Synchronous Filters Patents (Class 333/173)
  • Patent number: 4315227
    Abstract: Because of the very large variety of useful filter configurations, it is highly desirable to have a generalized circuit topology from which all specific filters can be derived. A generalized switched-capacitor biquadratic active filter comprises a pair of operational amplifiers (10, 11), each of which has an unswitched feedback capacitor (D, B) connected between its output port (3, 3') and its inverting input port (1, 1'). A third through-switched capacitor (C) provides feedback between the output port (3') of the second amplifier (11) and the inverting input port (1) of the first amplifier (10). A diagonally-switched capacitor (A) couples the output port (3) of the first amplifier (10) to the inverting input port (1') of the second amplifier (11). The noninverting input ports (2, 2') of the two amplifiers are connected to signal ground.
    Type: Grant
    Filed: December 5, 1979
    Date of Patent: February 9, 1982
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventors: Paul E. Fleischer, Kenneth R. Laker
  • Patent number: 4313096
    Abstract: Switched capacitor topologies currently in use are susceptible to the deleterious effects of the parasitic capacitances associated with the switches. Topologies that are immune to these effects are disclosed. A first such embodiment comprises a first switch (22, 32), a capacitor (23, 33), and a second switch (24, 34) connected in series between one input terminal (1) and one output terminal (3) of the network. Third and fourth switches (26, 35 and 27, 36) are connected between the junctions (98, 42 and 99, 43) of the capacitor and the first and second switches, respectively, and the common junction (97, 41) of the second input and second output terminals (2, 4). A second embodiment is also disclosed.
    Type: Grant
    Filed: November 19, 1979
    Date of Patent: January 26, 1982
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventor: Paul E. Fleischer
  • Patent number: 4309678
    Abstract: The invention relates to filters using a charge-transfer device as an active element it consists in providing such a filter with an output circuit of first order interpolator type; this circuit may be external to the charge-transfer device or partially integrated threwith by associating therewith an additional weighting cell and by using another set of weighting coefficients.
    Type: Grant
    Filed: January 30, 1980
    Date of Patent: January 5, 1982
    Assignee: Thomson-CSF
    Inventor: Jean-Edgar Picquendar
  • Patent number: 4308509
    Abstract: A non-recursive transversal filter circuit employs a charge transfer device in which certain of the capacitive storage elements are divided into first and second capacitive portions having predetermined capacitance relationships. The charge in the second capacitive storage elements is sensed at predetermined times to produce an output signal. The relative capacitances of the second capacitance portions provide weighting factors to the filter. Embodiments include bucket brigade devices with bipolar and FET transistors as well as charge coupled devices.
    Type: Grant
    Filed: January 18, 1980
    Date of Patent: December 29, 1981
    Assignee: Sony Corporation
    Inventors: Takao Tsuchiya, Mitsuo Soneda
  • Patent number: 4306203
    Abstract: A filter has a plurality of series circuits each including a reactance element and a switching element and the series circuits are connected in parallel. The switching elements are driven by clock pulses of the same period. When the switching elements are driven simultaneously, information stored in the reactance elements is cleared, whereby the filtering band can be switched over at high speed.
    Type: Grant
    Filed: February 26, 1980
    Date of Patent: December 15, 1981
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Michio Sasaki, Isamu Miwa
  • Patent number: 4298970
    Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of discrete frequencies advantageous to provide useful data. Any drift in electrical circuits which might affect or be affected by the use of precise frequencies is undesirable. A synchronous detector facilitates the removal of noise components from the data stream by comparing in a commutative filter the phase difference between a switching signal taken from the incoming data signal path, after the second stage of commutative filtering, with the data signal emerging from the last stage of filtering. The synchronous detector also compares a data signal having two stages of filtering with another data signal having six stages of filtering with the additional filtering, causing a phase shift in frequencies outside the precise frequency window, which the synchronous detector also rejects.
    Type: Grant
    Filed: August 10, 1979
    Date of Patent: November 3, 1981
    Assignee: Sperry-Sun, Inc.
    Inventors: E. Neil Shawhan, Octavio A. Vela, Miles A. Smither
  • Patent number: 4293937
    Abstract: In a borehole acoustic telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of precise frequencies advantageous to provide useful data. A first transmitter in the system operates at a precise frequency to transmit a signal over the pipe where it is received by a receive and retransmit circuit path. Components in the receive and retransmit section filter and amplify a data component of the signal and retransmit the data signal at a precise frequency. Crystal controlled oscillator clocks are operated in the system at a same frequency in the transmitter and receiver-retransmitter to insure precise frequency control of the system.
    Type: Grant
    Filed: August 10, 1979
    Date of Patent: October 6, 1981
    Assignee: Sperry-Sun, Inc.
