OFDM frequency offset compensation method and system based on radio frequency agile transceiver

Abstract

The application discloses an OFDM frequency offset compensation method and system based on a radio frequency agile transceiver, and comprises the following steps: in a wireless channel, performing autocorrelation operation on a received signal through AD936X, and judging whether the OFDM signal in the wireless channel is a valid signal through the autocorrelation result; when the OFDM signal is valid, calculating whether the error of the frequency offset at this time is within a predetermined error threshold range through an inverse tangent operation; when the error is outside the threshold range, constantly adjusting the frequency of a local oscillator (LO) of a modulation end and a demodulation end AD936X according to the positive and negative situations of the inverse tangent, finally achieving a dynamic balance and eliminating the frequency offset error of the OFDM signal in the wireless channel, so that the frequency offset error is within the error threshold range, approximate frequency offset estimation compensation is obtained, otherwise, a success flag signal is returned and the module is exited; the application has the advantages of low complexity, fast synchronization time and simple implementation, and is very suitable for OFDM frequency offset compensation of a radio frequency agile transceiver front end in a wireless channel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to an OFDM frequency offset compensation method and system based on a radio frequency agile transceiver. BACKGROUND

[0002] OFDM is a multicarrier modulation system, which can modulate and transmit on multiple orthogonal carriers (orthogonal carriers do not interfere with each other, similar to I and Q in IQ modulation, which are orthogonal and do not interfere with each other), and achieve large bandwidth data transmission by extending multiple subcarriers (subchannels).

[0003] AD9361 and AD9363, AD9364 is a highly integrated radio frequency (RF) transceiver that can be configured for various applications. These devices integrate the RF, mixed-signal, and digital modules needed to provide all transceiver functionality in a single device. Programmability makes this wideband transceiver suitable for multiple communication standards, including frequency division duplex (FDD) and time division duplex (TDD) systems.

[0004] The LO (local oscillator) operating frequency range of the AD9361 receiver is 70MHz to 6.0GHz, and the LO operating frequency range of the transmitter is 47MHz to 6.0GHz, covering most licensed and unlicensed frequency bands, and supporting a communication bandwidth range of 200KHz to 56MHz. AD9361 and AD9364 also provide self-calibration and automatic gain control (AGC) systems to maintain high performance under varying temperature and input signal conditions.

[0005] In the field of wireless communication, when using a radio frequency agile transceiver as a radio frequency front end, there will be a frequency difference between the local oscillators of the receiver and the transmitter, which will cause the orthogonal baseband sampling data of the zero intermediate frequency receiver to contain a frequency offset component, resulting in a phase rotation of the IQ sampling data of the received data.

[0006] Therefore, it is very important to explore an effective solution to the frequency offset caused by the difference between the local oscillators of the transmitter and the receiver of the zero intermediate frequency transceiver. Wireless OFDM communication technology should have a method of frequency offset compensation and estimation.

[0007] For IEEE802.11 protocol, the current technology is to realize relevant frequency offset estimation and compensation through the autocorrelation of long and short training sequences and through the algorithm designed by each protocol. However, since the frequency offset compensation is the most important part of the communication system, it is difficult to implement, the accuracy is not high, and it greatly increases the difficulty of implementation for engineers.

[0008] An OFDM frequency offset estimation method, system and device based on IEEE 802.11 (application number: CN201810099899.5) is disclosed. The first frequency offset estimation is obtained by self-correlation of the same two long training sequences in the preamble, and the subsequent signal part is compensated. Then the compensated signal part is re-modulated, converted into the frequency domain, and the second frequency offset estimation is obtained by local self-correlation operation. Finally, the first frequency offset estimation and the second frequency offset estimation are used to compensate the subsequent payload part. However, the difficulty of implementing the algorithm is great. SUMMARY

[0009] The present application provides an OFDM frequency offset compensation method and system based on a radio frequency agile transceiver, which only needs to detect the arrival of the OFDM frame signal in the wireless channel, and then uses a simple multiplier and CORDIC to gradually compensate the frequency offset of the wireless OFDM system. The present application differs from traditional algorithms in that it uses a high-integration radio frequency (RF) transceiver AD936X to solve the problems of high implementation complexity and high accuracy of existing carrier frequency offset estimation algorithms, greatly reducing the implementation difficulty of engineers.

