KR102693720B1 - Methods and apparatus for transmit iq mismatch calibration - Google Patents

Abstract

A method for pre-compensating transmitter in-phase (I) and quadrature (Q) mismatch (IQMM) includes transmitting a signal through an upconverter of a transmit path to provide an upconverted signal, determining the upconverted signal through a downconverter of a receive feedback path, determining one or more IQMM parameters for the transmit path based on the determined upconverted signal, and determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path. In some embodiments, the upconverted signal can be determined through the receive feedback path. In some embodiments, the upconverted signal can be determined through an envelope detector.

Description

{METHODS AND APPARATUS FOR TRANSMIT IQ MISMATCH CALIBRATION}

The present disclosure relates generally to orthogonal transmitters, and more particularly to transmit IQ mismatch correction.

An orthogonal transmitter may include an in-phase (I) path and a quadrature-phase (Q) path. An imbalance between the I and Q paths, also known as IQ mismatch (IQMM), can degrade the performance of the transmitter.

The above information disclosed in this Background section is intended solely to increase understanding of the background of the present invention and may therefore contain information that does not constitute prior art.

A method for pre-compensating transmitter in-phase (I) and quadrature phase (Q) mismatch (IQMM) is provided.

A system is provided to pre-compensate for transmitter in-phase (I) and quadrature phase (Q) mismatch (IQMM).

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

A method for pre-compensating transmitter in-phase (I) and quadrature (Q) mismatch (IQMM) can include the steps of: transmitting a signal through an upconverter of a transmit path to provide an upconverted signal; determining the upconverted signal through a downconverter of a receive feedback path; determining one or more IQMM parameters for the transmit path based on the determined upconverted signal; and determining one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path. The step of determining the one or more IQMM parameters for the transmit path can include the step of solving a system of equations, a first of the equations including a first parameter at least partially representative of a first component of the upconverted signal and a desired frequency response of the transmit path, and a second of the equations including a second parameter at least partially representative of a second component of the upconverted signal and a frequency response of the transmit path due to the transmit IQMM. The first equation of the above equations may further include a third parameter at least partially representing a gain and a delay for the transmit path. The method may further include determining an IQMM for the receive feedback path using a first local oscillator for the transmit path and a second local oscillator for the receive path, and the step of determining one or more IQMM parameters for the transmit path based on the determined up-converted signal may include processing the up-converted signal to compensate for the IQMM in the receive path. The local oscillator for the transmit path may have a frequency shift from the local oscillator for the receive feedback path. The signal may include a first signal at a first frequency, and the up-converted signal may include the first up-converted signal, and the method may include: transmitting a second signal at a second frequency via the up-converter of the transmit path to provide a second up-converted signal; determining the second up-converted signal via the down-converter of the receive feedback path; and may further include a step of determining one or more IQMM parameters for the transmission path based on the determined second up-converted signal.

A method for pre-compensating transmitter in-phase (I) and quadrature (Q) mismatch (IQMM) may include: transmitting a signal through an upconverter of a transmission path to provide an upconverted signal; determining the upconverted signal through an envelope detector; determining one or more IQMM parameters for the transmission path based on the determined upconverted signal; and determining one or more pre-compensation parameters for the transmission path based on the one or more IQMM parameters for the transmission path. The step of determining the one or more IQMM parameters for the transmission path may include: applying a first pre-compensation parameter to the transmission path; determining a first power of a component of the upconverted signal caused by the transmission IQMM through the envelope detector based on the first pre-compensation parameter; applying a second pre-compensation parameter to the transmission path; and determining a second power of a component of the upconverted signal caused by the transmission IQMM through the envelope detector based on the second pre-compensation parameter. The step of determining one or more IQMM parameters for the transmission path may further comprise selecting one of the first pre-compensation parameter or the second pre-compensation parameter based on the lower of the first power and the second power. The method may further comprise applying one or more additional pre-compensation parameters to the transmission path; and determining one or more additional powers of one or more components of the up-converted signal caused by the transmit IQMM via the envelope detector based on the one or more additional pre-compensation parameters, wherein the step of determining one or more IQMM parameters for the transmission path may comprise selecting one of the first pre-compensation parameter, the second pre-compensation parameter, or the one or more additional pre-compensation parameters based on the lower of the first power, the second power, or the one or more additional powers. The method may further comprise sweeping the frequency of a t-signal transmitted via the up-converter of the transmission path to provide an additional up-converted signal; determining the additional up-converted signal via the envelope detector; And the method may further include determining one or more IQMM parameters for the transmission path based on the additionally determined up-converted signal. The signal comprises a first signal at a first frequency, the up-converted signal comprises the first up-converted signal, and the method further includes transmitting a second signal at a second frequency via the up-converter of the transmission path to provide a second up-converted signal; determining the second up-converted signal via the envelope detector; and determining one or more IQMM parameters for the transmission path based on the determined second up-converted signal. The method may further include applying first and second pre-compensation parameters to the transmission path for each of the first and second signals, wherein the first and second up-converted signals can be individually determined based on the first and second pre-compensation parameters. The step of determining one or more IQMM parameters for the transmission path may comprise solving simultaneous equations based on the determined first and second up-converted signals, a first of the equations comprising at least a partial function of the first and second pre-compensation parameters. The second frequency may be a negative of the first frequency at baseband. The method may further comprise sweeping the first and second frequencies for each of the first and second pre-compensation parameters; determining additional first and second up-converted signals based on sweeping the first and second frequencies; and determining one or more IQMM parameters for the transmission path over frequency based on the determined additional up-converted signals. In the eighth paragraph, the signal comprises a first 2-tone signal, and the up-converted signal may comprise a first up-converted 2-tone signal, and the method may further comprise the steps of: transmitting a second 2-tone signal through the up-converter of the transmission path to provide a second up-converted 2-tone signal; determining the second up-converted 2-tone signal through the envelope detector; and determining one or more IQMM parameters for the transmission path based on the determined second up-converted 2-tone signal. The step of determining one or more IQMM parameters for the transmission path may comprise the step of solving simultaneous equations based on the determined first and second up-converted 2-tone signals, at least one of the equations comprising a first parameter of a first frequency of the first 2-tone signal and a second parameter of a second frequency of the first 2-tone signal. The method may further comprise the steps of sweeping at least one of the first and second frequencies of the two-tone signal; determining additional first and second up-converted two-tone signals based on sweeping the first and second frequencies; and determining one or more IQMM parameters for the transmission path over the frequency based on the determined additional up-converted two-tone signals.

