A non-reciprocal limiter

Abstract

The present invention proposes a non-reciprocal limiter, including a common transmission and reception path, wherein the common transmission and reception path includes a first input / output terminal, a directional coupler, a limiting circuit and a second input / output terminal connected in sequence, a detection circuit, an amplifier and a comparator are connected between the directional coupler and the limiting circuit, the directional coupler couples part of the energy from the common transmission and reception path and sends it to the detection circuit, the DC detection voltage output by the detection circuit is amplified by the amplifier and input to the comparator for comparison with its reference level, the comparator outputs a high / low level to provide a DC bias to the limiting circuit, and changes the starting level of the limiting circuit. When transmitting a signal, the starting level of the limiter is higher than the transmission power, so that the transmission signal passes smoothly; when receiving a signal, the starting level of the limiter is lower, so that the receiving signal is limited within the required range. The present invention realizes the non-reciprocity of the limiter.

Description

Technical Field

[0001] The invention relates to the technical field of radio frequency microwave circuits, and in particular to a non-reciprocal limiter. Background Art

[0002] A limiter is a commonly used RF device that limits the output signal amplitude within a certain range. Usually, the limiter is connected before the low-noise amplifier of the T / R component to protect the low-noise amplifier and receiver from being damaged by high-power signals, but it cannot effectively protect the transmitter and transceiver switch.

[0003] Existing limiters are generally not directional. For single-stage limiters, the limiting performance is basically the same when the signal is input in both directions; while for multi-stage limiters, the limiting structure of the previous stage is usually optimized to improve the withstand power, and generally requires unidirectional input and unidirectional output. Therefore, when using existing limiters to protect transmitters and transceiver switches, the transmitted signal will be limited at the same time. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a non-reciprocal limiter, which has different threshold levels for the receiving and transmitting signals, so that it can be applied to the transmission and receiving common path to protect the receiving and transmitting switch, and can also be applied to the transmission and receiving separate paths to protect the transmitter. The limiter is placed between the transmitting antenna and the transmitter or between the transmitting and receiving antenna and the receiving and transmitting switch. When transmitting the signal, the threshold level of the limiter is higher than the transmitting power, so that the transmitting signal passes smoothly; when receiving the signal, the threshold level of the limiter is lower, so that the receiving signal is limited within the required range.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] On the one hand, the present invention provides a non-reciprocal limiter, comprising a common transmission and reception path, wherein the common transmission and reception path comprises a first input / output terminal, a directional coupler, a limiter circuit and a second input / output terminal connected in sequence, a detection circuit, an amplifier and a comparator are connected between the directional coupler and the limiter circuit, the directional coupler couples part of the energy from the common transmission and reception path and sends it to the detection circuit, the detection circuit detects the signal input from the directional coupler into a DC detection voltage, the amplifier amplifies the detection voltage and inputs it to the comparator for comparison with its reference level, and then the comparator outputs a high / low level to provide a DC bias to the limiter circuit to change the threshold level of the limiter circuit; by utilizing the directionality of the directional coupler, when the common transmission and reception path transmits a signal, the threshold level of the limiter circuit is higher than the transmission power, and the transmission signal passes normally; when the common transmission and reception path receives a signal, once the power of the received signal input from the directional coupler to the limiter circuit is greater than or equal to the threshold level of the limiter circuit, the limiter circuit starts to limit the signal power input from the directional coupler to the limiter circuit within a required range.

[0007] Furthermore, in the present invention, the first input / output terminal is connected to the first terminal of the directional coupler, the second terminal of the directional coupler is connected to the first terminal of the limiter circuit, the third terminal of the directional coupler is connected to the first terminal of the detector circuit, the second terminal of the detector circuit is connected to the first terminal of the amplifier, the comparator has two input terminals, namely the first terminal of the comparator and the third terminal of the comparator, the second terminal of the amplifier is connected to the first terminal of the comparator, the reference level is input from the third terminal of the comparator, the second terminal of the comparator serves as the output terminal of the comparator, the second terminal of the comparator is connected to the third terminal of the limiter circuit, the second terminal of the limiter circuit is connected to the second input / output terminal, when the transmit-receive common path transmits a signal from the first input / output port, the third terminal of the directional coupler is the isolation port of the directional coupler; when the transmit-receive common path receives a signal from the first input / output port, the third terminal of the directional coupler is the coupling port of the directional coupler.

[0008] Furthermore, the first input / output end of the present invention includes a first input / output port and a first matching circuit, the first input / output port is connected to the first end of the first matching circuit, the second end of the first matching circuit is connected to the first end of the directional coupler, and the first matching circuit is used to achieve impedance matching.

