Abstract: A description is given of a high-performance fifth-order low-pass switched-capacitor filter operating form a single 5-V supply. The filter uses a fully differential topology combined with input-to-output class AB amplifier design, dynamic biasing, and switched-capacitor common-mode feedback. An experimental prototype fabricated in a 5-/spl mu/m CMOS technology requires only 350 /spl mu/W of power to meet the PCM channel filter requirements. Typical measured results are: a dynamic range of 92 dB; a supply rejection (PSRR) of 40 dB over the entire Nyquist range; and a total harmonic distortion of -73 dB for a 2-V r.m.s. differential output signal. The chip active area is about 3900 mil/SUP 2/.

Abstract: This paper explores in detail the possible approaches to. the design of voltage- or current-controllable linear transconductance elements needed for the design of continuous-time CMOS active filters. The focus of the paper is on circuit configurations, techniques of achieving linearity, and temperature compensation using the controlling variable. Circuit techniques for obtaining small transductance values are outlined. Simulation results are presented.

Abstract: The distortion mechanism in switched-capacitor (SC) filters are considered, and closed-form expression relating switched-capacitors filter distortion to circuit parameters are derived. Design techniques for low-distortion applications are discussed and are applied to a sixth-order experimental filter. The filter design uses a fully differential class A/B op amp with a continuous-time common-mode feedback circuit. Distortion measurements show that for 82-dB dynamic range (relative to noise floor) the total harmonic distortion of 0.02% within the whole 4-kHz bandwidth and 0.07% within 20-kHz bandwidth.

Abstract: Transferal and recursive filter concepts, normally associated with discrete-time applications, are adapted for implementation in the microwave frequency range. Principal focus is on microwave active filter designs that permit realization of wide bandwidths, with microwave transistors used as active elements. A transversal-type and a recursive-type experimental filter, both of which exhibit 9-15-GHz bandpass responses, serve to illustrate aspects of physical implementation, while offering a convenient basis for comparing the two different approaches.

Abstract: In order to realize self-contained analog video LSI, video band switched-capacitor (C) filters, including a two-dimensional filter, have been experimentally fabricated By using 2-/spl mu/m/spl middot/CMOS technology and high-speed/high-precision circuits, an LSI clock rate of 14 MHz, signal swing of 2 V p-p with a single 5-V supply, random noise S/N of 60-70 dB p-p/rms at LSI output, and power dissipation of less than 5 mW per amplifier have been achieved Single-stage cascode amplifiers are extensively used to attain video band speed Neutralization is introduced into fully differential filters to improve their frequency response

Abstract: A simple technique for significantly reducing the effect of the finite gain of amplifiers on the performance of switched-capacitor filters is presented. The effectiveness of this technique has been established by extensive simulation studies. This technique has the potential for simplifying amplifier design and extending the frequency range of switched-capacitor filters by trading gain for bandwidth.

Abstract: A switched bandpass filter includes a plurality of triple tuned bandpass filter sections coupled in parallel between an input and an output terminal and complemented by input and output parallel resonant circuits. Each bandpass filter section includes a switch such as a switching diode by means of which the filter section is either rendered active for passing or inactive for suppressing the frequency band to which it is tuned. Portions of the inactive bandpass filter sections contribute to the resulting frequency response with notches at frequencies outside of the passband of the active filter section. Thus, some components of the inactive bandpass filter sections are reused with the active filter section to gain steep out-of-band rejection slopes. In one embodiment, the switched bandpass filter employs only one switching diode per frequency band and, by reusing two-thirds of the filter components, provides a highly efficient switched bandpass filter arrangement.

Abstract: A novel method of designing higher-order filters using current conveyors (CCs) is presented in which a new type of impedance scaling of LC ladder prototypes facilitates direct incorporation of a class of nonideal simulated inductors and FDNRs in active filter design. The resulting structures are minimum-sensitive and require a very small number of CCs (typically, equal to the number of reactive elements in the passive prototype). Experimental results have confirmed the practical validity of the ideas.

Abstract: A parallel form adaptive pole-zero filter implemented in the frequency domain is presented. This filter can exactly model any proper rational system with distinct poles and it permits direct monitoring of pole trajectories during adaptation so that instability of the filter is easily prevented.

