Antinoise Patents (Class 381/13)
  • Patent number: 5337196
    Abstract: A stereo/multivoice recording and reproducing apparatus used for a high fidelity video tape recorder comprises a multi-channel television system (MTS) decoder for demodulating stereo and multivoice signals included in an IF signal supplied from a tuner, a high fidelity audio processor for frequency-modulating the stereo signal output from a MTS decoder, left and right channel heads for recording the stereo signal frequency-modulated in the high fidelity audio processor, a second audio processor for amplifying the multivoice signal from the MTS decoder, and a third audio head for recording the multivoice signal amplified in the second audio processor. According to one aspect of the invention, the apparatus can simultaneously record stereo and multivoice signal and selectively reproduce one of the stereo signal and the multivoice signal.
    Type: Grant
    Filed: January 31, 1992
    Date of Patent: August 9, 1994
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Sang-uk Kim
  • Patent number: 5315660
    Abstract: A decoding arrangement for decoding audio signals previously encoded in accordance with the dbx format, includes a wideband expander instead of a full dbx expander. The wideband expander employs a relatively simple, and therefore inexpensive, peak detector in place of the true RMS detector of a full dbx expander, and does not include apparatus for spectral expansion of the audio signal. Although the decoding is noncomplementary with respect to the encoding, the stereo audio reproduction as perceived by a listener, is surprisingly good.
    Type: Grant
    Filed: July 26, 1993
    Date of Patent: May 24, 1994
    Assignee: Thomson Consumer Electronics, Inc.
    Inventors: Mark R. Anderson, Robert P. Parker
  • Patent number: 5261004
    Abstract: An AM stereo input signal is processed by an envelope detector, an in-phase detector and a quadrature phase detector to yield outputs which may carry short noise impulses. Each output is low pass filtered to derive an average signal level and each output is ratiometrically compared to the corresponding average to detect a tic or modulation substantially above the average. In response to a tic a hold circuit generates a flag for a period which depends on the quality of the input signal. A dual mode deemphasis and sample/hold circuit normally filters the audio signal in each channel and is effective for the duration of the flag to hold the existing signal in the circuit to blank out the noise impulse.
    Type: Grant
    Filed: December 17, 1991
    Date of Patent: November 9, 1993
    Assignee: Delco Electronics Corporation
    Inventors: Gregory J. Manlove, Jeffrey J. Marrah, Richard A. Kennedy, Mark A. Kady, Marvin G. Stang
  • Patent number: 5257312
    Abstract: A receiver having a signal path incorporating a tuner, a demodulator circuit for supplying a stereo multiplex signal having a baseband stereo sum signal (L+R), a 19 kHz stereo pilot and a stereo difference signal (L-R) which is double sideband amplitude-modulated on a suppressed 38 kHz subcarrier, a sampler for converting an analog signal into a time-discrete signal and a stereo decoder for time-division multiplex decoding of a time-discrete stereo multiplex signal into time-discrete left and right stereo signals. In order to realize an effective selection of the stereo multiplex signal by an easily integrable low-pass filter, the stereo decoder includes a time-discrete halfband low-pass filter circuit having a finite impulse response, with a transition band which is substantially located in the frequency range of said modulated stereo difference signal and with a half-value transfer which is located at the frequency of said 38 kHz stereo subcarrier.
    Type: Grant
    Filed: April 23, 1992
    Date of Patent: October 26, 1993
    Assignee: U.S. Philips Corporation
    Inventors: Dieter E. M. Therssen, Johan K. J. Van Ginderdeuren
  • Patent number: 5255319
    Abstract: A noise suppressing circuit has a gate for controlling a composite signal applied to a stereo demodulator of an FM tuner, and a detector for detecting a noise included in the composite signal and for producing a noise dependent signal for controlling the gate to close it. A pilot signal detector is provided for detecting a pilot signal included in the composite signal for producing a pilot dependent pulses. In response to the noise dependent signal and to the pilot dependent pulses, gate control pulses are applied to the gate, thereby closing the gate in synchronism with the pilot signal.
    Type: Grant
    Filed: March 29, 1991
    Date of Patent: October 19, 1993
    Assignee: Pioneer Electronic Corporation
    Inventors: Tetsuo Nakamura, Masahide Terada
  • Patent number: 5253298
    Abstract: A receiver for receiving a stereophonic signal with upper and lower sidebands carrying a modulating signal includes independent sideband circuitry for providing upper and lower sideband signals. Selector circuitry responds to the level of audible noise in each of the upper and lower sideband signals for selecting that one of the sideband signals having a lower level of audible noise relative to the other. An ISB highpass filter filters the latter sideband signal to provide a highpass filtered sideband signal. Stereo detector circuitry provides left and right stereophonic audio signals. At least one audio lowpass filter filters the left and right stereophonic signals to provide corresponding lowpass filtered left and right stereophonic audio signals. At least one signal combiner combines the highpass filtered sideband signal with each of the lowpass filtered left and right stereophonic audio signals to provide corresponding composite left and right audio signals.
