High-power microwave amplitude limiting circuit design

Abstract

The invention discloses a high-power microwave amplitude limiting circuit which has a three-stage structure, a first-stage circuit and a second-stage circuit are respectively composed of three Schottky diodes at the upper part and three Schottky diodes at the lower part, and a third-stage circuit is respectively composed of three PIN diodes at the upper part and three PIN diodes at the lower part and is symmetrically distributed. Each stage of circuit is connected by a quarter-wavelength impedance transmission line, and two ends of the circuit are connected in series with a capacitor. After a radio-frequency signal is input from the first port, the Schottky diodes are rapidly conducted and generate direct current, the direct current can provide forward bias for the PIN diodes which are reversely connected in parallel after passing through the Schottky diodes of the first two stages, the bias current can rapidly reduce the forward conduction resistance of the PIN diodes, the PIN diodes are made to be in an approximate short-circuit state, and therefore the positive conduction resistance of the PIN diodes is reduced. The current is output from the third stage, and at the moment, the circuit can reflect most incident power so as to achieve the purpose of amplitude limiting. The invention overcomes the defects of difficult circuit structure adjustment, poor performance and the like, and has the advantages of low power consumption, large power capacity, small peak leakage energy, small response time and the like.

Description

Technical Field

[0001] The invention relates to a limiter with high-power microwave characteristics, belonging to the technical field of radio frequency wireless communication. Background Art

[0002] The limiter circuit is a two-port network whose impedance changes with the input RF signal. It can actually be regarded as a power control circuit. The main function of the limiter circuit is to ensure the lossless passage of the signal when the received microwave signal is small, to ensure the sensitivity of the system, and to attenuate the signal when the passing signal is large, to ensure that the subsequent stage receives only limited power, thereby completing the protection of the subsequent stage.

[0003] The limiting diode is the core component of the limiting operation, which determines the insertion loss, limiting level, power capacity and other performance indicators of the limiter. The limiting circuit relies on the microwave characteristics of the limiting diode when working. The limiting diode is usually a nonlinear element. When the microwave signal passes through the limiting diode, it can be controlled to be on or off according to the signal size.

[0004] The traditional power divider is a commonly used radio frequency (RF) device, and its structure mainly includes a microstrip line, a coupling structure and an output port. The traditional limiter has the following disadvantages:

[0005] 1. Distortion: Traditional limiters may introduce distortion, especially when the input signal exceeds the limiting range, a clipping effect will occur, resulting in distorted output signals.

[0006] 2. Overload: When the input signal exceeds the processing range of the limiter, the traditional limiter cannot effectively process these overload signals, which may cause the output signal to be completely truncated or produce nonlinear distortion.

[0007] 3. Fixed limiting range: Traditional limiters can usually only set a fixed limiting range, which may limit their applicability under different signal ranges.

[0008] 4. Power consumption: Traditional limiters may consume more power, especially when they need to work continuously for a long time, high power consumption may become a problem.

[0009] Although traditional limiters have these shortcomings, they are still practical in some simple application scenarios. In recent years, with the development of technology, some new limiter designs have attempted to overcome the shortcomings of these traditional limiters and provide better performance and flexibility.

[0010] Limiters are widely used in communication systems, audio processing, medical imaging, power systems, and other fields. They also have unique applications in various scientific, engineering, and technical fields to meet specific signal processing requirements, mainly because they can limit the amplitude range of signals. Summary of the invention

[0011] Purpose of the invention: The main technical problem solved by the present invention is to provide a high-power microwave limiting circuit, which has the advantages of flexible adjustable limiting range, high sensitivity, low power consumption, large power capacity, small peak leakage energy and response time, while having the disadvantages of large circuit size, difficult circuit structure adjustment, poor performance and other shortcomings of the existing power capacity improvement technology.

