Showing papers on "Electronic filter published in 1980"

Fundamental‐mode VHF/UHF minature acoustic resonators and filters on silicon

Abstract: Novel bulk acoustic‐wave high‐Q resonators and acoustically coupled resonator filters have been fabricated and operated at their fundamental half‐wavelength mode in the 200‐500‐MHz frequency range. These structures are fabricated on thin ZnO/silicon diaphragms with dimensions small enough to be incorporated within integrated circuits. Resonator Q’s near 2600 at the fundamental mode have been obtained and strong inter‐resonator acoustic coupling has been achieved yielding filters having insertion loss (untuned) as low as 5.5 dB.

An approach to programmable CTD filters using coefficients 0, + 1, and -1

Abstract: A delta modulation-like sampled analog filter structure for realizing low-pass filters is described. The filter uses only the coefficients 0, + 1 , and -1 and can be fabricated as a programmable CCD filter. Interpolation and decimation are employed to increase the accuracy of the delta modulation. It is shown that with this scheme a given response can be realized arbitrarily closely. Examples are included.

Active filters with zero transfer function sensitivity with respect to the time constants of operational amplifiers

Abstract: Most second-order RC active filters show a marked dependence on the gain-bandwidth product (GB) of operational amplifiers (OA's) when the \omega_0 to be realized is greater than 1 percent of GB and Q > 10 . Here designs are given that are virtually independent of OA's when \omega_0 GB and Q . Even for \omega_0=0.05 GB and Q=10 , the center frequency shift due to OA's is less than 0.1 percent. This desirable result is achieved by designing filter amplifiers which have zero first-order sensitivities with respect to the time constant \tau = 1/GB of the OA's used in the design. As a result, the filter transfer function has also zero first-order sensitivity with respect to \tau . General criteria for such designs are given. Experimental results show excellent agreement with theory.

Noise generated in switched capacitor networks

Abstract: It is shown that the noise generated in a passive first-order switched-capacitor lowpass filter has its origin in the thermal noise of the m.o.s. transistors' on-resistance. The spectral description of this noise at the output of the filter is given. The measurements made on a discrete laboratory model show good correspondence with the analytical results and confirm the noise model established.

Filter circuit utilizing charge transfer device

Abstract: A filter circuit of the type utilizing a charge-transfer device, such as a bucket brigade device, comprises a clocking signal drive circuit for supplying a clocking signal; a clock signal generator at whose output a clocking control signal is provided; a transistor whose base is connected to the output of the clock signal generator; a plurality of successive capacitive storage stages for sequentially holding a charge level representing a time-sampled input signal, each of the capacitive storage stages having a clocking electrode for receiving the clocking signal so that the charge level is transferred from one to another of the capacitive storage stages in succession, and at least one of the capacitive storage stages being formed of first and second parallel-connected capacitive circuit portions, and the first and second capacitive circuit portions having respective clocking electrodes coupled to the clock signal generator and to the emitter of the transistor, respectively; and a current feedback circuit, such as a current mirror circuit, for detecting the current flowing through the collector of the transistor and applying a corresponding current to a capacitive storage stage in advance of that stage which is coupled to the emitter of the transistor.

Data bus transceiver

Abstract: A data bus transceiver reduces self-induced noise by using trapezoidal drive waveforms. A differential receiver stage of the transceiver has a threshold voltage matched to the midpoint voltage of the drive waveform to reduce distortion, and a low-pass filter matched to the slew rate of the drive waveform to reduce noise while causing minimum progation delay. The transceiver has been integrated using back-to-back junction capacitors in the driver and filter circuits and these capacitors have been biased to reduce their variation in capacitance as a function of the voltage applied across them.

Generation of low-sensitivity state-space active filters

Abstract: This paper investigates the use of the similarity tranformation in the generation of high-order state-space active filters having minimized sensitivities. A sensitivity performance measure similar to the Rosenblum-Ghausi multiparameter sensitivity figure is defined, and a frequency independent relationship between the sensitivity measures of equivalent systems is derived. The results of optimizing an all-pole bandpass filter and a low-pass elliptic filter are presented, along with a detailed analysis of some of the attributes of the optimized realizations. The paper then examines the possibility of simplifying these optimized systems while maintaining good sensitivity behavior, by slightly altering the systems about their optimized values.

An integrated real-time programmable transversal filter

Abstract: Implementation, measurements, and characteristics of a fully integrated 32 tap real-time programmable transversal filter, which facilitates a number of filter applications, are discussed. It uses RAMs and 16 MDACs for tap weight programming and pipe organ structure to provide for a large variety of adaptive convolutional and correlative signal processing with optimum compromise among power dissipation, computational speed, size, and performance. The filter was constructed with the combined technology of bucket brigade devices and switched capacitors.