The system may include an IQ transmit path including an upconverter; an envelope detector arranged to provide an envelope of an upconverted signal from the IQ transmit path; a signal generator configured to apply a pilot signal to the IQ transmit path; a signal observer arranged to capture the envelope of the upconverted signal based on the pilot signal; and a processor configured to estimate one or more IQ mismatch (IQMM) parameters for the IQ transmit path based on the captured envelope of the upconverted signal, and to estimate one or more compensation factors for the IQ transmit path based on the estimated IQMM parameters. The signal observer may be arranged to capture the envelope of the upconverted signal via a branch of an IQ receiver.

The system comprises an IQ transmit path including an upconverter, an IQ receive path including a downconverter, a feedback connection arranged to couple an upconverted signal from the IQ transmit path to the IQ receive path, a signal generator configured to apply a pilot signal to the IQ transmit path, a signal observer configured to capture the upconverted signal via the IQ receive path based on the pilot signal, and a processor configured to estimate one or more IQ mismatch (IQMM) parameters for the IQ transmit path based on the captured upconverted signal, and to estimate one or more compensation factors for the IQ transmit path based on the estimated IQMM parameters.

The drawings are not necessarily to scale, and elements of similar structure or function are generally represented throughout the drawings with like reference numerals for illustrative purposes. The drawings are provided solely to facilitate the description of various embodiments disclosed herein. They do not illustrate every aspect of the teachings disclosed herein, nor do they limit the scope of the claims. The drawings, which are incorporated in and accompanying the specification, illustrate exemplary embodiments of the present disclosure, and together with the description serve to explain the principles of the present disclosure.
FIG. 1 illustrates an exemplary embodiment of an IQ transmitter that may be used to implement any TX IQMM estimation and/or compensation technique according to the present disclosure.
FIG. 2 illustrates an exemplary embodiment of a complex-valued pre-compensator (CVC) structure in which coefficients can be estimated according to the present disclosure.
FIG. 3 illustrates an embodiment of a system that can be used to implement TX FD-IQMM calibration using an RX feedback path according to the present disclosure.
FIG. 4 illustrates an exemplary embodiment of a system that can be used to implement TX FD-IQMM calibration using an RX feedback path according to the present disclosure.
FIG. 5 illustrates an exemplary embodiment of a spectrum plot of transmitted and captured (observed) signals corresponding to some equations according to the present disclosure.
FIG. 6 illustrates an embodiment of a system that can be used to implement TX FD-IQMM calibration using an envelope detector according to the present disclosure.
FIG. 7 illustrates an exemplary embodiment of a system that can be used to implement TX FD-IQMM calibration using an envelope detector according to the present disclosure.
FIG. 8 illustrates some spectrum plots of transmitted and captured (observed) signals using a first embodiment of a method for TX IQMM calibration using an envelope detector according to the present disclosure.
FIG. 9 illustrates some spectrum plots of transmitted and captured (observed) signals using a third embodiment of a method for TX IQMM calibration using an envelope detector according to the present disclosure.
FIG. 10 illustrates an embodiment of a method for TX IQMM calibration using an RX feedback path according to the present disclosure.
FIG. 11 illustrates an embodiment of a first method for TX IQMM calibration using an envelope detector according to the present disclosure.
FIG. 12 illustrates an embodiment of a second method for TX IQMM calibration using an envelope detector according to the present disclosure.
FIG. 13 illustrates an embodiment of a third method for TX IQMM calibration using an envelope detector according to the present disclosure.
FIG. 14 illustrates an embodiment of a pre-compensation method for a transmitter IQMM according to the present disclosure.
FIG. 15 illustrates another embodiment of a pre-compensation method for a transmitter IQMM according to the present disclosure.

outline

The present disclosure encompasses a number of inventive principles relating to pre-compensation of in-phase (I) and quadrature-phase (Q) mismatch (IQMM) in a quadrature up-conversion transmitter. A pilot signal can be applied to a transmit (TX) path at baseband and the IQMM impaired up-converted signal can be captured and processed using various techniques and algorithms disclosed to estimate the TX IQMM, which can include both frequency-independent IQMM (FI-IQMM) and frequency-dependent IQMM (FD-IQMM). The estimated IQMM can be used to determine coefficients for a pre-compensator in the TX path.

In some embodiments, the IQMM corrupted up-converted signal can be captured via a receive (RX) feedback path having a quadrature down-converter. A single tone pilot signal can be applied at different frequencies, and the first and mirror components of the captured down-converted signal can be used in a simultaneous equations to estimate the IQMM parameters for the TX path. The effect of the RX IQMM in the RX feedback path can be reduced or eliminated via various techniques disclosed, for example, by using separate local oscillators for the TX and RX paths, or by using a frequency shift between the local oscillators for the TX and RX paths.

In some embodiments, the IQMM corrupted up-converted signal can be captured via an envelope detector and processed using various techniques disclosed herein. In a first method using an envelope detector, a single tone pilot signal can be applied while varying one or more of the pre-compensation parameters. The single tone pilot signal applied at baseband can generate a signal at the output of the envelope detector having components corresponding to twice the frequency of the pilot signal when there is an IQMM in the TX path. Accordingly, the first method can sweep the one or more of the pre-compensation parameters while applying the first single tone pilot signal and selecting one or more of the parameters that provide the lowest output power from the envelope detector at twice the frequency of the pilot signal. The search can be performed by repeating this process at other frequencies to select one or more parameters for each frequency. The selected parameters can be used to estimate the IQMM parameters for the TX path.

In a second method using an envelope detector, one or more TX IQMM parameters for any frequency can be directly estimated by transmitting a single tone pilot signal at baseband for the negative and positive frequencies separately using two different sets of precompensator settings. The components corresponding to twice the arbitrary frequency at the output of the envelope detector are combined in a set of equations to solve for the frequency dependent gain and phase mismatch at that arbitrary frequency. This process can be repeated to determine the frequency dependent gain and phase mismatch at other frequencies, which can then be used to estimate the IQMM parameters for the TX path.

In a third method using an envelope detector, different combinations of negative and positive frequencies of a two-tone pilot signal can be applied individually to the TX path at baseband. The outputs of the envelope detector at different frequencies can be combined and solved using a set of equations to obtain direct estimates of the TX IQMM parameters.

Once the TX IQMM parameters are determined by any of these disclosed techniques, they can be used to determine coefficients for the pre-compensator in the TX path.

The principles disclosed herein may have independent utility and may be implemented individually, and not all embodiments may utilize all principles. Furthermore, the principles may also be implemented in various combinations, some of which may amplify the benefits of the individual principles in a synergistic manner.

