High-isolation full-duplex transceiver system and control method

Abstract

The invention belongs to the technical field of full-duplex communication, and particularly discloses a high-isolation full-duplex transceiver system and a control method.The system comprises a transmitting module, a receiving module and a full-duplex baseband module, the transmitting module comprises a power amplifier module and a first oscillator, the power amplifier module is connected with the full-duplex baseband module, and the first oscillator is connected with the receiving module; an intermediate frequency signal transmitted by the full duplex baseband module enters the power amplifier module, is mixed with a signal with a frequency f4 generated by the first oscillator, and is up-converted to a frequency f3; the receiving module comprises a second oscillator and a low-noise amplifier module, the second oscillator is connected with the low-noise amplifier module, a receiving antenna of the receiving module receives the signal and inputs the signal into the low-noise amplifier module for frequency mixing with the signal of the second oscillator, the signal is down-converted to frequency f2, and the signal enters the full-duplex baseband module for data processing. By adopting the technical scheme, based on each module, the influence of self-interference leaked by a transmitting link on a receiving link is completely avoided, and the design complexity of any system is not increased.

Description

Technical Field

[0001] This invention belongs to the field of full-duplex communication technology and relates to a high-isolation full-duplex transceiver system and control method. Background Technology

[0002] Full-duplex communication technology is a key technology that enables simultaneous transmission and reception of signals on the same frequency. Compared to traditional half-duplex systems, full-duplex communication can nearly double the system's spectrum utilization rate with the same spectrum resources, and is therefore considered an important development direction for next-generation communication.

[0003] However, since the transmitter and receiver operate on the same frequency, the high-power signal transmitted will couple to the receiver through various means (such as antenna coupling, transceiver leakage, etc.), thereby generating self-interference. The strength of this interference signal is usually much higher than the expected received signal, which severely limits the receiver's sensitivity and the communication performance of the entire system.

[0004] Currently, academia and industry have proposed various self-interference cancellation techniques, mainly including antenna isolation, analog domain cancellation, and digital domain cancellation, to reduce the impact of self-interference. These methods can suppress self-interference signals to a certain extent, enabling the receiver to recover the desired received signal.

[0005] However, due to limitations in transceiver hardware such as nonlinear distortion, phase noise, limited dynamic range, and other non-ideal factors, current technologies cannot completely eliminate self-interference. Residual self-interference may still exceed the receiver's noise floor, affecting system stability and reliability. Therefore, how to suppress self-interference coupling at its source, especially solving the leakage problem of self-interference signals within the transceiver, has become a key technical challenge in full-duplex system design. Summary of the Invention

[0006] The purpose of this invention is to provide a high-isolation full-duplex transceiver system and control method to solve the problem of self-interference signal leakage inside the transceiver.

[0007] To achieve the above objectives, the basic solution of the present invention is: a high-isolation full-duplex transceiver system, comprising a transmitting module, a receiving module, and a full-duplex baseband module;

[0008] The transmitting module includes a power amplifier module and a first oscillator. The first oscillator is connected to the power amplifier module, and the power amplifier module is connected to a full-duplex baseband module. The frequency of the signal transmitted by the full-duplex baseband module is intermediate frequency f1. After the intermediate frequency signal enters the power amplifier module, it is mixed with a signal of frequency f4 generated by the first oscillator and up-converted to frequency f3. Then, it enters the transmitting antenna of the transmitting module for transmission, where f3 = f1 + f4.

[0009] The receiving module includes a second oscillator and a low-noise amplifier module. The second oscillator is connected to the low-noise amplifier module, and the low-noise amplifier module is connected to the full-duplex baseband module. When the receiving antenna of the receiving module receives a signal with frequency f3, it is input into the low-noise amplifier module and mixed with a signal with frequency f5 generated by the second oscillator. The signal is then down-converted to frequency f2 and enters the full-duplex baseband module for data processing. f2 = f3 - f5, f4 ≠ f5.

