TWI462544B - Method and apparatus for compensation of frequency-dependent i/q imbalance - Google Patents

Description

Compensation method and device for frequency dependent I/Q imbalance

The present invention relates to a compensation method, and more particularly to a compensation method and apparatus for frequency dependent I/Q imbalance.

The data transmission of the existing wireless network is to support the rapid growth of the number of users and the popular signal coverage. In the modulation and demodulation of the signal, a signal transmission architecture capable of implementing multiple input and multiple output has been adopted, especially in the signal transmission architecture. The signal receiving end often seeks to correctly decode the data, and uses multiple antennas to receive the RF signal, and then uses the synchronous signal technology and the filter to eliminate the noise, so that the desired receiving data can smoothly compensate the signal phase and amplitude. Decoding with demodulation, and obtaining the same data as the transmission end has become an indispensable technical means for large-scale wireless transmission systems. Among them, if you want to reply to the signal phase and amplitude, you must first compensate the frequency-dependent I/Q imbalance, because the freeness of the received signal relative to its correct value will determine that a signal located near the correct value is Complete demodulation is the probability of, for example, a digital signal.

Compensating for the I/Q imbalance helps to homogenize the pilot signal of the carrier, and further, the signal receiving module can be recovered without the need to provide a signal for a large number of errors. , quickly get the information you get.

Currently, the frequency dependent I/Q imbalance compensation is directly estimated by using the known time domain or frequency domain preamble sequence or pilot signal and compensated in the time domain or the frequency domain; but in some specifications The format of the preamble sequence in the time domain or the frequency domain is not enough to estimate the I/Q parameters, or even if there are enough I/Q parameters, it will make the design of the signal receiving module more complicated and increase the operation. The burden is not enough to satisfy the immediate transmission characteristics of the current wireless system.

Another method of compensation is to use the time domain filter to compensate, but this involves the design of poles and zeros of different types of filters such as Chebyshev filters. Adapting to the operation of the dynamic wireless system, this will increase the time required for convergence, and also increase the manufacturing cost of the signal receiver invisibly. However, how to make a specific contribution to the application of wireless communication signal receiving technology through limited technical improvement, it is necessary to cooperate with the evolution of various useful detection and debugging methods to correctly regulate and obtain relevant results.

In order to solve the above problems, the inventors have intensively studied and analyzed, and countless experiments and improvements, and finally developed a new compensation method and device for frequency dependent I/Q imbalance, supplemented by electronic operation execution method, and developed a kind It has a very good compensation device for software and hardware integration and system utilization.

The present invention discloses that a multi-phase clock generator can be used to reduce the effect of filter offset, and the preamble sequence of the time domain is transferred to the frequency domain, and compared with the preamble sequence of the original frequency domain. Accurately extracting I/Q unbalanced parameters to compensate for it, can effectively reduce the complexity of the wireless signal receiving end design, and provide the signal-to-noise ratio (SNR) of the communication system to the received signal error rate ( Bit error rate) Effective maintenance.

Therefore, the present invention provides a compensation method for frequency dependent I/Q imbalance, which comprises: individually controlling an I path analog/digital converter and a Q path analog/digital converter, thereby reducing the bias of the complex filter. An I/Q imbalance effect; and an unequal crossover ratio of the complex preamble sequence in the time domain and the frequency domain, the I/Q imbalance parameter can be estimated in a frequency domain residual to the I/ Q is unbalanced to implement compensation.

According to the above concept, the complex main waves of the filters are coherent to reduce the influence of the bias of the filters on the I/Q imbalance.

According to the above concept, the step of estimating the unequal cross ratio of the I/Q imbalance comprises: collecting a complex short preamble sequence in the time domain; converting the short preamble sequences to a virtual long preamble sequence in the frequency domain via a Fourier transform; And using a multiple input multiple output (MIMO) long preamble sequence and the virtual long preamble sequence to find the unequal cross ratio. The Fourier transform is converted to a fast Fourier transform.

According to the above concept, the unequal cross ratio can be obtained by the following formula:

Where C _i (k) is the unequal cross ratio, MLP _i,1 (k) is the MIMO long preamble sequence, VirtualLP _i (k) is the virtual long preamble sequence, i is the transmit antenna index, and k is a sub Carrier index, and the asterisk (*) indicates the conjugate complex function of the MIMO long preamble sequence or the virtual long preamble sequence, and -k indicates the length of the MIMO long preamble sequence plus 1-k, which is orthogonal frequency division multiplexing. The mirrored position of the data subcarriers of the symbol of the technology (OFDM).