[0009] Furthermore, the second input / output end of the present invention includes a second input / output port and a second matching circuit, the second input / output port is connected to the second end of the second matching circuit, the first end of the second matching circuit is connected to the second end of the limiting circuit, and the second matching circuit is used to achieve impedance matching.

[0010] Furthermore, the first matching circuit and the second matching circuit of the present invention are both composed of transmission lines and DC blocking capacitors.

[0011] In the present invention, when the transmitting and receiving common path receives a signal from the first input / output port, if the power of the received signal input from the third end of the directional coupler to the limiting circuit is less than the limiting level of the limiting circuit, the received signal passes through the limiting circuit to the second matching circuit with low loss or even without loss; if the power of the signal input from the directional coupler to the limiting circuit is greater than or equal to the limiting level of the limiting circuit, the limiting circuit starts limiting and limits the power of the signal input from the directional coupler to the limiting circuit to be lower than the tolerable power of the transmitter or the transmitting and receiving switch.

[0012] Furthermore, the directional coupler described in the present invention is one of a parallel line directional coupler, a branch line directional coupler and a Lange directional coupler.

[0013] Furthermore, the detection circuit of the present invention is composed of a plurality of Schottky diodes and capacitors connected in series and in parallel.

[0014] Furthermore, the amplifier of the present invention often adopts an operational amplifier circuit composed of transistors or field effect transistors.

[0015] Furthermore, the comparator described in the present invention is often a voltage comparator.

[0016] Furthermore, the limiting circuit of the present invention includes 1 to 3 levels of limiting structures, each level of limiting structures is connected by a quarter-wavelength transmission line. Further, each level of limiting structure includes 1 to 3 parallel limiting units, and each limiting unit includes 1 to 9 PIN diodes of the same model connected in series.

[0017] The present invention utilizes the directivity of the directional coupler to realize the non-reciprocity of the limiter, so that the starting and limiting levels of the two-way input of the limiter are different. Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] The present invention has different responses to the receiving and transmitting signals, that is, it has a smaller insertion loss for the transmitted high-power signal and has a better limiting effect for the received high-power signal. It can be applied to the transmission and reception common path to protect the transceiver switch, and can also be applied to the transmission and reception separate paths to protect the transmitter, which can effectively solve the problem that the traditional limiter can only be applied to the receiving channel, and improve the power resistance of the transmission channel or the transceiver switch.

[0019] Compared with the design of the non-reciprocal limiter without an amplifier, the present invention adopts an amplifier, and under the condition of the same detection effect, the signal power input from the directional coupler to the detection circuit can be reduced, the insertion loss of the non-reciprocal limiter can be reduced, and the influence on the transmission power can be reduced.

[0020] The present invention adopts a comparator to compare the amplified detection voltage with a set reference level through the comparator. When the detection voltage is higher than the reference level, the comparator outputs a high level to provide a positive bias voltage to the limiter circuit and reduce the limiter level of the limiter circuit. When the detection voltage is lower than the reference level, the comparator outputs a low level to provide a zero bias or a negative bias voltage to the limiter circuit. The negative bias voltage can raise the limiter level of the limiter circuit. According to the reasonable setting of the reference level of the comparator and the high / low level of the output, the limiter level of the non-reciprocal limiter when sending and receiving signals can be flexibly adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without creative work.

[0022] Figure 1 A schematic diagram of a circuit structure of an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of a circuit structure of an embodiment of the present invention;

[0024] Figure 3 A circuit structure diagram of an embodiment of the present invention;

[0025] Numbers in the figure:

[0026] 01, first input / output port; 02, second input / output port;

[0027] 10. First matching circuit; 101. First end of the first matching circuit; 102. Second end of the first matching circuit;

[0028] 20, directional coupler; 201, first end of directional coupler; 202, second end of directional coupler; 203, third end of directional coupler; 211, first resistor;

[0029] 30, a limiter circuit; 301, a first end of the limiter circuit; 302, a second end of the limiter circuit; 303, a third end of the limiter circuit; 311, a first PIN diode; 312, a second PIN diode; 313, a third PIN diode;

[0030] 40. A second matching circuit; 401. A first end of the second matching circuit; 402. A second end of the second matching circuit.