    Inventors: H. Eugene Sharp, Octavio A. Vela, Mils A. Smither
  • Patent number: 4293831
    Abstract: A plurality of MIS charge transfer systems are connected to the output of a first MIS charge transfer system and are operated in parallel with each other. The plurality of charge transfer systems form filters of the same kind, or of a different kind, and charge packets emitted thereby have different delay times and are subsequently converted into a voltage which is sampled at a higher frequency than the sampling frequency for the signal which is applied to the input of the first MIS charge transfer system. This voltage is smoothed by a simple low pass filter.
    Type: Grant
    Filed: February 25, 1980
    Date of Patent: October 6, 1981
    Assignee: Siemens Aktiengesellschaft
    Inventor: Rainer Lueder
  • Patent number: 4290034
    Abstract: A switched capacitor filter circuit which closely matches single pole RC filters at voice frequency. The filter pole is determined by the ratio of a first and second capacitor (C.sub.1 and C.sub.2). Any resulting loss is compensated for by an operational amplifier (13) in combination with third and fourth capacitors (C.sub.3 and C.sub.4) operating as a voltage divider circuit. A switch (16) may be provided for discharging one of the latter capacitors during nonsampling intervals. A further switch (17) may also be provided to cancel charge due to gate-to-drain overlap of the first switch.
    Type: Grant
    Filed: May 16, 1980
    Date of Patent: September 15, 1981
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventors: Donald L. Fraser, Jr., Armando J. Vera
  • Patent number: 4283696
    Abstract: The invention relates to a method for operating recursive filter circuits or analog storage circuits constructed according to the charge coupled device principle and to a circuit arrangement for implementing the method, in which method only each respective second stage a CCD is occupied with a charge representing a sampling value of an analog signal and the respective stages lying between these stages concerned are left empty. Known circuits constructed according to the CCD principle conduct the signal from the output stage of a CCD chain to the input of the CCD loop via an amplifier to which the input signal is supplied at the same time. Thereby, the amplification must very precisely amount to 1. An amplifier of the high stability required for that purpose which is arranged in common with the CCD concerned on a chip cannot be satisfactorily realized.
    Type: Grant
    Filed: August 27, 1979
    Date of Patent: August 11, 1981
    Assignee: Siemens Aktiengesellschaft
    Inventor: Karl Goser
  • Patent number: 4281296
    Abstract: An electrical filter circuit comprising charge transfer devices formed as lines consisting of individual CTD elements formed as four-terminal resonators formed as closed looped circuits and which determine the frequency-dependent transmission behavior of the filter circuit and wherein the four-terminal resonators are interconnected by way of a coupling circuit. In the invention, the filter circuit functions as a separating and shunt circuit and can be formed as an integrated circuit with two end resonators designed as self-contained closed looped circuits.
    Type: Grant
    Filed: July 24, 1979
    Date of Patent: July 28, 1981
    Assignee: Siemens Aktiengesellschaft
    Inventors: Hermann Betzl, Ernst Hebenstreit, Roland Schreiber
  • Patent number: 4281297
    Abstract: A filter circuit utilizing charge transfer delay lines having individual CTD elements utilizing four-terminal resonators each of which is designated as a self-contained closed looped circuit and which determine the frequency dependent transmission characteristics of the filter circuit and wherein successive four-terminal resonators are interconnected by way of a coupling circuit. The invention utilizes the coupling circuit mounted between adjacent four-terminal resonators which are constructed simply as possible and utilizing integrated circuit techniques. Amplifiers are connected in parallel with the input and/or the output of the individual four-terminal resonators and the signal flow direction of the amplifiers corresponds to that of parallel connected CTD lines and the series lines of the coupling circuit and the amplifiers have unidirectional transmission characteristics and an inverting amplifier is contained in at least one of the series lines.
    Type: Grant
    Filed: July 24, 1979
    Date of Patent: July 28, 1981
    Assignee: Siemens Aktiengesellschaft
    Inventors: Hermann Betzl, Ernst Hebenstreit, Roland Schreiber
  • Patent number: 4255725
    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.
    Type: Grant
    Filed: May 23, 1979
    Date of Patent: March 10, 1981
    Assignee: Thomson-CSF
    Inventors: Jean-Luc Berger, Jean-Louis Coutures
  • Patent number: 4251785
    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.
    Type: Grant
    Filed: June 22, 1979
    Date of Patent: February 17, 1981
    Assignee: Siemens Aktiengesellschaft
    Inventor: Hans-Joerg Pfleiderer
  • Patent number: 4231002
    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.