    Type: Grant
    Filed: April 18, 1991
    Date of Patent: October 12, 1993
    Assignee: Bose Corporation
    Inventors: Robert P. Parker, William R. Short
  • Patent number: 5253299
    Abstract: A noise reduction apparatus in an FM stereo tuner including a circuit for generating a stereo sum signal and a stereo differential signal; a noise eliminating circuit for dividing, in accordance with several frequency bands, the stereo differential signal into several divisional signals and for outputting, in accordance with signals levels corresponding to the frequency bands, a composite signal of divisional stereo differential signals respectively corresponding to the signal levels; and a circuit for reproducing a stereo signal from the composite signal and the stereo sum signal.
    Type: Grant
    Filed: July 20, 1992
    Date of Patent: October 12, 1993
    Assignee: Pioneer Electronic Corporation
    Inventors: Kohji Ishida, Yasushi Nishimura, Shigeru Yamaguchi
  • Patent number: 5249233
    Abstract: A frequency modulation (FM) stereo broadcast receiver detects the onset of multipath interference and initiates corrective action to minimize the audible effects of multipath. Under an unacceptable multipath interference condition, a multipath detection signal disables the FM RF mixer thereby preventing any further energy in the multipath event from entering succeeding sections of the receiver. This action reduces noise generated by multipath interference and allows the output to return to normal in a shorter time. In another aspect of the invention, a phase-locked loop employed in a stereo decoder circuit is latched during the multipath disturbance in order to avoid rapid changes in the phase of the regenerated pilot employed in the stereo decoder.
    Type: Grant
    Filed: April 6, 1992
    Date of Patent: September 28, 1993
    Assignee: Ford Motor Company
    Inventors: John F. Kennedy, Robert D. Plowdrey
  • Patent number: 5241687
    Abstract: Apparatus for demodulating information signals frequency-modulated on an RF carrier signal carrying spectral components within the audio frequency range, a pilot carrier signal having an imparted phase shift from the phase of the transmitted pilot carrier signal, and amplitude-modulated spectral components having another imparted phase shift in a subcarrier channel frequency range above the audio frequency range. The apparatus includes a demodulator for demodulating the frequency-modulated information signals to provide a detected composite signal which includes a detected pilot carrier characterized by an imparted phase shift due to the effects of multipath reception, and detected amplitude modulated spectral components exhibiting another multipath induced phase shift.
    Type: Grant
    Filed: February 14, 1991
    Date of Patent: August 31, 1993
    Assignee: Bose Corporation
    Inventor: William R. Short
  • Patent number: 5226088
    Abstract: Method and apparatus for active noise suppression in stereo multiplex signals particularly in an automotive radio receiver includes an insertion circuit where the disturbed signal section is replaced with an insertion signal formed by sampled signal values/signal sections which are located before and/or after the disturbed signal section. Basic-delay stages ensure that only those sample values are used for the insertion signal which are separated from the respective instant of insertion by a time interval having an integral relationship nT to the period T of a carrier contained in the stereo multiplex signal (where n is a positive integer).
    Type: Grant
    Filed: March 29, 1991
    Date of Patent: July 6, 1993
    Assignee: SamSung Electronics Co., Ltd.
    Inventors: Martin Winterer, Dieter Baecher
  • Patent number: 5204904
    Abstract: A system for increasing the quality of the sound available from a broadcast, frequency modulated, radio frequency, stereophonic signal. Sound quality is promoted by: (1) so switching between available antennas that the signal available from the antenna receiving the incoming signal which is stronger and contains the least multipath distortion is processed into audio output signals, and (2) at least partially blending stereophonically related audio input signals into a monophonic signal if the modulation of the incoming first and second audio signals decreases below a selected threshold value and if: (a) the multipath distortion in the incoming signal reaches or exceeds a preselected threshold value, or (b) the strength of the incoming signal decreases to, or falls below, an also preselected threshold value.
