Bridge-based frequency-division duplex balanced low noise amplifier and radio frequency receiver

Abstract

The application discloses a kind of based on bridge's frequency division duplex balanced low noise amplifier and radio frequency receiver, including bridge A and bridge B, bridge A and bridge B are both double-frequency bridge, port P1 of bridge A receives signal, port P4 is connected to load, port P2 and port P3 are connected with the input end of low noise amplifier respectively, the output end of low noise amplifier is connected with the port P5 of bridge B and port P8 respectively, port P6 outputs frequency f1 signal, P7 port can output frequency f2 signal or P6 port outputs frequency f2 signal, P7 port outputs frequency f1 signal;The output port of bridge A is opposite phase, and the output port of bridge B is same phase;Under the work of two bridges, duplex effect is realized.Compared with the design of traditional balanced duplex low noise amplifier, additional conventional duplexer is not needed to realize duplex function, so as to improve system integration and reduce component cost, improve system performance.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency communication technology, and particularly relates to a frequency division duplex balanced low-noise amplifier and radio frequency receiver based on a bridge. Background Technology

[0002] Current RF receiver designs commonly employ duplexers to achieve precise separation and efficient transmission of dual-frequency signals. In multi-band receiver systems, the duplexer, through the coordinated operation of its integrated transmit and receive filters, effectively suppresses spurious signals from non-target frequency bands, accurately allocating signals from different frequency bands to their respective independent transmit and receive channels. This ingenious frequency-segmentation-based design enables the RF front-end to simultaneously support the transmission of high-frequency signals and the reception of low-frequency signals, or to achieve concurrent processing of multiple communication frequency bands. The core role of a duplexer in a system is mainly reflected in the following three aspects: First, transmit / receive isolation. It utilizes the frequency selectivity of a bandpass filter to strictly physically isolate the high-power signal of the transmit link from the weak signal of the receive link, effectively avoiding reverse interference of the transmitted signal to the receiver front end. Second, path optimization. In space-constrained application scenarios such as cellular base stations, the duplexer completes the transmit and receive tasks of multi-band signals by multiplexing the same antenna, significantly reducing the number of antennas and lowering system complexity. Third, anti-aliasing processing. Combined with the duplexing mechanism in frequency division duplex (FDD) mode, the duplexer utilizes the spacing between frequency bands to protect bandwidth, effectively suppressing adjacent channel interference and image frequency interference, and ensuring the spectral purity of each signal path.

[0003] However, the use of duplexers also presents several challenges. First, the addition of a duplexer typically complicates the system architecture, requiring more components for interconnection and debugging. Second, duplexers increase system costs, especially in high-frequency and high-power applications where their design and manufacturing are expensive. Furthermore, the size and volume of the duplexer also increase the overall size of the RF receiver, impacting the miniaturization requirements of the system. More importantly, the duplexer itself may introduce additional signal loss, particularly in high-frequency signal transmission, where it can lead to insertion loss, thus affecting the overall system performance.

[0004] As the core of a receiver, the loss of the pre-amplifier (LNA) can greatly affect the noise performance of the system. In order to improve the noise performance of LNA, integrated solutions have become an important direction of research and development in recent years. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a functionally integrated dual-frequency duplex balanced low-noise amplifier. Its core concept lies in achieving dual-frequency duplex functionality through a clever coupler design, eliminating the need for an additional traditional duplexer, thereby improving the integration and performance of the RF receiver and achieving circuit miniaturization.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a frequency division duplex balanced low-noise amplifier based on a bridge, comprising bridge A and bridge B, both of which are dual-frequency bridges. Port P1 of bridge A receives signals, port P4 is connected to a load, and ports P2 and P3 are respectively connected to the input terminals of the low-noise amplifier. The output terminals of the low-noise amplifier are respectively connected to ports P5 and P8 of bridge B. Port P6 outputs a frequency f1 signal, and port P7 can output a frequency f2 signal, or port P6 outputs a frequency f2 signal and port P7 outputs a frequency f1 signal. The output ports of bridge A are out of phase, while the output ports of bridge B are in the same phase.