[0010] The working principle and beneficial effects of this basic solution are as follows: This technical solution designs the transmitted and received signals at different frequencies in the full-duplex baseband module, and incorporates mixing modules in the power amplifier and low-noise amplifier to mix the signals, completely avoiding leakage of self-interference signals on the baseband module circuit board. Furthermore, it does not increase the complexity of the system design, which is beneficial for practical applications.

[0011] Furthermore, the power amplifier module is provided with two transmit mixing channels, each of which includes a first transmit bandpass filter, an upconverter mixer, a second transmit bandpass filter, an RF driver amplifier, a third transmit bandpass filter, a power amplifier, a high-power amplifier, a SAW filter, and an RF coupler connected in sequence.

[0012] The input terminal of the first transmit bandpass filter is connected to the full-duplex baseband module;

[0013] The first oscillator generates a local oscillator signal and connects it to the up-converter mixer via a power divider.

[0014] The power amplifier module has a simple structure and is easy to use.

[0015] Furthermore, the transmit power divider evenly distributes the local oscillator signal with a frequency of f4 to the upper and lower mixing channels;

[0016] The first transmit bandpass filter is used to select the intermediate frequency signal with frequency f1 and suppress out-of-band interference;

[0017] The upconversion mixer mixes the intermediate frequency signal with frequency f1 and the local oscillator signal with frequency f4 to generate a signal with frequency f3.

[0018] The second transmit bandpass filter is used to select the signal with frequency f3 and filter out the image frequency and spurious signals generated by mixing;

[0019] The radio frequency driver amplifier is used to amplify the signal at frequency f3 and provide sufficient driving power for the subsequent power amplifier.

[0020] The third transmit bandpass filter is used to clean up the amplified signal at frequency f3 and suppress out-of-band noise.

[0021] The power amplifier boosts the signal power to near the target transmission power;

[0022] The high-power amplifier amplifies the signal power to a final output power of 1W;

[0023] The SAW filter is used to suppress harmonics and spurious signals, ensuring the purity of the output signal spectrum.

[0024] The radio frequency coupler is used to detect the output power and provide feedback for power monitoring or closed-loop protection settings of various devices to meet the requirements of the transmission signal.

[0025] Furthermore, the low-noise amplifier module includes two receiving mixer channels, each receiving mixer channel comprising a low-noise amplifier, a first RF drive amplifier, a first receiving bandpass filter, a second RF drive amplifier, a second receiving bandpass filter, a downconverter mixer, a third receiving bandpass filter, and a fourth receiving bandpass filter connected in sequence.

[0026] The second oscillator generates a local oscillator signal and connects it to the down-conversion mixer via a receiving power divider.

[0027] The output of the fourth receiving bandpass filter is connected to the full-duplex baseband module.

[0028] The low-noise amplifier module has simple device connections and is easy to operate.

[0029] Furthermore, the receiving power divider evenly distributes the local oscillator signal with a frequency of f5 to the upper and lower mixing channels.

[0030] The first receiving low-noise amplifier is used to amplify the received signal at frequency f3, thereby improving system sensitivity and reducing the overall noise figure.

[0031] The first receiving bandpass filter is used to select a signal with a frequency of f3 and filter out out-of-band interference and harmonics.

[0032] The first and second RF driver amplifiers are used to amplify the signal at frequency f3 and provide sufficient drive power for the subsequent mixer.

[0033] The second receiving bandpass filter cleans up the amplified signal at frequency f3 and suppresses out-of-band noise;

[0034] The downconverter mixer mixes the signal with frequency f3 with the local oscillator with frequency f5 and outputs an intermediate frequency signal with frequency f2.

[0035] The third receiving bandpass filter is used to select the intermediate frequency signal with a frequency of f2 and filter out the image frequency and spurious signals in the mixing products.

[0036] The fourth receiving bandpass filter is used to clean the intermediate frequency signal at frequency f2 to ensure the purity of the output signal spectrum.

[0037] Based on the connection structure of each device, the required signal is obtained.

[0038] Furthermore, it also includes two independent metal cavities, with the power amplifier module and the low-noise amplifier module respectively placed in the two metal cavities.