TX Pre-compensation

In a quadrature upconverter transmitter, IQMM between the I and Q branches can create interference between the mirror frequencies after upconversion to radio frequency (RF) or intermediate frequency (IF). Therefore, IQMM can degrade system performance by reducing the effective signal-to-coherence-noise ratio (SINR). Frequency-independent IQMM (FI-IQMM) can result from an imbalance in the mixer, while frequency-dependent IQMM (FD-IQMM) can result from a mismatch between the overall frequency responses of the I and Q paths. In some embodiments, only the frequency-independent IQMM (FI-IQMM) can be compensated for. However, in some applications, such as wideband systems (e.g., mmWave systems), FI-IQMM compensation alone may not provide adequate performance. Therefore, some of the inventive principles of the present application relate to techniques for providing FD-IQMM compensation for a quadrature upconverter transmitter. Additionally, the TX IQMM may be different from the RX IQMM. Therefore, in some embodiments, the correction method for the TX path according to the present disclosure may be different from that for the RX path.

FIG. 1 illustrates an exemplary embodiment of an IQ transmitter that may be used to implement any of the TX IQMM estimation and/or compensation techniques according to the present disclosure. The transmitter (100) illustrated in FIG. 1 may include an I signal path including a digital-to-analog converter (DAC) (104), a low pass filter (108) having an impulse response h _ITX (t), and a mixer (112). The transmitter (100), which may also be referred to as a TX path, may also include a Q signal path including a DAC (106), a low pass filter (110) having an impulse response h _QTX (t), and a mixer (114). The mixers (112, 114) and filters (108, 110) may collectively form an upconverter along with a summation circuit (116). The transmitter (100) may further include an IQMM precompensator (118).

In the transmitter, g _TX ≠ 1 and φ _TX ≠ 0 can represent the TX gain and phase mismatch, respectively, which can generate frequency-independent IQ mismatch (FI-IQMM) in the transmitter. The mismatch between the overall frequency responses h _ITX (t) and h _QTX (t) in the I and Q paths of the TX path can generate FD-IQMM in the TX path, i.e., h _ITX (t) ≠ h _QTX (t).

The baseband corresponding to the up-converted signal of the TX path (100) in the frequency domain (at the output of the mixer) can be given as follows:

Here, U(f) can be the frequency response of the desired baseband (BB) signal at the input of the analog baseband (ABB) filter (108 and 110) in the TX path, and G _1TX (f) and G _2TX (f) can be defined as follows:

In Equation 2, H _ITX (f) and H _QTX (f) may represent the frequency responses of the filter (108) (h _ITX (t)) and the filter (110) (h _QTX (t)), respectively. In Equation 1, G _1TX (f)U(f) may represent a desired TX signal, and G _2TX (f)U*(-f) may represent a TX image signal. In the absence of IQMM (g _TX = 1, φ _TX = 0, and h _ITX (t) = h _QTX (t)), G _2TX (f) and consequently the second term of Equation 1 may become 0. Therefore, in some embodiments, G _1TX (f) may represent the desired frequency response of the transmit path, and G _2TX (f) may represent the frequency response of the transmit path due to the IQMM.

In some embodiments according to the present disclosure, the effect of IQMM in the transmitter (100) can be compensated for by estimating one or more IQMM parameters in the transmitter and then determining pre-compensation parameters using the estimated IQMM parameters.

The one or more IQMM parameters may include a gain mismatch g _TX , a phase mismatch φ _TX , filters h _ITX (t) and h _QTX (t) (and/or their frequency responses H _ITX (f) and H _QTX (f)), G _1TX (f), G _2TX (f), V _TX (f) (described below), etc. In some example embodiments described below, the parameters φ _TX and V _TX (f) may be used as IQMM parameters, for example, because this may reduce complexity and/or effort associated with mathematical derivation. However, other IQMM parameters may be used according to the present disclosure. For example, in some example embodiments, G _1TX (f) and G _2TX (f) may be used as IQMM parameters that can be used to determine the pre-compensation parameters after they are estimated.

The pre-compensation parameter can be any parameter that can determine how the IQMM pre-compensator (118) can affect the IQMM in the TX path (100). An example of the pre-compensation parameter can be a coefficient (IQMC coefficient) for the IQMM pre-compensator (118) that can form the BB signal s[n] = s _I [n] + js _Q [n] to reduce or remove the image component in the up-converted signal _{z TX} (t). Examples of IQMC coefficients that can be obtained based on the estimated IQMM parameters are described below.

In some embodiments, the above-described IQMM parameter V _TX (f), which may vary depending on the TX gain and filter mismatch, may be defined as:

The various correction algorithms described herein can be used to estimate the phase mismatch φ _TX and V _TX (f) for continuous time frequencies f = ±f ₁ ,…, ±f _K over a desired frequency band. The estimates of φ _TX and V _TX (f) can be used to obtain IQ Mismatch Compensator (IQMC) coefficients for the pre-compensator (118) to reduce the TX FD-IQMM.

FIG. 2 illustrates an exemplary embodiment of a complex-valued pre-compensator (CVC) structure in which coefficients can be estimated according to the present disclosure. The embodiment illustrated in FIG. 2 may include an integer delay element (200) having a delay T _D , a complex conjugate block (202), a complex-valued filter (204) having an impulse response w _TX [n], and a summation circuit (206).

The values for the coefficients for the pre-compensator shown in FIG. 2, which can completely or partially remove the TX FD-IQMM from the transmitter (100) shown in FIG. 1, can be given as follows:

Here can represent the frequency response of the filter w _TX [n]. From equation (4), it can be evident that the optimal response of the IQMC coefficients may include knowledge of φ _TX and/or V _TX (f), which can be estimated using, for example, any of the techniques disclosed herein.

In some embodiments, and depending on implementation details, the methods, expressions, etc. disclosed herein may provide an optimal value, and thus the designator "opt" may be used. However, the principles of the present invention are not limited to embodiments in which an optimal value can be obtained, and the use of "opt" or "optimal" is not limited to methods, expressions, etc. that can provide an optimal value.

Some exemplary embodiments of the CVC architecture illustrated in FIG. 2 may include any of the following implementation details. The complex-valued filter (204) having an impulse response w _TX [n] may be implemented as, for example, a finite impulse response (FIR) filter. The complex conjugate block (202) may be configured to output the complex conjugate of the signal s[n], for example, as s[n] ^* = s _I [n] - js _Q [n]. The integer delay element (200) having a delay T _D may be configured to generate a delay in the input signal, for example, as s[nT _D ].

