Patent ID: 7355490
Filing Date: 2008-04-08
Classification: H03J,H04N,Y10S

Abstract:
1. A receiver comprising: a tuning circuit that has a variable capacitive unit and an inductive element, and is capable of being tuned to a frequency of a received signal, the variable capacitive unit having a plurality of capacitive elements and switching units that connect the individual capacitive elements to the inductive element in parallel; a mixer that frequency-converts the received signal; a local oscillator that supplies a local oscillating signal to the mixer; a first PLL circuit that controls the local oscillator to oscillate at a frequency corresponding to the frequency of the received signal; an oscillating active element that constitutes an oscillating circuit together with the tuning circuit; a second PLL circuit that controls the oscillating circuit to output a control voltage for setting a capacitance value of the variable capacitive unit such that an oscillation frequency of the oscillating circuit matches with the frequency of the received signal; an up/down counter that controls turning on/off of the switching units by multiple-bit output data; and a count signal generator that compares the control voltage with a first reference voltage and a second reference voltage lower than the first reference voltage, and outputs an up count signal or a down count signal to the up/down counter, wherein the count signal generator outputs the down count signal when the control voltage is higher than the first reference voltage, outputs the up count signal when the control voltage is lower than the second reference voltage, and stops the output of the up count signal and the down count signal and outputs a lock signal when the control voltage is between the first reference voltage and the second reference voltage, and by the lock signal, a flow of a current in the oscillating active element stops; and wherein the count signal generator further comprises: wherein the tuning circuit is a double-tuning circuit,