[0007] Furthermore, the bridge A operates at frequencies f1 and f2. Dual-frequency 90-degree and -90-degree phase-difference coupling is achieved by loading four quarter-wavelength microstrip lines with a 90-degree coupler. Two half-wavelength @f0 microstrip lines TL1 and two half-wavelength @f0 microstrip lines TL3 are connected to form a traditional 90-degree bridge. The four quarter-wavelength @f0 microstrip lines TL2 crosswise to connect ports P1 and P3, and ports P2 and P4. Simultaneously, ports P1 and P2, and ports P4 and P3 are connected via half-wavelength @f0 microstrip lines TL1, and ports P1 and P4, and ports P2 and P3 are connected via half-wavelength @f0 microstrip lines TL3.

[0008] Furthermore, when the input port is port P1 and the circuit operates at frequencies f1 and f2, at operating frequency f1, there is a 90-degree phase difference between the through port P2 and the coupling port P3 of bridge A, and at operating frequency f2, there is a -90-degree phase difference between the through port P2 and the coupling port P3 of bridge A. Alternatively, at operating frequency f1, there is a -90-degree phase difference between the through port P2 and the coupling port P3 of bridge A, and at operating frequency f2, there is a 90-degree phase difference between the through port and the coupling port of bridge A.

[0009] Furthermore, f1 and f2, as well as the bandwidth of the operating frequency band, can all be controlled by adjusting the impedance of the three microstrip lines: half-wavelength @f0 microstrip line TL1, quarter-wavelength @f0 microstrip line TL2, and half-wavelength @f0 microstrip line TL3.

[0010] Furthermore, bridge B uses a 90-degree coupler to load four quarter-wavelength open-circuit stubs to achieve dual-frequency 90-degree phase-difference coupling. Two quarter-wavelength @f0 microstrip lines TL2 and two quarter-wavelength @f0 microstrip lines TL3 are connected as shown in the figure to form a conventional 90-degree bridge. Four quarter-wavelength @f0 microstrip lines TL1 are loaded between the input port and the quarter-wavelength @f0 microstrip lines TL2 and TL3.

[0011] Furthermore, bridge B is a dual-frequency bridge with operating frequencies of f1 and f2. At operating frequency f1, there is a 90-degree phase difference between the through port P6 and the coupling port P7 of bridge B. At operating frequency f2, there is a 90-degree phase difference between the through port P6 and the coupling port P7 of bridge B.

[0012] Furthermore, when the received signal frequency at port P1 is f1 & f2, ports P6 and P7 output frequency signals f1 and f2 respectively, or frequency signals f2 and f1 respectively.

[0013] Furthermore, in the two operating frequencies of bridge A and bridge B, f 1A with f 1B Same, f 2A with f 2B same.

[0014] Furthermore, the low-noise amplifier employs a two-stage transistor amplifier circuit.

[0015] The present invention can also provide an RF receiver that employs the above-mentioned bridge-based frequency division duplex balanced low-noise amplifier.

[0016] Compared with existing technologies, the present invention has at least the following beneficial effects: The present invention implements a balanced amplifier circuit using two different dual-frequency bridges A and B, and two identical low-noise amplifiers (LNAs). Simultaneously, based on the phase characteristics of bridges A and B, the balanced amplifier integrates duplex functionality. This significantly improves the performance of the RF receiver, reduces system complexity, and provides a new technical path for the realization of future multi-band and high-frequency communication systems. The dual-frequency duplex balanced low-noise amplifier design in the present invention integrates dual-frequency duplex functionality in the 90-degree coupler section, eliminating the complex design of traditional duplexers. Compared with traditional balanced duplex low-noise amplifiers… The design eliminates the need for an additional traditional duplexer to achieve duplex functionality. Removing the duplexer significantly improves system integration, resulting in a simpler overall design and lower costs. The balanced design enhances the interference immunity of the low-noise amplifier, mitigating the impact of circulator mismatch on the pre-amplifier balanced low-noise amplifier, thus improving system stability and interference immunity, and ensuring efficient and stable communication. This design supports simultaneous processing of signals from multiple frequency bands, improving spectrum utilization and adapting to the multi-band requirements of modern wireless communication systems. Furthermore, the removal of the duplexer makes the entire RF receiver design more compact, reducing internal system complexity and the number of components, thereby improving system maintainability and reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a frequency division duplex balanced low-noise amplifier circuit topology based on a bridge circuit.