Although the CVC architecture illustrated in FIG. 2 is provided as an example to illustrate the inventive principles of the present disclosure, other IQMM pre-compensation architectures and/or combinations thereof may be used. For example, in some embodiments, a real value compensator (RVC) architecture may be used.

RX feedback path

FIG. 3 illustrates an embodiment of a system that may be used to implement TX FD-IQMM calibration using an RX feedback path according to the present disclosure. The embodiment illustrated in FIG. 3 may include a TX path (300), an RX path (302), a feedback connection (304), and a signal processing unit (306). The TX path (300) may include a pre-compensator (308), a digital-to-analog converter (DAC) (310), an up-converter (314), and a radio frequency (RF) transmit block (316). The RX path (302) may include an RF receive block (318), a down-converter (320), and an analog-to-digital converter (ADC) (324). In some embodiments, the RX path (302) may further include a compensator (not shown). The signal processing unit (306) may include a signal generator (328), a signal capture unit (330), and a signal processor (332).

The feedback connection (304) may be implemented with any suitable device, such as a switch, coupler, conductor, transmission line, filter, etc. The feedback connection (304) may be connected to the TX path (300) at any location after the upconverter (314). The feedback connection (304) may be connected to the RX path (302) at any location before the downconverter (320). In some embodiments, part or all of the feedback connection (304) may be integrated with the TX path (300) and/or the RX path (302).

The TX path (300) and the RX path (302) may each include an I signal path or branch and a Q signal path or branch. The RF transmit block (316) may include various components for transmitting RF signals, such as a power amplifier, a bandpass filter, an antenna, and the like. The RF receive block (318) may include various components for receiving RF signals, such as an antenna, a bandpass filter, a low noise amplifier (LNA), and the like. Depending on whether the system is in operating mode or calibration mode, the IQMM of the TX path (300) may be corrected by the IQMM pre-compensator (308).

In some embodiments, the processor (332) may manage and/or control the overall operation of the system illustrated in FIG. 3. This may include controlling the application of one or more pilot signals to the TX path (300), capturing observations of the upconverted pilot signals via the RX path (302), performing computations and/or offloading the computations to another resource, providing estimated coefficients to the TX precompensator (308), controlling the TX precompensator (308) during transmission and/or transmission of the pilot signals, such as by disabling the precompensator (308), placing it in a transparent or pass-through state, etc.

Although the various components illustrated in FIG. 3 may be depicted as individual components, in some embodiments, a number of the components and/or their functionality may be combined into a fewer number of components. Likewise, single components and/or their functionality may be distributed and/or integrated among other components. For example, the signal generator (328) and/or the signal capture unit (330) may be integrated with and/or have their functionality performed by one or more similar components of a modem that may be coupled to the transceiver illustrated in FIG. 3.

Components of the signal processing unit (306) may be implemented in hardware, software, and/or any combination thereof. For example, a full or partial hardware implementation may include combinational logic, sequential logic, timers, counters, registers, gate arrays, amplifiers, synthesizers, multiplexers, modulators, demodulators, filters, vector processors, complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), state machines, data converters such as ADCs and DACs, and the like. A full or partial software implementation may include one or more processor cores, memory, program and/or data storage, and the like, which may be located locally and/or remotely, and which may be programmed to execute instructions for performing one or more functions of the components of the signal processing unit (306).

FIG. 4 illustrates an exemplary embodiment of a system that may be used to implement TX FD-IQMM calibration using an RX feedback path according to the present disclosure. The embodiment illustrated in FIG. 4 may include a TX path (400), an RX path (402), and an RX feedback connection (403). The TX path (400), which may be similar to the transmitter (100) illustrated in FIG. 1, may include an I signal path including a DAC (404), a low pass filter (408) having an impulse response h _ITX (t), and a mixer (412). The TX path (400) may also include a Q signal path including a DAC (406), a low pass filter (410) having an impulse response h _QTX (t), and a mixer (414). The mixer (412, 414) and filters (408, 410) may collectively form an upconverter together with a summing circuit (416). The TX path (400) may further include an IQMM precompensator (418).

The RX path (402) may include an I signal path including a mixer (426), a low pass filter (430) having an impulse response h _IRX (t), and an ADC (434). The RX path (402) may also include a Q signal path including a mixer (428), a low pass filter (432) having an impulse response h _QRX (t), and an ADC (436). The mixers (426, 428) and filters (430, 432) may collectively form a down converter. In some embodiments, the RX path (402) may further include an IQMM compensator (not shown) that may be disabled or placed in a pass state during the calibration operation.

In some embodiments, during the calibration operation, the IQMM pre-compensator (418) may be disabled or placed in a pass mode such that the IQMC becomes singular, thereby making U(f) = S(f).

To estimate the IQMM parameters φ _TX and V _TX (f), a single tone signal can be applied to the baseband of the TX path (400) at frequency f _K , i.e., U(f) = A _TX δ(f _K ), where A _TX may be an unknown scaling factor that can account for the gain and/or delay of the path between the TX baseband signal generation and the inputs of the ABB filters (408 and 410). The IQMM impaired upconverted signal can be observed by capturing the frequency response of the downconverted signal through the RX feedback path at the main and image frequencies (f _K and -f _K ), which is and can be represented as . Next, a single tone signal at frequency -f _K , i.e. can be transmitted through the TX path (400), and the down-converted signals at frequencies -f _K and f _K can be represented as R _3,k = R'(-f _K ) and R _4,k = R'(f _K ), respectively. Collecting all the observations can provide the following set of equations:

Here, A _RX may represent the gain and/or delay from the RX ABB filter (430 and 432) to the RX BB. In some embodiments, the four equations 5 may be time-aligned for accurate estimation of the IQMM parameters.

Figure 5 illustrates an exemplary embodiment of a spectrum plot of a transmitted and captured (observed) signal corresponding to Equation 5.

A single tone signal (e.g., f _K ) can be swept across the channel bandwidth for all selected frequencies to obtain estimates of φ _TX and V _TX (f) using Equation 5 as follows.

Here,

In some implementations of the above-described compensation algorithm, the IQMM in the RX feedback path may be assumed to be zero. In some other implementations, the RX feedback path may introduce the RX IQMM into the observation, which may degrade the estimation accuracy of the TX IQMM parameters.

In some embodiments, one or both of the two techniques described below can reduce or eliminate the impact of an IQMM in the RX feedback path on the observation of an up-converted pilot signal according to the present disclosure.

