Channel selector

DETAILED DESCRIPTION What is claimed is: 1.
A channel selector comprising: a phase locked loop (PLL) frequency synthesizer which synthesizes a local oscillation frequency corresponding to a closely determined frequency to a transmitting signal of a desired receiving channel; a search tuning system; means for adding an output of a voltage integrator of said search tuning system which is in sweeping state to an output of a low pass filter of said PLL; means for causing said PLL to be an open loop, when an added voltage obtained by said means reaches a voltage corresponding to said closely determined frequency; and means thereafter for searching said transmitting signal by said search tuning system for causing said search tuning system to be in search tuning state.
2.
A channel selector according to claim 1, wherein a sweep driving voltage of said search tuning system is variable so as to enable fine adjustment of a local oscillation frequency of said search tuning system.
3.
A channel selector according to claim 1 further comprising means for controlling a dividing ratio of a programmable divider of said PLL frequency synthesizer, so that said PLL frequency synthesizer will synthesize said closely determined frequency again, when a local oscillation frequency reaches a closely determined frequency across a frequency of said transmitting signal in the opposite side of said closely determined frequency after breaking said transmitting signal.
4.
A channel selector according to claim 1 further comprising: means for detecting a detector output when there is not said transmitting signal of a desired receiving channel; and means for controlling a dividing ratio of said a programmable divider of said PLL frequency synthesizer so as to cause a channel selection number to increase by one for PLL frequency synthesizer to synthesize a closely determined frequency to a transmitting signal of the channel of said channel selection number.
5.
A channel selector according to claim 1, wherein said transmitting signal of a desired receiving channel is a video carrier of television broadcast, and the channel selector further comprises means for deciding a local oscillation frequency corresponding to the closely determined frequency of said video carrier to be in the opposite side of a local oscillation frequency corresponding to an adjacent sound carrier frequency across a local oscillation frequency corresponding to said video carrier frequency