[0019] Figure 2 This is a circuit diagram of the bridge A used in this invention.

[0020] Figure 3 The S-parameter curves of the four ports of bridge A used in this invention are shown.

[0021] Figure 4 The phase difference curves between ports P2 and P3 of bridge A used in this invention are shown.

[0022] Figure 5 This is a schematic diagram of the bridge circuit B used in this invention.

[0023] Figure 6 The S-parameter curves of the four ports of bridge B used in this invention are shown.

[0024] Figure 7 The phase difference curves of ports P6 and P7 of bridge B used in this invention are shown.

[0025] Figure 8 This is the gain curve of a frequency division duplex balanced low-noise amplifier based on a bridge.

[0026] Figure 9 The noise profile is for a frequency division duplex balanced low-noise amplifier based on a bridge circuit.

[0027] Figure 10 Simulation results of the four-port noise figure for a frequency division duplex balanced low-noise amplifier.

[0028] Figure 11 This is a block diagram of an RF receiver based on the frequency division duplex balanced low-noise amplifier described in this invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The foregoing and other technical contents, features, and effects of this invention will be clearly presented in the following detailed description of the specific embodiments with reference to the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by this invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] This invention provides a frequency division duplex balanced low-noise amplifier based on a bridge circuit, comprising bridge A and bridge B, both of which are dual-frequency bridges. Port P1 of bridge A receives signals, port P4 is connected to a load, and ports P2 and P3 are respectively connected to the input terminals of the low-noise amplifier. The output terminals of the low-noise amplifier are respectively connected to ports P5 and P8 of bridge B. Port P6 outputs a frequency f1 signal, and port P7 can output a frequency f2 signal, or port P6 outputs a frequency f2 signal and port P7 outputs a frequency f1 signal. The output ports of bridge A are out of phase, while the output ports of bridge B are in the same phase.

[0032] Bridge A is based on a dual-frequency 90-degree circuit with a 180-degree phase difference between ports 2 and 3, meaning they are out of phase. Bridge B is also based on a dual-frequency 90-degree circuit with a 0-degree phase difference between ports 2 and 3, meaning they are in the same direction. This circuit operates at two frequencies, f1 and f2, which are chosen here as 1.58 GHz and 2.68 GHz. The specific circuit framework is as follows... Figure 1 As shown, port P1 of bridge A receives the signal, port P4 is connected to the load, ports P2 and P3 are connected to the input terminals of a low noise amplifier (LNA) respectively, the output terminals of the LNA are connected to the input ports P5 and P8 of bridge B respectively, port P6 can output a signal of frequency f1, and port P8 can output a signal of frequency f2, thus achieving a duplex effect under the operation of the two bridges.

[0033] Figure 1 Specifically, a bridge A circuit structure that can achieve dual-frequency coupling with port 2 and port 3 having a phase difference of ±90 degrees is given as follows: Figure 2 As shown:

[0034] This includes ports P1, P2, P3, and P4. Assuming port P1 is the input port, then port P2 is a through port, port P3 is a coupling port, and port P4 is an isolation port. This circuit uses a conventional 90-degree coupler loaded with four quarter-wavelength microstrip lines to achieve dual-frequency 90-degree and -90-degree phase difference coupling. Two half-wavelength @f0 microstrip lines TL1 and TL3 are connected as shown in the diagram to form a conventional 90-degree bridge. The four quarter-wavelength @f0 microstrip lines TL2 crosswise to connect ports P1 and P3, and ports P2 and P4. Simultaneously, ports P1 and P2, and ports P4 and P3 are connected via half-wavelength @f0 microstrip lines TL1, and ports P1 and P4, and ports P2 and P3 are connected via half-wavelength @f0 microstrip lines TL3. Figure 1 As shown, this coupler is completely symmetrical. When the input port is port P1 and the circuit operates at frequencies f1 and f2, equal power distribution is achieved between ports P2 and P3. Simultaneously, when bridge A operates at frequency f1, there is a 90-degree phase difference between ports P2 and P3; when bridge A operates at frequency f2, there is a -90-degree (270-degree) phase difference between ports P2 and P3. The operating frequencies f1 and f2 are related to f0, and f1, f2, and the bandwidth of the operating frequency band can all be freely controlled by adjusting the impedances of the three microstrip lines: half-wavelength @f0 microstrip line TL1, quarter-wavelength @f0 microstrip line TL2, and half-wavelength @f0 microstrip line TL3.