In a first technique according to the present disclosure, the RX FD-IQMC can be compensated using separate local oscillators (LOs) for the TX and RX paths in loopback mode (e.g., using a DC tone at the BB of the TX path while sweeping the TX LO and keeping the RX LO fixed). Next, the BB TX tone can be swept across frequency while keeping both the TX LO and the RX LO fixed to the same frequency. The TX FD-IQMC coefficients can be determined. In some embodiments, an additional step can be added to post-process the received signal R(f) to remove the influence of the RX-IQMM before the estimation of φ _TX and V _TX (f).

In a second technique according to the present disclosure, a frequency shift can be generated between the LOs of the TX path and the RX path so that the RX-IQMM does not interfere with the main signal and the mirror signal of the TX path. In some embodiments, the frequency shift between the LOs can be kept relatively small, for example, to preserve the approximate symmetry of the ABB filter response observable by the TX main signal and the image signal.

Envelope detector

FIG. 6 illustrates an embodiment of a system that may be used to implement TX FD-IQMM calibration using an envelope detector according to the present disclosure. The system illustrated in FIG. 6 may include a signal processing unit (606) and a TX path (600), which may be configured and/or operated in a similar manner as illustrated in FIG. 3. Specifically, the TX path (600) may include a pre-compensator (608), a digital-to-analog converter (DAC) (610), an up-converter (614), and a radio frequency (RF) transmit block (616). The signal processing unit (606) may include a signal generator (628), a signal capture unit (630), and a signal processor (632).

The system illustrated in FIG. 6 may further include an envelope detector (640) and a signal return path (642). The envelope detector (640), which may be implemented using any suitable devices including diodes, filters, and the like, may be coupled to the TX path (600) at any location after the upconverter (614). The return signal path (642) may include any suitable devices such as switches, couplers, conductors, transmission lines, filters, data converters, and the like.

In some embodiments, the envelope detector (640) may provide an output having the form, for example, y(t) = |z(t)| ^2. In some embodiments, part or all of the envelope detector (640) may be integrated with the TX path (600).

In some embodiments, the envelope detector (640) may output the envelope of the IQMM corrupted up-converted signal and feed it back to the signal processing unit (606) without passing through the mixer. Thus, the captured signal may contain only the TX IQMM without the RX corruption. The return signal path (642) is not limited to any particular implementation details, but in some embodiments, the dLT downstream of the multiplier in the orthogonal receiver may be used as the return signal path, either the I or Q signal path. This may be convenient, for example, in a transceiver system where an RX path already exists.

FIG. 7 illustrates an exemplary embodiment of a system that may be used to implement TX FD-IQMM calibration using an envelope detector according to the present disclosure. The system illustrated in FIG. 7 may include a TX path (700), an RX path (702), and an envelope detector (740).

The TX path (700), which may be similar to the TX path (400) illustrated in FIG. 4, may include an I signal path including a DAC (704), a low pass filter (708) having an impulse response h _ITX (t), and a mixer (712). The TX path (700) may also include a Q signal path including a DAC (706), a low pass filter (710) having an impulse response h _QTX (t), and a mixer (714). The mixers (712, 714) and the filters (708, 710) may collectively form an upconverter along with a summing circuit (716). The TX path (700) may further include an IQMM precompensator (718).

The RX path (702), which may be similar to the RX path (402) illustrated in FIG. 4, may include an I signal path including a mixer (726), a low pass filter (730) having an impulse response h _IRX (t), and an ADC (734). The RX path (702) may also include a Q signal path including a mixer (728), a low pass filter (732) having an impulse response h _QRX (t), and an ADC (736). The mixers (726, 728) and filters (730, 732) may collectively form a down converter. In some embodiments, the RX path (702) may further include an IQMM compensator that may be disabled or placed in a pass state during the calibration operation.

The envelope detector (740) can be connected to the TX path (700) at any location after the upconversion unit. It can also be connected to the RX path (702) at any location after the mixers (726 and 728). In the embodiment illustrated in FIG. 7, the envelope detector (740) is connected to the I path of the RX path, but it can also be connected to the Q side.

Embodiments of three different methods for estimating the TX IQMM using an envelope detector are described below in the context of the exemplary embodiment illustrated in Fig. 7. However, these methods are not limited to these or any other system implementation details.

Method 1

In some embodiments, the method is to obtain single-tap pre-compensator filter coefficients capable of removing IQMM at frequencies ±f ₁ ,…, ±f _K . These coefficients can be used to estimate the IQMM parameters φ _TX and V _TX (f).

Referring to FIG. 8, in some embodiments, a single tone signal transmitted at baseband with frequency f _K can produce an output from an envelope detector having a component of frequency 2f _K when there is an IQMM in the TX chain. Therefore, the single-tap pre-compensator coefficients (in some implementations the optimal or optimum coefficients) for frequency f _K can be obtained by transmitting a single tone signal from baseband of the TX at frequency -f _K , sweeping the pre-compensator coefficients (in some implementations a single tap may be adequate), and selecting the coefficients that can provide the lowest power at the output of the envelope detector at twice the frequency of the BB signal, i.e. 2f _K . For a single tone signal transmitted at frequency -f _K , the output of the envelope detector path can be denoted by r(t), and its response (ignoring high frequency components) can be given by:

The frequency response of the envelope detector output at frequency 2f _K can be given as:

In the absence of IQMM, G _2TX (f _K ) can be 0, so R(2f _K ) in Equation 9 can be 0. By performing a pre-compensator coefficient search, a one-tap pre-compensator setting, i.e., w _TX [n] = w _TX,0 × δ[n], can be obtained so that R(2f _K ) becomes 0 and the IQMM can be removed at frequency f _K . By sweeping f _K and for T _D = 0, After obtaining the IQMC coefficients (i.e., optimal coefficients) for all frequency tones denoted by , φ _TX and V _TX (f) can be estimated for the CVC structure as follows:

In some embodiments, the search for the pre-compensator coefficients may be implemented as a broad or exhaustive search. For example, the search may be performed over a wide range of pre-compensator settings and/or frequency tones at fixed intervals. In some embodiments, the search may be performed in stages. For example, an initial search may be performed over a relatively coarse grid of pre-compensator settings and/or frequency tones at a wider interval. Then, one or more additional searches may be performed over a finer grid at a smaller interval at one or more smaller intervals based on the results of the coarse search.