[0012] Technical solution: In order to achieve this purpose, a high-power microwave limiting circuit of the present invention adopts the following technical solution:

[0013] The high-power microwave limiting circuit includes: Schottky diodes, PIN diodes, transmission lines and capacitors. The limiter adopts a three-stage tube limiting circuit structure. The first stage circuit adopts Schottky diodes, and the Schottky diodes from top to bottom are SBD1, SBD2, SBD3, SBD4, SBD5, and SBD6; the second stage circuit also adopts Schottky diodes, and from top to bottom are SBD7, SBD8, SBD9, SBD10, SBD11, and SBD12; the third stage circuit adopts PIN diodes, and from top to bottom are PN1, PN2, PN3 and PN4, PN5, and PN6. After the large RF signal is input from the first port, the Schottky diode is quickly turned on and generates a DC current. After passing through the Schottky diodes of the first two stages, the DC current can provide a forward bias for the reverse-parallel PIN diode. The bias current can quickly reduce the forward conduction resistance of the PIN diode, making the PIN diode close to a short-circuit state. The current is output from the third stage. At this time, the circuit can reflect most of the incident power to achieve the purpose of limiting.

[0014] Beneficial effects: Compared with the traditional limiter, the present invention uses PIN pair tubes instead of inductors to provide a DC circuit to improve the power capacity of the limiter circuit; the method of replacing PIN diodes with Schottky diodes reduces the peak leakage energy and response time of the limiter circuit; the number of diodes in each circuit is increased to improve the power resistance and power capacity of the limiter circuit; the method of using a cascade limiter structure further improves the power capacity and isolation of the limiter circuit. The invention has the advantages of flexible adjustable range of limiter, high sensitivity, low power consumption, large power capacity, small peak leakage energy and response time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A functional block diagram of a preferred embodiment of a high-power microwave limiting circuit of the present invention;

[0016] Figure 2 It is a structural schematic diagram of a limiter circuit of a comparative example of the present invention;

[0017] Figure 3 The figure is an S parameter waveform diagram of a limiter circuit of a comparative example of the present invention;

[0018] Figure 4 It is a simulation waveform diagram of input and output power of a limiter circuit of a comparative example of the present invention;

[0019] Figure 5 It is a structural schematic diagram of a high-power microwave limiting circuit of the present invention;

[0020] Figure 6 It is an S parameter waveform diagram of a high-power microwave limiting circuit of the present invention;

[0021] Figure 7 The figure is a simulation waveform diagram of input and output power of a high-power microwave limiting circuit of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0023] The technical solution of the present invention is further described below in conjunction with the specific implementation manner and the accompanying drawings. Figure 1 to Figure 7 , the embodiment of the present invention includes:

[0024] like Figure 1 The functional block diagram of a preferred example of a high-power microwave limiting circuit is shown. The block diagram provides a good idea for designing a high-power microwave limiter, which includes: a matching circuit (1), a matching circuit (2), diodes (D1, D2, D3, D4, D5, D6), and transmission lines (TL1, TL2). The matching circuit (1) and the matching circuit (2) both use a DC blocking capacitor to ensure that the circuit can operate more stably. The first-stage circuit is composed of a diode D1 and a diode D2, respectively, in which the positive electrode of the diode D1 is grounded and the negative electrode of the diode D2 is grounded. The first-stage circuit and the second-stage circuit are connected by a quarter-wavelength impedance transmission line TL1; the second-stage circuit is composed of a diode D3 and a diode D4, respectively, in which the positive electrode of the diode D3 is grounded and the negative electrode of the diode D4 is grounded. The second-stage circuit is connected by a quarter-wavelength impedance transmission line TL2; the third-stage circuit is composed of a diode D5 and a diode D6, respectively, in which the positive electrode of the diode D5 is grounded and the negative electrode of the diode D6 is grounded. The port impedance of the input and output ports is 50Ω.

[0025] After the signal is input from the first port, the Schottky diode is quickly turned on and generates a DC current. After passing through the Schottky diodes of the first two stages, the DC current can provide a forward bias for the reverse parallel PIN diode. This bias current can quickly reduce the forward conduction resistance of the PIN diode, making the PIN diode close to a short-circuit state. The current is output from the third stage. At this time, the circuit can reflect most of the incident power to achieve the purpose of limiting. The three-stage structure increases the power capacity of the limiter by increasing its order to meet the high power requirements of the limiter.

