Design of hexagonal filter with source-load coupling

A method for synthesising a novel hexagonal filter with source-load coupling is presented. The equivalent circuit of the lowpass prototype of a general lossless coupled resonator filter is proposed, and the corresponding transfer function t(s) is derived. A novel quasi-elliptic function microstrip hexagonal filter is designed and fabricated. Simulated and measured results are presented. Compared with the conventional cross-coupling filter, the proposed hexagonal filter acquires more than 27.5% size reduction and provides improved selectivity by a relatively small bandwidth     

Dual-band bandpass filter with source-load coupling

A compact dual-band bandpass filter is presented for wireless LAN applications. Using two centrally-loaded stepped-impedance resonators, the second passband frequency can be conveniently tuned. Two transmission zeros are generated between the two passbands because of source-loading coupling topology. Simulated results show that two central frequencies are located at desired 2.4 and 5.7 GHz with 3 dB fractional bandwidths of 18.8 and 7.1 , respectively. Comparison of measured and simulated results shows good agreement.     

Design of microstrip bandpass filters with multiorder spurious-mode suppression

This paper proposes a bandpass filter design method for suppressing spurious responses in the stopband by choosing the constitutive resonators with the same fundamental frequency, but staggered higher order resonant frequencies. The design concept is demonstrated by a four-pole parallel-coupled Chebyshev bandpass filter and a compact four-pole cross-coupled elliptic-type bandpass filter. Each filter is composed of four different stepped-impedance resonators (SIRs) for which a general design guideline has been provided in order to have the same fundamental frequency and different spurious frequencies by proper adjusting the impedance and length ratios of the SIR. Being based on knowledge of the coupling coefficients and following the traditional design procedure, the resultant filter structures are simple and easy to synthesize. The measured results are in good agreement with the simulated predictions, showing that better than -30-dB rejection levels in the stopband up to 5.4f/sub 0/ and 8.2f/sub 0/ are achieved by the Chebyshev and quasi-elliptic filters, respectively.     

Design of microstrip highpass filters with complementary split ring resonators

An accurate equivalent circuit model and the parameter extraction method are presented for the microstrip line with a complementary split ring resonator. A highpass filter with steep rejection slope is designed based on the model. Numerical simulation and measurement confirms the efficient analysis and design procedure and the validity of the highpass filter configuration     

Cross-coupled microstrip hairpin-resonator filters

A new class of cross-coupled planar microwave filters using microstrip hairpin resonators is introduced. The realization of bath the canonical and the cascaded quadruplet (CQ) filters is feasible. Coupling characteristics of four basic coupling structures encountered in this class of filters are investigated in the light of full-wave electromagnetic (EM) simulations. A four-pole cross-coupled filter of this type is designed and fabricated. Both the theoretical and experimental performance is presented     

Pseudo-elliptic microstrip line filters with zero-shifting properties

The paper presents a new design of pseudo-elliptic microstrip line filters. These filters employ a coupling scheme which allows shifting of transmission zeros from one side of the passband to the other by only changing the resonant frequencies of the resonators. To demonstrate the performance of these filters, a fourth-order bandpass filter with one transmission zero in the upper stopband is first designed. A second filter with a transmission zero in the lower stopband is then designed by simply adjusting the lengths of the resonators followed by minor optimization to account for the fact that the resonant frequencies can not be changed without slightly affecting the coupling coefficients in the used layout. Measured and simulated results are presented.     

Cross-coupled microstrip band reject filters with non-resonating nodes

A new design of cross-coupled band reject filters in microstrip technology is presented. In the proposed model, the source and the load are not directly coupled. Instead, non-resonating nodes (NRNs) are introduced in the network to generate the required number of attenuation poles and modularize the design. Higher order band reject filters are designed by cascading lower-order building blocks with NRNs inserted between them. A fourth order filter is designed, built and measured. Good agreement between theory and measurement is achieved.     

