Common receiver for terrestrial TV and CATV

Abstract

The present invention relates to a common receiver for terrestrial TV and CATV. A tuner section 1 includes: an RF signal input terminal 2 via which multichannel RF signals are supplied; an AGC circuit 4, by which the RF signal input terminal 2 is followed, for fixing or controlling a gain in accordance with a first gain control signal; a broadband amplifying circuit 5, by which the AGC circuit 4 is followed; an AGC circuit 6, by which the broadband amplifying circuit 5 is followed, for fixing or controlling a gain in accordance with a second gain control signal,; a mixer circuit 7 for selecting and picking out a target channel signal from signals supplied from the AGC circuit 6; and an AGC switching circuit 15 for controlling gains of the AGC circuit 4 and the AGC circuit 6 by selecting whether to fix or to control a gain of the AGC circuit 4 while selecting whether to fix or to control a gain of the AGC circuit 6.

Description

technical field [0001] The invention relates to a ground wave TV / CATV compatible receiver. Background technique [0002] Currently, with the digitalization of broadcasting, there is an increasing need to be able to receive various broadcasting signals such as terrestrial TV broadcasting and CA (cable) TV broadcasting with one receiver. [0003] Due to the difference in transmission media such as air transmission and cable transmission, as well as the difference in transmission conditions such as the number of channels and signal strength caused by different broadcast methods, the performance required for the receivers to receive the above broadcast signals are also different. . [0004] For example, in CATV broadcasting, multi-channel broadcasting signals of 134 channels in the RF signal transmission frequency band are transmitted with approximately equal signal strengths of -64dBm to -34dBm, and the signal range is 30dB. Among them, the above-mentioned RF signal transmiss...

AI Technical Summary

Problems solved by technology

Therefore, when receiving CATV broadcasts that require good distortion characteristics, there will be a problem that the amplified RF signal is not sufficiently attenuated by the AGC circuit 116 preceding the RF signal amplifying circuit 117 due to insufficient attenuation of the signal. signal distortion problem

[0027] In addition, when receiving terrestrial TV broadcasting, when the input signal level is low, the AGC circuit 116 preceding the RF signal amplifying circuit 117 will also operate, and the total noise figure NF total of the tuner 115 will increase. , there will be a problem that the reception performance of the tuner deteriorates

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