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    • 9. 发明专利
    • CARRIER CONVERTING EQUIPMENT
    • GB1448883A
    • 1976-09-08
    • GB5490373
    • 1973-11-27
    • JAPAN BROADCASTING CORP
    • H04N7/01H03C1/50H03D7/00H03D7/02H03D7/04H03D7/18H03D9/06H04N7/00H04N7/20
    • 1448883 Modulators; frequency changing NIPPON HOSO KYOKAI 27 Nov 1973 [30 Nov 1972 18 April 1973] 54903/73 Headings H3R and H3T In an arrangement for amplitude modulating a second unmodulated carrier wave with a signal which is received as an amplitude modulated first carrier wave, the two carrier waves are applied to a two-terminal non-linear device, and an amplitude modulated second carrier wave extracted. In one embodiment a frequencymodulated U.H.F. wave is first converted to an amplitude-modulated U.H.F. wave by means of circuit Q, Fig. 2a, which may comprise an off-tune parallel resonant circuit (Fig. 4a, not shown). The amplitude modulated U.H.F. signal is applied via circuit FU1 resonant at this frequency to terminal 6 of diode d which may comprise a tunnel, variable capacitance or other diode. Unmodulated V.H.F. carrier is applied to terminal 5 of diode d over seriesresonant circuit FV1: the diode d is biased by means of circuit V, and amplitude-modulated V.H.F. signal obtained at terminal 2. Circuit FV2 is resonant at the V.H.F. carrier frequency. In a second embodiment, amplitude-modulated signal is applied via terminal 4, Fig. 10, and unmodulated V.H.F. carrier via terminal 1, to diode d. Amplitude-modulated V.H.F. signal is obtained at terminal 2, across circuit F V resonant at this frequency: series-resonant shunt circuits Fm and Fi are tuned respectively to the sum and difference frequencies. The Specification also describes a modification of this circuit using a 3-dB coupler (Fig. 12, not shown) and one using a circulator (Fig. 13, not shown). The circuit may also impose preemphasis or de-emphasis.