A device and method for canceling the leakage phase shift of a local oscillator in a communication transceiver

Abstract

The application discloses a kind of suitable for communication transceiver channel local oscillator leakage phase shift cancellation device and method, belong to radio frequency communication technical field.For the problem of existing secondary frequency conversion transceiver channel spur deterioration, dynamic range decline, sensitivity degradation, the application generates and leakage signal amplitude phase adjustable cancellation signal by power division sampling in two-stage local oscillator link respectively, and realizes vector cancellation by power division injection in receiving two-stage intermediate frequency link key node respectively;At the same time, through detection and closed loop iteration algorithm, adaptive matching cancellation signal amplitude and phase, realize local oscillator leakage depth suppression and local oscillator interaction suppression in wide frequency band and wide temperature range.The application can significantly improve the spur performance of secondary frequency conversion system, especially suitable for microwave communication equipment with strict spur and dynamic range index requirements.

Description

Technical Field

[0001] This invention belongs to the field of microwave communication radio frequency front-end technology. Specifically, it relates to a device and method for canceling local oscillator leakage shift in communication transceiver channels. Background Technology

[0002] In 2GHz–18GHz microwave communication transceiver systems, a double-conversion architecture is commonly used to achieve high image rejection and high selectivity. A typical scheme involves: the 2GHz–18GHz radio frequency signal is down-converted once to a 22GHz±0.5GHz intermediate frequency (IF) via a 24GHz–40GHz broadband local oscillator, and then down-converted again to a 1.8GHz±0.5GHz IF via a 23.8GHz point-frequency local oscillator. This architecture effectively processes and selects the radio frequency signal through two-stage frequency conversion and is one of the most widely used receiving schemes in the current microwave communication field.

[0003] However, in this double-conversion architecture, the two local oscillators have high power and operate in frequencies close to the radio frequency (RF) and intermediate frequency (IF) bands. This makes them highly susceptible to leakage to the receiving and IF links via mixer feedthrough, microstrip line coupling, spatial radiation, and cavity coupling, resulting in fixed spurious signals and intermodulation interference. Specifically, the local oscillator leakage signal falls directly into the IF passband, forming strong fixed spurious signals that are difficult to eliminate using conventional filtering methods, severely contaminating the useful signal. Simultaneously, the high-power leakage signal compresses the linearity of the low-noise amplifier and the IF amplifier, leading to a significant decrease in the system's dynamic range. Furthermore, crosstalk exists between the broadband local oscillator and the point-frequency local oscillator, generating additional intermodulation components and further deteriorating the communication error characteristics.

[0004] Traditional shielding layouts and filtering schemes have significant limitations when facing the aforementioned problems. On the one hand, while traditional cavity filters can provide good filtering effects, they suffer from drawbacks such as large size, low space utilization, and high cost, making them unsuitable for applications with strict size and cost requirements. On the other hand, although microstrip filters are smaller and less expensive, their suppression capabilities are limited and they cannot effectively suppress leakage signals. More importantly, traditional schemes struggle to simultaneously suppress multipath leakage from two local oscillators and lack adaptive compensation capabilities, failing to adjust the suppression strategy in real time according to local oscillator frequency switching or operating temperature changes.

[0005] Existing technologies are mostly designed for single-band local oscillator or single-conversion architectures, lacking dedicated solutions for two-stage local oscillator cooperative suppression adapted to 2GHz–18GHz double-conversion architectures. This makes it difficult to meet the stringent requirements of modern communication systems for high spurious emission suppression and high dynamic range. Therefore, developing a device capable of achieving cooperative phase-shift cancellation of two-stage local oscillators and possessing adaptive calibration capabilities has significant engineering application value for improving the spurious emission performance of double-conversion communication systems and enhancing the overall system performance. Summary of the Invention

[0006] The purpose of this invention is to provide a local oscillator leakage phase shift cancellation device and method suitable for communication transceiver channels, mainly to solve the problems of spurious degradation, dynamic range reduction, and sensitivity deterioration in existing secondary frequency conversion transceiver channels.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A local oscillator leakage shift cancellation device suitable for communication transceiver channels, comprising:

[0009] The radio frequency input module is used to filter and select the frequency of external radio frequency input signals from 2GHz to 18GHz, and to filter out out-of-band interference signals.

[0010] The broadband local oscillator module is used to provide the local oscillator signal for the first frequency conversion, and at the same time, it splits one signal to the first-stage frequency conversion cancellation module to generate a cancellation signal;

[0011] The local oscillator module is used to provide the local oscillator signal for the second frequency conversion, and at the same time, it splits one signal to the second-level frequency conversion cancellation module to generate a cancellation signal;

[0012] The first-stage frequency conversion cancellation module is used to complete the first mixing of radio frequency and broadband local oscillator. It sets up a closed-loop vector cancellation branch for broadband local oscillator leakage, detects the first-stage residual leakage power and provides feedback control.

