Abstract: A variable equalizer adapted to be fabricated in an integrated circuit structure and having improved compensation characteristics comprises a parallel connection of two circuits, one including a series connection of a first impedance circuit (impedance: Zy) and an input A.C. signal source circuit having a voltage v.sub.i, the other comprising a series connection of a second impedance circuit (impedance: Z.sub.x) and an A.C. signal source circuit having a voltage amplitude v.sub.z which is equal to v.sub.i (K/Z.sub.y).sup.2, where K is a constant, and the second impedance circuit, consists of a variable resistor.

Abstract: Amplitude and delay equalization of a surface acoustic wave filter used in the output of the amplitude modulated stage of a TV transmitter is disclosed. The equalization is provided by designing the filter to produce an amplitude ripple maximum or minimum at the visual carrier frequency. The video applied to the amplitude modulator is processed by a transversal equalizer such that the video is preprocessed to have an inverse amplitude and phase ripple with that produced by surface acoustic wave filter.

Abstract: The input wave guides are oriented towards a perpendicular output wave gu with a semi-reflecting quarter-wave plane reflector disposed at 45.degree. to two progressive reflectors which cause increasing delay with frequency and which are disposed in the line of the input and output wave guides.

Abstract: Digital transversal filter for realizing a lowpass filter with a cut-off frequency f.sub.g and an impulse response h.sub.1 (i), a lowpass filter having a cut-off frequency 2f.sub.g which has a transfer characteristic which is in phase with the first-mentioned lowpass filter, as well as a lowpass filter with a quadrature transfer characteristic of the in-phase filter.

Abstract: A cable equalization resonant amplifier circuit for compensating for the signal-attenuation effects of a coaxial cable connected with the amplifier circuit and having a length of up to one-half mile. The gain of the amplifier circuit is matched with the attenuation characteristics of the coaxial cable over a wide range of frequencies by employing an LC resonant circuit with a Q of approximately 1 in the emitter circuit of an amplifying transistor. The gain for the amplifier circuit is established to match the attenuation characteristics of the coaxial cable at low frequencies by an RC circuit coupled with the amplifying transistor and the LC resonant circuit. The maximum or peak desired value of gain for the amplifier circuit at the resonant frequency of the LC resonant circuit is established by a resistor connected in series with the LC resonant circuit and a resistor in the collector circuit of the amplifying transistor.

Abstract: In order to realize a precision variable equalizer of little errors by a simple circuit arrangement, a plurality of variable transmission circuits having variable transfer coefficients are connected in series between input and output terminals, and feed-back and feed-forward are applied from input and output sides of the respective variable transmission circuits to input and output portions of the variable equalizer through transmission networks having specified transfer characteristics.

Abstract: A signal to be filtered is subjected to a known filter function a sufficient plurality of times and with appropriate processing to produce in a plot of the total filtering response versus the response of one such function at least one inflection in a portion of the plot corresponding to a transition band between a passband and a stopband of the filter function. Various embodiments of the overall filtering function are shown which are applicable to both recursive and nonrecursive filters and to filters having either single or multiple sets of passband and stopband combinations per filter function.

Abstract: An equalizer in which an input signal is double differentiated without introducing phase shift. First and second differentiating circuits are provided at the input electrode and one of the output electrodes of a transistor. A further circuit is provided at the other transistor output electrode, the circuit having the same time constant as the time constant of the first differentiating circuit. Low pass filters and noise suppression may be included in embodiments particularly useful in video and audio recording and reproducing systems.

Abstract: In an automatic equalizer for regenerating a received digital signal, comprising a delay element train with a plurality of taps, a coefficient matrix circuit and a group of variable coefficient units, the structure of said coefficient matrix circuit being considerably simplified by introducing a simple adder and/or subtractor at the input and/or the output of said coefficient matrix circuit.

Abstract: A Bode equalizer which has as one active element thereof a high-gain, differential-input amplifier and which has as a second active element a variable negative resistance, the equalizer circuit being controlled by a resistance arrangement which effectively comprises a series-connected, fixed resistor and the variable negative resistance.

Abstract: Equalization apparatus for a communication system transmitting through a time or frequency spread medium. The message to be transmitted is partitioned and transmitted in burst or frame by frame form. Each frame comprises the message (unknown at the receiver) followed by a test signal known at the receiver. Time gaps are provided between the message and test signals to avoid overlapping of the received message and test signals due to time-spreading. The received mutilated signals are processed in the frequency domain to obtain a reconstituted version of the transmitted message in the frequency domain. This is re-transformed into the time domain so that the reconstituted message available at the receiver is a close replica of the message which was originally available only at the transmitter.