[0026] like Figure 5 As shown, in this embodiment, the diode D1 in the first stage circuit is replaced by Schottky diodes SBD1, SBD2, and SBD3, the positive electrode of Schottky diode SBD1 is grounded, and the other end is connected to Schottky diode SBD2, the positive electrode of Schottky diode SBD2 is connected to Schottky diode SBD1, and the other end is connected to Schottky diode SBD3. By using Schottky diodes in the input signal path, the response delay can be reduced and the processing capability of the limiter for fast-changing signals can be improved; the diode D2 is replaced by Schottky diodes SBD4, SBD5, and SBD6, wherein the cathode of Schottky diode SBD6 is grounded, The other end is connected to Schottky diode SBD5, the anode of Schottky diode SBD5 is connected to SBD4, and the other end is connected to SBD6; the diode D3 in the second stage circuit is replaced by Schottky diodes SBD7, SBD8, and SBD9, wherein the anode of Schottky diode SBD7 is grounded, and the other end is connected to SBD8; the diode D4 is replaced by Schottky diodes SBD10, SBD11, and SBD12, wherein the anode of Schottky diode SBD12 is connected to SBD11, and the other end is grounded; the use of Schottky diodes has a faster switching speed and a lower turn-on voltage, and can respond to changes in input signals more quickly. The diode D5 in the third stage circuit is replaced by PIN diodes PN1, PN2, and PN3, wherein the anode of PIN diode PN1 is grounded, and the other end is connected to PIN diode PN2, the anode of PIN diode PN2 is connected to PIN diode PN1, and the other end is connected to PIN diode PN3; the diode D6 is replaced by PIN diodes PN4, PN5, and PN6, wherein the anode of PIN diode PN6 is connected to PIN diode PN5, and the other end is grounded. The use of PIN diodes can effectively limit the excessive amplitude of the input signal while minimizing the impact on the signal quality. At the same time, it can make the signal work in a wider frequency band, increase the bandwidth, and make the limiter work in the S frequency band. The matching circuit (1) selects the DC blocking capacitor C1, and the matching circuit (2) selects the DC blocking capacitor C2.

[0027] like Figure 6The S parameter waveform of the high-power micro-wave limiting circuit based on the tube structure is shown. S(1, 1) represents the input return loss and S(2, 1) represents the insertion loss. It can be seen that the bandwidth coverage range is from 2GHz to 4GHz. Within this coverage range, the insertion loss is within 0.24dB and is only 0.215dB at the center frequency of 3GHz; the input return loss is below -27dB and reaches about 33.5dB at the center frequency of 3GHz.

[0028] like Figure 7 The input and output power simulation waveforms of the high-power microwave limiting circuit based on the tube structure are shown. It can be seen that the circuit's threshold level is 17dBm and the stable output level is 22dBm. The circuit power capacity is 50dBm and the maximum isolation is about 28dB. It meets the performance requirements of the limiter.

[0029] Comparative Example:

[0030] like Figure 2 As shown, a single-stage PIN pair tube limiting circuit is adopted. In the comparative example, only two diodes are used, which are symmetrically distributed up and down.

[0031] like Figure 3 From the S parameter waveform diagram of the limiter circuit shown, it can be seen that the insertion loss at the center frequency of 3 GHz is 0.32 dB; the input return loss is between 11.5 dB and 13.5 dB in the S band, and is only 13 dB at the center frequency of 3 GHz. Compared with the present invention, the insertion loss of the single-stage PIN pair tube limiter circuit becomes larger, and the standing wave characteristic of the input end becomes worse.

[0032] like Figure 4 The input and output power simulation waveforms of the limiter circuit shown in the figure show that the threshold level of the circuit is 13dBm and the stable output level is 17dBm. The power capacity of the circuit is 32dBm and the maximum isolation is about 15dB. Compared with the present invention, the power capacity of the circuit is 18dBm lower and the isolation is lower, which does not meet the high power requirements.

[0033] In summary, the high-power microwave limiting circuit pointed out in the present invention has the advantages of flexible adjustable limiting range, high sensitivity, low power consumption, large power capacity, small peak leakage energy and response time, and compact structure while reducing the chip size, which meets the processing applications of PCB board-level and chip-level circuits.