[0013] The two-stage frequency conversion cancellation module is used to complete the secondary mixing of the intermediate frequency and the local oscillator. It sets up a closed-loop vector cancellation branch to address the leakage of the local oscillator and outputs the intermediate frequency signal to the intermediate frequency output detection module.

[0014] The intermediate frequency output detection module is used to output the final received intermediate frequency signal, and at the same time detect the residual point frequency local oscillator leakage power of the secondary link and feed it back to the programmable logic control device.

[0015] A programmable logic controller is used to receive two-stage leakage power detection data, and to iteratively adjust two-stage amplitude and phase control devices in a closed loop to achieve automatic cancellation of leakage from the two-stage local oscillator.

[0016] Furthermore, in this invention, the radio frequency input module includes a 2GHz to 18GHz radio frequency input port and a first frequency selection device; the 2GHz to 18GHz external radio frequency input signal is connected through the 2GHz to 18GHz radio frequency input port and then filtered by the first frequency selection device.

[0017] Furthermore, in this invention, the broadband local oscillator module includes a 24GHz-40GHz broadband source and a first power divider; the 24GHz-40GHz broadband source provides a 24GHz-40GHz signal as a broadband local oscillator signal, and the first power divider performs two power division processing on the 24GHz-40GHz broadband source signal, one for the first mixing and the other for sampling the broadband source local oscillator signal.

[0018] Furthermore, in this invention, the local oscillator module includes a 23.8GHz local frequency source and a third power divider; the 23.8GHz local frequency source is used to provide a 23.8GHz signal as a local oscillator signal; the third power divider is used to perform two power division processing on the 23.8GHz local frequency source signal, one for the second mixing and the other for sampling the local oscillator signal of the local frequency source.

[0019] Furthermore, in this invention, the first-stage frequency conversion cancellation module includes a first mixer, a second frequency selection device, a first combiner, a second power divider, and a first power detection device connected in sequence, as well as a first amplitude and phase control device connected to the first combiner; the first mixer is used to mix a 2GHz to 18GHz radio frequency signal with a 24GHz to 40GHz broadband source local oscillator signal to generate an intermediate frequency signal.

[0020] The second frequency selection device is used to perform frequency selection filtering on the input 22GHz±0.5GHz intermediate frequency signal to filter out part of the local oscillator leakage signal and intermodulation spurious signal;

[0021] The first amplitude and phase control device is used to adjust the amplitude and phase of the 24GHz to 40GHz broadband source sampling signal respectively, and generate corresponding amplitude and phase cancellation signals.

[0022] The first combining device is used to inject the cancellation signal modulated by the first amplitude and phase control device into an intermediate frequency signal link node, so as to achieve vector cancellation with the local oscillator leakage signal of the corresponding path;

[0023] The second power divider is used to perform power division processing on the signal after passing through the first combiner, with one path used for secondary mixing and the other path used for injection into the first power detection device.

[0024] The first power detection device is used to detect the residual local oscillator leakage signal strength at an intermediate frequency, and then convert it into a digital signal to realize the digital processing of the residual local oscillator leakage signal strength.

[0025] Furthermore, in this invention, the secondary frequency conversion cancellation module includes a second mixer, a third frequency selection device, a second combiner, a fourth power divider, and a second power detection device connected in sequence, as well as a second amplitude and phase control device connected to the second combiner; the second mixer is used to mix a 22GHz±0.5GHz intermediate frequency signal with a 23.8GHz point frequency source local oscillator signal to generate two intermediate frequency signals;

[0026] The third frequency selection device is used to perform frequency selection filtering on the output 1.8GHz±0.5GHz intermediate frequency signal to filter out some local oscillator leakage signals and intermodulation spurious signals;

[0027] The second amplitude and phase control device is used to adjust the amplitude and phase of the 23.8GHz point frequency source sampling signal respectively, and generate corresponding amplitude and phase cancellation signals;

[0028] The second combining device is used to inject the cancellation signal modulated by the second amplitude and phase control device into the two intermediate frequency signal link nodes, so as to achieve vector cancellation with the local oscillator leakage signal of the corresponding path;

[0029] The fourth power divider is used to divide the signal after passing through the second combiner, with one output and the other used to inject into the second power detection device.

