RADIO FREQUENCY HIGH-Q VALUE BAND-PASS FILTER

摘要

A radio frequency high-Q value band-pass filter is a feed-forward structure and comprises a main branch circuit, a feed-forward branch circuit and a subtraction circuit. The main branch circuit and the feed-forward branch circuit are the same in structure, and comprise a radio frequency amplification stage and a load stage. The load stage is composed of a switch mixing stage of a passive mixer and a trans-impedance stage. The input impedance feature of a trans-impedance amplifier is moved to a radio frequency local oscillator by means of the impedance moving feature of the passive mixer on a frequency, so as to enable a main branch to become a radio frequency high-Q value band elimination filter. In order to ensure the phase matching between output ends of a feed-forward branch and the main branch, the feed-forward branch uses a structure same as that of the main branch, and an in-band rejection ratio and a stop bandwidth of the band elimination filter of the branch are reduced by changing a feedback resistance value of the trans-impedance stage in the feed-forward branch. Then, the radio-frequency band pass effect is realized by subtracting an output signal of the main branch from an output signal of the feed-forward branch by using the subtraction circuit.