[0039] By isolating the power amplifier and low-noise amplifier separately, leakage of self-interference at frequency f3 is reduced, achieving a high degree of isolation design for the full-duplex transceiver.

[0040] The present invention also provides a high-isolation full-duplex transceiver control method based on the full-duplex transceiver system described in the present invention, comprising the following steps:

[0041] The frequency of the full-duplex baseband module's transmitted signal is designed to be intermediate frequency f1. After the intermediate frequency signal enters the power amplifier module, it is mixed with the signal with frequency f4 generated by the first oscillator and up-converted to the required frequency f3. The signal then enters the transmitting antenna for transmission, satisfying f3 = f1 + f4.

[0042] The receiving antenna receives a signal with frequency f3. The signal with frequency f3 enters the low noise amplifier module and is mixed with a signal with frequency f5 generated by the second oscillator. It is then down-converted to the required frequency f2 and enters the full-duplex baseband module for data processing, satisfying f2 = f3 - f5.

[0043] The method of this invention designs a high isolation method for full-duplex transceivers, which completely avoids the impact of self-interference from the transmission link leakage on the receiving link, and does not increase the complexity of the system design. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the high isolation full-duplex transceiver system of the present invention;

[0045] Figure 2 This is a schematic diagram of the power amplifier module of the high-isolation full-duplex transceiver system of the present invention;

[0046] Figure 3 This is a schematic diagram of the low-noise amplifier module of the high-isolation full-duplex transceiver system of the present invention. Detailed Implementation

[0047] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0048] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0049] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0050] This invention discloses a high-isolation full-duplex transceiver system, such as... Figure 1 As shown, it includes a transmitting module, a receiving module, and a full-duplex baseband module. The full-duplex baseband module can adopt existing module structures for processing baseband signals.

[0051] The transmitting module includes a power amplifier module and a first oscillator. The first oscillator is electrically connected to the power amplifier module, which is also electrically connected to a full-duplex baseband module. The full-duplex baseband module transmits a signal at an intermediate frequency (IF) f1. This IF signal enters the power amplifier module and is mixed with a signal at frequency f4 generated by the first oscillator, then up-converted to frequency f3, which is then transmitted through the transmitting antenna of the transmitting module. f3 = f1 + f4. Preferably, the first oscillator can be a STUW81200 local oscillator generator, which can generate a stable 4053MHz local oscillator signal for the mixer.

[0052] The receiving module includes a second oscillator and a low-noise amplifier module. The second oscillator is electrically connected to the low-noise amplifier module, which is electrically connected to a full-duplex baseband module. When the receiving antenna of the receiving module receives a signal at frequency f3, it is input to the low-noise amplifier module and mixed with a signal at frequency f5 generated by the second oscillator. This signal is then down-converted to frequency f2 and enters the full-duplex baseband module for data processing. f2 = f3 - f5, f4 ≠ f5. Preferably, the second oscillator is a STUW81200 local oscillator generator, which generates a stable 3450MHz local oscillator signal, which is then provided to the mixer.

[0053] This invention designs the transmitted and received signals at different frequencies in the full-duplex baseband module, and incorporates a mixing module in the power amplifier and low-noise amplifier to mix the signals, completely avoiding leakage of self-interference signals on the baseband module circuit board.

[0054] In a preferred embodiment of the present invention, such as Figure 2 As shown, the power amplifier module has two transmit mixing channels. Each transmit mixing channel includes a first transmit bandpass filter, an upconverter mixer, a second transmit bandpass filter, an RF driver amplifier, a third transmit bandpass filter, a power amplifier, a high-power amplifier, a SAW filter, and an RF coupler, connected in sequence. The two channels correspond to the vertically polarized signal and the horizontally polarized signal, respectively, allowing for flexible adjustment of the transmit signal polarization.

[0055] The input of the first transmit bandpass filter is electrically connected to the full-duplex baseband module, and the first oscillator generates a local oscillator signal and is electrically connected to the upconverter mixer through the transmit power divider.

