Broadband amplitude limiter with adjustable threshold

Abstract

The utility model discloses a broadband amplitude limiter with an adjustable threshold, which comprises an input port, an output port, an amplitude limiting unit and an adjusting unit, the amplitude limiting unit comprises a first diode and a second diode, the first diode and the second diode are reversely connected in parallel and are used for limiting the amplitude of radio frequency signals input by the input port, and the adjusting unit is used for adjusting the amplitude of the radio frequency signals input by the output port. The anode of the first diode is electrically connected between the input port and the output port, and the cathode of the first diode is grounded; the anode of the second diode is grounded, and the cathode of the second diode is electrically connected between the input port and the output port; the adjusting unit comprises a radio frequency choking coil and an operational amplifier, the first end of the radio frequency choking coil is electrically connected with the output end of the operational amplifier, and the second end is electrically connected with the anode of the second diode; the adjusting unit is configured to control the conduction threshold of the second diode based on the magnitude of the direct current bias voltage input from the non-inverting input end of the operational amplifier. By means of the design, the wide amplitude limiting threshold and the high response speed can be achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of radio frequency microwaves, in particular to a broadband limiter with adjustable threshold. Background Art

[0002] The limiter is an important control unit in the RF microwave system. Its main purpose is to prevent high-power signals from damaging the RF microwave components in normal operation, such as the low-noise amplifier at the front end of the receiver. The limiter is placed at the front end of the system to absorb or reflect RF microwave energy. It is widely used in radar, wireless communication, test and measurement, drones, aviation and navigation, and mass consumer applications.

[0003] Currently, most of the limiters available on the market are fixed-threshold limiters. Limiters with adjustable thresholds also add a DC bias voltage to the PIN diode and achieve the purpose of threshold adjustment by controlling the conduction threshold of the PIN diode.

[0004] However, the problem is that the threshold is adjusted only by controlling the bias voltage of the PIN diode, the threshold range is narrow, and due to the characteristics of the PIN diode itself, the response speed is not fast.

[0005] Therefore, the above problems need to be solved urgently by those skilled in the art. Utility Model Content

[0006] In order to solve the technical defects mentioned in the above background technology, the purpose of the utility model is to provide a broadband limiter with adjustable threshold, which has a wider limiting threshold and a faster response speed.

[0007] The utility model adopts the following technical solutions:

[0008] A broadband limiter with adjustable threshold, comprising:

[0009] Input port, used for inputting radio frequency signal;

[0010] Output port, used for outputting the limited RF signal;

[0011] A limiting unit, the limiting unit comprising a first diode and a second diode, the first diode and the second diode are connected in reverse parallel and are used to limit the RF signal inputted from the input port, the anode of the first diode is electrically connected between the input port and the output port, and the cathode is grounded; the anode of the second diode is grounded, and the cathode is electrically connected between the input port and the output port;

[0012] An adjustment unit, the adjustment unit comprising a radio frequency choke and an operational amplifier, a first end of the radio frequency choke being electrically connected to an output end of the operational amplifier, and a second end being electrically connected to an anode of the second diode; wherein the adjustment unit is configured to control a conduction threshold of the second diode based on a DC bias voltage input from a non-inverting input end of the operational amplifier.

[0013] Optionally, it also includes an RF bypass capacitor, one end of which is electrically connected to the anode of the second diode and the other end is grounded; wherein the RF bypass capacitor is used to bypass the RF signal to provide an RF current path.

[0014] Optionally, it also includes a first DC blocking capacitor, a first end of which is electrically connected to the input port, and a second end of which is electrically connected to the output port; a second DC blocking capacitor, a first end of which is electrically connected to the second end of the first DC blocking capacitor, and a second end of which is electrically connected to the output port; wherein the first DC blocking capacitor and the second DC blocking capacitor are connected in series to isolate the DC current of the RF signal transmitted by the input port.

[0015] Optionally, the first diode is a PIN diode.

[0016] Optionally, the second diode is a Schottky diode.

[0017] In summary, the beneficial effects of the utility model are:

[0018] 1. By setting the first diode and the second diode in the limiting unit to be connected in reverse parallel, the RF signal inputted from the input port can be limited. At the same time, by setting the RF choke in the adjustment unit to be electrically connected to the operational amplifier, the DC bias voltage inputted through the same-direction input terminal of the operational amplifier is transmitted to the RF choke through the output terminal, and then outputted to the anode of the second diode, so that the conduction threshold of the second diode can be controlled, making its threshold range wider;

[0019] 2. By setting the second diode as a Schottky diode, since the Schottky diode has a lower conduction voltage and a faster response speed, the direct current of the conducted Schottky diode is used to start the conduction state of the first diode. Compared with the basic PIN limiting circuit, the first diode and the second diode connected in reverse parallel have a lower limiting threshold and a faster response speed for the limiter.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the circuit structure of an embodiment of the utility model.

