Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1991-10-28
1994-09-20
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
4551922, 4551972, 455272, H04B 116
Patent
active
053497007
ABSTRACT:
A tunable antenna system operates over a predetermined frequency range with an antenna having a length and width each significantly less than a quarter wavelength within the predetermined frequency range. A controllable reactive element is coupled to the antenna and has a variable reactance for tuning the antenna in a resonant circuit to the frequency of a desired signal in the predetermined frequency range. An antenna-tuning circuit is responsive to the frequency to which the antenna is tuned for providing an antenna-tuning signal to the controllable reactive element to control the reactance of the controllable reactive element so that the antenna remains tuned to the desired signal. The antenna tuning signal includes a dither component of dither frequency for varying the tuning of the antenna around the desired signal. The antenna tuning circuit includes a level detector for providing a level signal representative of a signal transduced by the antenna. The level signal includes a second harmonic component of frequency twice the dither frequency. A second harmonic detector responds to the second harmonic component to provide a dither amplitude control signal that reduces the amplitude of the dither signal with increasing amplitude of the second harmonic component.
REFERENCES:
patent: 3473128 (1969-10-01), Kiser
patent: 3869674 (1975-03-01), Borbely
patent: 4100578 (1978-07-01), Arneson
patent: 4843636 (1989-06-01), Hendriks et al.
patent: 4996599 (1991-02-01), Anderson
patent: 5077834 (1991-12-01), Andros et al.
Bose Corporation
Eisenzopf Reinhard J.
Pham Chi
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