[0056] In a preferred embodiment of the present invention, a transmit power divider evenly distributes the local oscillator signal with a frequency of f4 to the upper and lower mixing channels. The transmit power divider can be an LC-Divider, which evenly distributes the 4053MHz local oscillator signal to the upper and lower mixing channels.

[0057] The first transmit bandpass filter is used to pass the intermediate frequency (IF) signal at frequency f1 and suppress out-of-band interference. The first transmit bandpass filter can be a B5159, which can pass a 1747MHz IF signal and suppress out-of-band interference.

[0058] An upconversion mixer mixes an intermediate frequency (IF) signal (f1) with a local oscillator (LO) signal (f4) to generate a signal with a frequency (f3). An example upconversion mixer is the LTC5549 IUDB#TRMPBF, which can mix a 1747MHz IF signal with a 4053MHz LO signal to generate a 5800MHz signal.

[0059] The second transmit bandpass filter is used to select the signal at frequency f3, filtering out image frequencies and spurious signals generated by mixing. The second transmit bandpass filter can be an M.B5800-150, capable of selecting 5800MHz signals and filtering out image frequencies and spurious signals generated by mixing.

[0060] The RF driver amplifier, such as the QPL9504TR7, is used to amplify signals at a frequency of f3 (e.g., 5800MHz) to provide sufficient drive power for the subsequent power amplifier.

[0061] The third transmit bandpass filter, which can be a 5515BP15C975E, is used to further clean up the amplified signal at frequency f3 and suppress out-of-band noise.

[0062] Power amplifiers, such as the SE5004L, boost the signal power to near the target transmit power.

[0063] High-power amplifiers (Final Power Amplifiers), such as the GTAH35012PD, amplify the signal power to a final output power of 1W.

[0064] SAW (Surface Acoustic Wave Filter), including but not limited to SHSA6Z5.8AB, is used to suppress harmonics and spurious signals, ensuring the purity of the output signal spectrum.

[0065] Radio frequency couplers, such as RF50-10T0525, are used to detect output power and provide feedback for power monitoring or closed-loop protection.

[0066] In a preferred embodiment of the present invention, such as Figure 3 As shown, the low-noise amplifier module includes two receiving mixer channels, each receiving mixer channel comprising a low-noise amplifier, a first RF drive amplifier, a first receiving bandpass filter, a second RF drive amplifier, a second receiving bandpass filter, a downconverter mixer, a third receiving bandpass filter, and a fourth receiving bandpass filter connected in sequence.

[0067] The second oscillator generates a local oscillator signal and is electrically connected to the down-conversion mixer via a receiving power divider. The output of the fourth receiving bandpass filter is electrically connected to the full-duplex baseband module.

[0068] In a preferred embodiment of the present invention, a receiving power divider (such as an LC-Divider) evenly distributes a local oscillator signal with a frequency of f5 (such as 3450MHz) to the upper and lower mixing channels.

[0069] The first receiver low-noise amplifier is used to amplify the received signal at frequency f3, improving system sensitivity and reducing the overall noise figure. The first receiver low-noise amplifier can be the SKY16602-632LF, amplifying the received 5800MHz signal.

[0070] The first receiving bandpass filter (such as M.B5800-150) is used to select signals with a frequency of f3 (such as 5800MHz) and filter out out-of-band interference and harmonics.

[0071] The first and second RF driver amplifiers are used to amplify the signal at frequency f3, providing sufficient drive power for the subsequent mixer. The first and second RF driver amplifiers are preferably, but not limited to, QPL9504TR7, and are used to amplify the 5800MHz signal.

[0072] The second receiving bandpass filter (such as 5515BP15C975E) cleans up the amplified signal at frequency f3 and suppresses out-of-band noise.

[0073] A downconversion mixer mixes a signal with frequency f3 with a local oscillator with frequency f5, outputting an intermediate frequency (IF) signal with frequency f2. Examples of downconversion mixers include the LTC5549 IUDB#TRMPBF, which mixes a 5800MHz signal with a 3450MHz local oscillator, outputting a 2350MHz IF signal.

