Abstract: An electronic microwave calibration device provides an electronic load connected to each of two ports of a vector network analyzer. The load comprises a plurality of PIN diodes interconnected by transmission line. Each of the diodes are biased to generate different loads or conditions at each of the two ports. A control computer controls the biasing of diodes according to a predetermined procedure and compares impedance values measured at each of the two ports by the network analyzer to known values stored by the control computer. The control computer thereby derives calibration coefficients that are stored in the network analyzer and used by the network analyzer in performing further measurements.

Abstract: A frequency adjustment method for an RF bandpass filter, especially a combiner filter, wherein the center frequency of the passband of the RF bandpass filter is adjusted in response to the RF power reflected from the input of the bandpass filter or passed through the bandpass filter. A sample signal proportional to the RF power reflected from the input of the bandpass filter or passed through the bandpass filter is mixed with a signal of substantially the transmitting frequency. The mixing result is lowpass-filtered and the bandpass filter is adjusted in response to the lowpass-filtered mixing result.

Abstract: A method of controlling the time constant of a filter for use in a radio receiver which receives a signal, transmitted from a transmitting station at a predetermined period, intermittently at the predetermined period and demodulates and delivers the received signal, a filter circuit having the time constant control function based on the method, and a radio receiver having the filter circuit. Preferably, the filter has its time constant switchable stepwise and specifically, parallel connection of capacitors or shortcircuiting of resistors is controlled by turning on/off switches.

Abstract: An apparatus and method for varying coupling of a radio frequency (RF) signal (408). This is advantageously used for increasing the dynamic range of a power detector (406) in an automatic power level control loop (403) of a transmission unit (404), while maintaining transmission unit efficiency at higher power levels. This is accomplished by selecting between a first operating mode of the RF coupler (405) having strong coupling, responsive to a first predetermined power level, such that the RF coupler (405) produces a first coupled RF signal (509) responsive to the RF signal (408) and a second operating mode of the RF coupler (405) having weak coupling, responsive to a second predetermined power level, such that the RF coupler (405) produces a second coupled RF signal (510) responsive to the RF signal (408).

Abstract: This invention provides a method and circuit for separating a signal of interest from a composite signal including a signal of interest and an angle modulated interfering signal, in which an in-phase component of a reference signal representative of a composite signal is mixed with the composite signal to produce a first compound signal, selected components from the first compound signal are removed to produce a first filtered signal, and the in-phase component of the reference signal is mixed with the first filtered signal to produce a second compound signal. Similarly, a quadrature component of the reference signal is mixed with the composite signal to produce a third compound signal, selected components from the third compound signal are removed to produce a second filtered signal, and the quadrature component of the reference signal is mixed with the second filtered signal to produce a fourth compound signal.

Abstract: An automatic tracking notch filter system tracks a large-magnitude narrow band signal through frequency effectively eliminating it. A frequency variable notch filter is responsive to a control input at which is applied a small amplitude AC dither signal. The resulting fluctuation in frequency of the notch filter causes corresponding fluctuations in the magnitude of the notch filter output. The output signal is rectified and band pass filtered around the dither frequency before being demodulated with the dither signal to provide a DC error signal indicating the magnitude and direction in frequency of the filter misalignment. The error signal is integrated and input to the control input of the notch filter with the dither signal such that the notch filter tracks the narrow band signal in response to the feedback signal provided at its control input.

Abstract: In order to efficiently and steadily remove a frequency-fluctuating interference wave, for instance, a leakage wave of a household electronic oven, intermixed into a received wave for communication, adaptively to the frequency deviation and the frequency fluctuation of the interference wave, a rejection band component included in the received wave applied onto a circulator an output terminal of which is connected with a variable band rejection filter is reflected from the output terminal on which impedance mismatch is caused by zero-impedance presented by the rejection filter on the basis of absorption of input wave and applied to a detector through the circulator again, in response to a detection output of which a so-called mountaineering control is effected on the variable band rejection filter for shifting the rejection band, so as to maximize the detection output of the detector adaptively to the frequency deviation and the frequency fluctuation of the interference wave.

Abstract: The radio receiver of the present invention detects the presence of adjacent channel interference in either the lower adjacent channel or the upper adjacent channel and shifts the received signals to remove the adjacent channel interference from the intermediate frequency passband, but only if the other adjacent channel is clear. A maximum amount of the desired signal is retained so that modulation distortion is low. Frequency limits for shifting of the desired signals prevent undesirable amounts of phase distortion from being introduced into the audio signal.

