Iterative SDR chip IQ calibration method and circuit

Abstract

The present application relates to an iterative-based IQ calibration method and circuit for an SDR chip. The IQ calibration method includes, when the transmit path and the receive path are in a connected state, sending a calibration signal to the transmit path based on the received I-path baseband signal and Q-path baseband signal to instruct the transmit path to perform a first RF processing on the calibration signal and generate a first transmit signal, and obtaining a first calibration coefficient for the I-path baseband signal and the Q-path baseband signal based on the first transmit signal; further, when the number of calibrations does not reach a preset iteration threshold, performing a first calibration process on the received I-path baseband signal and the Q-path baseband signal based on the first calibration coefficient to update the calibration signal, and re-executing the step of sending the calibration signal to the transmit path until the number of calibrations reaches the preset iteration threshold. Multiple iterative processes can improve the accuracy of the finally obtained first calibration coefficient, thereby improving the IQ image suppression ratio of the transmit path.

Description

Technical Field

[0001] The present application relates to the technical field of radio frequency transceivers, and in particular to an iterative-based 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, forming a complex SDR chip.

[0003] SDR transceivers typically use quadrature modulation to modulate and demodulate signals. However, the signals in the quadrature and in-phase channels may experience phase or amplitude imbalance, a phenomenon known as IQ imbalance. This imbalance can cause image interference in the transmitted and received signals, reducing the static range and severely impacting baseband signal demodulation. 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 transmit path and a receive path; the method comprises:

[0006] When the transmitting path and the receiving path are in a connected state, sending a calibration signal to the transmitting path based on the received I-channel baseband signal and the Q-channel 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 first calibration coefficients for the I-channel baseband signal and the Q-channel baseband signal according to the first transmit signal;

[0008] If 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 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 transmit path is re-executed until the number of calibrations reaches the preset iteration threshold.

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

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

[0011] determining an imbalance parameter of the I baseband signal and the Q 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, obtaining 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] Perform a second calibration process 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] Obtaining target calibration conditions for an I-channel baseband signal and a Q-channel baseband signal; the target calibration conditions comprising 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] When 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 first RF 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] Determining a preset number of calibration frequencies within the target frequency band, where each calibration frequency is different and a 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, applied to a radio frequency system, the IQ calibration circuit comprising:

[0028] a transmission processing module, configured to, when the transmission path and the reception path are in a connected state, send a calibration signal to the transmission path based on the received I-channel baseband signal and the Q-channel baseband signal, 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 configured to obtain a first calibration coefficient for an I-channel baseband signal and a Q-channel baseband signal based on the first transmission signal; if the number of calibrations does not reach a preset iteration threshold, perform a first calibration process on the received I-channel baseband signal and the Q-channel baseband signal based on the first calibration coefficient to update the calibration signal, and control the transmission processing module to resend the calibration signal to the transmission path until the number of calibrations reaches the preset iteration threshold.

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

[0031] a transmit complex filter connected to the transmit path, and configured to send the calibration signal to the transmit path based on the received I-channel baseband signal and the Q-channel baseband signal;

[0032] The transmit complex filter includes a plurality of transmit sub-filters, each of which includes a plurality of cascaded transmit filter units, each of which includes 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 delay device of the i-th stage is used to perform delay processing on the received i-1-th stage signal, and the multiplier of the i-th stage is used to perform multiplication processing on the i-th stage sub-calibration coefficient and the signal delayed by the i-th stage delay device.

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

[0035] a transmitting path, configured to receive a calibration signal and perform a first radio frequency processing on the calibration signal to generate a first transmitting signal;

[0036] a receiving path, configured to perform a second radio frequency processing on the first transmit signal;

