Research Of Auto-tracking Voltage Controlled Filter

The auto-tracking filter is widely used in communication field of echo cancellation, automatic balancing, antenna array beam forming, noise elimination, as well as other related signal processing parameter identification, spectrum estimation, etc. It has important research significance. Based on the full study at various types of automatic tracking filtering method at home and abroad, pointing at the current analog automatic tracking filter's low signal processing speed, low signal bandwidth and the lacking filter frequency automatic tracking and other shortcomings, we design an new kind of analog automatic tracking filter which pass-band can adapted with the frequency range of the input signal of dynamic regulation, applicable to a wide range of signal frequency, high-speed signal processing occasions analog automatic tracking filter.The key research questions are as follows: to study the design theory of all the kinds of high-performance filter, to make full use of junction capacitance of varactor with reverse voltage change and other advantages; to study the design measure and method of the linear circuit; to study the application theory and method of wideband frequency voltage conversion circuit by using decrease frequency and programmable amplifier, to solve the problem of existing F/V chips only can allow low frequency and slow speed signal to be converted, to realize the high frequency automatic tracking filtering.The thesis is summarized and the majority of contents has several aspects:(1) We introduce the current research status of the tracking filter, application field and development prospect, and summarizes and compares existing digital tracking filter algorithm and analog tracking filter design methods; proposes a use of decrease frequency and programmable amplifier and high-performance the F/V chip VFC320 to achieve wideband frequency voltage conversion, combining with varactor and current feedback op amp chip to achieve the design of high frequency and fast analog tracking filter.(2) Principle of varactor adjust frequency and design theory of linear circuit are introduced. Advantages and disadvantages of several linear measures are compared. The method of linear power function circuit that is adopted. The circuit constituted by log amp, multiplier, antilog amp, inverter and proportion arithmetic unit.(3) The signal pre-processing circuit is designed by this thesis, which includes amplification and amplitude circuit. The amplification circuit constituted by resistance and current feedback op amp chip. The amplitude circuit constituted by parallel high frequency switch diode. Part of the circuit are simulated, the same as, the real circuits are experimental measured.(4) The frequency auto-tracking circuit is designed, which includes shaping circuit, wideband frequency to voltage circuit, linear circuit. The shaping circuit constituted by high-speed voltage comparator MAX9203 and resistor networks to achieve shaping signal. The wideband frequency to voltage circuit constituted by decrease frequency circuit and programmable amplifier circuit. The frequency auto-tracking circuit achieves tracking the frequency of input signal. Parts of the circuit are experimental measured.(5) The voltage-controlled filter circuit is designed by using current feedback op amp chip and varactor. And a variety of voltage-controlled filter circuit are analyzed theoretically and simulated by ORCAD Capture software. Parts of the circuit are experimental measured.The analog auto-tracking filter designed in this thesis can achieve the function that the pass band can be adjusted dynamically with the input signal's frequency range and can achieve the automatic tracking function of the filter frequency. The frequency characteristics can be used for harmonic analysis, frequency detection and other areas of the signal detection, has some research significance and application prospects.