Traveling-wave Filter Research Articles

How much “villain” is the anti-aliasing filter for traveling wave-based fault location methods?

This paper analyzes the influence of anti-aliasing filters (AAFs) on traveling wave (TW)-based fault location (TWFL) methods. To do so, the Alternative Transients Program (ATP) is used to simulate several fault scenarios on a 230 kV/60 Hz test power system, allowing the assessment of AAFs influence when different TW filters and TWFL algorithms are used. The main goal is to clarify how much “villain” are the AAFs for TWFL methods if their cutoff frequencies are varied in noisy environments. By doing so, the most relevant spectrum band for TWFL solutions is investigated, addressing whether the application of AAFs with reduced cutoff frequencies would be critical or not. Although most people may think that the answer to this question is obvious, the obtained results show evidences that some solutions monitor transients within spectrum ranges wider than those they indeed require. Moreover, although AAFs can relevantly influence the performance of TWFL methods, it is proven that the application of AAFs with reduced cutoff frequencies is not necessarily critical, but rather, it depends on the used TW filters and TWFL methods, such that it can be beneficial when electrical noise is present in monitored signals.

Микрополосковые удвоители СВЧ с нетрадиционной реализацией

Frequency multipliers are used in electronic devices to generate spectrally pure sinusoidal signals in the frequency range from a few to tens of GHz. The multipliers are used to multiply the frequency of highly stable but more low-frequency devices with the subsequent extraction of the necessary harmonics from the frequency spectrum of the received microwave range. The frequencies selected after multiplication (set) have significantly higher energy, spectral and range characteristics, which allows them to be used as local oscillators and synthesizers in receiving and transmitting systems. The authors of this paper theoretically substantiate and practically demonstrate the possibility of an unconventional implementation of a microstrip multiplier of the microwave range based on a directional traveling wave filter. The proposed implementation does not require the use of active semiconductor elements. The well-known circuit and technological principles for the creation of microstrip microwave multipliers are considered in the paper. The features, problems and shortcomings arising from their implementation are analyzed. The effectiveness of using the balanced circuit for frequency multiplication is confirmed. A list of mandatory requirements and conditions necessary for the implementation of the microwave multipliers is given. It is demonstrated that the features of the microstrip travelling-wave filter are identical to the conditions and requirements for the implementation of balanced multipliers. It is shown and substantiated how an unconventional implementation of a passive microwave multiplier is possible due to the electromagnetic interaction of the input and output nodes of such a filter with an annular travelling-wave resonator. Using the example of modifying a block diagram of a directional filter into a multiplier circuit, the possibility of creating a microwave doubler is confirmed by separating a given frequency from the frequency spectrum of a traveling-wave ring resonator.

A CMOS Finite Impulse Response Filter With a Crossover Traveling Wave Topology for Equalization up to 30 Gb/s

This paper describes a fully differential 3-tap finite impulse response filter in 90-nm CMOS. A traditional traveling wave filter topology is modified to alleviate its inherent delay-bandwidth-gain tradeoffs. Each tap gain is comprised of two transconductors whose outputs superimpose with the same group delay, similar to a distributed amplifier. This doubles the bandwidth of the filter for a given tap spacing and gain. Digital control is provided for the tap gains, an integrated pre-amplifier, and tuning varactors. Coupled differential spirals are used in the delay lines to help the design fit into an area 600 /spl mu/m/spl times/500 /spl mu/m. A 1-V supply voltage and 25-mW power consumption are enabled by the use of parallel differential pairs for sign control of the transconductances instead of Gilbert cell amplifiers. The input return loss is better than 16 dB and the output return loss is better than 9 dB up to 30 GHz. Equalization of NRZ data over a coaxial cable channel was demonstrated up to 30 Gb/s, making it faster than any previously reported CMOS equalizer.

A Study on Circular Disk Resonators on a Ferrite Substrate

In this paper, an exact analysis of a circular disk resonator on a magnetized ferrite substrate which can be used for tunable filters and circular polarizing radiators is presented. The method makes use of Galerkin's method applied in the Hankel transform domain and is quite suitable for numerical calculation. The calculated values of the resonant frequencies and unloaded Q's are shown to be in good agreement with the measured data and the validity of the present theory is confirmed. Furthermore, the characteristics of the traveling wave filters are investigated theoretically and experimentally, and their advantages over the standing wave filters are demonstrated in terms of reflection and sensitivity of the Q/sub L/ on the coupling strength.

Frequency Response of Strip-line Traveling-Wave Directional Filters (Correspondence)

Coale analyzed the single resonator strip-line traveling-wave filter shown in Fig. 1 by a perturbation method. Design criteria were formulated relating loaded Q to pertinent circuit parameters. Experimentally it is observed that properly aligned filters exhibit a frequency response which is approximately Butterworth. The purpose of this communication is to show that the approximate frequency response of narrow band-width filters in the absence of dissipation and resonator discontinuities is theoretically Butterworth. Comments on the design problem are included as well as a discussion of the effects of resonator discontinuities.