Iteration-based SDR chip IQ calibration method and circuit

Abstract

The invention relates to an IQ calibration method and circuit for an SDR chip based on iteration. The IQ calibration method comprises the following steps: under the condition that a transmitting path and a receiving path are in a connection state, sending a calibration signal to the transmitting path according to a received I-path baseband signal and a Q-path baseband signal so as to indicate the transmitting path to perform first radio frequency processing on the calibration signal and generate a first transmitting signal, acquiring first calibration coefficients of the I-path baseband signal and the Q-path baseband signal according to the first transmitting signal; and further, under the condition that the calibration frequency does not reach a preset iteration threshold value, performing first calibration processing on the received I-path baseband signal and Q-path baseband signal according to the first calibration coefficient so as to update the calibration signal, and re-executing the step of sending the calibration signal to the transmitting path until the calibration frequency reaches the preset iteration threshold value. The accuracy of the finally obtained first calibration coefficient can be improved through multiple times of iterative processing, so that the IQ image rejection ratio of a transmitting path can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of radio frequency transceivers, and in particular to an iterative SDR chip IQ calibration method and circuit. Background Art

[0002] With the development of chip integration technology, it has become possible to integrate various electronic components previously required for zero-IF receivers, such as low-noise amplifiers, mixers, power amplifiers, filters, attenuators, digital-to-analog converters, and digital filters, into a single-chip SDR (software defined radio) chip to form a complex SDR chip.

[0003] For SDR transceivers, orthogonal modulation technology is usually used to achieve signal modulation and demodulation. Among them, the signals of the orthogonal channel and the in-phase channel may have phase or amplitude imbalance problems, which is called IQ imbalance. IQ imbalance will cause image interference in the transmitted and received signals, reduce the static range, and seriously affect the demodulation of the baseband signal. Summary of the invention

[0004] Based on this, it is necessary to provide an iterative SDR chip IQ calibration method and circuit.

[0005] In a first aspect, the present application provides an IQ calibration method, which is applied to an IQ calibration circuit in a radio frequency system, wherein the radio frequency system further includes a transmitting path and a receiving path; the method includes:

[0006] When the transmitting path and the receiving path are in a connected state, a calibration signal is sent to the transmitting path according to the received I-path baseband signal and Q-path baseband signal to instruct the transmitting path to perform a first radio frequency processing on the calibration signal and generate a first transmitting signal;

[0007] Acquire a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to the first transmit signal;

[0008] When the number of calibration times does not reach the preset iteration threshold, a first calibration process is performed on the received I-channel baseband signal and Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the step of sending the calibration signal to the transmission path is re-executed until the number of calibration times reaches the preset iteration threshold.

[0009] In one embodiment, the acquiring, according to the first transmit signal, first calibration coefficients of an I-channel baseband signal and a Q-channel baseband signal includes:

[0010] Acquire a corresponding first received signal according to the first transmitted signal;

[0011] Determine an imbalance parameter of the I-channel baseband signal and the Q-channel baseband signal according to the first received signal;

[0012] determining a compensation coefficient according to the imbalance parameter;

[0013] The first calibration coefficient is determined according to the compensation coefficient.

[0014] In one embodiment, acquiring a corresponding first received signal according to the first transmitted signal includes:

[0015] Acquire a second received signal corresponding to the first transmitted signal;

[0016] A second calibration process is performed on the second received signal according to a pre-stored second calibration coefficient to obtain the first received signal.

[0017] In one embodiment, the radio frequency system further includes a signal source; and the method further includes:

[0018] Acquire target calibration conditions for an I-channel baseband signal and a Q-channel baseband signal; the target calibration conditions include at least one of a target frequency band and a target transmission gain of the baseband signal;

[0019] When the target calibration condition includes the target frequency band, controlling the signal source to generate an I-channel baseband signal and a Q-channel baseband signal within the target frequency band;

[0020] In a case where the target calibration condition includes the target transmit gain, a gain control instruction is sent to the transmit path to instruct the transmit path to perform a first radio frequency processing on the I baseband signal and the Q baseband signal at the target transmit gain.

[0021] In one embodiment, controlling the signal source to generate an I-channel baseband signal and a Q-channel baseband signal within the target frequency band includes:

[0022] Determine a preset number of calibration frequencies within the target frequency band, each calibration frequency is different and the frequency difference between any two adjacent calibration frequencies is the same;

[0023] The signal source is controlled to generate an I-channel baseband signal and a Q-channel baseband signal corresponding to each of the calibration frequencies.

[0024] In one embodiment, the method further comprises:

[0025] When the transmitting path and the receiving path are in a disconnected state, obtaining a third receiving signal corresponding to the radio frequency signal;

[0026] A second calibration coefficient corresponding to the radio frequency signal is obtained according to the third received signal.

[0027] In a second aspect, the present application further provides an IQ calibration circuit, which is applied to a radio frequency system, and the IQ calibration circuit includes:

[0028] a transmission processing module, configured to send a calibration signal to the transmission path according to the received I-path baseband signal and Q-path baseband signal when the transmission path and the reception path are in a connected state, so as to instruct the transmission path to perform a first radio frequency processing on the calibration signal and generate a first transmission signal;

[0029] A calibration processing module is used to obtain a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to the first transmission signal; when the number of calibrations does not reach a preset iteration threshold, a first calibration process is performed on the received I-channel baseband signal and the Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the transmission processing module is controlled to resend the calibration signal to the transmission path until the number of calibrations reaches a preset iteration threshold.