Amplitude and phase equalizer

Abstract: Minimal realization of an optimum amplitude and phase equalizer is disclosed. A first amplifier circuit including first respective passive filter elements provides both high and low frequency amplitude equalization. A second amplifier circuit including second respective passive filter elements provides first, second or higher order phase equalization, respectively, with gain. The equalizer operates between voltage sources and virtual ground to minimize noise picked up from parasitic capacities and external sources.

Monitoring device for the capacitor battery of a d-c filter circuit

Abstract: A circuit for monitoring the capacitor battery of a filter circuit connected to a transmission line, the capacitor battery consisting of at least two parallel legs, each with a number of series-connected capacitors. A first signal is produced which corresponds to the total alternating current flowing through the capacitor battery. A second signal is produced which corresponds to the difference between the currents flowing through the respective parallel legs of the capacitor battery. The current difference signal is compared with a respective fraction of the total current signal. A fault indicator signal is produced if the difference between the difference current signal and the fractional total current signal exceeds a predetermined threshold value. Further circuitry is provided for correcting drift in the difference current signal, which may be caused by temperature variations or acceptable capacitor failures. Automatic ranging circuitry may be provided in embodiments of the invention in which the total capacitor battery current varies in amplitude over a large range.

Earth contact monitoring device for a polyphase three-phase filter circuit

Abstract: A monitoring system for detecting earth contact of at least one phase of a polyphase network. Each of the phases in the network is connected by a capacitive-inductive filter to a neutral node which is connected to earth. In one embodiment of the invention, the current flowing from the neutral node to earth is detected by an induction current transformer which provides a signal responsive to said earth current. The output signal of the induction current transformer is conducted through at least one low pass filter for suppressing harmonics, and rectified to produce a direct current voltage signal, the amplitude of which is proportional to the amplitude of the fundamental frequency component of said signal. A fault indicating signal is produced when the direct voltage signal exceeds a predetermined value.

An Optimal SAW Filter Design Using FIR Design Technique

Abstract: An optimal design involving minimum number of transducer finger in a SAW filter has been developed, using the FIR (Finite Impulse Response) approximation.

Novel active filters using amplifier pole

Abstract: Active R realisation of bandpass and lowpass filters using lossy simulated inductors and capacitors is described.

Temperature control circuit for electric heating device

Abstract: PURPOSE:To exercise accurate temperature control without causing fluctuation of detected temperature even if the hygroscopicity of a heat-sensitive element varies, by inserting a correcting circuit between a filter circuit and a switching circuit. CONSTITUTION:A correcting circuit K is inserted between a filter circuit 11 and a switching circuit 13. A circuit K consists of a current detecting circuit 19 which detects a current flowing through a heat-sensitive element 5 by a voltage signal corresponding to the impedance of the element 5 sent from the circuit 11, a reference voltage detecting circuit 20 which detects the output of an oscillating circuit 9, a phase detecting circuit 21 which detects the dielectric loss angle sigma of the element by the output signals of the circuits 20 and 19, an impedance detecting circuit 22 which detects the impedance of the element 5 on the basis of the output signal of the circuit 19, an arithmetic circuit 23 which receives the combined detection value of the dielectric loss angle sigma from the circuit 21 and a detection value Z from the circuit 22 and then outputs the temperature of a heater 3 corresponding to the detection value, and a voltage level correcting circuit 24 which inputs a voltage level signal, corresponding to the temperature value from the circuit 23, to a trailing comparing circuit 14.

Method and apparatus for suppressing noise during nondestructive eddy current testing

Abstract: A filter apparatus (2) is disclosed for filtering out any reoccurring noise (5) present in a defect signal (1) received from a flaw detection device (4) such as an eddy current test probe. Filter circuit means (10) receives the defect signal generated by the flaw detector device and produces an output signal (5) duplicative of any reoccurring noise present therein. A differential amplifier (50) subtracts the output signal (5) of the filter circuit means from the defect signal (1) generated by the flaw detection device and amplifies the difference. A filtered defect signal (9) void of any reoccurring noise is thereby produced.

Lowpass filter with electronic control of cutoff and resonance

Abstract: A lowpass filter circuit having an electronically controllable cutoff frequency and utilizing a feedback current mirror circuit as a variable impedance element. The filter circuit employs low noise, low distortion output circuitry and includes means for electronically controlling resonance.

