Abstract: An impedance matching and filter network is disclosed. The network performs two preselected impedance transformations and provides a filtering function to attenuate harmonics of an electrical signal delivered at an input of the network. The network may advantageously be structured in the form of balanced dual filters which are referenced to a virtual ground between them, the virtual ground being connected to a shield which surrounds the electric components. The network is particularly suitable for use with electrodeless discharge lamps to provide an impedance matching function for the induction coil and to limit RFI.
Abstract: A transmitter has an oscillator (101, 201, 303, 401, 501) that operates at frequency k multiplied by f.sub.c, thus the oscillator (101, 201, 303, 401, 501) outputs a signal at an output frequency, kf.sub.c. Coupled to the oscillator (101, 201, 303, 401, 501) is a frequency modifier (103, 205, 307, 405, 505), for modifying the oscillator output frequency by factor 1/k, thereby producing a signal at frequency f.sub.c at the frequency modifier output. Coupled to the frequency modifier output is a modulator (105, 215, 301, 407-417, 507-517) for producing a modulated output signal substantially centered at frequency f.sub.c.
September 24, 1993
Date of Patent:
July 9, 1996
Paul H. Gailus, Mark A. Gannon, Steven F. Gillig
Abstract: A circuit for coupling a signal source producing a signal having a given voltage waveform to a load having two ends, the circuit being composed of: a load voltage control unit connectable between the signal source and one end of the load for producing across the load a voltage corresponding to the signal voltage; and a load current control unit connectable to the load and operable independently of the signal source for producing a current flow through the load sufficient to cause the voltage across the load or the current through the load to have the given waveform.
July 17, 1992
Date of Patent:
March 28, 1995
Zero Impedance Systems
George H. Freuler, Edward J. Collier, David Mazi
Abstract: A circuit for limiting temperature without distortion in audio power amplifiers, comprising a temperature sensor for sensing the temperature in an audio power amplifier, and a variable-gain amplifier connected ahead of the audio power amplifier circuit and having a gain control input connected to the temperature sensor to vary the input signal of the audio amplifier in a linear manner. A linear limitation of the power, and therefore of the temperature, is thus obtained in the audio amplifier without introducing distortion.
Abstract: An antipilferage system is provided with an improved signal processing system to prevent false alarms. This signal processing involves singly or in combination the improvements of a slew rate limited amplifier, which prevents impulse noise from ringing or being stretched by subsequent filters; a gain-controlled amplifier ahead of said slew rate limited amplifier, the gain of the gain-controlled amplifier being reduced as the noise and/or signal exceeds a minimum threshold level; a video detector which controls the gain-controlled amplifier and serves to maintain a minimum signal to noise ratio; a digital smoothing circuit which averages several "frames" of the entire signal such that random noise is averaged to zero while any signals which are synchronized with the modulation are added together; signal processing circuitry for the recognition of incoming signal pulse shape as compared to a predetermined pulse shape, the output of which is a trigger signal to an alarm.
Abstract: A method and apparatus for measuring the small signal gain of an amplifier. Each amplifier responds, in operation, to a small signal input. The small signal input varies substantially linearly over a field time interval. A small bias signal is added to the bias level input of the amplifier during a portion of the field time interval. The output of the amplifier is measured at three or more different times during the field time interval, at least one time when the small bias signal has not been added to the bias level input and at least one time being when the small bias signal has been added to the bias level input. By processing the measured outputs, a signal which is directly proportional to the product of the small bias signal with the small signal gain of the amplifier is obtained.
Abstract: A BTL power amplifier comprises main and inverse amplifier units having the same constitution but producing outputs inverted from each other. A low impedance load is directly connected between the output ports of the main and inverse amplifier units. The present BTL power amplifier further comprises a first operation control circuit which activates only the main amplifier unit after the power switch is turned on, and a second operation control circuit which maintains the output port of the inverse amplifier unit in a floating state for a predetermined period of time after the activation of the main amplifier unit is begun. Thus, the present BTL power amplifier produces no pop noise when the power supply is initiated.
Abstract: An input signal is applied to the inverting input of a class B amplifier and to the input of a limiter circuit. The square wave signal from the limiter is applied to the input of a switching amplifier which drives this amplifier between V and ground at the switching rate established by the input signal; thereby, obtaining a power control signal. The power control signal is applied to one terminal of a load and to the non-inverting input of said class B amplifier. Ignoring the input signal to the amplifier, this switches the output of the class B amplifier between V and ground at the same rate and in phase with the output from the switching amplifier. The gain of the input signal path in the amplifier is such that the input signal will just drive the output between V and ground. The switching action of the power control signal in combination with the input signal then causes the output signal across the load to have the same characteristic as the input signal but with a peak-to-peak amplitude of 2V.
Abstract: A radio transmitter has an output power control circuit including a power amplifier, a directional coupler coupled to the power amplifier, a detector of the forward power of the directional coupler, a generator of a difference voltage between the output voltage of the detector means and a reference voltage. A power regulator varys the output power of the power amplifier in response to the output of the difference voltage. The power applied from the power amplifier through the directional coupler to the detector is controlled by a control signal.The control circuit electrically varies the coupling coefficient of the directional coupler for attenuating the power applied from the directional coupler to the detector means to extend the controllable range of the transmitter output power.
Abstract: A circuit for providing adaptive level control in a sound-recording device. A feed-back signal drives a variable attenuator which controls the input level to the audio amplifier stage. Means are provided for preventing voltage spikes at turn-on from adversely affecting the operation of the attenuator and which provide stable sensitivity control.