A radio frequency protection circuit with integrated limiting threshold control and energy recovery functions

Abstract

The present invention discloses a radio frequency protection circuit with integrated limiting threshold control and energy recovery functions, belonging to the technical field of reflective limiters. The circuit includes a radio frequency input terminal, a circulator, a branch line directional coupler, a bias and limiting network, an energy recovery unit, a load terminal, and a radio frequency output terminal. The energy recovery unit includes a high-power rectifier and a pass-through filter. The circulator and branch line directional coupler reflect overload signals, and the reflected power is introduced into the high-power rectifier via the circulator to achieve radio frequency energy recovery. The bias and limiting network includes a GaN-based Schottky diode and a symmetrical bias network, which are used to achieve limiting protection and adjustable limiter threshold functions. The present invention realizes the organic unification of high-power radio frequency signal limiting protection and reflected energy reuse, improves the functional integration and energy utilization efficiency of the radio frequency system, and is suitable for protection scenarios of high-power front-end circuits such as radar communication and satellite navigation.

Description

Technical Field

[0001] The present invention belongs to the technical field of reflective limiters, and in particular relates to a radio frequency protection circuit integrating limit threshold control and energy recovery functions. Background Art

[0002] RF / microwave front-end systems play a key role in radar, communications, navigation and other fields. With the improvement of system integration and the increase of power levels, the problem of instantaneous strong signal interference faced by RF front-end components is becoming increasingly serious, which can easily cause damage to the subsequent receiving circuits. For this reason, limiters, as core components of front-end protection, are widely used at the input end of the signal chain to limit the input power to a safe range. In the existing technology, limiters are mainly divided into two categories: absorptive limiters and reflective limiters. Absorptive limiters convert overload energy into heat energy for dissipation; while reflective limiters reflect overload signals back to the signal source, thereby preventing overload energy from entering the receiving system. They have the advantages of simple structure and low power consumption, and are widely used in radar systems, satellite communications and navigation terminals.

[0003] However, existing reflective limiters have two major technical deficiencies:

[0004] 1. Unmanaged reflected energy leads to wasted resources and potential interference: Most reflective limiters focus solely on protecting downstream circuits, often ignoring and leaving unprocessed the high-power energy reflected back to the source. This not only wastes electromagnetic energy but also potentially damages source-side devices (such as antennas, switches, and circulators), compromising overall system reliability.

[0005] 2. The limiter threshold is not adjustable and lacks system adaptability: The turn-on threshold of a traditional limiter is typically determined by the device's inherent conduction threshold (such as a Si- or GaAs-based PIN diode or Schottky diode). This threshold is typically 15dBm to 20dBm, making it difficult to achieve the requirements of high-sensitivity systems (less than 0dBm) and perform dynamic adjustment. With the diversification of application scenarios, such as high-sensitivity receiving systems and short-range, high-power ranging systems, new requirements have been placed on the limiter threshold to include multiple power levels and adjustable settings.

[0006] In summary, although the existing reflective limiters are relatively mature in terms of protection functions, they still have obvious shortcomings in energy management and threshold control capabilities, making it difficult to meet the development trend of "low-carbon energy saving, multi-functional integration, and intelligent control" in modern communication and radar systems.

[0007] In order to respond to the design trend of green and low-carbon electronic systems and meet the RF protection needs of multiple scenarios and multiple power levels, there is an urgent need for an integrated RF protection circuit structure that has the ability to adjust the limiting threshold and effectively collect and reuse reflected energy. Summary of the Invention

[0008] In response to the above-mentioned problems existing in the prior art, the present invention proposes a radio frequency protection circuit that integrates limit threshold control and energy recovery functions. The circuit has a reasonable design, solves the shortcomings of the prior art, and has good effects.

[0009] In order to achieve the above-mentioned purpose of the invention, the following technical solutions are adopted:

[0010] A radio frequency protection circuit with integrated clipping threshold control and energy recovery functions includes a radio frequency input terminal, a circulator, a branch line directional coupler, a bias and clipping network, an energy recovery unit, a load terminal, and a radio frequency output terminal. The energy recovery unit includes a high-power rectifier and a pass-through filter.

