High-power-resistant cascade amplitude limiter, microwave radar receiver and protection method

Abstract

The invention discloses a high-power-resistant cascaded amplitude limiter, a microwave radar receiver comprising the same and a protection method. The cascaded amplitude limiter comprises a waveguide plasma amplitude limiter, a microstrip amplitude limiter and a waveguide coaxial converter which are cascaded in sequence. The receiver comprises an antenna, a difference device, the cascade amplitude limiter and a receiver radio frequency front-end circuit which are arranged in sequence, wherein the receiver radio frequency front-end circuit is communicated with the waveguide coaxial converter of the cascade amplitude limiter. The starting threshold of the micro-strip amplitude limiter is effectively improved compared with the working threshold of other amplitude limiters, it is ensured that echo signals can enter a receiver with low loss, and the sensitivity of the receiver is ensured. According to the cascade amplitude limiter, the standing-wave ratio near the working frequency is slightly larger than 1, the loss is low, and the use requirement is met. According to the invention, two stages of amplitude limiters in different forms are used, so that the high power resistance and the fast response time are improved; a micro-strip amplitude limiter is used to raise a starting threshold.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave protection, and in particular relates to a microwave radar receiver protection structure. Background Art

[0002] High-power microwave radar can detect, interfere with, and nearly destroy targets by emitting high-power microwaves. It has the characteristics of fast battlefield response, low cost, no pollution, light speed attack, no collateral damage from firepower, and all-weather standby. It is an advanced means of future battlefield confrontation. The pulse power of high-power microwave transmission signal is high (GW level) and the pulse width is narrow (ns level). When the high-power microwave radar receiver receives the target echo, the extremely strong electromagnetic radiation (greater than 10MW level) leaked will cause co-frequency electromagnetic leakage interference to the high-power microwave radar receiving channel through front-door coupling. The receiver, as the most direct front-door device, will be directly damaged, causing the radar to fail to work. High-power microwave protection technology has always been a research hotspot at home and abroad, but it mainly focuses on non-co-frequency leakage interference, high-power microwave radar transmission and reception are separated in two places, and kW-level leakage power electromagnetic pulses. It cannot effectively protect against high-power electromagnetic pulses; traditional limiters do not have the ability to withstand high power, and ordinary waveguide plasma limiters have a low start threshold. When they do not meet the protection of high-power echoes, they can receive strong echo signals, resulting in target loss. Summary of the invention

[0003] The technical problem to be solved by the present invention is that there is currently no limiter with GW-level transmission power, fast response, and high starting threshold to enable a high-power microwave receiver to normally receive strong echo signals and ensure that the equipment is not burned. A high-power microwave radar receiver protection structure with a cascade limiter that has high power resistance, extremely short response time, high starting power threshold, and low leakage power is provided.

[0004] The present invention is achieved through the following technical solutions.

[0005] According to a first aspect of the present invention, a high-power resistant cascade limiter is provided. The cascade limiter comprises a waveguide plasma limiter, a microstrip limiter and a waveguide coaxial converter which are cascaded in sequence.

[0006] Preferably, the waveguide plasma limiter includes a first sealing window and a second sealing window arranged on both sides of the resonance cavity, a plurality of discharge gaps arranged in a direction from the first sealing window to the second sealing window in the resonance cavity, and a rare gas and a radioactive element in the resonance cavity.

[0007] Preferably, each discharge gap is formed by a pair of electrodes arranged opposite to each other.

[0008] Preferably, the first sealing window and the second sealing window are respectively rectangular, and each pair of electrodes is arranged parallel to the narrow side of the sealing window.

[0009] Preferably, each pair of electrodes is a conical fixed electrode, and the opposite conical ends form the discharge gap.

[0010] Preferably, the waveguide plasma limiter further comprises a plurality of groups of resonance diaphragms, and each group of resonance diaphragms is symmetrically arranged on both sides of the paired electrodes with respect to the discharge gap.