[0037] The IQ calibration circuit is configured to, when the transmit path and the receive path are in a connected state, send a calibration signal to the transmit path based on the received I baseband signal and the Q baseband signal; obtain first calibration coefficients for the I baseband signal and the Q baseband signal based on the first transmit signal; and, if the number of calibrations does not reach a preset iteration threshold, perform a first calibration process on the received I baseband signal and the Q baseband signal based on the first calibration coefficients to update the calibration signal, and re-execute the step of sending the calibration signal to the transmit 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 iterative SDR chip IQ calibration method and circuit, when the transmit and receive paths are connected, a calibration signal is sent to the transmit path based on the received I and Q baseband signals, instructing the transmit path to perform a first RF processing on the calibration signal and generate a first transmit signal. First calibration coefficients for the I and Q baseband signals are then obtained based on the first transmit signal. Furthermore, if the number of calibration cycles does not reach a preset iteration threshold, the first calibration process is performed on the received I and Q baseband signals based on the first calibration coefficients to update the calibration signals, and the step of sending the calibration signal to the transmit path is repeated until the number of calibration cycles reaches the preset iteration threshold. It is understood that multiple iterative processes can improve the accuracy of the ultimately obtained first calibration coefficients. Using the first calibration coefficients obtained from the multiple iterative processes to perform pre-distortion compensation on the I and Q baseband signals of the transmit path during normal operation of the RF system can improve the image rejection ratio of the transmit path. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. 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 first calibration coefficients for an I-channel baseband signal and a Q-channel baseband signal according to a first transmit signal provided in an embodiment;

[0044] Figure 4 A compensation model provided in one 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 is provided for 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 is provided in accordance with a specific embodiment;

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

[0050] Figure 10 A comparison diagram of the IQ image suppression ratio of a transmit path after two calibrations and before no calibration provided by an embodiment;

[0051] Figure 11 A comparison diagram of the IQ image suppression ratio of a transmit path after three calibrations and without calibration provided by an embodiment;

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

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

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

[0055] Figure 15 A schematic diagram of calculating a sub-calibration coefficient from a compensation coefficient B according to an embodiment;

[0056] Figure 16 A schematic diagram of calculating a sub-calibration coefficient from a compensation coefficient C according to an embodiment is provided. DETAILED DESCRIPTION

[0057] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided 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 pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0059] It will be understood that the terms "first", "second", etc. used in this application may be used to describe various data in this article, 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 there is transmission of electrical signals or data between the connected circuits, modules, units, etc.

[0061] It is understood that “at least one” refers to one or more, “a plurality” refers to two or more, and “at least a portion of an element” refers to a portion or all of an element.

[0062] As used herein, the singular forms "a," "an," and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include," "comprising," "having," and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Furthermore, the term "and / or" as 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 RF system includes a signal source, an IQ calibration circuit, a transmit path, and a receive path (the signal source is not shown). The IQ calibration circuit is connected to the transmit path, receive path, and signal source, respectively. The transmit path includes an I transmit path, a Q transmit path, and a power amplifier (PPA). The I transmit path and the Q transmit path each include a first FIR filter, a multi-stage interpolation filter (HB2, HB3), a digital-to-analog converter (DAC), a first low-pass filter, and an up-conversion mixer, all connected in series. The receive path includes a low-noise filter (LNA), an I receive path, and a Q receive path. The I receive path and the Q receive path each include a down-conversion mixer, a second low-pass filter, an analog-to-digital converter (ADC), a multi-stage decimation filter (HB2, HB3), and a second FIR filter, all connected in series. 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 transmit path and the receive path are connected, a calibration signal is sent to the transmit path based on the received I-channel baseband signal and the Q-channel baseband signal to instruct the transmit path to perform a first RF processing on the calibration signal and generate a first transmit signal.

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

[0067] It is understood that when the transmit and receive paths are connected, the IQ calibration circuit sends a calibration signal to the transmit path based on the received I and Q baseband signals. After receiving the calibration signal, the transmit path performs a first RF processing on the calibration signal to generate a first transmit signal. The first RF processing includes filtering, interpolation, digital-to-analog conversion, and up-conversion mixing on the calibration signal. The first transmit signal is an 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 the I-channel baseband signal and the Q-channel baseband signal in the transmission path.

[0070] In step 206, if the number of calibrations does not reach the 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 step of sending the calibration signal to the transmit path is re-executed until the number of calibrations 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] If the number of calibrations does not reach a preset iteration threshold, the IQ calibration circuit may perform a first calibration on the received I and Q baseband signals based on the first calibration coefficients to update the calibration signals, and send the new calibration signals to the transmit path to obtain new first calibration coefficients. If the number of calibrations is 0, the calibration signals are the I and Q baseband signals; if the calibration signals are greater than 0, the calibration signals are the signals obtained by performing the first calibration on the I and Q baseband signals based on the obtained first calibration coefficients.

