Showing papers on "Voltage-controlled filter published in 1987"

Design of Filters to Reduce Harmonic Distortion in Industrial Power Systems

Abstract: Shunt filters are effective in minimizing voltage distortion caused by nonlinear loads in industrial power systems. Different alternatives of filter design should be considered before making the final decision on filter configuration. Among the criteria used for performance evaluation are losses, current, and voltage ratings of each of the filter components, and the effect of filter and system contingency conditions. The design and performance of single-tuned and high-pass filters and the methodology used for the analysis will be discussed.

Minimal transistor-only micropower integrated VHF active filter

Abstract: A minimal integrated filter containing four MOS transistors as the only circuit elements is presented. Voltage tuning is used to set the cutoff frequency and band-edge peaking. A filter test chip occupies an active area of 0006mm2, has acutoff frequency of 40 MHz and dissipates 580W.

Filter adjustment apparatus and method

Abstract: Filter adjustment apparatus for adjusting cut-off frequencies or dip frequencies, for example, may be adjusted to desired optimum properties, during application of an input signal of a constant frequency. The optimum filter adjustment data are found, based on data manifested when the level detected output of the filter output crosses a prescribed reference level whereby the filter adjustment operation is simplified and accuracy is improved with a simplified structure, and it is possible to achieve automatic adjustment of the filter characteristics.

Circuitry for converting measurement signals disturbed by a disturbance function into undisturbed signals

Abstract: A filter circuitry for disturbed signals of changing frequencies The disturbed signals are supplied to a first adaptive ladder filter (3) and to a second adaptive ladder filter (5), via a high-pass filter (4) In time intervals determined by a control circuit, during which only the disturbance reaches the second adaptive ladder filter, the parameters for filtering-out the disturbing signals are determined in the second filter, then transferred, if necessary, to the first adaptive ladder filter

Apparatus for stabilizing turbine-generator shaft torsional oscillations

Abstract: OF THE DISCLOSURE An apparatus for stabilizing turbine generator shaft torsional oscillations including: a current detector for detecting ac current of a turbine generator used in combination with a dc power-transmission system, a filter to which an output of said current detector is delivered, the filter comprising a first bandpass filter for detecting a super synchronous component (fl + fm) and a second bandpass filter for detecting a sub synchronous component (fl - fm) where a fundamental frequency of the generator is represented by fl and a natural frequency of the mechanical shaft system of the generator is represented by fm, a calculation circuit for applying conversion of at least one of d and q axis to respective outputs from the first and second bandpass filters using a generator phase .theta.G to take out at least one of .DELTA.id and .DELTA.iq of the sub and super synchronous components, a third bandpass filter to which an output from the calculation circuit is fed, the third bandpass filter for taking out a stabilization signal therefrom, and a circuit for controlling a converter for delivering an output of the generator to the dc power-transmission system on the basis of the stabilization signal.

Microwave multiband filter

Abstract: A multiband microwave filter that can selectively transmit a broadband signal or any discret or combination of predefined frequency bands. The filter has two transmission lines, with an output port at one end of a first one of the transmission lines. A switch selectively transmits an input signal to one of the transmission lines. The filter also has a plurality of narrowband directional filters, each of which is used to transmit signals in a corresonding frequency band from one of the transmission lines to the other. Each directional filter includes at least one diode for enabling and disabling the operation of the direction filter in accordance with a bias voltage applied to the diodes. By controlling the switch and applying appropriate bias voltages to each of the diodes, the microwave filter can selectively transmit a broadband signal or any discret or combination of the frequency bands transmitted by the directional filters.

Method and device for transmitting a digital signal

Abstract: In a transmitter, a digital base-band signal drives a frequency modulator via a pulse-expanding filter. In the receiver, the received signals are fed via a bandpass filter to a frequency discriminator for demodulation. The demodulated signal is filtered in a low-pass filter and passes through a pulse-compressing filter before threshold decoding. A plurality of identical receivers can be connected in such a manner that the bandwidth of the bandpass filter becomes smaller and smaller in successive branches. The pulse-expanding filter has a constant frequency response amplitude and a linearly rising group delay time, while the pulse-compressing filter has a frequency response which is the conjugate-complex of the said filter.

