Abstract: A phase-locked loop capable of generating a plurality of stable frequncy signals. This loop includes a plurality of voltage controlled oscillators which are sequentially coupled to the output of a phase sensitive detector by a multiplexer. RF switches then sequentially couple, in synchronism with the multiplexer, the oscillator outputs to a programmable divider which, in turn, is coupled to an input of the phase sensitive detector, the other input thereto being coupled to a reference oscillator. The dividing factors for the programmable divider are inputted thereto, in synchronism with the multiplexer, from a memory.

Abstract: An isolation amplifier circuit is described that utilizes a magnetic field in combination with a Hall effect device to isolate input signals and output signals. The input signal is applied to a conducting coil that produces a magnetic field in a Hall effect material through which current is flowing. Because of the Hall effect, terminals on the sides of the Hall effect material can provide a voltage difference. This voltage difference is amplified and applied to a second conducting coil. The second conducting coil is adapted to provide a magnetic field in the opposite direction from the magnetic field produced by the input signal. When the magnetic fields are identical, no difference in current flowing through the two terminals will be present. The output signal of the difference amplifier circuit will be a function of the input signal. According to a second embodiment, apparatus is included for cancelling ambient magnetic fields.

Abstract: A low-distortion transformer-coupled circuit. An amplifier is constructed to have a negative output impedance equal to the resistance of the primary winding of a coupling transformer to which the amplifier is connected thereby cancelling the distortion component produced by the transformer distortion current flowing through the primary winding resistance. The input to the amplifier is thus coupled to the secondary winding of the transformer. A low-frequency feedback circuit is provided between the amplifier output and a non-inverting input thereof. Means is provided for adjusting the negative output impedance of the amplifier to match circuit parameters. Alternatively, the coupling transformer employs two matched primary windings and one secondary winding, and the amplifier is constructed to provide a signal to each primary winding.

Abstract: A circuit for a selective push-pull amplifier having amplifier triple poles of the same polarity which simultaneously produces high efficiency and low nonlinear distortions. The circuit has control electrodes controlled by out-of-phase control voltages and an output inductance having a center tap which produces a magnetic combination of output currents of the amplifier triple poles. The output electrodes of each triple pole is connected to an output inductance through a transformer having three windings. Two oppositely polarity windings connect the output of the triple poles to the output inductance while the third winding is connected to provide a series resonant circuit.

Abstract: A high frequency circuit is arranged to modify a signal, such as a television broadcast signal, prior to high power amplification so as to compensate for distortions introduced by the amplifier. Separate signal paths give independent adjustment of the differential gain, differential phase and linearity of the signal by altering the characteristics of level dependent detectors.

Abstract: A unitary component operating as a low noise amplifier incorporates several other tuning components in conjunction with an FET. By adjusting the tuning components, the overall amplification and impedance characteristics of the unit can be standardized in spite of typical variations in impedance and amplifying characteristics of the FET by itself. The incorporation of such a drop-in module in a microwave circuit, simplifies testing and repair of the remaining portions of the circuit, since the drop-in modules can easily be tested and adjusted for proper operation in a test jig separate from the actual operating circuit.

Abstract: A frequency synthesizer includes frequency reduction means which includes a pulse swallow circuit PS which cancels cycles from the frequency Fo under the control of a rate multiplier RM. To prevent phase jitter at the output of phase comparator PC due to the cancelled cycles, a compensation signal HP is derived from a swallow command signal A and from a multiplying fraction n/x of the rate multiplier. In order to keep the DC level of the signal HP constant, the signal HP is bidirectional with respect to a mid-point voltage level and the total area of the pulses in one direction is the same as the total area of the pulses in the other direction. The invention is applicable to both phase locked loop synthesizers (FIG. 2) and direct synthesizers (FIG. 11).

Abstract: The JFET transistor differential amplifier herein serves as an input stage, as for an electrometer operational amplifier, and exhibits high input impedance and low leakage current. This is achieved by biasing the JFET transistors so as to operate in the ohmic region rather than the saturation region of their characteristic drain current-gate to source voltage curve.

Abstract: The loop uses a phase comparator (PD) designed to compare the phase of a reference signal (F.sub.1) with the phase of a signal generated locally (F.sub.2) and also to make available on a first output (E) a signal expressing the entity of phase shift and on a second output (S) a signal expressing the sign of the phase shift (F.sub.1 leading, or lagging, in respect to F.sub.2). Thanks to the presence of this latter signal (S) it is possible to render the remaining units of the loop particularly simple and economic without having to make use of components that introduce in their turn limits in operational speed, excepting of course those imposed by the type of technology used. This loop is suitable to be conveniently implemented in an integrated manner.

Abstract: A series biasing arrangement for a pair of junction field effect transistors (JFETs), which may be used in RF amplifiers, mixers or oscillators, comprises connecting the JFETs together in series, with the gates of the two JFETs selectively connected to different reference potentials. The first FET is also connected to the DC voltage source. In one embodiment of the invention, two operational amplifiers, whose output leads are connected to the gates of corresponding JFETs have their noninverting input leads connected to selected points on a voltage divider made up of three resistors and their inverting input leads each connected to the source of a corresponding JFET. The drain to source voltage drops across the JFETs are controlled solely by the values of two of the resistors in the three resistor voltage divider. The bias current through the series-connected JFETs can be controlled independently of the drain to source voltage drops across each of the JFETs. The two FETs need not be closely matched.

