Showing papers on "Electronic filter published in 1990"

A new approach to harmonic compensation in power systems-a combined system of shunt passive and series active filters

Abstract: A novel approach to compensating for harmonics in power systems is presented. It is a combined system of a shunt passive filter and a small rated series active filter. The compensation principle is described, and some filtering characteristics are discussed in detail. Excellent practicability and validity to compensate for harmonics in power systems are demonstrated experimentally. Although the source harmonic voltage was only 1%, the source harmonic current reached about 10% before the series active filter was started. After it was started, no harmonic current flowed into the shunt passive filter. In addition, no harmonic voltage appeared at the terminals of the shunt passive filter, because the source harmonic voltage was applied to the series active filter. The total loss of the series active filter was less than 40 W. It is concluded that the combined system is far superior in efficiency to conventional shunt active filters. >

Si IC-compatible inductors and LC passive filters

Abstract: Passive inductors and LC filters fabricated in standard Si IC technology are demonstrated. Q-factors from three to eight and inductors up to 10 nH in the gigahertz range have been realized. Measurements on a five-pole maximally flat low-pass filter give midband insertion loss and -3 dB bandwidth close to the nominal design values of 2.25 dB and 880 MHz. >

Gradient-based adaptive IIR notch filtering for frequency estimation

Abstract: The use of gradient-based algorithms with infinite impulse response (IIR) notch filtering for estimating sinusoids imbedded in noise is investigated. Two notch filter model structures are presented. The first is for applications where two signal sources with correlated noise components can be assessed. The second can be used in situations where only one composite signal source is available. Error surface analysis indicates that second-order modules are unimodal and result in guaranteed convergence. Higher-order modules are multimodal and require judicious choice of initial parameter estimates. Simulation results are included to demonstrate the performance characteristics of both filter structures. >

Filter circuit receiving upstream signals for use in a CATV network

Abstract: A two-way CATV network which in the preferred embodiment uses gating upstream narrowband filters in the distribution lines and/or trunks to substantially reduce upstream noise gathering. The filters sense the upstream signal energy and open in the event the energy exceeds a predetermined threshold.

Sigma delta modulator with distributed prefiltering and feedback

Abstract: A separate filter circuit is inserted between the D/A converter and the summing junction in the feedback path of a conventional sigma delta modulator. This additional filter allows control of the quantization noise transfer function profile independently of the forward signal transfer function. By proper tailoring of the transfer functions a third or higher order modulator can be constructed without instability developing.

A 1.4 V switched capacitor filter

Abstract: An approach to creating switched-capacitor circuits with supply voltages as low as 1.4 V is presented. The addition of one mask step creates an addition device type of low threshold. This device may be used both as a switch and in the amplifiers of switched capacitor circuits. A seventh order Chebyshev test circuit demonstrated performance approximating that of the more 5-10 V switched-capacitors filter circuits. By adding a second threshold adjustment implant mask for p-channel devices additional voltage reduction and performance improvement may be achievable. >

Applications of a first-generation current conveyor in current-mode circuits

Abstract: In current-mode filter circuits which utilise a single current conveyor as the only active device, the first-generation current conveyor permits feedback of the response without connecting filter elements to the output port. Complex poles can be realised in such circuits while maintaining high output impedance. The utility of this observation is illustrated by the derivation of new second-order, complex-pole, current-mode, all-pass networks that employ a single current conveyor. Laboratory and simulation results are compared

An octave-band MMIC active filter

Abstract: The design, fabrication, and measurement of a GaAs monolithic, active bandpass filter with a passband from 4 to 8 GHz is described. The circuit uses a set of cascaded lumped- and distributed-element LC circuits isolated by a feedback amplifier to realize an equivalent fourth-order filter response. The final circuit was fabricated on a 3-mm*2-mm GaAs substrate. >

Real-time ML estimation of very frequency selective multipath channels

Abstract: It is shown that the inverse filter is a good solution for estimating multipath channels when using binary sequences as the input signal. It is a maximum-likelihood estimator which enables the utilization of aperiodic sequences (bursts). Therefore, it is well suited for estimating very-frequency-selective channels. Since the channel is only occupied during short time intervals, it maintains compatibility with other services when measuring in occupied frequency bands. A practical realization shows that inverse-filter-based estimation techniques are well suited for implementing real-time channel sounders. The inverse filter is realized in SAW (surface acoustic wave) techniques. The implementation loss of 2.5 to 3.5 dB for the POP (peak/off peak) ratio shows that its realization is not particularly critical. The sounder estimates either full impulse responses or statistical parameters at a rate of 9 or 2.2 impulse responses per second, respectively. Relevant parameters characterizing the mobile radio channel are proposed. >

Electrical signal filter and method for manufacture of electrical signal filter internal circuit board

Abstract: An electrical signal filter in which circuit provided with filter circuits are inserted into a cylinder-shaped shield case, has a first cavity portion having an inner case. The side of one end of the inner case has the circuit boards inserted, and the side of the other end thereof is provided with one of an input side connector and an output side connector. The electrical signal filter also has a second cavity portion having a second shield case having an outer case. The side of one end of the second shield case is provided with one of an output side connector and an input side connector.

