Abstract: A high bandwidth transversal filter is described having an input impedance matching network, a tapped delay line, a plurality of weighting amplifiers, a distributed summing circuit, and an output impedance matching network. The delay line is implemented with a transmission line. The input impedance of this transversal filter depends on the inductance and capacitance of the transmission line and the capacitance of the inputs of each of the FET's used as weighting amplifiers. The gates of the FET's provide high impedance low loss taps of the delay line. The weighting is accomplished by either varying the drain current of the FET's or by using capacitive voltage dividers to apportion the tapped signals. The resulting weighted signals are applied to a distributed summing circuit which provides both high bandwidth summing and additional delays. This summer is also implemented with a tapped transmission line.

Abstract: For use in a pulsed-laser lidar such as a laser ceilometer, there are shown several examples of signal processing means for separating desired pulses due to targets such as clouds from strong background signals due to suspended particles causing poor visibility. The several examples belong to a class of means having the property of applying, to an electrical signal pulse waveform, a time-distributed signed electrical weighting function having negligible total weight, with alternations of sign of weights separated by intervals of the order of the width of the desired pulses.

Abstract: A time delay and integrate signal processing device is provided to which, in use, a clock signal having a duty cycle which varies linearly with time at a predetermined rate is applied at an input. The number of delay stages in the path of signals from a plurality of input taps is determined in accordance with a predetermined function of the rate of change of the clock duty cycle.Embodiments of the invention may be employed to advantage in SONAR applications where signals are received from a plurality of transducers to scan a sector by constructive summation of signal returns. The predetermined function may be chosen to minimize distortion during a scan and so scanning may take place at a higher rate than with prior art devices enabling full coverage of the sector with good range resolution to be achieved with a single device.

Abstract: A filter comprising a cascade arrangement of closed line CTD filtering loops has an intermediate CTD coupling loop formed with the adjoining output coupling of the preceding filter loop and input coupling of the succeeding filter loop. Disturbing self-oscillations outside the desired passband are eliminated by adjusting the voltage amplification factors of the amplifiers within the intermediate coupling loop, for example to from about five percent to about fifteen percent less than values selected to give a pure reactance branching circuit at the middle pass frequency. The resulting slight distortion of the transmission characteristic in the pass band of the filter can then be compensated by adjusting the amplifications of other amplifiers, and if necessary the capacitance conditions can be additionally altered.

Abstract: A resonator circuit formed in MOS technology for scanned analog signals, wherein such circuits are constructed for use with accumulators and information processing is accomplished by means of switched capacitors which are charged or respectively connected to each other by way of clock pulse transistors. In the present invention, the realization of general ladder networks or branching circuits for builders in single layer MOS techniques is accomplished by utilizing a second continuous branch which is switched to a first accumulator stage by clock pulse switches and is connected with a reference potential through a capacitor as well as to a further accumulator input through a series switch. The signal series arms are connected with the outputs of the total accumulator arrangement by way of time delay transit elements.

Abstract: Charge transfer filtering device which comprises a recursive filter and a non-recursive filter. The two filters on separate semiconductor substrates have charge injection means 12, 10 receiving the input signal E for the non-recursive filter 2 and the output signal S, previously phase-displaced by 180.degree. by means 9, for the recursive filter 1. Means 15, 16, common to both filters, ensure the reading and summation of the charge quantities weighted by means P and 14 and then the supply of the output signal S.

Abstract: A time-multiplexed CCD transversal filter includes N filter sections each comprising N substantially identical CCD's connected in parallel. An N-phase clock is connected to each filter section to provide a sampling frequency f.sub.s which is N times the clock frequency f.sub.c. The output taps of all the devices in a filter section are weighted in a predetermined manner and summed, and the outputs of all the filter sections are multiplexed to provide a continuously valid output.

Abstract: Disclosed is a Sidelobe Rejection Filter for reducing the time sidelobes seen in the auto-correlation output signals from a matched filter. Such matched filters are used with radars utilizing pulse compression techniques, for example. The sidelobe rejection filter may be utilized whenever the time response of the auto-correlation signals includes a plurality of sidelobes each having a period .tau. and having essentially the same amplitude. Accordingly, the disclosed sidelobe rejection filter is particularly useful for pulse compression radars employing linear FM (i.e., Chirp) or Barker phase coded waveforms.The matched filter includes a delay circuit coupled to receive the time response of the auto-correlation signal, which delay circuit inserts a delay of .tau.