[0035] To verify the feasibility of the aforementioned bridge A, the circuit structure was simulated. The simulation results of the four-port S-parameters are as follows: Figure 3As shown in the figure, the circuit effectively achieves dual-frequency equal power sharing. Within the operating frequency bands f1 and f2, circuit S11 is less than -20dB, indicating good matching characteristics. The transmission characteristics S at ports 2 and 3 of the circuit are also good. 21 With S 31 The sizes are almost identical, around -3.39dB, and the insertion loss is around 0.39dB, which is mainly due to dielectric loss.

[0036] The phase difference between the through port 2 and the coupling port P3 of bridge A is as follows: Figure 4 As shown in the figure, the phase difference between the through coupling port 2 and the coupling port 3 is 270 degrees (-90 degrees) at the operating frequency f1 and 90 degrees at the operating frequency f2. The effect is good and the expected design effect is achieved.

[0037] Alternatively, at operating frequency f1, there is a 90-degree phase difference between the through port 2 and the coupling port 3 of bridge A, and at operating frequency f2, there is a -90-degree phase difference between the through port 2 and the coupling port 3 of bridge A.

[0038] The circuit of bridge B is as follows Figure 5 As shown, this includes ports P5, P6, P7, and P8. Assuming port P5 is the input, port P6 is a through port, port P7 is a coupling port, and port P8 is an isolation port. This circuit uses a conventional 90-degree coupler with four quarter-wavelength open-circuit stubs to achieve dual-frequency 90-degree phase-difference coupling. Two quarter-wavelength @f0 microstrip lines TL2 and two quarter-wavelength @f0 microstrip lines TL3 are connected as shown to form a conventional 90-degree bridge. Four quarter-wavelength @f0 microstrip lines TL1 are loaded between the input port and the quarter-wavelength @f0 microstrip lines TL2 and TL3, as shown. Figure 1 As shown, this coupler is completely symmetrical. When the input port is port P5, the circuit operates at frequencies f1 and f2, achieving equal power distribution between ports P6 and P7. Simultaneously, when bridge B operates at frequency f1, there is a 90-degree (-270-degree) phase difference between ports P5 and P6; when bridge B operates at frequency f2, there is also a 90-degree (-270-degree) phase difference between ports P5 and P6. The operating frequencies f1 and f2 of this circuit are related to f0 and can be controlled by adjusting the impedances of the three microstrip lines: quarter-wavelength @f0 microstrip line TL1, quarter-wavelength @f0 microstrip line TL2, and quarter-wavelength @f0 microstrip line TL3.

[0039] Figure 6The figure shows the simulation results of the four-port S-parameters of coupler B. As can be seen from the figure, the circuit achieves good dual-frequency equal power splitting. Within the operating frequency bands f1 and f2, the circuit S11 is less than -20dB, indicating good matching characteristics. The transmission characteristics S11 between ports P6 and P2 in the circuit are also good. 21 With S 31 The magnitudes are almost the same, around -3.41dB, and the insertion loss is around 0.41dB, which is mainly due to dielectric loss.

[0040] The phase difference between the through port P6 and the coupling port P7 of bridge B is as follows: Figure 7 As shown in the figure, the phase difference between the through coupling port 6 and the coupling port 7 is -270 degrees (90 degrees) at both the operating frequency f1 and the operating frequency f2, which is good and achieves the expected design effect.