D/a converter

Abstract: PURPOSE:To reduce the burden of a filter circuit, by alternately giving an average output between the present data and the data before by one and the data before by one itself. CONSTITUTION:The output data of an audio synthesizer 10 is read in the 1st register 11 with the clock P1 in 8kHz, and the output data of the register 11 is read in to the 2nd register 12 with clock P2 in 8kHz. The output data of the registers 11, 12 is given to an interpolation circuit 13 and the data averaged with both the data is outputted. Switches 14, 15 are turned on and off by complementary clocks P14, P15 which rise every 62.5mus (16kHz), and the output data of the register 12 and the interpolation circuit 13 are alternately given to a D/A converter 16. No 8kHz component is present at the output of the converter 16.

Surface acoustic wave filter device with equalization of stray coupling

Abstract: A surface acoustic wave filter device in which a capacitative coupling means is provided to couple at least one of the terminals of the SAW input transducer to at least one of the terminals of the output transducer, in order to equalize the levels of signals which are induced on the pair of output terminals of said output transducer without assuming the form of surface acoustic waves. The stray inductive coupling which normally occurs between the input and output terminals of the SAW filter degrades filter performance. Since the inductive coupling to the two output terminals is normally unequal, the inductively coupled unfiltered signals cannot be completely rejected by a balanced differential amplifier. By equalizing the levels of unfiltered signals at the output terminal, effective rejection by a differential amplifier is possible.

Integrated CRC filter circuit

Abstract: A capacitor-resistor-capacitor (CRC) element for active filter realization, which is fully integrable and compatible with MOS technology, is described. The incorporation of the CRC element in a semiconductor integrated circuit active filter also is described. The structure of the CRC filter element is closely analogous to a depletion mode MOS field effect device, except that the channel zone 26 is doped to a level which substantially precludes conductivity modulation at the usual operating voltages. However, the doping level is such as to enable the use of the channel zone as a semiconductor resistance element. Thus, the N-channel CRC element realized in the NMOS technology comprises a first capacitance composed of the gate 27, gate dielectric 38, and resistive channel 26, paralleled by the resistive channel 26 itself constituting a resistor, and then the underlying PN junction capacitance between the N-type resistive channel 26 and the underlying P-type semiconductor body portion 21. An active low-pass filter consists of two CRC elements and an operational amplifier and utilizes the positive feedback principle.

IF Bandpass shaping circuits

Abstract: An IF bandpass shaping circuit for use with a television receiver having a tuner for providing intermediate frequency signals comprises a surface acoustic wave (SAW) filter coupled to the tuner. The SAW filter provides a predetermined bandpass response. A tuned circuit is coupled between the tuner and the output of the SAW filter. The tuned circuit is responsive to a frequency bandwidth which is narrow relative to the response of the SAW filter. The tuned circuit response is added to the output of the SAW filter to provide a modified SAW filter response.

Rodent control apparatus and method

Abstract: Apparatus and method for producing ultrasonic sound waves used to disperse rodents including negative feedback damping of a tuned band-pass filter output circuit. An electrical signal is frequency modulated, amplitude modulated asynchronously with the frequency modulation, pulsed on and off and applied to a speaker to produce ultrasonic sound waves corresponding thereto. The output signal is passed through a tuned band-pass filter circuit which includes negative feedback damping to reduce the power consumption of the amplification of the output signal and in part to produce the band-pass characteristics of the band-pass filter output circuit.

Filter circuit employing surface acoustic wave device

Abstract: A filter circuit comprises a surface acoustic wave device including input and output transducers. A tuning coil is interposed in series between an input terminal and the input transducer and/or between an output terminal and the output transducer. A piezoelectric resonator is connected in parallel with the tuning coil. The resonance frequency of the piezoelectric resonator is selected to be approximately equal to the frequency where an attenuation pole appears. The tuning coil and a capacitance component of the piezoelectric resonator and a clamp capacitance of the transducer constitute a tuning circuit, which is tuned to a given frequency in the passband.

An active-compensated double-integrator filter without matched operational amplifiers

Abstract: All active-compensated double-integrator filters proposed up to now require matched operational amplifiers. This condition is never fully met in practice, resulting in a Q-error that can be large at high-Q and high pole frequencies. A superior double-integrator filter is presented here, which does not require matched operational amplifiers to give error-free Q even under extreme conditions.

Circuit arrangement for a wide-band VHF-UHF television double superheterodyne receiver

Abstract: OF THE DISCLOSURE: The signal transmission lines in a double conversion stage for a double superheterodyne VHF-UHF television receiver are mainly constructed of unbalanced circuits rather than balanced circuits. The circuit arrangement comprises a wide-band amplifier for receiving the incoming carrier frequency, first and second frequency conversion stages, and an inter-mediate frequency amplifying stage. Connections between the wideband amplifier and the first frequency conversion stage as well as connections between the second frequency conversion stage and the intermediate frequency amplifying stage are achieved by means of unbalanced circuits. Each of the first and second frequency conversion stages comprises a mixer constructed of a single balanced circuit, a local oscillator and an unbalanced/balanced conversion circuit interposed therebetween. A filter circuit, comprising a band-pass filter and a low-pass filter, interposed between the first and second frequency conversion stages, effectively blocks spurious signals.