The invention further provides a wireless frequency compensation device, comprising: an I/Q frequency compensation estimator connected to a multi-phase timing generator and a radio frequency receiver via a Fourier converter, and capable of receiving from more than one Inputting a data of a multiple output (MIMO) channel estimator, wherein the I/Q frequency compensation estimator can estimate an I/Q imbalance parameter using an unequal cross ratio of an I/Q imbalance; and an analogy /Digital converter, performing a anti-skew sampling to provide a complex digital signal stream to the I/Q frequency compensation estimator.

The present invention further provides a compensation apparatus comprising: an I/Q compensation estimator that calculates a parameter associated with an I/Q imbalance via an unequal crossover ratio to correct the I/Q imbalance. .

The invention further provides a compensation device, comprising: an I/Q compensator, which calculates and obtains a signal by receiving a signal and calculating a ratio of a real component and an imaginary component of the signal in a frequency domain. Compensation parameters.

According to the above concept, a tuning sequence can be obtained by performing fast Fourier transform on the real component and the imaginary component of the signal, wherein the tuning sequence comprises a multiple input multiple output (MIMO) long preamble sequence and A virtual long frontian.

According to the above concept, wherein the compensation parameter is a quasi-sequence by estimating at least one quarter of the subcarriers, and it satisfies the ratio not being zero, thereby correcting an I/Q imbalance for the signal.

In short, the present invention wants to reduce the SNR requirement during the entire compensation process without increasing the convergence time, so a skew calibration mechanism is provided to control the analog/digital conversion of the I path separately. And Q-path analog/digital converters to reduce the effects of filter bias on I/Q imbalance and provide an innovative I/Q imbalance compensation method that utilizes a finite number of time domain preamble sequences ( Preamble) is converted to the frequency domain to compare with the original frequency domain long preamble sequence to find the required I/Q imbalance information to estimate and compensate for the remaining frequency dependent I/Q imbalance, not only for existing wireless The demodulation of network transmission signal reception can also be applied to the integration of emerging system chips and applications in the future.

The present invention can be achieved by the I/Q imbalance model and its parameter calculation compensation, as shown in the schematic diagram of the I/Q imbalance model of FIG. 1 , wherein the antenna 110 receives a wireless signal and is respectively a signal oscillation generator 113. The signal and the two sets of signals generated by the 90-degree phase difference signal 114 are demodulated, and the demodulation can be operated by the multipliers 111, 112 to make the two sets of signals become the I path signal I _LQ1 (t )=Z ₁ (t)cos(2πf _c t) and Q path signal Q _LQ1 (t)=-Z ₁ (t)(1+ε ₁ )sin(2πf _c t+Θ ₁ ), where Θ ₁ and ε ₁ is the phase difference and the distortion amplitude caused by the signal transmission channel, respectively, and the distortion amplitude is defined by the Q path signal obtained by an amplitude amplifier, and the phase difference and the distortion amplitude are displayed in the Q path signal. The two path signals are then passed through the low frequency filters 116, 117 having the transfer functions h _I(t) and h _Q(t) to filter the high frequency signals, and then individually pass through the I path analog/digital converters 118 and Q. The analog/digital converter 119 of the path obtains two sets of fundamental frequency signals I _BB (t) and Q _BB (t). The complex fundamental signals generated by the four sets of wireless signal processing modules 11, 12, 13, 14 are then provided to a multiple input multiple output orthogonal frequency division multiplexing (OFDM) modulation demodulator 15 for processing.

In an embodiment of the invention, in order to reduce the effects of a filter offset, we control the I-path analog/digital converter 118 and the Q-path analog/digital converter 119 to filter the I/Q path, respectively. The main pulse signal is coherent, so that the filter bias reduces the subsequent I/Q imbalance, and then the time domain and frequency domain preamble sequences are used to estimate and compensate the I/Q imbalance parameters.

As shown in FIG. 2, a schematic diagram of the frequency domain I/Q imbalance estimation and compensation module, the RF signals received by the four antennas 21 are individually passed through the RF processing block 22, and then the I/Q is utilized by the multi-phase clock generator 23. The main pulse signal of the path filter is coherent, and the processed signal is serially converted into parallel block 24 and fast Fourier transform block 25 to form an organized data combination, and then the data combination can be simultaneously input into the frequency domain I/ The Q imbalance estimation compensator 27 and the multiple input multiple output channel estimator 26, after which the frequency domain I/Q imbalance estimation compensator 27 reuses the received data combination with the message from the MIMO channel estimator 26, The remaining I/Q imbalance parameters are estimated and the received signal is corrected to compensation information 28.