[0030] In one embodiment, the calibration coefficient includes a plurality of sub-calibration coefficients of different levels; the transmission processing module includes:

[0031] A transmission complex filter connected to the transmission path, and configured to send the calibration signal to the transmission path according to the received I-path baseband signal and Q-path baseband signal;

[0032] The transmit complex filter comprises a plurality of transmit sub-filters, each of which comprises a plurality of cascaded transmit filter units, each of which comprises at least two delay devices and a multiplier connected in series, wherein the output ends of the two delay devices connected in series are connected to the input end of the multiplier;

[0033] The i-th level delay device is used to perform delay processing on the received i-1-th level signal, and the i-th level multiplier is used to perform multiplication processing on the i-th level sub-calibration coefficient and the signal delayed by the i-th level delay device.

[0034] In a third aspect, the present application also provides a radio frequency system, including:

[0035] A transmitting path, used for receiving a calibration signal and performing a first radio frequency processing on the calibration signal to generate a first transmitting signal;

[0036] A receiving path, used for performing a second radio frequency processing on the first transmission signal;

[0037] The IQ calibration circuit is used to send a calibration signal to the transmitting path according to the received I-path baseband signal and Q-path baseband signal when the transmitting path and the receiving path are in a connected state; obtain a first calibration coefficient of the I-path baseband signal and the Q-path baseband signal according to the first transmitting signal; and perform a first calibration process on the received I-path baseband signal and the Q-path baseband signal according to the first calibration coefficient to update the calibration signal when the number of calibrations does not reach a preset iteration threshold, and re-execute the step of sending the calibration signal to the transmitting path until the number of calibrations reaches the preset iteration threshold.

[0038] In a fourth aspect, the present application also provides an SDR chip, comprising a radio frequency system as provided in any of the above embodiments.

[0039] In the above-mentioned iteration-based SDR chip IQ calibration method and circuit, when the transmission path and the receiving path are in a connected state, according to the received I-channel baseband signal and Q-channel baseband signal, a calibration signal is sent to the transmission path to instruct the transmission path to perform a first RF processing on the calibration signal, and generate a first transmission signal, and obtain the first calibration coefficient of the I-channel baseband signal and the Q-channel baseband signal according to the first transmission signal; further, when the number of calibrations does not reach the preset iteration threshold, the first calibration processing is performed on the received I-channel baseband signal and the Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the step of sending the calibration signal to the transmission path is re-executed until the number of calibrations reaches the preset iteration threshold. It can be understood that the accuracy of the first calibration coefficient finally obtained can be improved by multiple iterations. The first calibration coefficient obtained by multiple iterations is used to perform pre-distortion compensation on the I-channel baseband signal and the Q-channel baseband signal of the transmission path during the normal operation of the RF system, which can improve the image suppression ratio of the transmission path. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 is a structural block diagram of a radio frequency system according to an embodiment;

[0042] Figure 2 A flow chart of a signal calibration method provided by an embodiment;

[0043] Figure 3A flowchart of obtaining a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to a first transmit signal provided by an embodiment;

[0044] Figure 4 A compensation model provided for an embodiment;

[0045] Figure 5 A flowchart of an IQ calibration method provided by another embodiment;

[0046] Figure 6 A flowchart for calibrating a receiving path provided in a specific embodiment;

[0047] Figure 7 A structural block diagram of calibrating a receiving path provided in a specific embodiment;

[0048] Figure 8 A flowchart for calibrating a transmission path provided in a specific embodiment;

[0049] Fig. 9 A comparison diagram of the IQ image suppression ratio of a transmission path before and after calibration provided by an embodiment;

[0050] Fig.10 A comparison diagram of the IQ image suppression ratio of a transmission path after calibration twice and before calibration provided by an embodiment;

[0051] Fig.11 A comparison diagram of the IQ image suppression ratio of a transmission path before and after calibration provided by an embodiment;

[0052] Fig.12 A structural block diagram of an IQ calibration circuit provided by an embodiment;

[0053] Fig.13 An internal block diagram of a transmit complex filter provided by an embodiment;

[0054] Fig.14 A digital block diagram of a transmit sub-filter provided by an embodiment;

[0055] Fig.15 A schematic diagram of calculating a sub-calibration coefficient from a compensation coefficient B provided by an embodiment;

[0056] Fig.16 A schematic diagram of calculating a sub-calibration coefficient from a compensation coefficient C provided by an embodiment. DETAILED DESCRIPTION

[0057] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0059] It can be understood that the terms "first", "second", etc. used in this application can be used in this article to describe various data, but these data are not limited by these terms. These terms are only used to distinguish the first data from another data.

[0060] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0061] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0062] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0063] The signal calibration method provided in this application can be applied to Figure 1The radio frequency system includes a signal source, an IQ calibration circuit, a transmitting path and a receiving path (the signal source is not shown), and the IQ calibration circuit is connected to the transmitting path, the receiving path and the signal source respectively. Among them, the transmitting path includes an I transmitting path, a Q transmitting path and a power amplifier (PPA), wherein the I transmitting path and the Q transmitting path respectively include a first FIR filter, a multi-stage interpolation filter (HB2, HB3), a digital-to-analog conversion circuit (DAC), a first low-pass filter and an up-conversion mixer connected in series in sequence. The receiving path includes a low noise filter (LNA), an I receiving path and a Q receiving path. The I receiving path and the Q receiving path respectively include a down-conversion mixer, a second low-pass filter, an analog-to-digital conversion circuit (ADC), a multi-stage extraction filter (HB2, HB3) and a second FIR filter connected in series in sequence. The signal source can be a standard digital signal generator (NCO).

