| 摘要 |
PURPOSE:To constitute a front end of a 2-band receiver with simple constitution by providing a single local oscillator using a fundamental wave and its harmonics so as to plural band frequencies into a single IF. CONSTITUTION:An oscillator 31 is connected to an oscillation tuning circuit 30 and its oscillation output is fed to a mixer 12 via a mixer 5 and a 2nd harmonic extraction circuit 32. In selecting the IF of a lower local system superheterodyne receiver to, e.g., 10.7MHz, it is required for local oscillators of 65.3-79.3MHz, 79.3-97.3MHz and 164.3-212.3MHz. When the local oscillator 31 oscillates frequencies of 65.3-106.15MHz, since the secondary harmonic is in the range of 130.6-212.3MHz, the lower local system superheterodyne receiver has all the required local oscillating frequencies to receive an FM and TVVHF signal in utilizing the harmonics. Thus, two bands are received selectively by a single local oscillator.
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