[0031] 50, detection circuit; 501, first end of detection circuit; 502, second end of detection circuit; 511, first capacitor; 512, second capacitor; 521, first Schottky diode; 522, second Schottky diode;

[0032] 60, amplifier; 601, first end of amplifier; 602, second end of amplifier; 611, first resistor; 612, second resistor; 613, third resistor; 621, amplifier chip;

[0033] 70. Comparator; 701. First terminal of comparator; 702. Second terminal of comparator, 703. Third terminal of comparator; 711. First resistor; 712. Second resistor; 721. First voltage source; 731. Comparator chip. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention more clearly understood, the following will be used with drawings and detailed descriptions to clearly illustrate the spirit of the contents disclosed by the present invention. After understanding the embodiments of the contents of the present invention, any person skilled in the art can change and modify the techniques taught by the contents of the present invention without departing from the spirit and scope of the contents of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0035] Reference Figure 1 In one embodiment, the non-reciprocal limiter provided mainly includes a transmit-receive common path, wherein the transmit-receive common path includes a first input / output port 01, a directional coupler 20, a limiting circuit 30 and a second input / output port 02 connected in sequence, and a detection circuit 50, an amplifier 60 and a comparator 70 are connected between the directional coupler 20 and the limiting circuit 30.

[0036] The first input / output port 01 is connected to the first end 201 of the directional coupler, the second end 202 of the directional coupler is connected to the first end 301 of the limiter circuit, the third end 203 of the directional coupler is connected to the first end 501 of the detector circuit, the second end 502 of the detector circuit is connected to the first end 601 of the amplifier, the comparator 70 has two input ends, namely the first end 701 of the comparator and the third end 703 of the comparator, the second end 602 of the amplifier is connected to the first end 701 of the comparator, the reference level is input from the third end 703 of the comparator, the second end 702 of the comparator is used as the output end of the comparator 70, the second end 702 of the comparator is connected to the third end 303 of the limiter circuit, the second end 302 of the limiter circuit is connected to the second input / output port 02, when the transmit-receive common path transmits a signal from the first input / output port 01, the third end 203 of the directional coupler is the isolation port of the directional coupler 20; when the transmit-receive common path receives a signal from the first input / output port 01, the third end 203 of the directional coupler is the coupling port of the directional coupler 20.

[0037] The directional coupler 20 couples part of the energy from the common transmission and reception path and sends it to the detection circuit 50. The detection circuit 50 detects the signal input from the directional coupler 20 into a DC detection voltage. The amplifier 60 amplifies the DC detection voltage output by the detection circuit 50 and inputs it to the comparator 70 for comparison with its reference level. Then the comparator 70 outputs a high / low level to provide a DC bias to the limiter circuit 30 to change the limiter level of the limiter circuit. The directional coupler 20 has four ports, a first end 201 of the directional coupler, a second end 202 of the directional coupler, a third end 203 of the directional coupler and a fourth end of the directional coupler, wherein the fourth end of the directional coupler is connected to a grounded resistor. Figure 1 Not shown in the figure. By utilizing the directivity of the directional coupler 20, when the transmission and reception common path transmits a signal, the threshold level of the limiter circuit 30 is higher than the transmission power, and the transmission signal passes normally; when the transmission and reception common path receives a signal, once the power of the received signal input from the directional coupler 20 to the limiter circuit 30 is greater than or equal to the threshold level of the limiter circuit 30, the limiter circuit 30 starts to limit the signal power input from the directional coupler 20 to the limiter circuit 30 within the required range, ensuring that the output level of the second input / output port 02 is lower than the withstand power of the transmitter or the transceiver switch, thereby preventing the transmitter or the transceiver switch from being damaged.

[0038] When the transmitting and receiving common path receives a signal from the first input / output port 01, the third end 203 of the directional coupler is the coupling port of the directional coupler 20. At this time, the signal power input from the third end 203 of the directional coupler to the detection circuit 30 is relatively large. At this time, the logarithm of the ratio of the output power of the third end 203 of the directional coupler to the input power of the first end 201 of the directional coupler is recorded as the coupling degree C; when the signal enters from the second input / output port 02 and transmits from the first input / output port 01, the third end 203 of the directional coupler is the isolation port of the directional coupler 20. At this time, the signal power input from the third end 203 of the directional coupler to the detection circuit 30 is relatively small. At this time, the logarithm of the ratio of the output power of the third end 203 of the directional coupler to the input power of the second end 202 of the directional coupler is recorded as the isolation degree I. The difference between the coupling degree C and the isolation degree I is usually recorded as the directivity D.