Abstract: A multiplexer has a plurality of bandpass filters coupled through E-plane or H-plane T-junctions to a waveguide manifold. Where the multiplexer has four channels and each filter is a six-pole filter, two triple mode cavities make up each filter. Where each filter is a five-pole filter, one triple cavity and one dual mode cavity makes up each filter. Two band edge channel filters are operated to produce an asymmetrical filter function response, thereby causing extra transmission zeros to be created and improving the selectivity of the filter out of the passband. The multiplexer is designed for use in satellite communication systems and can have a reduced volume and weight when compared to previous multiplexers without any sacrifice in electrical performance.

Abstract: An integrated circuit for filtering signals by having cascaded switched capacitor sampling filters. The circuit includes a transmit section which has an anti-aliasing filter, a core section filter, a highpass filter and an encoder for providing analog-to-digital conversion. Each successive filter is sampled at a lower rate to inhibit anti-aliasing. The circuit also includes a receive section which has a digital-to-analog decoder, an output buffer, a receiver core filter and a power amplifier.

Abstract: An integrator that is useful in forming low pass, band pass, high pass, and band stop filters. The integrator (10) comprises a transconductance amplifier (20) and a capacitor (65) which is connected between the amplifier output terminal and the amplifier ground. When implemented as a monolithic IC, the integrator gain is fundamentally process independent. A ladder structure comprising one or more of these integrators provides high order filtering characteristics without many of the problems associated with conventional filter devices. In addition, the integrator (610) provides stop band zero filter characteristics at the filter output terminal when a capacitor (675) is connected across the differential input terminals of the integrator.

Abstract: An electronic compensation network which allows the analytic and empirical realization of the compensation needed to optimize a system response. The electronic compensation network includes a switched capacitor active filter network; means for selectively changing filter characteristics; and, means for indicating the characteristics of the compensator which produces an optimized system response.

Abstract: An area optimized computer-aided cascade switched-capacitor (SC) filter design program called AROMA is presented. The program contains several user-selectable filter approximation techniques. AROMA permits the user to make tradeoffs between several design parameters such as passive sensitivity, op-amp output voltage swings, clock frequency, and the total capacitance of the filter. The program has default values of the tradeoffs, however, each block in the cascade filter can be modified by the user to meet specific requirements. AROMA incorporates recent results of practical interest to the SC filter designer. The flexible structure of the program allows for easy addition of new results, i.e., refined efficient building blocks, additional filter approximations, etc. It can be used by the novice as well as by experienced designers. Furthermore, the program is user-oriented. It can start, in its simplest mode, with a set of frequency specifications. The output gives a circuit description file that can be layed out by an analog circuit layout generator program. Examples illustrating the practicalness of AROMA are given.

Abstract: A multiplexer samples multiple analog waveform signals to provide a sequence of input signals to an active low-pass filter. The bandwidth of the filter is determined by an input RC network having series resistance and shunt capacitance elements. As the multiplexer switches state to sample a different analog signal, the resistance elements of the filter are temporarily shorted to allow the filter input signal to rapidly charge or discharge the shunt capacitance element to a steady state voltage in response to any change in input signal voltage. The resistance elements are then unshorted to permit normal low-pass filter operation. Switch means are also provided to selectively disconnect the shunt capacitance element from the network when the resistance elements are shunted, thereby selectively widening the bandwidth of the filter to pass higher frequency input signals.

Abstract: The variable switched-capacitor filter (VSCF) comprises an input terminal (101), an output terminal (104) and first and second variable switched-capacitor filter blocks (102 and 103, resp.) each having a plurality of capacitors. In each of the filter blocks (102, 103) at least one of the filters is selected in response to a control signal for changing the filter characteristic based on the selected capacitor or capacitors. A first switch (SA) delivers during a first state a first output signal from the first variable switched-capacitor filter block (102) to the output terminal (104), and during a second state, prohibits the first output signal from reaching the output terminal (104). The function of the second switch (SB) is essentially opposite to that of the first switch (SA). The selection of at least one capacitor in the first and the second variable switched-capacitor filter block (102 and 103, resp.) is performed during the second and the first state, respectively. The VSCF accomplishes automatic line equalization without being affected by waveform distortions which result from switching the filter characteristic.

