Low noise CATV converter

Telecommunications – Wireless distribution system

Patent

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Details

455241, 455249, 455315, 455131, H04B 126, H04H 102

Patent

active

045205078

ABSTRACT:
A low noise frequency converter particularly adapted for the large bandwidth environment encountered in extended bandwidth cable television (CATV) systems is disclosed. The CATV converter includes an upconverter/downconverter combination for translating the received RF signal to an intermediate frequency (IF) carrier signal. A first IF signal is generated by heterodyning the received RF signal with the output of a voltage controlled oscillator in a first double balanced mixer. The upconverted signal thus produced is then mixed in a second double balanced mixer with the reference output of a second local oscillator to provide a fixed, downconverted second IF carrier signal. The upconverter portion of the CATV converter includes a pin diode attenuator between an RF amplifier and the first double balanced mixer. The pin diode attenuator is driven by the RF amplifier and is regulated by the signal receiver's automatic gain control (AGC) system permitting signal level to be increased at a faster rate than noise figure resulting in an improved converter signal-to-noise ratio and improved large signal handling capability. The downconverter portion of the CATV converter includes a double balanced diode mixer between the first IF amplifier and the second IF amplifier. With the double balanced diode mixer for the second mixer in the downconverter section, cross-modulation and intermodulation distortion from adjacent channels is reduced. In addition, the double balanced diode mixer provides an improved overall noise figure due to its lower noise performance than that available with either a single ended diode mixer or active mixer.

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