[0074] The third receiving bandpass filter (such as B5133) is used to select the intermediate frequency signal with a frequency of f2 (such as 2350MHz) and filter out the image frequency and spurious signals in the mixing products.

[0075] The fourth receiving bandpass filter (such as LFCG-3800+) is used to further clean the intermediate frequency signal at frequency f2 (such as 2350MHz) to ensure the purity of the output signal spectrum.

[0076] In a preferred embodiment of the present invention, the high-isolation full-duplex transceiver system further includes two independent metal cavities, with the power amplifier module and the low-noise amplifier module respectively housed within the two metal cavities. The power amplifier and the low-noise amplifier should be isolated separately within the transceiver and shielded by the metal cavities to reduce the impact of signal leakage at frequency f3.

[0077] The signals with frequencies f1 and f2 are in different frequency bands, which completely avoids the interference of the signal before it enters the power amplifier in the transmission link on the signal after it is output by the low noise amplifier in the receiving link, thus achieving high isolation of the full-duplex transceiver.

[0078] To further verify this, actual measurements were conducted, and the results are shown in Table 1:

[0079] Table 1. Measured Results

[0080] Transmit power 20dBm 30dBm Isolation (not using the design method proposed in this invention) 128dB 119dB Isolation (using the design method proposed in this invention) 107dB 96dB

[0081] In this practical test, the proposed design method was not used, which involved setting the transmit and receive signals of the full-duplex baseband module to the same frequency, i.e., f1 = f2. It can be seen that the proposed design method can increase the isolation by approximately 20 dB under different transmit powers, effectively improving the communication performance of the full-duplex transceiver.

[0082] This invention also provides a high-isolation full-duplex transceiver control method based on the system described herein, which completely avoids the impact of self-interference from transmit link leakage on the receive link, and does not increase the complexity of system design. The high-isolation full-duplex transceiver control method includes the following steps:

[0083] The frequency of the full-duplex baseband module's transmitted signal is designed to be intermediate frequency f1. After the intermediate frequency signal enters the power amplifier module, it is mixed with the signal with frequency f4 generated by the first oscillator and up-converted to the required frequency f3. The signal then enters the transmitting antenna for transmission, satisfying f3 = f1 + f4.

[0084] The receiving antenna receives a signal with frequency f3. The signal with frequency f3 enters the low noise amplifier module and is mixed with a signal with frequency f5 generated by the second oscillator. It is then down-converted to the required frequency f2 and enters the full-duplex baseband module for data processing, satisfying f2 = f3 - f5.

[0085] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A high-isolation full-duplex transceiver system, characterized in that, Includes a transmitter module, a receiver module, and a full-duplex baseband module; The transmitting module includes a power amplifier module and a first oscillator. The first oscillator is connected to the power amplifier module, and the power amplifier module is connected to a full-duplex baseband module. The frequency of the signal transmitted by the full-duplex baseband module is intermediate frequency f1. After the intermediate frequency signal enters the power amplifier module, it is mixed with a signal of frequency f4 generated by the first oscillator and up-converted to frequency f3. Then, it enters the transmitting antenna of the transmitting module for transmission, where f3 = f1 + f4. The receiving module includes a second oscillator and a low-noise amplifier module. The second oscillator is connected to the low-noise amplifier module, and the low-noise amplifier module is connected to the full-duplex baseband module. When the receiving antenna of the receiving module receives a signal with frequency f3, it is input into the low-noise amplifier module and mixed with a signal with frequency f5 generated by the second oscillator. The signal is then down-converted to frequency f2 and enters the full-duplex baseband module for data processing. f2 = f3 - f5, f4 ≠ f5.