Abstract: A Q multiplier circuit which is automatically feedback stabilized through the use of phase and gain control loops and thereby adapted for use as an amplifier and filter. In a typical embodiment, a variable gain amplifier and band pass filter are provided in a forward signal path while a phase shifter is provided in a feedback signal path. The output of the circuit is sampled and compared to a fixed reference in order to generate a gain control signal for application to the variable gain amplifier. The input signal on the forward signal path is sampled along with the signal on the feedback signal path and the phases of these samples are compared in order to generate a phase control signal for application to the phase shifter. The variable gain amplifier is controlled to maintain a predetermined power output level while the phase shifter is controlled to maintain positive feed back.

Abstract: An on-chip apparatus and method are provided for automatically tuning a continuous time filter in which a single filter selectively filters an information signal or, when tuning is desired, an unfiltered reference signal. During tuning, a controller determines the amplitudes of the unfiltered and filtered reference signals and their ratio. From the ratio, the controller ascertains a corresponding center or tuned frequency of the filter. If the ascertained frequency does not substantially equal a desired tuned frequency, the controller directs a bias controller to adjust the bias of the filter until the tuned frequency is substantially equal to the desired tuned frequency.

Abstract: An autotuning combiner particularly for use in combining signals for radio telephony transmission. The combiner has a series of filter cavities each with an adjuster for fine-tuning the cavity to an input carrier signal. The combiner cavities are stabilized from positional drift in the absence of a carrier signal by means of a mechanical brake which holds the adjuster or a pilot signal generator which simulates the absent carrier signal.

Abstract: An auto-tuned apparatus for a band-pass filter, wherein, the generated reference signals having the given frequency to be set are mixed with signals to be outputted from the band-pass filter when the reference signals have been inputted to the band-pass filter so as to multiply them for outputting the signals of the multiplied results, the signals of the direct current component from the signals of the multiplied results to be outputted are filtered, and the band-pass filter is controlled so that the center frequencies of the band-pass filter may agree with the frequencies of the reference signal in accordance with the signal of the direct current component to be outputted, whereby the center frequency of the band-pass filter can be adjusted automatically to the desired set value with simple circuit construction and precision better than in the conventional embodiment.

Abstract: An automatic filter adjusting apparatus including an adjustable filter having an input and an output, a reference signal generator for providing a reference signal to the filter, a generator for generating an adjusting signal used to adjust the filter, a comparator for comparing the output of the filter to a reference level and a controller for controlling the adjusting signal generator.

Abstract: In order to efficiently and steadily remove a frequency-fluctuating interference wave, for instance, a leakage wave of a household electronic oven, intermixed into a received wave for communication, adaptively to the frequency deviation and the frequency fluctuation of the interference wave, a rejection band component included in the received wave applied onto a circulator, an output terminal of which is connected with a variable band rejection filter, is reflected from the output terminal on which impedance mismatch is caused by zero-impedance presented by the rejection filter on the basis of absorption of the input wave and applied to a detector through the circulator again, in response to a detection output of which a so-called peak-keeping control is effected on the variable band rejection filter for shifting the rejection band, so as to maximize the detection output of the detector adaptively to the frequency deviation and the frequency fluctuation of the interference wave.

Abstract: A power amplifier arrangement includes a power divider for dividing the signal to be amplified into equal-amplitude components. Each component is amplified by a signal amplifying path. The amplified signals are applied to a phase-sensitive power combiner. The combined signal appears at the sum port and a phase-related difference signal appears at a difference port of the combiner. The difference signal is processed to produce a control signal for controlling the relative phases of the signals passing through the signal amplifying paths.

Abstract: A cut-off frequency automatic adjusting filter includes a plurality of filters, one of them being a reference filter, and a feedback circuit for the reference filter. The feedback circuit is formed by a subtracter, a full-wave rectifier, an integrator and an error amplifier. A square wave signal is inputted to the reference filter as a reference signal instead of a sine wave signal in the conventional filter. The feedback circuit generates an electrical signal which causes the cut-off frequency of the reference filter and another filter to be constant.