[0011] The circulator and branch line directional coupler reflect the overload signal, and the reflected power is introduced into the high-power rectifier through the circulator to achieve RF energy recovery; the bias and limiting network includes a GaN-based Schottky diode and a symmetrical bias network, which is used to achieve limiting protection and adjustable limiter threshold functions.

[0012] Furthermore, the first port of the circulator is connected to the radio frequency input terminal, the second port thereof is connected to the branch line directional coupler, and the third port thereof is connected to the high power rectifier via the capacitor C3.

[0013] Furthermore, the branch line directional coupler includes four λ / 4 impedance lines connected in a ring shape, and the characteristic impedances are Z1 to Z4 respectively, satisfying , Z1=Z3;

[0014] The branch line directional coupler has four ports, namely the input end, coupling end, output end and isolation end. The first end of Z1 and Z2 is the input end, which is connected to the second port of the circulator; the first end of Z3 and Z4 is the output end; the second end of Z1 and Z4 is the isolation end, which is connected to the RF output end; the second end of Z2 and Z3 is the coupling end.

[0015] Furthermore, the bias and limiting network includes two GaN-based Schottky diodes D1 and D2 and capacitors C1 and C2, the coupling end of the branch line directional coupler is connected in series with C1 and D1 in sequence, and its output end is connected in series with C2 and D2 in sequence, and the negative electrodes of D1 and D2 are grounded;

[0016] The bias and limiting network also includes a symmetrical bias network, which is composed of bias resistors R1, R2 and bias inductors L1, L2. One end of L1 is connected to the positive electrodes of C1 and D1, and the other end is connected to one end of R1, and the other end of R1 is the X1 end; one end of L2 is connected to the positive electrodes of C2 and D2, and the other end is connected to one end of R2, and the other end of R2 is the X2 end.

[0017] Furthermore, when the input power is lower than the set clipping threshold, that is, the turn-on voltage of D1 and D2, D1 and D2 are not conducting, and the coupling end and output end of the coupler are in an open circuit state. Therefore, the signal is transmitted from the input end of the coupler through Z1 to the isolation end and output from the RF output end.

[0018] When the input power exceeds the set limiting threshold, D1 and D2 are turned on, forming an impedance mismatch. The reflected power at the coupling end and output end of the coupler flows to the input end and isolation end respectively. The reflected power is shown in formula (1), forming a limit on the input end signal. The power output to the isolation end has been limited, and the output is output to the subsequent circuit at a lower power.

[0019] ;(1)

[0020] in, is the incident power, is the reflected power, is the on-resistance of the diode, is the characteristic impedance, =50Ω.

[0021] Furthermore, the limiting threshold is regulated by a symmetrical bias network. By adjusting the resistors R1 and R2 and the applied bias voltage, the conduction threshold of D1 and D2 is controlled. The bias voltage range is -0.3V to +0.3V.

[0022] By increasing the resistance values ​​of R1 and R2, the limiting threshold and limiting level are increased. When a positive voltage is connected to the X1 and X2 terminals, the limiting threshold and limiting level are reduced. When a negative voltage is connected to the X1 and X2 terminals, the limiting threshold and limiting level are increased. The overall limiting threshold is dynamically adjustable from -10dBm to +10dBm.

[0023] Furthermore, the high-power rectifier includes an impedance matching structure Z5, a GaN-based Schottky diode D3 and a λ / 8 branch impedance line Z6 connected in sequence, and Z6 is grounded;

[0024] The straight-through filter includes an impedance matching structure Z7, a λ / 4 branch impedance line Z8, a λ / 2 branch impedance line Z9, and a λ / 8 branch impedance line Z10. One end of Z7 is connected to the negative electrode of D3, and the other end is connected to one end of Z8~Z10 and the load end.

[0025] Furthermore, the power signal reflected from the input end of the coupler is output through the third port of the circulator, first passes through the impedance matching structure Z5, and then enters the GaN-based Schottky diode D3, which rectifies the high-frequency signal into a DC current;

[0026] The rectified DC current is accompanied by higher harmonics. Z8~Z10 in the pass-through filter suppress the fundamental wave, second harmonic and third harmonic respectively. The higher harmonics that are not completely suppressed are reflected back to D3 through Z7 and rectified again. Finally, the DC current is sent to the matching load through the load end, realizing real-time energy recovery and utilization.