Pre-coat filter

Abstract: In the filter according to the invention (precoat filter), gap filter elements (11) designed in the manner of filter candles are used, which consist of a profile wire wound into a helical spring. To remove the adhering filter cake, the gap filter element (11) is stretched in its axial direction while opening the filter gap, which is expediently carried out by means of a stretching drive, which can also be designed as an oscillating drive. The gap filter elements are set in vibration at the same time, which can be done by periodic stretching and shortening or by the stretched gap filter elements being set in vibration. The oscillating movement is expediently carried out at a frequency adapted to the natural frequency of the gap filter elements.

Data compander for digital video signals

Abstract: The data compander for digital video signals, the sampling frequency of which is coupled to the colour subcarrier frequency, consists of the following part-circuits being connected in series with respect to the signal flow: a filter (k1) for changing the coupling which changes the colour subcarrier coupling of the video signals (vs) into signals, the clock frequency of which is coupled to the line frequency, an (a/b) decimation filter (df), a, b being integral numbers and a being less than b, a first peaking filter (p1), an application circuit (uc) for the line-coupled signals, a (b/a) interpolation filter (ip), a coupling reversal filter (k2) which changes the line coupling of the signals into a coupling of the signals to the colour subcarrier frequency, and a second peaking filter (p2).

Television tuner for three different frequency ranges

Abstract: A television tuner for three different frequency ranges comprises a common antenna connection for three input filter circuits (1, 2, 3). In order to obtain a simple circuit design which involves negligible mutual capacitive loads from the input filter circuits (1, 2, 3), the antenna connection (4) is spatially associated with the input filter circuit (3) for the highest frequency range and is directly connected to one end of a coupling conductor (5). The coupling conductor (5) is series-connected directly with the connection for input filter circuit (1) of the lowest frequency range I and, via a switching diode (11), with the input filter circuit (2) for the medium frequency range II. A further switch (12) detunes the input filter circuit (3) for the highest frequency range III if one of the other input filter circuits (1, 2) is activated.

Spread spectrum communications system

Abstract: In a spread communications systems, a filter is inserted in a transmitter and a receiver, respectively. The filter in the transmitter is an FIR filter and the filter in the receiver has a characteristic inverse to that of the FIR filter.

A low–loss 6–pole canonical dual–mode filter for the output multiplexer of broadcasting satellite transponders in the 12–GHz band

Abstract: This paper describes the development of a filter for the channel multiplexer in the 12-GHz band broadcasting satellite transponder with a high transmitting power (above 200 W). The filter for high-power multiplexer must have a very low loss, to maintain the satellite transmitting power and to secure thermal stability. It was found that the use of a 6-pole elliptic filter is better than that of a 4-pole elliptic filter from the viewpoint of the insertion loss and the heat dissipation. The 6-pole canonical filter is designed using TE113 dual-mode. In the thermal design, super-invar with small thermal expansion coefficient is used for the cylindrical waveguides of the filter, and copper with high thermal conductivity is used for the iris plate. Improving the heat dissipation and suppressing the temperature-rise, the deterioration of the filter characteristics caused by the temperature variation is prevented. The experimental filter realized the insertion loss of less than 0.3 dB, the loss variation of 0.1 dBp-p and group-delay variation of 5 nsp-p within the channel. No significant deterioration of the filter performance was observed through the thermal test of 0°C to 90°C and the high-power test of 200 W. As a result, it was demonstrated that the proposed filter has better electrical and thermal performance than the previous 4-pole elliptic filter, being suited as the filter for the multiplexers in high-power broadcasting satellite transponders.

Device for digitalizing measured signals.

Abstract: In such a device with a band-limiting filter (15, 16, 17), a sample-and-hold element (21, 22, 23) and an analog/digital converter (39) in series connection, the band-limiting filter is designed as a filter with switched capacitances and is connected to a clock signal source (31) of variable frequency. This allows the sampling frequency for the digital processing of the signals to be varied in a simple way.

Filter, phase-measuring device and method for application of said filter

Abstract: The present invention concerns mainly a filter, a phase-measuring device and a method to apply said filter. The main object of the invention is a phase-measuring device. The use of adapted filters (140) enables the increasing of the signal/noise ratio of a received signal. However, if several samples of the signal are sent, each having a different phase, the signal present at the output of the adapted filter at any given instant risks being a mixture of the phase of two successive samples. The use of an odd value filter (141) makes it possible to determine the only instants during which the phase measurement corresponds to the phase of a single sample of the signal. The invention can be applied chiefly to the demodulation, detection or decoding of television and radio broadcasts or phase-modulated data transmissions.

New Q enhancement technique of low pole frequency bandpass filter using single-ended operational amplifiers

Abstract: A new bandpass filter with low pole frequency (ωp) and high selectivity (Q) derived from state variable technique is described. Design equations and sensitivity figures are also presented.