[0022] Description of reference numerals in the figures:

[0023] 1. Limiting unit; 2. Adjusting unit; D1, first diode; D2, second diode; L1, RF choke; U1, operational amplifier; C1, first DC blocking capacitor; C2, RF bypass capacitor; C3, second DC blocking capacitor. DETAILED DESCRIPTION

[0024] In order to make the content of the utility model more clearly understood, the utility model is further described below based on specific embodiments in combination with the accompanying drawings.

[0025] It should be noted that the terms "center", "upper", "lower", "front", "back", "left", "right", "inner", "outer" and the like used herein to indicate directions or positional relationships are based on directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. Unless otherwise specified, "plurality" means two or more.

[0026] Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this utility model can be understood by specific circumstances.

[0027] like Figure 1As shown, an embodiment of the present application provides a threshold-adjustable bandwidth limiter, a threshold-adjustable broadband limiter, comprising an input port, an output port, a limiting unit 1 and an adjusting unit 2, wherein the input port is used to input a radio frequency signal; the output port is used to output a limited radio frequency signal; the limiting unit 1 comprises a first diode D1 and a second diode D2, the first diode D1 and the second diode D2 are reversely connected in parallel and used to limit the radio frequency signal inputted from the input port, the anode of the first diode D1 is electrically connected between the input port and the output port, and the cathode is grounded; the anode of the second diode D2 is grounded, and the cathode is electrically connected between the input port and the output port; the adjusting unit 2 comprises a radio frequency choke L1 and an operational amplifier U1, the first end of the radio frequency choke L1 is electrically connected to the output end of the operational amplifier U1, and the second end is electrically connected to the anode of the second diode D2; wherein the adjusting unit 2 is configured to control the conduction threshold of the second diode D2 based on the magnitude of the DC bias voltage inputted from the same-direction input end of the operational amplifier U1.

[0028] In the embodiment of the present application, the above-mentioned input port is used to input the RF signal that needs to be limited. After the RF signal is transmitted, it is limited by the first diode D1, wherein the first diode D1 can be a PIN diode; wherein, it should be noted that the PIN diode has a characteristic, that is, when a certain DC current (forward bias) flows through the PIN diode, its impedance is very low, equivalent to a small resistor; when no DC current (reverse bias) flows through the PIN diode, its impedance is very large, equivalent to a small capacitor. When the frequency increases, the carrier lifetime inside the diode cannot keep up with the frequency change of the external signal. Therefore, at high frequencies, the PIN diode loses its unidirectional conduction function. Even if the amplitude of the RF signal has exceeded the DC conduction voltage of the PIN diode, it still cannot cause the PIN diode to conduct. Therefore, the PIN diode can withstand higher RF signal power. Only when the RF signal power applied to the PIN diode is strong enough, resulting in the average number of carriers accumulated inside the diode being large enough to cross the I layer (intrinsic layer) of the PIN diode and form a DC current on the PIN diode can it enter the on state. At the same time, in order to maintain the on state, there must be a DC path that can maintain the flow of DC current.

[0029] Therefore, by setting a limiting unit 1, wherein the limiting unit 1 may include a second diode D2 and a first diode D1, and the second diode D2 and the first diode D1 are reversely connected in parallel, the DC current flow can be maintained to form a DC loop. By setting the second diode D2, the frequency characteristic requirements can be lowered, thereby improving the bandwidth of this embodiment.

[0030] At the same time, since the first diode D1 and the second diode D2 are connected in reverse parallel, when the first diode D1 and the second diode D2 are turned on, they present a very low impedance, so that the standing wave seen from the input port is very large, and most of the input RF energy is reflected back, so that the RF signal reaching the output port is very weak, thereby limiting the size of the RF signal and protecting the circuit connected to the output port.

[0031] The above-mentioned adjustment unit 2 may include an RF choke L1 and an operational amplifier U1, wherein the non-inverting input terminal of the above-mentioned operational amplifier U1 is used to input a DC bias, and the reverse input terminal is electrically connected to the first end of the RF choke L1, and the output terminal of the operational amplifier U1 is also electrically connected to the first end of the RF choke L1. By setting the RF choke L1 to be electrically connected to the anode of the second diode D2, the DC bias is transmitted from the RF choke L1 to the anode of the second diode D2 through the follower buffer formed by the operational amplifier U1, thereby increasing or decreasing the size of the DC bias to control the conduction threshold of the second diode D2, thereby achieving an adjustable threshold and a wider threshold range; at the same time, by setting the second diode D2, since the Schottky diode has a lower conduction voltage and a faster response speed, the present embodiment has a faster response speed when limiting.

[0032] like Figure 1 As shown, the embodiment of the present application also includes an RF bypass capacitor C2, one end of which is electrically connected to the anode of the second diode D2, and the other end is grounded; wherein the RF bypass capacitor C2 is used to bypass the RF signal to provide an RF current path.