[0027] Furthermore, the GaN-based Schottky diodes D1, D2, and D3 are selected as FCR080, with a reverse breakdown voltage of 120V, an on-resistance of 2.5Ω, and a turn-on voltage of approximately 0.45V.

[0028] Beneficial technical effects brought about by the present invention:

[0029] 1. Equipped with adjustable limit threshold function to improve system adaptability and protection accuracy;

[0030] By integrating a GaN diode and a symmetrical bias network into the limiter, this invention achieves a controllable limiting threshold, which can be continuously adjusted from -10dBm to +10dBm. Compared to traditional fixed-threshold limiters, this design better adapts to the varying sensitivity and power handling requirements of different RF systems, improving the accuracy and flexibility of the protection system.

[0031] 2. Introducing energy recovery paths to effectively utilize reflected power and reduce energy waste;

[0032] The present invention integrates an energy rectifier module at the front end of the limiter, uses a circulator to guide the reflected power to the GaN Schottky rectifier diode and outputs it to the load after passing through the filter network, realizing DC energy recovery of the reflected power. Compared with the existing technology of directly dissipating the reflected power, the present invention significantly improves the energy efficiency of the RF system, and the energy recovery efficiency reaches more than 70%. Figure 6 As shown, it meets the requirements of green and low-carbon design.

[0033] 3. High structural integration, reducing the number of components and connection loss, and facilitating modular packaging;

[0034] The present invention integrates the limiter, directional coupler, circulator and energy recovery structure into an integral module, significantly reducing the insertion loss, intermodulation interference and packaging complexity caused by the separation of multiple modules in traditional designs, improving the system's integration level, reliability and manufacturability, and is suitable for miniaturized and modular high-frequency RF front-end systems.

[0035] 4. Use multi-stage wavelength branch filtering to improve rectification efficiency and energy conversion effect;

[0036] The λ / 8, λ / 4, and λ / 2 impedance branches are introduced into the rectifier circuit to suppress harmonics of different orders and reflect them back to the rectifier unit, enabling secondary rectification of the reflected signal. This structure significantly improves the energy conversion efficiency of the rectifier system and avoids energy loss due to complex frequency components.

[0037] 5. Suitable for various high-frequency and high-power application scenarios such as L, C, and X bands;

[0038] The coupler structure, matching impedance design and limiting method adopted in the present invention are applicable to various types of radio frequency systems such as Beidou navigation, radar communication, and electronic countermeasures, and have wide engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the overall structural diagram of the radio frequency protection device in the present invention.

[0040] Figure 2 This is a circuit diagram of the radio frequency protection device of the present invention;

[0041] Among them, 01 is the first port, 02 is the second port, 03 is the third port; 11 is the input port, 12 is the isolation port, 13 is the coupling port, and 14 is the output port.

[0042] Figure 3 Graph showing the characteristics of the GaN-based Schottky diode of the present invention;

[0043] Among them, (a) is the forward conduction characteristic diagram; (b) is the reverse breakdown characteristic diagram.

[0044] Figure 4 Schematic diagram of the threshold and limit level control under different bias voltages in the present invention.

[0045] Figure 5 Schematic diagram of the threshold and limit level control of R1 and R2 at different resistance values ​​in the present invention.

[0046] Figure 6 Schematic diagram of energy recovery efficiency at different frequencies in the present invention.

[0047] Figure 7 Schematic diagram of the maximum power capacity achievable by the radio frequency protection circuit of the present invention. DETAILED DESCRIPTION

[0048] The specific implementation of the present invention will be further described below with reference to specific embodiments:

[0049] A radio frequency protection circuit with integrated limiting threshold control and energy recovery functions, such as Figure 1As shown, it includes a radio frequency input terminal, a circulator, a branch line directional coupler, a bias and limiting network, an energy recovery unit, a load terminal and a radio frequency output terminal, and the energy recovery unit includes a high power rectifier and a straight-through filter;

[0050] The circulator and branch line directional coupler reflect the overload signal, and the reflected power is introduced into the high-power rectifier through the circulator to achieve RF energy recovery; the bias and limiting network includes a GaN-based Schottky diode and a symmetrical bias network to achieve limiting protection and adjustable limiter threshold functions.