Fiber-Optic RF Filter

Abstract: This paper describes a fiber-optic RF bandpass filter consisting of a multimode fiber cavity. Performance equations are derived and test results are presented. The filter is capable of high Q, low loss operation up to frequencies beyond 10 GHz. It is expected to be useful in a variety of systems applications to reduce noise bandwidths and remove unwanted out-of-band signals.

System for converting analog signals to a discrete representation without aliasing

Abstract: A network of filter elements for transforming an analog signal of infinite bandwidth into a discrete filter space representation having a bandwidth equal to π. In one embodiment the filter network includes Laguerre filter elements. Other embodiments include methods for estimating the values of the amplitudes, frequencies, and phases of the frequency components of the analog signal, for reconstructing an input signal, and correcting for non-ideal filter elements.

Network for multi-way speaker equipment

Abstract: PURPOSE:To realize desired phase and amplitude characteristics with a scale of a small circuit by providing a cyclic filter correcting the phase characteristic of a speaker unit and a noncyclic filter correcting the amplitude characteristic of the cyclic filter. CONSTITUTION:A sampling converter 23 converting a clock frequency of a digital signal inputted from a switch 4 into a lower clock frequency is connected to a low-pass filter 8. D/A converters 24, 25 converting the said low sampling signal are connected to the post-stage of the filter 8. Moreover, the high-pass filters 6, 7 consist of the cyclic filter correcting the phase characteristic of the speaker unit and the noncyclic filter correcting the amplitude characteristic of the cyclic filter. A digital signal whose time base is corrected by delay circuits 26-29 is converted into an analog signal by D/A converters 10, 11, 24, 25 and amplified by amplifiers 14-17 and fed to speakers 18-21.

Complementary filtering technique for subband speech coder design

Abstract: This paper presents a new filtering scheme for splitting speech signals into subbands which results in no aliasing problem when the subband signals are sub-sampled and recombined. The highpass and lowpass filters are an odd-length complementary linear phase filter pair. As a consequence, the highpass filter output can be obtained by subtracting the lowpass filter output from the appropriately delayed input. This produces a factor-of-two reduction in the computation load when compared to the conventional even-length quadrature mirror filter. Another factor-of-two saving in computation load can be gained by using halfband lowpass filters whose every other coefficient is zero. Furthermore, the filters can be designed using well known minimax optimization techniques such as the Remez exchange algorithm and integer programming.

Device for digitizing an analogous signal.

Abstract: To simplify such a device, the band-limiting filter (15, 16, 17) and sample-and-hold element together take the form of a filter which samples analog input values, in particular a filter with switched capacitances of integrated design, the output driver of which is preceded by a further switching element with a capacitance.

Gain control bandpass LCR filter with variable bandwidth

Abstract: A bandpass filter is presented which allows variation of bandwidth while passband gain remains constant. The presented bandpass filter relies on feedforward (as opposed to feedback) to compensate for losses within the bandpass filter. Two feedforward circuits are shown, one a current source and the other a voltage source in series with a resistance.

Single-parameter controlled-variable amplitude change function for digital filtering

Abstract: A single-parameter controlled-variable amplitude change function has been constructed for digital filtering using multiple units of a prototype filter. The limits of variation are discussed. The technique is shown to be useful not only for the reduction of errors in either the pass band or the stop band of the overall filter, but also for varying the cutoff frequency of the overall filter over a wide range. Hardware implementation problems resulting from a wide variation are shown to be overcome by a modular approach.

Synthesis of switched capacitor filters using voltage and charge variables

Abstract: The switched-capacitor filter is distinguished by low temperature dependence and small aging effect. In realizing those features in actual filter implementation, the element sensitivity is a problem. In previous construction of the switched-capacitor filter only the voltages have been considered, which results in limitation of the derived low element sensitivity. In order to improve the circuit with respect to element sensitivity, this paper proposes a construction method using both voltages and charges as the network variables. It is shown first that the basic SC circuit composed of a capacitor and a switch has both the differential-input property with respect to voltage and the differential output property with respect to charge. By applying these properties, four kinds of integrators are derived. It is shown by computer simulation that the proposed construction, permits enlargement of the range of element sensitivity in cases such as scaling the output of the operational amplifier in the leapfrog switched-capacitor filter, which has been known as a filter with low element sensitivity. Integrators in which the effect of parasitic capacitance of the original filter is compensated are also discussed.