[0039] When the signal is input from the first input / output port 01, the third end 203 of the directional coupler is the coupling port of the directional coupler 20. The signal input from the first input / output port 01 reaches the first end 201 of the directional coupler, and then most of the signal power is input to the first end 301 of the limiter circuit through the second end 202 of the directional coupler, and a small part of the power is passed to the first end 501 of the detector circuit through the third end 203 of the directional coupler. The detector circuit 50 detects the signal input from the directional coupler 20 into a DC detection voltage and sends it to the first end 601 of the amplifier through the second end 502 of the detection circuit. The amplifier 60 amplifies the DC detection voltage obtained by the detection and sends it to the first end 701 of the comparator through the second end 602 of the amplifier. In the comparator 70, the amplified DC detection voltage is compared with the reference level of the comparator 70 to generate a high / low level, and the second end 702 of the comparator outputs the high / low level to provide a DC bias to the limiter circuit 30. When the DC detection voltage amplified by the amplifier 60 is lower than the reference level of the comparator 70, the comparator 70 outputs a low level, providing a zero bias or a negative bias voltage to the limiter circuit 30. The zero bias or the negative bias voltage can increase the limiter level of the limiter circuit 30. At this time, the signal input from the first input / output port 01 can pass smoothly. When the DC detection voltage amplified by the amplifier 60 is higher than the reference level of the comparator 70, the comparator 70 outputs a high level, providing a forward bias voltage to the limiter circuit 30. The forward bias voltage can reduce the limiter level of the limiter circuit 30. At this time, when the signal power input from the second end 202 of the directional coupler to the first end 301 of the limiter circuit is less than the limiter level, the signal is output through the limiter circuit 30 to the second input / output port 02 with almost no loss. When the signal power input from the second end 202 of the directional coupler to the first end 301 of the limiting circuit is greater than or equal to the starting limit level, the limiting circuit 30 starts limiting, and the signal power input from the directional coupler 20 to the limiting circuit 30 is limited to a required range before being output to the second input / output port 02. The limiting to the required range means that at least the output level of the second input / output port 02 is required to be lower than the withstand power of the transmitter or the transceiver switch to prevent the transmitter or the transceiver switch from being damaged.

[0040] When the signal is input from the second input / output port 02, the third end 203 of the directional coupler is the isolation port of the directional coupler 20. The signal input from the second input / output port 02 is input to the limiting circuit 30 via the second end 302 of the limiting circuit. In order to prevent the signal from passing through the third end 303 of the limiting circuit to the second end 702 of the comparator, an inductor is usually connected in series to the third end 303 of the limiting circuit and then connected to the second end 702 of the comparator. The signal input from the second input / output port 02 to the limiting circuit 30 is transmitted to the directional coupler 20 via the first end 301 of the limiting circuit and the second end 202 of the directional coupler. Since the directional coupler 20 has good directivity, most of the signal power is output to the first input / output port 01 via the first end 201 of the directional coupler, and a small part of the signal power is input to the detection circuit 50 via the third end 203 of the directional coupler. Moreover, the signal power input from the third terminal 203 of the directional coupler to the first terminal 501 of the detection circuit is smaller than that when the signal is input from the first input / output port 01, and a very small part of the power is input to the detection circuit 50, which is determined by the directional coupler itself. The detection circuit 50 detects the signal input from the directional coupler 20 into a DC detection voltage and sends it to the first terminal 601 of the amplifier through the second terminal 502 of the detection circuit. The amplifier 60 amplifies the DC detection voltage obtained by the detection and sends it to the first terminal 701 of the comparator through the second terminal 602 of the amplifier. In the comparator 70, the amplified DC detection voltage is compared with the reference level of the comparator 70 to generate a high / low level, and the second terminal 702 of the comparator outputs the high / low level to provide a DC bias to the limiter circuit 30. Since the energy input from the third end 203 of the directional coupler to the first end 501 of the detection circuit is smaller than when the signal is input from the first input / output port 01, the DC bias provided to the limiter circuit 30 is also smaller than when the signal is input from the first input / output port 01. At this time, the limiter level of the limiter circuit 30 is relatively higher than when the signal is input from the first input / output port 01. The limiter level at this time is higher than the transmission power of the transmitter. At this time, the signal input from the second input / output port 02 passes smoothly.

[0041] Reference Figure 2 The non-reciprocal limiter provided in one embodiment mainly includes a transmitting and receiving common path, wherein the transmitting and receiving common path includes a first input / output terminal, a first matching circuit 10, a directional coupler 20, a limiting circuit 30, a second matching circuit 40 and a second input / output terminal connected in sequence, and a detection circuit 50, an amplifier 60 and a comparator 70 are connected between the directional coupler 20 and the limiting circuit 30.

[0042] Figure 2In the embodiment, the first input / output end includes a first input / output port 01 and a first matching circuit 10, and the first matching circuit 10 is used to achieve impedance matching. The first matching circuit 10 is usually composed of a transmission line and a DC blocking capacitor, and its function is to prevent direct current from passing through and match the impedance of the first input / output port 01 to a set value (such as 50 ohms) to reduce the insertion loss of the non-reciprocal limiter.