Method 2

In some embodiments, the method can directly estimate the IQMM parameters for an arbitrary frequency f _K , for example, by transmitting single tone signals separately at f _K and -f _K using two different pre-compensator coefficients and/or settings. The envelope detector output at frequency 2f _K for such measurements can then be combined and solved, for example, using a closed-form second-order equation, to obtain the frequency-dependent gain and phase mismatch at f _K . Then the IQMM parameters φ _TX and V _TX (f) can be obtained as, for example, simple functions of the frequency-dependent gain and phase mismatch for each frequency f _K .

Some examples of implementation details are as follows. Single tone signals at frequencies f _K and -f _K can be applied individually without any IQMC in the case of the CVC architecture illustrated in Fig. 2 in BB (e.g., w _TX [n] = 0), and the frequency responses of the envelope detector output at frequency 2f _K can be denoted by Y _1,k and Y _{2,k ,} respectively. Another pre-compensation parameter w[n] with delay element T _D = 0 can be selected and applied, and the single tone signal at frequency f _k can be transmitted. The frequency response of the envelope detector output at frequency 2f _k can be denoted by Y _3,k . This results in the following equation.

Here, J ₁ and J ₂ can be known values which can be defined as follows.

Equation (11) can be reformulated using the relation V _TX (f _K ) = V ^* _TX (-f _k ) and equations (2) and (3) as follows.

Here, am.

Equation (13) can provide six real equations with five real unknowns, namely Re{γ}, Im{γ}, Re{V _TX (f _K )}, Im{V _TX (f _K )}, φ _TX , which can be solved to obtain estimates of V _TX (f _K ) and φ _TX . The IQMM parameter V _TX (-f _K ) is , which can be estimated from h _ITX (t) and h _QTX (t), which are real-valued filters that can be conjugate-symmetric in the frequency domain, i.e., and am.

Method 3

In some embodiments, the method comprises frequency and and may include transmitting a separate 2-tone pilot signal at the frequency The envelope detector output for these measurements is, for example, Using two second-order equations to obtain estimates of φ _TX and V _TX (f) directly, they can be combined in closed form to obtain a solution.

Referring to FIG. 9, in some embodiments of this method, the frequency In , a 2-tone signal is generated and transmitted at the TX baseband, i.e. , and the time domain signal can be captured from the output of the envelope detector. The frequency response of the time domain signal is , , , can be represented as . Next, the multi-tone signal is expressed as a frequency and is transmitted from, i.e. , and frequency The frequency response of the envelope detector output is and can be represented as . Then, the multi-tone signal is expressed as a frequency and is transmitted from, i.e. and frequency The captured frequency response of the envelope signal in and can be expressed as . The following parameters can be defined:

Combining all the observations can give the following set of nonlinear equations:

The set of eight equations with eight unknowns in Equation 15 can be solved, for example, using the following steps.

1.

a. For l = 1,2 and i = 1,2 we can compute the following parameters:

b. , , , and can be calculated as follows:

, ,

Here, and

c. , , and can be calculated as follows:

d. and can be calculated as follows:

, , ,

2. All , , and After obtaining this, at this time

a. φ _TX can be estimated as follows:

b. The estimate of V _TX (f) can be obtained as follows:

, For r=1,2,

In some embodiments, f _K1 > 0 and f _K2 > 0 are the frequencies , , , and This can be chosen to be distinct.

The selection of the 2-tone pilot signal (and its positive and negative frequencies) as well as the resulting envelope detector output signals selected for analysis are for illustration purposes only and other combinations of pilot signals and/or output signals may be used. For example, in the second set of signals in Fig. 9, and Instead and may be used. Some of the unused signals are indicated by dashed lines in FIG. 9, but in other embodiments, these signals may be used while other signals may not be used. Some embodiments may be described in the context of a 2-tone pilot signal, but pilot signals having any number of tones, such as 3-tone, 4-tone, etc., may be used.

As described above, in some embodiments, one or more of the equations that may be obtained using Method 3 may include one or more IQMM parameters of two frequencies of the two-tone signal. In contrast, in some embodiments using Method 2, each equation may include only the IQMM of a single frequency. Thus, in some embodiments, and depending on implementation details, different sets of equations may be obtained using different methods.

Obtaining IQMC coefficients

In some embodiments, after obtaining estimates of φ _TX and V _TX (f) for f = ±f ₁ ,…, ±f _K , these estimates can be used to compensate the FD-IQMM in the TX path. In some exemplary embodiments, a least squares (LS) method can be implemented as follows: For any delay element T _D , the parameters given in Equation 4 can be estimated at frequencies f = ±f ₁ ,…, ±f _K . For example, a finite impulse response (FIR) filter with length L In an embodiment having, the method is to obtain W _TX (f) at frequencies f = ±f ₁ ,…, ±f _K The optimal L-tap filter that minimizes the least squares (LS) between You can obtain:

Here, And is a discrete Fourier transform (DFT) matrix of size 2K x L. In some embodiments, T _D can take values of {0, ..., L-1}. For a fixed T _D , w _TX is with least squares error can be obtained. The optimal TD and filter coefficients are then is obtained as follows:

Although some of the techniques have been described in the context of a pre-compensator structure such as that illustrated in FIG. 2, the principles of the present invention are not limited to these examples, and the correction algorithm according to the present disclosure can be applied to other IQMC structures as well. It is also possible to obtain filter coefficients for an IQMC structure based on the estimated IQMM parameters using techniques other than LS, and the methodology described herein is merely an example to illustrate the principles of the present invention.

In any of the embodiments disclosed herein, the frequency domain signals (e.g., signals R _1,k , …, R _4,k of FIG. 10 ) can be obtained by capturing a baseband time domain signal and transforming it into a frequency domain signal using a fast Fourier transform (RET).

FIG. 10 illustrates an embodiment of a TX IQMM calibration method using an RX feedback path according to the present disclosure. The method illustrated in FIG. 10 may be used, for example, with the system illustrated in FIG. 4. The method illustrated in FIG. 10 may begin at step 1000. At step 1002, a counter k may be initialized to 1. At step 1004, the method may check the value of the counter k. If k is less than or equal to a maximum value K, the method may proceed to step 1006, where a single tone pilot signal may be generated at frequency f _K and applied to the TX path (400) at baseband. At step 1008, a received pilot signal may be captured at frequencies f _K and -f _K at baseband of the RX path (402), which may be denoted as R _1,k and R _{2,k ,} respectively. At step 1010, a single tone pilot signal may be generated at frequency -f _K and applied to the TX path (400) at baseband. At step 1012, a received pilot signal may be captured at frequency -f _K and f _K at baseband of the RX path (402) and may be denoted as R _{3, k} and R _{4, k} , respectively.