[0030] The second power detection device is used to detect the residual local oscillator leakage signal strength of the second intermediate frequency, and then convert it into a digital signal to realize the digital processing of the residual local oscillator leakage signal strength.

[0031] Based on the above cancellation device, the present invention also provides a method for cancellation of local oscillator leakage shift in communication transceiver channels, comprising the following steps:

[0032] S1: The reference signal is extracted from the output links of the 24GHz~40GHz broadband local oscillator and the 23.8GHz point frequency local oscillator respectively to generate the cancellation signal;

[0033] S2: The extracted reference signals are input into the corresponding amplitude and phase control devices respectively. The amplitude and phase control devices perform amplitude attenuation and phase shift processing on the reference signals to generate cancellation signals with similar amplitude and opposite phase to the corresponding leakage signals.

[0034] S3: The generated cancellation signal is injected into the first intermediate frequency link node and the second intermediate frequency link node respectively, and vector superposition is performed with the intermediate frequency signal in the combining device to achieve multi-level local oscillator leakage cancellation;

[0035] S4: The residual local oscillator leakage signal power is collected in real time through the first power detection device and the second power detection device, and the analog signal is converted into a digital signal and output to the programmable logic control device.

[0036] S5: The programmable logic controller executes a gradient search algorithm to iteratively adjust the amplitude and phase parameters to the optimal suppression point based on the reported residual leakage signal power value.

[0037] S6: When the local oscillator frequency changes or the operating temperature changes, the system automatically detects abnormal changes in leakage power, triggers the recalibration process, and the programmable logic controller re-executes the gradient search algorithm to update the amplitude and phase adjustment parameters to adapt to the new operating conditions and maintain high spurious suppression performance.

[0038] Furthermore, in this invention, the gradient search algorithm calculates the gradient direction at the current parameter point, updates the amplitude and phase parameters along the gradient direction, and repeats the iteration until the residual leakage power converges to below a preset threshold. After each iteration, the first power detection device and the second power detection device re-detect the residual leakage power and report it, forming a closed-loop control.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The present invention sets up power division sampling branches in the output links of the broadband local oscillator and the point frequency local oscillator respectively. After the sampling signal is adjusted by the amplitude and phase control device, a cancellation signal with similar amplitude and opposite phase to the leakage signal is generated. Vector cancellation is achieved by injecting the signal into the first intermediate frequency link node and the second intermediate frequency link node respectively. This can suppress the leakage signal generated by the two local oscillators through multiple paths such as mixer feedthrough, microstrip line coupling, spatial radiation and cavity coupling, effectively eliminate the fixed spurious components falling into the intermediate frequency passband, and significantly improve the spurious performance of the secondary frequency conversion transceiver system.

[0041] (2) By injecting cancellation signals into key nodes of the two intermediate frequency links, the present invention achieves vector cancellation before the leakage signal enters the subsequent amplifier, effectively reducing the local oscillator leakage power entering the intermediate frequency amplification link, avoiding the compression of the linear operating range of the low noise amplifier and the intermediate frequency amplifier by the high power leakage signal, thereby preventing the system dynamic range from decreasing and ensuring the normal operation capability of the receiving link in the case of large dynamic signals.

[0042] (3) In this invention, the residual local oscillator leakage signal power is collected in real time by a first power detection device and a second power detection device, and the detection results are fed back to the programmable logic control module. The programmable logic control module adjusts the amplitude and phase parameters of the two-stage amplitude and phase control devices in a closed loop based on a gradient search algorithm, so that the cancellation signal always maintains a matching state with the leakage signal with similar amplitude and opposite phase. When the characteristics of the leakage signal change due to local oscillator frequency switching or operating temperature change, the system can automatically detect abnormal changes in residual leakage power and trigger a recalibration process to update the amplitude and phase adjustment parameters to adapt to the new operating conditions, maintaining a stable local oscillator leakage suppression effect across the entire frequency band and wide temperature range.

[0043] (4) This invention uses the vector cancellation principle to replace the traditional cavity filter or microstrip filter scheme. It can achieve deep suppression of local oscillator leakage without relying on high suppression filter devices, avoiding the defects of large size and high cost of cavity filters, and at the same time making up for the shortcomings of insufficient suppression of microstrip filters. The power divider, digitally controlled attenuator, digital phase shifter and power detection device in the device are all miniaturized surface-mount devices with a compact overall structure, which is suitable for microwave communication equipment with strict requirements on size and cost. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0045] Figure 2 This is a structural diagram of the first-stage frequency conversion cancellation module in this invention.