[0064] In one embodiment, Figure 2 As shown, the present application provides an IQ calibration method, including steps 202 to 206.

[0065] Step 202: When the transmitting path and the receiving path are in a connected state, a calibration signal is sent to the transmitting path according to the received I-path baseband signal and Q-path baseband signal to instruct the transmitting path to perform a first RF processing on the calibration signal and generate a first transmitting signal.

[0066] The I-channel baseband signal and the Q-channel baseband signal may be generated by a signal source. The calibration signal is a signal sent by the IQ calibration circuit to the transmission path.

[0067] It can be understood that when the transmitting path and the receiving path are in a connected state, the IQ calibration circuit sends a calibration signal to the transmitting path according to the received I-path baseband signal and Q-path baseband signal. After the transmitting path receives the calibration signal, the calibration signal is subjected to a first RF processing and a first transmitting signal is generated. The first RF processing includes filtering, interpolation, digital-to-analog conversion, and up-conversion mixing of the calibration signal. The first transmitting signal is a RF signal.

[0068] Step 204: Acquire first calibration coefficients of the I-channel baseband signal and the Q-channel baseband signal according to the first transmit signal.

[0069] The first calibration coefficient is used to implement predistortion compensation for an I-channel baseband signal and a Q-channel baseband signal in a transmission path.

[0070] Step 206, when the number of calibration times does not reach the preset iteration threshold, a first calibration process is performed on the received I-channel baseband signal and Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the step of sending the calibration signal to the transmission path is re-executed until the number of calibration times reaches the preset iteration threshold.

[0071] The number of calibrations is the number of times the first compensation coefficient is obtained. For example, the preset iteration threshold may be greater than or equal to 2.

[0072] When the number of calibrations does not reach the preset iteration threshold, the IQ calibration circuit may perform a first calibration process on the received I-channel baseband signal and Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and send the new calibration signal to the transmission path to obtain a new first calibration coefficient. Wherein, when the number of calibrations is 0, the calibration signal is the I-channel baseband signal and the Q-channel baseband signal; when the calibration signal is greater than 0, the calibration signal is a signal after the I-channel baseband signal and the Q-channel baseband signal are subjected to the first calibration process according to the first calibration coefficient that has been obtained.

[0073] In this embodiment, when the transmitting path and the receiving path are in a connected state, a calibration signal is sent to the transmitting path according to the received I-path baseband signal and Q-path baseband signal to instruct the transmitting path to perform a first RF processing on the calibration signal and generate a first transmitting signal, and a first calibration coefficient of the I-path baseband signal and the Q-path baseband signal is obtained according to the first transmitting signal; further, when the number of calibrations does not reach a preset iteration threshold, the first calibration processing is performed on the received I-path baseband signal and the Q-path baseband signal according to the first calibration coefficient to update the calibration signal, and the step of sending the calibration signal to the transmitting path is re-executed until the number of calibrations reaches the preset iteration threshold. It can be understood that the accuracy of the first calibration coefficient finally obtained can be improved by multiple iterations. The first calibration coefficient obtained by multiple iterations is used to perform pre-distortion compensation on the I-path baseband signal and the Q-path baseband signal of the transmitting path during the normal operation of the RF system, so as to improve the image suppression ratio of the transmitting path.

[0074] In one embodiment, Figure 3 As shown, obtaining the first calibration coefficients of the I-channel baseband signal and the Q-channel baseband signal according to the first transmit signal includes steps 302 to 308.

[0075] Step 302: Acquire a corresponding first received signal according to the first transmitted signal.

[0076] Specifically, step 302 may include the steps of acquiring a second received signal corresponding to the first transmitted signal, performing a second calibration process on the second received signal according to a pre-stored second calibration coefficient, and acquiring the first received signal.

[0077] The second received signal is an IQ signal obtained after down-conversion mixing, low-pass filtering, analog-to-digital conversion and extraction in the receiving path. The second calibration coefficient is used to implement IQ imbalance calibration in the receiving path. The first received signal includes an I-path signal and a Q-path signal.

[0078] It can be understood that the second calibration processing is performed on the second received signal through the pre-stored second calibration coefficient to obtain the first received signal, complete the calibration of the IQ imbalance of the receiving path, and basically eliminate the influence of the IQ imbalance of the receiving path on the calculation of the imbalance parameters of the transmitting path and the first calibration coefficient, thereby improving the accuracy of the first calibration coefficient subsequently obtained based on the first received signal.

[0079] Step 304: determine the imbalance parameters of the I-channel baseband signal and the Q-channel baseband signal according to the first received signal.

[0080] The imbalance parameter includes an amplitude imbalance value and a phase imbalance value. Assuming that the I-path signal in the first received signal is taken as a reference, the I-path signal is expressed as , the Q-path signal can be expressed as .in, Indicates the amplitude imbalance value of the Q-channel signal relative to the I-channel signal. Indicates the phase imbalance value of the Q-path signal relative to the I-path signal.

