Pioneer Electronic Corporation

Tatsuo Numata

Kohji Ishida

Tadashi Noguchi

Akira Nishioka

Hitoshi Hirata

Masaharu Sakamoto

Akira Misawa

Susumu Yokoyama

An opposite-phase current source is improved by eliminating the conventionally employed current mirror circuits, and by instead using a pair of transistor current sources subjected to voltage feedback and emitter-connected via a resistor. A constant current source or sources are coupled to the opposite ends of the resistor or to a mid-point thereof.

Distortion-free, opposite-phase current source

A signal meter driving signal is derived from first and second active elements connected in parallel and controlled by opposite phase differential outputs from an IF amplifier. The active elements are biased with a bias voltage which differs by a predetermined amount from the d.c. output of the differential amplifier when no IF input signal is present.

Circuit for driving a signal meter for a receiver

An FM stereo demodulating circuit comprising a pulse counter detector 1 for generating a pulse train signal including the frequency spectrum of the FM signal, DC biasing means for current biasing the detector output about a midpoint, a subcarrier signal generator 2 and current drivers 8, 10 for generating dual polarity biased subcarrier currents, first and second transistor pairs 3, 4, the emitters of each being connected to one of the current drivers, and the bases of the pairs being cross-connected to one of the biased detector outputs, at least one reference transistor pair whose emitters are connected to a current source 11 and whose collectors are connected to each of the biased detector outputs. The currents entering the cross-connected collectors of the first and second transistor pairs, when referenced against the currents into the emitters of the reference transistor pair, produce signals proportional to the right and left channels of the FM signal.

FM Stereo demodulating circuit

An FM receiver comprising a 90 degree phase shifter 21 of the FM signal and a first multiplier 22 for multiplying the FM signal and the phase shifted signal to produce a main signal L+R and a second multiplier 6 for multiplying the FM signal, the phase shifted signal and a subcarrier wave of 38 kHz to produce a sub-signal L-R.

FM receiver

Disclosed is an FM stereo demodulator in which components of the demodulated signal corresponding to odd harmonics of the subcarrier signal are eliminated. In order to prevent the production of odd harmonics, the multiplication between positive and negative sinusoidal subcarrier signals is performed with a stereo pilot signal and positive and negative pulse train signals produced by pulse detection of an FM signal. The multiplication signals are further added with each other to directly reproduce left and right stereophonic signals.

FM Stereo demodulator for demodulating stereo signals directly from an

An FM stereo demodulator having improved separation and distortion characteristics comprising a high-frequency pulse signal which is modulated by a sinusoidal subcarrier signal produced in accordance with a stereo pilot signal. The high-frequency pulse signal is multiplied with a composite signal at a multiplier so as to reproduce left and right signals without frequency components of noise. Constructed accordingly, the invention advantageously obviates the use of a low-pass filter which injects delay characteristics and reduces gain of the composite signal from an FM demodulator.

FM stereo demodulator

A differential output leading circuit forming a part of an IF amplifier includes a pair of common collector connected transistors which receive, at control electrodes, outputs from a differential amplifier, by way of emitter follower circuits having constant current loads.

Differential amplifier output leading circuit, and intermediate

A pulse position modulated (PPM) signal is derived from an input FM signal, and first and second switching signals are derived which are opposite in phase and correspond to alternating half cycles of the PPM signal. First and second opposite phase subcarrier signals are derived synchronized to the pilot signal in the input FM signal, and various combinations of the switching and subcarrier signals are multiplied together and the multiplication products combined to obtain left and right channel outputs.

FM Stereo demodulation circuit

A multi-function sound system including an AM stereophonic receiving function in which interference with operating circuits in modes other than the AM stereophonic mode is eliminated. A limiter receives a IF AM stereophonic received signal and removes the amplitude variation components therefrom and couples the resulting signal to a phase detector composed of a phase-locked loop which produces as an output signal a sub-signal. A switch is provided which deactivates both the limiter and the voltage-controlled oscillator in the phase-locked loop circuit when the sound system is set to other than the AM stereophonic receiving mode.

