1 results about "Local oscillator" patented technology

The invention relates to a digital tuner solving the problem that the power levels of television signals are lowered because of a great number of combined two-order and three-order beat interference signals generated by dense channel signals of the prior high-level cable digital televisions. The digital tuner comprises an antenna input device, a radio-frequency AGC low-noise wideband pre-amplifier, a power divider, a frequency selective network, a tracking filter, a frequency mixer, a local oscillator, an intermediate-frequency filter, a circular signal output device, a rheostatic diode, an alternating current gain controller and a delay controller, wherein the alternating current gain controller is connected in series with the frequency selective network and the tracking filter and also connected in parallel with the delay controller and a high-frequency AGC voltage. The invention adopts a step-by-step AGC control mode to control intermediate-frequency AGC, high-level AGC and radio-frequency AGC step by step so that the functions that a small signal receives a low noise factor and a large signal has a large receiving dynamic range is achieved, and the acceptable maximum cable television signal level can not be lowered.