Electrically tunable filter for gain of VHF/UHF frequency band and communication device of electrically tunable filter

Abstract

The invention discloses an electrically tunable filter for gain of a VHF / UHF frequency band. The electrically tunable filter comprises a first tuning loop unit, a second tuning loop unit, a third tuning loop unit, and a low-noise amplifier, wherein the first tuning loop unit is used for acquiring a radio-frequency signal, and carrying out frequency pre-selection on the radio-frequency signal so as to obtain a radio-frequency signal with a pre-selected frequency, sending the radio-frequency signal with the pre-selection frequency to the low-noise amplifier for low-noise amplification so as to obtain low-noise amplified radio-frequency signal with the pre-selection frequency and sending the low-noise amplified radio-frequency signal with the pre-selection frequency to a dual-tuning network consisting of the second tuning loop unit and the third tuning loop unit for secondary frequency selection, so as to obtain the gain controllable low-noise amplified radio-frequency signal, wherein the frequencies respectively contained in the radio-frequency signal and the gain controllable low-noise amplified radio-frequency signal belong to the VHF / UHF frequency band.

Description

technical field [0001] The present invention belongs to the technical field of very high frequency (VHF) / ultra high frequency (Ultra High Frequency, VHF) / communication frequency band communication equipment, and in particular relates to a VHF / UHF frequency band gain electronically adjustable filter and a communication device thereof , suitable for band-pass ESC filtering in the VHF / UHF frequency band at the front end of the receiving equipment. Background technique [0002] VHF (Very high frequency, VHF) refers to radio waves with a frequency band from 30MHz to 300MHz; VHF is mostly used for radio and television broadcasts, and is also a communication channel for aviation and navigation, mainly for short-distance transmission; and The difference with high frequency (HF) is that the ionosphere of VHF usually does not reflect the VHF signal, and VHF is often affected by environmental factors (such as: terrain) to affect its signal. [0003] Ultra High Frequency (UHF) refers t...

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Problems solved by technology

[0004] With the continuous development of communication technology, the communication frequency resources in the VHF / UHF frequency band are very tight, and the environmental noise is complex. In the same area or on the same vehicle, there will be situations where adjacent channels communicate at the same time, causing channel interference between communication devices. The channel hardware of these communication devices is designed with good selectivity and frequency-variable frequency-selective electronic filter frequency selection devices; The bias voltage controls the gating frequency of the band-pass filter to realize the function of gating the useful signal in the receiving channel and attenuating the useless signal outside the band; The receiving signal is amplified, but due to the large insertion loss of the electric tuning filter, the receiving noise figure will be too large, which will affect the sensitivity of the communication equipment; if the low noise amplifier (LNA) is placed before the electric tuning filter, there will be no frequency selection for the receiving signal , even if there is a low-insertion-loss band-pass filter built by a combination of inductors and capacitors at the front end to process unwanted out-of-band signals, it is difficult to deal with the problem of channel saturation due to strong interference from adjacent channels, which in turn affects the receiving device in communication equipment

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