[0046] Figure 3 This is a detailed structural diagram of the two-stage frequency conversion cancellation module in this invention. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0048] like Figure 1 As shown, this invention discloses a local oscillator leakage phase-shift cancellation device suitable for communication transceiver channels. The entire device adopts a double-conversion architecture. The RF input terminal receives external RF signals in the 2GHz to 18GHz frequency band. This signal undergoes frequency selection filtering, two down-conversion processes, and local oscillator leakage cancellation processing in sequence, finally outputting an intermediate frequency signal in the 1.3GHz to 2.3GHz range. In the entire signal processing chain, the local oscillator leakage suppression device achieves deep suppression of primary and secondary local oscillator leakage by setting power division sampling, amplitude and phase adjustment, vector combining, and closed-loop detection modules at key nodes.

[0049] In this embodiment, a 2GHz to 18GHz radio frequency signal enters the first frequency selection device from the radio frequency input terminal. The first frequency selection device performs frequency selection filtering on the radio frequency signal, and its main function is to isolate interference signals outside the radio frequency band and improve the receiving sensitivity of the system. The first frequency selection device uses a multi-channel integrated frequency selection filter, covering the 2GHz to 18GHz frequency band, and maintains an overlap bandwidth of 1GHz between adjacent channels to ensure that the instantaneous bandwidth of each frequency point meets the design requirement of greater than or equal to 1GHz. The radio frequency signal after frequency selection filtering is sent to the radio frequency input port of the first mixer.

[0050] The 24GHz–40GHz broadband local oscillator source, used as the local oscillator signal source for primary frequency conversion, employs an integrated phase-locked loop (PLL) chip in conjunction with a frequency multiplier and filter circuit. The integrated PLL chip selected is the LMX2820, which features ultra-wideband frequency characteristics, covering an output frequency range of 45MHz to 22.6GHz. It incorporates a voltage-controlled oscillator (VCO) from 11GHz to 22.6GHz, eliminating the need for external oscillation components, and also boasts ultra-low phase noise jitter and ultra-fast frequency switching. After generating a broadband source signal of 12GHz–20GHz with a frequency step of 100MHz, the PLL chip performs frequency multiplication using an IML-2040-2E active frequency multiplier chip to generate a broadband frequency-hopping source signal of 24GHz–40GHz with a frequency step of 200MHz. The frequency-multiplied signal is amplified and filtered by an amplifier and a switching filter. The switching filter divides the frequency band into two segments: 24GHz to 30GHz and 30GHz to 40GHz. This is used to filter out the fundamental frequency and third and higher harmonic components, and finally outputs a 24GHz to 40GHz broadband local oscillator signal that meets the system requirements.

[0051] After the 24GHz–40GHz broadband local oscillator signal is output, it enters the first power divider for two-way power division. The first power divider uses a broadband power divider with an operating frequency range covering 18GHz to 40GHz, port isolation better than 20dB, and in-band loss less than 1dB. The first power divider splits the broadband local oscillator signal into two inputs to the first-stage frequency conversion cancellation module: one input is used as the local oscillator input port of the first mixer to perform the first down-conversion operation; the other output is used as a reference signal to the first amplitude and phase control device to generate a cancellation signal.

[0052] like Figure 2 As shown, in the first-stage frequency conversion cancellation module, the first mixer uses a double-balanced mixer to achieve the mixing function of the radio frequency signal and the broadband local oscillator signal. The first mixer uses the IMX-1850A, whose radio frequency port and local oscillator port frequency range covers 18GHz to 40GHz, and the intermediate frequency output port frequency range covers DC to 22GHz. The full-band frequency conversion loss is less than or equal to 8dB, and the port isolation is high with excellent intermodulation spurious performance. The first mixer mixes the 2GHz to 18GHz radio frequency signal with the 24GHz to 40GHz broadband local oscillator signal to generate a first intermediate frequency signal of 22GHz ± 0.5GHz. This first intermediate frequency signal then enters the second frequency selection device for frequency selection and filtering.

[0053] The second frequency selection device uses a ceramic microstrip filter to selectively filter the 22GHz±0.5GHz intermediate frequency signal. Its main function is to filter out part of the local oscillator leakage signal and intermodulation spurious signals. Ceramic microstrip filters have the advantages of small size and low cost, but their suppression is relatively limited and their in-band unevenness is relatively high. Therefore, they need to be used in conjunction with the cancellation device of this invention to achieve deep suppression of local oscillator leakage. The first intermediate frequency signal after frequency selection and filtering is output to the first combining device.

