Showing papers on "Electronic filter published in 1978"

Saw IF Filter on LITaO3 for Color TV Receivers

Abstract: More than eight years have passed since DeVries et al. reported the first attempt at installing SAW (Surface Acoustic Wave) filters in a TV set(1). In Japan, SAW IF filter development has been continued by several companies and TV receivers incorporating SAW filter have been placed on the market since 1977.

Design of signal flow graph (SFG) active filters

Abstract: A systematic procedure is presented for the design of active filters obtained as operational simulations of LC ladder prototypes. The method is based on the signal-flow graph (SFG) approach, but allows one to obtain the final circuit without ever considering signal-flow graphs. Practical design problems, namely, scaling for maximum dynamic range, stabilizing the reciprocator amplifiers, predistorting the LC prototype to compensate for the parasitic reactances introduced by reciprocators, eliminating the inherent dc offsets, and tuning are solved and illustrated by examples. Complete design and experimental results are given for a twelfth-order bandpass channel bank filter.

Active R ladders: High frequency, high order, low sensitivity active R filters without external capacitors

Abstract: Active R filter techniques which make use of the pole of an operational amplifier to produce the state variables without the need for inductors or external capacitors may be employed to simulate all of the elements of both singly and doubly terminated reactance ladders. Although the design techniques are very simple and follow directly from passive synthesis techniques, the resulting filters offer high-order circuits with low sensitivity. However, the primary advantage of these active R filters is the ability to design filters which operate in a considerably higher frequency range than obtainable with standard active RC designs. While still primarily of research interest due to dynamic range problems and temperature sensitivity problems, active R ladders may be adequately compensated to allow many applications in specialized signal processing environments.

Multiple-amplifier RC-active filter design with emphasis on GIC realizations (Invited Paper)

Abstract: The use of more than one amplifier to realize an RC-active filter is now economically viable because of the relatively low cost of high-performance operational amplifiers. In this review article, multipleamplifier RC-active synthesis and design techniques are considered. Multiple-amplifier circuits are described that use generalized immittance converters or integrators to realize low-sensitivity high-quality biquadratic circuits and active ladder circuits.

Linear transformation active filters

Abstract: An approach is presented in this paper for the design of active filters from doubly terminated lossless ladder filters. The method relies-on-the-lnear transformation of port variables from the V-I domain to a new domain in which the filter is realized actively. The resulting active filters are referred to as linear transformation active (LTA) filters. The transformations are applied on an element-by-element basis thus producing a systematic and effective way of achieving new active structures while others like the leapfrog and the wave active filter structures appear as special cases. Examples are presented in the paper to show the efficiency of the method and the importance of the results.

Dynamic filter for a moving head disk storage system

Abstract: A dynamic filter circuit used to process analog position error information in a disk drive head-positioning servo system is disclosed. The filter circuit monitors the velocity of the disk drive carriage and dynamically increases the gain and bandwidth of the filter as the carriage velocity increases. Specifically, an operational amplifier in feedback configuration is used in which the feedback networks are switched in response to the velocity signal. At low carriage velocity the filter has low gain and reduced bandwidth and therefore helps to decrease sensitivity of the system to noise. At high carriage velocities the gain and bandwidth of the filter are increased to minimize the effects of missing servo data.

The composite active filter: A combined wave-active and gyrator-C filter

Abstract: With two inverting or noninverting active hybrid networks in a wave structure, wave-active, filters can be constructed without the need for additional inverting amplifiers. One-to-one correspondence exists between the dynamic elements of the active and passive networks. The hybrid has one bidirectional and two undirectional ports. Tandem connection at the undirectional ports leads to S-parameter realizations such as the ladder. Series and parallel connections at the bidirectional ports, while not strictly wave-active, can be used to reduce the number of amplifiers or to derive realizations for such networks as parallel ladders. Gyrator- C realizations in which the gyrator is a loop of an inverting and a noninverting hybrid become a special case of the composite filter. Experimental results show agreement with the analytic conclusions and confirm the low sensitivity.

High-Q selective filters using mechanical resonance of silicon beams

Abstract: The theory of integrated high- Q selective filters based on the mechanical resonance of single silicon beams is presented. The method for transfer function calculation is developed, and it is shown that the silicon beam filters have high- Q selective characteristics. A construction procedure based on anisotropic etching of silicon and classical integrated technology is proposed.

Remotely powered intermediate amplifier for communications transmission

Abstract: A remotely powered intermediate amplifier for communications transmission incorporates two sectional amplifiers and a filter circuit interconnecting the output of the first sectional amplifier with the input of the second sectional amplifier.