Abstract: Fully differential switched-capacitor (SC) analogue blocks are shown to be suitable for implementing SC ladder filters via the bilinear transform of the corresponding analogueRLC passive prototypes. These filters become fully insensitive to parasitic capacitance effects, while the interesting features of the differential implementation, i.e. power supply and common mode rejection ratios and dynamic range improvements, are retained. The technique presented is useful for the exact design of wide-band SC filters, i.e. for filters with a small ratio between the clock frequency and the cut-off frequency. As an example, the bilinear design of an 8th-order Cauer bandpass filter is given, with numerically computed results.

Abstract: Introduction to Active Filters Approximation The Second Order Function Active Components Analysis of Active Filters Sallen and Key Filters Multiple-Loop Feedback Filters Biquads I: The State-Variable Structure Biquads II: The Current Generalized Immittance (CGIC) Structure Design of High-Order Active Filters Practical Limitations of RC-Active Filters Computer Programs Design Aids Index Author Index Subject Index Name Index.

Abstract: Experimental results of a switched capacitor (SC) N-path filter integrated in a CMOS Si-gate technology are reported, with N=6. The circuit is based on the theory of wave-flow networks and uses only fully stray-eliminating (usually referred to as stray-insensitive) SC amplifier and integrator circuits. The two main drawbacks of N-path filters, i.e. unwanted mirror frequencies due to path mismatch and clock feedthrough located in the passbands, as solved by multiplexing large filter parts and by using a third-order high-pass reference filter, respectively. The integrated six-path filter features low power consumption due to the use of dynamic amplifiers.

Abstract: A new class of integrated circuits called charge-domain device has been developed for performing enhanced monolithic signal processing. All signal-processing operations are accomplished by splitting, routing and combining charge packets, thus overcoming many of the limitations of alternative devices such as charge-coupled device (CCD) split-electrode transversal filters and switched capacitor filters. Charge manipulation techniques are described which allow poles as well as zeros of a transfer function to be implemented efficiently, leading to infinite impulse response monolithic filters suitable for high-frequency applications. Several test filters, including a narrowband 8-pole bandpass filter, are demonstrated. These charge-domain devices are useful in applications ranging from radio IF to radar to video signal processing with a high level of integration achievable on a single charge-domain integrated circuit.

Abstract: In FM transmitters, particularly land mobile FM transmitters, wherein a speech signal is pre-emphasized between 300 Hz and 3 kHz, whereafter it is filtered to provide a sharp cut-off and wherein the maximum peak frequency deviation is limited in order to maintain channel integrity, the level of undistorted speech can be raised to within 90% of the transmitter peak deviation by directly connecting an amplitude limiter to a filter amplifier which behaves as a level sensitive filter when the speech signal has been limited and prevents ringing and overshoot from occurring. The output from the filter amplifier is coupled to a low pass filter, typically a fourth-order Butterworth filter, via an attenuator which reduces the amplitude of the signal to prevent the onset of further clipping.

Abstract: A broadband microwave recursive filter that provides sharp transitions in the frequency domain between adjacent stop and passbands comprising a signal input node; a signal output node; a filter circuit connected between the signal input node and the signal output node for providing a signal flow therebetween which has a predetermined frequency bandwidth characteristic; a microwave transistor circuit, with the microwave transistor circuit being band-limited to provide gain in only a restricted window of frequencies within the predetermined frequency bandwidth and connected for providing amplification to signals flowing in the filter circuit between the signal input node and the signal output node while suppressing out-of-window signals resulting from design approximations. The filter circuit includes a plurality of distributed feedback loop circuits, with each of the feedback loop circuits including the microwave transistor circuit therein, and wherein each of the feedback loop circuits has a different electrical length in relation to the other of the plurality of feedback loop circuits. Finally, the present filter design includes a passive filter connected in common to all of the plurality of distributed feedback loop circuits in the filter circuit for circuit for providing filter zeros on both sides of the restricted window of frequencies. In a preferred embodiment, the microwave transistor circuit includes an FET which is impedance-matched to obtain an approximately flat gain response across the window. It is preferred that the plurality of feedback loops all have amplitude weighting factors of the same sign.