[0054] The first amplitude and phase control device is located in the power-dividing sampling branch of the broadband local oscillator source. It is used to adjust the amplitude and phase of the broadband local oscillator sampled signal, generating a cancellation signal with an amplitude similar to but opposite phase to the leakage signal in the first intermediate frequency link. The first amplitude and phase control device consists of an amplitude control unit and a phase control unit. The amplitude control unit is implemented using a low-phase-shift digitally controlled attenuator, specifically the CNW400402B type, which can perform step attenuation control within the range of 0dB to 31.5dB. The phase control unit is implemented using a digital phase shifter, specifically the CNW418460A type, which is a 6-bit structure and can adjust the phase within the range of 0° to 360° with a step accuracy of 5.625°. The amplitude and phase adjustment range and accuracy design of the first amplitude and phase control device fully considers the frequency band characteristics of the 24GHz to 40GHz broadband source, enabling the generation of a cancellation signal that precisely matches the leakage signal.

[0055] The first combiner is positioned between the second frequency selection device and the second power divider, and is used to inject the cancellation signal modulated by the first amplitude and phase control device into the first intermediate frequency (IF) signal link node. The first combiner uses an HGC157L power divider, with an operating frequency range covering 18GHz to 40GHz, isolation better than 20dB, and in-band loss less than 1dB. The first combiner employs a hybrid microstrip combining structure and capacitive coupling to inject the cancellation signal. This design vector-superimposes the cancellation signal and the first IF signal without affecting the VSWR and insertion loss of the receiving path. The injection loss of the first combiner is controlled within 0.5dB to ensure effective injection of the cancellation signal.

[0056] The first intermediate frequency signal, after passing through the first combining device, enters the second power divider for two-way power division. The second power divider also uses an HGC157L power divider to split the first intermediate frequency signal into two paths: one path is output to the second mixer for the second down-conversion; the other path is output to the first power detection device for power injection detection.

[0057] The first power detection device is located in the sampling branch of the second power divider and is used to detect the residual local oscillator leakage signal strength in the first intermediate frequency link. The first power detection device consists of three parts: an amplification and filtering circuit, a detection and amplitude measurement circuit, and an analog-to-digital converter. The amplification and filtering circuit amplifies the sampled signal with low noise and filters out out-of-band noise to ensure the purity of the detected signal. The detection and amplitude measurement circuit uses a MWJ0009 logarithmic detector, which operates in a frequency range of 15GHz to 45GHz, has a large detection dynamic range, and high sensitivity. The analog-to-digital converter uses a 12-bit analog-to-digital converter to convert the analog signal to a digital signal, achieving a detection dynamic range of 60dB. The first power detection device converts the detected residual local oscillator leakage signal strength into a digital signal and outputs it to the programmable logic controller (PLC) to achieve graded detection of the local oscillator leakage signal in the first intermediate frequency band.

[0058] The 23.8GHz point-frequency local oscillator, serving as the local oscillator signal source for secondary frequency conversion, is also implemented using an integrated phase-locked loop (PLL) chip paired with a frequency multiplier and filter circuit. The integrated PLL chip is also the LMX2820, which generates an 11.9GHz point-frequency source signal. This signal is then multiplied by an IML-2040-2E active frequency multiplier chip to produce a 23.8GHz point-frequency source signal. The multiplied signal is then amplified and filtered by an amplifier and a bandpass filter to remove the fundamental frequency of 11.9GHz and higher harmonics (35.7GHz and above), ultimately outputting a 23.8GHz point-frequency local oscillator signal that meets the system requirements.

[0059] After the 23.8GHz local oscillator signal is output, it enters the third power divider for secondary power division. The third power divider uses an HGC157L power divider to split the local oscillator signal into two inputs to the secondary frequency conversion cancellation module: one input is used as the local oscillator input port of the second mixer to realize the second down-conversion; the other input is used as a reference signal to be output to the second amplitude and phase control device to generate a cancellation signal.

[0060] like Figure 3 As shown, in the two-stage frequency conversion cancellation module, the second mixer also uses a double-balanced mixer to achieve the mixing function of the first intermediate frequency signal and the local oscillator signal. The second mixer uses the IMX-0626A, whose RF port and local oscillator port frequency range covers 6GHz to 26GHz, and the intermediate frequency output port frequency range covers DC to 6GHz. The full-band frequency conversion loss is less than or equal to 8dB, and the port isolation is high with excellent intermodulation spurious performance. The second mixer mixes the 22GHz±0.5GHz first intermediate frequency signal with the 23.8GHz local oscillator signal to generate a 1.8GHz±0.5GHz second intermediate frequency signal. This second intermediate frequency signal then enters the third frequency selection device for frequency selection and filtering.

