High-Q-factor band-pass filter for audio near field communication

Abstract

The invention discloses a high-Q-factor band-pass filter for audio near field communication. The band-pass filter comprises a first amplifier, a second amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor, a second capacitor and a third capacitor, wherein the first amplifier, the first, second and third resistors and the first and second capacitors jointly form a first-stage general filter low in Q-value, the second amplifier, the sixth and seventh resistors and the third capacitor jointly form a second-stage phase inverter which amplifies signals by several times to increase the Q-value of an entire circuit, and the fifth resistor is a feedback resistance which leads part of positive feedback of the second stage into the first stage. The band-pass filter has good frequency-selection characteristics. The Q-value of the circuit is increased, so that the band-pass filter is narrow in bandwidth and good in frequency-selection characteristics and has good anti-jamming capability.

Description

technical field [0001] The invention relates to a band-pass filter, in particular to a high-Q band-pass filter for audio near-field payment. Background technique [0002] The audio near-field payment technology is proposed by the applicant and applied for a patent, which uses short-distance audio transmission information to complete the payment function. It uses the audio transceiver device that comes with conventional equipment such as mobile phones to realize payment, and has the advantages of fast payment and easy implementation. , Easy to popularize the advantages. In the audio near-field payment technology, band-pass filters are required in the process of audio receiving and sending. Although the traditional band-pass filters have the advantages of no inductor, small size, light weight, open-loop voltage gain and integrated op amp The input impedance is very high, and the output impedance is low. After forming an active filter circuit, it also has the advantages of vol...

AI Technical Summary

Problems solved by technology

In the audio near-field payment technology, band-pass filters are required in the process of audio receiving and sending. Although the traditional band-pass filters have the advantages of no inductor, small size, light weight, open-loop voltage gain and integrated op amp The input impedance is very high, and the output impedance is low. After forming an active filter circuit, it also has the advantages of voltage amplification and buffering, but because of its Q value (that is, the quality factor), it cannot be made very large, which leads to its pass-through The frequency bandwidth cannot be made very narrow, resulting in the filter's poor selectivity to frequency, and the ability to suppress interference signals is not very strong.

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