    Type: Grant
    Filed: December 1, 1986
    Date of Patent: April 20, 1993
    Assignee: Carver Corporation
    Inventors: Robert W. Carver, Victor O. Richardson
  • Patent number: 5202924
    Abstract: A stereo decoder for use in a stereo FM radio receiver includes a phase-locked loop; for detecting the 19 KHz pilot signal in the FM composite signal; for generating the 38 KHz subcarrier for use as a reference signal to a double balanced gating circuit that combines he L-R and L+R components of the stereo composite signal to produce the left audio and right audio signals separately; and for providing a 19 KHz reference signal for use in the pilot detector and pilot indicator circuit. The phase-locked loop includes a mixer to which a 19 KHz reference and the composite signals are applied, a low pass filter switchable from a first bandpass of about 300 Hz to a second bandpass of about 10 Hz connected to the output of the mixer a voltage controlled oscillator connected to the output of the filter that has a natural operating frequency of 38 KHz and a divide-by-two circuit connecting the oscillator to an input of the mixer.
    Type: Grant
    Filed: December 22, 1989
    Date of Patent: April 13, 1993
    Assignee: Allegro Microsystems, Inc.
    Inventor: Oliver L. Richards, Jr.
  • Patent number: 5202925
    Abstract: An FM stereophonic receiver including an FM detector circuit for detecting an intermediate frequency signal, and for providing a main signal and a sub signal in response to the detected intermediate frequency signal, a first high cut circuit, connected to receive the main signal, for providing a first high cut signal, a high cut control circuit for providing a high cut control signal in accordance with a received signal field strength level, the first high cut circuit controlling a frequency characteristic of the main signal in accordance with the high cut control signal, a second high cut circuit for providing a second high cut signal, a separation control circuit for providing a separation control signal in accordance with the received signal field strength level, the second high cut circuit controlling a frequency characteristic of the sub signal in accordance with the separation control signal, and a stereophonic demodulation circuit for providing separated right and left channel signals.
    Type: Grant
    Filed: March 27, 1991
    Date of Patent: April 13, 1993
    Assignee: Pioneer Electronic Corporation
    Inventor: Katsuaki Kawamura
  • Patent number: 5201001
    Abstract: Disclosed is a pilot signal cancelling system employed in an FM stereo receiver which does not cause deterioration of the S-N ratio.
    Type: Grant
    Filed: January 30, 1992
    Date of Patent: April 6, 1993
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Masashi Itoh
  • Patent number: 5179593
    Abstract: An FM stereo receiving device according to the present invention has an object to be able to demodulate a stereo signal in a state close to a monaural reception, in which a pilot signal is extracted from an FM-demodulated output; a subcarrier signal is formed, based on this pilot signal; IF signals are switched intermittently by this subcarrier signal; and intermittent IF signals are IF-detected to obtain intermittent signals of base-band signals.These intermittent signals are switched by means of two switches, based on a subcarrier signal. Low frequency components of each output audio signal are extracted to obtain left and right signals EL and ER through a de-emphasis circuit.Owing to this device, it is possible to enlarge a reception region for an FM stereo broadcast with a high sensitivity.
    Type: Grant
    Filed: September 27, 1991
    Date of Patent: January 12, 1993
    Assignee: Clarion Co., Ltd.
    Inventor: Haruo Sakata
  • Patent number: 5170081
    Abstract: The present invention relates to a ground isolation circuit for use in connecting electronic circuits at the pre-stage and the post-stage having signal lines assigned for a plurality of channels, wherein the interconnection of the two electronic circuits is performed by employing a shielded signal cable for each channel, discrete ground terminals are provided at either of the electronic circuits, one for each channel, and thereby each shielding braid of the shielded signal cable is connected independently to the discrete ground terminal with every channel. Accordingly, no loop circuit is formed through the shielding braids, thus resulting in no induced noise even if there is an interlinkage of external radiation noise with the shielding braids.
    Type: Grant
    Filed: October 24, 1991
    Date of Patent: December 8, 1992
    Assignee: Pioneer Electronic Corporation
    Inventors: Hiroo Adachi, Mitsuo Nakazato, Kouzo Nozawa, Toshiro Araki, Mutsuro Tanoue, Mitsumasa Watanabe
  • Patent number: 5131047
    Abstract: A noise suppressor is disclosed in which a noise signal is detected by a first detector, then processed by an adaptive filter, and an output signal from the adaptive filter and an audio signal from audio equipment are added by an adder and reproduced by a speaker. The sound signal thus reproduced by the speaker and the noise signal are detected by a second detector located at a listening point and sent to a filter control circuit. The filter control circuit possesses the signal sent from the second detector and the audio signal from the audio equipment having a transfer function from the adder to the filter control circuit convoluted thereby to remove the audio signal component therefrom. The adaptive filter adaptively controls the noise signal in response to the output signal from the filter control circuit.