Abstract: An information reproducing apparatus for tracking control has a high-pass filter and a low-pass filter of closed loops connected in parallel to each other and has a storage quantity control circuit which controls an input signal of the high-pass filter in response to a defect detection signal which detects a defective portion of an information recording medium and is outputted from a defect detection circuit. The storage quantity of a capacitor included in the high-pass filter, or of a storage element operable equivalently to the capacitor, is equal to the storage quantity when the high-pass filter is fed a signal having previously been fed to the high-pass filter but without its high frequency component. Even when a speed error is created in an actuator due to pulse-like noises caused by a delay in the defect detection caused by the defect detection circuits, the speed error is removable just after the defect is detected, thereby obtaining the effect such that the tracking control is not so easily disturbed by the defect and operates stably.

Abstract: The study focuses on the application of transversal and recursive principles to the design of broadband active filters for microwave frequencies, employing microwave transistors as active elements. Physical implementation of these concepts is illustrated with a transversal-type and a recursive-type experimental filter. To offer a convenient basis for comparison, both examples are chosen to provide 9-to-15-GHz bandpass responses.

Abstract: An active biquadratic notch filter having first integrating circuitry for providing a first integration signal and further having second integrating circuitry responsive to the first integration signal for providing a filter output. The first integrating circuitry includes at least one operational amplifier. The notch filter further includes compensation circuitry for compensating the limitation on notch frequency attenuation resulting from current lag introduced by the at least one operational amplifier of the first integrating circuitry.

Abstract: A multi-output second-order digital filter without zero-input, constant-input, and forced overflow oscillations is presented. The filter structure can be used for the simultaneous realization of low-pass, high-pass, band-pass, band-stop, all-pass, and general biquadratic transfer functions using two delays, four multipliers, and eleven adders.

Abstract: A filter integrated circuit (1) having a reference level generator circuit (4) for attenuating its input signal and generating a reference level signal, a pseudofilter circuit (5) including resistors (17, 18) and a variable capacitor (19) as filter elements, and an error amplifier unit (6, 7, 8) for comparing the level of the output signal of the reference level generator circuit with the level of the output signal of the pseudofilter circuit and for generating an automatic adjustment control signal (9) in accordance with the level difference between the output signals. The automatic adjust- . ment control signal is supplied to the pseudofilter circuit to change the capacitance value of the variable capacitor in the pseudofilter circuit so that the output signal level of the pseudofilter circuit may become equal to the level of the reference signal. The automatic adjustment control signal is also supplied to at least one filter circuit (11, 12) to change the capacitance of a variable capacitor (32, 33) included therein. As a result, the deviation in the filter characteristics caused by deviations in the resistance of a resistor (30, 31) and in the capacitance of the capacitor is corrected.

Abstract: A new approach is presented for the design of linear-phase anti-aliasing filters. These filters consist of an approximately linear phase analog filter cascaded with a linear phase nonrecursive digital decimator. The use of the decimation part enables us to use a higher sampling rate after the analog part. This increases the required transition bandwidth of the analog filter and, consequently, decreases the required filter order. The passband variation of the group delay response of the analog part is minimized subject to the given amplitude requirements. The optimization is done by an efficient iterative algorithm constructed using recent advances in constrained minimax optimization. As a decimator, we use a filter consisting of two parts, one working at the higher sampling rate and the other one at the final sampling rate. This filter requires significantly fewer multiplications per output sample than a conventional FIR decimator. Examples demonstrate that by oversampling by a factor of 3, a third order analog filter is sufficient to construct an extremely linear phase highly selective anti-aliasing filter meeting the same amplitude specifications as a seventh order purely analog elliptic filter.

Abstract: The design of an input filter for the six-pulse bridge rectifier is discussed. For industrial applications of mid-range power, two types of input filter are examined. It is shown that these filters with minimum number of components can meet most operational requirements if designed properly. The variation of performance factors with filter type and parameters are discussed. As the ultimate decision in selecting the filter components depends on the type of application, the design guidelines are described. The materials for custom designing of the filter are included. The features and advantages of each type of filter are outlined. For comparison purposes, several design examples are also included.