CN111835290A - Power amplification system and related power amplification method suitable for Bluetooth device - Google Patents

Abstract

The power amplification system comprises a voltage-controlled oscillator, a frequency divider, a mixer and a summing amplifier. The voltage-controlled oscillator is used for providing input signals with the frequency being a non-integral multiple of a preset frequency; the frequency divider is coupled to the voltage-controlled oscillator and used for receiving the input signal and dividing the frequency of the input signal to respectively generate an in-phase signal and a quadrature signal corresponding to the input signal; the frequency mixer is respectively coupled with the voltage-controlled oscillator and the frequency eliminator and is used for mixing the input signal transmitted by the voltage-controlled oscillator and the in-phase signal transmitted by the frequency eliminator to output a mixed signal; the summing amplifier is coupled to the mixer and the frequency divider respectively for integrating the mixed signal and the quadrature signal to generate an output signal with a predetermined frequency.

Description

Power amplification system and related power amplification method suitable for Bluetooth device

technical field

The present invention relates to the application of power amplifiers, especially to the power adjustment of Bluetooth (Bluetooth) transmission.

Background technique

For a conventional direct-up transmitter, the frequency of the voltage-controlled oscillator (VCO) is selected if the same frequency as the even harmonic of the power amplifier (PA) is selected. On the other hand, the frequency of the VCO may be affected by the frequency of the power amplifier, which is also called PA-pulling, which makes the Error Vector Magnitude (EVM) worse, thereby deteriorating the communication quality. Taking a 2.4GHz Bluetooth transmitter as an example, when the VCO signal is 2.4GHz or its multiples (eg, 4.8GHz, 9.6GHz), the above-mentioned power amplifier pulling effect will occur.

At present, there are some prior technologies to solve the above problems. In order to have a more specific concept, the following will give a general introduction to these related technologies:

Please refer to FIG. 1, which is a schematic diagram of a prior art Bluetooth transmitter. For more details, please refer to "H. Darabi, et al., "A Dual-Mode 802.11b/Bluetooth Radio in 0.35um CMOS," IEEEJ .Solid State Circuits, pp.698-706.Mar.2005”. In the Bluetooth local oscillator (LO) generation architecture shown in Figure 1, in order to avoid the power amplifier pulling effect on the VCO, the VCO frequency is selected at 2/3 of the LO frequency (2.4GHz), that is, 1.6GHz ; The mixer (Mixer) is a double sideband mixer (doublesideband mixer, DSB) structure. The disadvantage of this method is that in addition to the 2.4GHz signal at the output end of the mixer, there will be an additional non-ideal spur at 800MHz, which greatly affects the power amplification characteristics.

Please refer to FIG. 2. FIG. 2 is a schematic diagram of a fractional frequency multiplier of the prior art (for details, please refer to "A. Bevilacqua" A 2.7-6.1GHz CMOS Local Oscillator Based on FrequencyMultiplication by 3/2, "2011NORCHIP"), Among them, when the VCO is deliberately selected to be 2/3 times of 2.4G to avoid the pulling effect of the power amplifier, the output of the final mixer needs to be restored by 3/2 times to obtain a 2.4G signal. In order to achieve this purpose, this document first divides the VCO frequency by two through a frequency divider, and then multiplies the frequency to create a three-fold effect, and finally obtains an output frequency that is 1.5 times the VCO frequency. However, the above method must use an odd-numbered frequency multiplier structure, and the odd-numbered frequency multiplier structure is not only very complicated in design, but also increases a lot of cost, so such a method of directly multiplying the output end is not ideal.

US Publication No. US20110140746A1 discloses the technology of using a single sideband (single sideband, SSB) mixer architecture as a mixer (Mixer), although the technology can additionally suppress non-ideal spurs, but the disadvantage is that the two inputs of the mixer Both ends need an In-phase/Quadrature (I/Q) signal.

Next, referring to FIG. 3 , US Patent No. US7894778 discloses a multiband LO generator, which can adjust the frequency to 1.5 times or 1.25 times, thereby narrowing the frequency modulation range of the VCO. However, the disadvantage of the above approach is that the non-ideal spur will get closer to the desired output frequency with the degree of decimalization.