[0011] Preferably, the noble gas is a mixture of argon and water vapor, and the radioactive element is gaseous tritium.

[0012] Preferably, the operating frequency band of the cascade limiter is C band, the peak power resistance is greater than 10MW, the response time is less than 2ns, the voltage standing wave ratio is less than 1.4, the recovery time is less than 1us, the leakage peak power is less than 1W, and the starting working threshold is greater than 10mW; the starting threshold of the microstrip limiter is about 13.5dBm.

[0013] A second aspect of the present invention provides a microwave radar receiver, the receiver comprising an antenna, a differential device, the cascade limiter as described above, and a receiver RF front-end circuit connected to a waveguide coaxial converter of the cascade limiter, which are arranged in sequence.

[0014] A third aspect of the present invention provides a protection method for the microwave radar receiver as described above, the protection method comprising:

[0015] When the power of the radar echo signal entering the cascade limiter is less than the working threshold of the microstrip limiter, the radar echo signal passes through the cascade limiter and enters the receiver;

[0016] When the pulse power incident to the cascade limiter instantly rises to a level greater than the ignition power of the cascade limiter, the discharge gap of the waveguide plasma limiter discharges to ionize the internal rare gas to generate plasma, which is combined with the microstrip limiter for secondary limiting to achieve reflection of the incident power, thereby protecting the receiver.

[0017] The beneficial effects of the present invention are:

[0018] The startup threshold of the microstrip limiter of the present invention is effectively improved compared to the working thresholds of other limiters, ensuring that the echo signal can enter the receiver with low loss, thereby ensuring the sensitivity of the receiver. The standing wave ratio near the working frequency of the cascade limiter of the present invention is slightly greater than 1, and the loss is relatively low to meet the use requirements. The present invention uses two stages of limiters of different forms to improve the high power resistance and fast response time; a microstrip limiter is used to raise the startup threshold. The present invention is a protection structure based on the cascade limiter, which is suitable for receiver protection of high-power microwave radars. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic diagram of the structure of the present invention;

[0020] Figure 2 is a cross-sectional schematic diagram of the waveguide plasma limiter of the present invention;

[0021] Figure 3 is a cross-sectional view of the waveguide plasma limiter of the present invention;

[0022] Figure 4 It is a performance simulation verification diagram of the cascade limiter of the present invention;

[0023] Figure 5 It is a schematic diagram of the use of the present invention;

[0024] In the figure: 1-cascade limiter, 2-antenna, 3-difference device, 4-waveguide plasma limiter, 41-resonance cavity, 42-flange, 43-sealing window, 44-discharge gap, 45-conical fixed electrode, 46-resonance diaphragm, 5-microstrip limiter, 6-waveguide coaxial converter, 7-receiver. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0026] The technical problem to be solved by the present invention is that there is currently no limiter with GW-level transmission power, fast response, and high starting threshold to enable a high-power microwave receiver to normally receive strong echo signals and ensure that the equipment is not burned. A high-power microwave radar receiver protection structure and protection method of a cascade limiter with high power resistance, extremely short response time, high starting power threshold, and low leakage power are provided.

[0027] The present invention provides a microwave radar receiver protection structure, comprising a cascade limiter, wherein the cascade limiter is arranged after an antenna and a differentiator, and before a receiver radio frequency front-end circuit, and the cascade limiter comprises a waveguide plasma limiter, a microstrip limiter, and a waveguide coaxial converter, wherein the microstrip limiter is cascaded after the waveguide plasma limiter, and the waveguide coaxial converter is cascaded after the microstrip limiter.

[0028] The operating frequency band of the cascade limiter of the present invention is C band, the peak power resistance is greater than 10MW, the response time is less than 2ns, the voltage standing wave ratio is less than 1.4, the recovery time is less than 1us, the leakage peak power is less than 1W, and the starting working threshold is greater than 10mW.

[0029] Preferably, the waveguide plasma limiter comprises a resonant cavity, a flange, a sealing window and a discharge gap, and rare gas and radioactive elements are arranged in the waveguide plasma limiter.