[0081] The I-channel signal and the Q-channel signal in the first received signal can be synchronously analyzed to obtain and The value of .

[0082] Step 306: determining a compensation coefficient according to the unbalance parameter.

[0083] The compensation coefficients B and C represent the compensation values ​​required to supplement the Q channel signal into a standard sinusoidal signal. Figure 4 The compensation model, the compensation coefficient B can be expressed as:

[0084] The compensation coefficient C can be expressed as:

[0085] The values ​​of the compensation coefficients B and C can be calculated based on the above formula (1) and formula (2) according to the amplitude imbalance value and the phase imbalance value.

[0086] Step 308: Determine a first calibration coefficient according to the compensation coefficient.

[0087] The first calibration coefficient can be obtained by performing inverse fast Fourier transform processing and reverse processing on the compensation coefficient.

[0088] It should be noted that when the imbalance calibration of the transmission path is performed, an iterative processing method is adopted. Each iterative processing will generate a new imbalance parameter. Assuming that the preset iteration threshold is m, the imbalance parameter of the nth iterative processing is and , the corresponding compensation coefficients are Bn and Cn.

[0089] Then the following relationship will exist:

[0090]

[0091]

[0092]

[0093]

[0094] After performing inverse fast Fourier transform and inverse processing on the compensation coefficients Bm and Cm, the final first calibration coefficient can be obtained.

[0095] Using the first calibration coefficient obtained by this iterative processing to perform the first calibration process on the IQ channel will significantly improve the IQ image suppression ratio of the transmission path. The applicant has conducted experiments and found that after using the first calibration coefficient obtained by iterative processing to compensate the baseband signal of the IQ channel, the IQ image suppression ratio can be increased to 70dB.

[0096] In addition, since the correction value of the phase imbalance in the imbalance calibration in the IQ channel is usually very small, in some embodiments, the compensation coefficient B1 obtained for the first time can be used as the final compensation coefficient Bm.

[0097] In one embodiment, the IQ calibration method also includes the steps of obtaining target calibration conditions for the I-channel baseband signal and the Q-channel baseband signal; when the target calibration conditions include a target frequency band, controlling the signal source to generate the I-channel baseband signal and the Q-channel baseband signal within the target frequency band; and when the target calibration conditions include a target transmit gain, sending a gain control instruction to the transmit path to instruct the transmit path to perform a first RF processing on the I-channel baseband signal and the Q-channel baseband signal with the target transmit gain.

[0098] The target calibration condition includes at least one of a target frequency band and a target transmission gain of a baseband signal.

[0099] It is understood that in order to achieve full range calibration, the calibration conditions can be changed and multiple emission calibrations can be performed. The calibration conditions include a combination of different frequency bands and different emission gains. In some embodiments, the calibration conditions can also include a combination of different temperatures.

[0100] For example, Figure 5As shown, when calibrating the transmission path, the target temperature, target frequency band and target transmission gain can be determined in sequence, the signal source can be controlled to generate the I-channel baseband signal and the Q-channel baseband signal within the target frequency band, and then the above steps 202 to 206 are performed to obtain the first calibration coefficient and store the first calibration coefficient in the memory. Then, the calibration of the next combination of temperature, frequency band and transmission gain is performed until the calibration of all calibration conditions is completed.

[0101] In one embodiment, controlling a signal source to generate an I-channel baseband signal and a Q-channel baseband signal within a target frequency band includes determining a preset number of calibration frequencies within the target frequency band, wherein each calibration frequency is different and the frequency difference between any two adjacent calibration frequencies is the same; and controlling the signal source to generate an I-channel baseband signal and a Q-channel baseband signal corresponding to each calibration frequency.

[0102] According to the differential concept, a broadband signal is formed by superposition of sufficiently narrowband signals. For narrowband signals, it can be considered that their IQ imbalance parameters are constant and independent of frequency. Therefore, a preset number of calibration frequencies in the target frequency band can be determined first. The frequency difference between adjacent calibration frequencies is the length of the target frequency band divided by the preset number, and the signal source is controlled to generate the I-channel baseband signal and the Q-channel baseband signal corresponding to each calibration frequency. Then, the first receiving signal corresponding to each calibration frequency is obtained through the receiving path, and multiple first calibration coefficients are calculated based on the multiple first receiving signals. Among them, the preset number is the same as the number of stages of the complex filter in the IQ calibration circuit.

[0103] In one embodiment, the IQ calibration method of the present application also includes calibration of a receiving path, specifically, including the steps of obtaining a third receiving signal corresponding to the RF signal when the transmitting path and the receiving path are in a disconnected state, and obtaining a second calibration coefficient corresponding to the RF signal based on the third receiving signal.

[0104] When the transmitting path and the receiving path are disconnected, the path between the receiving path and the calibration PLL can be connected, and the calibration PLL (phase-locked loop) provides the receiving path with an RF signal. The receiving path sequentially processes the RF signal through down-conversion mixing, low-pass filtering, analog-to-digital conversion, and extraction to generate a third receiving signal.

[0105] Further, based on the same process as steps 304 to 308 above, the amplitude imbalance value and phase imbalance value of the I-path signal and the Q-path signal in the third received signal are first obtained, and the compensation coefficients B and C are calculated according to the amplitude imbalance value and the phase imbalance value, and then the second calibration coefficient is obtained based on the compensation coefficients B and C.