[0043] Figure 2 In the embodiment, the second input / output end includes a second input / output port 02 and a second matching circuit 40, and the second matching circuit 40 is used to achieve impedance matching. The second matching circuit 50 is usually composed of a transmission line and a DC blocking capacitor, and its function is to prevent direct current from passing through and match the impedance of the second input / output port 02 to a set value (such as 50 ohms) to reduce the insertion loss of the non-reciprocal limiter.

[0044] The first input / output port 01 is connected to the first end 101 of the first matching circuit, the second end 102 of the first matching circuit is connected to the first end 201 of the directional coupler, the second end 202 of the directional coupler is connected to the first end 301 of the limiter circuit, the third end 203 of the directional coupler is connected to the first end 501 of the detection circuit, and the second end 502 of the detection circuit is connected to the third end 303 of the limiter circuit. The second end 302 of the limiter circuit is connected to the first end 401 of the second matching circuit, and the second end 402 of the second matching circuit is connected to the second input / output port 02. The directional coupler 20 has four ports, and the fourth end of the directional coupler is usually connected to a 50 ohm resistor connected to ground. Figure 2 Not drawn in.

[0045] Similarly, when the transmitting and receiving common path receives a signal from the first input / output port 01, the third end 203 of the directional coupler is the coupling port of the directional coupler 20. At this time, the signal power input from the third end 203 of the directional coupler to the detection circuit 30 is relatively large. At this time, the logarithm of the ratio of the output power of the third end 203 of the directional coupler to the input power of the first end 201 of the directional coupler is recorded as the coupling degree C; when the signal enters from the second input / output port 02 and transmits from the first input / output port 01, the third end 203 of the directional coupler is the isolation port of the directional coupler 20. At this time, the signal power input from the third end 203 of the directional coupler to the detection circuit 30 is relatively small. At this time, the logarithm of the ratio of the output power of the third end 203 of the directional coupler to the input power of the second end 202 of the directional coupler is recorded as the isolation degree I. The difference between the coupling degree C and the isolation degree I is usually recorded as the directivity D.

[0046] The directional coupler 20 is required to have good directivity, usually above 8dB. The directional coupler 20 is required to have a lower coupling degree, usually below -7dB, to prevent excessive insertion loss of the limiter. The directional coupler 20 can be one of a parallel line directional coupler, a branch line directional coupler and a Lange directional coupler. The directivity of the directional coupler can be improved by introducing a microstrip coupling edge sawtooth structure, introducing an inductor and capacitor element compensation technology, and loading a short stub technology at the coupling end.

[0047] For electronic devices such as radars with integrated transceivers, the first input / output port 01 is usually connected to the transceiver antenna via a feeder; for electronic devices such as radars with separate transceivers, the first input / output port 01 is usually connected to the transmitting antenna via a feeder. According to the dielectric substrate, processing technology and performance index requirements, the first input / output port 01 can be selected to use one of the SMA type connector, N type connector, TNC type connector, BNC type connector, and SSMA type connector.

[0048] For electronic devices such as radars with integrated transceivers, the second input / output port 02 is usually connected to a transceiver switch via a feeder; for electronic devices such as radars with separate transceivers, the second input / output port 02 is usually connected to a transmitter via a feeder. According to the dielectric substrate, processing technology and performance index requirements, the second input / output port 02 can be selected to use one of an SMA connector, an N connector, a TNC connector, a BNC connector, and an SSMA connector.

[0049] The detection circuit 50 is used to detect the DC detection voltage. The detection circuit 50 can be composed of a Schottky diode and a capacitor connected in series and in parallel. To ensure the detection efficiency, the number of Schottky diodes is generally controlled to be 1 to 6.

[0050] The amplifier 60 is used to amplify the DC detection voltage output by the detection circuit to prevent the detection voltage from being too small to be compared. An operational amplifier circuit composed of transistors or field effect transistors is usually used.

[0051] The comparator 70 is used to compare the output voltage of the amplifier with its reference level, thereby outputting a high / low level to provide a DC bias to the limiting circuit. A voltage comparator is usually used.

[0052] The amplifier circuit is used to amplify the detection voltage. By setting the amplifier circuit, the present invention can reduce the signal power input from the directional coupler to the detection circuit under the same detection effect, reduce the insertion loss of the non-reciprocal limiter, and reduce the impact on the transmission power compared to the design of the non-reciprocal limiter without an amplifier.

[0053] The present invention adopts a comparator, and the comparator can flexibly set the reference level and flexibly adjust the starting level of the limiter circuit when receiving the signal. The comparator can also output a high / low level, the high level is a positive voltage, which reduces the starting level of the limiter circuit, and the low level can be zero or a negative voltage. By applying a reverse bias to the limiter circuit, the starting level of the limiter circuit is raised. In this way, when the signal power is small, the transmission and reception of the low-power signal are not affected, and both can be carried out normally, but the starting level of the limiter circuit when transmitting the signal is relatively raised.