基于分形理论的高低阻抗线低通滤波器

提出了具有分形形状的高低阻抗线低通滤波器,仿真结果表明,与传统的高低阻抗线低通滤波器相比,其通带性能得到了巨大的改善,其良好的通带性能是由于分形形状微带线的宽度阶梯渐变减弱了其电流不连续性.为了验证所提出方法的有效性,设计、加工、测量了一组不同迭代次数的分形高低阻抗线低通滤波器,结果表明,高低阻抗线低通滤波器通带内反射损耗的最大值由-17.8 dB降低到-28.6 dB,而其它性能并不因此而改变.     

Sharp-rejection microstrip bandpass filters with multiple transmission zeros

A simple design of a sharp-rejection microstrip bandpass (BPF) filter is presented. By creating multiple transmission zeros in the lower and upper stopbands, sharp rejection characteristics are obtained. The basic filter unit consists of a single parallel coupled-line section and an open-ended stub. A lossless transmission line model approach is used to derive the design equations for frequency responses and transmission zero positions. The bandwidths are controllable by the zero locations that in turn are controlled by varying the impedances of the configuration. To validate theoretical predictions, two prototype BPFs operating at lower band 2.4 GHz of WLAN are fabricated in microstrip form.     

An implementation of harmonic-suppression microstrip filters with periodic grooves

In this paper, a new parallel-coupled-line microstrip band pass filter (BPF) improving the harmonic suppression performance of the second harmonic signal (2f/sub o/, twice the passband frequency) is described. It is found that the desired passband performance is improved and the harmonic passband signal is diminished by enforcing the consecutive patterns in coupled-line and increasing the number of grooves to the optimum values. The recalculation of design parameters such as space-gap between lines, line widths and lengths is not required due to the simple modification of the conventional filter by inserting periodic patterns. To evaluate the validity of this novel technique, order-3 Butterworth BPF centered at 2.5 GHz with a 10% fractional bandwidth (FBW) and order-5 Chebyshev BPF centered at 10 GHz with a 15% FBW were used. When five and three square grooves are used, over 30-dB suppression at second harmonic signal is achieved in simulation and experiment. Finally, the comparison between the characteristics of filters with square and semicircular periodic grooves has been carried out by using the simulated results.     

Parallel coupled microstrip filters with suppression of harmonic response

Corrugated coupled microstrip lines are proposed to design planar microwave filters with suppression of spurious response at twice the center frequency (2f/sub o/). The corrugated structure is designed to equalize the phase velocities of the two eigenmodes in the propagation direction. The designed bandpass filters have a wide upper stopband with satisfactory attenuation levels. In addition, the symmetry of the passband response is improved. Measured results of two fabricated circuits show that the idea works very well.     

Spectral-domain analysis of submillimetre-wave microstrip filters

We consider the cut-off frequencies of high-order modes in boxed submillimetre-wave microstrip filters. It is shown that many of the filters in use at the present time are not cut off in the way that the designers imagine. It is also shown that for ease of manufacture the height of the microstrip channel should be 0.7 times the width and the thickness of the quartz substrate should be 0.5 times the width. This optimum geometry suggests that the upper frequency limit of conventional waveguide components is 1THz.     

Design of transversely fed EMC microstrip dipole arrays includingmutual coupling

Design techniques and procedures for microstrip dipole arrays transversely fed by proximity coupled microstrip lines are presented. Two design equations which include the effects of mutual coupling are developed, and the corresponding design curves are obtained by a rigorous integral equation solution. A seven-element standing wave linear array is designed to illustrate the developed design procedures. The design data are checked by a complete integral equation solution of the array, with good agreement. The measurements of radiation pattern and input impedance are found to be in good agreement with the design goal     

Novel compact parallel-coupled microstrip bandpass filters with lumped-element K-inverters

Novel compact parallel-coupled microstrip bandpass filters are proposed by using additional lumped inductors to realize K-inverters between coupled-line sections to achieve an equivalent to the quarter-wavelength (/spl lambda//4) resonator filters. As a result, the filter order can be doubled without increasing the circuit area, and no repeated passband is observed at twice the center frequency. In addition, by introducing the cross-coupling effect, two transmission zeros at upper and lower stopbands may be created. Simple equivalent-circuit models are also established as effective design tools. Specifically, several compact fourth-order microstrip bandpass filters with good stopband rejection are implemented and carefully examined.     