[0106] When performing imbalance calibration on the receiving path, it is not necessary to perform iterative processing, and the second calibration coefficient obtained for the first time can be directly used as the second calibration coefficient finally used, which can reduce the calculation complexity of the IQ calibration circuit.

[0107] In order to more clearly illustrate the IQ calibration method of the present application, a more specific embodiment is listed below.

[0108] The IQ calibration method of the present application can be divided into the calibration of the receiving path and the calibration of the transmitting path. Since the acquisition of the first calibration coefficient of the transmitting path depends on the I-path signal and the Q-path signal in the receiving path, it is necessary to calibrate the receiving path before calibrating the transmitting path. Assuming that the target frequency band is fL~fL+100Mhz, the order of the complex filter in the IQ calibration circuit is 128 orders, and the frequency midpoint fL+50Mhz of the target frequency band is used as the frequency of the local oscillator signal.

[0109] like Figure 6 and Figure 7 As shown, first calibrate the receiving path:

[0110] Step 602, controlling the transmission path and the reception path to be disconnected, and controlling the reception path to be connected to the calibration PLL;

[0111] Step 604, control the calibration PLL to first generate a radio frequency signal with a frequency of 2fL+50Mhz, and control the receiving PLL in the receiving path to generate a local oscillator signal with a frequency of fL+50Mhz;

[0112] Step 606, obtaining a third receiving signal generated by sequentially performing down-conversion mixing processing, low-pass filtering processing, analog-to-digital conversion processing and decimation processing on the radio frequency signal in the receiving path;

[0113] Step 608, obtaining an imbalance parameter between the I-path signal and the Q-path signal in the third received signal;

[0114] Step 610, calculating a compensation coefficient corresponding to a first calibration frequency according to the imbalance parameter;

[0115] Step 612, control the calibration PLL to generate a radio frequency signal with a frequency of the previous frequency + 100M / 128, and obtain the compensation coefficient corresponding to the current calibration frequency. Repeat this step 127 times to finally obtain the compensation coefficients corresponding to 128 frequencies;

[0116] Step 614: Perform inverse fast Fourier transform and inverse processing on the compensation coefficients corresponding to the 128 frequencies to obtain 128 second calibration coefficients of the receiving complex filter in the IQ calibration circuit.

[0117] Then as Figure 8 and Figure 1 As shown, the transmit path is calibrated:

[0118] Step 802, controlling the connection between the transmitting path and the receiving path, and controlling the connection between the signal source and the transmitting path;

[0119] Step 804, control the signal source to generate an I-channel baseband signal and a Q-channel baseband signal with a calibration frequency of fL, and control the transmit PLL in the transmit path and the receive PLL in the receive path to generate local oscillator signals with a frequency of fL+50Mhz respectively;

[0120] Step 806, obtaining a second receiving signal in the receiving path;

[0121] Step 808, using Figure 6 Performing a second calibration process on the second received signal using the acquired second compensation coefficient to obtain a first received signal;

[0122] Step 810, obtaining an imbalance parameter between an I-path signal and a Q-path signal in a first received signal;

[0123] Step 812, calculating a compensation coefficient corresponding to the first calibration frequency according to the imbalance parameter;

[0124] Step 814, control the signal source to generate an I-channel baseband signal and a Q-channel baseband signal with a calibration frequency of the previous calibration frequency + 100M / 128, obtain the compensation coefficient corresponding to the current calibration frequency, repeat this step 127 times, and obtain the compensation coefficients corresponding to 128 calibration frequencies;

[0125] Step 816, obtaining a 128th-order first calibration coefficient corresponding to the transmit complex filter in the IQ calibration circuit according to the compensation coefficients corresponding to the 128 calibration frequencies, and adding 1 to the value of the calibration times;

[0126] Step 820, determine whether the number of calibration times reaches the preset iteration threshold. If not, control the signal source again to generate an I-channel baseband signal and a Q-channel baseband signal with a calibration frequency of fL, and use the first calibration coefficient that has been obtained to perform a first calibration process on the I-channel baseband signal and the Q-channel baseband signal to generate a calibration signal. Repeat the above steps 806-820 until the number of calibration times reaches the preset iteration threshold.

[0127] Step 822: Calculate and store the first calibration coefficients that are finally required based on the 128 compensation coefficients obtained in the last iteration.

[0128] Figure 9-11 The following are comparison diagrams of the IQ image suppression ratio of the transmit path obtained after compensating the IQ baseband signal according to the first calibration coefficient obtained after calibration 1, calibration 2, and calibration 3, respectively, and the IQ image suppression ratio before calibration. Figure 9-12It can be seen that after two calibrations (i.e. one iteration), the IQ image suppression ratio of the transmit path can be increased to 70 dB.

[0129] In one embodiment, Fig.12 As shown, the present application also provides an IQ calibration circuit, including a transmission processing module 1202 and a calibration processing module 1204.

[0130] The transmission processing module 1202 is connected to the transmission path 1206, and can be used to send a calibration signal to the transmission path 1206 according to the received I-path baseband signal and Q-path baseband signal when the transmission path 1206 and the receiving path 1208 are in a connected state, so as to instruct the transmission path 1206 to perform a first RF processing on the calibration signal and generate a first transmission signal.

