Miniaturized lightning protection amplitude limiting device for specific frequency band

Abstract

The invention discloses a miniaturized lightning protection amplitude limiting device for a specific frequency band, belongs to the technical field of amplitude limiting circuits, solves the problem that an existing miniaturized amplitude limiting circuit cannot limit the amplitude of a high-power signal of the specific frequency band, and comprises an inductor and a capacitor which are connected in parallel, one end of each inductor is connected to a signal input end, and the other end of each inductor is grounded. The other end of the capacitor is sequentially connected with two stages of amplitude limiters in series and then connected to the signal output end, and both the two stages of amplitude limiters adopt PIN diodes. By arranging the broadband matching circuit composed of the inductor and the capacitor, selection of a specific frequency band can be met, meanwhile, the capacitor has a direct current blocking function, the capacitor and the inductor with direct current and alternating current blocking characteristics in a low frequency band can form a miniaturized lightning protection circuit, when radio frequency lightning instantaneous overvoltage comes, the inductor is conducted to discharge lightning current to the ground, and therefore the lightning protection circuit is safe and reliable. And the output power of the high-power signal is limited in a safe range through a two-stage amplitude limiter adopting a PIN diode, so that a rear-end receiver is protected from being damaged by lightning current or the high-power signal.

Description

Technical Field

[0001] The invention belongs to the technical field of amplitude limiting circuits, and in particular relates to a miniaturized lightning protection amplitude limiting device for a specific frequency band. Background Art

[0002] A limiting circuit is a circuit that can flatten the signal voltage amplitude within a limited range, also known as a limiter or clipper. Most of the existing limiting circuits can only meet the full-band limiting requirements, and there is no limiting for a specific frequency band. In addition, existing limiting circuits usually do not have lightning protection design. When the antenna is struck by lightning or electromagnetic pulses, the high-power lightning current pulse will directly damage the limiting circuit, which in turn causes the next-level receiver to be damaged and unable to work normally, resulting in significant property losses. Conventional lightning suppressors use devices such as TVS tubes or gas discharge tubes, which are usually large in size and therefore difficult to miniaturize. Summary of the invention

[0003] The purpose of the present invention is to provide a miniaturized lightning protection limiting device for a specific frequency band, thereby solving the problem that the existing miniaturized limiting circuit cannot limit the high-power signal in the specific frequency band.

[0004] The technical solution adopted by the present invention is: a miniaturized lightning protection limiting device for a specific frequency band, including an inductor and a capacitor connected in parallel, one end of the inductor and the capacitor are both connected to the signal input end, the other end of the inductor is grounded, and the other end of the capacitor is connected in series with two-stage limiters and then connected to the signal output end, and the two-stage limiters both use PIN diodes.

[0005] The present invention is also characterized in that: The broadband matching circuit composed of inductors and capacitors is used to select a specific frequency band. After selecting the target frequency band, the values ​​of the inductors and capacitors to be used are calculated by the following formula: Inductance calculation:

[0006] Capacitance calculation:

[0007] In the formula, R is the characteristic impedance of the broadband matching circuit, f is the target frequency of the broadband matching circuit, L is the inductance of the inductor, C is the capacitance value of the capacitor.

[0008] Inductors and capacitors form a lightning protection circuit.

[0009] Each of the two-stage limiters includes two PIN diodes connected in parallel and having opposite positive and negative poles, and one end of the two PIN diodes away from the capacitor is grounded.

[0010] It is installed on the printed circuit board in a micro-assembly manner. After installation on the printed circuit board, the device size is within 13mm in length, 5.5mm in width and 3mm in height.

[0011] The beneficial effects of the present invention are as follows: the miniaturized lightning protection limiting device for a specific frequency band of the present invention can meet the selection of a specific frequency band by setting a broadband matching circuit composed of an inductor and a capacitor. At the same time, the capacitor has a DC isolation function and can also form a miniaturized lightning protection circuit with an inductor having a DC pass and AC block characteristic in a low frequency band. When a radio frequency lightning instantaneous overvoltage occurs, the inductor is turned on to discharge the lightning current to the ground, and then the output power of the high-power signal is limited to a safe range by using a two-stage limiter using a PIN diode, thereby protecting the back-end receiver from being damaged by the lightning current or the high-power signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a circuit diagram of a miniaturized lightning protection and amplitude limiting device for a specific frequency band of the present invention; Figure 2 This is a 2400MHz to 5900MHz insertion loss simulation diagram of a miniaturized lightning protection and limiting device for a specific frequency band of the present invention; Figure 3 This is a simulation diagram of the insertion loss of the miniaturized lightning protection and limiting device for a specific frequency band of the present invention at 700MHz to 2700MHz; Figure 4 It is a 2400MHz to 5900MHz input and output standing wave simulation diagram of a miniaturized lightning protection and limiting device for a specific frequency band of the present invention; Figure 5 It is a 700MHz-2700MHz input and output standing wave simulation diagram of the miniaturized lightning protection and limiting device for a specific frequency band of the present invention. DETAILED DESCRIPTION

