Receiving device and gain control method

摘要

A receiving device performs log noise amplification on radio waves (desired waves and interfering waves), received with an antenna, to generate a received signal, converts the received signal into an intermediate frequency signal, converts the intermediate signal into a digital signal, filters out and demodulates a frequency band of a specific channel from the digital signal. Herein, a first received signal strength (RSSI 1) is detected from the digital signal, while a second received signal strength (RSSI 2) is detected from the digital signal of the specific channel. The intermediate frequency signal is amplified with a first gain which is calculated by way of the comparative judgment on the first receive signal strength and the allowable threshold. The digital signal of the specific channel is amplified with a second gain.

主权项

1. A receiving device which receives radio waves intermixing desired waves and interfering waves so as to carry out automatic gain control and demodulation, the receiving device comprising:
a low noise amplifier which amplifies a received wave; an intermediate frequency converter which converts a received signal, output from the low noise amplifier, into an intermediate frequency signal by use of an local oscillator frequency; an analog variable gain function part which amplifies the intermediate frequency signal with a first gain; an analog-to-digital (A/D) converter which performs analog-to-digital conversion on the intermediate frequency signal amplified with the analog variable gain function part; a channel selecting filter which filters out a frequency band of a specific channel from a digital signal output from the A/D converter; a digital variable gain function part which amplifies the digital signal of the specific channel, filtered by the channel selecting filter, with a second gain; a first received signal strength indicator (RSSI) part which detects a first received signal strength from the digital signal output from the A/D converter; a second RSSI part which detects a second received signal strength from the digital signal of the specific channel filtered by the channel selecting filter; a comparison controller which calculates the first gain applied to the analog variable gain function part based on a part of the first received signal strength exceeding an allowable threshold and which calculates the second gain applied to the digital variable gain function part based on the first gain set to the analog variable gain function part when a level difference between the first received signal strength and the second received signal strength exceeds the allowable threshold; and a demodulator which demodulates the digital signal amplified with the digital variable gain function part.