    Type: Grant
    Filed: June 7, 1991
    Date of Patent: July 14, 1992
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Hiroyuki Hashimoto, Nakama Yasutoshi, Tomokazu Suzuki, Terai Kenichi, Suzuki Ryoji
  • Patent number: 5125105
    Abstract: The reception of FM broadcast signals having a selected high sound quality is determined according to criteria including a low noise level and the absence of interference. The high quality information is employed to terminate a scan tuning operation or to activate an ultrasonic noise filter to improve listening quality of the FM audio output. The absence of noise and interference is determined by examining a particular frequency range from the FM field intensity line generated by an intermediate frequency circuit.
    Type: Grant
    Filed: November 30, 1989
    Date of Patent: June 23, 1992
    Assignee: Ford Motor Company
    Inventors: John F. Kennedy, Yao H. Kuo
  • Patent number: 5113446
    Abstract: The stereo separation provided by a radio receiver is controlled in dependence on the radio frequency environment at the receiver antenna. The blend curve for determining stereo separation in dependence on the field intensity of a received signal is dynamically shifted to maintain the average magnitude of a blend control signal at a predetermined magnitude if the field intensity is above a threshold. Otherwise the blend control signal follows a lower limit blend curve of predetermined shape.
    Type: Grant
    Filed: December 17, 1990
    Date of Patent: May 12, 1992
    Assignee: Ford Motor Company
    Inventor: John F. Kennedy
  • Patent number: 5103480
    Abstract: There is provided a FMX ID signal detection apparatus for discriminating between a FM broadcasting by means of a FM signal including a sum and difference signals M and S obtained from stereophonically related audio frequency source signals by matrix processing and a FMX broadcasting by means of a FMX composite signal including a compressed difference signal SD obtained by compresssing the dynamic range of the signal S, a FMX identification signal and the signals M and S.
    Type: Grant
    Filed: August 15, 1990
    Date of Patent: April 7, 1992
    Assignee: Victor Company of Japan
    Inventor: Yoshito Igarashi
  • Patent number: 5091943
    Abstract: In an FM stereo receiving device according to the present invention, a received first FM-modulated wave is demodulated by means of an FM-demodulator, from the demodulated output of which a subcarrier signal is produced, further a monaural signal is extracted by means of an LPF, and the monaural signal is again FM-modulated by means of a voltage controlled oscillator to obtain a second FM-modulated wave. Then a difference frequency component wave is produced by a multiplication operator and an LPF, starting from the first FM-modulated wave and the second FM-modulated wave and the FM-modulated wave and the difference frequency component wave are switched over with the subcarrier signal by means of a switch circuit. In this way signals of a right ear side component and a left ear side component are obtained and a stereo signal is obtained by FM-demodulating both the signals by means of the FM-demodulator.
    Type: Grant
    Filed: August 29, 1990
    Date of Patent: February 25, 1992
    Assignee: Clarion Co., Ltd
    Inventor: Haruo Sakata
  • Patent number: 5091957
    Abstract: A decoding arrangement for decoding audio signals previously encoded in accordance with the dbx format, includes a wideband expander instead of a full dbx expander. The wideband expander employs a relatively simple, and therefore inexpensive, peak detector in place of the true RMS detector of a full dbx expander, and does not include apparatus for spectral expansion of the audio signal. Although the decoding is noncomplementary with respect to the encoding, the stereo audio reproduction as perceived by a listener, is surprisingly good.
    Type: Grant
    Filed: April 18, 1990
    Date of Patent: February 25, 1992
    Assignee: Thomson Consumer Electronics, Inc.
    Inventors: Mark R. Anderson, Robert P. Parker
  • Patent number: 5077797
    Abstract: An FM stereo receiver for receiving FM stereo broadcast signals includes a pro-logic surround system in which the left stereo signal, a right stereo signal, a stereo sum signal and a stereo difference signal are selectively emphasized. Also includes a noise signal detector for detecting the noise signal in the received signal, and a device for disabling the pro-logic surround system when the noise signal is detected.
    Type: Grant
    Filed: May 23, 1990
    Date of Patent: December 31, 1991
    Assignee: Sanyo Electric Co., Ltd.
    Inventor: Tsutomu Ishikawa
  • Patent number: 5068896
    Abstract: A system for reducing audible noise in a stereo receiver includes a stereo demodulator having a monophonic signal output and a difference signal output. There is a left signal combiner and a right signal combiner. At least one filter having a controllable variable cutoff frequency intercouples at least one of the difference signal output and the monophonic signal output with the left and right combiners. A control signal generator has a control signal output coupled to the control signal input of the variable cutoff frequency filter.
    Type: Grant
    Filed: September 18, 1990
    Date of Patent: November 26, 1991
    Assignee: Bose Corporation
    Inventor: William R. Short
  • Patent number: 5067157
    Abstract: A noise reduction apparatus in an FM stereo tuner including a circuit for generating a stereo sum signal and a stereo differential signal; a noise eliminating circuit for dividing, in accordance with several frequency bands, the stereo differential signal into several divisional signals and for outputting, in accordance with signals levels corresponding to the frequency bands, a composite signal of divisional stereo differential signals respectively corresponding to the signal levels; and a circuit for reproducing a stereo signal from the composite signal and the stereo sum signal.