[0013] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] Example 1 The present invention provides a miniaturized lightning protection and limiting device for a specific frequency band, which can achieve lightning protection and limiting effects for a specific frequency band through a lightning protection circuit and a limiter. For the input of low-power signals, the lightning protection circuit is equivalent to an open circuit, and the insertion loss is very small; and for the input of strong electromagnetic pulses, it has two-level protection circuits, namely a lightning protection circuit and a limiter. Compared with a single limiter, it can discharge the pulse more effectively. When used, it is connected in series between the antenna and the receiver to protect the back-end receiver from being damaged by high-power signals. The specific circuit diagram is shown in the figure. Figure 1As shown, it includes a broadband matching circuit, a lightning protection circuit and a limiting circuit, wherein the broadband matching circuit includes a second-order filter composed of an inductor and a capacitor, and the inductor and the capacitor simultaneously constitute the above-mentioned lightning protection circuit, and the limiting circuit is a two-stage limiter composed of PIN diodes. One end of the inductor and the capacitor are both connected to the signal input end, the other end of the inductor is grounded, and the other end of the capacitor is connected in series with the two-stage limiter in sequence and then connected to the signal output end. Each stage of the limiter includes two PIN diodes connected in parallel with opposite positive and negative poles, and the ends of the two PIN diodes away from the capacitor are both grounded.

[0015] The specific technical principle of the miniaturized lightning protection and limiting device for a specific frequency band of the present invention is as follows: 1) By setting a broadband matching circuit composed of inductors and capacitors, the selection of a specific frequency band can be met. According to the calculation formula of the Chebyshev filter, by selecting inductors and capacitors with corresponding parameter specifications, the required target frequency band can be obtained. Since the value range of the inductor and capacitor is large, the broadband matching circuit composed of the inductor and capacitor can have a very wide frequency adjustment space; and since the broadband matching circuit uses a small number of electronic components and small size, it has extremely low insertion loss and standing wave ratio in the target frequency band, and has a certain degree of suppression outside the band.

[0016] According to the calculation formula of the second-order Chebyshev filter, the calculation of the capacitance and inductance values ​​within the target frequency band is as follows: Inductance calculation:

[0017] Capacitance calculation:

[0018] In the formula, R is the characteristic impedance of the broadband matching circuit, f is the target frequency of the broadband matching circuit, L is the inductance of the inductor, C is the capacitance value of the capacitor.

[0019] 2) Inductors and capacitors can form a lightning protection circuit at the same time. Compared with conventional large-sized lightning suppressors, the electronic components of the present invention, namely the inductors and capacitors, are small in size and easy to miniaturize. At the same time, by utilizing the DC isolation function of the capacitor and the DC-passing and AC-blocking characteristics of the inductor in the low-frequency band, the inductor presents a high impedance within the application frequency band and will not affect the transmission of radio frequency signals. When a lightning transient overvoltage with a frequency lower than the application frequency band occurs, the inductor conducts and discharges the lightning current to the ground, so that the lightning current is fully discharged before the limiter, and the DC isolation capacitor will filter out the DC component in the signal, and the residual pressure entering the limiter is small enough to be absorbed by it, thereby protecting the subsequent circuits.

[0020] 3) In the two-stage limiter, the main function of the first-stage limiter close to the capacitor is to limit the high-power microwave signal, and the main function of the second-stage limiter far away from the capacitor is to limit the high-power microwave signal leaked from the first-stage limiter. Both stage limiters use PIN diodes, which have fast recovery time, low clamping voltage, large average power at room temperature, large peak power, large transient power, and small parasitic capacitance. Each stage limiter consists of two parallel PIN diodes with opposite positive and negative poles. In the positive and negative half cycles of the microwave signal, the two PIN diodes alternately provide a DC path for each other to achieve the purpose of limiting. When a low-power signal is input, the PIN diode can be equivalent to a capacitor in the circuit. At this time, the impedance of the PIN diode is the largest, which is equivalent to an open circuit in the circuit. At this time, the insertion loss of the limiter is also the smallest. When the signal power input to the PIN diode gradually increases, the impedance of the PIN diode also changes, and the input signal attenuation also gradually increases. After the input signal passes through the PIN diode for a period of time, the limited output power no longer changes and reaches a flat leakage output, thereby limiting the output power of the high-power signal within a safe range, thereby protecting the back-end receiver from being damaged by the high-power signal.