Dual tone multifrequency signal receiver

Abstract: A system and method for detecting the presence of a tone burst and identifying the frequency signals contained within the tone burst of a dual tone multifrequency system includes an arrangement for applying the tone burst to a plurality of filter circuits that are tuned to respectively different frequencies including those frequency signals of which the tone burst may be comprised. The outputs of the filter circuits are monitored and signals representative of the filter outputs are compared with a first set of reference criteria, at a prescribed interval of time after beginning the monitoring of the outputs of the filter circuits. A history profile for each of the signal outputs of the filter circuits is maintained and in order to accurately identify a valid tone pair, an analysis is made of the level signal outputs of the filter circuits. Specifically, upon the monitored outputs of the filter circuits satisfying the first set of reference criteria and being also identified as those which satisfy a prescribed history profile, there are produced identification codes indicating the frequency signals which correspond to a valid tone burst.

Voice frequency RC active filter

Abstract: A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter. Each generalized impedance converter network includes a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with the amplifiers to provide the network with a driving point impedance ##EQU1## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor. At least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 is functionally trimmed to tune the filter. The capacitors in the filter are preferably discrete polycarbonate capacitors with a capacitance tolerance of ±5%, and all having the same value.

Self-adapting equalizer

Abstract: A control signal x(t) of known characteristics is transmitted over a transmission channel (1) together with a useful signal y(t). The equalizer comprises essentially: a local generator (5) for generating a control signal which is identical with the transmitted control signal and in phase with the control signal component x'(t) as received at the equalizer; a filter circuit (6) for substantially isolating the control signal component X"(t) from the received signal (y'(t)+x'(t)), a first non-recursive self-adapting transversal filter for synthesising the reciprocal of the transfer function of the transmission channel (1) in response to the locally generated control signal x(t) and the isolated control signal component x"(t); a second transversal filter (9) having the same structure and using the same weighting coefficients as the first transversal filter; and a subtractor for subtracting the isolated control signal component x"(t) from the received signal to produce an approximation y"(t) of the useful signal, which approximation it supplies to the second transversal filter (9) to obtain a substantially equalized useful signal y(t). This circuit uses two transversal filters where previously it has been necessary to use three.

Switching circuit for the disabling of spurious sensor signals

Abstract: A controllable filter circuit for removing noise from the useful picked up speed sensing signal in an anti-skid vehicular braking system. The controllable filter circuit includes a pickup device, a frequency dependent low-pass filter, a sine-wave to rectangular-wave converter and threshold circuit, a frequency to voltage converter and a switching circuit for actuating the low-pass filter for dampening and blocking troublesome noise signals from the speed signals prior to feeding them to logic, amplifying and output devices.

Failure Analysis of Passive Devices

Abstract: The failure analysis of passive devices requires all the skills and technology used in the failure analysis of solid state devices. Passive devices use similar manufacturing methods compared to solid state techniques to accomplish the finished device. Thin oxides, used in the manufacturing of tantalum slug capacitors, are subject to current and voltage transients which concern analysts on MOS structures. To create the K factor in the dielectric of ceramic capacitors, ppm's of additives are used. These can be more difficult than diffusions in determining their effect on the device performance. Resistors suffer from all the structural effects of moisture, voltage transients, or contamination reported in the studies on integrated circuits or hybrids. Filters and small inductors packaged for circuit application are subject to problems of handling and board insertion as well as the above mentioned failure modes. In the choice of analyzing a passive component over an integrated circuit or LSI circuit, there are times when many analysts would rather accept the more complicated solid state circuit rather than tackle the simple passive unit.

Electrical filter of cascaded surface acoustic wave resonators

Abstract: Surface acoustic wave resonators are used to provide band pass filters. The length of each resonator is related to the lumped constant inductor and capacitor values of the components of the low pass filter equivalent. This invention allows high frequency s.a.w. type filters to be constructed by reference to already available inductor and capacitor values from tables of low pass filter designs.

Programmable dynamic filter

Abstract: A programmable dynamic filter for use with a time-shared electronic organ or the like includes a filter circuit responsive to a logical state of a control signal for tracking notes generated by the instrument. Means are provided for programming the filter independently of generated notes by selectively adjusting the pulse width of the control signal to achieve desired musical effects.

Microwave low-pass band-pass filter circuit - has several longitudinal and lateral branches and has parallel and series resonant circuits

Abstract: A low pass or bandpass filter consists of a number of longitudinal branches which have lateral branches between them. The longitudinal branches contain one or more parallel resonant circuits, in which when designed as a low pass filter the lateral branches consist of a series resonant circuit (Pk), and when designed as a band-pass each lateral branch consists of a pair of series resonant circuits. The filter circuit is intended especially for use in a microwave network with very small insertion loss.

Design of high-order active filters in integrated circuits

Abstract: This correspondence considers the design of high-order filters using follow-the-leader feedback configurations and active-R biquadratic blocks. Statistical sensitivities of various second-order active-R and active-RC sections are compared, and experimental results of a sixth-order Butterworth bandpass filter are also included. The FLF configuration and versatile active-R blocks are also suitable for fully integrated filters.

