Abstract: A cosine signal corrector circuit as for use in a decoder for a system wherein an information signal is transmitted in the form of one trigonometric transform function of that signal. The second trigonometric transform function signal, required for decoding the information signal, required for decoding the information signal, is obtained by first deriving the Hilbert transform of the transmitted signal and phase inverting it, producing an approximate second transform function signal. The decoder produces the sum of the squares of the two transform function signals, and the difference between that decoder output and 1.0 is an "error" signal. Under the control of the signum signal of the approximate second transform function signal, the error signal is added to the approximate second transform function signal to produce an accurate second transform function signal.

Abstract: A baseband discriminator decodes a pair of trigonometric transform function signals, sin f(t) and cos f(t), to provide an original audio signal f(t) by first deriving the derivative of the audio signal from the pair of trigonometric signals and integrating that derivative. The discriminator is used in a new system of SSB transmission termed "transform modulation" and also in FM transmission.

Abstract: The volume of gases in a container or the volume of liquid in the container is determined by creating cyclic pressure waves in the gases and detecting the waves by a second transducer. The signals produced by the second transducer are a function of the volume of gas in the container, and the volume of any liquid can be obtained by simple calculation. The signals can also provide detection of an open container and, when coupled to signals relating to the velocity of a vehicle, can provide other data such as a miles-per-gallon reading.

Abstract: 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. The instantaneous phase varies as a function of the quadrature phase relationship. Transmitter and receiver embodiments are disclosed.

Abstract: 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 modulation. The gain in the high frequency L - R channel may be reduced in proportion to the signal level only, or to both level and frequency, or to the percent of distortion introduced into the high frequencies of the L - R signal by RF filtering of the modulated carrier.

Abstract: 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) and difference information (L-R) which are established in a preselected phase relationship (quadrature). In a stereo receiver, L and R or the sum and difference signals may be restored by dividing the signal by the cosine of the angle .phi., and in a monaural receiver, the sum signal alone is detected.

Abstract: 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 in a synchronous detector, a corrector circuit derives the correction factor, and a divider circuit provides the corrected difference signal. During tuning, and until a PLL is locked on the carrier frequency, the receiver is locked into the monophonic mode and tuned on the monophonic signal. When the PLL locks, the difference signal is coupled through to the matrix for stereophonic mode operation.

Abstract: A system for the transmission and reception of two program signals L and R on a single channel by means of a compatible SSB AM stereophonic signal having the form (1+L+R)cos(.omega..sub.c t+.phi.) where .phi. is arc sin{[(L-R)/.pi./2] [1+(L +R)/2] / (1+L + R)}. The system is also applicable to transmission of one program signal on one set of sidebands.

Abstract: A CSSB system for AM stereo provides both second and third order sideband correction in the transmitted signal for reduction of distortion at the receivers. Sum and difference signals are derived from two audio program signals (L and R) and shifted in phase 90.degree. with respect to each other. The carriers is then phase modulated with the ratio of these two signals and amplitude modulated with the sum signal.

Abstract: 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.

Abstract: 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.

Abstract: The cosine correction factor of a receiver for compatible AM stereo reception is controlled by the amount of high frequency energy present in the demodulated signal. Large amounts of such energy indicate a low signal-to-noise ratio and cosine correction under such conditions is then not desirable. During periods of excessive high frequency energy, a filter circuit output causes a switching circuit to remove the derived cosine correction factor and cause division of the demodulated signal by a factor of one instead.

Abstract: 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.

Abstract: 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 instantaneous or an average signal level.

Abstract: 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 infrasonic detector for control of a mono/stereo mode switch and a stereo presence indicator. When the received signal is weak, the infrasonic tone is effectively stronger, because the phase angle is increased. Since the s/n ratio is proportional to the phase angle, the stereo presence signal is self-adjusting. The mode switch and indicator are enabled for all values of L and R. The infrasonic tone could also be removed from the transmitted signal whenever the difference signal goes above a predetermined level during stereo broadcasting, in which case a comparator at the receiver would enable the mode switch and indicator upon detection of either a difference signal or the infrasonic tone.

Abstract: A double deflection scanning system for electron beam instruments is provided embodying a means of correcting isotropic coma, and anisotropic coma aberrations induced by the magnetic lens of such an instrument. The scanning system deflects the beam prior to entry into the magnetic lens from the normal on-axis intersection of the beam with the lens according to predetermined formulas and thereby reduces the aberrations.