[0033] like Figure 1 As shown, the embodiment of the present application also includes a first DC blocking capacitor C1, a first end of which is electrically connected to the input port, and a second end of which is electrically connected to the output port; a second DC blocking capacitor C3, a first end of which is electrically connected to the second end of the first DC blocking capacitor C1, and a second end of which is electrically connected to the output port; wherein the first DC blocking capacitor C1 and the second DC blocking capacitor C3 are connected in series to isolate the DC current of the RF signal transmitted by the input port.

[0034] In the embodiment of the present application, one end of the above-mentioned RF bypass capacitor C2 is electrically connected to the anode of the second diode D2 and the second end of the RF choke L1, and the RF bypass capacitor C2 is used to bypass the RF signal to provide an RF current path; it should be noted that when a large RF signal is input from the input port, the bypass RF capacitor and the second diode D2 and the first DC blocking capacitor C1 constitute an RF signal path, and the conduction threshold of the second diode D2 is controlled by a DC bias. Once the amplitude of the input RF signal exceeds the conduction threshold of the second diode D2, the second diode D2 is turned on and a DC current is generated in the RF choke L1 and the second diode D2. Since the first DC blocking capacitor C1, the RF bypass capacitor C2 and the second DC blocking capacitor C3 all have a DC blocking effect, the DC current can only pass through the first diode D1. At this time, the first diode D1 is turned on and the circuit enters a limiting state. At the same time, the DC bias voltage can be positive or negative. When the DC bias voltage increases, the clipping threshold is reduced; when the DC bias voltage decreases, the clipping threshold is increased. Therefore, the embodiment of the present application has a wider clipping threshold range.

[0035] Specifically, in the embodiment of the present application, the first diode D1 is a PI N diode, and the second diode D2 is a Schottky diode; by setting the second diode D2 as a Schottky diode, the Schottky diode has a lower conduction voltage and a faster response speed. When a high-power RF signal is input from the input port, the second diode D2 is first turned on, and a DC current is generated after the conduction. The DC current passes through the output of the operational amplifier U1, the RF choke L1, the second diode D2 and the first diode D1 to form a loop. Once a DC current flows through the first diode D1, the first diode D1 quickly enters the conduction state, so that the entire circuit has a lower impedance and can reflect the RF energy to the maximum extent. Since the DC of the turned-on Schottky diode is used to start the conduction state of the PI N diode, compared with the basic PI N limiting circuit, the reverse parallel PI N and Schottky diodes have a lower limiting threshold and a faster response speed for the limiter.

[0036] The embodiments of this specific implementation are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. The same components are represented by the same figure marks. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A broadband limiter with adjustable threshold, characterized in that: include: Input port, used for inputting radio frequency signal; Output port, used for outputting the limited RF signal; A limiting unit (1), the limiting unit (1) comprising a first diode (D1) and a second diode (D2), the first diode (D1) and the second diode (D2) being connected in reverse parallel and used for limiting the amplitude of a radio frequency signal inputted from an input port, the anode of the first diode (D1) being electrically connected between the input port and the output port, and the cathode being grounded; the anode of the second diode (D2) being grounded, and the cathode being electrically connected between the input port and the output port; An adjustment unit (2), the adjustment unit (2) comprising a radio frequency choke (L1) and an operational amplifier (U1), a first end of the radio frequency choke (L1) being electrically connected to the output end of the operational amplifier (U1), and a second end of the radio frequency choke (L1) being electrically connected to the anode of the second diode (D2); wherein the adjustment unit (2) is configured to control the conduction threshold of the second diode (D2) based on the magnitude of a DC bias voltage input from the non-inverting input end of the operational amplifier (U1).

2. A broadband limiter with adjustable threshold according to claim 1, characterized in that: It also includes a radio frequency bypass capacitor (C2) with one end electrically connected to the anode of the second diode (D2) and the other end grounded; wherein the radio frequency bypass capacitor (C2) is used to bypass the radio frequency signal to provide a radio frequency current path.

3. The broadband limiter with adjustable threshold according to claim 1, characterized in that: Also includes: a first DC blocking capacitor (C1), a first end of which is electrically connected to the input port, and a second end of which is electrically connected to the output port; A second DC blocking capacitor (C3), a first end of which is electrically connected to the second end of the first DC blocking capacitor (C1), and a second end of which is electrically connected to the output port; wherein the first DC blocking capacitor (C1) and the second DC blocking capacitor (C3) are connected in series to isolate the DC current of the radio frequency signal transmitted by the input port.

4. The broadband limiter with adjustable threshold according to claim 1, characterized in that: The first diode (D1) is a PIN diode.

5. The broadband limiter with adjustable threshold according to claim 1, characterized in that: The second diode (D2) is a Schottky diode.

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