In order to estimate the parameters of the remaining IQ, the preamble sequence that meets the following conditions needs to be found.

However, the long preamble sequence in the frequency domain does not meet the above characteristics, so the short preamble sequences of m time domains are collected and converted into frequency domain contents by fast Fourier transform, and the content of the frequency domain is called virtual length. Leader sequence (VirtualLP). As shown in the following formula, where CSP is a short preamble sequence in the time domain, and ( k ) is the relevant conversion parameter of the fast Fourier transform.

Thus, the characteristics of Ci(k)≠0 can be found using the virtual long preamble sequence and the long preamble sequence in the original frequency domain, and the parameters of the I/Q imbalance are obtained as follows.

The MLP is the long leading sequence of the original frequency domain.

Figure 3 is a diagram showing the position of the virtual long preamble sequence and the subcarriers of the original frequency domain long preamble sequence in frequency, wherein the subcarriers 31 of the virtual long preamble sequence and the subcarriers 32 of the original frequency domain long preamble sequence are estimated to be at least four quarters. The subcarrier 33 of the original frequency domain long preamble sequence is a quasi-sequence, and it satisfies the characteristic of Ci(k) ≠0, thereby correcting an I/Q imbalance for the transmission signal.

By comparing the benefits that can be achieved by the present invention under different signal transmission conditions, reference can be made to the system performance diagram of the 802.11n multiple-input multiple-output orthogonal frequency division multiplexing (OFDM) system as shown in Figures 4a and 4b. In Figures 4a and 4b, 411 and 421 are the system performance curves of the wireless communication system under ideal compensation conditions, and 412 and 422 are the system performance curves of the system under offset calibration and I/Q compensation, 413 And 423 is the system performance curve of the system without offset calibration but with I/Q compensation, and 414 and 424 are the system performance curves of the system without any compensation. It can be found that the method of the present invention is applied to the 802.11n multiple-input multiple-output orthogonal frequency division multiplexing (OFDM) system via TGnD (8 taps and 50-ns rms delay distribution, as shown in Fig. 4a) and TGnE ( 15 taps and 100-ns rms delay distribution, as shown in Figure 4b), the resulting signal-to-noise ratio loss is approximately 1.5 dB (compare 411 and 412 and compare 421 and 422); Without the separate control of the I path analog/digital converter and the Q path analog/digital converter and the main pulse signal of the I/Q path filter, the overall system performance will be reduced by 1.5 dB~1.8 dB (compare 412 with 413 and comparing 422 and 423), therefore, the method of offset calibration proposed by the present invention can surely reduce the signal-to-noise ratio required for the wireless communication system to achieve a fixed transmission data error rate. In addition, I/Q does not Balance compensation also does provide this performance improvement for wireless communication systems.

The compensation convergence time of the wireless transmission of the 802.11n multiple-input multiple-output orthogonal frequency division multiplexing (OFDM) system is less than or equal to the preamble sequence, as compared to the use of the time domain filter to compensate for a longer convergence time. The time taken by the number is therefore more advantageous. Through the above description of the preferred embodiment, it can be known that the analog/digital converter that controls the I path and the Q path is used to reduce the influence of the bias of the filter on an I/Q imbalance, and a limited number of The preamble of the time domain is converted to the frequency domain to be compared with the original frequency domain long preamble sequence to find the required IQ information to estimate and compensate for the remaining frequency domain signal I/Q imbalance, and the present invention The above-mentioned analog/digital converter 118 for controlling the I path and the analog/digital converter 119 of the Q path are respectively used to reduce the signal noise ratio requirement required by the system, and simultaneously estimate the preamble sequence in the time domain and the frequency domain. Out of the frequency dependent I/Q imbalance parameters, overcoming the use of only the frequency domain leader sequence is not sufficient to estimate the I/Q imbalance.

Products using the technology of the present invention include various integrated circuit components related to fundamental frequency communication and digital television, and the application range covers digital television, electronics, communication and other industries. Therefore, the use of this patent can greatly improve the correct rate of the fundamental frequency processing application technology, so that the product has a better performance.

Example:

A compensation method for frequency domain signal I/Q imbalance, comprising: individually controlling an I path analog/digital converter and a Q path analog/digital converter, thereby reducing a complex filter biasing pair I The influence of the /Q imbalance; and the unequal crossover ratio of one of the complex preamble sequences in the time domain and the frequency domain, the parameter of the I/Q imbalance effect can be estimated in a frequency domain residual to the I/Q Unbalanced implementation of compensation.

