Passive Ladder Research Articles

Grounded Generalized Impedance Converter Based on Differential Voltage Current Conveyor (DVCC) and its Applications

The inductor is a required element in circuit designs and it can be used in many analog circuits such as LC ladder filters, LC oscillators, phase shifter, tuned amplifiers and impedance matching circuitry. Therefore, in recent years, synthetic simulated inductance, frequency-dependent negative resistor (FDNR) that can be used instead of the bulky grounded and floating inductors in passive ladder filters. So, in this paper, a topology for the realization of grounded generalized impedance converter (GIC) is presented. The GIC can also be used in the realization of grounded inductor or FDNR elements depending on the passive component selection. The proposed topology consists of a pair of differential voltage current conveyor (DVCC) and three grounded passive elements, which makes it suitable for integrated circuit implementation. The circuit offers attractive features, such as there is no need to another type active building block, independent tuning of quality factor and central frequency, all grounded passive components, and low passive sensitivities. The circuit performance are depicted through PSPICE simulations, which show good agreement to theoretical anticipation. Some applications are included to confirm the usability of the proposed topology

Fast FPGA-architecture for fan/beam-steering in wave-digital RF aperture arrays

A digital hardware architecture is proposed for computation of filter coefficients of 1st- and 2nd-order 2-D IIR beam/fan filters, which are capable of enhancement of RF plane-waves based on their direction of arrival, therefore having applications in steerable digital beamformers. Fan filters are designed using the WDF realization, which has superior sensitivity and stability properties since it is derived from the original passive continuous-domain prototype LC ladder network with impedance-matched resistive terminations. The orientation of the fan filter, which is determined by the look-direction of the radio beam, can be altered by the WDF coefficients. Custom computing parallel digital architectures are proposed for fast real-time updating of WDF coefficients as a function of beam angle and beam size. These coefficients are computed using algebraic approximation methods resulting in fast digital circuits. Digital designs are implemented on Xilinx Virtex-6 XC6VLX240T FPGA device and tested using on-chip hardware co-simulation. The designs are also synthesized, placed and routed for 45 nm standard cell ASIC technology using freePDK45 library to determine the area utilization, power consumption and the maximum speed of operation.

The Presence of the Fibonacci Numbers in Passive Ladder Networks: The Case of Forbidden Bands [Historical Corner

This paper takes into consideration a number of different ladder networks showing links with the so-called Golden Ratio φ = 1.6180339⋯ , which is embedded into the Fibonacci sequence. Discreteness and periodicity in electronic ladder networks seem to appear as the main features able to include Fibonacci numbers. For instance, in the telecommunication environment, transmission lines can be studied with a given approximation by simplified discrete ladder networks made by a sequence of passive identical cells, such as R-R; R-C; R-L; C-R; L-R; L-C; C-L; directly and electrically coupled each other. In this context, the so called Golden Ratio frequently appears in particular conditions, without a specific reason, at least to our best knowledge, and its presence, so far, still does represent a sort of mystery. © 2014 IEEE.

Electrical Network Functions of Common-Ground Uniform PassiveRLCLadders and Their Elmore’s Delay and Rise Times

In the paper are presented the expressions for all network functions of common-ground, uniform passive ladders having, in general, complex terminations at both their ends. The Elmore's delay and rise times calculated for selected types ofRLCladders have indicated their slight deviation from delay and rise times obtained according to their classical definitions. For common-ground, integrating typeRCladder with voltage-step input, the Elmore's delay- and rise-times are produced in closed-form, both for ladder nodes and points. Furthermore, it is proposed a particular common-ground, uniformRLCladder being amenable to application as delay line for pulsed and analog input signals. For this ladder, the Elmore's delay and rise times relating to their node voltages are produced in a closed-form, enabling thus with the realization of artificial (a) pulse delay line with arbitrarily and independently specified overall Elmore's delay and rise times and (b) true delay line with arbitrarily specified delay time for frequency bounded analog and/or pulsed input signals. In cases (a) and (b), precise procedures are formulated for calculation of ladder length and of all itsRLCparameters. The obtained results are illustrated with several practical examples and are, also, verified throughpspicesimulation.