Abstract: A corrective network for obtaining a desired overall frequency response comprises a plurality of tunable, non-active resonant circuit stages, each connected with a source and operative for modifying the frequency response over a respective portion of the frequency spectrum. Each resonant stage comprises a variable differential capacitor having a rotor plate terminal and two stator plate terminals. Each stage further includes a series circuit branch constituted of a resistor and an inductor which has one end which is connected to the respective rotor terminal of each stage. The network further includes a common terminal at which the other ends of the series circuit branches are all connected. The source may be a transformer having a tap intermediate its end terminals, and an output impedance is located between the common terminal and the tap of the transformer. The stator plate terminals of at least some of the stages are connected to respective ones of the end terminals of the source.

Abstract: A method for determining the initial values of the coefficients of a transversal equalizer for a synchronous data transmission system, wherein a training sequence is transmitted to allow the equalizer coefficients to be adjusted to optimum initial values. According to the method, a sequence (v.sub.i) of L elements v.sub.i, having a periodic autocorrelation function, only the first coefficient of which is not zero, is derived from a periodic binary pseudo-random sequence (u.sub.i) of L binary elements u.sub.i having a periodic autocorrelation function, the first coefficient of which is equal to L and each of the other coefficients are equal to -1. Then, the sequence (v.sub.i) is transmitted through the transmission channel and the initial values of the equalizer coefficients are derived from the received sequence.

Abstract: A technique of reducing "crosstalk" in transmission lines for time multiplex pulse communication, by insertion of artificial compensating networks having an impedance varying with frequency in opposite sense as compared with the natural impedance of the line. The values of the elements of the network are determined by transmitting a pulse over the line and determining the distortion to that pulse.

Abstract: A compensating circuit has a frequency response curve into which can be introduced elevations or depressions of selected breadth at selected frequencies. The compensating circuit includes a plurality of tunable circuit stages associated with different frequency ranges. Each tunable circuit stage includes a resistor and an inductor connected in series with each other and to the rotor terminal of a differential capacitor having two stator terminals. The first stator terminals of the differential capacitors are connected to the first winding or windings of one or more differential transformers, while the second stator terminals of the differential capacitors are connected to the second winding or windings of the one or more differential transformers. The voltage induced across the one or more differential transformers is then employed to supplement the voltage which is being transmitted to the output resistor of the compensating circuit by the input transformer of the compensating circuit.

Abstract: A signal processing means and method of adaptively filtering input signals received at a terminal means in which the input signals include pulse signals and noise, with the pulse signals occurring at unknown times and having unknown durations, which includes signal filtering means having a first input for receiving signals derived from the terminal means, a second input and an output, the signal filtering means having a controllable filter characteristic for passing signals from its first input to its output responsive to signals received at its second input, and a signal analyzing means having an input receiving signals derived from said terminal means and an output delivering signals which are responsive to signals received at its input, to the second input of said signal filtering means for controlling its filter characteristic, whereby the output of the signal filtering means delivers signals corresponding to the pulse signals of the input signals to said terminal means while minimizing delivery of noise

Abstract: Attenuation equalizer in the circuit of an adjustable four-terminal network for correcting the frequency-related attenuation curve of cables including a bridged T circuit containing ohmic resistances and having two fixed ohmic series resistance, preferably of equal resistance value, bridged by a bridging impedance, the bridging impedance being a series-resonant circuit having an inductance, a condenser and a variable parallel resistance wherein the shunt impedance is a parallel-resonant circuit having an inductance, a condenser and a variable series resistance, the latter being adjustable by means of a common traversing device.

Abstract: A low loss corrective network for obtaining a desired overall frequency response comprises a plurality of tunable resonant circuit stages which are operative for modifying the frequency response over respective portions of the frequency spectrum. Each resonant stage comprises a variable differential capacitor having two stator plate input terminals and a rotor plate output terminal. Each stator plate input terminal is connected to respective end terminals of a source. A single voltage divider common to all of the stages has two end terminals which are connected with the source and which are also commonly connected with all of the respective stator plate input terminals of the individual stages, and a tap point located intermediate the end terminals of the divider which is commonly connected with all of the respective rotor plate output terminals of the individual stages. Moreover, matching resistors and inductors are employed to compensate for the capacitive loading presented by the differential capacitors.

Abstract: A video processing circuit features direct current coupled circuits. This reduces streaking errors and lowers the power dissipation required.

Abstract: A system equalizer and a method of equalization employed in a repeatered submarine cable system, in which automatic gain controlled (AGC) submerged repeaters are employed to compensate for fluctuations of the cable loss caused by the temperature fluctuations in the surrounding environment of the repeatered submarine cable system. In a terminal equipment connected to the repeatered submarine cable system, the seasonal misalignment of the repeatered cable system is equalized by a switchable equalizer having a loss-frequency characteristic corresponding to the total of compensation errors in the AGC submerged repeaters. Short-term level fluctuations of the repeatered cable system are compensated by an automatic equalizer, which has a loss-frequency characteristic proportional to the square root of frequency f and is controlled by the level of a pilot signal transmitted through the repeatered submarine cable system. An unknown fixed deviation is finally equalized by a second adjustable equalizer.