[0131] The calibration processing module 1204 is respectively connected to the transmission processing module 1202 and the receiving path 1208, and can be used to obtain a first calibration coefficient of the I-path baseband signal and the Q-path baseband signal according to the first transmission signal; when the number of calibrations does not reach the preset iteration threshold, the first calibration processing is performed on the received I-path baseband signal and the Q-path baseband signal according to the first calibration coefficient to update the calibration signal, and the transmission processing module 1202 is controlled to resend the calibration signal to the transmission path 1206 until the number of calibrations reaches the preset iteration threshold.

[0132] The specific description of the functions of the transmission processing module 1202 and the calibration processing module 1204 has been described in steps 202 to 206 and will not be repeated here.

[0133] Furthermore, in one embodiment, the transmission processing module includes a transmission complex filter. The transmission complex filter is connected to the transmission path and is used to send a calibration signal to the transmission path according to the received I-path baseband signal and Q-path baseband signal.

[0134] The transmit complex filter includes a plurality of transmit sub-filters. Specifically, as mentioned above, the compensation coefficient includes a compensation coefficient B and a compensation coefficient C. Accordingly, the transmit complex filter includes four transmit sub-filters, namely, a BHI filter, a BHQ filter, a CHI filter, and a CHQ filter. Fig.13 As shown, the inputs of the BHI filter and the BHQ filter are the I-channel baseband signal, the inputs of the CHI filter and the CHQ filter are the Q-channel baseband signal, the outputs of the BHI filter and the CHI filter are added to obtain the calibrated Q-channel baseband signal, and the outputs of the BHQ filter and the CHQ filter are added to obtain the calibrated I-channel baseband signal.

[0135] The transmit sub-filter can be implemented using a systolic Multiply-Accumulate structure. Fig.14 As shown, each transmit sub-filter includes a plurality of cascaded transmit filter units ( Fig.14 In the embodiment of the present invention, each transmit filter unit includes at least two delay devices and multipliers connected in series, wherein the output ends of the two delay devices connected in series are connected to the input ends of the multiplier. The i-th level delay device is used to delay the received i-1-th level signal, and the i-th level multiplier is used to multiply the i-th level sub-calibration coefficient and the signal delayed by the i-th level delay device. The calibration coefficient includes a plurality of sub-calibration coefficients of different levels, and the sub-calibration coefficients are expressed as coefficients of each level of filter unit in the transmit sub-filter.

[0136] It can be understood that the output-input relationship of each transmit sub-filter can be expressed as:

[0137]

[0138] in, represents the i-th sub-calibration coefficient, k represents the total number of transmit sub-filters, and X(i) represents the baseband signal.

[0139] In addition, each filter unit uses two delay devices connected in series, which can support high-performance compensation for large amounts of data.

[0140] In one embodiment, the calibration processing module includes a calibration coefficient determination unit and an iteration unit.

[0141] The calibration coefficient determination unit may be used to obtain a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to a first transmission signal. Specifically, the calibration coefficient determination unit may first obtain a corresponding first received signal according to the first transmission signal, determine an imbalance parameter of the I-channel baseband signal and the Q-channel baseband signal according to the first received signal, determine a compensation coefficient according to the imbalance parameter, and determine a first calibration coefficient according to the compensation coefficient.

[0142] Among them, for Fig.13 In the framework of the transmit complex filter shown in FIG. 1 , the I-channel baseband signal includes k I-channel baseband signals of different frequencies, and the Q-channel baseband signal includes k Q-channel baseband signals of different frequencies. Correspondingly, the calibration coefficient determination unit can obtain k compensation coefficients B (BF1 to BFk) and k compensation coefficients C (CF1 to CFk). Fig.15 As shown, the calibration coefficient determination unit can perform inverse fast Fourier transform on the k compensation coefficients B (BF1~BFk) to obtain k real data BI1~BIk and k imaginary data BQ1~BQk. The k real data BI1~BIk are processed in reverse order to obtain k sub-calibration coefficients BHI1~BHIk of the BHI filter. The k imaginary data are processed in reverse order to obtain k sub-calibration coefficients BHQ1~BHQk of the BHQ filter.

[0143] Similarly, if Fig.16 As shown, the calibration coefficient determination unit can perform inverse fast Fourier transform on the k compensation coefficients C (CF1~CFk) to obtain k real data CI1~CIk and k imaginary data CQ1~CQk. By reversing the k real data CI, k sub-calibration coefficients CHI1~CHIk of the CHI filter are obtained. By reversing the k imaginary data, k sub-calibration coefficients CHQ1~CHQk of the CHQ filter are obtained.

[0144] The iteration unit is used to perform a first calibration process on the received I-channel baseband signal and Q-channel baseband signal according to a first calibration coefficient to update the calibration signal when the calibration number does not reach a preset iteration threshold, and control the transmission processing module to resend the calibration signal to the transmission path until the calibration number reaches the preset iteration threshold.

[0145] For a detailed description of the function of the iteration unit, please refer to the above definition of step 206, which will not be repeated here.

[0146] In one embodiment, the IQ calibration circuit further includes a receiving processing module. The receiving processing module is connected to the receiving path and the calibration processing module respectively, and the receiving processing module can be used to perform a second calibration process on the second receiving signal according to a pre-stored second calibration coefficient to obtain the first receiving signal.

