| 摘要 |
PROBLEM TO BE SOLVED: To accurately control the amplitude of a received RF signal by changing the reference value of an automatic gain controller, if an interference wave appears near a desired channel on a frequency axis, with a receiving environment determiner provided for determining the radio wave environment of the received RF signal. SOLUTION: The automatic gain control circuit comprises an antenna 1 for receiving RF signals, a tuner 2 for selecting a desired channel, a filter 3 for band-limiting an output signal from the tuner, a variable-gain amplifier 4 for keeping the signal level constant, an AD converter 5 for converting to a digital signal, an orthogonal demodulator 6 for converting to a baseband OFDM signal, a Fourier transformer 7 for transforming to an OFDM signal in a frequency domain, a decoder 8 for decoding the OFDM signal, a receiving environment determiner 9 for determining the radio wave environment of the received signal, and an automatic gain controller 10 for generating a signal for controlling the variable gain amplifier. COPYRIGHT: (C)2004,JPO
|
