Automatic gain control circuit for zero intermediate frequency receiver

Abstract

The invention relates to an automatic gain control circuit for a zero intermediate frequency receiver. The automatic gain control circuit comprises at least one radio frequency variable gain amplifier, at least one phase splitter, a second circuit and a first circuit, wherein the radio frequency variable gain amplifier is used for inputting a radio-frequency signal and dividing the radio-frequency signal into an orthogonal signal and a homonymous signal; the phase splitter is used for inputting a local oscillation signal; the second circuit is used for processing the orthogonal signal; the first circuit is used for processing the homonymous signal; the second circuit and the first circuit are parallel; each circuit comprises a mixer, a baseband variable gain amplifier, an LC low pass filter and a baseband fixed gain amplifier for outputting a baseband signal, which are connected in series sequentially; the radio frequency variable gain amplifier is simultaneously connected with the mixers of the two circuits respectively; and the phase splitter is simultaneously connected with the mixers of the two circuits respectively. The automatic gain control circuit overcomes the disadvantage that the conventional automatic gain control circuit has lower performance when the receiver has high sensitivity requirement on the circuits.

Description

Technical field [0001] The invention belongs to the technical field of wireless radio frequency transceiver systems, and particularly relates to an automatic gain control circuit of a zero-IF receiver. Background technique [0002] In the wireless radio frequency transceiver system, due to the influence of factors such as the different signal power transmitted by the transmitter, the different path loss during the signal propagation, the change of the distance between the transmitter and the receiver, the change of the receiver environment, and the interference of other frequency band signals, Makes the signal strength acting on the input of the receiver have great changes and fluctuations. However, the terminal equipment of the receiver can generally only process signals with little amplitude change. If the signal is too strong or weak, or the terminal equipment becomes invalid. The amplitude of the output signal of the receiver depends on the signal strength acting on the inpu...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide an automatic gain control circuit for a zero-IF receiver in order to overcome the disadvantage that the existing automatic gain control circuit is not effective when the receiver requires high sensitivity

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