Flat Group Delay Characteristics Research Articles

A Compact Ka-Band 4-bit Phase Shifter With Low Group Delay Deviation

This letter presents a compact $Ka$ -band 4-bit switch-type phase shifter with low group delay deviation (GDD) using 28-nm CMOS technology. A magnetically coupled all-pass network (APN) configuration is employed to achieve both equal and flat group delay characteristics versus frequency at each phase state. The measured rms phase error is 1.2°, and the gain error is 1.1 dB at 33 GHz. The average measured insertion loss is 12.8 dB at 33 GHz, and the input and output return losses are both lower than −10 dB from 29 to 37 GHz. The fabricated phase shifter has a compact size of 0.08 mm2 excluding pads, low GDD of ±4 ps, and rms group delay error of $Ka$ -band phase shifter has the lowest GDD per bandwidth (GDD/BW) compared with other reported passive phase shifters.

Transition between flat magnitude and flat group delay low pass recursive digital filters

Many a paper has been written on the characteristics of the continuous-time and discrete-time low-pass filters which are designed to have either maximally flat magnitude characteristics or maximally flat group delay responses. The polynomial (all pole) low pass recursive digital filters which are characterised by characterise the transition between a flat magnitude and flat group delay characteristics, named Transitional Butterworth Thiran (TBTh) recursive digital filters, is considered. The characteristics of the resulting filter change gradually from the characteristics of the well known Butterwort's filter to the characteristics of the Thiran's filter with the maximally flat group delay characteristic. Poles of the TBTh filter are obtained by interpolating between poles Butterworth and Thiran's filters by varying a parametar which controls the pole positions that enables a tradeoff between the steepness magnitude characteristic at passband edge and group delay deviation.

Leakage-Reduced Conductor-Backed Coplanar Waveguide With Periodic Structures and its Antenna Application

A simple method is described where the need of via holes is not required to suppress the inherent leakage of a conductor-backed coplanar waveguide (CBCPW). Pairs of slots are periodically etched on the side ground planes in close proximity to the central signal line. When one period of the structure is considered as a coupled-line section, it provides an open-open boundary condition leading to the all-pass frequency response. To further reduce the possible mode conversion caused by the impedance discontinuity, pairs of small patches are loaded inside the slots. Since the self-resonant frequency of the small patches is far beyond the frequency of interest, the impedance seen from the signal line to the small patches is relatively high suppressing the leakage. The proposed leakage-reduced CBCPW transmission lines both possess good insertion/return loss responses, low loss factor, and flat group delay characteristics. The operation frequency range of the proposed structures is up to 45 GHz. Both structures are then integrated with the coplanar patch antenna. It is demonstrated that using the proposed structures as feed lines could not only improve the antenna efficiency but also lower the cross polarization levels of the coplanar patch antenna, which operates at 5.5 GHz. More importantly, the proposed via-free structures would be more suitable for use in microwave and millimeter wave integrated circuits.

Compact ultra-wideband bandpass filter with multilayered structure

A compact ultra-wideband (UWB) bandpass filter using a multilayered structure is proposed.The proposed filter is composed of a pair of parallel plates, a meander line, and a thin conductor column that connects the parallel plates. The fabricated filter has a small size of 5 × 6 × 1.818 mm3 that amounts to 0.19 λg × 0.22 λg × 0.07 λg, where λg is the guided wavelength at the center frequency of the passband (6.95 GHz). UWB bandpass characteristics from 1.9 to 12.0 GHz with two attenuation poles at 0.4 and 12.8 GHz were achieved. Experimental results are in good agreement with the numerical ones that are obtained from a simulation and an equivalent circuit. Flat group delay characteristics in the wide frequency range are also shown. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:557–559, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25816

A novel LTCC multilayer SIW linear phase filter

AbstractIn this article, a novel multilayer substrate‐integrated waveguide (SIW) linear phase filter is proposed. Four SIW cavities are placed in two layers based on a standard low temperature cofired ceramic technology. Neural network is used to improve the efficiency of design. One slot which is etched on the top metal layer of SIW cavity is adopted to suppress the first high mode. Flat group delay characteristics can be achieved in the filter that has a rejection level of −25 dB in upper stopband. The filter has a 55% area reduction in comparison with planar structure. Good agreement is acquired between measured and simulated results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2357–2360, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24595

Synthesis of coherent two-port optical delay-line circuit with ring waveguides

A method has already been reported by the author and others for synthesizing coherent two-port lattice-form optical delay-line circuits which have the same filter characteristics as finite impulse response (FIR) digital filters. This paper proposes a two-port circuit configuration with ring waveguides which can realize the same filter characteristics as infinite impulse response (IIR) digital filters. It also describes a synthesis method for realizing arbitrary IIR filter characteristics with the circuit configuration. This method is based on scattering matrix factorization. Some synthesis examples are demonstrated including an elliptic filter, a Butterworth filter, an optical filter with maximally flat group-delay characteristics, a group-delay dispersion equalizer, and a multichannel selector.

Broad-band matching with maximally flat group delay characteristics

The paper presents a new approach to the design of a broad-band matching network which, when operating between two given terminating impedances, yields a maximally flat group delay characteristic. First, we use the indeterminate coefficients to construct a scattering matrix, and then present a theorem which states that if there exists a set of real numbers such that the scattering matrix satisfies the realizability conditions and the system transmission function possesses the maximally flat group delay characteristic, the problem is solvable. If the equalizer is an all-pole low-pass network, the set of real numbers can be expressed in terms of a normalizing frequency coefficient <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\xi</tex> . The solution is then simplified to that of finding <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\xi</tex> under realizability conditions. The method is simpler and more accurate than that given by Zysman and Carlin using integral restriction and the Appell function.

Cascade Synthesis of Selective Linear-Phase Filters

A design procedure is presented for the realization of selective linear-phase channel filters in a cascade configuration. From the transfer function which exhibits optimum maximally fiat amplitude and linear phase characteristics, synthesis is performed using symmetrical seconddegree transmission zero producing sections which contain frequencyinvariant reactances, and the overall network is constructed with complex conjugate symmetry. Conversion is made to lumped-element bandpass channel filters using the reactance slope parameter method. In all but very narrow bandwidths, dispersion occurs in the bandpass filter, but it is shown that by choosing a dispersive modification to the prototype, flat group-delay characteristics may be recovered in the bandpass filter.

Design of Chebyshev Filters with Flat Group-Delay Characteristics

In this paper, a method for designing Chebyshev filters having flat group-delay characteristics in the main part of the passband is presented. From the general approximation theory, a method for obtaining the transfer function of Chebyshev filters with complex transmission zeros is derived, which are so determined that the group-delay characteristics may be flat in the main part of the passband. A new theory of cascade synthesis, which is an extension of Belevitch's cycle, and an extended bisection theorem are introduced. By the applications of these results, Chebyshev filters with flat group delay can be realized. A practical design example is also included.

A Class of Transfer Functions Having Approximately Maximally Flat Group Delay Characteristics

A Class of Transfer Functions Having Approximately Maximally Flat Group Delay Characteristics

The design of phase-linear intermediate-frequency amplifiers

Data are given for the design of i.f. amplifiers with flat group-delay characteristics for combinations of from one to six tuned circuits. Both staggered-tuned single circuits and combinations of band filters are considered. Figures of merit are calculated and compared with the figures for networks based on flat-amplitude design