Highpass and bandpass filters using a new single-amplifier simulated inductor

Abstract: A new single-amplifier single-capacitor circuit simulating a grounded inductor, for use in active RC highpass and bandpass filters, is discussed, and a method of compensating for the nonideal behaviour of simulated inductors of this type is presented. In contrast to known compensation methods, the compensation procedure proposed here does not seek to improve the nonideal simulated inductors, but deliberately designs the simulating circuit to have a specific biquadratic impedance function and then modifies the filter circuit so as to produce the required loss/frequency response using these biquadratic impedances instead of the original inductors. For bandpass filters the compensation is only approximate. However, for highpass filters, complete compensation can be achieved over the entire frequency range in which the gain of the amplifier can be adequately described by a single-pole model; the cost of achieving this is some increase in sensitivity. The new design procedure has been applied successfully to a 5th-order Cauer-type highpass filter; computed incremental sensitivities and some measured results are presented.

A class of high-Q high-frequency two amplifier active RC network

Abstract: Generalization schemes and illustrative examples are given for a class of high- Q high-frequency two amplifier active RC networks using all-pass circuits with either positive or negative gain constant. In this preliminary study, the \omega_0 and Q degradations of the networks are compared with the state-variable filter. Experimental results for a bandpass filter application are included.

Flame detector for fire alarm system - uses photocell and demodulator to provide flicker signal to evaluation circuit which supplies alarm signal

Abstract: The flame detector circuit, for a fire alarm system, uses a photocell (RF), which provides a signal representing the modulated radiation caused by the flickering of the flames. The photocell (RF) is coupled to a demodulator in the form of an active bandpass filter, for limiting the photodetector signal to a given range, to provide a flicker signal. an evaluation circuit monitors the physical parameters of the flicker signal to provide an alarm signal. The demodulator has a number of low frequency filter devices (V1, V2) between its input (E) and output (F), the first (V1) comprising an operational amplifier (V1) with its non-inverting input connected to a reference potential and its inverting input connected to the photo cell (RF). The filter circuit (V1, V2) is connected to an operational amplifier (V3) which acts as an integrator and provides a feedback to the non-inverting input of the former operational amplifier (V1).

Multiifrequency signal receiving system

Abstract: PURPOSE:To simplify the design and manufacture of the circuit for the multifrequency signal receiving system to receive the signals of many different frequencies, by obtaining the output through an isolator circuit composed through a combination of a modulator which modulates the input signal and a kind of the filter circuit

Noise protection circuit for am stereo cosine correction factor

Abstract: The cosine correction factor of a receiver for compatible AM stereo reception is controlled by the amount of high frequency energy present in the demodulated signal. Large amounts of such energy indicate a low signal-to-noise ratio and cosine correction under such conditions is then not desirable. During periods of excessive high frequency energy, a filter circuit output causes a switching circuit to remove the derived cosine correction factor and cause division of the demodulated signal by a factor of one instead.

Comparison of conventional and minimum inductance filters

Abstract: Minimum inductance filters are generally considered to have more stopband attenuation then the corresponding conventional filters for the same number of coils; however, a rigorous proof of this property has never been published. In this paper, the conventional Cauer type-B elliptic filters, designed with the coil-saving zigzag transformation, are compared with minimum inductance filters designed to meet the same requirements. It is shown that the minimum inductance filter has more stopband attenuation for the same number of inductors.

Frequency band amplifier circuit

Abstract: PURPOSE:To improve the flat property within band as well as the attenuation property outside band with a simple circuit element and structure by having different central frequency for two band amplifiers composed by connecting a filter circuit of a single-peak property to a feedback circuit.

An electrically programmable CCD transversal filter with variable capacitance weight factors

Abstract: A prototype of a CCD programmable transversal filter is described. The tap weights have been implemented by on-chip voltage-controlled variable MOS capacitors. The summation of the weighted tap signals uses a charge-sensing technique. The performance of the filter has been demonstrated by suitable measurements indicating a nonlinear distortion below -45 dB.

Special effects circuit for an electronic organ

Abstract: A special effects circuit for use in an electronic musical instrument, preferably an electronic organ, including a filter circuit having variable bandpass characteristics and a tone source supplying a signal to the input of the filter circuit. The bandpass characteristics of the filter circuit are modified in accordance with a control signal. Upon the occurrence of an input signal, a control circuit provides the filter circuit with the control signal at a random or pseudo-random value. The instrument player may select the source of input signals from a variety of sources within the organ thereby determining the times or frequency at which the control signal changes but the value of the control signal is random or pseudo-random. The tone signal output from the filter circuit has randomly or pseudo-randomly attenuated frequency characteristics and is coupled to standard organ output circuits for audio presentation.

Cascade synthesis of monolithic crystal filters with transmission zeros at finite frequencies

Abstract: This paper describes a method of cascade synthesis to realise filter response, with transmission zeros at finite frequencies, using dual monolithic-crystal filters with bridging and series connected capacitors.