[0073] In this embodiment, when the transmit path and receive path are connected, a calibration signal is sent to the transmit path based on the received I and Q baseband signals to instruct the transmit path to perform a first RF processing on the calibration signal and generate a first transmit signal. First calibration coefficients for the I and Q baseband signals are then obtained based on the first transmit signal. Furthermore, if the number of calibrations does not reach a preset iteration threshold, the first calibration process is performed on the received I and Q baseband signals based on the first calibration coefficients to update the calibration signals, and the step of sending the calibration signal to the transmit path is repeated until the number of calibrations reaches the preset iteration threshold. It is understood that multiple iterations can improve the accuracy of the ultimately obtained first calibration coefficients. Using the first calibration coefficients obtained through multiple iterations to perform predistortion compensation on the I and Q baseband signals of the transmit path during normal operation of the RF system can improve the image rejection ratio of the transmit path.

[0074] In one embodiment, Figure 3 As shown, obtaining 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 obtaining 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 obtaining 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 decimation in the receive path. The second calibration coefficient is used to calibrate IQ imbalance in the receive path. The first received signal includes an I signal and a Q signal.

[0078] It can be understood that the second calibration processing is performed on the second received signal using 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 parameter 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 imbalance parameters of the I baseband signal and the Q baseband signal according to the first received signal.

[0080] The imbalance parameters include amplitude imbalance value and phase imbalance value. Assuming that the I-path signal in the first received signal is used 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 value.

[0082] Step 306: Determine a compensation coefficient according to the imbalance 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 amplitude imbalance value and the phase imbalance value according to the above formula (1) and formula (2).

[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 inverse order 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 iteration 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 order processing on the compensation coefficients Bm and Cm, the final first calibration coefficient can be obtained.

[0095] Using the first calibration coefficients obtained through this iterative process to perform a first calibration on the IQ channel significantly improves the IQ image rejection ratio of the transmit path. The applicant has demonstrated that using the first calibration coefficients obtained through a single iteration to compensate for the baseband signal of the IQ channel can increase the IQ image rejection ratio to 70 dB.

[0096] In addition, since the correction value of phase imbalance in the IQ channel imbalance calibration 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 further 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 at the target transmit gain.

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

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

[0100] For example, Figure 5As shown, when calibrating the transmit path, the target temperature, target frequency band, and target transmit gain are sequentially determined. The signal source is controlled to generate the I and Q baseband signals within the target frequency bands. Then, steps 202 to 206 are executed to obtain first calibration coefficients and store them in memory. Calibration is then performed for the next combination of temperature, frequency band, and transmit gain until all calibration conditions are complete.

[0101] In one embodiment, controlling the 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, where 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 the I-channel baseband signal and the Q-channel baseband signal corresponding to each calibration frequency.

[0102] According to the principle of differentiation, a wideband signal is composed of the superposition of sufficiently narrowband signals. For narrowband signals, their IQ imbalance parameters can be assumed to be constant and frequency-independent. Therefore, a preset number of calibration frequencies can be determined within the target frequency band. The frequency difference between adjacent calibration frequencies is the length of the target frequency band divided by the preset number. The signal source is controlled to generate the I and Q baseband signals corresponding to each calibration frequency. Then, the first received signal corresponding to each calibration frequency is acquired through the receiving path, and multiple first calibration coefficients are calculated based on these multiple first received signals. The preset number is equal to the number of complex filter stages in the IQ calibration circuit.

[0103] In one embodiment, the IQ calibration method of the present application also includes calibration of the receiving path, specifically, including the steps of obtaining a third received 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 received signal.

[0104] When the transmit and receive paths are disconnected, the path between the receive path and the calibration PLL is connected, allowing the calibration PLL (phase-locked loop) to provide the receive path with an RF signal. The receive path then processes the RF signal through down-conversion mixing, low-pass filtering, analog-to-digital conversion, and decimation to generate a third received signal.