Unbalanced saw filter

Abstract: An unbalanced surface acoustic wave (SAW) resonator-filter is achieved by using a predetermined length of unbalanced transmission line to define a ground potential and permit two SAW resonators and such transmission line to function together as an unbalanced filter.

A Combined System of Shunt Passive and Series Active Filters

Abstract: A combined system of shunt passive and small rated series active filters has already been proposed by the authors. The operating principle and steady compensation characteristics have been presented also. The combined system can greatly reduce problems of using only shunt passive or shunt active filters and is suitable for harmonic compensation for large VA rated loads in power systems, because the required VA rating of the series active filter used here is considerably smaller than that of a conventional shunt active filter.In steady states, the combined system behaves like an ideal compensator, because the extraction of the harmonics easy. However, some loads such as cycloconverters fluctuate with rapid speed and cannot be regarded as steady loads. It is difficult for a conventional shunt passive filter to compensate for these fluctuating loads because they generate various frequency harmonics. So it is necessary to discuss transient compensation characteristics of the combined system when it is applied to compensation for fluctuating loads.In this paper, focusing on transient states, stability and compensation characteristics of the combined system are analyzed and discussed theoretically and experimentally in detail. The stable and unstable regions of the combined system and the problems faced by improving transient compensation characteristics are revealed. Then, to improve transient characteristics of the system, a new control method is proposed, and the validity is experimentally demonstrated.

Apparatus to improve image enlargement or reduction by interpolation

Abstract: An image interpolation apparatus receives an image signal in the frequency domain. The image signal is supplied to a filter circuit. The output of the filter circuit is transformed by a two-dimensional fourier transformation circuit into a filtered image signal in the spatial domain. The filtered image signal is linearly interpolated by an interpolation circuit to enlarge or reduce the image representing the image signal. The filter circuit, the fourier transformation circuit and the interpolation circuit are under the control of a processor. The processor sets the filter circuit a filter function representing the inverse of the modulated transfer function of the interpolation circuit to compensate for the degradation caused by the modulated transfer function of the interpolation circuit.

Integrated filter circuit

Abstract: An integrated filter (10) having a controllable frequency response includes a pair of cascaded differential transconductance amplifiers (12, 14) with the differential outputs of the first one of the pair being coupled to the differential inputs of the second one via coupling resistors (32, 36) and the differential inputs of the first one being coupled to inputs of the filter via input coupling resistors (20, 22). The differential outputs of the second transconductance amplifier are coupled both to outputs of the filter and are fed back (50, 52 and 54, 56) to the respective differential inputs of the two amplifiers to provide multiple inputs such that the damping factor of the filter is controllable for adjusting the filter frequency transfer function by varying the ratio of the coupling resistor value to the feedback resistor value while the damping factor is independent of the natural resonant frequency of the filter. Series coupled integrating capacitors (26, 28 or 38, 40) are coupled across the differential outputs of both pairs of amplifiers with the interconnection therebetween return to ground.

Parasitic insensitive programmable biquadratic pulse slimming technique

Abstract: A filter circuit with improved performance characteristics A biquadratic transconductance-C filter includes a differentiator in the feed forward path of the input signal to compensate for the non-ideal operation of the transconductance elements and to simplify the performance requirements of a variable gain amplifier also in the feed forward path The variable gain amplifier and feed forward technique are used to create two programmable magnitude, opposite sign zeros on the real axis, whose effect on the incoming data signal results in variable pulse slimming The addition of a differentiator in the feed forward path eliminates the effect of the output admittance of the transconductance elements on the filter's group delay The differentiator acts as a first order, high pass filter The frequency of the differentiator is controlled so that the input signal is attenuated before it is provided to the variable gain amplifier This reduces the dynamic range requirements of the variable gain amplifier without affecting group delay requirements

Active filter having reduced capacitor area but maintaining filter characteristics

Abstract: An active filter comprises a differential-type voltage-controlled current source. A first resistor is connected between the first input terminal of the voltage-controlled current source and a first signal source. A second resistor is connected between the second input terminal of the voltage-controlled current source and the second signal source (or the output terminal of the voltage-controlled current source). The incremental transfer conductance gm of the filter becomes smaller by R 2 /(R 1 +R 2 ) compared to that of an active filter which does not contain the first and the second resistors of the active filter of the invention, where R 1 and R 2 are resistance values of the first and the second resistors, respectively.