[0041] Figure 8 This is the schematic diagram of a low-noise amplifier (LNA) circuit. To demonstrate the feasibility of the aforementioned theory, this design employs a broadband low-noise amplifier covering f1 and f2. This amplifier uses a two-stage transistor amplification design, where RF... in The input microstrip line is connected to the low-noise input matching network L1 and C1, then to the gate of transistor 1, with the middle section connected to the gate bias circuit. The drain of transistor 1's output terminal is connected to C2, R1, C3, C4, L2, and R2, with the middle section connected to the drain bias circuit. C3, L2, R2, and C4 form an interstage matching network. To achieve higher gain and smoother adjustment, its output terminal is connected to the gate of transistor 2, with the middle section connected to the gate bias circuit of transistor 2. The drain of transistor 2's output terminal is connected to C5, R3, C6, and L3, with the middle section connected to the drain bias circuit of transistor 2. C6 and L3 form the output matching network, connected to the RF output microstrip line RF... out Connected. The output matching network is used to ensure the reflection coefficient at port P2 is less than -10dB. While adjusting gain flatness, C2, R1, C5, and R3 improve amplifier stability. Additionally, high-impedance lines are added to the sources of both transistors to further enhance transistor stability. L g1 L d1 L b1 L c1 The yoke inductor is used to simulate the RF signal entering the DC path, and each DC path has two bypass capacitors to filter out low-frequency noise interference. Simulations were performed using ADS software. The simulation results show that the low-noise amplifier can achieve a gain of over 21dB in the wide bandwidth range of 1.3GHz-2.9GHz, with a simulated noise figure of 0.4dB-0.6dB, demonstrating good performance.

[0042] Figure 9The simulation results of the four-port S-parameters of the frequency division duplex balanced low-noise amplifier are presented, through the ingenious simulation of the two previous dual-frequency bridge circuits and LNA, such as... Figure 9 As shown in (a), S 21 With S 31 The results show that at the operating frequency band f1, port P6 outputs with a circuit gain of 20.9dB. At the operating frequency band f2, port P7 outputs with a circuit gain of 20.1dB, indicating good port balance and achieving the expected duplex effect. Figure 9 As shown in (b), S 11 The values ​​are all less than -10dB within the operating frequency band, indicating good port matching.

[0043] Figure 10 The simulation results for the four-port noise figure of the frequency division duplex balanced low-noise amplifier are shown. The results show that at the operating frequency band f1, the noise figure of the circuit is 0.72dB when port P6 is output. At the operating frequency band f2, the noise figure of the circuit is 0.96dB when port P7 is output, indicating that the circuit has good duplex performance. Furthermore, due to the integration of system functions, the use of duplexers is reduced, and the system gain and noise performance are both good.

[0044] Example 2: Based on the use of a bridge-based frequency division duplex balanced low-noise amplifier, this invention can also provide an RF receiver that does not require a duplexer during operation, thereby improving the performance of the RF receiver and reducing system complexity. (Reference) Figure 11 The radio frequency receiver includes a dual-band antenna, a filter, a bridge-based frequency division duplex balanced low-noise amplifier, and a load. The antenna is connected in sequence to port P1 of the switching filter and the bridge-based frequency division duplex balanced low-noise amplifier, and the load is connected to port P4.

[0045] In summary, the frequency division duplex balanced low-noise amplifier based on a bridge circuit provided by this invention includes bridge A and bridge B, both of which are dual-frequency bridges. Port P1 of bridge A receives the signal, port P4 is connected to the load, and ports P2 and P3 are respectively connected to the input terminals of the low-noise amplifier. The output terminals of the low-noise amplifier are respectively connected to ports P5 and P8 of bridge B. Port P6 outputs a signal at frequency f1, and port P7 can output a signal at frequency f2, or port P6 outputs a signal at frequency f2 and port P7 outputs a signal at frequency f1. The output ports of bridge A are out of phase, while the output ports of bridge B are in the same phase. Through the ingenious application of a coupler, a traditional duplexer is replaced, reducing the dependence on the duplexer and achieving dual-frequency duplex performance. Compared with traditional dual-frequency receiver architectures, this integrated design not only reduces system cost and size but also reduces interconnection and insertion losses, lowers receiver pre-stage noise, and improves signal gain. Through this innovative design, the RF receiver can achieve higher integration and lower power consumption while improving system performance. By eliminating the duplexer, the entire system becomes more compact and can be adapted to a wider range of applications, such as wireless communication, radar systems, and satellite communication.