[0054] The limiting circuit 30 usually includes 1 to 3 levels of limiting structures, and the limiting structures are usually connected by a quarter-wavelength transmission line. Each level of limiting structure is composed of multiple limiting units in parallel. Each level of limiting structure has several limiting units in parallel, which can improve the isolation of the limiter. Usually, each level of limiting structure includes 1 to 3 parallel limiting units. Each limiting unit in the limiting circuit is composed of multiple PIN diodes connected in series. By changing the number and model of the PIN diodes in series, the starting and limiting level during transmission can be flexibly adjusted. Each limiting unit usually includes 1 to 9 PIN diodes in series. The PIN diodes in the same limiting unit should be of the same model, and diodes with higher starting and limiting levels are preferred.

[0055] When a signal is input from the first input / output port 01, the signal passes through the first matching circuit 10 and reaches the first end 201 of the directional coupler. After that, most of the signal power is input to the first end 301 of the limiter circuit through the second end 202 of the directional coupler, and a small part of the power is passed to the first end 501 of the detection circuit through the third end 203 of the directional coupler. The detection circuit 50 detects the signal input from the directional coupler 20 into a DC detection voltage and passes it to the amplifier 60. The amplifier 60 amplifies the detection voltage and passes it to the comparator 70 and compares it with the reference level of the comparator 70. The comparator 70 outputs a high / low level to provide a DC bias to the limiter circuit 30, changing the limiter level of the limiter circuit. When the amplified detection voltage is lower than the reference level of the comparator, the comparator outputs a low level, providing a zero bias or a negative bias to the limiter circuit. The zero bias or the negative bias can increase the limiter level of the limiter circuit. At this time, the signal input from the first input / output port 01 can pass smoothly. When the amplified detection voltage is higher than the reference level of the comparator, the comparator outputs a high level, providing a forward bias voltage to the limiter circuit. The forward bias voltage can reduce the limiter level of the limiter circuit. At this time, when the signal power input from the second end 202 of the directional coupler to the first end 301 of the limiter circuit is less than the limiter level, the signal passes through the limiter circuit 30 to the second matching circuit 40 with almost no loss, and is output through the second matching circuit 40 to the second input / output port 02. When the signal power input from the second end 202 of the directional coupler to the first end 301 of the limiter circuit is greater than or equal to the limiter level, the limiter circuit 30 starts to limit the signal power input from the directional coupler 20 to the limiter circuit 30 within the required range and outputs it to the second matching circuit 40. Finally, the signal is output from the limiter circuit 30 to the second input / output port 02 through the second matching circuit 40. It is required that the output level at this time is lower than the withstand power of the transmitter or the transceiver switch to prevent the transmitter or the transceiver switch from being damaged.

[0056] When a signal is input from the second input / output port 02, the signal reaches the limiter circuit 30 through the second matching circuit 40. In order to prevent the signal from passing through the third terminal 303 of the limiter circuit to the second terminal 702 of the comparator, an inductor is usually connected in series to the third terminal 303 of the limiter circuit and then connected to the second terminal 702 of the comparator. At this time, the signal input from the second matching circuit 40 to the limiter circuit 30 is output to the directional coupler 20. Since the directional coupler 20 has good directivity, the power input from the third terminal 203 of the directional coupler to the first terminal 501 of the detection circuit is smaller than when the signal is input from the first input / output port 01, so a large part of the power of the signal input to the directional coupler 20 is input to the first matching circuit 10, and a small part of the power is input to the detection circuit 50. The detection circuit 50 detects the signal input from the directional coupler 20 into a DC detection voltage and passes it to the amplifier 60. The amplifier 60 amplifies the detection voltage and passes it to the comparator 70 for comparison with the reference level of the comparator 70. The comparator 70 outputs a high / low level to provide a DC bias to the limiter circuit 30. Since the energy input from the third terminal 203 of the directional coupler to the first terminal 501 of the detection circuit is smaller than when the signal is input from the first input / output port 01, the DC bias provided to the limiter circuit 30 is also smaller than when the signal is input from the first input / output port 01. At this time, the limit level of the limiter circuit 30 is relatively higher than when the signal is input from the first input / output port 01. It is required that the limit level at this time is higher than the transmission power of the transmitter.

[0057] Therefore, when the signal is input from the first input / output port 01 (receiving signal state), the limiting level of the signal output from the second input / output port 02 by the non-reciprocal limiter is lower than the tolerance power of the transmitter or the transceiver switch, which can effectively protect the transmitter or the transceiver switch; when the signal is input from the second input / output port 02 (transmitting signal state), the starting level of the non-reciprocal limiter is higher than the transmission power of the transmitter, ensuring that the transmission signal passes normally.

