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Hilbert; Francis H.
Addison, IL
No. of patents:

Patent Number Title Of Patent Date Issued
4406922 Stereo broadcast system September 27, 1983
The signal transmitted is a compatible amplitude modulated carrier with amplitude directly proportional to the monaural information or 1+L+R up to a frequency near the upper end of the normal program spectrum. Above the transition region, the amplitude becomes a pure quadrature function.
4377728 Phase locked loop with improved lock-in March 22, 1983
The circuit determines whether an incoming frequency is within the normal "lock-in" range of a phase locked loop VCO or not, and whether it is higher or lower than the VCO frequency. If not within normal range, the beats are rectified and gated to provide a DC control voltage of the
4371747 AM Stereophonic decoder February 1, 1983
A decoder for use with a compatible AM stereophonic signal utilizes a amplifier and a feedback loop from the amplifier output to control the output of a multiplier circuit which is one input to the amplifier. The amplifier output is thus forced to become the required correction factor
4338491 Compatible AM stereophonic system July 6, 1982
The signal as transmitted is a compatible AM stereophonic signal with amplitude directly proportional to the monophonic signal 1+L+R. The instantaneous phase angle is the quadrature phase angle modified in that high level, high frequencies in the L-R channel are reduced before carrier
4218586 Compatible AM stereo broadcast system August 19, 1980
A compatible AM stereo broadcasting system is disclosed in which the signal is a carrier having an amplitude directly variable with monoaural or sum (L+R) information, and having an instantaneous phase .phi. varying as a function of the resultant amplitude of the sum information (L+R) an
4192968 Receiver for compatible AM stereo signals March 11, 1980
An improved AM stereo receiver for receiving broadcast signal having the form (1+L+R)cos(.omega..sub.c t+.phi.) where .phi. is arc tan(L-R)/(1+L+R). The sum signal (L+R) is demodulated in an envelope detector and coupled to a matrix. The uncorrected difference signal is demodulated i
4172966 AM stereophonic receiver October 30, 1979
An AM receiver for utilizing a broadcast signal of the form (1+L+R) cos (.omega..sub.c t+.phi.) separates the L and R signals by utilizing phase detection and matrixing. Distortion is either eliminated with non-linear amplification or reduced with partial matrixing.
4170716 AM stereo receiver with correction limiting October 9, 1979
An AM receiver receiving a compatible stereo signal and utilizing a cosine correction signal for restoring the original stereo information limits the amount of correction at very large modulation angles to prevent excessive noise from being introduced by the increased gain.
4164623 AM stereo receiver with improved correction signals August 14, 1979
An AM receiver for receiving a compatible stereo signal and requiring a dynamic correction factor prevents the introduction of a false phase reference signal by limiting and filtering the signal going into the oscillator of the PLL which provides the correction reference signal.
4159398 Stereo presence signal for an AM stereo system June 26, 1979
In an AM broadcast transmitter, an infrasonic tone is added to the difference channel of a compatible AM stereo system to provide a stereo presence signal. In a stereophonic receiver, the corrected output of a synchronous detector in the difference signal channel is coupled to an inf
4159396 AM stereo receiver having signal-controlled corrector June 26, 1979
A signal level controlled switching circuit removes the stereo correction factor in a compatible AM stereo receiver when the received signal level is low enough to allow signal degradation due to noise affecting the correction factor. The switching circuit can operate on either an in
4051532 Auxiliary signal processing circuit for television receivers September 27, 1977
A low level video auxiliary signal is transmitted in addition to the conventional composite black and white or color television signal. The auxiliary signal is in the form of redundant, opposite-polarity signal portions during pairs of time successive signal portions, such as horizon

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