[0010] To achieve the above-mentioned scheme purposes, the technical solutions adopted by the present application are as follows:

[0011] The present application provides an OFDM frequency offset compensation method based on a radio frequency agile transceiver, which includes the following steps: according to the OFDM signal frame structure of IEEE 802.11, detecting whether the OFDM signal in the wireless channel arrives through the short training sequence in the wireless channel. If the arrival of the OFDM signal in the wireless channel is not detected, the detection is continued. If the arrival of the OFDM signal in the wireless channel is detected, the inverse tangent module is entered. The value of the inverse tangent calculated by the inverse tangent module is used to determine whether the value exceeds the threshold. If the value is within the set threshold range, a success flag signal is returned, the frequency offset correction module is exited, and if the value exceeds the set threshold range, the sign bit of the inverse tangent result is used to adjust the frequency of the local oscillator (LO) of the second-stage IQ modulator / demodulator to be upward or downward biased, and the AD936X sends a synchronization flag signal to the transmitting end. After receiving the flag signal, the transmitting end updates the frequency of the local oscillator (LO) of the AD936X in the modulation end to be offset in the opposite direction through the SPI communication protocol. By adjusting the radio frequency agile transceiver AD936X of the transmitting end and the receiving end at the same time, the frequency offset threshold range set by us is reached, so that the radio frequency agile transceivers AD936X of the transmitting end and the receiving end generate the same frequency, and the purpose of frequency offset correction is finally achieved.

[0012] Further, the radio frequency signal expression sent out by the second stage IQ modulation in the wireless channel is complex equivalent form:

[0013]

[0014] Wherein, x(n) is the baseband signal, t is time, F tx is the transmitting end AD936X carrier frequency, which is equivalent to moving the baseband signal x(n) to F tx frequency point and sending out.

[0015] Further, the wireless channel is detected by the short training sequence to determine whether the OFDM signal comes in the wireless channel, including the following steps:

[0016] The autocorrelation operation is performed on the ten short training sequence data in the received signal of the receiver;

[0017] When the autocorrelation value of the received data of the receiver exceeds the threshold value;

[0018] And when the energy exceeds the threshold value and remains for several clock cycles;

[0019] And when the current two conditions are met, the fluctuation of the received data is detected to determine whether the positive value data and negative value data signal exceeding a certain number threshold is received within a certain time;

[0020] If yes, it means that the OFDM signal is successfully detected; if not, repeat the detection;

[0021] The formula of the short training sequence data detection algorithm of the OFDM signal receiving end in the wireless channel is:

[0022]

[0023] Wherein, S[i] represents the signal received by the receiver through AD936X, corr[i] represents the grouping detection result, Indicates the conjugate, D represents the delay parameter.

[0024] Further, wherein the frame structure of the OFDM signal includes:

[0025] Ten short training sequence parameters, cyclic prefix parameters, two long training sequence parameters, signal domain parameters, data domain parameters.

[0026] The signal expression before entering the arctangent module is:

[0027] r=x(n)e 2πεn / N

[0028] Wherein, x(n) is the baseband signal, ε is the frequency offset error generated when the second IQ modulation, N is the length of an OFDM symbol, n is the index of the baseband signal.

[0029] The result obtained after the arctangent module is:

[0030]

[0031] Wherein, the result of result is positive or negative only related to ε.

[0032] Further, the principle of judging the arctangent result positive or negative and the formula are:

[0033]

[0034] Wherein, F tx is the transmit carrier frequency of the AD936X at the transmitting end, F rx is the receive carrier frequency of the AD936X at the receiving end, and t is time.

[0035] Wherein, F tx and F rx are generated by two different RF agile transceivers AD936X. Although they are all through their own internal fractional frequency phase-locked loop (PLL) to generate their own transmitter and receiver local oscillator (LO) frequency and BBPLL, due to the actual work and many other factors, even if the two AD936X settings are the same, the local oscillator (LO) generated inside them is not the same, resulting in F tx and F rx are not the same and produce a frequency difference.