On Modelling of Two‐Wire Transmission Lines with Uniform Passive Ladders

In the paper we presented new results in incremental network modelling of two‐wire lines in frequency range [0,3] [GHz], by the uniform RLCG ladders with frequency dependent RL parameters, which are analyzed by using PSPICE. Some important frequency limitations of the proposed approach have been pinpointed, restricting the application of developed models to steady‐state analysis of RLCG networks transmitting the limited‐frequency‐band signals. The basic intention of this approach is to circumvent solving of telegraph equations or application of other complex, numerically demanding procedures in determining line steady‐state responses at selected equidistant points. The key to the modelling method applied is partition of the two‐wire line in segments with defined maximum length, whereby a couple of new polynomial approximations of line transcendental functions is introduced. It is proved that the strict equivalency between the short‐line segments and their uniform ladder counterparts does not exist, but if some conditions are met, satisfactory approximations could be produced. This is illustrated by several examples of short and moderately long two‐wire lines with different terminations, proving the good agreement between the exactly obtained steady‐state results and those obtained by PSPICE simulation.

Log-Domain Filter Design Based on Impedance Scaling of LC Ladder Structures

In this paper, a log-domain filter design based on an impedance scaling technique of passive LC ladder structures is considered. To this end a general circuit for the simulation of any kind of two-terminal component, both grounded and floating, is presented. Depending on the kind of filter, the proposed technique can produce implementation advantages by reducing the number of required components. The validity of the approach is demonstrated through the simulation of a fifth-order LC ladder elliptic low-pass filter.

New Current-mode all-pole and Elliptic Filters Employing Current Conveyors

New current-mode high-order all-pole and elliptic filters employing second-generation and third-generation current conveyors are presented in this paper. The synthesis method is based on signal flow graph design of simulating LC passive ladder filters. Simple architectures are obtained along with only grounded resistors and capacitors in our all-pole filter design. Moreover, the numbers of resistors, capacitors and current conveyors in our proposed all-pole filters are equal to the numbers of filter order. The proposed elliptic filter can be designed by only adding floating capacitor to the corresponding nodes as the all-pole filter counterpart. Third-order current-mode Chebychev and elliptic lowpass filters are demonstrated to verify the proposed method.

Effects of transistor nonidealities on high-order log-domain ladder filter frequency responses

The nonideality studies on biquadratic log-domain filters are extended to cover high-order filter deviations. It is shown that the log-domain filter nonidealities can be classically understood as integrator magnitude and phase errors, which also bear direct relationship to the component drifts and parasitic dissipations experienced by their passive ancestors. This insight allows us to apply the well-proven LC ladder nonideality theories to our relatively unexplored log-domain regime. We quantify the high-order log-domain filter deviations due to major transistor nonidealities such as parasitic junction resistances, finite beta, and Early effect. SPICE simulations are performed to verify the results. By promoting physical understandings based on the passive ladder, effective and straightforward compensation schemes are proposed.

Some Prominent Characteristics of the Modified Elliptic Low-Pass Function

A modified elliptic low-pass filter function with progressively diminishing ripples in both the passband and the stopband is proposed and analyzed. The modified elliptic function is realizable by the passive doubly-terminated ladder network for the order n even or odd, thus lending themselves amenable to high-quality low-sensitivity active RC or switched capacitor filters through the simulation techniques. Besides the passive ladder network realization, the modified elliptic function has improved characteristics both in the frequency domain and the time domain as compared with the classical elliptic function. In addition, the modified function exhibits better magnitude sensitivity properties than the classical function.

OTA-C Filters with Finite Zeros

In this paper we present a novel technique for OTA-C filter realizations with finite zeros based on doubly loaded passive ladder networks. Only grounded capacitors are needed; all floating capacito...

Implementations of continuous-time current-mode ladder filters using multiple output current integrators

Three different approaches to designing continuous-time current-mode ladder filters using multiple output current integrators are presented. These approaches are based on simulating node voltages, state variables, or loop currents of passive RLC ladder filter prototypes. Node voltage and state variable simulations yield more compact structures than that obtained using loop current simulation. Possible CMOS implementations are presented and their performance characteristics are investigated using SPICE simulations. Scaled filters, using the constant field scaling law, are found to operate properly at low supply voltages, down to 1.0V.