In addition, US Patent No. US9548774 discloses an N-path filter structure, which is used to generate a band reject frequency response through the N-path filter, and the output end adopts a double sideband (DSB) The mixer filters out the non-ideal spurs, but the disadvantage is that it needs to generate the clock required for N-channel filtering. If N=4, it needs to generate a clock of 25% duty cycle. If there is a good filtering The effect must be increased in order. The disadvantage of the above method is that it is not easy to expand the order, and the higher the order, the smaller the duty cycle of the operation, and therefore the more power consumption.

In addition, US Patent Nos. US7515931 and US8121214 propose to use a band-pass filter (BPF) to filter out non-ideal spurs. Although the band-pass filter is relatively simple, the disadvantage is that it will occupy a large area, which is undoubtedly a kind of increase in cost.

To sum up, many prior techniques cannot improve the problem of power amplifier pulling effect without causing side effects. Therefore, there is a need for a novel method and related circuit to improve the above problem.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a power amplification system suitable for a Bluetooth device and a related method, so as to solve the bottleneck faced by the prior art without causing side effects.

At least one embodiment of the present invention provides a power amplification system suitable for a Bluetooth device, the power amplification system is used to generate an output of a predetermined frequency, and the power amplification system includes a voltage controlled oscillator, a frequency divider, a mixer and a summing amplifier. The voltage-controlled oscillator is used for providing an input signal whose frequency is a non-integer multiple of the predetermined frequency; the frequency divider is coupled to the voltage-controlled oscillator for receiving the input signal and dividing the frequency of the input signal, to respectively generate an in-phase signal and a quadrature signal corresponding to the input signal; the mixer is respectively coupled to the voltage controlled oscillator and the frequency divider for the voltage The input signal from the controlled oscillator and the in-phase signal from the frequency divider are mixed to output a mixed signal; and the summing amplifier is respectively coupled to the frequency mixer and the frequency divider , for integrating the mixed signal and the quadrature signal to generate a first output signal having a frequency multiplier of the predetermined frequency.

At least one embodiment of the present invention provides a power amplifying method suitable for a Bluetooth device, the power amplifying system is used to generate an output of a predetermined frequency, and the power amplifying method includes: providing a frequency that is a non-integer multiple of the predetermined frequency the input signal; divide the frequency of the input signal to respectively generate an in-phase signal and a quadrature signal corresponding to the input signal; the input signal from the voltage controlled oscillator and the frequency divider from the frequency divider The in-phase signal is mixed to output a mixed signal; and the mixed signal and the quadrature signal are integrated to generate a first output signal having a frequency multiplier of the predetermined frequency.

To sum up, the present invention mainly generates a reverse spur signal to eliminate spurs by means of feed forward. This method not only does not require I/Q phase for the mixer, but also does not require high-order output at the output. Filtering or setting the inductance can eliminate the non-ideal spur of the mixer. In other words, the present invention can achieve the desired PA effect at a lower cost and eliminate non-ideal spurs.

Description of drawings

1 to 3 are filters designed for the prior art for harmonic interference.

FIG. 4 is a schematic diagram of a power amplification system suitable for a Bluetooth device according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of an amplitude phase controller of the power amplification system of FIG. 4 according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of the summing amplifier of FIG. 4 according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of applying the power amplification system shown in FIG. 4 to 2.4GHz Bluetooth transmission.

FIG. 8 is a flowchart of a power amplification method suitable for a Bluetooth device according to an embodiment of the present invention.

Symbol Description:

400 Power Amplification System

410 Voltage Controlled Oscillator

420 Frequency divider

430 mixer

440 Summing Amplifier

450 Amplitude Phase Controller

460 In-phase/Quadrature Generator

S1 input signal

S2 in-phase signal

S3 Quadrature Signal

S4 Adjusted quadrature signal

S5 mixed signal

S6, S7, S8 output signal

PI_1, PI_2 non-inverting path

PQ_1, PQ_2 quadrature paths

R1, R2 resistance

802～810 steps

Detailed ways

Certain terms are used in the specification and subsequent claims to refer to particular elements. It should be understood by those of ordinary skill in the art that hardware manufacturers may refer to the same components by different nouns. The scope of this specification and subsequent applications does not take the difference in name as a way to distinguish elements, but takes the difference in function of the elements as a criterion for distinguishing. The reference to "comprising" throughout the specification and subsequent claims is an open-ended term, so it should be interpreted as "including but not limited to". Additionally, the term "coupled" herein includes any direct and indirect means of electrical connection. Therefore, if a first device is described as being coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connecting means .