Abstract: Transducer circuit, including a tuning inductor for removing the reactive mponent from the signal of an acoustic transducer; the inductance varies with frequency, thus permitting the transducer-tuning inductor to present a non-reactive load to the an amplifier over a broad operating frequency.

Abstract: The center frequency of each of the analog filters with different selectivities each other installed in an automatic adjusting circuit is automatically adjusted in accordance with a bias input signal which is generated by the phases detectors respectively associated with the analog filters in accordance with a frequency difference, so as to be equal to the reference frequency of an input signal applied to the two analog filters. The bias input signal is fed to an analog filter to be controlled, which is formed on the same chip as that of the above two filters. A coarse adjustment is based on the output signal of the phase detector associated with the analog filter with a low selectivity. A fine adjustment is based on the output signal of the phase detector associated with the analog filter with a high selectivity.

Abstract: In a circuit arrangement for matching the resonant frequency of an antenna resonant circuit (18) to the output circuit of a transmitter output stage (10), the antenna resonant circuit (18) is coupled via a reactance to the transmitter output stage (10). By means of a current sensor (16), the supply direct current of the transmitter output stage (10) is detected. The value of a tuning component (26), lying in the antenna resonant circuit (18), can be changed by a control signal; the tuning component is a governing factor for the resonance frequency of the antenna resonant circuit (18). A comparator and control unit (36)repeatedly samples the value of the supply direct current detected by the current sensor (16). In dependence upon the result of a comparison with a sequential previously sampled value, it applies th control signal to the tuning component (26) to obtain a maximization of the supply direct current detected.

Abstract: The balance of the volumes in right and left channels in a stereo play back system is controlled. The amount of attenuation of an attenuator provided in each channel is controlled. When the levels of right and left stereo signals are judged to be approximately the same, an oscillator is permitted to oscillate and the pulses from the oscillator are counted by a counter. In accordance with a voltage signal which corresponds to the level ratio of the right and left stereo signals, whether the counter must count upwards or downwards is determined. The balance is controlled in accordance with the amount of attenuation of each attenuator which is determined in accordance with the decoded count value. The completion of the control is detected when the level ratio of the right and left stereo signals alternately change after they become substantially equal, and the control is automatically finished.

Abstract: A three terminal compensation network for frequency dependent attenuation has a control terminal, an input terminal, and an output terminal. The network is particularly useful for an off-premises CATV system for slope compensation of a broadband television signal. The control terminal is supplied with a voltage indicative of the amount and direction of the slope in the actual television signal. The voltage oppositely biases a set of diodes which are used as controlled resistances in a pair of tuned circuits in the network. One series tuned circuit provides for varying degrees of negative slope compensation and a parallel tuned circuit provides for varying degrees of positive slope compensation. The network elements are connected in a modified bridge T configuration such that the characteristic impedance of the CATV system (75 ohms) can be approximately matched for the input and output of the broadband television signal.

Abstract: An apparatus for frequency band reduction of a voice signal having an upper and lower band limit including a voice signal input, a clipping circuit for clipping the positive and negative peaks of the voice signal connected to the voice signal input. A bandpass filter is connected to the clipping circuit for rejecting harmonics created by the clipping circuit. A low and high end roll off filter device is provided for producing a given decibel/octave frequency roll off at the lower band limit; and the geometric mean value of the upper and lower band limit falls within a given lower and a given upper frequency range.

Abstract: A tunable bandpass filter system and filtering method wherein the bandwidth of a tunable bandpass filter is adjusted as a function of the fundamental frequency of an input signal. Either a constant bandwidth or a constant quality factor tunable bandpass filter may be used. The center frequency of the tunable bandpass filter is adjusted in direct proportion to the product of the fundamental frequency and the number of a selected harmonic thereof. In the case of a constant bandwidth filter the bandwidth is adjusted in direct proportion to the quotient of the fundamental frequency divided by a selected filter quality factor. In the case of a constant quality factor filter, the bandwidth is indirectly controlled by adjusting the center frequency while adjusting the quality factor in inverse proportion to the harmonic number. The output amplitude of the filter is measured to determine the amount of distortion in the input signal. The fundamental frequency may be determined by measuring the input signal.