Current-mode band-pass ladder filters using OTAs

A design method of current-mode (CM) band-pass ladder filters is presented. The proposed method is based on the simulation of the passive RLC ladder networks using current-mode biquad blocks. Three scaled impedance functions are chosen to generate the biquadratic transfer functions. Based on these scaled impedance functions, three CM band-pass filters are obtained and implemented using OTAs. As an example, a sixth-order Chebyshev band-pass filter is designed and simulated using HSPICE.

Ladder decompositions for wideband SI filter applications

Methods for designing switched-current ladder filters for wideband applications are presented. By performing UL-LU and LU-UL decompositions on the z-domain matrix description of a bilinear transformed passive ladder, filter structures are derived which preserve low passband sensitivity even for large relative bandwidths. Derivation procedures are outlined and illustrated by the example of a 5th order lowpass UL-LU filter and a 10th order LU-UL bandpass. The switched-current filters are realised using Euler-type integrators based on S3I cells. A comparison of the properties of different structures demonstrate the advantages of the UL-LU and LU-UL methods.

Studying the effects of mismatching and clock-feedthrough in switched-current filters using behavioral simulation

Mismatching and clock-feedthrough are sources of error in Switched-Current (SI) circuits producing DC offset, gain errors, and harmonic distortion, which cause deviations in SI filter responses in both the passband and the stopband. This paper develops formulas including these effects in the input-output description of filter building blocks to make possible not only a faster prediction of the filter performance levels but also to analyze tradeoffs at the early design stages. The block input-output descriptions have been derived taking into account the real physical realization of these blocks together with simple error models. Using these behavioral input-output descriptions, we have studied the extent of these effects in the performance of two different SI filter realizations of passive LC ladder structures: one using integrators to simulate the signal flow graph (SFG) of the ladder and another based on the use of wave active filter (WAF) structures. Monte Carlo simulations of a filter example are presented and analyzed.

Extended remez algorithms for filter amplitude and group delay approximation

Various Remez-type algorithms for the computation of rational filter functions of a general form are proposed. They allow filter amplitude and group delay functions to be arbitrarily shaped and tapered. Such functions can be applied to predistort for undesirable effects in communication systems such as sine (x), transmission line weighting or distortion due to nonideal components. High-order touch points are introduced as a generalisation of the concept of maximum flatness. They are used to trade off between the amplitude, group delay and passive sensitivity properties of a filter. The high-order touch points can be used directly to design a passive ladder prototype by an iterative algorithm.

Microelectronic switched capacitor filters

An explanation of what switched-capacitor (SC) filters are and how they work is given. Attention is focused on low-sensitivity SC filters, which can be developed from a general passive ladder where the branches are arbitrary impedances. The equations that describe the filter components are reviewed, and the characteristics of these low-sensitivity filters are outlined. Applications of the filters in telecommunications are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

SC simulators of passive two-ports

Abstract A method for synthesizing switched capacitor circuits that simulate passive LC ladder networks is proposed. The circuits are developed by cascading lower order SC active subnetworks which serve the purpose of two port simulators. Experimental results from two circuits that are proposed as examples, are also given.

Linear Phase Emphasis Networks with Gaussian Function

In this paper, a new approach to the practical design and realization methods of linear phase emphasis network, which is applicable to the FM transmission system, is introduced. The methods are based on employing the Gaussian function expressed as a real exponential function exp(P2) realized by the squared amplitude response of a specific two-port passive LC ladder network. They are also based on a time base conversion technique using digital technology which provides a zero phase network.

Linear Phase Networks With Hyperbolic Tangent Function and Their Applications

This paper describes several methods to realize passive and active networks. with linear phase frequency response applicable to the video signal processing circuit especially for the FM transmission system. The methods are based on employing the hyperbolic tangent function realized by using passive LC ladder networks. They are also based on a time base conversion technique which provides the zero phase network. Using these methods, video signal processing circuits with linear phase property such as pre-emphasis and de-emphasis networks for the FM transmission TV system are introduced.

An improved method for the evaluation of filter sensitivity performance

Conventional sensitivity measures are unsuitable to evaluate filter performance. They ignore the difference between ripple increase (a serious degradation of filter performance), and the flat-gain deviation (of much less practical importance). These two aspects of filter performance are taken into account separately in the multiparameter sensitivity indexes proposed in this paper. The new indices are applied in a comparison of active filters obtained by different methods of simulation of passive ladder prototypes.