Abstract: As all the weighting coefficients of the filter are positive, a weighted charge quantity is collected by a line beneath one of the elementary electrodes of each weighting electrode. A charge reading device is coupled to the line and supplies an electrical signal which is transmitted to the negative input of a differential amplifier, which receives the sampled input voltage of the filter at its positive input. The electrical output signal of the filter is taken, under low impedance, at the output of the differential amplifier, said signal being reinjected at the input of the filter by the injecting means.

Abstract: A differential charge-transfer device for transversal filtering or delay line applications. It comprises: two charge-transfer channels which respectively receive the two signals, the difference between which is to be formed; an electrode common to both channels; means for sampling the signals in each channel, this sampling taking place at the same instants in both channels; a set of electrodes in each channel which, on the application of potentials of period T, propagate the samples to the common electrode with a relative delay equal to T/2 from one channel to the other. The signal representing the difference between the input signals is extracted at the common electrode.

Abstract: The invention relates to an integrated filter circuit including a charge transfer device (CTD) transversal filter to which a sample-and-hold stage is post-connected. In such filters, a smoothing of the step-shaped signal output voltage emitted from the said stage is strived for. According to the invention, the smoothing ensues by means of a RC low pass which is realized by means of a "switched capacitor" circuit. This has two capacitors and two alternatively actuatable, electronic switches. The area of employment of the invention particularly embraces CTD transversal filters which are employed in systems with varying clock pulse frequencies.

Abstract: An apparatus for cancelling an undesired signal includes a programmable filter in which differential waveforms of a desired signal are superimposed on one another to form a composite signal similar to an undesired signal, a control circuit for detecting a level of the undesired signal to control the gain of a level adjusting circuit of the programmable filter so as to have a value proportional to the undesired signal, and a subtracter for subtracting the composite signal from an input signal.

Abstract: An input-weighted charge transfer transversal filter which comprises a charge transfer device including a plurality of stages, a plurality of signal charge injectors to inject into the stages of the charge transfer device weighted signal charge packets containing an AC component and a DC component, and a sense amplifier to sense the output signal of the transversal filter from the final stage of the charge transfer device, a DC charge injector to inject a predetermined quantity of DC charge into the first stage of the charge transfer device, and charge drains respectively coupled to the stages of the charge transfer device to drain at least DC charge from stages. Due to this arrangement the quantity of DC component injected by the signal charge injectors and transferred through the charge transfer device will be reduced. This leads to an improvement in packing density and signal detecting capability of the transversal filter.

Abstract: This invention relates to an integrated filter circuit with a charge transfer device transversal filter and a further low-pass filter pre-connected to the transversal filter. The pre-connected filter includes a first capacitor and a second, significantly smaller capacitor, as well as two alternately actuable electronic switches.

Abstract: A filter in the form of a semiconductor charge coupled device (CCD) split electrode transveral filter section (10) of many transfer stages, typically of the order of 150, is characterized by a controllable detection threshold level by means of the addition of an auxiliary CCD split-electrode section (20) of but a few stages, typically one or two. Each segment of a split-electrode 209 of this auxiliary section (20) is connected to the corresponding sense line of the transveral filter section (10).

Abstract: Adaptive filters are commonly used in echo cancelers and automatic equalizers. Usually adaptive filters include a tapped delay line and apparatus coupled to the delay line for producing a tap coefficient signal, whose sign and magnitude indicate the appropriate correction in adjusting the filter. However, in the presence of input signals having a partial frequency band spectrum, known filters tend to become unstable, e.g., tap coefficient signals blow up. The instant arrangement includes apparatus for weakly driving the tap coefficient signals to optimal values. As illustrated in a deceptively simple embodiment, a tap coefficient updating component is extended through a one's complement converter to a first input of a binary adder. A two's complement output of the adder is fed back to a second input of the adder. The sign of the adder output is also provided to a CARRY-IN input terminal of the adder.

