Patent ID: 9166642
Filing Date: 2015-10-20
Classification: H03J,H04B

Abstract:
1. A frequency signal receiving device comprising: a mixer generating an intermediate frequency which has a predetermined center frequency by mixing a received frequency signal with a local oscillation frequency signal generated by a local oscillator, and outputting the intermediate frequency signal; an IF filter comprising a high-pass filter and a low-pass filter connected in series to each other each of which includes a resistance and condenser block that is connected to the resistance and a capacity thereof is changeable comprising a plurality of condensers connected in parallel to each other via at least one corresponding switch respectively, and receiving said intermediate frequency signal, and causing a frequency signal to pass therethrough, the passed frequency signal existing within a range of a frequency band determined by a center frequency and a size of a frequency bandwidth set in the IF filter; a controlling part providing the high-pass filter and the low-pass filter with a filter adjusting input signal, which part changes the size of the frequency bandwidth set in the IF filter by changing a capacity value of the condenser block by turning said switch on or off according to frequency components contained in the passed frequency signal, and providing the local oscillator with an oscillating frequency setting input signal, which changes the local oscillation frequency signal so as to match a center frequency of said intermediate frequency signal with the center frequency set in the IF filter that fluctuates with the change of the size of the frequency bandwidth set in the IF filter, wherein the local oscillator is a Phase Locked LOOP oscillator; the center frequency and the size of the frequency bandwidth of the IF filter are set by a resistance element having a changeable resistance value or a capacity element having a changeable capacitance value: the controlling part comprises: a first storing part in which a plurality of frequency bandwidth setting data pieces each consisting of digital data for setting the size of the frequency bandwidth of the IF filter by changing one of the resistance values of the resistance element and the capacitance value of the capacity element are stored for a plurality of mutually different sizes of the frequency bandwidth, respectively; a first selecting circuit for selecting one of the frequency bandwidth setting data pieces and outputting the selected data piece to the IF filter; a second storing part in which a plurality of local oscillation frequency signal setting data pieces each indicating a division ratio for setting the frequency of the local oscillation frequency signal to the local oscillator are stored correspondingly to a plurality of mutually different frequencies of the local oscillation frequency signal; and a second selecting circuit for selecting one of the local oscillation frequency signal setting data pieces and outputting the selected data piece to the oscillator, and the controlling part outputs, in accordance with a setting signal inputted from an outside of the frequency signal receiving device, the filter adjusting input signal to the IF filter by issuing a first selection command for selecting one of the frequency bandwidth setting data pieces to the first selecting circuit, and the oscillation frequency setting input signal to the local oscillator by issuing a second selection command for selecting one of the local oscillation frequency signal setting data pieces to the second selecting circuit, the plurality of local oscillation signal setting data pieces stored in the second storing part are associated to each other with the frequency bandwidth setting data pieces stored in the first storing part so that the center frequency of the intermediate frequency signal matches the center frequency set in the IF filter that fluctuates by setting one of a plurality of mutually different sizes of the frequency bandwidth provided by the frequency bandwidth setting data pieces to the IF filter.