| 摘要 |
A received modulated information signal is converted to an intermediate frequency (IF) signal from which modulating information may be recovered by supplying the modulated information signal to two mixers supplied with local oscillating signals of equal frequency but phase shifted with respect to each other. Output signals produced by the mixers are supplied through phase shift circuits which impart predetermined phase shifts thereto such that image signal components present in respective ones of the mixer output signals are phase shifted to be out-of-phase with each other. The phase shifted mixer output signals are combined, whereby the out-of-phase image signal components are substantially cancelled. A filter tuned to the IF frequency is coupled to the output of the combining circuit to pass the mixer output signals having frequencies within a predetermined range of the IF frequency.
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