Abstract: In a system employing half-span preemphasis of transmitted signals on a cable pair telephone line, equalization is accomplished in a circuit arrangement including first and second complementary constant-resistance networks having the input impedances thereof in the emitter and collector circuits, respectively, of a common emitter amplifier. These impedances control the feedback and gain of the amplifier such that their effects are additive in a particular manner in the collector-output circuit thereof. The terminating resistances of the networks are the resistances produced by a pair of differentially controlled thermistors. A DC error signal that is proportional to line length controls the current driving the thermistors and thus the resistances thereof. When the circuit arrangement is at half-span spacing, a difference circuit causes the terminating resistances of the thermistors to be the same values, which make the impedance characteristics of the networks such that the net gain of the amplifier is flat.

Abstract: An equalizer having improved amplitude characteristics and phase characteristics of more than several hundred MHz has been found by using a four port directional coupler. The equalizer consists of coupled lines, and two far end ports of the directional coupler are grounded through two resistances R.sub.1, respectively; while interconnecting the two far end ports through a resistance r, an input port is formed at one of the near end ports of the directional coupler, and an output port is formed at the other end thereof, said resistances substantially satisfying the relation ofG.sub.1 (G.sub.1 +2g)=G.sub.0.sup.2 Z.sub.0o Z.sub.0e =R.sub.0.sup.2where, G.sub.1 =1/R.sub.1,g=1/r,G.sub.0 =1/R.sub.0, R.sub.0 being resistance of a power source and a load, Z.sub.Oo being the odd mode impedance of a coupled line, and Z.sub.0e being the even mode impedance of the same.

Abstract: An equalizer for partial response signals is described which is constituted by a shift register and an analog adder, from the output of which a corrected signal is produced. Two of the switching stages forming the shift register have their outputs connected to inputs of an additional analog adder, and one of these shift register stage outputs is connected to the analog adder over an adjustable amplifier. The output of the additional analog adder is connected to a correlator, the value of the output signal of which controls the gain of the adjustable amplifier.

Abstract: This invention concerns gyrator circuits, and particularly gyrator circuits used in filters. The gyrator network contains two differential input operational amplifiers and an input network, some of the elements of which are variable to enable the Q, the bandwidth and the resonant frequency to be adjusted in such a way that previously adjusted parameters are not changed. The circuit may have three configurations according to the position of a pair of ganged switches, alternatively the switches may be replaced by fixed links.

Abstract: A two-path equalizer system interposable in a telephone line carrying supervisory signals whose frequencies lie below a 3 KHz limit and data signals whose frequencies primarily lie above this limit. The system normally operates in a first path mode with respect to incoming supervisory signals, the gain in the first path being preset to a degree depending on line losses, whereby the levels of supervisory signals emerging from the output of the system are at their nominal telephone line levels. An automatic path selector is provided which is responsive only to data signal frequencies and acts to switch-over the system and render it operative in a second path mode in which incoming data signals are subjected to automatic gain control and appear at the output at their maximum line level despite variations in input level.

Abstract: An inductorless variable equalizer comprises input and output terminals. A first transmission network is situated in the forward path between the input and output terminals and has a variable transfer coefficient; second and third transmission networks are situated in the feedback and feedforward paths, respectively, between the input and output terminals. Each of these networks has a fixed transfer coefficient and the transfer coefficients of the feedback and feedforward networks having polarities opposite each other.

Abstract: If a time domain equalizer with capacitive-resistive voltage dividers for adjusting the level of the individual time-delayed partial signals as commonly employed for high frequencies is to be used to equalize broad communication bands, the noise requirements for the lower communication band cannot be satisfied because of the frequency response of the voltage dividers. This effect is reduced by adding to the signal to be corrected, besides the signals delayed by n..tau., at least one signal delayed by .tau./m.

Abstract: A line device for transmission lines having coaxial cables for the transmission of signals, in particular digital signals or analog signals, employs an input equalizer in the form of a line section connected in parallel or in series to the transmission path, a first switch or dividing network for dividing the transmission path into a communications transmission path and a long distance current supply path, a regenerator in the communication transmission path, a series circuit connected in the long distance supply path including a first low pass filter, an element for producing a voltage drop for the current supply of the regenerator and a second low pass filter. A second switch or dividing network rejoins the communications and long distance supply paths and an output equalizer in the form of an additional line section is connected in parallel to the transmission path or in series with the transmission path.