    Type: Grant
    Filed: November 29, 1989
    Date of Patent: November 19, 1991
    Assignee: Pioneer Electronic Corporation
    Inventors: Kohji Ishida, Yasushi Nishimura, Shigeru Yamaguchi
  • Patent number: 5046129
    Abstract: A receiver for receiving a transmitted signal comprising first and second bandwidth limited component signals modulating a single high frequency carrier in phase quadrature with the first component signal as originally transmitted including an identification signal has a source of a reference signal subject to phase error. Circuitry combines the received transmitted component signals with the reference signal to provide first and second demodulated signals characteristic of the first and second component signals respectively. A detector responds to the first and second demodulated signals to provide first and second detected components of the identification signal. Feedback circuitry responds to the detected components of the identification signal by providing a correction signal that is applied to the source of reference signal to reduce the phase error.
    Type: Grant
    Filed: January 24, 1989
    Date of Patent: September 3, 1991
    Assignee: Bose Corporation
    Inventor: William R. Short
  • Patent number: 5036543
    Abstract: A noise component is extracted either from FM-detected output or from the so-called signal meter in the intermediate frequency amplifier. The noise component is amplified and rectified to provide a d-c signal indicative of the noise level. The rectified noise is then shaped to produce a control signal having a predetermined level and a width. The control signal is supplied to the gate circuit to control the opening and closing of the gate through which the FM detected output passes. The gate is closed during a period when the pulse noise is superimposed on the FM detected output, and is opened during a period when the pulse noise is not superimposed to the FM detected output. In the mean time, the rectified d-c signal is smoothed out to be used as a control signal for controlling the stereo separation, the attenuation of high frequency component of the MPX-demodulated audio outputs, and the overall signal level of the audio outputs.
    Type: Grant
    Filed: June 26, 1990
    Date of Patent: July 30, 1991
    Assignee: Pioneer Electronic Corporation
    Inventor: Eiji Ueno
  • Patent number: 5027402
    Abstract: An FM stereo decoding and separating circuit has an (AM) demodulator multiplier to which is connected the FM stereo composite signal and a signal of dominant frequency equal to and in phase (0.degree.) with respect to the pilot signal for retrieving the L-R signal from the composite signal. This demodulator also has a blend control circuit for diminishing the magnitude of the L-R signal as a function of a blend control voltage that may be applied to the input of the blend control circuit. The decoding circuit also includes a special multiplier to which is connected the FM stereo composite signal and a signal of dominant frequency equal to that of the 38 KHz subcarrier but shifted 90.degree.
    Type: Grant
    Filed: December 22, 1989
    Date of Patent: June 25, 1991
    Assignee: Allegro Microsystems, Inc.
    Inventors: Oliver L. Richards, Jr., Thomas L. Field
  • Patent number: 5001757
    Abstract: A stereo FM radio transmission system with FMX transmission and reception capability includes a transmitter that transmits a pilot-coherent FMX-tone indicator signal at a frequency of an exact integer submultiple of the pilot frequency. The system also includes a receiver for dividing the frequency of the received pilot signal by various submultiples, nearly equal to the exact submultiple, toward quickly finding a match in phase of the received tone and the received pilot and finally dividing the pilot by the exact submultiple to establish an operational lock mode of the receiver tone detector to keep-on an FMX-indicator lamp, to change the receiver decoder to an FMX-reception operating mode and to stand by to quickly recapture the pilot and FMX-tone in the event of multipath or other interfering signals.
    Type: Grant
    Filed: December 22, 1989
    Date of Patent: March 19, 1991
    Assignee: Sprague Electric Company
    Inventors: Thomas L. Field, Oliver L. Richards, Jr.
  • Patent number: 4982431
    Abstract: A signal distinction circuit comprising a noise detector for detecting a noise included in a received signal; and a maintaining circuit for maintaining the condition of a signal outputted from a detector for detecting a discrimination signal according to a signal outputted from the noise detector so that since the noise detector and the maintaining circuit prevent the condition of a signal outputted from the distinction circuit from being changed when an inteference such as a multipath interference occuurs, an output corresponding to a received signal can be reliably obtained.
    Type: Grant
    Filed: November 16, 1989
    Date of Patent: January 1, 1991
    Assignee: Sanyo Electric Co., Ltd.
