Tunable bandpass filter system

Abstract

The invention provides a tunable bandpass filter system, wherein the center frequency range of frequency signals output by the system is 470-862MHz; the system comprises a microprocessor unit, a digital tunable potentiometer and an analog circuit system, wherein the microprocessor unit is used for calculating data signals of frequency points, bandwidth, out-of-band signal rejection and signal gain requirements corresponding to system output requirements according to the received user instruction, and outputting more than one path of instruction signals to the corresponding digital tunable potentiometer unit; the digital tunable potentiometer is used for performing digital to analog conversion according to data bits in the instruction signals, and parallelly outputting four groups of analog voltage signals to the corresponding analog circuit system with the functions of the bandpass filter by taking clock signals as a working period; the analog circuit system with the functions of the bandpass filter is used for exactly intercepting the central frequency points of the input broadband frequency signals under the control of the digital tunable potentiometer according to the received analog voltage signals and then performing bandpass filtering; and a power amplifying part amplifies the signals so as to improve the signal gains to the required level.

Description

A Tunable Bandpass Filter System technical field The invention belongs to the technical field of radio frequency signal processing, and in particular relates to a filter system outputting precise central frequency, bandwidth control, out-of-band signal suppression and adjustable signal gain in the 470-862MHz frequency band. Background technique At present, for the radio frequency digital signal in the range of 470~862MHz in the world, the traditionally defined frequency bands are as follows: For the actual UHF frequency band, 49 frequency points (channels 21 to 69) are specifically defined, and each channel has a corresponding center frequency (for example, channel 21 corresponds to frequency 471.25MHz, channel 37 corresponds to 559.25MHz, channel 69 corresponds to the frequency point 855.25). For radio frequency signals transmitted in space or coaxial cables, qualified bandpass filters must be used to select and reprocess specific channel signals. To realize the sel...

AI Technical Summary

Problems solved by technology

(1) The signal has actually been filtered by two stages of high-pass and low-pass. Since the actual transmission is a radio frequency signal, the signal loss and loss of the transmission is relatively large

At the same time, there is more noise introduced into the signal during transmission;

(2) It is difficult to ensure the accurate output of the bias voltage of the varactor, and then the capacitance of the varactor is changed by the bias voltage, and the accuracy of the upper and lower side frequencies of the adjusted bandpass filter is difficult to guarantee;

(4) When there are many frequency points required to be output, it is impossible to control the bias voltage of the varactor in real time to meet the output requirement;

(5) For weaker signals, there is no option to provide real-time signal gain function

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