Harmonic absorbing circuit for short wave filter

Abstract

The utility model discloses a kind of harmonic absorption circuits of short wave filter, circuit includes RF power amplifier, low-pass filter module and high-pass filter module, the high-pass filter module is connected in parallel at the input end of the low-pass filter module, and the input end of low-pass filter module and high-pass filter module is respectively connected in parallel by the RF power amplifier output signal. The scheme adopts the mode of connecting high-pass filter in parallel at the input end of low-pass filter, and the passband of high-pass filter is set as the out-of-band harmonic suppression frequency band of wave band, 50Ω power resistance is connected at the output end of high-pass filter to absorb harmonic power, improve the harmonic suppression performance of short wave communication equipment and improve the working life of power amplifier tube.

Description

Technical Field

[0001] This utility model relates to the field of shortwave communication technology, and in particular to a harmonic absorption circuit for a shortwave filter. Background Technology

[0002] In shortwave communication equipment, power amplifier devices, due to their nonlinear operation, generate harmonic parasitic parameters, which can cause interference at non-operating frequencies. Therefore, certain requirements are placed on harmonic performance specifications. Shortwave communication equipment operates in the 1.6-30MHz range, with operating frequencies approaching twenty harmonics. Filter components must be divided into at least seven bands to effectively filter out multiple harmonics. Due to the wide operating bandwidth, the large number of bands required, and the limitations of equipment size, conventional shortwave filter components typically employ a 7th-order low-pass filter to remove harmonics.

[0003] To meet the insertion loss requirements within the operating frequency band, the out-of-band rejection of such low-pass filters is typically only around 45dB, resulting in a harmonic performance limit of only around 55dB for the equipment. Due to the wide operating frequency band, the multiple harmonics generated by the nonlinearity of the shortwave power amplifier account for a very high percentage of the total output power, approximately 15-20%. These multiple harmonics, under the out-of-band rejection of the low-pass filter, will be reflected back to the power amplifier tubes. Over long-term operation, this will lead to a degradation in the performance and a reduction in the lifespan of the power amplifier tubes. Utility Model Content

[0004] To address the aforementioned technical problems, this utility model provides a harmonic absorption circuit for a shortwave filter.

[0005] This utility model is achieved by the following technical solution: a harmonic absorption circuit for a shortwave filter, comprising an RF power amplifier, a low-pass filter module, and a high-pass filter module, wherein the input terminal of the low-pass filter module is connected in parallel with the high-pass filter module, and the output signal of the RF power amplifier is connected in parallel with the input terminals of the low-pass filter module and the high-pass filter module respectively.

[0006] Specifically, the passband of the high-pass filter module is set to the out-of-band harmonic suppression frequency band of the band, and the output terminal of the high-pass filter module is connected to a power resistor that absorbs harmonic power.

[0007] Specifically, the power resistor has a resistance of 50Ω.

[0008] Specifically, the high-pass filter module includes four capacitors connected in parallel, with the other end of each capacitor grounded. An inductor is connected in series between adjacent capacitors in the high-pass filter module circuit, and a capacitor is also connected in parallel across each inductor.

[0009] Specifically, the output of the low-pass filter module is connected to an external antenna.

[0010] Specifically, an inductor is connected in parallel between the output of the low-pass filter module and the external antenna connection line, and the other end of the inductor is grounded.

[0011] Specifically, the low-pass filter module includes three capacitors connected in series on the line, an inductor connected in parallel between adjacent capacitors, and each inductor connected in series with a capacitor and then grounded.

[0012] The beneficial effects of this utility model are as follows: This utility model adopts the method of connecting a high-pass filter in parallel at the input end of the low-pass filter, setting the passband of the high-pass filter as the out-of-band harmonic suppression frequency band of the band, and connecting a 50Ω power resistor at the output end of the high-pass filter to absorb harmonic power, thereby improving the harmonic suppression performance of shortwave communication equipment and increasing the working life of the power amplifier tube. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the harmonic absorption circuit module of the shortwave filter in this embodiment of the present invention; Figure 2 This is a structural diagram of the harmonic absorption circuit of the shortwave filter in this embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0017] The following is in conjunction with the appendix Figure 1-2 The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0018] This invention proposes a harmonic absorption circuit for a shortwave filter, such as... Figure 1As shown, it includes an RF power amplifier, a low-pass filter module, and a high-pass filter module. The input terminal of the low-pass filter module is connected in parallel with the high-pass filter module, and the output signal of the RF power amplifier is connected in parallel with the input terminals of the low-pass filter module and the high-pass filter module, respectively.

[0019] In this embodiment, the passband of the high-pass filter module is set to the out-of-band harmonic suppression frequency band of the band, and the output terminal of the high-pass filter module is connected to a power resistor that absorbs harmonic power with a resistance value of 50Ω; the output terminal of the low-pass filter module is connected to an external antenna.