As can be seen from the introduction to the previous technologies, these technologies pay a heavy price in terms of design and cost while solving the pulling effect of the power amplifier. The present invention proposes a simple design, mainly through the feedback forward (Feedforward) technique to create a reverse spur signal to eliminate the non-ideal spur, not only the mixer does not need I/Q phase (that is, does not need to receive The signal is divided into an in-phase signal and a quadrature signal), and the output end does not need to set a high-order filter for high-order filtering or set an inductance, which can eliminate the non-ideal spur of the mixer. Different from the so-called feedback technology, the feedforward technology used in the present invention can be roughly understood as predicting and responding to disturbances before they affect the system.

Please refer to FIG. 4 . FIG. 4 is a schematic diagram of a power amplification system 400 suitable for a Bluetooth device according to an embodiment of the present invention. In order to solve the above-mentioned problems of the prior art, the present invention first sets the VCO frequency at the PA harmonic. On the non-integer frequency, the VCO frequency and the frequency divided by 2 of the VCO are sent to the mixer (Mixer) to generate the required local oscillation frequency (LO frequency). The power amplifying system 400 is used to generate an output of a predetermined frequency (LO), wherein the predetermined frequency may be, for example, twice the local oscillator frequency (2LO), but the invention is not limited thereto. The power amplification system 400 may include a voltage controlled oscillator (VCO) 410, a frequency divider 420, a mixer 430, a summing amplifier 440, an amplitude phase controller 450, and an in-phase/quadrature ( In-phase/Quadrature, I/Q) generator 460. The voltage-controlled oscillator 410 is used to provide an input signal whose frequency is a non-integer multiple of the predetermined frequency (that is, a signal that is not an integer multiple of LO). In this embodiment, the voltage-controlled oscillator 410 provides a frequency of 4 /3LO input signal S1.

The frequency divider 420 is coupled to the voltage controlled oscillator 410 for receiving the input signal with a frequency of 4/3LO from the voltage controlled oscillator 410, and divides the frequency of the input signal S1 to generate corresponding input signals respectively. The signal S1 is an in-phase signal S2 and a quadrature signal S3. The frequency dividing circuit 420 can be a divide-by-2 circuit (marked as "/2" in the figure), and the phase of the in-phase signal S2 and the quadrature signal S3 is different by 90 degrees, but the invention is not limited to this, for example, The frequency dividing circuit 420 can be replaced by a divide-by-4 circuit.

The mixer 430 is coupled to the voltage controlled oscillator 410 and the frequency divider 420 respectively, and is used for the input signal S1 (frequency is 4/3LO) from the voltage controlled oscillator 410 and the in-phase signal from the frequency divider 420 The signal S2 (frequency is 2/3LO) is mixed to output a mixed signal S5, wherein the frequency of the mixed signal S5 is 2LO and has a non-ideal spike at frequency 2/3LO (marked as "(2LO),(2/3LO)"), which is an inevitable phenomenon. The mixer 430 can be implemented by a double sideband mixer (DSB) mixer, but the present invention is not limited to this, and the double sideband mixer belongs to a well-known structure in the art, and details are not repeated.

The amplitude-phase controller 450 is coupled between the summing amplifier 440 and the frequency divider 420 for receiving the quadrature signal S3 transmitted from the frequency divider 420 and generating the adjusted quadrature with a frequency of 2/3LO accordingly. The signal S4 (marked as "-(2/3LO)"), in which the quadrature signal S3 and the in-phase signal S2 have a phase difference of 90 degrees, and through the appropriate adjustment of the amplitude phase controller 450, the adjusted positive signal can be obtained. The crossover signal S4 can generate anti-phase spur signals with the same frequency and opposite phase (180 degrees difference), so as to cancel the spur component in the mixed signal S5. In addition to the 90-degree phase delay provided by the quadrature signal S3, the path between the amplitude-phase controller 450 and the summing amplifier 440 provides a certain degree of phase delay (eg, a 45-degree phase delay), and then the amplitude is adjusted appropriately The phase controller 450 (for example, generating a phase delay of 45 degrees) can make the final phase delay of the adjusted quadrature signal S4 reach 180 degrees.

FIG. 5 is a schematic diagram of the amplitude phase controller 450 of the power amplification system 400 of FIG. 4 according to an embodiment of the present invention. As shown in FIG. 5, it is the basic structure of the amplitude and phase controller of the present invention. The gain of the differential amplifier is controlled by the N-bit signal, which can achieve the effect of adjusting the signal amplitude; in addition, the M-bit signal is used to control the gain of the differential amplifier. The low-pass filter capacitor output by the differential amplifier can achieve the effect of adjusting the signal phase. Generally speaking, the amplitude phase controller 450 can be implemented by a first-order low-pass filter. If the parasitic capacitance generated by the circuit is not enough to generate the required delay, a higher-order low-pass filter, such as a second-order low-pass filter, can be used. pass filter.

The summing amplifier 440 is respectively coupled to the mixer 430 and the amplitude-phase controller 450 for adding the mixed signal S5 and the processed quadrature signal S4 to generate a frequency-multiplied (2LO) output signal with a predetermined frequency S6. The summing amplifier 440 can be implemented by the structure of FIG. 6 . FIG. 6 is a schematic diagram of the summing amplifier 440 of FIG. 4 according to an embodiment of the present invention. By adding and canceling the non-ideal spur output from the mixer 430 with the inverted waveform (ie, the processed quadrature signal S4 with a difference of 180 degrees), it is possible to suppress the non-ideal spur and amplify the desired signal. Effect. As shown in FIG. 6 , using resistors R1 and R2 for the load of the summing amplifier 440 can save the overall area. However, if you want to further improve the effect of suppressing spurs, the resistors in FIG. 6 can be replaced by inductors.

The in-phase/quadrature signal generator 460 is coupled to the output end of the summing amplifier 440 for processing the output signal (2LO) of the summing amplifier 440 to generate at least one output signal having the predetermined frequency (LO). The output signals S7 and S8 with predetermined frequencies (LO) can be obtained from the outputs of the in-phase path PI_2 and the quadrature path PQ_2, respectively. Since the purpose of the in-phase/quadrature signal generator 460 is only to reduce the frequency of the output signal of the summing amplifier 440 by a factor of one, the setting of the in-phase/quadrature signal generator 460 can also be omitted in some cases.

In order to have a better understanding of the present invention, a more practical example will be used for illustration below. Please refer to FIG. 7, which is a schematic diagram of applying the power amplification system 400 shown in FIG. 4 to 2.4GHz Bluetooth transmission. As mentioned earlier, if the VCO signal is a multiplier of 2.4G (eg 2.4GHz, 4.8GHz, 9.6GHz), it will face the problem of power amplifier pulling effect (PApulling). Therefore, in Figure 7, when the target's local When the oscillation signal (LO) is 2.4 GHz, the VCO 410 provides an input of 3.2 GHz to avoid the above problems, but the invention is not limited to this. The mixer 430 then receives the 3.2 GHz signal from the voltage controlled oscillator 410 and the 1.6 GHz signal divided by 2 from the non-inverting path PI_1, and mixes the two. After mixing, the mixer generates 4.8GHz and 1.6GHz signals (ie, non-ideal spikes that must be attenuated or filtered before the LO signal is generated). On the other hand, the amplitude-phase controller 450 generates an anti-phase 1.6 GHz spur signal with the same amplitude and a phase delay of 180 degrees according to the divided 1.6 GHz signal from the quadrature path PQ_1. Since the 90-degree delayed phase can be directly obtained by using the divide-by-2 frequency divider 420 circuit, the phase adjustment range of the amplitude phase controller 450 can be reduced, thereby reducing the order of phase adjustment. Finally, after adding by the adder 440, since the non-ideal spurs have been cancelled, a clean 4.8GHz signal can be obtained, and after processing by the adder 460, the desired 2.4GHz output can be obtained.

FIG. 8 is a flowchart of a power amplification method suitable for a Bluetooth device according to an embodiment of the present invention. Note that these steps do not necessarily have to be performed in the order of execution shown in FIG. 8 if substantially the same results can be obtained. The method shown in FIG. 8 can be adopted by the power amplification system 400 of FIG. 4 and can be briefly summarized as follows:

Step 802: Provide an input signal whose frequency is a non-integer multiple of a predetermined frequency;

Step 804: Divide the frequency of the input signal to respectively generate an in-phase signal and a quadrature signal corresponding to the input signal;

Step 806: Mix the input signal from the voltage-controlled oscillator and the in-phase signal from the frequency divider to output a mixed signal;

Step 808: Integrate the mixed signal and the quadrature signal to generate an output signal having the predetermined frequency;

Step 810: End.

Since those skilled in the art should be able to easily understand the details of each step in FIG. 8 after reading the above paragraphs, further descriptions are omitted here for the sake of brevity.

To sum up, the present invention generates a reverse spur signal by means of forward feedback to eliminate spurs, which can effectively solve the problems faced by the prior art, for example, without increasing a lot of cost (without using high-order filter or band-pass filter) to eliminate spurs in the output signal. Furthermore, although the content of the description mainly emphasizes that the present invention is applicable to a Bluetooth system, the present invention is not limited thereto. For example, under the same/similar concept, the power amplification system and power amplification method of the present invention can also be applied to Wireless Fidelity (WiFi) architecture, such as WiFi2.4G/5G architecture, which can effectively improve the The power amplifier traction effect, thereby improving the communication quality of WiFi.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (10)

1. A power amplification system for a bluetooth device, the power amplification system for generating an output at a predetermined frequency, the power amplification system comprising:

a Voltage Controlled Oscillator (VCO) for providing an input signal having a frequency that is a non-integer multiple of the predetermined frequency;

a frequency divider, coupled to the vco, for receiving the input signal and dividing the frequency of the input signal to generate an in-phase (in-phase) signal and a quadrature (quadrature) signal corresponding to the input signal, respectively;

a frequency mixer, coupled to the voltage-controlled oscillator and the frequency divider, for mixing the input signal from the voltage-controlled oscillator and the in-phase signal from the frequency divider to output a mixed signal; and

and the addition amplifier is respectively coupled with the frequency mixer and the frequency divider and used for integrating the mixed signal and the orthogonal signal to generate a first output signal with the frequency multiplication of the preset frequency.

2. The power amplification system of claim 1, further comprising:

an In-phase/Quadrature (I/Q) generator coupled to the output of the summing amplifier for processing the first output signal to generate at least one second output signal having the predetermined frequency.

3. The power amplifier system of claim 1 wherein the frequency divider circuit is a divide-by-2 circuit and the in-phase signal and the quadrature signal are 90 degrees out of phase.

4. The power amplification system of claim 1 further comprising an amplitude phase controller coupled between the summing amplifier and the frequency divider for receiving the quadrature signal and generating an adjusted quadrature signal accordingly.

5. The power amplification system of claim 4, wherein the amplitude phase controller comprises:

an amplitude control unit for adjusting the amplitude of the quadrature signal according to the signal amplification factor of the mixer; and

a phase control unit for adjusting the phase of the quadrature signal.

6. The power amplification system of claim 5, wherein the phase control unit adjusts the phase of the quadrature signal according to the phase of the quadrature signal and a path delay between the summing amplifier and the amplitude phase controller to generate the adjusted quadrature signal.

7. The power amplification system of claim 4 wherein the adjusted quadrature signal is an inverted spur signal to cancel the spur signal generated by the mixer.

8. The power amplification system of claim 1, wherein the voltage controlled oscillator provides an input signal having a frequency of 4/3 times the predetermined frequency.

9. The power amplification system of claim 1, wherein the mixer is a Double Sideband (DSB) mixer.

10. A power amplification method for a bluetooth device, the power amplification system for generating an output at a predetermined frequency, the power amplification method comprising:

providing an input signal with a frequency which is a non-integral multiple of the predetermined frequency;

dividing the frequency of the input signal to generate an in-phase (in-phase) signal and a quadrature (quadrature) signal corresponding to the input signal;

mixing the input signal from the voltage-controlled oscillator and the in-phase signal from the frequency divider to output a mixed signal; and

the mixed signal and the quadrature signal are integrated to generate a first output signal having a frequency multiplied by the predetermined frequency.

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