[0051] Specifically, if Figure 2 As shown, the first port 01 of the circulator is connected to the radio frequency input terminal, the second port 02 thereof is connected to the branch line directional coupler, and the third port 03 thereof is connected to the high power rectifier via the capacitor C3.

[0052] The branch line directional coupler is a 3dB directional coupler, which includes four λ / 4 impedance lines connected in a ring, with characteristic impedances of Z1 to Z4, respectively, meeting , Z1=Z3, achieving 3dB power division and directivity control. Under normal circumstances, the signal enters from the input end and is mainly output to the output end and coupling end;

[0053] The branch line directional coupler has four ports, namely the input end 11, the isolation end 12, the coupling end 13 and the output end 14. The first ends of Z1 and Z2 are input ends, which are connected to the second port of the circulator; the first ends of Z3 and Z4 are output ends; the second ends of Z1 and Z4 are isolation ends, which are connected to the RF output end; the second ends of Z2 and Z3 are coupling ends, forming a reflection path control structure.

[0054] The external high-power RF signal first enters the first port 01 of the circulator. The circulator guides the signal into the second port 02 in a low-loss manner and connects it to the input end of the branch line directional coupler.

[0055] Specifically, the bias and limiting network includes two GaN-based Schottky diodes D1 and D2 and capacitors C1 and C2, forming a limiting structure at the port. The coupling end of the branch line directional coupler is connected in series with C1 and D1 in sequence, and its output end is connected in series with C2 and D2 in sequence. The negative electrodes of D1 and D2 are grounded.

[0056] The bias and limiting network also includes a symmetrical bias network, consisting of bias resistors R1 and R2 and bias inductors L1 and L2. One end of L1 is connected to the positive terminals of C1 and D1, and the other end is connected to one end of R1, and the other end of R1 is the X1 terminal. One end of L2 is connected to the positive terminals of C2 and D2, and the other end is connected to one end of R2, and the other end of R2 is the X2 terminal. Bias inductors L1 and L2 are used to isolate the bias network from interference from high-frequency RF signals. R1 and R2 are used to limit the bias current and adjust the conduction threshold, and their values ​​generally range from 0Ω to 40Ω.

[0057] Specifically, when the input power is lower than the set clipping threshold, that is, the turn-on voltage of D1 and D2, D1 and D2 are not conducting, and the coupling end and output end of the coupler are in an open circuit state. Therefore, the signal is transmitted from the input end of the coupler through Z1 to the isolation end and output by the RF output end;

[0058] When the input power exceeds the set limiting threshold (i.e., the diode's turn-on voltage, which is 0.45V for GaN SBD diodes), D1 and D2 are turned on, forming an impedance mismatch (50Ω in the normal matching state, and the diode's on-resistance is 2.5Ω, so the overall impedance mismatch occurs). The reflected power at the coupling end and output end of the coupler flows to the input end and the isolation end respectively. The reflected power is shown in Equation (1). At this time, the reflected signal will return to the input end and the isolation end respectively, forming a limit on the input end overload signal, and the power output to the isolation end has been limited. At this time, the output end of the entire system should be the isolation end. The power of this part has been limited by the limiting structure and output to the subsequent circuit at a lower power.

[0059] ;(1)

[0060] in, is the incident power, is the reflected power, is the on-resistance of the diode, is the characteristic impedance, =50Ω.

[0061] Specifically, the clipping threshold is regulated by a symmetrical bias network. By adjusting the resistors R1 and R2 and the applied bias voltage, the conduction thresholds of D1 and D2 are controlled. The bias voltage range is -0.3V to +0.3V.

[0062] By increasing the resistance values ​​of R1 and R2, the clipping threshold and clipping level are increased. When the X1 and X2 terminals are connected to a positive voltage, the clipping threshold and clipping level are reduced. When the X1 and X2 terminals are connected to a negative voltage, the clipping threshold and clipping level are increased. Figure 4 As shown in Figure 2, the overall clipping threshold is dynamically adjustable from -10dBm to +10dBm. Figure 4 and Figure 5 As shown, it adapts to the sensitivity and power protection level requirements of different application scenarios. Since the threshold of the limiter depends on the diode's turn-on voltage, which is generally determined by formula (2), and GaN SBD is generally 0.45V@10mA, its threshold can be adjusted by relying on the resistors (R1 and R2) in each bias network. The threshold can be increased by connecting a higher resistor in series, or reduced by applying a reverse bias voltage.