2. The method of the above embodiment, wherein the complex main waves of the filters are coherent to reduce the effect of the bias of the filters on the I/Q imbalance.

3. The method of any of the preceding embodiments, wherein the step of estimating the unequal crossover ratio of the I/Q imbalance comprises: collecting a complex short preamble sequence in the time domain; and converting the short preamble sequences via a Fourier transform a virtual long preamble sequence of one of the frequency domains; and using a multiple input multiple output (MIMO) long preamble sequence and the virtual long preamble sequence to find the unequal cross ratio.

4. The method of any of the preceding embodiments, wherein the Fourier transform is a fast Fourier transform.

5. The method of any of the preceding embodiments, wherein the unequal intersection ratio is determined by the following formula:

Where C _i (k) is the unequal cross ratio, MLP _i,1 (k) is the MIMO long preamble sequence, VirtualLP _i (k) is the virtual long preamble sequence, i is the transmit antenna index, and k is a sub Carrier index, and the asterisk (*) indicates the conjugate complex function of the MIMO long preamble sequence or the virtual long preamble sequence, and -k indicates the length of the MIMO long preamble sequence plus 1-k, which is orthogonal frequency division multiplexing. The mirrored position of the data subcarriers of the symbol of the technology (OFDM).

6. A radio frequency compensation apparatus, comprising: an I/Q frequency compensation estimator connected to a multi-phase timing generator and a radio frequency receiver via a Fourier converter, and capable of receiving from a multi-input Outputting (MIMO) channel estimator data, wherein the I/Q frequency compensation estimator can estimate an I/Q imbalance parameter using a unequal cross ratio of the preamble sequence; and performing a analog/digital converter Anti-skew sampling to provide a complex digital signal stream to the I/Q frequency compensation estimator.

7. A compensation device comprising: an I/Q compensation estimator that calculates a parameter associated with an I/Q imbalance via an unequal crossover ratio to correct the I/Q imbalance. .

8. A compensation device comprising: an I/Q compensator that receives a signal and uses the ratio of a real component and an imaginary component of the signal in a frequency domain to calculate a compensation parameter .

9. The apparatus according to the above embodiment, wherein a tuning sequence is obtained by performing fast Fourier transform on the real component and the imaginary component of the signal, wherein the tuning sequence comprises a multiple input multiple output (MIMO) long preamble sequence with a virtual long preamble.

10. The apparatus according to any of the preceding embodiments, wherein the compensation parameter is that a sub-carrier is estimated to be at least one quarter of a quasi-sequence, and the ratio is not zero, and the signal is corrected by an I. /Q is not balanced.

The above is only the preferred embodiment of the present invention, and the invention is not limited thereto, and the scope of the present invention is determined by the scope of the appended patent application and its equivalent field, that is, the patent application according to the present invention Equivalent changes and modifications to the scope are intended to fall within the scope of the invention.

11. . . Wireless signal processing module

12. . . Wireless signal processing module

13. . . Wireless signal processing module

14. . . Wireless signal processing module

15. . . Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (OFDM) Modulation Demodulator

110. . . antenna

111. . . Multiplier

112. . . Multiplier

113. . . Signal oscillation generator

114. . . Has a 90 degree phase difference signal

115. . . Amplitude amplifier

116. . . Low frequency filter

117. . . Low frequency filter

118. . . I-path analog/digital converter

119. . . Q path analog/digital converter

twenty one. . . Four antennas

twenty two. . . RF processing block

twenty three. . . Multiphase clock generator

twenty four. . . Serial to parallel block

25. . . Fast Fourier transform block

26. . . Multiple input multiple output channel estimator

27. . . Frequency domain I/Q imbalance estimation compensator

28. . . Compensation information

31. . . Subcarrier of virtual long preamble sequence

32. . . Subcarrier of the original frequency domain long preamble sequence

33. . . One-quarter of the subcarriers of the original frequency domain long preamble sequence

411. . . System performance under ideal compensation

412. . . System performance with offset calibration and I/Q compensation

413. . . No offset calibration but system performance with I/Q compensation

414. . . System performance without any compensation

421. . . System performance under ideal compensation

422. . . System performance with offset calibration and I/Q compensation

423. . . No offset calibration but system performance with I/Q compensation

424. . . System performance without any compensation

Figure 1 is a schematic diagram of a frequency domain I/Q imbalance model of the present invention.