[0105] Furthermore, based on the same process as steps 304 to 308 above, the amplitude imbalance values ​​and phase imbalance values ​​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 values ​​and the phase imbalance values. 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 this application can be divided into calibration of the receive path and calibration of the transmit path. Because the acquisition of the first calibration coefficient for the transmit path relies on the I and Q signals in the receive path, calibration of the receive path is required before calibrating the transmit path. Assuming the target frequency band is fL to fL+100 MHz, the order of the complex filter in the IQ calibration circuit is 128, and the frequency midpoint of the target frequency band, fL+50 MHz, 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: Control the transmit path and the receive path to be disconnected, and control the receive path to be connected to the calibration PLL.

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

[0112] Step 606, obtaining a third received 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: Obtain 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 , performing 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+50 MHz, respectively.

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

[0121] Step 808, using Figure 6 Performing a second calibration process on the second received signal using the obtained 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 equal to the previous calibration frequency + 100 MHz / 128, and obtain the compensation coefficient corresponding to the current calibration frequency. Repeat this step 127 times to obtain the compensation coefficients corresponding to 128 calibration frequencies.

[0125] Step 816: Obtain 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 add 1 to the value of the calibration times.

[0126] Step 820, determine whether the number of calibrations reaches the preset iteration threshold. If not, control the signal source again to generate the I-channel baseband signal and the Q-channel baseband signal with a calibration frequency of fL, and use the first calibration coefficient 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 calibrations reaches the preset iteration threshold.

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

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

[0129] In one embodiment, Figure 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 transmit processing module 1202 is connected to the transmit path 1206 and can be used to send a calibration signal to the transmit path 1206 based on the received I-channel baseband signal and Q-channel baseband signal when the transmit path 1206 and the receive path 1208 are in a connected state, thereby instructing the transmit path 1206 to perform a first RF processing on the calibration signal and generate a first transmit signal.

[0131] The calibration processing module 1204 is connected to the transmission processing module 1202 and the receiving path 1208 respectively, and can be used to obtain a first calibration coefficient of the I-channel baseband signal and the Q-channel 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-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 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 detailed 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 transmit processing module includes a transmit complex filter connected to the transmit path and configured to send a calibration signal to the transmit path based on the received I-channel baseband signal and the Q-channel baseband signal.

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

[0135] The emission sub-filter can be implemented using a systolic Multiply-Accumulate structure. Figure 14 As shown, each transmit sub-filter includes multiple cascaded transmit filter units ( Figure 14 Each transmit filter unit includes at least two delay units and a multiplier connected in series, with the outputs of the two delay units connected to the inputs of the multiplier. The i-th delay unit is used to delay the received i-1-th level signal, and the i-th multiplier is used to multiply the i-th level sub-calibration coefficient by the signal delayed by the i-th level delay unit. The calibration coefficients include multiple sub-calibration coefficients of different levels, which are represented as coefficients for each level of filter unit in the transmit sub-filter.

[0136] It can be understood that the output and 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-filter stages, and X(i) represents the baseband signal.

[0139] In addition, each filtering 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 configured to obtain first calibration coefficients for the I baseband signal and the Q baseband signal based on the first transmit signal. Specifically, the calibration coefficient determination unit may first obtain a corresponding first receive signal based on the first transmit signal, determine imbalance parameters of the I baseband signal and the Q baseband signal based on the first receive signal, determine compensation coefficients based on the imbalance parameters, and determine the first calibration coefficients based on the compensation coefficients.

[0142] Among them, for Figure 13 In the framework of the transmit complex filter shown in FIG, 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). Figure 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. By performing reverse processing on the k real data BI1~BIk, k sub-calibration coefficients BHI1~BHIk of the BHI filter are obtained. By performing reverse processing on the k imaginary data, k sub-calibration coefficients BHQ1~BHQk of the BHQ filter are obtained.

[0143] Similarly, if Figure 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 performing reverse processing on the k real data CI, k sub-calibration coefficients CHI1~CHIk of the CHI filter are obtained. By performing reverse processing on 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 the first calibration coefficient to update the calibration signal when the number of calibration times does not reach the preset iteration threshold, and control the transmission processing module to resend the calibration signal to the transmission path until the number of calibration times reaches the preset iteration threshold.