Abstract: An amplifier switchable between a dual-channel amplifier and a BTL amplifier includes first and second amplifying circuits having a non-inverting input, an inverting input and an output, a first input terminal receiving a first input signal and applying it to the non-inverting input of the first amplifying circuit, a second input terminal receiving a second input signal, a first switch selectively applying a signal to the non-inverting input of the first or second amplifying circuit, a second switch controlling the application of an output from the first amplifying circuit to the inverting input of the second amplifying circuit, a controlling circuit controlling the first and second switches, first through third loads and a third switch controlling the application of an output from the first and second amplifying circuits to the first and second loads, respectively, or to the respective ends of the third load.

Abstract: An electrometer amplifier with automatic zero-error correction in which the input current is switched periodically between two amplifier channels by twin reed switches 2,2', the channel outputs being switched in synchronism (15,15') to a common output 19. Each channel includes a current-to-voltage converter 3,4; 3',4' feeding an amplifier 8,9; 8',9', followed by an integrator and store 11,12,13; 11',12',13' whose output is continuously fed back negatively to the input of this amplifier but whose input is synchronously switched (10,10') into connection with the amplifier output only when that channel is disconnected from the input terminal 1. During the latter period capacitors 13,13' store a voltage corresponding to the zero error in the circuitry preceding amplifiers 8,8', so that the stored value (periodically updated) continues to cancel the zero error when terminal 1 is reconnected to that channel and switch 10,10' reopens.

Abstract: There is disclosed a phase adjusted feedforward error correction system with improved linearity and bandwidth for use in high frequency systems. The feedforward system includes phase and amplitude equalizer circuits which cause a main amplifier output signal to be equal in amplitude and phase with the input signal and a second phase and amplitude equalizer circuit which causes the distortion products generated by the main amplifier to be equal in amplitude and phase with the distortion products from the main amplifier output before subtracting the distortion products from the main amplifier output signal. The phase and amplitude equalizer circuits simplify the construction of the feedforward circuit while maintaining inherent stability over the bandwidth and frequency of operation.

Abstract: An accessory device for use with a metal detector with means to amplify the low, barely audible audio output of the metal detector so that it can be easily heard with further means to dampen louder audio output signals causing those signals to be softer.

Abstract: A problem encountered in the design of preamplifiers of optical receivers, e.g., of so-called transimpedance amplifiers, is to achieve both a wide bandwidth and high sensitivity. The invention solves this problem primarily by a specific implementation and placement of the feedback resistor in the transimpedance amplifier type, and of the load resistor in the high-impedance amplifier type which permit a high resistance value and very low series and shunt capacitances. The resistor consists of a resistive strip (1) and conductive strips (2, 3) deposited on a substrate, the conductive strips extending parallel to the resistive strip and each having one end connected to one end of the resistive strip. To reduce shunt capacitances, the substrate is located at a distance from the metallic amplifier case and from the amplifier board.

Abstract: An active biquadratic notch filter having first integrating circuitry for providing a first integration signal and further having second integrating circuitry responsive to the first integration signal for providing a filter output. The first integrating circuitry includes at least one operational amplifier. The notch filter further includes compensation circuitry for compensating the limitation on notch frequency attenuation resulting from current lag introduced by the at least one operational amplifier of the first integrating circuitry.

Abstract: A multiband local oscillator of a television tuner comprises a common collector transistor amplifier, a capacitive feedback circuit for conditioning the amplifier to oscillate in the wide range of frequencies for VHF broadcast and cable channels and a multiband tuning circuit coupled to the base electrode of the transistor. Bandswitching signals are applied to the multiband tuning circuit to produce tuned circuit configurations for the various frequency bands. When one band is selected, the corresponding bandswitching signal is coupled to the capacitive feedback network to modify it so as to inhibit out-of-band oscillations due to parasitic elements of the tuning circuit.

Abstract: A power source consisting of a low power high frequency oscillator section driving a high power high gain amplifier section. The amplifier section includes one or more SIT's. The dc operating potential is applied to the drain electrode of one of the SIT's and is supplied to the other through a dc path from the source electrode of the one SIT to the drain electrode of the other. Operating potential from the dc biasing network between the gate and source electrodes of an SIT in the amplifier section is conducted through a dc path to a transistor in the oscillator section to provide operating power for the oscillator section. The oscillator output is connected through a high frequency coupling dc blocking path to the amplifier input to provide a drive signal to be amplified and extracted at the amplifier output.

Abstract: A dielectric resonator stabilized oscillator structure and method for adjusting the oscillating characteristics of the oscillator which includes mounting the dielectric resonator to a cover housing member which can be positionally varied to move the resonator in a plane parallel to a semiconductor device and transmission line circuitry comprising the oscillator. The semiconductor device and transmission line circuitry are disposed within a bottom housing assembly to which the cover housing member is fixedly mounted to after adjustment and optimizing of the oscillator characteristics is conducted. The cover member includes openings therethrough which are oversized with respect to corresponding threaded openings in the bottom housing assembly thereby allowing the adjustment of the dielectric resonator by moving the cover member while screws are threaded through the openings thereof into the bottom assembly and also fixedly mounting of the cover member to the bottom assembly.

Abstract: An improvement to a linear power amplifying system is disclosed which maintains the DC balance of the envelope feedback loop under adverse conditions, thereby improving the accuracy of the system. The improvement is realized through the addition of two differential amplifier stages to the feedback loop. A first differential amplifier 103 is added to the balanced outputs of the synchronous envelope detector 102, which is comprised of an active balanced modulator/demodulator device, to correct for the common-mode DC drift of the detector. An auxiliary feedback loop, comprised of a second differential amplifier 104 and a low-pass filter, compares the average DC value of the envelope error signal to a system reference voltage V.sub.R, and produces a loop gain error signal which corrects for variations in envelope feedback loop gain. The improvement provides envelope modulation transmitters with a substantial reduction in adjacent-channel interference and lower on-channel distortion.