[0034] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high power microwave limiting circuit, characterized in that: The circuit has a three-level structure. Each level of the circuit includes a first port, a second port, Schottky diodes (SBD1, SBD2, SBD3, SBD4, SBD5, SBD6, SBD7, SBD8, SBD9, SBD10, SBD11, SBD12), PIN diodes (PN1, PN2, PN3, PN4), MIM capacitors (C1, C2), and transmission lines (TL1, TL2). Among them: After the signal is input from the first port, the Schottky diode is quickly turned on and generates a DC current. After passing through the Schottky diodes of the first two stages, the DC current can provide a forward bias for the reverse-parallel PIN diode. The bias current can quickly reduce the forward conduction resistance of the PIN diode, making the PIN diode close to a short-circuit state. The current is output from the third stage. At this time, the circuit can reflect most of the incident power to achieve the purpose of limiting. SBD1, SBD2, SBD3 and SBD4, SBD5, SBD6 are located at both ends of the first input port to form a first-level circuit structure, SBD7, SBD8, SBD9 and SBD10, SBD11, SBD12 are located in the second-level circuit structure, PN1, PN2, PN3 and PN4, PN5, PN6 are located in the third-level circuit structure. All diodes in the three-level circuit are symmetrically distributed.

2. The high-power microwave limiting circuit according to claim 1, characterized in that: The diodes in each stage are located on both sides of the transmission impedance and adopt a pair structure. Their function is to protect the circuit from the influence of excessive input signals or excessive reverse signals, ensuring that the circuit can work correctly without damage regardless of whether the input signal is forward or reverse.

3. The high-power microwave limiting circuit according to claim 1, characterized in that: The diodes in the first two stages of the circuit are Schottky diodes, and the last stage of the circuit uses PIN diodes. The Schottky diodes are turned on first, which can reduce the risk of input signal being cut off, while reducing power consumption and improving circuit efficiency. In order to further improve the power tolerance of the circuit and reduce leakage power.

4. The high-power microwave limiting circuit according to claim 1, characterized in that: The circuit has a three-level structure, and the power capacity and isolation of the limiting circuit are improved by increasing the number of orders.

5. The high-power microwave limiting circuit according to claim 1, characterized in that: The parameters of Schottky diodes SBD1, SBD2, SBD3, SBD4, SBD5, and SBD6 in the first stage circuit are the same, and the parameters of Schottky diodes SBD7, SBD8, SBD9, SBD10, SBD11, and SBD12 in the second stage circuit are the same, and the parameters of the first and second stage Schottky diodes are exactly the same, but because they are in different positions in the circuit, the power acting on each tube is different, and the corresponding bias is also different, resulting in their unequal impedance. Schottky diodes have faster switching speeds and lower turn-on voltages, and can respond to changes in input signals more quickly than PIN diodes. By using Schottky diodes in the input signal path, the response delay can be reduced and the limiter's ability to handle rapidly changing signals can be improved.

6. The high-power microwave limiting circuit according to claim 1, characterized in that: The PIN diodes PN1, PN2, PN3, and PN4 of the third-stage circuit have the same parameters, and the PIN diodes can effectively limit the excessive amplitude of the input signal while affecting the quality of the signal as little as possible. At the same time, the signal can work in a wider frequency band, increase the bandwidth, and make the limiter work in the S frequency band.

7. The high-power microwave limiting circuit according to claim 1, characterized in that: The transmission lines TL1 and TL2 are the same, the capacitors C1 and C2 are the same, each pair of tubes is connected by a transmission line with a spacing of one quarter wavelength, so that the circuit can be well matched; the function of the capacitor is to act as a DC block to ensure that the circuit can operate more stably.

8. The high-power microwave limiting circuit according to claim 3, characterized in that: The three-stage circuit is composed of three diodes at the top and bottom, which increases the number of diodes and improves the power resistance and power capacity of the limiting circuit. At the same time, the first two stages are Schottky diodes, and the last stage is a mixed pair structure of PIN diodes, which further improves the power tolerance of the circuit and reduces leakage power.

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