[0036] Further, if the result obtained by the arctangent module is negative, it means that the frequency of the receiving end AD936X is too high, and the AD936X receiving end local oscillator (LO) frequency needs to be adjusted downward.

[0037] Further, if the result obtained by the arctangent module is positive, it means that the frequency of the receiving end AD936X is too low, and the AD936X receiving end local oscillator (LO) frequency needs to be adjusted upward.

[0038] The formula for adjusting through the RF agile transceiver AD936X is as follows:

[0039] ε = RXLO - TXLO

[0040] Wherein, TXLO is the frequency of the AD936X local oscillator at the transmitting end, and RXLO is the frequency of the AD936X local oscillator at the receiving end.

[0041] Further, the smaller the threshold range set by the user, the more accurate the final frequency offset correction result.

[0042] Further, the frequency offset correction process is a continuous feedback process.

[0043] The application also provides an OFDM frequency offset compensation system based on a radio frequency agile transceiver, comprising:

[0044] The detection module is configured to detect whether the OFDM signal in the wireless channel arrives through a short training sequence in the wireless channel, and if the arrival of the OFDM signal in the wireless channel is not detected, the detection is continued; if the arrival of the OFDM signal in the wireless channel is detected, the arctangent module is entered.

[0045] The arctangent module is configured to calculate the arctangent result.

[0046] The frequency offset correction module is configured to determine whether the frequency offset error exceeds the predetermined threshold range through the arctangent result calculated by the arctangent module, and if the threshold range is within the threshold range, a success flag signal is returned; if the threshold range is outside the threshold range, the AD936X local oscillator (LO) frequency of the receiving end is adjusted upward or downward according to the sign bit of the arctangent result, and the AD936X sends a synchronization flag signal to the transmitting end; after the transmitting end receives the flag signal, the AD936X local oscillator (LO) frequency of the transmitting end is updated to offset in the opposite direction through the SPI communication protocol, and the AD936X local oscillator (LO) frequencies of the transmitting end and the receiving end are adjusted at the same time to reach the frequency offset threshold range set by us, so that the AD936X radio frequency agile transceivers of the transmitting end and the receiving end generate the same frequency, and the frequency offset correction is finally realized through continuous feedback.

[0047] Further, the application further comprises:

[0048] The update parameter module is configured to configure the new frequency calculated in the frequency offset correction module to the radio frequency agile transceiver AD936X through the SPI communication protocol, and complete the update of the AD936X local oscillator (LO) frequencies of the transmitting end and the receiving end.

[0049] The feedback gain module is configured to adjust the AD936X local oscillator (LO) frequencies of the transmitting end and the receiving end to make them offset upward or downward with a certain precision, and finally reach a dynamic balance to eliminate the frequency offset. It should be noted that the smaller the adjustment precision, the more accurate the final frequency offset compensation result.

[0050] Compared with the existing frequency offset compensation technology, the application has the following advantages:

[0051] 1. High accuracy, suitable for all OFDM frequency offset correction using RF transceiver front-end.

[0052] 2. Compared with the traditional OFDM frequency offset estimation algorithm, the application provides a new type of frequency offset compensation method, which can greatly save the time of frequency offset synchronization by using the advantages of programmable logic device, and the method is simple to implement and beneficial for engineers to implement.

[0053] 3. The application provides a new idea for the frequency offset compensation module, which is a heavy and difficult point for software radio developers.

[0054] 4. The entire frequency offset compensation module provided by the application reduces the hardware complexity and uses fewer resources to complete the OFDM frequency offset compensation in the wireless channel. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 A flow chart of an OFDM frequency offset compensation method based on a radio frequency transceiver is disclosed in the application.

[0056] Figure 2 A schematic diagram of an OFDM data packet of the IEEE802.11a protocol in a wireless channel is shown.

[0057] Figure 3 A specific implementation block diagram of the OFDM frequency offset compensation method based on the radio frequency transceiver is disclosed in the application.

[0058] Figure 4 A module block diagram of the envelope detection algorithm of the receiving end disclosed in the application is shown.

