Telecommunications – Transmitter and receiver at separate stations – Frequency or phase modulation
Patent
1988-10-13
1991-06-11
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
Frequency or phase modulation
455307, 455339, H04B 110
Patent
active
050239333
ABSTRACT:
An SCA receiver is provided which has a close to ideal passband characteristic which greatly improves frequency response to produce a brighter sound due to the use of ceramic resonator elements. The use of ceramic resonator elements and a superheterodyne approach also provides a receiver which can be rapidly aligned and which has improved noise protection, lower distortion, increased stability, less residual subcarrier in the audio, and more consistent performance from one unit to the next. In one embodiment the superheterodynes circuit operates at 455 kHz which up-converts the usual 67 kHz signal by mixing it with the output of a ceramic resonator controlled local oscillator/mixer. The ceramic resonator and ceramic filter along with the local oscillator/mixer I.C. provides low group delay, improved impulse noise rejection, while most importantly achieving at least an order of magnitude better audio response over the signal bandwidth. Moreover, in the manufacturing process, complicated alignment is eliminated which decreases the alignment time from as much as two hours to typically under two minutes.
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Eisenzopf Reinhard J.
Tendler Robert K.
Urban Edward
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