Abstract: A television broadcast receiving apparatus has a demodulating unit including a PLL part synchronizing a phase of an IF signal with a phase of an internally generated carrier signal and outputting an out-of-synchronization flag signal when the IF signal and the carrier signal are in an unsynchronized state, and a muting part muting a sound intermediate frequency signal and outputting a noise signal of a predetermined level when the out-of-synchronization flag signal is outputted from the PLL part. Therefore, even when an IF amplifier of a tuning unit amplifies a noise at the maximum gain when there is no signal, an abnormal sound can be prevented from being outputted from a speaker of a decode and output unit.

Abstract: A front-end circuit according to the present invention includes a VCO which oscillates a local signal, a mixer which converts an RF signal Frf into a baseband signal, a DC offset cancel circuit which detects a DC offset contained in the baseband signal and then eliminates the DC offset, and a local frequency control circuit which controls a frequency of the local signal. In a case where the RF signal is an analog television signal, the local frequency control circuit controls the frequency of the local signal so that a frequency of the baseband signal differs from each frequency spectrum of a luminance signal contained in a video signal which is generated by demodulating the baseband signal. This makes it possible to provide the front-end circuit which can prevent video distortion caused when a frequency spectrum is eliminated from the luminance signal.

Abstract: A television broadcast receiving apparatus has a demodulating unit including a PLL part synchronizing a phase of an IF signal with a phase of an internally generated carrier signal and outputting an out-of-synchronization flag signal when the IF signal and the carrier signal are in an unsynchronized state, and a muting part muting a sound intermediate frequency signal and outputting a noise signal of a predetermined level when the out-of-synchronization flag signal is outputted from the PLL part. Therefore, even when an IF amplifier of a tuning unit amplifies a noise at the maximum gain when there is no signal, an abnormal sound can be prevented from being outputted from a speaker of a decode and output unit.

Abstract: A front-end circuit according to the present invention includes a VCO which oscillates a local signal, a mixer which converts an RF signal Frf into a baseband signal, a DC offset cancel circuit which detects a DC offset contained in the baseband signal and then eliminates the DC offset, and a local frequency control circuit which controls a frequency of the local signal. In a case where the RF signal is an analog television signal, the local frequency control circuit controls the frequency of the local signal so that a frequency of the baseband signal differs from each frequency spectrum of a luminance signal contained in a video signal which is generated by demodulating the baseband signal. This makes it possible to provide the front-end circuit which can prevent video distortion caused when a frequency spectrum is eliminated from the luminance signal.

Abstract: A terrestrial broadcast tuner section is disposed in an area A1, and frequency-converts an externally supplied terrestrial broadcast signal into an IF signal. A terrestrial broadcast analog demodulation section is disposed in an area A3, and demodulates the IF signal frequency-converted by the terrestrial broadcast tuner section. A satellite broadcast tuner section is disposed in an area A2, and frequency-converts an externally supplied satellite broadcast signal into a signal having a frequency band lower than that of the satellite broadcast signal. A digital demodulation section is disposed in an area A4, and demodulates the signal supplied from either one of the terrestrial broadcast tuner section and the satellite broadcast tuner section. With this arrangement, a broadcast receiving apparatus easily changeable from the one for analog and digital broadcasting to the one for digital broadcasting only can be provided.

Abstract: A tuner unit includes a case, first and second antenna terminals, a first tuner circuit for digital terrestrial broadcast reception, a second tuner circuit for digital satellite broadcast reception, and a plurality of external pins. The first and second antennal terminals are arranged in a line along a first straight line, and the plurality of external pins are arranged in a line along a second straight line parallel to the first straight line. A signal in the first tuner circuit flows in a direction from the first antenna terminal toward the second antenna terminal, and a signal in the second tuner circuit flows in a direction from the second antenna terminal toward the first antenna terminal. Consequently, reduction in size can be achieved while maintaining an interval between the first and second antenna terminals at a prescribed distance.

Abstract: In one embodiment of a printed circuit board securing structure and a tuner unit according to the present invention, a chassis comprises a chassis frame that surrounds the lateral faces of a printed circuit board and a shield plate that partitions the space within the chassis frame, and circuit board holding parts for holding the printed circuit board between the circuit board holding parts and the shield plate are disposed on inner wall faces of the chassis frame. The circuit board holding parts are configured to be able to secure the printed circuit board from both faces.

Abstract: A terrestrial broadcast tuner section is disposed in an area A1, and frequency-converts an externally supplied terrestrial broadcast signal into an IF signal. A terrestrial broadcast analog demodulation section is disposed in an area A3, and demodulates the IF signal frequency-converted by the terrestrial broadcast tuner section. A satellite broadcast tuner section is disposed in an area A2, and frequency-converts an externally supplied satellite broadcast signal into a signal having a frequency band lower than that of the satellite broadcast signal. A digital demodulation section is disposed in an area A4, and demodulates the signal supplied from either one of the terrestrial broadcast tuner section and the satellite broadcast tuner section. With this arrangement, a broadcast receiving apparatus easily changeable from the one for analog and digital broadcasting to the one for digital broadcasting only can be provided.

Abstract: A PLL circuit is used for a super-heterodyne television receiver. In the PLL circuit, a reference signal oscillator circuit generates a reference signal, and the reference signal is compared to a LO signal in a phase comparator. The phase comparator includes (i) an oscillating circuit, (ii) a series circuit of a correcting capacitor and an oscillator corresponding to a predetermined IF signal frequency, (iii) another correcting capacitor, and (iv) a switch. The switch is turned ON or OFF only when receiving a particular channel in which interference occurs, so as to shift the frequency of the reference signal by several ten kHz. This reduces beats in a particular channel, and prevents deterioration of picture quality in other channels. That is, interference in a particular channel can be reduced without causing any adverse effects in other channels having a relatively high frequency.