2. The high isolation full-duplex transceiver system as described in claim 1, characterized in that, The power amplifier module has two transmit mixing channels, each of which includes a first transmit bandpass filter, an upconverter mixer, a second transmit bandpass filter, an RF driver amplifier, a third transmit bandpass filter, a power amplifier, a high-power amplifier, a SAW filter, and an RF coupler connected in sequence. The input terminal of the first transmit bandpass filter is connected to the full-duplex baseband module; The first oscillator generates a local oscillator signal and connects it to the up-converter mixer via a power divider.

3. The high isolation full-duplex transceiver system as described in claim 2, characterized in that, The power divider distributes the local oscillator signal with a frequency of f4 evenly to the upper and lower mixing channels. The first transmit bandpass filter is used to select the intermediate frequency signal with frequency f1 and suppress out-of-band interference; The upconversion mixer mixes the intermediate frequency signal with frequency f1 and the local oscillator signal with frequency f4 to generate a signal with frequency f3. The second transmit bandpass filter is used to select the signal with frequency f3 and filter out the image frequency and spurious signals generated by mixing; The radio frequency driver amplifier is used to amplify the signal at frequency f3 and provide sufficient driving power for the subsequent power amplifier. The third transmit bandpass filter is used to clean up the amplified signal at frequency f3 and suppress out-of-band noise. The power amplifier boosts the signal power to near the target transmission power; The high-power amplifier amplifies the signal power to a final output power of 1W; The SAW filter is used to suppress harmonics and spurious signals, ensuring the purity of the output signal spectrum. The radio frequency coupler is used to detect the output power and provide feedback for power monitoring or closed-loop protection.

4. The high isolation full-duplex transceiver system as described in claim 1, characterized in that, The low-noise amplifier module includes two receiving mixer channels, each receiving mixer channel comprising a low-noise amplifier, a first RF drive amplifier, a first receiving bandpass filter, a second RF drive amplifier, a second receiving bandpass filter, a downconverter mixer, a third receiving bandpass filter, and a fourth receiving bandpass filter connected in sequence. The second oscillator generates a local oscillator signal and connects it to the down-conversion mixer via a receiving power divider. The output of the fourth receiving bandpass filter is connected to the full-duplex baseband module.

5. The high isolation full-duplex transceiver system as described in claim 4, characterized in that, The receiving power divider evenly distributes the local oscillator signal with frequency f5 to the upper and lower mixing channels. The first receiving low-noise amplifier is used to amplify the received signal at frequency f3, thereby improving system sensitivity and reducing the overall noise figure. The first receiving bandpass filter is used to select a signal with a frequency of f3 and filter out out-of-band interference and harmonics. The first and second RF driver amplifiers are used to amplify the signal at frequency f3 and provide sufficient drive power for the subsequent mixer. The second receiving bandpass filter cleans up the amplified signal at frequency f3 and suppresses out-of-band noise; The downconverter mixer mixes the signal with frequency f3 with the local oscillator with frequency f5 and outputs an intermediate frequency signal with frequency f2. The third receiving bandpass filter is used to select the intermediate frequency signal with a frequency of f2 and filter out the image frequency and spurious signals in the mixing products. The fourth receiving bandpass filter is used to clean the intermediate frequency signal at frequency f2 to ensure the purity of the output signal spectrum.

6. The high isolation full-duplex transceiver system as described in claim 1, characterized in that, It also includes two independent metal cavities, with the power amplifier module and the low-noise amplifier module respectively placed in the two metal cavities.

7. A high-isolation full-duplex transceiver control method based on the full-duplex transceiver system according to any one of claims 1-6, characterized in that, Includes the following steps: The frequency of the full-duplex baseband module's transmitted signal is designed to be intermediate frequency f1. After the intermediate frequency signal enters the power amplifier module, it is mixed with the signal with frequency f4 generated by the first oscillator and up-converted to the required frequency f3. The signal then enters the transmitting antenna for transmission, satisfying f3 = f1 + f4. The receiving antenna receives a signal with frequency f3. The signal with frequency f3 enters the low noise amplifier module and is mixed with a signal with frequency f5 generated by the second oscillator. It is then down-converted to the required frequency f2 and enters the full-duplex baseband module for data processing, satisfying f2 = f3 - f5.

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