Biljana P. Stošić

New CIC Filter Architecture: Design, Parametric Analysis and Some Comparisons

ABSTRACT A new CIC filter architecture, i.e. CIC (cascaded-integrator-comb) FIR (finite impulse response) filter functions, designed by introducing spreading of the delays in the comb stages is presented here. The design forms of modified CIC filters that approximate simultaneously both magnitude and group delay specifications are given. The benefit of the novel filter class is demonstrated by a few example filter functions and their comparisons with existing classical CIC structures and one technique given in the literature. The effect of the compensation filter on the frequency response (reduction of the passband droop) is also shown. The novel cascaded-filter architecture has valuable benefits: wider passband range, higher insertion loss in stopband, as well as smaller values of integer coefficients of the impulse response.

A combined wave digital/full-wave electromagnetic approach used for response calculation in equivalent networks of microwave circuits

In this paper, a combined wave digital/full wave electromagnetic (EM) approach is used to synthesize wave digital networks of microstrip structures with step and capacitive gap discontinuities. The wave digital approach is applied to model uniform transmission lines in these structures, while the full-wave EM tool provides a generalized S-parameter description of discontinuities, used to generate their approximate equivalent network models. In the case of capacitive gap discontinuity in the end-coupled structures, the synthesis procedure is based on equivalent circuit representation by using admittance (J-) inverters and half-wavelength resonators. Wave digital model of J-inverter is formed by use of a two-port parallel adaptor. The combined technique is used for efficient modeling and analyzing of two different types of microstrip band-pass filters.

Using Cascaded Non-Identical CIC Sections to Improve Insertion Loss

A novel class of cascaded-integrator-comb (CIC) filter functions, which preserve the CIC filter simplicity avoiding the multipliers, is proposed in this paper. The proposed class is designed using several cascaded non-identical CIC sections. The paper provides its non-recursive and recursive forms, as well as frequency response. Compared with classical CIC finite impulse response (FIR) filters designed novel class shows excellent performances in term of insertion loss in stopband and selectivity. To verify the behavior of the proposed novel class of CIC FIR filter functions, several illustrative examples are provided. Also, comparisons of the novel filter class with existing classical CIC structures and some recent improvements given in the literature are provided. For the same level of a constant group delay of 31.5 s, a classical CIC filter function has insertion loss of 115.176 dB, and proposed novel filter function has 136.757 dB. It has achieved significant improvement of 21.581 dB or approximately about 20%.

Compact equivalent network synthesis for double-symmetric four-ports

This article describes the properties of a double-symmetric electromagnetic four-port and its decomposition into four one-ports which are subsequently synthesized as lumped element circuits. This allows for a compact lumped element representation of the four-port and, hence, for an efficient analysis using circuit simulators. Methods of system identification and lumped element network synthesis using Foster representation are used.

A wave digital approach in obtaining z-domain functions for microstrip stub-line structures

An efficient method based on transfer parameter approach is proposed to obtain the scattering parameters in z-domain of planar microstrip stub-line structures. A wave digital network (WDN) which represents a digital model of a microstrip stub-line structure is observed here. WDN is composed of cascaded unit elements and three-port adaptors. An open T-resonator realized in microstrip technique, proving the response accuracy of the new technique, is given.

Performances of the novel modified CIC FIR filter functions

Design of novel selective multiplerless Cascaded-Integrator-Comb (CIC) finite impulse response (FIR) filter functions with applications in modern communication systems is presented here. Performance comparisons of the modified CIC filter functions and the classical CIC filter functions through a few design examples are also presented. Novel designed filter functions show substantial performance improvements compared to classical CIC filters. Depending on the chosen filter order, the achieved improvements are from 6.70 % up to 43.44 %.

Extended foster approach for equivalent circuit synthesis of lossy microwave circuits

In this paper, a circuit synthesis approach based on an extended Foster canonical expansion for representation of distributed passive lossy electromagnetic structures is described. Compact lumped element model is extracted from data provided by numerical TLM method in the time-domain and then embedded into a conventional circuit simulator. The equivalent circuit synthesis procedure is applied to the two-port low-pass and band-pass microstrip filters. The resultant circuits with elements are analyzed and the obtained S parameters results are in a good agreement with numerical results.

Innovative design of CIC FIR filter functions

An innovative design of CIC (Cascaded-Integrator-Comb) FIR (finite impulse response) filter functions based on spreading the delays in the CIC filter comb stages is described. The method is given in a closed-form which provides the impulse response coefficients analytically. The benefit of the new filter class is shown through a few example filter functions and their comparisons with existing classical CIC structures and some improvements given in the recent papers. The novel cascaded-filter architecture shows valuable benefits: increased minimum attenuation in stopband, smaller impulse response coefficient values, and decreased passband droop.

Efficient simulation of thin anisotropic conductive materials by using digital filter-based TLM method

In this paper, a digital filter technique is used for an efficient modelling of thin anisotropic conductive materials. Appropriate digital filter is developed to incorporate the scattering parameters of an anisotropic conductive panel allowing to include its presence without the need to model the panel thickness. The filter is implemented in the Z-TLM method. The example of carbon fibre composite material with frequency independent anisotropic electric conductivity is used to verify the accuracy and efficiency of the presented approach.

Wave digital network of parallel-coupled microstrip based on admittance inverter model

Wave digital network of parallel-coupled microstrip resonator filters is considered in the paper. It is based on equivalent circuit representation by using admittance (J-) inverters and half-wavelength (λ/2) resonators. Wave digital model of admittance inverter (J,-90°), developed here by the use of two-port parallel adaptor network, is described in details. Proposed equivalent network allows for efficient analysis of parallel-coupled microstrip circuits.