[0059] Figure 5 An algorithm simulation result diagram of the envelope detection of the receiving end is shown.

[0060] Figure 6 A block diagram of the second stage modulation of the transmitting end using AD936X is shown.

[0061] Figure 7 A block diagram of the local oscillator (LO) inside AD936X is shown.

[0062] Figure 8 A specific block diagram of the parameter updating module disclosed in the application is shown.

[0063] Figure 9 A specific block diagram of the parameter conversion module disclosed in the application is shown. DETAILED DESCRIPTION

[0064] The modules and specific steps involved in the application will be introduced completely and clearly in combination with the drawings and embodiments in the application.

[0065] We know the essence of OFDM modulation, two-stage IQ modulation, the current to the second stage IQ modulation caused by the frequency offset is mostly through the algorithm in the internal compensation, the present application provides a new way of thinking, by adjusting the radio frequency front end of the receiving center frequency to eliminate the influence of frequency offset.

[0066] As Figure 1 , the present application carries out the method for compensating the OFDM frequency offset based on the radio frequency agile transceiver, the first step is to detect the OFDM signal in the wireless channel, we according to the OFDM frame structure of IEEE802.11 protocol in Figure 2 , design the OFDM detection algorithm as shown in Figure 3 .

[0067] Said, Figure 4 is the specific implementation block diagram of OFDM detection algorithm, it includes:

[0068] Delay latch module, complex conjugate module, complex multiplication module, cumulative smoothing module, amplitude estimation module, comparator module.

[0069] The delay latch module is mainly to delay the signal received by the radio frequency agile transceiver for a sampling clock.

[0070] The delay latch module, the complex conjugate module and the complex multiplication module constitute the algorithm of the data packet detection, and the formula is:

[0071]

[0072] Wherein, S [i] represents the signal received by AD936X, corr [i] represents the result of grouping detection, Indicates the conjugate, D represents the delay parameter.

[0073] The addition of the cumulative smoothing module is mainly to eliminate the influence of noise in the wireless channel, so as to better detect whether the OFDM signal arrives.

[0074] The amplitude estimation module and the comparator module reduce the division operation in the formula, greatly reduce the consumption of resources, and reduce the hardware complexity.

[0075] The modulus of complex number is complex and not easy to realize, therefore, the present application uses an approximate algorithm instead, the average error of the algorithm is 0.006, and the formula principle is as follows:

[0076] Mag=Alpha*max(|I|,|Q|)+Beta*min(|I|,|Q|)

[0077] Where I is the real part of the complex signal, Q is the imaginary part of the complex signal, Alpha and Beta are different quantization parameters, here we take 1 and 1 / 4.

[0078] When there is no data received, there is only noise in the channel, in this case, the value of corr calculated according to the formula should be close to zero, the value of denominator will not be very large, but its multiple will be far greater than the numerator, so the value of corr is close to zero when there is no data received in the receiver, only when the OFDM data is correctly received, the value of corr should be particularly close to 1, and will remain until the end of the short training sequence data input.

[0079] The analysis result is consistent with the result in Figure 5 .

[0080] When the OFDM signal is not successfully detected, according to Figure 3 , the detection is repeated.

[0081] When the OFDM signal is successfully detected, it enters the next arctangent module.

[0082] The signal expression before entering the arctangent module is:

[0083] r = x(n) e 2πεn / N

[0084] Where x(n) is the baseband signal, ε is the frequency offset error generated when the second IQ modulation is performed, N is the length of an OFDM symbol, and n is the index of the baseband signal.

[0085] When the frequency offset is corrected, we send a pilot signal for frequency offset correction, which must be a real signal. The reason for this is to reduce the implementation complexity and avoid considering the influence of the phase of the x(n) signal on the arctangent module.

[0086] After the arctangent, the result expression is:

[0087]

[0088] Where the positive and negative of the result of result is only related to ε.

[0089] If the obtained ε value is within the set threshold range, return a success flag signal, and pull up the frequency offset correction flag signal to indicate that the frequency offset correction is successful, and then exit the frequency offset correction module.