Sound system having suppression of AM stereophonic receiving

An AM stereophonic receiver including a stereophonic pilot signal eliminating circuit which substantially completely eliminates a pilot signal in an input stage of a matrix detector. A received AM stereophonic signal, of the type in which the carrier signal is phase-modulated with a sub-signal and amplitude modulated by a main signal, is coupled to a main signal detector and a sub-signal detector. The output of the sub-signal detector is coupled through a band amplifier which produces as an output a signal corresponding to the pilot signal contained in the stereophonic signal. The outputs of the sub-signal detector and main signal detector are coupled to inputs of adder/subtractor circuit in a matrix detector while the output of the band amplifier is also coupled thereto in a phase so as to cancel the pilot signal contained in the output of the sub-signal detector.

Stereo pilot signal eliminating circuit for AM stereophonic receiver

A multiplex demodulation circuit in which no band elimination filter is required for eliminating beating between the mixed signals and odd harmonics of the 38 KHz switching signal derived from the 19 KHz pilot signal. The FM detection signal is logarithmicly converted as is the 38 KHz subcarrier signal. The two logarithmically converted signals are added and then inversely logarithmically converted. The inversely logarithmically converted signal is added to the FM detection signal to produce the left channel signal while the inversely logarithmically converted signal is phase inverted then added to the FM detection signal to provide the right channel signal.

Multiplex demodulation circuit

A muting circuit for an AM stereophonic receiver of the type in which a received signal is phase modulated with a sub signal and amplitude modulated with a main signal and in which noise generated under certain adverse conditions is eliminated. A first detection signal is generated when the level of a received AM stereophonic signal is lower than a predetermined value, a second detection signal is generated upon detection of a non-locked state of a phase-locked loop circuit used to detect the sub signal, a third detection signal is generated when a frequency deviation detection senses is that a free-running frequency of a voltage controlled oscillator in the phase-locked loop circuit and a frequency of the AM stereophonic signal are different in frequency by more than a predetermined value; and a fourth detection signal is generated when a stereo pilot signal is absent. A muting circuit is activated in response to any of first through fourth detection signals. The frequency deviation detector is preferably implemented as a window detector which has an input-output characteristic including hysteresis.

Muting circuit for AM stereophonic receiver

A muting switching circuit for decoupling the output signal from an FM tuner including a transistor PNP-NPN pair push-pull connected between the terminals of a power source with a current mirror circuit supplying bias to the transistor pair in response to an input muting control signal. A middle point potential equal to one-half the voltage of the power source supplying current to the circuit is connected to a common connection point of the transistor pair so that when the transistors are rendered nonconductive by control of the input control signal, the common connection point thereof, which is also the output terminal of the circuit, is brought to the middle point potential immediately so that no pop noise is produced in the output signal. Preferably, a capacitor is coupled between the source of the middle point potential and ground to slow down transitions in the output signal when the power source is switched off or on to thereby prevent pop noise in the output signal at that time.

Switching circuit

An improved muting signal generation circuit of an FM receiver of the type in which the deviation of an FM detection signal relative to a predetermined level is detected. When the deviation of the FM detected signal is above or below a predetermined value, a muting signal is generated. A band elimination filter is provided for eliminating the frequency components of an information signal contained in the FM detection signal. A detuning detection circuit detects detuning in response to the output of the band elimination filter. A muting signal generation circuit generates a muting signal in response to the detection output of the detuning detection circuit.

Muting signal generation circuit for an FM receiver

A stereophonic signal demodulation circuit receives an input signal including a signal modulated with first and second channel information to separate the first and second channel information from each other. The circuit includes first and second operational amplifiers and at least two switching devices namely, first and second switches for applying the input signal through respective resistors to one input terminal of the first operational amplifier and third and fourth switches for applying the input signal through respective resistors to one input terminal of the second operational amplifier. A control device controls the operations of the first through fourth switches and the first and second operational amplifiers outputs first and second channel information, respectively.

Growing community of inventors

Tokyo, Japan

Tatsuo Numata