[0061] The third frequency selection device uses an HGC171-1.8A bandpass filter to selectively filter the 1.8GHz±0.5GHz intermediate frequency signal. This third frequency selection device features miniaturization, high suppression, low loss, and in-band flatness, effectively filtering out some local oscillator leakage signals and intermodulation spurious signals. The second intermediate frequency signal, after frequency selection and filtering, is output to the second combiner.

[0062] The second phase control device is located in the power-dividing sampling branch of the local oscillator source. It is used to adjust the amplitude and phase of the sampled signal from the local oscillator source, generating a cancellation signal with an amplitude similar to but opposite phase to the leakage signal in the second intermediate frequency link. The second phase control device also consists of an amplitude control unit and a phase control unit. The specific component selection is the same as the first phase control device, using a CNW400402B digitally controlled attenuator and a CNW418460A digital phase shifter. The design of the second phase control device fully considers the frequency band characteristics of the 23.8GHz local oscillator source, enabling it to generate a cancellation signal that precisely matches the leakage signal.

[0063] The second combiner is located between the third frequency selection device and the fourth power divider, and is used to inject the cancellation signal modulated by the second amplitude and phase control device into the second intermediate frequency signal link node. The second combiner also uses an HGC157L power divider, employing a microstrip combiner structure and a hybrid capacitive coupling method to inject the cancellation signal. The design of the second combiner ensures vector superposition of the cancellation signal and the second intermediate frequency signal, with injection loss controlled within 0.5dB.

[0064] The second intermediate frequency signal, after passing through the second combiner, enters the fourth power divider for two-way power splitting. The fourth power divider also uses an HGC157L power divider to split the second intermediate frequency signal into two paths: one path is used as the final intermediate frequency output to the subsequent circuit, with an output frequency range of 1.3GHz to 2.3GHz; the other path is output to the second power detection device for injected power detection.

[0065] The second power detection device is located after the fourth power divider and is used to detect the residual local oscillator leakage signal strength in the second intermediate frequency link. The circuit composition of the second power detection device is exactly the same as that of the first power detection device, consisting of an amplification and filtering circuit, a detection and amplitude measurement circuit, and an analog-to-digital converter. It uses an MWJ0009 logarithmic detector and a 12-bit analog-to-digital converter to achieve graded detection of the local oscillator leakage signal in the second intermediate frequency band. The second power detection device converts the detected residual local oscillator leakage signal strength into a digital signal and outputs it to the programmable logic controller.

[0066] The programmable logic controller (PLC) is electrically connected to the first power detection device, the second power detection device, the first amplitude-phase control device, and the second amplitude-phase control device, and is the core control unit of the entire local oscillator leakage suppression system. The PLC uses an EG4A20NG88I7 field-programmable gate array (FPGA), which has abundant logic resources and high-speed processing capabilities, enabling the implementation of relatively complex control algorithms. The main functions of the PLC include: receiving digitized information of the residual local oscillator leakage signal power output from the first and second power detection devices; calculating the optimal amplitude-phase adjustment parameters based on the digitized information using a gradient search algorithm; and outputting the amplitude-phase adjustment control signal to the first and second amplitude-phase control devices to perform closed-loop adjustment of the amplitude and phase of the cancellation signal.

[0067] The gradient search algorithm built into the programmable logic controller (PLC) is the core algorithm for achieving adaptive cancellation. The specific execution steps of this algorithm are as follows: First, initial values ​​for the amplitude and phase parameters are set, typically with the attenuation set to an intermediate value and the phase set to 0°. Then, the gradient direction is calculated based on the residual leakage power value reported by the detector, determined by the partial derivative of the residual power with respect to the amplitude and phase parameters. Next, the amplitude and phase parameters are updated along the gradient direction, i.e., the attenuation and phase offset are adjusted along the gradient descent direction. These steps are iteratively executed until the residual leakage power reaches a preset convergence threshold. When the local oscillator frequency changes or the operating temperature changes, the system automatically detects abnormal changes in leakage power, triggering a recalibration process. The PLC then re-executes the gradient search algorithm, updating the amplitude and phase adjustment parameters to adapt to the new operating conditions.

[0068] In actual operation, the local oscillator leakage shift cancellation method of the present invention first performs an initial calibration after the system is powered on. The programmable logic controller (PLC) controls the first and second phase control devices to set the parameters to the initial state, and then starts the gradient search algorithm for iterative search. After the initial calibration is completed, the system enters the normal operating state. The first and second power detection devices monitor the residual local oscillator leakage power in real time and report the monitoring data to the PLC. The PLC determines whether the current cancellation effect meets the requirements based on the monitoring data. If the residual power is lower than the preset threshold, the current parameters remain unchanged; if the residual power is higher than the preset threshold, the gradient search algorithm is re-executed for parameter optimization.