Abstract: A bandpass filter is disclosed which may be used in a superheterodyne receiver in front of the first mixer. The bandpass filter provides a narrow front end filter which is tuned automatically as the local oscillator frequency is changed. In the present exemplary embodiment, a series tuned reflective notch filter is coupled to a node of a balanced resistive bridge in such a manner that the tuned circuit presents a short circuit to the node at the filter's resonant frequency to thereby assure a maximum transfer of signal from the input to the output of the circuit at a desired frequency. At all other frequencies, the series tuned reflective notch filter will present essentially an open circuit across the node of the resistive bridge so that the node is balanced and no transmission occurs. The inclusion of the series reflective notch filter thereby produces a bandpass characteristic from the circuit input to output.

Abstract: Devices and methods for selectively reducing an electromagnetic or acoustic interference present in a transmission line by an active adaptive means, are described. For the electromagnetic interference, the transmission line may include a waveguide carrying a desired signal along with an undesired interference, the objective of the invention being to reduce the interference selectively at the output of the transmission line without affecting the desired signal substantially. Similarly, for an acoustic interference, the transmission line may include an exhaust pipe of an auto or Diesel engine carrying an undesired acoustic interference or noise, the objective of the invention being to reduce this noise at the output of the pipe.

Abstract: In an ALC circuit for automatically performing an amplitude compression control operation according to the output level of a low frequency amplifier circuit, the output level of the amplifier circuit is subjected to amplitude compression according to the level of a control signal which is outputted in correspondence to the output level of the amplifier circuit. The differentiation time constant of a differentiating circuit (or cutoff frequency of a high pass filter) provided on the output side of the amplifier circuit is controlled according to the level of the control signal to control the cutoff frequency for the frequency band subjected to amplitude compression.

Abstract: An automatic gain control (AGC) circuit for microwave applications is disclosed. The AGC circuit includes a power divider for splitting the signal to be controlled into two signal paths. In one signal path the signal is passed through a GaAs monolithic attenuator. In the other signal path, an RF detector provides a detector output signal to a shaper circuit, which responds to the detector signal to provide control signals to the attenuator. Thus, the AGC circuit employs a feed forward technique for gain control, to provide fast settling times for the circuit.

Abstract: A notch filter for reducing clock signal feedthrough effects in an acoustic charge transport (ACT) device. This notch filter is included on the same substrate as an ACT device. This notch filter may be employed to remove clock signals which have greater voltage than the data signals in an ACT device. This notch filter may be employed either at the input or the output of the ACT device. The notch filter includes a bridge connection of surface acoustic wave transducers and RC networks on opposite sides of the bridge configuration. Each side of the bridge is balanced so that at the notch filter frequency, the voltage output by each side of the bridge is one-half of the input voltage and in phase. These voltages produced by each half of the bridge are differenced and a zero output voltage is produced at approximately a notch or center frequency.

Abstract: The filter disclosed has a feedback circuit to stabilize the matching frequency f.sub.o at any instant, in acting on the bias current and voltage of the variable capacitance diodes of the filter, when interfering signals have a frequency located in the pass-band of this filter.

Abstract: A tunable bandpass filter for radio frequency energy with a phase-locked loop for tracking an input signal and to control the filter to keep the center frequency of the passband coincident with the frequency of the input signal is shown. Using a Yttrium Iron Garnet (YIG) filter as a frequency determining element and as a passive dispersive reference element for a frequency discriminator, the bandpass filter uses the output signal of the discriminator to form a fine tuning signal to control the center frequency of the passband of the YIG filter.

Abstract: A tuning circuit is provided for increasing the power transfer between first and second electrically coupled utilization circuits while controlling the effective source reflection coefficient thereby increasing the power available to the latter wherein the input signal provided at the output of the first utilization circuit is reflected back reducing the power available at the input of the second utilization circuit. The input signal is applied to the first input of the power combiner while a feedback signal proportional to the power loss between the first and second utilization circuits is applied to the second input of the power combiner. The output of the power combiner is increased by the feedback signal for compensating the power loss of the input signal such that the power available to the second utilization circuit is increased.

Abstract: A MMIC variable slope gain-equalizer varies the conductance of depletion mode Schottky gate FETs to controllably insert frequency dependent resonant members in a modified bridged-T configuration. Resistors connected from circuit input port to output port define the arms of the "T" and a T-node to which a first frequency dependent resonant member is connected in series with a first FET. A second FET and a second frequency dependent resonant member are each connected in series between the circuit ports, bridging the T. Preferably a third frequency dependent resonant member is series connected with the second frequency dependent member. Each frequency dependent resonant member resonates at about the highest frequency of interest, typically about 18 GHz. When the first FET is on and the second FET off, maximum attenuation at lower frequencies is inserted into the circuit, and when the first FET is off and the second FET on, minimum attenuation is inserted at lower frequencies.