Adjoint networks revisited

Abstract: The authors demonstrate that the adjoint network concept can be used to generate alternative circuit realizations of well-known high-precision filter circuits with identical parameter sensitivities but different, possibly better, noise and distortion behavior. Both computer simulations and experimental results on several complex filter circuit examples are used to verify the proposed theory. >

Impact of OTA nonlinearities on the performance of continuous-time OTA-C bandpass filters

Abstract: A new technique for predicting actual large-signal frequency responses, including jump resonance, in high-Q bandpass filters constructed from OTAs (operational transconductance amplifiers) and linear capacitors is presented. These predictions are a function of the nonlinearities of the OTAs and the Q enhancement of the filter. This approach offers significant advantages over other published techniques: a closed-form expression is obtained which is used to estimate the sensitivity of the nonideal filter parameters to signal amplitude, OTA distortion and Q enhancement, and which offers valuable insight into the nonideal operation of the filter. A representative filter structure is discussed. It shows close agreement between measurement and predicted responses in the presence of both Q enhancement and QTA distortions. >

Experimental investigation of transform ratio ternary phase-amplitude filters for improved correlation discrimination

Abstract: Transform ratio ternary phase-amplitude filters (TR-TPAFs) encoding the modulation states 1, 0, — 1 have been investigated in theory and practice. Simulations have demonstrated that TR-TPAFs can be formulated to provide increased discrimination compared with binary phase-only filters. TPAFs have practical advantages over complex-valued matched filters—efficient electronic filter storage and real-time implementation with available devices, such as magneto-optic spatial light modulators (MOSLMs).These are associated with the use of only three discrete modulation levels. In an experimental study, significant increases in correlation discrimination were demonstrated for several test patterns, showing substantial agreement with computer simulations. The effects of an imperfect MOSLM zero-modulation state, present in our experiment, were modeled and investigated. The performance of the TR-TPAFs for different threshold line angles also was investigated.

Balanced filter circuit having a controllable balanced current multiplier

Abstract: A balanced filter circuit has a number of balanced pushpull amplifiers (10) whose inputs (11, 12) and outputs (13, 14) are coupled to filter resistors (20, 21, 22, 25, 27A/B) and filter capacitors (23, 24, 26A/B). In order to adjust the filter, the currents from the filter resistors to the inputs of the balanced amplifiers are varied by means of adjustable balanced multipliers (40).

Satellite receiving tuner

Abstract: PURPOSE: To prevent a filter circuit and an amplifier circuit from being invaded by an external unnecessary element by arranging a circuit part for converting an input signal into a satellite 2nd intermedient frequency signal on a part corresponding to an input terminal in a 1st shield case, the filter circuit and the amplifier of which are covered with a 2nd shield case. CONSTITUTION: The input terminal 1 is fixed to the outside wall face of the 1st shield case 14 and other parts are arranged in the case 14. The 2nd shield case 15 is arranged in the case 14 in the vicinity of the input terminal 1 and the filter circuit 2 and the amplifier circuit 3 are covered with the case 15. Even when an unnecessary external signal in an 1GHZ band is invaded from the vicinity of the input terminal 1 into the case 14, the case 15 blocks the unnecessary signal. Thus, no external unnecessary signal is inputted to the filter circuit 2 and the amplifier circuit 3 in the circuit part. COPYRIGHT: (C)1992,JPO&Japio

A 900 MHz SAW microstrip antenna-duplexer for mobile radio

Abstract: A novel, 900-MHz SAW (surface acoustic wave) microstrip antenna-duplexer designed for use in European mobile radio systems is presented. The duplexer consists of a transmitter SAW filter, two receiver SAW filters, a low-noise receiver amplifier, and a duplexing microstrip circuit. A dual-track filter design using interdigital transducers for track coupling provides low insertion loss (5 dB), small passband ripple (+or-0.5 dB), high stopband rejection (50 dB), and small chip-size (TO-39 package). The filters were fabricated on 36 degrees -rotated YX-LiTaO/sub 3/ substrates with a photolithographic technique. Due to the design of the microstrip duplexer, the selectivity of the front end is enhanced by 15 dB. >

Electronic filter effects on normal motor and sensory nerve conduction tests.

Abstract: Electronic filtering of the recorded signal is a significant aspect of all electro-diagnostic testing, but the filter type and frequency band are infrequently reported. Although the effects of different high- and low-frequency filters have been hypothesized, they have been the subject of little study under actual clinical conditions. This investigation showed clinically and statistically (p less than 0.01) significant alterations in both motor and sensory nerve evoked responses produced by modification of filter settings within the range routinely used for recording. As the low-frequency filter was varied from 3 to 20 Hz; large differences were seen in amplitude, area and duration of the compound muscle action potential. When the high-frequency filter was changed from 10 to 2 kHz, the mean amplitude of the sensory nerve action potential decreased by 12% and the mean latency was increased 0.1 ms. We conclude that filter parameters must remain constant when determining normal values and when performing serial studies on any patient. Filter settings should be reported as part of all electro-diagnostic reports and scientific manuscripts.