Abstract: A phase multiplexed CCD transversal filter includes N substantially identical parallel-connected CCD's which acquire samples in a predetermined consecutive order over a given clock cycle so that the apparent sampling frequency is equal to N times the clock frequency. The output taps of the CCD's are weighted in a predetermined manner to provide a filter having a predetermined transfer function.

Abstract: A CTD transversal filter is disclosed which comprises a CTD arrangement with parallel inputs and evaluation circuits. The evaluation coefficients are set up in digital fashion by means of comparator-controlled input sequences of signal-dependent quantities of charge. High value coefficients may be established without the need to reduce a lower frequency transmission limit. With the invention, the transfer electrodes of the CTD are not supplied with the normal clock voltages but with the output voltages of a shift register in which circulates an item of logic information which forwards the input charges individually and consecutively by one electrode spacing. The application of this "electrode-per-bit" operation results in a considerable increase in the times for the individual input sequences. The invention is useful in programmable frequency filters.

Abstract: An input signal X(j) is fed directly to the positive port of a summing function and is simultaneously fed through a parallel channel in which it is delayed, and passed through an adaptive linear transversal filter, the output being then subtracted from the instantaneous input signal X(j). The difference, X(j)-Y(j), between these two signals is the error signal .epsilon.(j). .epsilon.(j) is multiplied by a gain .mu. and fed back to the adaptive filter to readjust the weights of the filter. The weights of the filter are readjusted until .epsilon.(j) is minimized according to the recursive algorithm: ##EQU1## where the arrow above a term indicates that the term is a signal vector. Thus, when the means square error is minimized, W.sub.(j+1) =W.sub.(j), and the filter is stabilized.

Abstract: A transversal filter utilizes a charge transfer device (CTD) shift register having parallel inputs and evaluation circuits assigned to those inputs. The evaluation circuits which form evaluation coefficients by reading-in signal-dependent amounts of charges. The charges are summed in the shift register and the charges successively reaching the output level are read out in series in order to form the filtered output signal. An electric coefficient setting is provided which guarantees a large relative adjustment range having a small requirement for semiconductor surface. The evaluation circuits have separately actuated source zones or additional source zones which are arranged in pairs on opposite sides of the CTD transfer channel, or which are provided with gate oxide and field oxide areas arranged beneath a transfer gate between the evaluation circuits and the shift register. A transversal filter constructed according to the invention is suitable for use as an electrically programmable frequency filter.

Abstract: A charge coupled device (CCD) transversal filter (TVF) having an improved electrode configuration and connecting arrangement which minimizes the noise that is added to the signal to provide a relatively high amplitude output signal and a relatively high output signal-to-noise ratio. The CCD transversal filter operates with the weighting coefficients determined by the one sided width of the electrodes and with one end of the split electrodes coupled to the output and the other ends of the split electrodes coupled to a reference voltage source. When some of the weighting coefficients of the desired impulse response are negative the output ends of the weighting electrodes are selectively connected to either the inverting or noninverting common connections of a differential amplifier in turn providing the transversal filter output signals. For a single polarity impulse response, all of the electrodes are coupled to an output arrangement without requiring an inversion.

Abstract: A transversal filter is disclosed in which the stages of an analog charge transfer device shift register, integrated on a doped semiconductor substrate, are provided with parallel inputs and evaluation circuits preconnected to the parallel inputs. The evaluation circuits respectively exhibit an area doped opposite to the substrate, a first input gate and a second input gate and a transfer gate, whereby the transfer gate is arranged immediately next to the transfer channel of the charge transfer device shift register. The one input gate is connected to an input signal, the other input gate is connected to a constant direct voltage, the oppositely doped area is connected to a first clock pulse voltage and the transfer gate is connected with a second clock pulse voltage. The output signal can be tapped at an output of the charge transfer device shift register. Comparators are provided having first inputs connected with a counter which is loaded with clock pulses and second inputs connected with digital memories.

Abstract: A control signal x(t) of known characteristics is transmitted over a transmission channel (1) together with a useful signal y(t).