[0145] The specific description of the function of the iteration unit can be found in 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 connected to the receiving path and the calibration processing module, respectively, and configured to perform a second calibration process on the second received signal according to a pre-stored second calibration coefficient to obtain the first received signal.

[0147] The receive processing module includes a receive complex filter. The receive complex filter framework is the same as the transmit complex filter framework, including a BHI filter, a BHQ filter, a CHI filter, and a CHQ filter. The definition of the receive complex filter is similar to the definition of the transmit complex filter.

[0148] In one embodiment, the IQ calibration circuit further includes a storage module. The storage module is connected to the calibration processing module, the transmit processing module, and the receive processing module, and is configured to store first and second calibration coefficients corresponding to each target frequency band. After calibration of the transmit and receive paths is completed, the first and second calibration coefficients corresponding to the signal frequency band can be directly retrieved from the storage module during normal operation of the RF system.

[0149] Based on the same inventive concept, embodiments of the present application further provide a radio frequency system for implementing the aforementioned IQ calibration method. The solution provided by this radio frequency system is similar to the solution described in the aforementioned method. Therefore, the specific limitations in one or more radio frequency system embodiments provided below can be found in the above-described limitations on the IQ calibration method and are not further elaborated 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 configured to, when the transmit path and the receive path are in a connected state, send a calibration signal to the transmit path based on the received I baseband signal and the Q baseband signal; obtain first calibration coefficients for the I baseband signal and the Q baseband signal based on the first transmit signal; and, if the number of calibrations does not reach a preset iteration threshold, perform a first calibration process on the received I baseband signal and the Q baseband signal based on the first calibration coefficients to update the calibration signal, and re-execute the step of sending the calibration signal to the transmit path until the number of calibrations reaches the preset iteration threshold.

[0154] In this embodiment, an IQ calibration circuit processes the RF signal based on the received I and Q baseband signals when the transmit and receive paths are connected. The calibration signal is sent to the transmit path, instructing the transmit path to perform a first RF processing on the calibration signal and generate a first transmit signal. First calibration coefficients for the I and Q baseband signals are obtained based on the first transmit signal. The accuracy of the ultimately obtained first calibration coefficients is improved by iteratively obtaining the first calibration coefficients. During normal operation of the RF system, the first calibration coefficients are used to perform predistortion compensation on the I and Q baseband signals of the transmit path, thereby improving the image rejection ratio of the transmit path.

[0155] In one embodiment, the IQ calibration circuit is further 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 a compensation coefficient based on the imbalance parameter; and determine a first calibration coefficient based on the compensation coefficient.

[0156] In one embodiment, the IQ calibration circuit is further configured 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 further 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 at the target transmission gain.

[0159] In one embodiment, the IQ calibration circuit is further 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 configured 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 based on the third received signal.

[0161] The present application also provides an SDR chip for implementing the aforementioned IQ calibration method. The solution provided by this SDR chip is similar to the solution described in the aforementioned method. Therefore, the specific limitations in one or more of the following SDR chip embodiments can be found in the aforementioned limitations on the signal calibration method and will not be further elaborated 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. The memory stores a computer program, and the processor implements the IQ calibration method provided in any of the above embodiments when executing the computer program.

[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, reference to the terms "some embodiments" or "other embodiments" 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 descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0168] The technical features of the above embodiments can 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 merely illustrate several embodiments of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. An IQ calibration method, characterized in that: An IQ calibration circuit is applied to a radio frequency system, wherein the radio frequency system further includes a transmitting path and a receiving path; and the method includes: When the transmitting path and the receiving path are in a disconnected state, obtaining a third receiving signal corresponding to the radio frequency signal; obtaining a second calibration coefficient corresponding to the radio frequency signal according to the third received signal; wherein the second calibration coefficient is used to implement IQ imbalance calibration in the receiving path; When the transmitting path and the receiving path are in a connected state, sending a calibration signal to the transmitting path based on the received I-channel baseband signal and the Q-channel 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 second received signal corresponding to the first transmitted signal; performing a second calibration process on the second received signal according to the second calibration coefficient to obtain a first received signal; determining an imbalance parameter of the I baseband signal and the Q baseband signal according to the first received signal; determining a compensation coefficient according to the imbalance parameter; Determining a first calibration coefficient based on the compensation coefficient; the first calibration coefficient is used to implement predistortion compensation for the I-channel baseband signal and the Q-channel baseband signal in the transmission path; If 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 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 transmit path is re-executed until the number of calibrations reaches the preset iteration threshold.