[0147] The receiving processing module includes a receiving complex filter. The framework of the receiving complex filter is the same as that of the transmitting complex filter, including a BHI filter, a BHQ filter, a CHI filter, and a CHQ filter. The definition of the receiving complex filter refers to the above-mentioned definition of the transmitting complex filter.

[0148] In one embodiment, the IQ calibration circuit further includes a storage module. The storage module is respectively connected to the calibration processing module, the transmission processing module, and the reception processing module, and is used to store the first calibration coefficient and the second calibration coefficient corresponding to each target frequency band. After completing the calibration of the transmission path and the reception path, during the normal operation of the radio frequency system, the first calibration coefficient and the second calibration coefficient corresponding to the signal frequency band can be directly called from the storage module.

[0149] Based on the same inventive concept, the embodiment of the present application also provides a radio frequency system for implementing the above-mentioned IQ calibration method. The implementation scheme for solving the problem provided by the radio frequency system is similar to the implementation scheme recorded in the above-mentioned method, so the specific limitations in one or more radio frequency system embodiments provided below can refer to the above-mentioned limitations on the IQ calibration method, which will not be repeated here.

[0150] In one embodiment, Figure 1As shown, the present application also provides a radio frequency system, including a transmitting path, a receiving path and an IQ calibration circuit.

[0151] The transmitting path is used to receive a calibration signal and perform a first radio frequency processing on the calibration signal to generate a first transmitting signal.

[0152] The receiving path is used to perform second radio frequency processing on the first transmitting signal.

[0153] The IQ calibration circuit is used to send a calibration signal to the transmission path according to the received I-path baseband signal and Q-path baseband signal when the transmission path and the receiving path are in a connected state; obtain a first calibration coefficient of the I-path baseband signal and the Q-path baseband signal according to the first transmission signal; and perform a first calibration process on the received I-path baseband signal and the Q-path baseband signal according to the first calibration coefficient to update the calibration signal when the number of calibrations does not reach a preset iteration threshold, and re-execute the step of sending the calibration signal to the transmission path until the number of calibrations reaches the preset iteration threshold.

[0154] In this embodiment, the IQ calibration circuit sends a calibration signal to the transmitting path according to the received I-path baseband signal and Q-path baseband signal when the transmitting path and the receiving path are in a connected state, so as to instruct the transmitting path to perform a first RF processing on the calibration signal and generate a first transmitting signal, and obtain the first calibration coefficient of the I-path baseband signal and the Q-path baseband signal according to the first transmitting signal, and improve the accuracy of the first calibration coefficient finally obtained by iteratively obtaining the first calibration coefficient. During the normal operation of the RF system, the I-path baseband signal and the Q-path baseband signal of the transmitting path are pre-distorted and compensated by using the first calibration coefficient, so as to improve the image suppression ratio of the transmitting path.

[0155] In one embodiment, the IQ calibration circuit is also used to obtain a corresponding first received signal based on the first transmitted signal; determine the imbalance parameters of the I-channel baseband signal and the Q-channel baseband signal based on the first received signal; determine the compensation coefficient based on the imbalance parameter; and determine the first calibration coefficient based on the compensation coefficient.

[0156] In one embodiment, the IQ calibration circuit is further used to obtain a second received signal corresponding to the first transmitted signal; and perform a second calibration process on the second received signal according to a pre-stored second calibration coefficient to obtain the first received signal.

[0157] In one embodiment, the radio frequency system further includes a signal source.

[0158] The IQ calibration circuit is also used to obtain target calibration conditions for the I-channel baseband signal and the Q-channel baseband signal; the target calibration conditions include at least one of a target frequency band and a target transmission gain of the baseband signal; when the target calibration conditions include the target frequency band, the signal source is controlled to generate the I-channel baseband signal and the Q-channel baseband signal within the target frequency band; when the target calibration conditions include the target transmission gain, a gain control instruction is sent to the transmission path to instruct the transmission path to perform a first RF processing on the I-channel baseband signal and the Q-channel baseband signal with the target transmission gain.

[0159] In one embodiment, the IQ calibration circuit is also used to determine a preset number of calibration frequencies within the target frequency band, each calibration frequency is different and the frequency difference between any two adjacent calibration frequencies is the same; the control signal source generates an I-channel baseband signal and a Q-channel baseband signal corresponding to each calibration frequency.

[0160] In one embodiment, the IQ calibration circuit is further used to obtain a third received signal corresponding to the RF signal when the transmit path and the receive path are in a disconnected state; and obtain a second calibration coefficient corresponding to the RF signal according to the third received signal.

[0161] The embodiment of the present application also provides an SDR chip for implementing the above-mentioned IQ calibration method. The implementation solution provided by the SDR chip to solve the problem is similar to the implementation solution recorded in the above-mentioned method, so the specific limitations in one or more SDR chip embodiments provided below can refer to the limitations on the signal calibration method above, and will not be repeated here.

[0162] In one embodiment, the present application further provides an SDR chip, comprising the radio frequency system provided in any of the above embodiments.

[0163] By integrating a radio frequency system with a high IQ image rejection ratio on the SDR chip, the transceiver performance of the SDR chip is improved.

[0164] In an exemplary embodiment, a controller is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the IQ calibration method provided in any of the above embodiments is implemented.