[0020] The operating logic of the harmonic absorption circuit of the shortwave filter proposed in this invention is as follows: the output signal of the RF power amplifier is connected in parallel to the input terminals of the low-pass filter and the high-pass filter respectively. The bandpass of the low-pass filter is set within the main wave range of the operating frequency of the RF power amplifier, and the stopband is set at the harmonic frequency of the operating frequency. In this way, the harmonic signal is blocked by the low-pass filter, and only the main wave signal is output to the antenna terminal. The bandpass of the high-pass filter is set at the harmonic of the operating frequency of the RF power amplifier, and the stopband is set within the main wave range of the operating frequency of the RF power amplifier. In this way, only the harmonic signal is absorbed to the 50Ω load at the output terminal by the high-pass filter, thus avoiding the reflection of harmonic power back to the power amplifier tube and improving the harmonic suppression capability.

[0021] In one specific embodiment, the harmonic absorption circuit structure of the shortwave filter is as follows: Figure 2 As shown, the high-pass filter module includes four capacitors connected in parallel (C1, C3, C4, C7), with the other end of the capacitors grounded. An inductor (L1, L2, L3) is connected in series between adjacent capacitors in the high-pass filter module circuit, and a capacitor (C2, C4) is also connected in parallel across each inductor.

[0022] An inductor (L6) is connected in parallel between the output of the low-pass filter module and the external antenna connection line, and the other end of the inductor (L6) is grounded; the low-pass filter module includes three capacitors (C8, C10, C12) connected in series on the line, an inductor (L4, L5) is connected in parallel between adjacent capacitors, and each inductor is connected in series with a capacitor (C9, C11) and then grounded.

[0023] The technical specifications of the harmonic absorption circuit of the shortwave filter proposed in this utility model include: 1) Frequency range: 2.0000MHz~29.9999MHz; 2) Input VSWR: ≤1.3 (load VSWR ≤1.1); 3) Operating voltage: 21V~30.8V; 4) Input level: ≤2dBm; 5) Output power: 50dBm+1dB; (100W continuous wave and peak packet power, load VSWR ≤2, the power amplifier power output performance does not deteriorate), while meeting the overall system performance requirements; 6) Power gain: ≥48dB; 7) Gain flatness: ±1dB; 8) Relative audio intermodulation product level: Under test conditions of a 600Hz two-tone interval and an output peak power of 100W (filter output port), the following must be met: a) ≤-32dB (supply voltage 21V~25.2V); b) ≤-36dB (supply voltage 25.2~30.8V); 9) Working efficiency: ≥40% (within the working voltage range), while also meeting the overall machine specifications; 10) Harmonic distortion: ≤-55dB; 11) Transmit / receive isolation: ≤-65dB.

[0024] This solution uses a high-pass filter connected in parallel at the input of a low-pass filter. The passband of the high-pass filter is set to the out-of-band harmonic suppression band of the band. A 50Ω power resistor is connected at the output of the high-pass filter to absorb harmonic power.

[0025] For the foregoing embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to this application.

[0026] The above embodiments describe the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Modifications and variations made by those skilled in the art without departing from the spirit and scope of this utility model should be protected within the scope of the appended claims.

Claims

1. A harmonic absorption circuit for a shortwave filter, characterized in that, It includes an RF power amplifier, a low-pass filter module, and a high-pass filter module. The input terminal of the low-pass filter module is connected in parallel with the high-pass filter module, and the output signal of the RF power amplifier is connected in parallel with the input terminals of the low-pass filter module and the high-pass filter module, respectively.

2. The harmonic absorption circuit of a shortwave filter as described in claim 1, characterized in that, The passband of the high-pass filter module is set to the out-of-band harmonic suppression frequency band of the band, and the output terminal of the high-pass filter module is connected to a power resistor that absorbs harmonic power.

3. The harmonic absorption circuit of a shortwave filter as described in claim 2, characterized in that, The power resistor has a resistance of 50Ω.

4. The harmonic absorption circuit of a shortwave filter as described in claim 2, characterized in that, The high-pass filter module includes four capacitors connected in parallel, with the other end of each capacitor grounded. An inductor is connected in series between adjacent capacitors in the high-pass filter module circuit, and a capacitor is also connected in parallel across each inductor.

5. The harmonic absorption circuit of a shortwave filter as described in claim 1, characterized in that, The output of the low-pass filter module is connected to an external antenna.

6. The harmonic absorption circuit of a shortwave filter as described in claim 5, characterized in that, An inductor is connected in parallel between the output of the low-pass filter module and the external antenna connection line, with the other end of the inductor grounded.

7. The harmonic absorption circuit of a shortwave filter as described in claim 5, characterized in that, The low-pass filter module includes three capacitors connected in series on the line, an inductor connected in parallel between adjacent capacitors, and each inductor connected in series with a capacitor and then grounded.

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