    Inventor: Masaya Tanno
  • Patent number: 4977597
    Abstract: Stereo receiver circuit for processing a multiplex signal comprising a pilot signal by means of a pilot signal detector which detects frequency components in the multiplex signal at the frequency of the pilot signal and which controls a Schmitt trigger for influencing the mono/stereo operation, said circuit also comprising a control circuit capturing the noise components in the multiplex signal and acting on the Schmitt trigger. To prevent the Schmitt trigger from switching between the state for mono operation and the state for stereo operation in the case of weak reception field strengths, the control circuit is only active in mono operation and influences the input signal of the Schmitt trigger in the case of reception of sufficiently strong noise components to such an extent that the Schmitt trigger remains in its switching state for mono operation.
    Type: Grant
    Filed: July 18, 1989
    Date of Patent: December 11, 1990
    Assignee: U.S. Philips Corp.
    Inventor: Manfred L. A. Horl
  • Patent number: 4975953
    Abstract: An FM stereo radio circuit has an ultrasonic noise detector and an amplitude noise detector each for detecting impulse noise by developing an average noise signal and comparing the average noise signal with an attenuated value of the instantaneous noise signal to generate a noise flag. A dual mode circuit normally operates as a low pass filter for a deemphasis function and is switched by the noise flag to operate as a sample and hold circuit which blanks the noise pulse. The dual mode circuit uses a switched capacitance design and is driven by clock signals to serve as a filter. The clock signals are stopped by the noise flag to effect the sample and hold function.
    Type: Grant
    Filed: January 13, 1989
    Date of Patent: December 4, 1990
    Assignee: Delco Electronics Corporation
    Inventors: Richard A. Kennedy, Gregory J. Manlove, Jeffrey J. Marrah, Seyed R. Zarabadi
  • Patent number: 4947431
    Abstract: A circuit is provided which gauges the amount of significant high-frequency spectral energy in the very recent history of the program material and ignores the effects of short noise bursts and other transients associated with FM reception in the moving vehicle. The circuit provides an output voltage which can be used to adjust the attack characteristics of an audio processor.
    Type: Grant
    Filed: September 13, 1989
    Date of Patent: August 7, 1990
    Assignee: Delco Electronics Corporation
    Inventors: Richard S. Stroud, Fred J. Anderson, Matthew C. Reprogle, Douglas E. White, Jeffrey J. Marrah, Gregory J. Manlove
  • Patent number: 4933974
    Abstract: A switched capacitor low pass filter is used to sample an FM stereo composite signal with non-overlapping clock signal to achieve phase or magnitude detection of the 19 kHz pilot without being adversely affected by the presence of information at or about 57 kHz.
    Type: Grant
    Filed: August 14, 1989
    Date of Patent: June 12, 1990
    Assignee: Delco Electronics Corporation
    Inventors: Jeffrey J. Marrah, Gregory J. Manlove, Richard A. Kennedy
  • Patent number: 4932058
    Abstract: A switched capacitor pilot cancellation circuit included in an FM stereo decoder signal path which substantially eliminates the 19 kHz pilot from the FM composite by subtracting a reconstructed pilot frequency signal from the FM composite. The reconstructed pilot signal is obtained by applying the DC output voltage of a pilot magnitude detector to a switched capacitor network which is sampled by clock signals which convert the DC to 19 kHz.
    Type: Grant
    Filed: August 14, 1989
    Date of Patent: June 5, 1990
    Assignee: Delco Electronics Corporation
    Inventors: Jeffrey J. Marrah, Gregory J. Manlove, Richard A. Kennedy
  • Patent number: 4916741
    Abstract: An FMX stereophonic receiver for receiving an FMX stereophonic broadcast signal, which includes a stereo sum signal, a stereo difference signal and a compressed stereo difference signal, is disclosed. When multipath interference takes place, noise signal will be produced, which adversely affects on a level control of an added signal of the stereo difference signal and the compressed stereo difference signal. The disclosed receiver includes a detector for detecting the multipath noise signal contained in the FMX stereophonic broadcast signal. When the multipath noise signal is detected, FMX receiving mode is automatically changed to FM receiving mode by a selecting means, so as to reduce the affect of the noise signal.
    Type: Grant
    Filed: March 21, 1988
    Date of Patent: April 10, 1990
    Assignee: Sanyo Electric Co., Ltd.
    Inventor: Tsutomu Ishikawa
  • Patent number: 4901350
    Abstract: A closed-loop attenuator for an FM stereo receiver provides attenuation to the L+R audio signal in a controlled and predictable reaction to an ultrasonic noise (USN) voltage presented to an input amplifier. This is accomplished through a closed-loop circuit configuration including a multiplier which modulates the current output of the input amplifier in accordance with the output of a master differential amplifier and supplies the modulated current to a gain stage connected to the input of the master differential amplifier. The output of the master amplifier is mirrored by a slave differential amplifier which applies the actual audio signal attenuation. The closed-loop configuration confines this linear control action to a very narrow range. Outside of this range, the circuit provides either full attenuation or no attenuation.