[0058] Reference Figure 3 , which is a circuit structure diagram of a non-reciprocal limiter provided in one embodiment of the present invention, comprising a first input / output port 01, a first matching circuit 10, a directional coupler 20, a limiting circuit 30, a second matching circuit 40, a detection circuit 50, an amplifier 60, a comparator 70 and a first input / output port 02.

[0059] In one embodiment, the first input / output port 01 is connected to the first end 101 of the first matching circuit, and the second end 102 of the first matching circuit is connected to the first end 201 of the directional coupler. The first matching circuit 10 is usually composed of a transmission line and a DC blocking capacitor, and its function is to prevent direct current from passing through and match the impedance of the first input / output port 01 to 50 ohms to reduce the insertion loss of the non-reciprocal limiter. The first end 501 of the second matching circuit is connected to the second end 402 of the limiting circuit, and the second end 502 of the second matching circuit is connected to the second input / output port 02. The second matching circuit 50 is usually composed of a transmission line and a DC blocking capacitor, and its function is to prevent direct current from passing through and match the impedance of the second input / output port 02 to 50 ohms.

[0060] In one embodiment, the directional coupler 20 is a Lange directional coupler, and the directional coupler 20 has four ports, wherein the first end 201 of the directional coupler is connected to the second end 102 of the first matching circuit, the second end 202 of the directional coupler is connected to the first end of the limiter circuit, the third end 203 of the directional coupler is connected to the first end of the detection circuit, the fourth end of the directional coupler is connected to the first end of the first resistor 211, and the second end of the first resistor 211 is grounded. In one embodiment, the first resistor 211 is a 50 ohm resistor.

[0061] In one embodiment, the detection circuit 50 is composed of a first capacitor 511, a second capacitor 512, a first Schottky diode 521, and a second Schottky diode 522, wherein the first Schottky diode 521 and the second Schottky diode 522 are Schottky diodes of the same type. The positive electrode of the first capacitor 511 is connected to the third terminal 203 of the directional coupler, the negative electrode of the first capacitor 511 is connected to the negative electrode of the first Schottky diode 521 on one hand, the positive electrode of the first Schottky diode 521 is grounded, the negative electrode of the first capacitor 511 is connected to the positive electrode of the second Schottky diode 522 on the other hand, the negative electrode of the second Schottky diode 522 is connected to the first terminal 601 of the amplifier on one hand, the negative electrode of the second Schottky diode 522 is connected to the positive electrode of the second capacitor 512 on the other hand, and the negative electrode of the second capacitor 512 is grounded.

[0062] In one embodiment, the amplifier 60 is a common-mode proportional operational amplifier, which is composed of a first resistor 611, a second resistor 612, a third resistor 613, an amplifier chip 621 and an external voltage source of the chip. Figure 3The positive electrode of the first resistor 611 is used as the first end 601 of the amplifier, and the negative electrode of the second Schottky diode 522 in the detection circuit 50 is connected to the positive electrode of the first resistor 611. The negative electrode of the first resistor 611 is connected to the positive electrode of the amplifier chip 621. The output end of the amplifier chip 621 is connected to the comparator 70 on one hand, and the output end of the amplifier chip 621 is connected in series with the second resistor 612 and the third resistor 613 on the other hand. The other end of the third resistor 613 is grounded, and the negative electrode of the amplifier chip 621 is connected between the second resistor 612 and the third resistor 613. The gain of the amplifier can be changed by changing the second resistor 612 and the third resistor 613.

[0063] In one embodiment, the comparator 70 is a voltage comparator, which is composed of a first resistor 711, a second resistor 712, a first voltage source 721, a comparator chip 731 and an external voltage source of the chip. Figure 2 Not shown in the figure. The output terminal of the amplifier chip 621 is connected to the positive electrode of the comparator chip. The first voltage source 721 is connected to the positive electrode of the first resistor 711, the negative electrode of the second resistor 711 is connected to the negative electrode of the comparator chip, and one end of the second resistor 712 is grounded, and the other end is connected to the negative electrode of the comparator chip. Among them, the reference level of the negative electrode of the comparator can be changed by changing the first resistor 711 and the second resistor 712. Since the amplified detection voltage is compared with the reference level, by setting the reference level of the comparator 70 and the high / low level of the output, the starting level of the non-reciprocal limiter when sending and receiving signals can be flexibly adjusted.