2 is a schematic diagram of a frequency domain I/Q imbalance estimation and compensation module according to the present invention.

FIG. 3 is a schematic diagram showing the position of the sub-carrier of the virtual long preamble sequence and the original frequency domain long preamble sequence in time series according to the present invention.

4a is a schematic diagram of the 802.11n multiple-input multiple-output orthogonal frequency division multiplexing technology with TGnD multipath effect system performance.

Figure 4b is a schematic diagram showing the performance of the 802.11n multiple-input multiple-output orthogonal frequency division multiplexing (OFDM) multi-path effect system.

twenty one. . . Four antenna receivers

twenty two. . . RF processing block

twenty three. . . Multiphase clock generator

twenty four. . . Serial to parallel block

25. . . Fast Fourier transform block

26. . . Multiple input multiple output channel estimator

27. . . Frequency domain I/Q imbalance estimation compensator

28. . . Compensation information

118. . . I path analog/digital converter

119. . . Q path analog/digital converter

Claims (8)

A compensation method for frequency domain dependent I/Q imbalance, comprising: individually controlling an I path analog/digital converter and a Q path analog/digital converter, thereby reducing the bias of a plurality of filters to an I/ The effect of the Q imbalance; and the unequal crossover ratio of one of the plurality of preamble sequences in the time domain and the frequency domain, the parameter of the I/Q imbalance can be estimated in a frequency domain residual to not Balancing the implementation of the compensation, wherein the step of estimating the unequal cross-ratio of the I/Q imbalance comprises: collecting a plurality of short preamble sequences in the time domain; converting the short preamble sequences to a virtual length in the frequency domain via a transposed leaf a preamble sequence; and utilizing a frequency domain multiple input multiple output (MIMO) long preamble sequence and the virtual long preamble sequence in the frequency domain to determine the unequal cross ratio. The method of claim 1, wherein the plurality of main waves of the filters are coherent to reduce the influence of the bias of the filters on the I/Q imbalance. The method of claim 1, wherein the Fourier transform is a fast Fourier transform. The method of claim 1, wherein the unequal intersection ratio is determined by the following formula: Where C _i (k) is the unequal cross ratio, MLP _i,1 (k) is the MIMO long preamble sequence, VirtualLP _i (k) is the virtual long preamble sequence, i is the transmit antenna index, and k is a sub Carrier index, and the asterisk (*) indicates the conjugate length number function of the MIMO long preamble sequence or the virtual long preamble sequence, and -k indicates the length of the MIMO long preamble sequence plus 1-k, which is orthogonal The mirror position of a plurality of data subcarriers of one symbol of frequency division multiplexing (OFDM). A radio frequency compensation apparatus includes: an I/Q frequency compensation estimator connected to a multi-phase timing generator and a radio frequency receiver via a Fourier converter, and receivable from a multiple input multiple output (MIMO) a data of a channel estimator, wherein the I/Q frequency compensation estimator can estimate a parameter of an I/Q imbalance using an unequal cross ratio, and the step of estimating the parameter of the I/Q imbalance includes: collecting a plurality of short preamble sequences in the time domain; converting the short preamble sequences to a frequency domain virtual long preamble sequence via a Fourier transform; and utilizing a frequency domain multiple input multiple output (MIMO) long preamble sequence and a frequency domain The virtual long preamble sequence is used to determine the unequal cross ratio; and an analog/digital converter performs a deskew sampling to provide a plurality of digital signal streams to the I/Q frequency compensation estimator . A compensation device includes: an I/Q compensation estimator that calculates a parameter associated with an I/Q imbalance via an unequal cross ratio to correct the I/Q imbalance, wherein the parameter is calculated The method includes: collecting a plurality of short preamble sequences in the time domain; converting the short preamble sequences to a virtual long preamble sequence in one of the frequency domains via a Fourier transform; The unequal crossover ratio is determined using a frequency domain multiple input multiple output (MIMO) long preamble sequence and the virtual long preamble sequence in the frequency domain. A compensating device can obtain a tuning sequence by performing fast Fourier transform on a real component and an imaginary component of a signal, wherein the tuning sequence includes a frequency domain multiple input multiple output (MIMO) long preamble a sequence and a frequency domain virtual long preamble, the compensation device comprising: an I/Q compensator that uses the ratio of the real component and the imaginary component of the signal in a frequency domain to calculate a compensation parameter. The device of claim 7, wherein the compensation parameter is a quasi-sequence by estimating at least one-quarter of the sub-carriers, and the ratio is not zero, and the signal is corrected by an I/ Q is not balanced.