Produce Transmission Zeros Research Articles

Microstrip dual‐band bandpass filter using slow‐wave resonators for WLAN applications

AbstractA dual‐band bandpass filter using microstrip slow‐wave resonators is developed for wireless local area network applications. The fundamental and higher order resonant harmonics of a microstrip open‐loop resonator are analyzed against the length of the loading open stub. Then a dual‐band bandpass filters is designed in the form of slow‐wave open‐loop resonators. A zero‐degree feed structure is employed to produce transmission zeros near the passband to increase the rate of attenuations, and a quarter‐wavelength feed line for impedance matching is added to get desired external quality factor at the input and output. The theoretical analysis and design procedures are successfully verified by experimental results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 14–16, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22055

Synthesis and realization of ultra‐wideband bandpass filters using the Z‐transform technique

AbstractA modified synthesis theory using the Z‐transform technique is presented to design and realize ultra‐wideband (UWB) bandpass filters. Instead of using a system function based on lumped‐element prototypes, a transfer function based on distributed transmission lines is employed to synthesize the filter. In order to get sharp attenuations of the filter, shunt two‐section open‐circuited stubs are employed to produce transmission zeros. A 3° UWB filter is designed and implemented in the form of microstrip lines, and the measured characteristics show good agreement with the theoretical results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1398–1401, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21677

A novel compact interdigital bandpass filter using multilayer cross-coupled folded quarter-wavelength resonators

In this letter, a novel compact cross-coupled interdigital bandpass filter (BPF) is developed. By using multilayer folded quarter-wavelength resonators, the size of the filter is reduced greatly, meanwhile a cross-coupling is introduced to produce transmission zeros and thereby improve the stopband characteristics of the filter. As an example, a four-pole BPF centered at 2.25GHz with a fractional bandwidth of 31% is designed, fabricated, and measured. The simulated and measured results show an excellent agreement.

Cross-coupling in coaxial cavity filters-a tutorial overview

This paper presents a tutorial overview of the use of coupling between nonadjacent resonators to produce transmission zeros at real frequencies in microwave filters. Multipath coupling diagrams are constructed and the relative phase shifts of multiple paths are observed to produce the known responses of the cascaded triplet and quadruplet sections. The same technique is also used to explore less common nested cross-coupling structures and to predict their behavior. A discussion of the effects of nonzero electrical length coupling elements is presented. Finally, a brief categorization of the various synthesis and implementation techniques available for these types of filters is given.