[0165] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the IQ calibration method provided in any of the above embodiments is implemented.

[0166] In one embodiment, a computer program product is provided, including a computer program. When the computer program is executed by a processor, the IQ calibration method provided in any of the above embodiments is implemented.

[0167] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0168] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0169] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An IQ calibration method, characterized in that: An IQ calibration circuit applied to a radio frequency system, wherein the radio frequency system further comprises a transmitting path and a receiving path; the method comprises: When the transmitting path and the receiving path are in a connected state, a calibration signal is sent to the transmitting path according to the received I-path baseband signal and Q-path baseband signal to instruct the transmitting path to perform a first radio frequency processing on the calibration signal and generate a first transmitting signal; Acquire a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to the first transmit signal; When the number of calibration times does not reach the preset iteration threshold, a first calibration process is performed on the received I-channel baseband signal and Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the step of sending the calibration signal to the transmission path is re-executed until the number of calibration times reaches the preset iteration threshold.

2. The method according to claim 1, characterized in that The acquiring, according to the first transmit signal, a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal comprises: Acquire a corresponding first received signal according to the first transmitted signal; Determining an imbalance parameter of the I-channel baseband signal and the Q-channel baseband signal according to the first received signal; determining a compensation coefficient according to the imbalance parameter; The first calibration coefficient is determined according to the compensation coefficient.

3. The method according to claim 2, characterized in that The acquiring a corresponding first received signal according to the first transmitted signal includes: Acquire a second received signal corresponding to the first transmitted signal; Perform a second calibration process on the second received signal according to a pre-stored second calibration coefficient to obtain the first received signal.

4. The method according to claim 1, characterized in that: The radio frequency system further includes a signal source; the method further includes: Acquire target calibration conditions for an I-channel baseband signal and a Q-channel baseband signal; the target calibration conditions include at least one of a target frequency band and a target transmission gain of the baseband signal; When the target calibration condition includes the target frequency band, controlling the signal source to generate an I-channel baseband signal and a Q-channel baseband signal within the target frequency band; In a case where the target calibration condition includes the target transmit gain, a gain control instruction is sent to the transmit path to instruct the transmit path to perform a first radio frequency processing on the I baseband signal and the Q baseband signal at the target transmit gain.

5. The method according to claim 4, characterized in that The controlling the signal source to generate an I-channel baseband signal and a Q-channel baseband signal within the target frequency band includes: Determine a preset number of calibration frequencies within the target frequency band, each calibration frequency is different and the frequency difference between any two adjacent calibration frequencies is the same; The signal source is controlled to generate an I-channel baseband signal and a Q-channel baseband signal corresponding to each of the calibration frequencies.

6. The method according to claim 1, characterized in that The method further comprises: When the transmitting path and the receiving path are in a disconnected state, obtaining a third receiving signal corresponding to the radio frequency signal; A second calibration coefficient corresponding to the radio frequency signal is obtained according to the third received signal.

7. An IQ calibration circuit, characterized in that: Applied to a radio frequency system, the IQ calibration circuit comprises: a transmission processing module, configured to send a calibration signal to the transmission path according to the received I-path baseband signal and Q-path baseband signal when the transmission path and the reception path are in a connected state, so as to instruct the transmission path to perform a first radio frequency processing on the calibration signal and generate a first transmission signal; A calibration processing module is used to obtain a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to the first transmission signal; when the number of calibrations does not reach a preset iteration threshold, a first calibration process is performed on the received I-channel baseband signal and the Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the transmission processing module is controlled to resend the calibration signal to the transmission path until the number of calibrations reaches a preset iteration threshold.

8. The IQ calibration circuit according to claim 7, characterized in that: The calibration coefficient includes a plurality of sub-calibration coefficients of different levels; the transmission processing module includes: A transmission complex filter connected to the transmission path, and configured to send the calibration signal to the transmission path according to the received I-path baseband signal and Q-path baseband signal; The transmit complex filter comprises a plurality of transmit sub-filters, each of which comprises a plurality of cascaded transmit filter units, each of which comprises at least two delay devices and a multiplier connected in series, wherein the output ends of the two delay devices connected in series are connected to the input end of the multiplier; The i-th level delay device is used to perform delay processing on the received i-1-th level signal, and the i-th level multiplier is used to perform multiplication processing on the i-th level sub-calibration coefficient and the signal delayed by the i-th level delay device.

9. A radio frequency system, characterized in that: include: A transmitting path, used for receiving a calibration signal and performing a first radio frequency processing on the calibration signal to generate a first transmitting signal; A receiving path, used for performing a second radio frequency processing on the first transmission signal; An IQ calibration circuit is used to send a calibration signal to the transmitting path according to the received I-path baseband signal and Q-path baseband signal when the transmitting path and the receiving path are in a connected state; Acquire a first calibration coefficient of an I-channel baseband signal and a Q-channel baseband signal according to the first transmit signal; When the number of calibration times does not reach the preset iteration threshold, a first calibration process is performed on the received I-channel baseband signal and Q-channel baseband signal according to the first calibration coefficient to update the calibration signal, and the step of sending the calibration signal to the transmission path is re-executed until the number of calibration times reaches the preset iteration threshold.

10. An SDR chip, characterized in that: Comprising a radio frequency system as claimed in claim 9.

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