    Type: Grant
    Filed: April 20, 1989
    Date of Patent: February 13, 1990
    Assignee: Delco Electronics Corporation
    Inventors: Fred J. Anderson, Richard A. Kennedy, Gregory J. Manlove, Jeffrey J. Marrah
  • Patent number: 4866779
    Abstract: An audio processor for adaptively rejecting undesired noise and interference in an audio input which includes a variable Q, 10 kHz switched capacitor notch filter. The Q of the notch filter is varied by a control loop responsive to the 10 kHz content of the audio signal. The notch filter includes a summer section that is clocked at a predetermined frequency, and an integrator section which is clocked at a multiple of the predetermined frequency in order to prevent center frequency variation with changes in Q of the notch filter.
    Type: Grant
    Filed: July 13, 1988
    Date of Patent: September 12, 1989
    Assignee: Delco Electronics Corporation
    Inventors: Richard A. Kennedy, Seyed R. Zarabadi, Fred J. Anderson, Marvin G. Stang
  • Patent number: 4852167
    Abstract: 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.
    Type: Grant
    Filed: January 14, 1988
    Date of Patent: July 25, 1989
    Assignee: Sanyo Electric Co., Ltd.
    Inventors: Noboru Usui, Kanji Tanaka, Ryuichi Ogawa, Tsutomu Ishikawa, Kazuhisa Ishiguro, Masashi Arai
  • Patent number: 4833715
    Abstract: An FM stereo receiver includes a level detecting circuit for detecting the received electric field intensity and a pseudo stereo circuit for changing the phase of an entered signal and outputting two signals different in phase. When the level detecting circuit detects a received electric field intensity below a threshold level, monaural signals produced from outputs of a stereo demodulator are applied to the pseudo stereo circuit to produce pseudo stereo signals.
    Type: Grant
    Filed: November 12, 1987
    Date of Patent: May 23, 1989
    Assignee: Alps Electric Co., Ltd.
    Inventor: Tsuneo Sakai
  • Patent number: 4829570
    Abstract: A device comprised of separate transmitter and receiver sections, which converts an audio signal into an F.M. signal, transmits the F.M. signal over A.C. power lines, and reconverts the F.M. signal into an audio signal, which can then be outputted to loudspeakers or other devices. By transmitting the signal over A.C. lines, no long wires are needed to connect remote loudspeakers or other devices to the source of the audio signal.
    Type: Grant
    Filed: May 22, 1987
    Date of Patent: May 9, 1989
    Assignee: Recoton Corporation
    Inventor: Larry Schotz
  • Patent number: 4821322
    Abstract: Apparatus demodulates frequency-modulated information signals on a radio frequency signal carrying on a suppressed superaudio carrier signal, amplitude-modulated spectral components in a subcarrier channel frequency range above the audio frequency range and frequency modulated spectral components within the audio range. A demodulator demodulates the frequency-modulated information signals to provide detected audio signals having spectral components within the audio frequency range and detected superaudio signals having spectral components including those within the subcarrier channel frequency range above the audio frequency range in response to modulated radiated radio frequency signals arriving at the apparatus over a number of paths of different lengths.
    Type: Grant
    Filed: August 12, 1987
    Date of Patent: April 11, 1989
    Assignee: Bose Corporation
    Inventor: Amar G. Bose
  • Patent number: 4817151
    Abstract: A decoder for use in an FM stereo broadcasting system in which the usual difference signal S and a compressed version S' of the difference signal are transmitted, automatically selects on a continuous basis for de-matrixing with the received sum signal M either an attenuated signal S' or the usual difference signal S based on the protocol that the attenuated signal S' is always selected unless the usual difference signal S is higher in level than a predetermined threshold potential related to the signal level at the knee of the expansion characteristic. The decoder eliminates the need for the relatively expensive analog variable gain amplifier used in prior art decoders and is less sensitive to time constant errors and errors due to multipath distortions.