[0021] Through the above-mentioned manner, the miniaturized lightning protection limiting device for a specific frequency band of the present invention can meet the selection of a specific frequency band by setting a broadband matching circuit composed of an inductor and a capacitor. At the same time, the capacitor has a DC isolation function and can also form a miniaturized lightning protection circuit with an inductor having a DC pass and AC block characteristic in a low frequency band. When a radio frequency lightning instantaneous overvoltage occurs, the inductor is turned on to discharge the lightning current to the ground, and then the output power of the high-power signal is limited to a safe range by using a two-stage limiter using a PIN diode, thereby protecting the back-end receiver from being damaged by the lightning current or the high-power signal.

[0022] Example 2 The present invention provides a miniaturized lightning protection and limiting device for a specific frequency band. The insertion loss and standing wave index simulations in the 2400MHz to 5900MHz frequency band and the 700MHz to 2700MHz frequency band are as follows: 1) The limiter loss and standing wave are mainly determined by the limiter junction capacitance, zero bias resistance, and parasitic inductance. The junction capacitance changes with the bias voltage, and the change is relatively small. The parasitic inductance is relatively stable. The bias resistance is determined by the I layer resistance, P layer resistance, and N layer resistance, and is relatively fixed under small signal zero bias conditions. The insertion loss simulation results are shown in Figure 1. Figure 2 and Figure 3 As shown in the figure, the simulation results show that the insertion loss of each section is less than 1.6dB. By properly adjusting the matching circuit, the insertion loss within the frequency band can be less than 2dB.

[0023] 2) Input and output standing waves are determined by the lightning protection circuit and the limiter. The standing wave simulation results are as follows: Figure 4 and Figure 5As shown in the figure, limited by the junction capacitance of the device and the matching branch bandwidth, the higher the frequency, the worse the standing wave. The simulation results show that the standing wave in each section is less than 1.7.

[0024] Example 3 The present invention provides a miniaturized lightning protection and limiting device for a specific frequency band. In a lightning protection circuit, an inductor is wound with an enameled wire with a diameter of φ0.3 mm. After winding, the length is about 3 mm and the diameter is about 1.8-2.2 mm (the inductance value can be adjusted according to the length of the enameled wire and the number of winding turns). Considering the high-power pulses that may be received, a chip capacitor with a package of 0805 is selected (a standard package with multiple capacitance options). In a limiting circuit, a conventional PIN diode is usually packaged in a standard package SOD-323 with a single size of 2.7×1.3 mm. The present invention uses four PIN diodes, so a limiting chip is selected. The chip installs a wafer of the PIN diode into the chip by plastic packaging, and the size is 4 mm×4 mm. Therefore, the electronic components involved in the present invention are small in size and small in number, and can be mounted on the printed circuit board in a micro-assembly manner. Therefore, the overall device size can be within 13mm in length, 5.5mm in width, and 3mm in height, occupying very little space, and the weight can also be within 10g. It can be easily reserved at any position between the antenna and the receiver during design. For the situation where the device has already been designed or put into use and there is no modification space, the present invention can even be made inside the cable without changing the original design. Relying on the advantage of small size, it is convenient to install and the position is flexible.

Claims

1. A miniaturized lightning protection and limiting device for a specific frequency band, characterized in that: It includes an inductor and a capacitor connected in parallel, one end of the inductor and the capacitor are both connected to the signal input end, the other end of the inductor is grounded, and the other end of the capacitor is connected in series with two-stage limiters in sequence and then connected to the signal output end, and the two-stage limiters both use PIN diodes.

2. The miniaturized lightning protection and limiting device for a specific frequency band as claimed in claim 1, characterized in that: The inductor and capacitor form a broadband matching circuit for the selection of a specific frequency band. After the target frequency band is selected, the values ​​of the inductor and capacitor to be used are calculated by the following formula: Inductance calculation: Capacitance calculation: In the formula, R is the characteristic impedance of the broadband matching circuit, f is the target frequency of the broadband matching circuit, L is the inductance of the inductor, C is the capacitance value of the capacitor.

3. The miniaturized lightning protection and limiting device for a specific frequency band as claimed in claim 1, characterized in that: The inductor and the capacitor form a lightning protection circuit.

4. The miniaturized lightning protection and limiting device for a specific frequency band as claimed in claim 1, characterized in that: Each of the two-stage limiters includes two PIN diodes connected in parallel and having opposite positive and negative poles, and one end of the two PIN diodes away from the capacitor is grounded.

5. The miniaturized lightning protection and limiting device for a specific frequency band as claimed in claim 1, characterized in that: It is installed on the printed circuit board in a micro-assembly manner. After installation on the printed circuit board, the device size is within 13mm in length, 5.5mm in width and 3mm in height.

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