Sanyo Electric Co., Ltd.

Ryuichi Ogawa

Tsutomu Ishikawa

Masashi Arai

Kazuhisa Ishiguro

Kanji Tanaka

Noboru Usui

Masaya Tanno

Fumio Tosaka

Hirohisa Suzuki

Hirofumi Okada

Mikio Yamagishi

Akira Kabashima

Takayuki Imaida

A diversity receiver includes first and second antennae for receiving an RF signal, and an antenna switching circuit for selecting one of the first and second antennae. A first detection circuit having a high sensitivity, and a second detection circuit having a low sensitivity are provided, each detecting a noise signal contained within the received RF signal in different sensitivity. A field strength detection circuit is provided for detecting a field strength of the received RF signal, and a selection circuit is provided for selecting either one of the first and second detection circuits according to the output signal of the field strength detection circuit, and for providing a switching signal to the antenna switching circuit. Thus, when the field strength is relatively strong, the first detection circuit with high sensitivity is used for the noise detection, and when the field strength is relatively weak, the second detection circuit with low sensitivity is used for the noise detection.

Diversity receiver

A television receiver includes a volume control circuit (4) for controlling levels of sound signals corresponding to a left channel, a right channel, a center channel and a surround channel and speakers (6 to 10) corresponding to these channels. The television receiver further comprises a test tone circuit (11; 18), a microcomputer (14) and a character display circuit (16). The test tone circuit (11; 18) supplies a test tone of a prescribed frequency sequentially to the speakers (6 to 10) through the volume control circuit (4). The microcomputer (14) provides a command to the character display circuit (16) so that a CRT 17) displays which speaker is currently supplied with the test tone as well as volume levels of the respective speakers.

Sound reproducer

A surround-decoder comprises terminals to which left and right stereo input signals are applied, a decoder for processing the left and the right stereo input signals to provide left and right stereo output signals, a center output signal and a surround output signal, circuits for detecting the left and the right stereo input signals to be monaural signals, and a switch responsive to an output signal of the detecting circuit for cutting off an output of a surround signal from the decoder.

Surround decoder

A PLL circuit comprises a variable frequency divider (7) for frequency-dividing a signal having a reference frequency f.sub.1 with a frequency dividing ratio n.sub.1 or n.sub.2, a fixed frequency divider (8) for further frequency-dividing an output of the variable frequency divider with a frequency dividing ratio n.sub.0, to generate a first output signal and a second output signal which is out of phase by 90.degree. from the first output signal, multiplier (10) for multiplying an input signal by the second output signal, a comparator (11) for comparing an output of the multiplier with a predetermined reference voltage, and a D-type flip-flop (12) receiving as a D input an output of the comparator and receiving as a clock input the first output signal, an output of the D-type flip-flop (12) being applied to the variable frequency divider (7). When the second output signal leads the input signal by 90.degree. or more, the output of the D-type flip-flop (12) attains an 'L' level, so that the large frequency dividing ratio n.sub.2 is selected. On the other hand, when the second output signal lags the input signal by 90.degree. or more, the output of the D-type flip-flop (12) attains an 'H' level, so that the small frequency dividing ratio n.sub.1 is selected.

PLL circuit for generating output signal synchronized with input signal

An improved FMX sterophonic broadcast receiver provided with countermeasures against transient noises, which includes a level detection circuit for detecting level of a detected stereo difference signal, and a level control circuit for controlling level of an expanded stereo difference signal according to an output signal of the level detection circuit. By the above arrangement of the present invention, since it is so arranged to cause the level control circuit to function when the degree of modulation becomes large so as to control the level of the stereo difference signal to be low, a level difference is produced between the stereo sum signal and the stereo difference signal for deterioration of the stereo separation degree upon matrixing at a matrix circuit for reduction of noises accordingly.

FMX stereophonic broadcast receiver

An FMX stereophonic receiver receives an FMX stereophonic broadcast signal which includes a stereo sum signal, an uncompressed stereo difference signal, and a compressed stereo difference signal which is formed by modulating the uncompressed stereo difference signal by a quadrature modulation and being compressed. The FMX stereophonic receiver includes an FM detector for producing an FM detection signal including a stereo pilot signal, a PLL circuit for producing a signal which is in a synchronized relationship with the stereo pilot signal included in the FM detection signal, a synchronous detection circuit for receiving the FM detection signal and for producing the uncompressed stereo difference signal in accordance with the signal produced from the PLL circuit, a quadrature detection circuit for receiving the FM detection signal and for producing the compressed stereo difference signal in accordance with the signal produced from the PLL circuit, and a phase shifting means for shifting the phase of at least one of the FM detection signal applied to the PLL circuit and the FM detection signal applied to the detection circuits so as to correct the phase difference between the synchronous detection signal and the signal to be detected.

FMX stereophonic receiver

An FM/FMX stereophonic receiver is capable of receiving an FM or an FMX stereophonic broadcast signal. The FM stereophonic broadcast signal includes a stereo sum signal and stereo difference signal, whereas the FMX stereophonic broadcast signal further includes a compressed stereo difference signal and an FMX ID signal indicating the FMX stereophonic broadcast signal. The FM/FMX stereophonic receiver has a stereo demodulator for receiving said broadcast signal and for producing left and right stereo signals, a detector for detecting the field strength of the receiving signal, and a noise reducer, which may be a circuit for changing the mode from stereophonic mode to monaural mode or a high cut circuit for attenuating the signals of high frequency region, for reducing noise signals contained in the left and right stereo signals. The FM/FMX stereophonic receiver further has a detector for detecting the FMX ID signal and a disabling circuit for disabling the noise reducer when the FMX ID signal is detected by the detector. Instead of the disabling circuit, a timing control circuit may be provided for changing the timing at which the noise reducer starts to activate in response to the detection of the FMX ID signal.

Growing community of inventors

Gunma, Japan

Ryuichi Ogawa