Abstract: A filter circuit (2) is automatically tuned so that the positions of the poles and zeros of its frequency response characteristic are maintained in substantially fixed ratios to an input frequency (f.sub.r). The arrangement comprises a frequency discriminator (1) having its output (5) coupled to a controllable element (8) of a resonant circuit included therein, so that the resonant frequency of the resonant circuit is maintained equal to the input frequency. The output 5 also controls a counterpart (13) to element (8), which counterpart is included in an auxiliary circuit (3). The filter circuit is tuned by controlling an element (10) included therein, which element also has a counterpart element (14) included in the auxiliary circuit, both of these elements (10,14) being controlled by the auxiliary circuit output signal.

Abstract: An electronic circuit utilizing a parallel tuned resonant circuit and time variant frequency multiplying to eliminate undesired response changes of the tuned circuit due to temperature is disclosed. The electronic circuit illustrated permits accurate measuring of the change of inductance in a parallel tuned circuit where such change of inductance is due to an input parameter to be measured. The inductive component being measured may be located in environmental conditions which include a large variation in ambient temperature. While normally such wide temperature variations may substantially interfere with the measurement of the value of the inductance in question, the disclosed invention provides for compensation of such undesired changes so that the actual change of the inductance can be monitored without interference.

Abstract: A noise reduction system compresses an input signal at a constant ratio in response to a control signal derived from the compressed signal. Added to the derived control signal is a counterfeit control signal which causes the compressor to mistrack when the compressed signal falls below a preselected threshold level. Thus, low level compressor output signals are increasingly deemphasized. A constant counterfeit control signal produces a logarithmic decrease in compressor output signal levels below the threshold point. The resulting compressed signal is used to enhance system noise reduction. The input signal is fed to a filter having a variable bandwidth controlled by a signal derived from the compressed signal and responsive to compressed signal frequency and amplitude so that the filter is desensitized to input signal amplitude changes. A multistage filter control signal arrangement may be employed to provide variable cutoffs in more than one bandwidth.

Abstract: A notch filter is provided with an ancillary circuit including a non-inverting amplifier and a coupling which enables the filter to form part of an oscillatory loop of which the frequency of oscillation corresponds to the frequency of maximum rejection by the notch filter. Measurement of that frequency facilitates the tuning of the notch filter, which includes capacitors constituted by varactor diodes. The gain of the ancillary circuit may be adjusted to change its mode of operation from oscillation to that of a tuned amplifier so that a sweep of the center frequency of the notch filter through a range of interest facilitates a search for an unknown interfering frequency and the simultaneous tuning of the notch filter to reject that interference.

Abstract: A combining and filter circuit is provided to connect the acquisition circuit and phase detector circuit to the voltage controlled oscillator in a phase locked loop. The combining and filter circuit includes twin-T filters for removing reference frequency signals. An output circuit includes series resistors and capacitors, and reverse poled Schottky diodes which provide rapidly changing acquisition signals that are relatively noise free.

Abstract: A distortion-corrector which comprises a filter of the low-pass type, of the .pi. or T configuration, and two diodes, in parallel opposition, disposed between the input and output of the filter. This corrector compensates amplitude-and-phase- distortions of the tube associated with the corrector, over a given operational frequency-band of the tube which is below the cut-off frequency of the filter, by compressing weak signals, for which no diode conducts, with respect to strong signals, for which there is at least a start of conduction of one of the diodes and by producing a phase-lead which increases with the input power of the tube.

Abstract: This invention relates to a flexible notch filter for use in a servo system to eliminate natural mechanical resonance. The filter is an improved "twin-T" type where the "in-phase" output of the filter is fed back into the filter. Varying the feedback varies the bandwidth of the filter. The improved filter further provides for attenuation control in addition to control of the center frequency of the filter. The advantage of this filter over prior art designs is that one filter may be manufactured and adapted to be used in many servo systems since the filter can be easily adjusted to effectively eliminate the natural resonating frequency of the machine in addition to reducing phase lag at frequencies below the center frequency of the notch filter.