At step 1014, the method may increment the value of the counter k and return to step 1004, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to task 1016, where the method may estimate the IQMM parameters φ _TX and V _TX (f), f = ±f ₁ ,… , ±f _K using the observations for R _1,k ,… , R _4,k , ∀k . At step 1018, the method may estimate the coefficients for the TX IQMM pre-compensator (418) using φ _TX and V _TX (f), f = ±f ₁ ,… , ±f _K . The method may then terminate at step 1020.

As mentioned above, in some embodiments, R _1,k ,…, R _{4,k can be obtained} by capturing the time domain signal at the BB of the RX path (402) and converting it to a frequency domain signal using, for example, FFT.

FIG. 11 illustrates an embodiment of a first method for TX IQMM calibration using an envelope detector according to the present disclosure. For example, the method illustrated in FIG. 11 may be used with the system illustrated in FIG. 7. The method illustrated in FIG. 11 may begin at step 1100. At step 1102, a counter k may be initialized to 1. At step 1104, the method may check the value of the counter k. If k is less than or equal to a maximum value K, the method may proceed to step 1106 where a new pre-compensator setting may be selected from the possible pre-compensator values. At step 1108, a single tone pilot signal may be generated at frequency -f _K and applied to the TX path (700) at baseband. At step 1110, the output signal of an ABB filter in the envelope detector path at frequency 2f _K may be captured. At step 1112, the method may check the power of the captured signal. If the power is a non-negligible value, the method can return to step 1106. If the power is zero or a negligible value, the method can proceed to step 1114 where an optimal value for the pre-compensator setting for frequency f _K can be set to the current setting. In step 1116, the procedure can be repeated for the single tone signal generated at f _k .

At step 1118, the method may increment the value of the counter k and return to step 1104, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to step 1120, where using the pre-compensator settings for ±f ₁ ,… , ±f _K , the method may estimate the IQMM parameters φ _TX and V _TX (f), f = ±f ₁ ,… , ±f _K . At step 1122, the method may estimate the coefficients for the TX IQMM pre-compensator (718) using φ _TX and V _TX (f), f = ±f ₁ ,… , ±f _K . The method may then end at step 1124.

FIG. 12 illustrates an embodiment of a second method for TX IQMM calibration using an envelope detector according to the present disclosure. The method illustrated in FIG. 12 may be used, for example, with the system illustrated in FIG. 7. The method illustrated in FIG. 12 may begin at step 1200. At step 1202, a counter k may be initialized to 1. At step 1204, the method may check the value of the counter k. If k is less than or equal to a maximum value K, the method may proceed to step 1206, where, for example, a first pre-compensator setting without IQMC may be selected. At step 1208, the method may generate and transmit a single tone signal at frequency f _K in the BB of the transmit path (700). A signal at the output of the ABB filters (730 and 732) in the envelope detector path may be captured at frequency 2f _K and denoted as Y _1,k . In some embodiments, the signal can be captured after the ADCs (734 and 736). At step 1210, the method can generate and transmit a single tone signal at frequency -f _K at the BB of the transmit path (700). The signal at the output of the ABB filters (730 and 732) in the envelope detector path can be captured at frequency 2f _K and denoted as Y _2,k . At step 1212, the method can select a second pre-compensator setting to apply to the TX path (700). At step 1214, the method can generate and transmit a single tone signal at frequency f _K at the BB of the transmit path (700). The signal at the output of the ABB filters (730 and 732) in the envelope detector path can be captured at frequency 2f _K and denoted as Y _3,k .

At step 1216, the method may increment the value of the counter k and return to step 1204, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to step 1218, where for every k, using Y _1,k , Y _2,k and Y _3,k , the method may estimate the IQMM parameters φ _TX and V _TX (f), f = ±f ₁ ,… ±f _K . At step 1220, the method may estimate coefficients for the TX IQMM pre-compensator (718) using φ _TX and V _TX (f), f = ±f ₁ ,… , ±f _K . Then, the method may end at step 1222.

FIG. 13 illustrates an embodiment of a third method for TX IQMM calibration using an envelope detector according to the present disclosure. The method illustrated in FIG. 13 may be used with, for example, the system illustrated in FIG. 7. The method illustrated in FIG. 13 may begin at step 1300. At step 1302, a counter k may be initialized to 1. At step 1304, the method may check the value of the counter k. If k is less than or equal to a maximum value K, the method may proceed to step 1306, where a two-tone signal is detected at the baseband of the TX path (700) at a frequency can be generated and transmitted at step 1308. At the output of the ABB filter (730 and 732) in the envelope detector path, the signal is frequency , , , and are represented as Y _1,k , Y _2,k , Y _3,k , and Y _{4,k ,} respectively. At step 1310, a 2-tone signal is captured at the baseband of the TX path (700) at a frequency can be generated and transmitted at step 1312. At the output of the ABB filter (730 and 732) in the envelope detector path, the signal is frequency , Captured in , respectively , may be represented as . At step 1314, a 2-tone signal is transmitted at the baseband of the TX path (700) at a frequency , can be generated and transmitted in step 1316. At step 1316, the signal of the output of the ABB filter (730 and 732) of the envelope detector path is frequency , Captured in each , can be displayed as

At step 1318, the method may increment the value of the counter k and return to step 1304, where the method may check the value of the counter k. If k is greater than the maximum value K, the method may proceed to step 1320, where, using Y _1,k ,…, Y _8,k for each k, the method may estimate the IQMM parameters φ _TX and V _TX (f), f = ±f ₁ ,…, ±f _K . At step 1322, the method may estimate coefficients for the TX IQMM pre-compensator (718) using φ _TX and V _TX (f), f = ±f ₁ ,…, ±f _K . The method may then terminate at step 1324.

FIG. 14 illustrates an embodiment of a pre-compensation method for a transmitter IQMM according to the present disclosure. The method may begin at step 1400. At step 1402, the method may transmit a signal via an upconverter of a transmit path to provide an upconverted signal. At step 1404, the method may determine the upconverted signal via a downconverter of a receive feedback path. At step 1406, the method may determine one or more IQMM parameters for the transmit path based on the determined upconverted signal, and at step 1408, the method may determine one or more pre-compensation parameters for the transmit path based on the one or more IQMM parameters for the transmit path. The method may end at step 1410.