Accurate synthesis of inline prototype filters using cascadedtriplet and quadruplet sections

A general method for designing low-pass prototype networks with cascade inline topology is presented. The generalized Chebyshev characteristic is imposed, allowing an equiripple response in the passband and transmission zeros arbitrarily displaced in the complex plane (symmetry with respect to the imaginary axis is, however, required). A computationally efficient method is employed for evaluating reflection and transmission polynomials, given the transmission zeros; then, the synthesis of a starting coupling matrix is performed using one of the methods available in the literature. The desired inline topology is then assembled by cascading elementary building blocks (triplets and/or quadruplets), following specific rules which assure the feasibility of the structure; finally, the synthesis is performed by applying a multiple similarity transform to the starting coupling matrix (the set of rotation angles is determined by means of an efficient and fast optimization procedure). Examples are reported which validate the proposed synthesis procedure     

HTS microstrip matching networks and filters

High-temperature superconducting (HTS) YBCO microstrip bandpass filters and microstrip impedance matching networks were fabricated, tested and compared with the predicted performance. Vector corrected measurements of these circuits were performed at cryogenic temperatures. Comparisons of the insertion loss for the HTS and corresponding Au filters are presented, as well as the predicted noise figure for the low-noise amplifiers using HTS and Au matching networks     

High-Selectivity single- and dual-resonator microstrip filters

New selective properties are revealed of the base section of conventional microstrip filters with circuits based on a four-wire system of coupled quarter-wave lines with one half-wave hairpin resonator. The conditions under which this single-resonator section acquires the characteristics of multi-resonator circuits due to the possibility of formation of four zeros and six operating attenuation poles at the end frequencies are determined. The structure does not contain elements short-circuited to the screen, which determines its high manufacturability. It is demonstrated that high-selectivity compact microstrip filters can be designed on the basis of single- and dual-resonator structures, i.e., the structures with the minimum number of resonators.     

LTE频段平行耦合微带线带通滤波器设计

为克服集总元件滤波器在高频下产生的寄生效应,基于ADS(Advanced Design System)软件设计一款适用于LTE(Long Term Evolution)2.6 GHz中国移动频段的微带线带通滤波器,详尽描述滤波器的参数配置、原理图仿真及优化、PCB(Printed Circuit Board)版图仿真及优化等。测试结果表明,此滤波器带内插入损耗小(<2 d B)、矩形系数低,满足设计要求。     

Wide-band microstrip antenna with an H-shaped coupling aperture

Theoretical and experimental results of a wide-band planar antenna are presented. This antenna can achieve a wide bandwidth, low cross-polarization levels, and low backward radiation levels. For wide bandwidth and easy integration with active circuits, it uses aperture-coupled stacked square patches. The coupling aperture is an H-shaped aperture. Based on the finite-difference time-domain method, a parametric study of the input impedance of the antenna is presented, and effects of each parameter on the antenna impedance are illustrated. One antenna is also designed, fabricated, and measured. The measured return loss exhibits an impedance bandwidth of 21.7%. The cross-polarization levels in both E and H planes are better than 23 dB. The front-to-back ratio of the antenna radiation pattern is better than 22 dB. Both theoretical and experimental results of S parameters and radiation patterns are presented and discussed     

Narrow-band microstrip bandpass filters with low radiation lossesfor millimeter-wave applications

Microstrip lines are attractive for the lower millimeter-wave ranges, but use of relatively thick substrates would be desirable in order to minimize losses. On such substrates the usual types of microstrip narrowband bandpass filters (formed from, e.g. coupled line segments with open ends) tend to radiate strongly giving very poor performance. It has been found that a grating technique initially developed for use with dielectric waveguides can be adapted for microstrips to obtain narrowband millimeter-wave microstrip filters with little radiation and strong filter characteristics. The stopbands are broad, the second passband occurring at three times the frequency of the first passband. These filters use parallel-coupled gratings with a single grating in cascade at each end. The modifications to the dielectric waveguide filter theory that are necessary for use with microstrips are detailed. Experimental results from microstrip realizations, which demonstrate their potential for millimeter-wave microstrip applications, are also presented