A parametric study of aliasing error for a narrow field of view scanning radiometer

Abstract: Starting from the general measurement equation, it is shown that a NFOV scanner can be approximated by a spatially invariant system whose point spread function depends on the detector shape and angular characteristics and electrical filter transfer function for given patches at the top of the atmosphere. The radiometer is modeled by a detector, electrical filter, analog to digital converter followed by a reconstruction filter. The errors introduced by aliasing and blurring into a reconstruction of the input radiant exitance are modeled and analyzed for various detector shapes, sampling intervals, electrical filters and scan types. Quantitative results on the errors introduced are presented showing the various tradeoffs between design parameters. The results indicate that proper selection of detector shape coupled with electrical filter can reduce aliasing errors significantly.

Remote controller using sound wave as medium

Abstract: PURPOSE:To prevent malfunction due to a low-frequency and large-level noise by dividing arrival sound waves into higher and lower bands than a fixed frequency and by stopping an output signal when a lower band output is greater than a higher- band output. CONSTITUTION:The output of microphone 1 receiving sound waves arriving from direction A is amplified 2 and inputted to high-pass filter circuit 3 and low-pass filter circuit 3a. The output of circuit 3 is inputted to Tr9 by way of transistor Tr23 and inversion amplifier 7, and that of circuit 3a is to Tr24. Then, Trs 23 and 24, constituting the comparator, input a signal of ''1'' to AND circuit 22 when an input to comparator 23 is greater. On the arrival of a high-band sound wave, Tr9 becomes unconducted and capacitor 35 is gradually charged by power supply 34 up to a high voltage; when the arrival of the sound wave continues, it is charged up to a fixed value, thereby operating FF37 by way of trigger diode 36 and circuit 22. However, a low-level signal is inputted to circuit 22 with an input to Tr24 greater and circuit 22 disallows the signal to pass through, so that FF37 will never operate.

Keyed noise filter in a television receiver

Abstract: A video signal channel in a television receiver includes a keyed filter, followed by a keyed automatic brightness control circuit for establishing a desired black or blanking level for the video signal. The brightness control circuit operates during blanking intervals of the video signal to sense the blanking level of the video signal for deriving a control signal which is utilized to maintain a desired blanking level. The filter comprises a high-pass filter circuit which is decoupled for filtering purposes during image intervals, but is coupled to the video channel during the blanking intervals for suppressing high frequency signals including noise, when present, in the video channel during the blanking intervals. The sensed blanking level and the control voltage are therefore unaffected by noise components which would otherwise impair the control signal and thereby the operation of the brightness control circuit.

Elastic surface wave filter circuit

Abstract: PURPOSE:To obtain flat amplitude characteristics by lowering the Q value of a resonating circuit by connecting a variable resistance to inductance which compensating the internal capacitance of an elastic surface wave filter used in a VSB amplifier for TV broadcasting equipment. CONSTITUTION:The input terminal 7 and output terminal 8 of an elastic surface wave (SAW) filter 6 are connected to a preamplifiter 9 and a buffer amplifier 10 composed of an OP-AMP. To the output terminal 8 of the filter 6, an inductance element 11 and a variable resistor 12 are connected in parallel, and the inductance of the element 11 is so set that resonance occurs within the passing band of the filter, thus reducing the transmission loss of the filter 6 due to internal capacitance. The resistor 12 adjusts the Q value of a resonance circuit consisting of the internal capacitance and element 11. The Q value is adjusted to a prescribed value to obtain a filter which has steep rising and breaking characteristics and flat frequency characteristics within the passing band as shown by a solid line B.

Multiplex radio repeater

Abstract: PURPOSE:To make it possible to remove disturbance that tertiary and quinary distortions of several received waves affect other received waves by providing independently a branching filter circuit and pre-amplifier for two adjacent received signals each CONSTITUTION:A received signal is led to branching filter circuits 12a to 12d according to the rotation direction of circulator 11 and filters 14a to 14d branch it into groups of signals (f1) and (f2), (f3) and (f4), (f5) and (f6), and (f7) and (f8) of adjacent frequencies through circulators 13a to 13c; and they are amplified by pre-amplifiers 15a to 15c, whose outputs are inputted to branching filter circuits 16a to 16d Next, filters 17a to 17d remove odd-order distortions generated by amplifiers 15a to 15d and circulators 18a to 18d mix the outputs, so that the composite output will be sent to a feeder via circulator 19