FIG. 15 illustrates another embodiment of a pre-compensation method for a transmitter IQMM according to the present disclosure. The method may begin at operation 1500. At step 1502, the method may transmit a signal through an upconverter of a transmission path to provide an upconverted signal. At step 1504, the method may determine the upconverted signal via an envelope detector. At step 1506, the method may determine one or more IQMM parameters for the transmission path based on the determined upconverted signal. At step 1508, the method may determine one or more pre-compensation parameters for the transmission path based on the one or more IQMM parameters for the transmission path. The method may end at step 1510.

The operations and/or components described for the embodiments illustrated in FIGS. 14 and 15, as well as any other embodiments described herein, are exemplary. In some embodiments, some operations and/or components may be omitted and/or other operations and/or components may be included. Furthermore, in some embodiments, the temporal and/or spatial order of the operations and/or components may be changed.

The present disclosure encompasses a number of inventive principles relating to association and authentication for multi-point coordination. These principles may have independent utility and may be implemented individually, and not all embodiments may utilize all principles. Furthermore, the principles may also be implemented in various combinations, some of which may amplify the benefits of the individual principles in a synergistic manner.

While the embodiments disclosed above have been described in the context of various implementation details, the principles of the present disclosure are not limited to these or any other specific details. For example, while some functionality may be described as being implemented by a particular component, in other embodiments, the functionality may be distributed across different systems and components that are in different locations and have different user interfaces. While certain embodiments are described as having particular processes, steps, etc., these terms also encompass embodiments where the particular processes, steps, etc. may be implemented as multiple processes, steps, etc., or where multiple processes, steps, etc. may be integrated into a single process, step, etc. Reference to a component or element may refer to only a portion of the component or element.

The use of terms such as "first" and "second" in this disclosure and claims is solely for the purpose of distinguishing what they modify and may not imply spatial or temporal order unless the context otherwise makes clear. Reference to a first thing may not imply the existence of a second thing. While various organizational aids, such as section headings, may be provided for convenience, the subject matter arranged in accordance with such aids and the principles of this disclosure is not limited by such organizational aids.

The various details and embodiments described above may be combined to produce additional embodiments according to the principles of the present invention. Since the inventive principles of the present patent disclosure may be arranged and modified in detail without departing from the concept of the present invention, such changes and modifications are considered to fall within the scope of the following claims.

Claims (24)

In a method for pre-compensating transmitter in-phase (I) and quadrature phase (Q) mismatch (MM) (IQMM),
The above method,
A step of transmitting a first signal through a transmission path to provide a second signal;
A step of transmitting the second signal through an envelope detector;
determining one or more IQMM parameters for the transmission path based on the output of the envelope detector; and
Comprising a step of determining one or more pre-compensation parameters for the transmission path based on the one or more IQMM parameters for the transmission path,
The step of determining one or more IQMM parameters for the above transmission path comprises:
A step of applying a first pre-compensation parameter to the above transmission path;
A step of determining a first power of a component of the second signal caused by the transmitted IQMM through the envelope detector based on the first pre-compensation parameter;
A step of applying a second pre-compensation parameter to the above transmission path;
A step of determining a second power of a component of the second signal caused by the transmitted IQMM through the envelope detector based on the second pre-compensation parameter; and
A method comprising the step of selecting one of the first pre-compensation parameter or the second pre-compensation parameter based on the lower one of the first power and the second power. In the first paragraph,
The above method,
applying one or more additional pre-compensation parameters to said transmission path; and
further comprising the step of determining one or more additional powers of one or more components of the second signal caused by the transmitted IQMM via the envelope detector based on the one or more additional pre-compensation parameters;
The method of claim 1, wherein the step of determining one or more IQMM parameters for the transmission path comprises the step of selecting one of the first pre-compensation parameter, the second pre-compensation parameter or the one or more additional pre-compensation parameters based on the lower of the first power, the second power, or the one or more additional powers. In a method for pre-compensating transmitter in-phase (I) and quadrature phase (Q) mismatch (MM) (IQMM),
The above method,
A step of transmitting a first signal through a transmission path to provide a second signal;
A step of transmitting the second signal through an envelope detector;
determining one or more IQMM parameters for the transmission path based on the output of the envelope detector; and
Comprising a step of determining one or more pre-compensation parameters for the transmission path based on the one or more IQMM parameters for the transmission path,
The step of determining one or more IQMM parameters for the above transmission path comprises:
A step of applying a first pre-compensation parameter to the above transmission path;
A step of determining a first power of a component of the second signal caused by the transmitted IQMM through the envelope detector based on the first pre-compensation parameter;
a step of applying a second pre-compensation parameter to the above transmission path; and
A step of determining a second power of a component of the second signal caused by the transmitted IQMM through the envelope detector based on the second pre-compensation parameter,
The above method,
A step of sweeping the frequency of said first signal transmitted through said transmission path to provide one or more additional second signals;
transmitting one or more additional second signals through said envelope detector to provide one or more additional outputs of said envelope detector; and
A method further comprising the step of determining one or more IQMM parameters for the transmission path based on one or more additional outputs of the envelope detector. In a method for pre-compensating transmitter in-phase (I) and quadrature phase (Q) mismatch (MM) (IQMM),
The above method,
A step of transmitting a first input signal through a transmission path at a first frequency to provide a first output signal;
A step of transmitting a second input signal through a transmission path at a second frequency to provide a second output signal;
A step of transmitting the first output signal through an envelope detector to provide a first output of the envelope detector;
A step of transmitting the second output signal through the envelope detector to provide a second output of the envelope detector;
determining one or more IQMM parameters for the transmission path based on the first output of the envelope detector and the second output of the envelope detector; and
A method comprising the step of determining one or more pre-compensation parameters for the transmission path based on the one or more IQMM parameters for the transmission path. In the fourth paragraph,
A method further comprising the step of applying a first pre-compensation parameter and a second pre-compensation parameter to the transmission path for each of the first input signal and the second input signal. In clause 5,
The step of determining one or more IQMM parameters for the transmission path comprises the step of solving simultaneous equations based on the first output signal and the second output signal,
A method wherein the first equation among the above equations comprises at least in part a function of the first pre-compensation parameter and the second pre-compensation parameter. In clause 5,
A method wherein the second frequency is the negative of the first frequency at baseband. In clause 5,
A step of sweeping the first frequency and the second frequency for each of the first pre-compensation parameter and the second pre-compensation parameter;
A step of determining additional first output signals and second output signals based on sweeping the first frequency and the second frequency; and
A method further comprising the step of determining one or more IQMM parameters for the transmission path over a frequency based on the determined additional first output signal and second output signal. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete