CN113225277B - Signal processing device and signal processing method - Google Patents
Signal processing device and signal processing method Download PDFInfo
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- CN113225277B CN113225277B CN202010070985.0A CN202010070985A CN113225277B CN 113225277 B CN113225277 B CN 113225277B CN 202010070985 A CN202010070985 A CN 202010070985A CN 113225277 B CN113225277 B CN 113225277B
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- 238000003672 processing method Methods 0.000 title claims description 16
- 230000000670 limiting effect Effects 0.000 claims abstract description 46
- 238000001914 filtration Methods 0.000 claims abstract description 39
- 230000004044 response Effects 0.000 claims description 48
- 238000004891 communication Methods 0.000 claims description 14
- 230000002238 attenuated effect Effects 0.000 claims description 8
- 230000002829 reductive effect Effects 0.000 claims description 7
- 230000003313 weakening effect Effects 0.000 claims description 7
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- 238000010586 diagram Methods 0.000 description 17
- 230000003044 adaptive effect Effects 0.000 description 14
- 238000012549 training Methods 0.000 description 8
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
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Abstract
A signal processing device comprises a decision feedback equalizer and a coefficient adjusting circuit. The decision feedback equalizer comprises a first equalizer for performing a filtering operation on a first signal according to a set of first coefficients to generate a first filtered signal, wherein the set of first coefficients comprises a plurality of first coefficients. The coefficient adjustment circuit is used for adaptively adjusting one or more of the first coefficients according to an error signal. A limiting operation of the first coefficients is also selectively performed, at least one of the first coefficients being set to a first predetermined value when the limiting operation of the first coefficients is performed to produce a limited set of first coefficients.
Description
Technical Field
The present invention relates to a signal processing device applicable in a communication device, and more particularly, to a signal processing device capable of effectively reducing the influence of radio frequency interference on system performance.
Background
Communication systems typically include communication devices such as transmitters and receivers. The transmitter sets the signal to be transmitted, e.g., one or more symbols, to a corresponding voltage level according to the content carried by the signal during modulation, and transmits the signal after appropriate processing (e.g., signal processing such as encoding, amplifying, etc.). The receiver is responsible for receiving the signal and processing the received signal. The receiver circuit typically includes a decision device, or slicer, for determining the voltage level corresponding to the symbol transmitted by the transmitter. However, in most communication systems, interference generated from outside or inside may cause the transmission signal to deviate in voltage, for example, noise in the transmission channel may cause the voltage level of the transmission signal to deviate from its ideal voltage level (i.e., the voltage level set by the transmitting end), which may further cause the decision device to determine an error.
In view of this, the communication device is typically configured with associated circuitry/devices to compensate for the effects of the channel effects on the signal. The compensation circuit/device can adjust/train the relevant parameters in an adaptive manner, so that the channel effect compensation performance can be optimized. However, the environment in which the parameters are typically trained does not include the radio frequency interference that is actually present in the real communication environment. Therefore, although the parameters of the compensation circuit/device can be adjusted to the optimal values during the training process, the overall performance of the receiver circuit is still affected by the radio frequency interference when the receiver circuit actually starts to operate. For example, since the rf front-end circuitry and/or compensation circuitry/devices of the receiver typically perform some degree of post-amplification processing on the received signal, unwanted rf interference components are also amplified. When the radio frequency interference becomes too large after amplification, the voltage level offset of the required signal is too large, and the receiving end misjudges due to the too large voltage level offset, so that the communication efficiency is reduced. If the receiving end continuously generates the problem of misjudgment or packet error, serious consequences such as the connection interruption of the receiving end and the transmitting end can be finally caused.
Disclosure of Invention
An objective of the present invention is to provide a signal processing method and a related signal processing apparatus, so as to solve the problem of excessive radio frequency interference. In the signal processing method and the corresponding signal processing device, the frequency response of the equalizer can be effectively weakened by limiting the parameters of the equalizer in the frequency domain or in the time domain.
An embodiment of the invention provides a signal processing apparatus, which includes a decision feedback equalizer and a coefficient adjustment circuit. The decision feedback equalizer comprises a first equalizer for performing a filtering operation on a first signal according to a set of first coefficients to generate a first filtered signal, wherein the set of first coefficients comprises a plurality of first coefficients. The coefficient adjustment circuit is used for adaptively adjusting one or more of the first coefficients according to an error signal. A limiting operation of the first coefficients is more selectively performed, and when the limiting operation of the first coefficients is performed, at least one of the first coefficients is set to a first predetermined value to generate a limited set of first coefficients.
Another embodiment of the present invention provides a signal processing method, including: adaptively adjusting a set of first coefficients of a first equalizer according to an error signal, wherein the set of first coefficients comprises a plurality of first coefficients; selectively performing a limiting operation of the set of first coefficients in response to a control signal after adaptively adjusting the set of first coefficients, wherein at least one of the first coefficients is set to a first predetermined value when the limiting operation is performed to generate a set of limited first coefficients; and providing the set of first coefficients or the set of restricted first coefficients to the first equalizer, so that the first equalizer performs a filtering operation according to the set of first coefficients or the set of restricted first coefficients, wherein the set of first coefficients and the set of restricted first coefficients are coefficients of the first equalizer in a time domain.
Another embodiment of the present invention provides a signal processing method, including: adaptively adjusting a set of first coefficients of a first equalizer according to an error signal, wherein the set of first coefficients comprises a plurality of first coefficients; and providing the set of first coefficients or the set of restricted first coefficients to the first equalizer, causing the first equalizer to perform a filtering operation according to the set of first coefficients or the set of restricted first coefficients, wherein the set of first coefficients and the set of restricted first coefficients are coefficients of the first equalizer in the frequency domain, and wherein the step of adaptively adjusting the set of first coefficients of the first equalizer according to the error signal comprises: selectively performing a limiting operation of the set of first coefficients in response to a control signal, wherein at least one of the first coefficients is also adaptively adjusted according to a weakening factor when the limiting operation is performed to produce the set of limited first coefficients.
Drawings
Fig. 1 is a block diagram showing an exemplary signal processing apparatus according to a first embodiment of the present invention.
Fig. 2 is a block diagram showing an exemplary coefficient adjustment circuit according to the first embodiment of the present invention.
Fig. 3 is a partial block diagram showing a signal processing apparatus according to a first embodiment of the present invention.
Fig. 4 is a flowchart showing an exemplary signal processing method according to the first embodiment of the invention.
Fig. 5 is a schematic diagram showing an exemplary frequency response according to the first embodiment of the invention.
Fig. 6 is a block diagram showing an exemplary signal processing apparatus according to a second embodiment of the present invention.
Fig. 7 is a block diagram showing an exemplary coefficient adjustment circuit according to a second embodiment of the present invention.
Fig. 8 is a partial block diagram showing a signal processing apparatus according to a second embodiment of the present invention.
Fig. 9 is a flowchart showing an exemplary signal processing method according to the second embodiment of the invention.
Fig. 10 is a schematic diagram showing an exemplary frequency response according to the second embodiment of the invention.
Detailed Description
Fig. 1 is a block diagram showing an exemplary signal processing apparatus according to a first embodiment of the present invention. The signal processing apparatus 100 is suitable for a communication apparatus, such as a receiver in a communication system, for processing received signals. The signal processing apparatus 100 may include a decision feedback equalizer 110 and a coefficient adjustment circuit 120. Decision feedback equalizer 110 may include equalizer 111 and equalizer 112, combiner 113, and decision device 114. The equalizer 111 performs a filtering operation on the signal d (n) according to a set of first coefficients to generate a filtered signal d_f (n), wherein the set of first coefficients may include a plurality of first coefficients, and the signal d (n) is an output signal (or referred to as a decision signal) of the decision device 114. The equalizer 112 performs a filtering operation on the signal x (n) according to a set of second coefficients to generate a filtered signal x_f (n), wherein the set of second coefficients may include a plurality of second coefficients, and the signal x (n) may be an input signal of the signal processing apparatus 100 or a received signal of the receiver.
The combiner 113 is coupled to the equalizers 111 and 112 for combining the signal x_f (n) and the signal d_f (n) to generate a processed signal x_p (n). The decision device 114 may be a slicer (slicer) for generating the decision signal d (n) according to the processed signal x_p (n).
The signal processing apparatus 100 may further comprise another combiner 130 coupled to the combiner 113 and the decision device 114 for combining the processed signal x_p (n) and the decision signal d (n), for example, subtracting the two signals to generate the error signal e (n). The coefficient adjustment circuit 120 may adaptively adjust one or more of the first coefficients and one or more of the second coefficients according to the error signal e (n), the decision signal d (n), and the signal x (n). Equations (1) and (2) show the adaptive adjustment operation performed in the coefficient adjustment circuit 120:
c i (n+1)＝c i (n)+μ c [x(n+i)e(n+i)]i= - (K-1), …,0,1, … N (1)
b j (n+1)＝b j (n)+μ b [d(n+j)e(n+j)]J=1, …, N-type (2)
Wherein b j (N) is the coefficient of the equalizer 111 in the time domain (i.e., the coefficient used by the equalizer in the time domain to perform the filtering operation), ci (N) is the coefficient of the equalizer 112 in the time domain, N represents the time index of the sampling time point N, j is the order index of the equalizer 111, i is the order index of the equalizer 112, N is the order (tapnumber) of the equalizer 111, (n+k) is the order of the equalizer 112, μ c To adjust coefficient c i (n) weights used, μ b To adjust coefficient b j (n) the weight used.
Fig. 2 is a block diagram showing an exemplary coefficient adjustment circuit according to the first embodiment of the present invention. As shown, the coefficient adjustment circuit 220 may include a plurality of multipliers (e.g., multipliers 221, 222, 225, and 226), a plurality of combiners (e.g., combiners 223 and 227), and a plurality of delay circuits (e.g., delay circuits 224 and 228) for adjusting the coefficient c according to the error signal e (n), the decision signal d (n), the input signal x (n), and the feedback coefficient i (n) and b j (n) generating coefficient c i (n+1) and b j (n+1)。
According to the first embodiment of the present invention, in addition to the above-described adaptation, the coefficient b of the equalizer 111 is responsive to a control signal constraint_en j A limiting operation of (n) may also be optionally performed. Coefficient b when the limiting operation is performed j In (n)Is set to a predetermined value to produce a restricted set of coefficients. The formula (3) shows the coefficient b j Limiting operation of (n):
b 1 (n)＝p 1 ，b 2 (n)＝p 2 ，…，b M (n)＝p M (3)
Wherein M is<=n, and p 1 ,p 2 ,…,p M Is a constant designed in advance.
FIG. 3 is a partial block diagram showing a signal processing apparatus according to a first embodiment of the present invention for explaining the filtering operation of an equalizer and coefficients b j And (n) a limiting operation. In the first embodiment, the equalizer 111/311 is a feedback equalizer (FeedBack Equalizer, abbreviated as FBE), the equalizer 112/312 is a feedforward equalizer (FeedForward Equalizer, abbreviated as FFE), and the equalizers 111/311 and 112/312 perform filtering operation in the time domain. As shown in FIG. 3, the signals x (n) and d (n) are delayed by a plurality of delay circuits 331 and 332 to generate corresponding delayed signals, and the signals and the corresponding coefficients c are further processed by a plurality of multipliers 333 and 334 -K+1 (n)、c -K+2 (n)…c 0 (n)、c 1 (n)…c N+1 (n)、c N (n) and b 1 (n)…b N-1 (n)、b N (n) or a restricted coefficient p 1 ,p N-1 ,…,p N Multiplication to perform a filtering operation of the filter in the time domain.
As shown in FIG. 3, equalizer 311 may include a plurality of multiplexers 335 for selecting b in response to a control signal constraint_en generated by an external device j (n) or p j Is output to multiplier 333.
Fig. 4 is a flowchart showing an exemplary signal processing method according to the first embodiment of the invention. The signal processing method may be performed by a signal processing apparatus as shown in fig. 1 to 3, and includes the steps of:
step S402: a set of coefficients of the equalizer is adaptively adjusted according to an error signal. The adaptive adjustment performed by the coefficient adjustment circuits 120/220 as shown in equations (1) and (2) and in fig. 2.
Step S404: after adaptively adjusting the set of coefficients, a coefficient limiting operation is selectively performed in response to a control signal. When the limiting operation of the coefficients is not performed, the set of coefficients is not adjusted. When the coefficient limiting operation is performed, coefficient b 1 (n)～b N One or more coefficients b in (n) j (n) will be set to a predetermined value p j To produce a restricted set of coefficients. As shown in equation (3) and fig. 3, b is selectively set according to the control signal constraint_en j (n) or p j Outputs to the corresponding multiplier.
Step S406: the set of coefficients (when the limiting of the coefficients is not performed) or the set of limited coefficients (when the limiting of the coefficients is performed) is provided to the equalizer, causing the equalizer to perform a filtering operation based on the current coefficients. As shown in fig. 3, the corresponding coefficients are output by the multiplexer 335 to perform the filtering operation.
In the first embodiment of the present invention, the limiting operation of the coefficients is performed in the time domain. Setting the 1 st to M-th order coefficients of the equalizer 111/311 to a pre-designed constant by the limiting operation allows the frequency of the equalizer 112/312 to have a reduced gain value in response to a specific frequency band. Since the frequency responses of the equalizer 111/311 and the equalizer 112/312 are related to each other, when the 1 st to M-th order coefficients of the equalizer 111/311 are reshaped (reshape) by the limiting operation, the frequency response of the equalizer 112/312 correspondingly changes due to the reshaping of the coefficients of the equalizer 111/311 even if the coefficients of the equalizer 112/312 are not adjusted. It is assumed that equalizer 112/312 has a first frequency response when equalizer 111/311 performs a filtering operation based on coefficients that are not reshaped (i.e., coefficients generated based on an adaptation), and that equalizer 111/311 performs a filtering operation based on reshaped/constrained coefficients (i.e., one or more coefficients are set to p) j ) When performing the filtering operation, the equalizer 112/312 has a second frequency response, which has a reduced gain value in response to a particular frequency band as compared to the first frequency response.
Fig. 5 is a schematic diagram showing an exemplary frequency response according to the first embodiment of the invention. The frequency response curve 501 represents the frequency response of the equalizer 112/312 when the equalizer 111/311 performs a filtering operation according to the coefficients that have not been reshaped, and the frequency response curve 502 represents the frequency response of the equalizer 112/312 when the equalizer 111/311 performs a filtering operation according to the reshaped/restricted coefficients. As can be seen, the frequency response curve 502 has a reduced gain value in the normalized frequency band of 0 to 0.7 (pi x radial degrees/sample times) compared to the frequency response curve 501, wherein the normalized frequency can be calculated as the frequency/sample frequency.
According to an embodiment of the invention, the limiting operation (reshaping) of the coefficients may be performed during the adaptive training of the coefficients, or may be performed after the adaptive training is completed. For example, the coefficients of the equalizers 111/311 and 112/312 may be adaptively adjusted during an adaptive training process according to the error signal e (n) in order to minimize the error signal e (n). After the adaptive training process is completed, the optimal coefficients are typically trained for the equalizers 111/311 and 112/312. After obtaining the optimal coefficients, the coefficient limiting operation of the feedback equalizer can be performed in the time domain according to the first embodiment of the present invention, wherein the constant p 1 ,p 2 ,…,p M The frequency range over which the gain value is attenuated as desired can be designed in advance. In this way, even if the coefficients of the feedforward equalizer are not adjusted, by limiting the coefficients of the feedback equalizer, the frequency response of the feedforward equalizer can be changed correspondingly, so as to achieve the effect of weakening the gain value.
Fig. 6 is a block diagram showing an exemplary signal processing apparatus according to a second embodiment of the present invention. The signal processing apparatus 600 is suitable for use in a communication device, such as a receiver in a communication system, for processing received signals. The signal processing apparatus 600 may include a decision feedback equalizer 610 and a coefficient adjustment circuit 620. Decision feedback equalizer 610 may include equalizer 611 and equalizer 612, combiner 613, and decision device 614. The equalizer 611 performs a filtering operation on the signal d (n) according to a set of first coefficients to generate a filtered signal d_f (n), wherein the set of first coefficients may include a plurality of first coefficients, and the signal d (n) is an output signal (or referred to as a decision signal) of the decision device 614. Equalizer 612 performs a filtering operation on signal X (n) according to a set of second coefficients to generate a filtered signal x_f (n), wherein the set of second coefficients may include a plurality of second coefficients.
In the second embodiment, the signal processing apparatus 600 or the decision feedback equalizer 610 may further include a fast fourier transform apparatus 615 and an inverse fast fourier transform apparatus 616. The FFT device 615 is configured to perform a FFT (Fast Fourier Transform, abbreviated FFT) on the time-domain signal X (n) to generate the frequency-domain signal X (n), wherein the time-domain signal X (n) may be an input signal of the signal processing device 600 or a received signal of the receiver. The Inverse fast fourier transform unit 616 is configured to perform Inverse fast fourier transform (Inverse FFT, abbreviated as IFFT) on the frequency domain signal (filtered signal) x_f (n) to generate an output signal x_f (n), where the output signal x_f (n) is a time domain signal. The combiner 613 is coupled to the equalizer 611 and the inverse fast fourier transform device 616, and combines the signal x_f (n) and the signal d_f (n) to generate a processed signal x_p (n). The decision device 614 may be a slicer (slicer) for generating the decision signal d (n) according to the processed signal x_p (n).
The signal processing device 600 may further comprise a further combiner 630 and a fast fourier transformation device 640. The combiner 630 is coupled to the combiner 613 and the decision device 614 for combining the processed signal x_p (n) and the decision signal d (n), e.g. subtracting the processed signal x_p (n) from the decision signal d (n), to generate the error signal e (n). The fast fourier transform device 640 is configured to perform fast fourier transform on the error signal E (n) in the time domain to generate the error signal E (n) in the frequency domain.
The coefficient adjustment circuit 620 may adaptively adjust one or more of the first coefficients and one or more of the second coefficients according to the error signals E (n) and E (n), the decision signal d (n), and the input signal X (n). Equations (4) and (5) show the adaptive adjustment operation performed in the coefficient adjustment circuit 620:
C k (n+1)＝(1-α i *leaky_on i )*C k (n)+μ c *X k (n)E k (n), i=1, …, P (4)
b j (n+1)＝b j (n)+μ b [d(n+j)e(n＝j)]J=1, …, N-type (5)
X k (n)＝FFT[x(n)]K=1, 2, …, K (6)
E k (n)＝FFT[e(n)](7)
Wherein b j (n) is the coefficient of equalizer 611 in the time domain, C k (N) is the coefficient of the equalizer 612 in the frequency domain (i.e., the coefficient used by the equalizer in the frequency domain for performing the filtering operation), N represents the time index of the sampling time point N, j is the order index of the equalizer 611, N is the order of the equalizer 611, K is the index of the frequency domain, K represents the number of points of the FFT performed by the FFT device 640, μ c To adjust coefficient c i (n) weights used, μ b To adjust coefficient b j (n) weight used, X k (n) the result of performing the fast Fourier transform on the signal x (n), E k (n) is the result of performing a fast fourier transform on the signal e (n).
In the second embodiment of the present invention, the coefficient C k The limiting operation (reshaping) of (n) is performed according to the switch signal leakage_on in the process of adaptively adjusting i Is selectively performed in which coefficient C k (n) can be further divided into a plurality of groups, and the coefficient C k The limiting operation (reshaping) of (n) can be controlled by groups, i is a group index value, P is the total number of groups, and the switch signal leak_on i The value of (a) can be set to 0 or 1, alpha i To weaken the factor, 0<α i <1. For example, when leak_on i When set to 1, coefficient C belonging to the i-th group k (n) in the course of the adaptive adjustment, the weakening factor alpha is also determined according to the equation (4) i Is adjusted to produce a restricted set of coefficients. When leak_on i When set to 0, coefficient C belonging to the i-th group k (n) will not depend on the attenuation factor alpha during the adaptive adjustment i Is adjusted.
FIG. 7 is a diagram showing a coefficient adjustment according to a second embodiment of the present inventionAn exemplary block diagram of an overall circuit. As shown, the coefficient adjustment circuit 720 may include a plurality of multipliers (e.g., multipliers 721, 722, 725, 726, 727), a plurality of combiners (e.g., combiners 723, 728), and a plurality of delay circuits (e.g., delay circuits 724, 729) for receiving the error signals E (n), E k (n), decision signal d (n) and input signal X k (n) coefficient C of feedback k (n) and b j (n) generating coefficient C k (n+1) and b j (n+1)。
For example, assuming that the FFT device 640 performs a 16-point FFT, i.e., k=16, the equalizer 612 has 16-order coefficients C in the frequency domain k (n). Further, assuming that the total number of groups p=4, each group may include 4 coefficients. When leak_on 1 When set to 1, coefficient C belonging to the 1 st group 1 (n)～C 4 (n) in the course of the adaptive adjustment, the attenuation factor alpha is also determined according to the equation (4) 1 Is adjusted, and so on.
Fig. 8 is a partial block diagram showing a signal processing apparatus according to a second embodiment of the present invention for explaining a filtering operation of an equalizer. In the second embodiment, the equalizer 611/811 is a feedback equalizer (FBE), the equalizer 612/812 is a feedforward equalizer (FFE), the equalizer 611/811 performs filtering operation in the time domain, and the equalizer 612/812 performs filtering operation in the frequency domain. As shown in fig. 8, the equalizer 811 delays the signal d (n) by a plurality of delay circuits 831 to generate a corresponding delay signal, and then the signal and the corresponding coefficient b are multiplied by a plurality of multipliers 833 1 (n)…b N-1 (n)、b N (n) multiplying to perform a filtering operation of the filter in the time domain. On the other hand, the equalizer 812 uses the multiplier 832 to correlate the frequency domain input signal with the corresponding C 1 (n)、C 2 (n)…C K (n) multiplying to perform a filtering operation of the filter in the frequency domain.
Fig. 9 is a flowchart showing an exemplary signal processing method according to the second embodiment of the invention. The signal processing method may be performed by a signal processing apparatus as shown in fig. 6 to 8, and includes the steps of:
step S902: a set of coefficients of the equalizer is adaptively adjusted according to an error signal. The adaptation performed by the coefficient adjustment circuit 620/720 as shown in equations (4) and (5) and in fig. 7.
Wherein, according to the second embodiment of the present invention, the step S902 may further include: selectively performing a limiting operation of coefficients of a feedforward equalizer (FFE) in response to a control signal, wherein at least one of the coefficients of the feedforward equalizer is also adaptively adjusted according to a weakening factor to produce a limited set of coefficients when the limiting operation is performed. As shown in equation (4) and fig. 7, the coefficient C k The limiting operation (reshaping) of (n) is performed according to the switch signal leakage_on in the process of adaptively adjusting i Selectively executed.
Step S904: the set of coefficients (when the limiting operation of the coefficients is not performed) or the set of limited coefficients (when the limiting operation of the coefficients is performed) is provided to the equalizer, causing the equalizer to perform a filtering operation according to the current coefficients.
In a second embodiment of the invention, the limiting operation (reshaping) of the coefficients of the feedforward equalizer (FFE) is performed in the frequency domain. Weakening one or more coefficients of equalizer 612/812 by the limiting operation according to a pre-designed weakening factor may cause the frequency response of equalizer 612/812 to have a weakened gain value in response to a particular frequency band. It is assumed that equalizer 612/812 has a first frequency response when equalizer 612/812 performs a filtering operation based on coefficients that are not reshaped (i.e., coefficients that are generated based on adaptation and are not attenuated), and that equalizer 612/812 has a second frequency response when equalizer 612/812 performs a filtering operation based on reshaped/restricted coefficients (i.e., coefficients that are generated based on adaptation and one or more of which are attenuated), the second frequency response has an attenuated gain value in comparison to the first frequency response.
Fig. 10 is a schematic diagram showing an exemplary frequency response according to the second embodiment of the invention. The frequency response curve 1001 represents the frequency response when the equalizer 612/812 performs a filtering operation according to the coefficients that are not reshaped, and the frequency response curve 1002 represents the frequency response when the equalizer 612/812 performs a filtering operation according to the reshaped/restricted coefficients. As can be seen, the frequency response curve 1002 has a reduced gain value in the normalized frequency band of 0 to 0.8 (pi x radial degrees/sample times) compared to the frequency response curve 1001.
According to an embodiment of the invention, the limiting operation (reshaping) of the coefficients may be performed during adaptive training of the coefficients, or after obtaining the optimal coefficients. For example, the coefficients of the equalizers 611/811 and 612/812 may be adaptively adjusted during an adaptive training process according to the error signal e (n) in an effort to minimize the error signal e (n). After the adaptive training process is substantially complete, the optimal coefficients may typically be trained for the equalizers 611/811 and 612/812. After obtaining the optimal coefficients, the second embodiment of the present invention performs the coefficient limiting operation of the feedforward equalizer in the frequency domain, wherein the switch signal leakage_on i Attenuation factor alpha i The frequency range over which the gain value is attenuated as desired can be designed in advance. In this way, the frequency response of the feedforward equalizer may be correspondingly changed to achieve the effect of the attenuated gain value.
The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
[ symbolic description ]
100. 600: signal processing device
110. 610: decision feedback equalizer
111. 112, 311, 312, 611, 612, 811, 812: equalizer
113. 130, 223, 227, 613, 630, 723, 728: coupling device
114. 614: decision making device
120. 220, 620, 720: coefficient adjusting circuit
221. 222, 225, 226, 333, 334, 721, 722, 725, 726, 727, 832, 833: multiplier unit
224. 228, 331, 332, 724, 729, 831: delay circuit
335: multi-task device
501. 502, 1001, 1002: frequency response curve
615. 640: fast fourier transform device
616: fast Fourier inverse conversion device
b 1 (n)、b 1 (n+1)、b N-1 (n)、b N (n)、b N (n+1)、c -K+1 (n)、c -K+1 (n+1)、c -K+2 (n)、c 0 (n)、c 0 (n+1)、c 1 (n)、c N-1 (n)、c N (n)、C 1 (n+1)、C 2 (n+1)、C K (n+1)、C N (n+1)、C 1 (n)、C 2 (n)、C K (n)、p 1 、p N-1 、p N Coefficients of
constraint_en control signal
d(n)、d(n+1)、d(n+N)、d_f(n)、e(n)、e(n-K+1)、e(n+1)、e(n+N)、E(n)、E 1 (n)、E 2 (n)、E K (n)、x(n)、X(n)、X 1 (n)、X 2 (n)、X K (N), X (N-k+1), X (n+1), X (n+n), x_f (N), x_p (N): signal signal
leaky_on i : switch signal
α i : attenuation factor
μ b 、μ c : weighting of
Claims (9)
1. A signal processing apparatus, the signal processing apparatus comprising:
a decision feedback equalizer comprising:
a first equalizer for performing a filtering operation on the first signal according to a set of first coefficients to generate a first filtered signal, wherein the set of first coefficients includes a plurality of first coefficients, an
A second equalizer for performing a filtering operation on the second signal according to a set of second coefficients to generate a second filtered signal, wherein the set of second coefficients includes a plurality of second coefficients, an
A coefficient adjustment circuit for adaptively adjusting one or more of the first coefficients according to the error signal,
wherein the limiting of the plurality of first coefficients is also selectively performed, at least one of the plurality of first coefficients being set to a first predetermined value to produce a set of limited first coefficients when the limiting of the plurality of first coefficients is performed, and the second equalizer having a particular frequency response having a reduced gain value in response to a particular frequency band when the first equalizer performs a filtering operation according to the set of limited first coefficients, and
wherein the coefficient adjustment circuit also adaptively adjusts one or more of the plurality of second coefficients based on the error signal, and the limiting operation of the plurality of second coefficients is also selectively performed in adaptively adjusting the one or more of the plurality of second coefficients, and when the limiting operation of the plurality of second coefficients is performed, at least one of the plurality of second coefficients is also adjusted based on a de-emphasis factor in adaptively adjusting the one or more of the plurality of second coefficients to produce a restricted set of second coefficients.
2. The signal processing device of claim 1, wherein the first equalizer is a feedback equalizer and the second equalizer is a feedforward equalizer.
3. The signal processing apparatus of claim 2, wherein the decision feedback equalizer further comprises:
a first combiner, coupled to the first equalizer and the second equalizer, for combining the first filtered signal and the second filtered signal to generate a processed signal;
decision means for generating a decision signal based on the processed signal; and
a second combiner, coupled to the first combiner and the decision device, for combining the processed signal and the decision signal to generate the error signal.
4. The signal processing apparatus of claim 1, wherein the set of second coefficients and the set of restricted second coefficients are coefficients of the second equalizer in a frequency domain, and frequencies corresponding to the set of restricted second coefficients have impaired gain values in response to a particular frequency band after the restricting operation of the plurality of second coefficients is performed.
5. The signal processing apparatus of claim 1, further comprising:
a fast fourier transform device coupled to the second equalizer for performing a fast fourier transform on an input signal to generate the second signal;
an inverse fast fourier transform device coupled to the second equalizer for performing inverse fast fourier transform on the second filtered signal to generate an output signal;
a first combiner, coupled to the first equalizer and the inverse fast fourier transform device, for combining the first filtered signal and the output signal to generate a processed signal;
decision means for generating a decision signal based on the processed signal; and
a second combiner, coupled to the first combiner and the decision device, for combining the processed signal and the decision signal to generate the error signal.
6. A signal processing method, comprising:
adaptively adjusting a set of first coefficients of a first equalizer according to an error signal, wherein the set of first coefficients comprises a plurality of first coefficients;
adaptively adjusting a set of second coefficients of a second equalizer according to the error signal, wherein the set of second coefficients comprises a plurality of second coefficients;
selectively performing a limiting operation of the set of first coefficients in response to a control signal after adaptively adjusting the set of first coefficients, wherein at least one of the plurality of first coefficients is set to a first predetermined value when the limiting operation is performed to generate a set of limited first coefficients; and when the first equalizer performs a filtering operation according to the set of limited first coefficients, the second equalizer has a particular frequency response having a attenuated gain value in response to a particular frequency band;
providing the set of first coefficients or the set of restricted first coefficients to the first equalizer, causing the first equalizer to perform a filtering operation according to the set of first coefficients or the set of restricted first coefficients; and
providing the set of second coefficients to the second equalizer, causing the second equalizer to perform a filtering operation based on the set of second coefficients,
wherein adaptively adjusting a set of second coefficients of a second equalizer based on the error signal comprises:
adaptively adjusting one or more of the plurality of second coefficients according to the error signal, and the limiting operation of the plurality of second coefficients is also selectively performed in adaptively adjusting the one or more of the plurality of second coefficients, and when the limiting operation of the plurality of second coefficients is performed, at least one of the plurality of second coefficients is also adjusted according to a reduction factor in adaptively adjusting the one or more of the plurality of second coefficients to produce a set of limited second coefficients,
wherein the set of first coefficients and the set of restricted first coefficients are coefficients of the first equalizer in the time domain.
7. The signal processing method of claim 6, wherein the set of second coefficients is coefficients of the second equalizer in a time domain;
wherein the first equalizer is a feedback equalizer in the communication device, and the second equalizer is a feedforward equalizer in the communication device.
8. A signal processing method, comprising:
adaptively adjusting a set of first coefficients of a first equalizer according to an error signal, wherein the set of first coefficients comprises a plurality of first coefficients;
adaptively adjusting a set of second coefficients of a second equalizer according to the error signal, wherein the set of second coefficients comprises a plurality of second coefficients;
providing the set of first coefficients or the set of restricted first coefficients to the first equalizer, causing the first equalizer to perform a filtering operation according to the set of first coefficients or the set of restricted first coefficients; and
providing the set of second coefficients to the second equalizer, causing the second equalizer to perform a filtering operation based on the set of second coefficients,
wherein the set of first coefficients and the set of restricted first coefficients are coefficients of the first equalizer in a frequency domain, and wherein the step of adaptively adjusting the set of first coefficients of the first equalizer according to the error signal comprises:
selectively performing a limiting operation of the set of first coefficients in response to a control signal, wherein when the limiting operation is performed, at least one of the plurality of first coefficients is also adaptively adjusted according to a weakening factor to produce the set of limited first coefficients; and the second equalizer has a particular frequency response having a reduced gain value in response to a particular frequency band when the first equalizer performs a filtering operation based on the set of limited first coefficients.
9. The signal processing method of claim 8, wherein the first equalizer is a feed-forward equalizer in the communication device, and after the limiting of the set of first coefficients is performed, frequencies corresponding to the set of limited first coefficients have attenuated gain values in response to a particular frequency band.
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