A high-performance, miniaturized X-band active mixer for DBS receiver application with on-chip IF noise filter

Abstract: A GaAs monolithic microwave integrated circuit (MMIC) dual-gate FET active mixer at X-band is described that is designed for direct broadcast satellite (DBS) applications. All of the components of the mixer, including biasing circuitry, RF, LO, and IF matching networks, as well as the IF noise filter, are implemented monolithically into a 25-mil*30-mil area. The design was process tolerant, and layout was compact for manufacturability and low cost. The mixer was integrated monolithically into a complete single-chip DBS low-noise block (LNB) converter. The active mixer has a conversion gain of 5.5 dB and a single-sideband noise figure of 8.5 dB. The circuit is manufactured using a 0.5- mu m gate length, buried p/sup -/ depletion mode MESFET process without substrate-through via holes. >

Optical information processor

Abstract: PURPOSE:To prevent an optical means from getting larger in size and, at the same time, to prevent influences of noises by only mounting a dividing means which divides the output of a photoelectric converting means and a sum signal producing means composed of operational amplifiers of high frequency stages on the optical means. CONSTITUTION:Reflected light rays from an optical disk 1 are condensed by means of photodiodes D1-D4. Outputs of the diodes D1-D4 are supplied to a focus difference signal/track difference signal generation circuit 29 respectively through resistances R1 of a filter circuit FL1 and operational amplifiers A2-A5. On the other hand, at an operational amplifier A1, the total sum of input currents of a high-band component from the circuit FL1 and a low-band component from the amplifier A6 is subjected to current/voltage conversion over the entire bands and the output of the amplifier A1 is supplied to a video circuit 19. When such constitution is used, narrow-band amplifiers can be used for the amplifiers A2-A6 and only the amplifier A1 requires a broad-band amplifier. Therefore, it is not necessary to make an optical head 3 larger in size, since only the circuit FL1 and amplifier A1 can be provided in the movable section of the head 3.

Digital/analog converter

Abstract: PURPOSE: To attain high resolution and fast response by supplying a PWM signal from a microcomputer to a least significant bit of a D/A converter processing 2 bits or over and inputting a digital signal to other digits. CONSTITUTION: A PWM (pulse width modulation) signal from a microcomputer 11 is inputted to the least significant bit LSB of a D/A converter 12 processing 2 bits or over and a digital signal from the microcomputer 11 is inputted to other digits. Then a filter circuit 13 receives an output voltage Vd from the D/A converter 12. When an n-bit D/A converter is employed as the D/A converter 12, a high speed D/A converter output is obtained with respect to other bits than the LSB, that is, (n-1) bits inputs. When the PWM signal is supplied to the least significant bit LSB, the filter is active and inactive in a small range between a voltage Vc and a voltage Va relating to the least significant bit, the filter time constant is enough to be small, the response is quickened and an optionally required potential is obtained between the voltages Va and Vc to attain high resolution. COPYRIGHT: (C)1992,JPO&Japio

Balanced filter circuit having a single amplifier

Abstract: A balanced filter circuit includes only one balanced amplifier (10) having an inverting input (6) and a non-inverting input (5) and an inverting output (7) and a non-inverting output (8) for realization of filter transfer functions Uout/Uin of the second or higher order from an input signal Uin at input terminals (1, 2) to an output signal Uout at output terminals (3, 4) having passive admittances which are composed of a parallel-combination of a resistor (R42, R44) and/or a capacitor (C41, C44) and/or a number of series-combinations of a resistor (R41, R43, R45) and a capacitor (C42, C43, C45).

Performance of direct-sequence spread-spectrum receiver using decision feedback and transversal filters for combatting narrowband interference

Abstract: A direct-sequence spread-spectrum (DSSS) receiver using both decision feedback (DFB) and two-sided transversal filters for combatting narrowband interference (NBI) is proposed. The receiver is made up of two branches. In the first branch, the conventional demodulator is followed by a DFB filter, while in the second, auxiliary branch, a demodulator with the carrier in quadrature is followed by a two-sided adaptive transversal (AT) filter. Performance of this receiver was analyzed on the basis of the calculated mean-square error and the probability of error at the output of the receiver. Special attention was paid to the effects caused by the propagation of errors in the DFB filter. The results obtained show that NBI rejection is fairly high and practically does not depend upon the difference of frequencies of the desired and interfering carriers or upon the interfering carrier level. >