[0090] If the obtained ε value is outside the set threshold range, jump to the next arctangent module to determine whether the value is positive or negative.

[0091] We can adjust the local oscillator (LO) frequency of the receiving end AD936X by the positive and negative cases of ε.

[0092] The principle and formula of judging the positive and negative of the arctangent result are as follows:

[0093]

[0094] Where F tx is the transmitting carrier frequency of the transmitting end AD936X, F rx is the receiving carrier frequency of the receiving end AD936X, and t is time.

[0095] Where F tx and F rx are generated by two different RF agile transceivers AD936X. Although they are generated by the respective internal fractional frequency synthesizer phase-locked loop (PLL) to generate the respective transmitter and receiver local oscillator (LO) frequency and BBPLL, due to the influence of many factors such as actual work, even if the two AD936Xs are set with the same parameters, the local oscillator (LO) generated by them is not the same, thereby causing F tx and F rx to be different and to generate a frequency difference.

[0096] If the result obtained by the arctangent module is negative, it represents that the local oscillator (LO) frequency of the receiving end AD936X is too high, and the local oscillator (LO) frequency of the receiving end AD936X needs to be adjusted to be lower.

[0097] If the result obtained by the arctangent module is positive, it represents that the local oscillator (LO) frequency of the receiving end AD936X is too low, and the local oscillator (LO) frequency of the receiving end AD936X needs to be adjusted to be higher.

[0098] The receiving end transmits the parameters back to the PS end through the AXI_LITE protocol.

[0099] After the PS end receives the new parameters, the parameter configuration of the local oscillator (LO) center frequency of the receiving end AD936X is completed through the SPI communication protocol.

[0100] At the same time, if it is out of the threshold range, the receiving end will feed back a flag signal to the transmitting end through the wireless channel.

[0101] The value of the flag signal is determined by the arctangent module.

[0102] If the result obtained by the arctangent module is negative, it represents that the local oscillator (LO) frequency of the transmitting end AD936X is too low, and the local oscillator (LO) frequency of the transmitting end AD936X needs to be adjusted to be higher.

[0103] If the result obtained by the arctangent module is positive, it represents that the local oscillator (LO) frequency of the sending end AD936X is too high, and the local oscillator (LO) frequency of the sending end AD936X needs to be adjusted downward.

[0104] The sending end returns the parameters to the PS end through the AXI_LITE protocol.

[0105] After the PS end receives the new parameters, the parameter configuration of the center frequency of the local oscillator (LO) of the sending end AD936X is completed through the SPI communication protocol.

[0106] The radio frequency agile transceiver AD936X of the sending end transmits the OFDM signal after modulation to the wireless channel through the newly set transmission frequency.

[0107] The smaller the threshold range set by the user is, the more accurate the final frequency offset correction result is.

[0108] The specific block diagram of the second-order modulation is shown in Figure 6 The sine and cosine signals generated by the second-order modulation are generated by the radio frequency agile transceiver AD936X, and in an ideal case, the demodulation end generates a sine and cosine signal of the same frequency and phase through the same operation, so as to complete the second-order IQ modulation and demodulation. The content of the application proposes a method for solving the frequency offset compensation caused by the difference between the local oscillators (LO) of the sending and receiving ends through the radio frequency agile transceiver AD936X.

[0109] The specific block diagram of the local oscillator (LO) inside the radio frequency agile transceiver AD936X is shown in Figure 7 The baseband signal sent by the local oscillator (TXLO) of the radio frequency agile transceiver AD936X of the sending end is up-converted to a specified frequency and transmitted, and the baseband signal down-converted to a specified frequency by the local oscillator (RXLO) of the radio frequency agile transceiver AD936X of the receiving end is transmitted through the wireless channel. The content of the application adjusts the RXLO of the receiving end to be as close as possible to the TXLO of the sending end, and then realizes a frequency offset correction.

[0110] The formula used is as follows:

[0111] ε=RXLO-TXLO

[0112] Wherein, TXLO is the frequency of the local oscillator (LO) of the AD936X of the sending end, and RXLO is the frequency of the local oscillator (LO) of the AD936X of the receiving end.

