Patent ID: 8213892
Filing Date: 2012-07-03
Classification: H03D,H04B

Abstract:
1. An FM-AM demodulator comprising: an FM signal amplifier configured to amplify an input FM signal; a local oscillator configured to generate a local oscillation signal for converting the FM signal to an intermediate frequency signal; an image oscillator configured to generate an image signal in FM frequency band; a first selector configured to select one of a signal from the FM signal amplifier and a signal from the image oscillator to output; a first orthogonal mixer configured to generate and output an I signal and a Q signal by performing frequency conversion using the local oscillation signal generated by the local oscillator and the signal selected by the first selector; an AM signal amplifier configured to amplify an input AM signal; a first frequency divider configured to generate a local oscillation signal for converting the AM signal to an intermediate frequency signal by performing frequency division on the output signal from the image oscillator; a second frequency divider configured to perform frequency division on the output signal from the local oscillator; a second selector configured to select one of a signal from the AM signal amplifier and a signal a signal from the second frequency divider to output; a second orthogonal mixer configured to generate and output I signal and Q signal by performing frequency conversion using the signal selected by the second selector and a signal from the first orthogonal mixer; a third selector configured to select one of the I signal from the first orthogonal mixer and the I signal from the second orthogonal mixer to output; a first filter configured to remove a high frequency signal component from the I signal selected by the third selector and output it; a first amplifier configured to amplify the I signal output from the first filter; a fourth selector configured to select one of the Q signal from the first orthogonal mixer and the Q signal from the second orthogonal mixer to output; a second filter configured to remove a high frequency signal component from the Q signal selected by the fourth selector to output it; a second amplifier configured to amplify the Q signal output from the second filter; a first gain controller configured to receive the I signal the first amplifier outputs and the Q signal the second amplifier outputs, and control the first and the second amplifiers so that the input I signal and the input Q signal have predetermined amplitudes; an I/Q compensation unit configured to perform a compensation operation on the gain and the phase of the I signal from the first amplifier or the Q signal from the second amplifier or both of the I and Q signals and output; an IF oscillator configured to generate and output a signal having a predetermined frequency when the intermediate frequency signal for the FM received signal or AM received signal is demodulated; a third orthogonal mixer configured to generate and output an I signal and a Q signal by performing frequency conversion using the I and Q signals output from the I/Q compensation unit with a signal output from the IF oscillator; an adder configured to add the converted I and Q signals output from the third orthogonal mixer to output; a channel filter configured to extract a signal with a predetermined frequency band from the signal output from the adder; a third amplifier configured to amplify the signal output from the channel filter to output; a second gain controller configured to control the third amplifier to output a signal having a predetermined amplitude; a demodulator configured to generate and output an output signal by demodulating the output signal from the third amplifier; and an I/Q compensation controller configured to generate an I/Q compensation signal to be used for adjusting phase and gain of the I signal in the I/Q compensation unit by detecting the amplitude of the output signal from the demodulator, and output the generated signal to the I/Q compensation unit.