Abstract: An adaptive interference reduction system for removing cross talk from a dual polarization system comprising a first adjustable filter for varying the phase and the weight of a first input signal, a second adjustable filter for varying the phase and the weight of a second input signal, a first adder for adding this first input signal and the weighted and phase adjusted output from the second adjustable filter, a second adder for adding the second input signal and the weighted and phase adjusted output from the first adjustable filter, a first noise-to-signal measuring device for generating a signal proportional to the noise-to-signal ratio in the output signal from the first adder, a second noise-to-signal measuring device for generating a signal proportional to the noise-to-signal ratio in the output signal from the second adder, and a dither-type control logic for dithering in-phase and quadrature square-waves in accordance with the signals generated by the first and second noise-to-signal measuring devices

Abstract: In the illustrated embodiments, the space required for a transversal filter with a given number of evaluation factors is reduced by providing valuator circuits embodying such factors as inputs to each successive capacitor element of a charge shifting device. In one mode of operation the signal to be filtered is sampled via the valuator circuits on each charge shift cycle while readout from the series output occurs on alternate cycles. Since the readout scanning frequency is a submultiple of the input sampling frequency, the filter is well suited as a low-pass filter.

Abstract: A delay network, having a chain of all-pass sections, each comprising two separate branches, a resistive and a capacitive branch, which terminate in amplifiers with negligible signal consumption whose output signals are combined. This enables an analog delay network to be realized in integrated circuit technology.

Abstract: A SAW signal processor includes a plurality of FET taps having individually programmable source-drain bias which controls both the amplitude and the phase of the mixing efficiency of internal product mixing of waves passing beneath the tap, in dependence upon the amplitude and polarity of the bias, the gates of the FETs may be interconnected so as to provide a summation of correlation at the output. Embodiments include multi-FET taps formed on substrates that are both semiconductive and piezoelectric, such as n-type epitaxial gallium aresenide, and ZnO coated silicon. Simple biphase and weighted biphase of phase-shifted tap pairs, for complete phase control, are disclosed.

Abstract: Signals extracted from the taps of a surface acoustic wave (SAW) device, as a consequence of a single wave propogating therein or as a consequence of interaction between a pair of waves propagating therein, are processed by linearly-controlled nonlinear product mixing and/or amplifying devices, to provide output signals in a serial chain of chips of RF, the magnitude of chips being dependent upon unique, selected bias applied to corresponding ones of the devices. The devices may be diodes operating in a bias range to provide impedence greater than the capacitive reactance impedance of the taps to which they are attached, thereby providing a linear RF voltage to DC bias current characteristic, while at the same time providing a nonlinear DC voltage to DC current characteristic for RF product mixing (where used); or the devices may comprise transistors, either field effect or bipolar, with similar suitable bias considerations when linearly-controlled product mixing is desired.

Abstract: An analog signal is processed through a lowpass filter and then regularly mpled at different sample times by a plurality of charge coupled devices. The outputs of the charge coupled devices are then summed and applied to a second lowpass filter which acts to produce a reconstructed and delayed version of the original analog signal. With this arrangement the time delay associated with each charge cell of the charge coupled devices is a whole number multiple of the effective sampling period of the system, and significant decreases in charge transfer distortion are achieved.

Abstract: Non-recursive digital filters having an output sampling frequency which is a factor of r lower than the input sampling frequency. A number of filters are described in which for each value of r and N (N being the number of filter coefficients) the time which is required to calculate an output sample is based on the output sampling period T.sub.u. This is achieved by using a storage device in the input circuit.

Abstract: A transversal filter has at least one analog shift register which includes a number of parallel inputs and one series output. A further number of individual, predeterminable evaluator circuits are provided, each evaluator circuit having at least one signal input for the input of the signal to be filtered and at least one output, and each evaluator circuit comprises a pair of capacitors arranged on a surface of a substrate. The substrate has at least one substrate terminal and comprises doped semiconductor material which carries a first insulating layer or blocking layer capacitor which contacts an oppositely doped zone located on the surface of the substrate and which is provided with a terminal contact. A second insulating layer or blocking layer capacitor is arranged beside the first capacitor, the second capacitor connectible, via a switching element, to an associated parallel input.