[0113] It needs to be explained that the local oscillator TXLO of the sending end and the local oscillator RXLO of the receiving end are all known, only due to the influence of actual work and other factors, the two will have a slight deviation, the deviation of the two is determined by the frequency of the up-conversion, the general deviation is from several tens of hertz to several hundred hertz. The patent content of the application assumes that the local oscillator of the sending end is standard and error-free, by continuously adjusting the local oscillator of the radio frequency agile transceiver AD936X of the sending end and the receiving end, the error of the two is made as same as possible.

[0114] The specific block diagram of the update parameter module is shown in Figure 8 The new frequency calculated in the frequency offset correction module is configured to the radio frequency agile transceiver AD936X through the SPI communication protocol to complete the update of the local oscillator (LO) frequency of the AD936X of the sending end and the receiving end.

[0115] The specific block diagram of the parameter conversion module is shown in Figure 9 The parameter conversion module mainly includes a judgment module and a gain adjustment module.

[0116] It needs to be explained that the application makes full use of the programmability of AD936X and the characteristics of the combination of software and hardware of ZYNQ platform, the AXI protocol can continuously feedback to the PS end, and the PS end modifies the center frequency of the AD936X receiving end in real time through the SPI communication protocol, and then the frequency synchronization of the two different radio frequency agile transceivers AD936X is achieved, and the frequency offset error in the second stage IQ modulation and demodulation is eliminated.

[0117] The method of the application is simple, different from the traditional frequency offset compensation method, greatly reduces the complexity of the algorithm implementation, greatly reduces the difficulty of the technical personnel in the field to design a set of frequency offset compensation algorithm, thereby solving the core difficulty in software radio, and facilitating the true implementation of software radio (SDR).

[0118] The above is only the embodiment designed by the application, and the application is not limited to the above examples. It can be understood that other improvements and changes directly derived or thought by the technical personnel in the field without departing from the basic concept of the application should be considered within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A radio frequency agile transceiver-based OFDM frequency offset compensation method, characterized by comprising the following steps: constantly receiving signals in a wireless channel through a radio frequency agile transceiver AD936X, detecting whether an OFDM signal in the wireless channel arrives using a short training sequence unique in an OFDM frame structure, if no OFDM signal in the wireless channel is detected to arrive, continuing to loop detection, if the OFDM signal in the wireless channel is detected to arrive, entering an arctangent module, judging whether a frequency offset error exceeds a predetermined threshold range through a result of the arctangent calculated by the arctangent module, if the frequency offset error is within the threshold range, returning a success flag signal, if the frequency offset error is outside the threshold range, updating a local oscillator (LO) frequency of a demodulation end AD936X upward or downward according to a sign bit of the arctangent result through a SPI communication protocol, and the AD936X sends a synchronization flag signal to a sending end, after the sending end receives the flag signal, updating a local oscillator (LO) frequency of a modulation end AD936X to shift in the opposite direction through the SPI communication protocol, adjusting the radio frequency agile transceiver AD936X of the sending end and the receiving end at the same time to reach a set frequency offset threshold range, and finally realizing frequency offset correction. The OFDM signal frame structure comprises ten short training sequence parameters, two long training sequence parameters, a signal domain parameter, a data domain parameter, and a cyclic prefix parameter. A radio frequency signal expression of the second-stage IQ modulation transmitted in the wireless channel is a complex equivalent: Detecting whether an OFDM signal in the wireless channel arrives through a short training sequence in the wireless channel comprises the following steps:

2. The method of claim 1, wherein the radio frequency agile transceiver based OFDM frequency offset compensation method is characterized by: performing autocorrelation operation on ten short training sequence data in the signal received by the receiver; Wherein, x(n) is the baseband signal, t is time, F tx is the transmitting carrier frequency of the transmitting end AD936X, which is equivalent to moving the baseband signal x(n) to F tx frequency point for transmission.

