1977-11-14
1978-09-19
Griffin, Robert L.
325388, 325437, 325344, H04B 106
Patent
active
041157370
ABSTRACT:
A tuner for receiving signals broadcast on two spaced bands, each divided into several channels, has two fixed bandpass filters, one to pass all of the channels in the lower band between the lowest frequency f.sub.P of the lowest channel and the highest frequency f.sub.S of the highest channel of the lower band, and the other to pass all of the channels in the upper frequency band between the lowest frequency f.sub.T of the lowest channel and the highest frequency f.sub.W in the highest channel of the upper band. The bandwidth of each channel is f.sub.B. The tuner includes an amplifier and a third filter to which signals of either band are supplied by selective operation of a switch. The third filter has a cut-off frequency below the second harmonic of the lowest frequency of the upper band to simplify the avoidance of image interference from second harmonic signals of the band. A tunable local oscillator supplies a heterodyning signal to the mixer to convert any selected channel of the received signal to an intermediate frequency (i.f.) band, and image interference is avoided by setting the local oscillator frequency f.sub.n required to convert channel n to the i.f. at a frequency above that channel such that the lowest frequency f.sub.L of the i.f. band satisfies the following conditions: ##EQU1##
REFERENCES:
patent: 3639840 (1972-02-01), Shekel
patent: 3931578 (1976-01-01), Gittinger
patent: 3942120 (1976-03-01), Ham
patent: 4009441 (1977-02-01), Kumagai et al.
patent: 4045740 (1977-08-01), Baker
Hongu Masayuki
Kawakami Hiromi
Niimura Tsutomu
Eslinger Lewis H.
Griffin Robert L.
Ng Jin F.
Sinderbrand Alvin
Sony Corporation
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