[0063] ;(2)

[0064] in, represents the limiter threshold, is the diode’s turn-on voltage, The characteristic impedance is 50Ω, and all RF signal paths are matched to the system reference impedance , ensuring optimal standing wave ratio and power transmission efficiency.

[0065] Specifically, the high-power rectifier includes an impedance matching structure Z5, a GaN-based Schottky diode D3, and a λ / 8 branch impedance line Z6 connected in sequence, Z6 is grounded, and Z5 is connected to C3;

[0066] The straight-through filter includes an impedance matching structure Z7, a λ / 4 branch impedance line Z8, a λ / 2 branch impedance line Z9, and a λ / 8 branch impedance line Z10. Z8 is used to suppress the fundamental wave, Z9 is used to suppress the second harmonic, and Z10 is used to suppress the third harmonic. One end of Z7 is connected to the negative electrode of D3, and the other end is connected to one end of Z8 to Z10 and the load end.

[0067] Specifically, the DC signal rectified by D3 is often accompanied by high-order harmonics, and the load collection end hopes to collect the rectified current with maximum efficiency. The power signal reflected back from the input end of the coupler is output through the third port of the circulator and enters the energy recovery unit. It not only effectively rectifies the RF energy, but also reflects the rectified high-order harmonics back to the rectifier diode through the pass-through filter, thereby improving the overall rectification efficiency and finally outputting it to the matching load (such as a battery) to realize DC energy recovery.

[0068] The high-frequency signal passes through the GaN-based Schottky diode D3 and is rectified into a DC current. Under the action of the DC blocking capacitor C3, the rectified DC must flow to the load end and will not flow through the isolator to burn the previous stage devices.

[0069] The rectified DC current is accompanied by high-order harmonics. Z8~Z10 in the pass-through filter suppress the fundamental wave, second harmonic and third harmonic respectively. The high-order harmonics that are not completely suppressed are reflected back to D3 through Z7 and rectified again (after passing through Z7, the harmonic peak is aligned with the phase at D3, which promotes its secondary rectification efficiency), improving the overall rectification efficiency. The overall energy recovery efficiency reaches more than 70%. Figure 6 As shown in the figure, the final DC current is sent to the matching load (such as lithium battery, super capacitor, etc.) through the load end to achieve real-time energy recovery and utilization.

[0070] Specifically, in order to achieve fast response turn-on and high power scenario use, the GaN-based Schottky diodes D1, D2, and D3 are selected as FCR080, with a reverse breakdown voltage of 120V, an on-resistance of 2.5Ω, and a turn-on voltage of approximately 0.45V. Figure 3 The final overall withstand power can reach 100W level, as shown in (a) and (b). Figure 7 As shown, X1 and X2 are +0.2V, resistors R1 and R2 are 15Ω, the clipping level is 2dBm, the threshold is 0dBm, and the withstand power is 50dBm (100W).

[0071] The RF input and output terminals can use SMA, N-type, TNC, BNC, or SSMA connectors. The energy harvesting load terminal can be connected to an impedance-matched energy harvesting device, such as a battery or capacitor.