[0030] Preferably, two groups of discharge gaps are provided and are located inside the resonance cavity. The discharge gaps include fixed electrodes and resonance diaphragms that are opposite to each other up and down. The resonance diaphragms are symmetrically distributed on both sides of the fixed electrodes.

[0031] Preferably, the fixed electrode is parallel to the narrow side of the sealing window, and the resonant diaphragm is parallel to the sealing window.

[0032] Preferably, the flanges are distributed on both sides of the resonance cavity.

[0033] Preferably, the sealing windows are distributed on both sides of the resonance cavity.

[0034] Preferably, the rare gas is a mixture of argon and water vapor.

[0035] Preferably, the radioactive element is gaseous tritium.

[0036] According to a protection method for a microwave radar receiver protection structure of the present invention, when the microwave radar receives an echo normally, the radar echo signal power entering the cascade limiter is less than the working threshold of the microstrip limiter, the cascade limiter is equivalent to a bandpass filter, and the echo signal passes smoothly and enters the back-end receiver. During the period when the radar transmits a high-power pulse, the pulse power incident to the cascade limiter rises instantaneously. When the pulse power is greater than the ignition power of the cascade limiter, the discharge gap of the waveguide plasma limiter discharges to ionize the internal rare gas to generate plasma, and combines with the microstrip limiter to perform secondary limiting, thereby realizing reflection of the incident power and realizing protection of the receiver.

[0037] Example

[0038] like Figures 1 to 5 As shown, a microwave radar receiver protection structure includes a cascade limiter 1, wherein the cascade limiter 1 is placed after a receiving antenna 2 and a differentiator 3, and before a radio frequency front-end circuit of a receiver 7. The cascade limiter 1 includes a waveguide plasma limiter 4, a microstrip limiter 5, and a waveguide coaxial converter 6. The microstrip limiter 5 is cascaded after the waveguide plasma limiter 4, and the waveguide coaxial converter 6 is cascaded after the microstrip limiter 5.

[0039] The waveguide plasma limiter 4 comprises a resonant cavity 41 , a flange 42 , a sealing window 43 and a discharge gap 44 . Rare gas and radioactive elements are arranged in the waveguide plasma limiter 4 .

[0040] The operating frequency band of the cascade limiter 1 is C band, the peak power resistance is greater than 10MW, the response time is less than 2ns, the voltage standing wave ratio is less than 1.4, the recovery time is less than 1us, the leakage peak power is less than 1W, and the starting working threshold is greater than 10mW.

[0041] The discharge gap 44 is provided with two groups and is located inside the resonant cavity 41. The discharge gap 44 includes a conical fixed electrode 45 and a resonant diaphragm 46 which are opposite to each other. The resonant diaphragm 46 is symmetrically distributed on both sides of the conical fixed electrode 45. The function of this setting is to enhance the local field strength inside the waveguide plasma limiter 4, which is conducive to quickly breaking down the working gas to form plasma.

[0042] The conical fixed electrode 45 is parallel to the narrow side of the sealing window 43, and the resonance diaphragm 46 is parallel to the sealing window 43. The function of this arrangement is to discharge and break down the working gas to form plasma.

[0043] The flanges 42 are distributed on both sides of the resonant cavity 41 . The flanges 42 are used to connect the protector of the receiver 7 , the waveguide plasma limiter 4 and the microstrip limiter 5 .

[0044] The sealing windows 43 are distributed on both sides of the resonant cavity 41 , and the functions of the sealing windows 43 are: transmission of microwave energy and maintenance of plasma.

[0045] The rare gas is a mixed gas of argon and water vapor. Using the mixed gas of argon and water vapor can effectively improve the protection capability against high-frequency and high-power microwave energy.

[0046] The radioactive element is gaseous tritium. Gaseous tritium has the advantages of being safe, effective, and rich in radiated electrons, and can provide an initial electron source for discharge in the discharge gap.