3. The method of claim 1, wherein the radio frequency agile transceiver based OFDM frequency offset compensation method is characterized by: when the autocorrelation value of the data received by the receiver exceeds a threshold value; and when the energy exceeds the threshold value and remains for a number of clock cycles; and when the current two conditions are met, detecting fluctuation of the received data, judging whether more than a certain number of threshold positive value data and negative value data signals are received within a certain time; if yes, it means that the OFDM signal is successfully detected; if no, repeat the detection; The formula principle of the short training sequence data detection algorithm of the receiving end is as follows: The signal before the arctangent module is: wherein x(n) is a baseband signal, ε is a frequency offset error generated when the second-stage IQ modulation and demodulation is performed, N is a symbol length of an OFDM, and n is an index of the baseband signal. Wherein, S[i] represents the signal received by the receiving end through AD936X, corr[i] represents the result of packet detection, represents conjugate, D represents delay parameter.

4. The method of claim 1, wherein the radio frequency agile transceiver is an OFDM frequency offset compensation method, characterized by:

5. The radio frequency agile transceiver-based OFDM frequency offset compensation method according to claim 4, characterized by: r = x(n) e 2πεn / N the result obtained by calling the arctangent module in the FPGA is: wherein the result of the result is only related to ε. Adjusting the local oscillator (LO) frequency of the receiving end AD936X upward or downward according to the sign bit of the arctangent result comprises the following steps: ​ 6. The OFDM frequency offset compensation method based on radio frequency agile transceiver according to claim 5, characterized in that: ​ If the result of arctangent is positive, it means that the frequency of AD936X receiver is too small, so the frequency of AD936X local oscillator (LO) should be adjusted upward; if the result of arctangent is negative, it means that the frequency of AD936X receiver is too large, so the frequency of AD936X local oscillator (LO) should be adjusted downward. The formula for adjusting the frequency of AD936X receiver through the highest bit of arctangent is as follows: Where F tx is the transmit carrier frequency of the transmitting AD936X, F rx is the receive carrier frequency of the receiving AD936X, and t is time.

7. The OFDM frequency offset compensation method based on radio frequency agile transceiver according to claim 6, characterized in that: The formula for adjusting through the radio frequency agile transceiver AD936X is as follows: ε=RXLO-TXLO Wherein, TXLO is the frequency of AD936X local oscillator of the sending end, and RXLO is the frequency of AD936X local oscillator of the receiving end.

8. A radio frequency agile transceiver based OFDM frequency offset compensation system for implementing the radio frequency agile transceiver based OFDM frequency offset compensation method of any of claims 1-7, characterized by: It comprises: A detection module for detecting whether an OFDM signal in a wireless channel comes through a short training sequence in the wireless channel, if the arrival of the OFDM signal in the wireless channel is not detected, the detection is continued; if the arrival of the OFDM signal in the wireless channel is detected, the arctangent module is entered; An arctangent module for calculating the result of arctangent; A frequency offset correction module for judging whether the frequency offset error exceeds the predetermined threshold range through the result of arctangent calculated by the arctangent module, if it is within the threshold range, a success flag signal is returned; if it is outside the threshold range, the frequency of AD936X local oscillator (LO) is adjusted upward or downward according to the sign bit of the arctangent result; at the same time, the AD936X sends a synchronization flag signal to the sending end, after the sending end receives the flag signal, the frequency of AD936X local oscillator (LO) of the modulation end is updated in the opposite direction through the SPI communication protocol, at the same time, the sending end and the receiving end radio frequency agile transceiver are adjusted, so that the frequency offset threshold range is reached, so that the same frequency is generated by the radio frequency agile transceiver AD936X of the sending end and the receiving end, and finally the frequency offset correction is realized.

9. The RF agile transceiver based OFDM frequency offset compensation system of claim 8, wherein: It further comprises: An update parameter module for configuring the new frequency calculated in the frequency offset correction module to the radio frequency agile transceiver AD936X through the SPI communication protocol, so as to complete the update of the frequency of AD936X local oscillator (LO) of the sending end and the receiving end.

10. The RF agile transceiver based OFDM frequency offset compensation system of claim 8, wherein: It further comprises: A feedback gain module for adjusting the frequency of AD936X local oscillator (LO) of the sending end and the receiving end upward or downward each time, so as to finally reach a dynamic balance, so as to eliminate the frequency offset.

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