[0069] When the local oscillator frequency changes, the frequency and phase characteristics of the leakage signal change, rendering the original amplitude and phase parameters unsuitable for the new operating frequency. At this time, the residual leakage power detected by the detector will increase significantly. The programmable logic controller (PLC) automatically detects this change and triggers a recalibration process, searching for the optimal amplitude and phase parameters based on the new local oscillator frequency. Similarly, when the operating temperature changes significantly, the phase and amplitude characteristics of the device will drift with temperature, leading to a deterioration in the cancellation effect. The PLC monitors changes in residual leakage power and automatically triggers a temperature compensation calibration process, updating the amplitude and phase adjustment parameters to compensate for the effects of temperature drift.

[0070] The working principle of this invention is based on the physical principle of vector cancellation. When the leakage signal and the cancellation signal are superimposed in the combining device, if the amplitudes of the two signals are equal and their phases are opposite, the combined signal is zero, achieving complete cancellation. Since the amplitude and phase of the leakage signal are affected by various factors such as local oscillator power, device characteristics, and temperature changes, it is necessary to track the changes in the leakage signal in real time through closed-loop detection and iterative adjustment, and adjust the amplitude and phase of the cancellation signal to maintain a relationship of equal amplitude and opposite phase with the leakage signal.

[0071] In the specific hardware implementation, the power divider sampling branch extracts a certain proportion of power from the local oscillator output signal as a reference. The sampling proportion is determined based on the estimated strength of the leakage signal, typically ranging from 1 / 10 to 1 / 100 of the local oscillator output power. After amplitude attenuation and phase shifting by the amplitude and phase control device, a cancellation signal is generated. The amplitude attenuation is adjusted inversely based on the leakage signal strength detected by the detector, and the phase shift is set to 180° plus the phase shift of the leakage signal, thereby achieving vector cancellation between the cancellation signal and the leakage signal.

[0072] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A device for canceling local oscillator leakage shift in communication transceiver channels, characterized in that, include: The radio frequency input module is used to filter and select the frequency of external radio frequency input signals from 2GHz to 18GHz, and to filter out out-of-band interference signals. The broadband local oscillator module is used to provide the local oscillator signal for the first frequency conversion, and at the same time, it splits one signal to the first-stage frequency conversion cancellation module to generate a cancellation signal; The local oscillator module is used to provide the local oscillator signal for the second frequency conversion, and at the same time, it splits one signal to the second-level frequency conversion cancellation module to generate a cancellation signal; The first-stage frequency conversion cancellation module is used to complete the first mixing of radio frequency and broadband local oscillator. It sets up a closed-loop vector cancellation branch for broadband local oscillator leakage, detects the first-stage residual leakage power and provides feedback control. The two-stage frequency conversion cancellation module is used to complete the secondary mixing of the intermediate frequency and the local oscillator. It sets up a closed-loop vector cancellation branch to address the leakage of the local oscillator and outputs the intermediate frequency signal to the intermediate frequency output detection module. The intermediate frequency output detection module is used to output the final received intermediate frequency signal, and at the same time detect the residual point frequency local oscillator leakage power of the secondary link and feed it back to the programmable logic control device. A programmable logic controller is used to receive two-stage leakage power detection data, and to iteratively adjust two-stage amplitude and phase control devices in a closed loop to achieve automatic cancellation of leakage from the two-stage local oscillator.

2. The device for canceling local oscillator leakage shift in a communication transceiver channel according to claim 1, characterized in that, The radio frequency input module includes a 2GHz to 18GHz radio frequency input port and a first frequency selection device; after the 2GHz to 18GHz external radio frequency input signal is connected through the 2GHz to 18GHz radio frequency input port, it is filtered by the first frequency selection device.

3. A device for canceling local oscillator leakage shift in a communication transceiver channel according to claim 2, characterized in that, The broadband local oscillator module includes a 24GHz-40GHz broadband source and a first power divider; the 24GHz-40GHz broadband source provides a 24GHz-40GHz signal as a broadband local oscillator signal, and the first power divider performs two power division processing on the 24GHz-40GHz broadband source signal, one for the first mixing and the other for sampling the broadband source local oscillator signal.

4. A device for canceling local oscillator leakage shift in a communication transceiver channel according to claim 3, characterized in that, The local oscillator module includes a 23.8GHz local frequency source and a third power divider; the 23.8GHz local frequency source is used to provide a 23.8GHz signal as the local oscillator signal; the third power divider is used to perform two power division processing on the 23.8GHz local frequency source signal, one for the second mixing and the other for sampling the local oscillator signal of the local frequency source.