2. The method according to claim 1, characterized in that The radio frequency system further includes a signal source; and the method further includes: Obtaining target calibration conditions for an I-channel baseband signal and a Q-channel baseband signal; the target calibration conditions comprising 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; When 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 first RF processing on the I baseband signal and the Q baseband signal at the target transmit gain.

3. The method according to claim 2, 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: Determining a preset number of calibration frequencies within the target frequency band, where each calibration frequency is different and a 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.

4. An IQ calibration circuit, characterized in that: Applied to a radio frequency system, the IQ calibration circuit includes: a transmission processing module, configured to, when the transmission path and the reception path are in a connected state, send a calibration signal to the transmission path based on the received I-channel baseband signal and the Q-channel baseband signal, 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 configured to, when the transmit path and the receive path are disconnected, obtain a third received signal corresponding to the radio frequency signal; obtain a second calibration coefficient corresponding to the radio frequency signal based on the third received signal; the second calibration coefficient being used to implement IQ imbalance calibration in the receive path; and obtain a second received signal corresponding to the first transmit signal; perform a second calibration process on the second received signal based on the second calibration coefficient to obtain a first received signal; determine imbalance parameters of the I-channel baseband signal and the Q-channel baseband signal based on the first received signal; determine a compensation coefficient based on the imbalance parameters; and determine a first calibration coefficient based on the compensation coefficient; the first calibration coefficient being used to implement pre-distortion compensation for the I-channel baseband signal and the Q-channel baseband signal in the transmit path; and, if the number of calibrations does not reach a preset iteration threshold, perform a first calibration process on the received I-channel baseband signal and the Q-channel baseband signal based on the first calibration coefficient to update the calibration signal, and control the transmit processing module to resend the calibration signal to the transmit path until the number of calibrations reaches the preset iteration threshold.

5. The IQ calibration circuit according to claim 4, characterized in that: The calibration coefficient includes a plurality of sub-calibration coefficients of different levels; the transmission processing module includes: a transmit complex filter connected to the transmit path, and configured to send the calibration signal to the transmit path based on the received I-channel baseband signal and the Q-channel baseband signal; The transmit complex filter includes a plurality of transmit sub-filters, each of which includes a plurality of cascaded transmit filter units, each of which includes 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 delay device of the i-th stage is used to perform delay processing on the received i-1-th stage signal, and the multiplier of the i-th stage is used to perform multiplication processing on the i-th stage sub-calibration coefficient and the signal delayed by the i-th stage delay device.

6. A radio frequency system, characterized in that: include: a transmitting path, configured to receive a calibration signal and perform a first radio frequency processing on the calibration signal to generate a first transmitting signal; a receiving path, configured to perform a second radio frequency processing on the first transmit signal and the radio frequency signal; An IQ calibration circuit is configured to obtain a third received signal corresponding to the radio frequency signal when the transmit path and the receive path are disconnected; and obtain a second calibration coefficient corresponding to the radio frequency signal based on the third received signal; the second calibration coefficient is used to implement IQ imbalance calibration in the receive path; 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 the Q-path baseband signal; and a second receiving signal corresponding to the first transmitting signal is obtained; performing a second calibration process on the second received signal according to the second calibration coefficient to obtain a first received signal; determining an imbalance parameter of the I baseband signal and the Q baseband signal according to the first received signal; determining a compensation coefficient according to the imbalance parameter; determining a first calibration coefficient according to the compensation coefficient; The first calibration coefficient is used to achieve predistortion compensation for the I-channel baseband signal and the Q-channel baseband signal in the transmission path; If 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 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 transmit path is re-executed until the number of calibrations reaches the preset iteration threshold.

7. An SDR chip, characterized in that: Comprising the radio frequency system as claimed in claim 6.

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