[0046] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A frequency-division duplex balanced low-noise amplifier based on a bridge circuit, characterized in that, The bridge circuit includes bridge A and bridge B, both of which are dual-frequency bridges. Bridge A's port P1 receives the signal, port P4 is connected to the load, and ports P2 and P3 are connected to the inputs of a low-noise amplifier (LNA). The outputs of the LNA are connected to ports P5 and P8 of bridge B, respectively. Port P6 outputs a signal at frequency f1, and port P7 outputs a signal at frequency f2, or vice versa. The output ports of bridge A are out of phase, while the output ports of bridge B are in phase. Bridge A operates at frequencies f1 and f2. Dual-frequency 90-degree and -90-degree phase difference coupling is achieved by loading four quarter-wavelength microstrip lines with a 90-degree coupler. Two half-wavelength @f0 microstrip lines TL1 and two half-wavelength @f0 microstrip lines TL3 are connected to form a traditional 90-degree bridge. Four quarter-wavelength @f0 microstrip lines TL2 cross to connect ports P1 and P3, and ports P2 and P4. Simultaneously, ports P1 and P2, and ports P4 and P3 are connected via half-wavelength @f0 microstrip lines TL1, and ports P1 and P4, and ports P2 and P3 are connected via half-wavelength @f0 microstrip lines TL3. Bridge B uses four quarter-wavelength open-circuit stubs loaded with 90-degree couplers to achieve dual-frequency 90-degree phase-difference coupling. Two quarter-wavelength @f0 microstrip lines TL2 and two quarter-wavelength @f0 microstrip lines TL3 are connected to form a traditional 90-degree bridge. Four quarter-wavelength @f0 microstrip lines TL1 are loaded between the input ports and the quarter-wavelength @f0 microstrip lines TL2 and TL3.

2. The frequency division duplex balanced low-noise amplifier based on a bridge as described in claim 1, characterized in that, When the input port is port P1, and the circuit operates at frequencies f1 and f2, at operating frequency f1, there is a 90-degree phase difference between the through port and the coupled port of bridge A, and at operating frequency f2, there is a -90-degree phase difference between the through port and the coupled port of bridge A. Alternatively, at operating frequency f1, there is a -90-degree phase difference between the through port and the coupled port of bridge A, and at operating frequency f2, there is a 90-degree phase difference between the through port and the coupled port of bridge A.

3. The frequency division duplex balanced low-noise amplifier based on a bridge as described in claim 1, characterized in that, f1 and f2, as well as the ground bandwidth of the operating frequency band, are all controlled by adjusting the impedance of three microstrip lines: half-wavelength @f0 microstrip line TL1, quarter-wavelength @f0 microstrip line TL2, and half-wavelength @f0 microstrip line TL3.

4. The frequency division duplex balanced low-noise amplifier based on a bridge as described in claim 1, characterized in that, Bridge B is a dual-frequency bridge with operating frequencies of f1 and f2. At operating frequency f1, there is a 90-degree phase difference between the through port and the coupling port of Bridge B. At operating frequency f2, there is a 90-degree phase difference between the through port and the coupling port of Bridge B.

5. A frequency division duplex balanced low-noise amplifier based on a bridge as described in claim 1, characterized in that, When the received signal frequency at port P1 is f1 & f2, ports P6 and P7 output frequency signals f1 and f2 respectively, or output frequency signals f2 and f1 respectively.

6. The frequency division duplex balanced low-noise amplifier based on a bridge as described in claim 1, characterized in that, In the two operating frequencies of bridge A and bridge B, f 1A with f 1B Same, f 2A with f 2B same.

7. A frequency division duplex balanced low-noise amplifier based on a bridge as described in claim 1, characterized in that, The low-noise amplifier uses a two-stage transistor amplifier circuit.

8. A radio frequency receiver, characterized in that, The frequency division duplex balanced low-noise amplifier based on a bridge as described in any one of claims 1-7 is adopted.

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