    Type: Grant
    Filed: November 9, 1987
    Date of Patent: March 28, 1989
    Assignee: Broadcast Technology Partners
    Inventors: Murray L. Bod, Renville H. McMann, Emil L. Torick
  • Patent number: 4815141
    Abstract: A tuner includes circuitry for conditioning an audio signal including (i) a pilot signal canceller, (ii) a noise limiter, (iii) a notch filter, and (iv) a de-emphasizer; as well as an attenuator for RF signals. In an exemplary embodiment, an AM stereo pilot signal canceller utilizes a 25 Hz signal which is added or subtracted from the left and right channels to eliminate the pilot signal. The noise limiter includes a capacitor which is switched into the feedback circuit of an operational amplifier when the input is at a selected level. The diverting of the feedback signal to the capacitor causes the amplifier to saturate thereby removing the noise from the signal. The notch filter includes first and second band pass filters which are centered at a selected frequency, e.g. 10 kHz, for removing a 10 kHz beat note. The passed band is phase shifted so that it is 180 degrees out of phase with the original signal and then added back with the original signal to remove the selected band.
    Type: Grant
    Filed: December 2, 1986
    Date of Patent: March 21, 1989
    Assignee: Carver Corporation
    Inventors: Robert W. Carver, Victor O. Richardson
  • Patent number: 4809328
    Abstract: 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.
    Type: Grant
    Filed: February 16, 1988
    Date of Patent: February 28, 1989
    Assignee: Sanyo Electric Co., Ltd.
    Inventors: Noboru Usui, Kanji Tanaka, Ryuichi Ogawa, Tsutomu Ishikawa, Kazuhisa Ishiguro, Masashi Arai
  • Patent number: 4771464
    Abstract: An FM stereophonic broadcasting system incorporating companding of the difference signal in which the broadcast signal includes both the usual difference signal and a compressed version of the difference signal which utilizes, in the transmitter, a circuit for simultaneously compressing the difference signal according to a desired characteristic and modulating the compressed difference signal onto a carrier and, in the receiver, essentially the same circuit for simultaneously demodulating and expanding an incoming compressed difference signal. Simultaneous compression/modulation is achieved by multiplying the difference signal, the carrier signal and a gain control signal, preferably derived from the output signal from the multiplier, for determining the compression characteristic, thereby producing at the output of the multiplier the carrier modulated with the difference signal compressed according to a desired characteristic.
    Type: Grant
    Filed: May 8, 1987
    Date of Patent: September 13, 1988
    Assignee: Broadcast Technology Partners
    Inventors: Jeffrey B. Kadin, David W. Stebbings
  • Patent number: 4769841
    Abstract: In the receiver of an FM stereo broadcasting system which transmits both the usual stereo difference signal S and a compressed version S' of the difference signal compressed according to a compression characteristic such that signals in a lower portion of the audio frequency spectrum are not compressed and signals having frequencies above said portion are compressed, according to a desired characteristic, instead of complementarily expanding the compressed difference signal, only those signal frequencies that have been compressed at the transmitter are expanded.
    Type: Grant
    Filed: July 9, 1987
    Date of Patent: September 6, 1988
    Assignee: Broadcast Technology Partners
    Inventor: Aldo G. Cugnini
  • Patent number: 4769840
    Abstract: A sound multiplex broadcast receiver wherein a SAP channel for a subchannel carrier wave audio signal is provided independently of a channel for the main audio signal to demodulate the subchannel audio signal by way of a noise reduction circuit. The receiver comprises a frequency characteristics correction circuit for correcting the frequency characteristics of the demodulated subchannel audio signal by diminishing the gain at a specific frequency where the distortion factor of the noise reduction circuit reaches a peak, and a noise detection circuit for detecting the level of noise in the audio signal received. The amount of correction by the correction circuit is controlled by the output of the noise detection circuit which varies with the intensity of electric field received, permitting the noise reduction circuit to produce a SAP signal output with flat frequency characteristics.
    Type: Grant
    Filed: February 4, 1987
    Date of Patent: September 6, 1988
    Assignee: Sanyo Electric Co., Ltd.
    Inventor: Akito Saisho
  • Patent number: 4761814
    Abstract: A multivoice demodulator circuit in which a sub-signal is separated from the main signal. The sub-signal may have different content and characteristic dependent upon the reception mode of the original signal. The sub-signal is given different frequency characteristics dependent upon the reception mode.
    Type: Grant
    Filed: June 20, 1986
    Date of Patent: August 2, 1988
    Assignee: Pioneer Electronic Corporation
    Inventors: Yoshiro Sugai, Hiroyuki Kimura
  • Patent number: 4752955
    Abstract: The compatibility of an FM stereophonic broadcasting system incorporating companding of the difference signal, in which both the usual difference signal and a compressed version of the difference signal are transmitted, with conventional FM receivers is improved by minimizing crosstalk from the compressed difference signal to the usual difference signal that sometimes occurs in conventional FM stereo receivers, particularly when the multiplex signal is received under multipath propagation conditions.
    Type: Grant
    Filed: March 25, 1987
    Date of Patent: June 21, 1988
    Assignee: Broadcast Technology Partners
    Inventor: Emil L. Torick