    Type: Grant
    Filed: March 5, 1979
    Date of Patent: October 28, 1980
    Assignee: Siemens Aktiengesellschaft
    Inventors: Karl Knauer, Hans-Joerg Pfleiderer
  • Patent number: 4224582
    Abstract: The peak output of a commutating capacitor triplet device (201) which contains three capacitors (10, 11, 12) connected in pairs across an input signal to provide six samples of each signal cycle, is obtained to provide envelope detection. To reduce output ripple by increasing the number of samplings of each cycle without increasing the number of capacitors, a portion of the output is obtained at the junction (13) of the capacitors, the amplitudes of the output and portion thereof are weighted with respect to each other by resistors (204, 205) and combined. In one embodiment, the positive and negative parts of the combined signal are applied to a full wave rectifier (207, 208, 214). In another embodiment, the positive and negative parts of the portion are inversely combined (306, 307, 308) prior to the portion being combined with the output of the triplet device.
    Type: Grant
    Filed: October 19, 1978
    Date of Patent: September 23, 1980
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventor: William Kaminski
  • Patent number: 4218665
    Abstract: A bandpass filter is disclosed which includes a low-pass filter and an analog delay circuit in which the delay time is set by a clock signal. THe analog delay circuit samples the voltage of the low-pass filter capacitor and delays the sampled voltage according to the clock signal. The output of the analog delay circuit is then used to equalize within a certain period of time the voltage of the low-pass filter capacitor. The analog delay circuit may consist of an integrated circuit BBD (Bucket Brigade Device) or CCD (Charge Coupled Device).
    Type: Grant
    Filed: March 17, 1978
    Date of Patent: August 19, 1980
    Assignee: Nippon Electric Company, Ltd.
    Inventor: Hisashi Fujisaki
  • Patent number: 4205283
    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.
    Type: Grant
    Filed: October 10, 1978
    Date of Patent: May 27, 1980
    Assignee: The United States of America as represented by the Secretary of the Army
    Inventor: William Donnally, Jr.
  • Patent number: 4204177
    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.
    Type: Grant
    Filed: February 10, 1977
    Date of Patent: May 20, 1980
    Assignee: U.S. Philips Corporation
    Inventor: Ludwig D. J. Eggermont
  • Patent number: 4197515
    Abstract: By combining a number of integrators with periodically switching means, which are sensing an input signal during circularly successive time intervals, sampled values are available for some of the latest time intervals sampled with a sampling frequency. By switching these values in a successive manner to an analog arithmetic circuit, it is possible to obtain an output signal with useful band-pass and band-reject properties depending on the sampling period and the arithmetic operation. According to one preferred embodiment, the output signal is the mean over the latest time intervals, giving an averaging system which, contrary to RC circuits, has a strictly limited memory. According to another preferred embodiment, the output signal is the different between the outputs of two integrators.
    Type: Grant
    Filed: October 5, 1977
    Date of Patent: April 8, 1980
    Inventors: Sven P. Hornfeldt, Karl O. U. Gafvert
  • Patent number: 4179665
    Abstract: A switched capacitor sampled data elliptic filter for data transmission or communication systems is disclosed. The filter section comprises three integrating operational amplifiers connected in series with a negative feedback connection between the output of the second operational amplifier and the input to the first operational amplifier, which is also connected to the input voltage source. Signals via a feed forward connection from the input voltage source and the outputs of the first and second operational amplifiers are summed by the third operational amplifier. Switched capacitors in the feed forward connection, the negative feedback connection, the inputs to all three operational amplifiers and in feedback sections of the first and third operational amplifiers are all connected to a two-phase clock driver operated at a preselected frequency.
    Type: Grant
    Filed: September 8, 1978
    Date of Patent: December 18, 1979
    Assignee: American Microsystems, Inc.
    Inventor: Roubik Gregorian
  • Patent number: 4156858
    Abstract: A transversal filter of the split electrode type employing a bucket-brigade device (BBD) is described. The BBD wells extend beyond the edges of the clocked gates of the BBD below second gates of different areas. These mask programmed second gates provide the filter output. Unlike other split electrode, capacitance sensing filters, these gates are not clocked, thus the filter has simplified output circuitry and a greater dynamic range.
    Type: Grant
    Filed: June 2, 1977
    Date of Patent: May 29, 1979
    Assignee: Reticon Corporation
    Inventors: Gene P. Weckler, Robert W. Brodersen
  • Patent number: 4151474
    Abstract: In a switched multipath filter network, the passband is varied by varying the duty cycle of the switches which commutate the constituent filters. When no filter is operative, the output connection of the filters is interrupted to prevent the unfiltered signal passing through, but the network output is smoothed to provide sample and hold action.
    Type: Grant
    Filed: August 18, 1977
    Date of Patent: April 24, 1979
    Assignee: Raytheon Company
    Inventors: Geoffrey G. Woollvin, Mieczyslaw Bilogan