Abstract: A CTD (charge transfer device) transversal filter that utilizes displacement current charge substraction techniques to create positive displacement current charge summation for some electrodes and negative displacement current charge summation for other electrodes into and out of a common electrode node. The operation is accomplished by shifting by one half bit all signal charges within the negative tap structure with respect to the signal charges within the positive tap structure. Thus, only a single summing capacitance node is utilized with all taps, plus and minus, being connected together, eliminating the differential amplifier requirement of other CTD transversal filters. An arrangement of either zero tap weights with an extra one bit delay or a separate high-frequency pulse eliminating a one bit delay are utilized to provide or not provide, as desired, zero weighting between the tap sections.

Abstract: A filter comprising a charge-coupled device having a first group of cells weighted according to a recurring filter law and having a second group of cells weighted according to a non recurring filter law. The cells of the first and second groups are interposed alternately and the displacement of the charges under these cells is carried at frequency twice that of the sampling rate of the input signal. Thus the effects of transfer inefficiency are suppressed without added hardware.

Abstract: A transversal filter with a charge shift device is disclosed for realizing a given filter function. The charge shift device includes a substrate of doped semiconductor material having arranged on one surface thereof a series of shift elements, each shift element having a plurality of capacitor elements in correspondence to the number of shift pulse sequence lines employed with the charge shift device. A serial input is provided for the filter to which an input signal is connected. Capacitor elements connected to one of the shift pulse sequence lines have non-reactive amplifying output units connected thereto. At least one of the capacitor elements connected to at least one of the other shift pulse sequence lines has an additional non-reactive amplifying unit connected thereto. All of the non-reactive amplifying units also connect with an output of the filter.

Abstract: A surface acoustic wave signal processor having a plurality of taps, each connected to an external nonlinear device are arranged in pairs, each pair having its phase center aligned for interception of propagating waves at the same transversal distance from the launching thereof, the taps having configurations so that each tap in the pair receives signals at a phase which is inverted (180.degree. out of phase) with respect to corresponding signals received at the other tap of the pair, the product mixing output of the external nonlinear device for each tap being summed with the like output for the other tap in the pair, whereby all waves intercepted by the tap pair are cancelled at the product mixer outputs, along with certain of the components of product mixing having odd-ordered exponents. Disclosed configurations include tilted taps with co-propagating waves, longitudinally aligned taps with counter-propagating waves, and co-linear taps with plural channel, transversally displaced waves.

Abstract: In an illustrated embodiment, at least one analog shift register has a number of parallel inputs and one series output. A number of individual evaluating circuits receive the signal to be filtered and supply respective output quantities of charge equal to the product of the difference between the relevant signal value and a predetermined minimum or maximum value, and a respective individual evaluation factor. The output of each evaluating circuit can be connected via a switching element to an associated parallel input. According to the present teaching, a considerably lesser space requirement is realized by operating the filter so that for every consecutive scanned value of the signal each evaluating circuit is read in twice consecutively with a charge shift between such read-in processes, no charge shift being effected between the second read-in process and the first read-in process for the next scanned signal value. Read-in of the held signal may be effected more than twice.

Abstract: In illustrated embodiments, at least one analogue shift register has a number of parallel inputs and one series output. A number of individual evaluating circuits receive the signal to be filtered and supply respective output quantities of charge equal to the product of the difference between the relevant signal value and a predetermined minimum or maximum value, and a respective individual evaluation factor. The output of each evaluating circuit can be connected via a switching element to an associated parallel input. The capacity of every storage position of the shift register is at least such that it is always able to accommodate the maximum quantity of charge supplied by the preceding storage position, and when the storage position has a parallel input, can additionally accommodate the maximum quantities of charge supplied by the associated evaluating circuit (s). Various modifications are disclosed for reducing the space requirement of a transversal filter when implemented, for example, as a CCD.

Abstract: A tapped delay line transversal filter utilizing both surface acoustic wave and charge coupled device technologies, the surface acoustic wave tapped delay line portion providing a coarse selection and the charge coupled device tapped delay line portion providing vernier weighting.

Abstract: This specification describes a charge-transfer device transversal filter chip in which an input signal is fed in parallel into a number of channels the outputs of which are summed together to provide the desired transversal filter transfer function. Each channel contains an analog shift register, a signal splitter and a polarity selector. The shift registers are of unequal length to provide a different delay thru each channel. The signal splitter provides a plurality of signal paths thru each channel while the polarity selector determines whether a given path in a given channel is added or subtracted in the summation to determine the gain of the given channel in the summation.