[0072] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A radio frequency protection circuit integrating limiting threshold control and energy recovery functions, characterized in that: It includes a radio frequency input terminal, a circulator, a branch line directional coupler, a bias and limiting network, an energy recovery unit, a load terminal and a radio frequency output terminal, wherein the energy recovery unit includes a high-power rectifier and a straight-through filter; The circulator and branch line directional coupler reflect the overload signal, and the reflected power is introduced into the high-power rectifier through the circulator to achieve RF energy recovery; the bias and limiting network includes a GaN-based Schottky diode and a symmetrical bias network, which is used to achieve limiting protection and adjustable limiter threshold functions; The first port of the circulator is connected to the RF input terminal, the second port thereof is connected to the branch line directional coupler, and the third port thereof is connected to the high power rectifier via the capacitor C3; The branch line directional coupler includes four λ / 4 impedance lines connected in a ring, and the characteristic impedances are Z1 to Z4 respectively, satisfying , Z1=Z3; The branch line directional coupler has four ports, namely input, coupling, output and isolation. The first ends of Z1 and Z2 are input, which are connected to the second port of the circulator; the first ends of Z3 and Z4 are output; the second ends of Z1 and Z4 are isolation, which are connected to the RF output; the second ends of Z2 and Z3 are coupling. The bias and limiting network includes two GaN-based Schottky diodes D1 and D2 and capacitors C1 and C2. The coupling end of the branch line directional coupler is connected in series with C1 and D1 in sequence, and its output end is connected in series with C2 and D2 in sequence. The negative electrodes of D1 and D2 are grounded. The bias and limiting network also includes a symmetrical bias network, which is composed of bias resistors R1 and R2 and bias inductors L1 and L2. One end of L1 is connected to the positive electrodes of C1 and D1, and the other end is connected to one end of R1, and the other end of R1 is the X1 end; one end of L2 is connected to the positive electrodes of C2 and D2, and the other end is connected to one end of R2, and the other end of R2 is the X2 end; The high-power rectifier includes an impedance matching structure Z5, a GaN-based Schottky diode D3 and a λ / 8 branch impedance line Z6 connected in sequence, and Z6 is grounded; The straight-through filter includes an impedance matching structure Z7, a λ / 4 branch impedance line Z8, a λ / 2 branch impedance line Z9, and a λ / 8 branch impedance line Z10, one end of Z7 is connected to the negative electrode of D3, and the other end is connected to one end of Z8 to Z10 and the load end; The power signal reflected from the coupler's input is output through the third port of the circulator, first passing through the impedance matching structure Z5, and then entering the GaN-based Schottky diode D3, which rectifies the high-frequency signal into a DC current. The rectified DC current is accompanied by higher harmonics. Z8~Z10 in the pass-through filter suppress the fundamental wave, second harmonic and third harmonic respectively. The higher harmonics that are not completely suppressed are reflected back to D3 through Z7 and rectified again. Finally, the DC current is sent to the matching load through the load end, realizing real-time energy recovery and utilization.

2. The radio frequency protection circuit with integrated limiting threshold control and energy recovery function according to claim 1, characterized in that: When the input power is lower than the set limit threshold, that is, the turn-on voltage of D1 and D2, D1 and D2 are not conducting, and the coupling end and output end of the coupler are in an open circuit state. Therefore, the signal is transmitted from the input end of the coupler through Z1 to the isolation end and output from the RF output end. When the input power exceeds the set limiting threshold, D1 and D2 are turned on, forming an impedance mismatch. The reflected power at the coupling end and output end of the coupler flows to the input end and isolation end respectively. The reflected power is shown in formula (1), forming a limit on the input end signal. The power output to the isolation end has been limited, and the output is output to the subsequent circuit at a lower power. ； (1) in, is the incident power, is the reflected power, is the on-resistance of the diode, is the characteristic impedance, =50Ω.

3. The radio frequency protection circuit with integrated limiting threshold control and energy recovery function according to claim 1, characterized in that: The limiting threshold is controlled by a symmetrical bias network. By adjusting the resistors R1 and R2 and the applied bias voltage, the conduction threshold of D1 and D2 is controlled. The bias voltage range is -0.3V to +0.3V. By increasing the resistance values ​​of R1 and R2, the limiting threshold and limiting level are increased. When a positive voltage is connected to the X1 and X2 terminals, the limiting threshold and limiting level are reduced. When a negative voltage is connected to the X1 and X2 terminals, the limiting threshold and limiting level are increased. The overall limiting threshold is dynamically adjustable from -10dBm to +10dBm.

4. The radio frequency protection circuit with integrated limiting threshold control and energy recovery function according to claim 1, characterized in that: The GaN-based Schottky diodes D1, D2, and D3 are FCR080, with a reverse breakdown voltage of 120V, an on-resistance of 2.5Ω, and a turn-on voltage of approximately 0.45V.

Images