[0047] A protection method for a microwave radar receiver protection structure. When a high-power microwave radar receives an echo normally, the radar echo signal power entering a cascade limiter 1 is less than the working threshold of a microstrip limiter 5. The cascade limiter 1 is equivalent to a bandpass filter. The echo signal passes smoothly and enters a back-end receiver. During the period when the radar transmits a high-power pulse, the pulse power incident to the cascade limiter 1 rises instantaneously. When the pulse power is greater than the ignition power of the cascade limiter 1, that is, when the threshold power is started, a discharge gap 44 of a waveguide plasma limiter 4 discharges and ionizes the internal rare gas to generate plasma, and performs secondary limiting in combination with the microstrip limiter 5 to realize reflection of the incident power and protection of the receiver.

[0048] The limiting performance of microstrip limiter 5 is verified, as shown in the following table:

[0049]

[0050] As can be seen from the above table, the start threshold of the microstrip limiter 5 is about 13.5 dBm, which is effectively improved compared with the working thresholds of other limiters, ensuring that the echo signal can enter the receiver 7 with low loss, thereby ensuring the sensitivity of the receiver 7.

[0051] The performance of cascade limiter 1 is simulated and verified. The results are as follows: Figure 4 As shown, the standing wave ratio of the cascade limiter 1 near the operating frequency is slightly greater than 1, and the loss is low to meet the use requirements.

Claims

1. A high power cascade limiter, characterized in that: The cascade limiter comprises a waveguide plasma limiter, a microstrip limiter and a waveguide coaxial converter which are cascaded in sequence.

2. The cascade limiter according to claim 1, characterized in that: The waveguide plasma limiter comprises a first sealing window and a second sealing window arranged on both sides of a resonance cavity, a plurality of discharge gaps arranged in a direction from the first sealing window to the second sealing window in the resonance cavity, and rare gas and radioactive elements in the resonance cavity.

3. The cascade limiter according to claim 2, characterized in that: Each discharge gap is formed by a pair of electrodes disposed opposite to each other.

4. The cascade limiter according to claim 3, characterized in that: The first sealing window and the second sealing window are respectively rectangular, and each pair of electrodes is arranged parallel to the narrow side of the sealing window.

5. The cascade limiter according to claim 4, characterized in that: Each pair of electrodes is a conical fixed electrode, and the opposite conical ends form the discharge gap.

6. The cascade limiter according to claim 4, characterized in that: The waveguide plasma limiter further comprises a plurality of groups of resonance diaphragms, and each group of resonance diaphragms is symmetrically arranged on both sides of the paired electrodes with respect to the discharge gap.

7. The cascade limiter according to claim 2, characterized in that: The rare gas is a mixed gas of argon and water vapor, and the radioactive element is gaseous tritium.

8. The cascade limiter according to claim 2, characterized in that: The operating frequency band of the cascade limiter is C band, the peak power resistance is greater than 10MW, the response time is less than 2ns, the voltage standing wave ratio is less than 1.4, the recovery time is less than 1us, the leakage peak power is less than 1W, and the starting working threshold is greater than 10mW; the starting threshold of the microstrip limiter is about 13.5dBm.

9. A microwave radar receiver, characterized in that: The receiver comprises an antenna, a differential, a cascade limiter according to any one of claims 1 to 8, and a receiver radio frequency front-end circuit connected to a waveguide coaxial converter of the cascade limiter, which are arranged in sequence.

10. A protection method for a microwave radar receiver according to claim 9, characterized in that: The protection method includes When the power of the radar echo signal entering the cascade limiter is less than the working threshold of the microstrip limiter, the radar echo signal passes through the cascade limiter and enters the receiver; When the pulse power incident on the cascade limiter instantly rises to a level greater than the ignition power of the cascade limiter, the discharge gap of the waveguide plasma limiter discharges to ionize the internal rare gas to generate plasma, which is combined with the microstrip limiter for secondary limiting to achieve reflection of the incident power.

Images