5. A device for canceling local oscillator leakage shift in a communication transceiver channel according to claim 4, characterized in that, The first-level frequency conversion cancellation module includes a first mixer, a second frequency selector, a first combiner, a second power divider, and a first power detection device connected in sequence, as well as a first amplitude and phase control device connected to the first combiner. The first mixer is used to mix a 2GHz to 18GHz radio frequency signal with a 24GHz to 40GHz broadband source local oscillator signal to generate an intermediate frequency signal; The second frequency selection device is used to perform frequency selection filtering on the input 22GHz±0.5GHz intermediate frequency signal to filter out part of the local oscillator leakage signal and intermodulation spurious signal; The first amplitude and phase control device is used to adjust the amplitude and phase of the 24GHz to 40GHz broadband source sampling signal respectively, and generate corresponding amplitude and phase cancellation signals. The first combining device is used to inject the cancellation signal modulated by the first amplitude and phase control device into an intermediate frequency signal link node, so as to achieve vector cancellation with the local oscillator leakage signal of the corresponding path; The second power divider is used to perform power division processing on the signal after passing through the first combiner, with one path used for secondary mixing and the other path used for injection into the first power detection device. The first power detection device is used to detect the residual local oscillator leakage signal strength at an intermediate frequency, and then convert it into a digital signal to realize the digital processing of the residual local oscillator leakage signal strength.

6. A device for canceling local oscillator leakage shift in a communication transceiver channel according to claim 5, characterized in that, The secondary frequency conversion cancellation module includes a second mixer, a third frequency selection device, a second combiner, a fourth power divider, and a second power detection device connected in sequence, as well as a second amplitude and phase control device connected to the second combiner; the second mixer is used to mix a 22GHz±0.5GHz intermediate frequency signal with a 23.8GHz point frequency source local oscillator signal to generate a second intermediate frequency signal; The third frequency selection device is used to perform frequency selection filtering on the output 1.8GHz±0.5GHz intermediate frequency signal to filter out some local oscillator leakage signals and intermodulation spurious signals; The second amplitude and phase control device is used to adjust the amplitude and phase of the 23.8GHz point frequency source sampling signal respectively, and generate corresponding amplitude and phase cancellation signals; The second combining device is used to inject the cancellation signal modulated by the second amplitude and phase control device into the two intermediate frequency signal link nodes, so as to achieve vector cancellation with the local oscillator leakage signal of the corresponding path; The fourth power divider is used to divide the signal after passing through the second combiner, with one output and the other used to inject into the second power detection device. The second power detection device is used to detect the residual local oscillator leakage signal strength of the second intermediate frequency, and then convert it into a digital signal to realize the digital processing of the residual local oscillator leakage signal strength.

7. A method for canceling local oscillator leakage shift in a communication transceiver channel, characterized in that, Based on the cancellation device according to any one of claims 1 to 6, the process includes the following steps: S1: The reference signal is extracted from the output links of the 24GHz~40GHz broadband local oscillator and the 23.8GHz point frequency local oscillator respectively to generate the cancellation signal; S2: The extracted reference signals are input into the corresponding amplitude and phase control devices respectively. The amplitude and phase control devices perform amplitude attenuation and phase shift processing on the reference signals to generate cancellation signals with similar amplitude and opposite phase to the corresponding leakage signals. S3: The generated cancellation signal is injected into the first intermediate frequency link node and the second intermediate frequency link node respectively, and vector superposition is performed with the intermediate frequency signal in the combining device to achieve multi-level local oscillator leakage cancellation; S4: The residual local oscillator leakage signal power is collected in real time through the first power detection device and the second power detection device, and the analog signal is converted into a digital signal and output to the programmable logic control device. S5: The programmable logic controller executes a gradient search algorithm to iteratively adjust the amplitude and phase parameters to the optimal suppression point based on the reported residual leakage signal power value. S6: When the local oscillator frequency changes or the operating temperature changes, the system automatically detects abnormal changes in leakage power, triggers the recalibration process, and the programmable logic controller re-executes the gradient search algorithm to update the amplitude and phase adjustment parameters to adapt to the new operating conditions and maintain high spurious suppression performance.

8. A method for canceling local oscillator leakage shift in a communication transceiver channel according to claim 7, characterized in that, The gradient search algorithm calculates the gradient direction at the current parameter point, updates the amplitude and phase parameters along the gradient direction, and repeats the iteration until the residual leakage power converges to below the preset threshold. After each iteration, the first power detection device and the second power detection device re-detect the residual leakage power and report it, forming a closed-loop control.

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