[0064] In one embodiment, the limiting circuit 30 includes a 1-stage limiting structure, in which there is a parallel limiting unit, and the limiting unit includes three PIN diodes connected in series, namely a first PIN diode 311, a second PIN diode 312, and a third PIN diode 313. The first PIN diode 311, the second PIN diode 312, and the third PIN diode 313 are PIN diodes of the same model. The positive electrode of the first PIN diode 311 is connected to the transmission line, the negative electrode of the first PIN diode 311 is connected to the positive electrode of the second PIN diode 312, the negative electrode of the second PIN diode 312 is connected to the positive electrode of the third PIN diode 313, and the negative electrode of the third PIN diode 313 is grounded. The limiting circuit 30 also includes an inductor 321 connected to the second end 702 of the comparator.

[0065] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A non-reciprocal limiter, characterized in that: The invention comprises a common transmission and reception path, wherein the common transmission and reception path comprises a first input / output terminal, a directional coupler, a limiter circuit and a second input / output terminal connected in sequence, a detection circuit, an amplifier and a comparator are connected between the directional coupler and the limiter circuit, the directional coupler couples part of the energy from the common transmission and reception path and sends it to the detection circuit, the detection circuit detects the signal input from the directional coupler into a DC detection voltage, the amplifier amplifies the detection voltage and inputs it to the comparator for comparison with its reference level, and then the comparator outputs a high / low level to provide a DC bias to the limiter circuit to change the limiter circuit's threshold level; by utilizing the directivity of the directional coupler, when the common transmission and reception path transmits a signal, the limiter circuit's threshold level is higher than the transmission power, and the transmission signal passes normally; when the common transmission and reception path receives a signal, once the power of the received signal input from the directional coupler to the limiter circuit is greater than or equal to the threshold level of the limiter circuit, the limiter circuit starts to limit the signal power input from the directional coupler to the limiter circuit within a required range; The first input / output end includes a first input / output port and a first matching circuit, the first input / output port is connected to a first end of the first matching circuit, a second end of the first matching circuit is connected to a first end of the directional coupler, and the first matching circuit is used to achieve impedance matching; When the transmit-receive common path receives a signal from the first input / output port, if the power of the received signal input from the third end of the directional coupler to the limiting circuit is less than the limiting level of the limiting circuit, the received signal passes through the limiting circuit to the second matching circuit with low loss or even without loss; if the power of the signal input from the directional coupler to the limiting circuit is greater than or equal to the limiting level of the limiting circuit, the limiting circuit starts limiting and limits the power of the signal input from the directional coupler to the limiting circuit to a level lower than the tolerable power of the transmitter or the transmit-receive switch.

2. The non-reciprocal limiter according to claim 1, characterized in that: The first input / output terminal is connected to the first terminal of the directional coupler, the second terminal of the directional coupler is connected to the first terminal of the limiter circuit, the third terminal of the directional coupler is connected to the first terminal of the detector circuit, the second terminal of the detector circuit is connected to the first terminal of the amplifier, the comparator has two input terminals, namely the first terminal of the comparator and the third terminal of the comparator, the second terminal of the amplifier is connected to the first terminal of the comparator, the reference level is input from the third terminal of the comparator, the second terminal of the comparator serves as the output terminal of the comparator, the second terminal of the comparator is connected to the third terminal of the limiter circuit, the second terminal of the limiter circuit is connected to the second input / output terminal, when the transmit-receive common path transmits a signal from the first input / output port, the third terminal of the directional coupler is the isolation port of the directional coupler; when the transmit-receive common path receives a signal from the first input / output port, the third terminal of the directional coupler is the coupling port of the directional coupler.

3. The non-reciprocal limiter according to claim 1, characterized in that: The second input / output end includes a second input / output port and a second matching circuit. The second input / output port is connected to the second end of the second matching circuit. The first end of the second matching circuit is connected to the second end of the limiting circuit. The second matching circuit is used to achieve impedance matching.

4. The non-reciprocal limiter according to claim 1, characterized in that: The directional coupler is one of a parallel line directional coupler, a branch line directional coupler and a Lange directional coupler.

5. The non-reciprocal limiter according to any one of claims 1 to 4, characterized in that: The detection circuit is formed by connecting a plurality of Schottky diodes and capacitors in series and in parallel.

6. The non-reciprocal limiter according to claim 5, characterized in that: The amplifier adopts an operational amplifier circuit composed of transistors or field effect tubes.

7. The non-reciprocal limiter according to claim 6, characterized in that: The limiting circuit includes 1 to 3 levels of limiting structures, and each level of limiting structures is connected through a quarter-wavelength transmission line.

8. The non-reciprocal limiter according to claim 7, characterized in that: Each level of the limiting structure includes 1 to 3 limiting units connected in parallel, and each limiting unit includes 1 to 9 PIN diodes of the same type connected in series.

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