Abstract: A non-recursive digital filter is disclosed, composed of a cascaded plurality of basic sections, each of which is characterized by coefficient values of integer powers of two's. No hardware multipliers are required in the filter and the operating speed is several times faster than other filters which utilize multipliers.

Abstract: Equalizing system arranged for pulse transmission, adaptive equalization being achieved without the use of an additional periodic adjusting pulse pattern. For this purpose in a control voltage generator the sub-bands and the associated additional sub-bands of an equalized pulse signal processed by the phase and amplitude control circuits are used after pulse regeneration directly as a local reference signal and an adjusting signal respectively. The sub-bands and additional sub-bands are applied to the cascade connection of a comparator and a mean-value device for generating the control voltage which controls the phase and amplitude control circuits in a feedback mode.

Abstract: A linear filter network to provide improved distortion characteristics of a demodulated FM signal by direct synthesis of the linear amplitude transfer characteristic.

Abstract: An adaptive feedforward transversal equalizer acting jointly with a data decision-directed demodulating carrier recovery system to achieve substantially jitter-free passband equalization of a suppressed-carrier coherent data signal without the use of pilot tones is improved by adding a feedback transversal filter section operating on past demodulated data symbols. The weighted output of the feedback section is subtracted from the demodulated output output of the feedforward section to provide signals from which data decisions are made and common error signals are derived. Tap-gain coefficients for both feedforward and feedback filter sections and phase angle for the demodulating carrier recovery system are adaptively updated in accordance with the common error signal. Severe frequency offset and phase jitter are simultaneously compensated.

Abstract: A variable delay equalizer comprises two directional couplers, each having a pair of input terminals and a pair of output terminals. A pair of variable phase shifters are inserted respectively between the output terminals of the first coupler and the input terminals of the second coupler. A third variable phase shifter is connected between the second output terminal of the second coupler and the second input terminal of the first coupler. This equalizer makes it possible to shift the peak delay frequency as well as to change the value of the peak delay itself.

Abstract: A sample data filter using a delta modulator to feed a shift register of which selected outputs are pulsewidth weighted. Each of the coefficient multipliers include a flip-flop fed by one of the taps of the shift register and triggered by a clock. A synchronous counter, common to each of the multipliers, is fed to a NAND gate that clears the flip-flop. Interposed between the counter and the NAND gate are a series of switches, one for each stage of the counter. The flip-flop controls a switch to a source of reference voltage and the output of this switch controlled voltage from each of the multipliers is summed and fed to a demodulator.

Abstract: In known audio equalization systems, full room equalization cannot be employed because it introduces undesirable transient effects during the growth stage of a sound field, especially in a large auditorium. The invention seeks to solve this problem by establishing an initial state of the equalizing system giving a reduced degree of equalization whenever a signal commences but which effects a transition to normal equalization within a time typically of the order of some tens of milliseconds.

Abstract: The feature of the invention is an adaptive equalizer for modulated carrier transmission systems in which a received signal is subjected to a Hilbert transformation to obtain a second signal having a 90.degree. phase shift for all components. The two signals are then passed through a pair of filters each and the outputs are cross-combined to generate the cartesian coordinate signals of an equalized signal. The coordinate signals are combined in a polar converter and are then decoded to detect the amplitude and phase data components of the received signal.The equalizers are made adaptive by determining at each sampling time, the phase and amplitude errors in the signal and using these errors to modify the coefficients of the equalizing filters. The phase and amplitude errors are recoded into Cartesian coordinates and multiplied by the values of the samples at each tap of the filters to generate four error signals for each tap.

Abstract: A multi-level digital filter system applicable to modems is provided. The incoming data is read serially into M shift registers and read out in parallel by M further shift registers under the control of an M-bit clock, where M=log.sub.2 N and N is the number of levels. After appropriate conditioning by a logic control circuit, the parallel outputs are filtered separately by M digital shaping filters. The shaping filters each comprise a chain of shift registers the outputs of which are weighted by a resistor network and summed to produce a desired time response, which in an exemplary embodiment is the inverse Fourier transform of an ideal low-pass filter. Summing of the filter outputs produces an N-level signal. Specific examples of three-, four-, five-, six- and eight-level systems are disclosed.

Abstract: A group delay equaliser for a repeater in a waveguide communication system uses a magnetostatic wave delay line as a dispersive element to compensate for inherent dispersion in the waveguide. The delay line uses a thin ferrimagnetic film in which a propagation path is defined which is biased by a uniform adjustable magnetic field which is established to provide an adjustable dispersion characteristic. The film has associated with it means for preventing reflections of magnetostatic waves propagated beyond the ends of the propagation path. A substantially linear propagation delay with frequency is achieved over a bandwidth of 500 MHz. at a centre frequency of 1.5 GHz.