A New Class of Reconfigurable Microwave Bandpass Filters

A distributed network prototype is presented that enables the design of a new class of reconfigurable bandpass filters. The design procedure is based on the application of a classical synthesis technique. The passband of the filters are reconfigured by simply open or short circuiting the ends of its resonators. The filters exhibit constant bandwidth and passband shape as they are reconfigured. The performance of implemented filters agrees with the presented theory.     

新型紧凑型带通滤波器的设计

文章设计了两个通带位于超宽带低频范围的带通滤波器,用一种T型结构来代替传统带通滤波器中的四分之一波长传输线,这种替代减小了滤波器的尺寸.而且,可以很方便的控制位于滤波器通带两端的传输零点,即合理的调节开路支线的电长度,进而可以方便的控制滤波器的通带范围.为了证明以上新型滤波器的优点,设计了两个开路支线电长度不同的带通滤...     

Predistortion techniques for increasing the element tolerances in equiripple passband niters revisited

A well established technique to increase the element tolerances in the design of selective passive filters, or to decrease the adverse effect of limited gain-bandwidth product of operational amplifiers is to use transfer function with a special type of magnitude response for which the passband ripple amplitude decreases with increasing frequency. Recently various techniques have been reported to construct this type of filtering functions but they are either entirely numerical or, at least, require numerical optimization of some relevant parameters. In this paper, an exact method is proposed to find the explicit expression for the predistorted characteristic function of these filters applicable to both polynomial filters and filters with finite attenuation poles of any degree. The ratio of the magnitudes of the first passband ripple to the last passband ripple can be prescribed in advance, according to the required specifications.     

A new method for the design of IIR filters with flat magnitude response

This paper presents a new direct design of infinite-impulse response (IIR) filters with a flat magnitude response in both passband and stopband (Butterworth filters). The design specifications are passband and stopband frequencies and passband droop and stopband attenuation. The approach is based on an allpass filter with flatness at frequency points /spl omega/=0 and /spl omega/=/spl pi/. Depending on the parity of the IIR filter order, the allpass filter is either real or complex. However, in both cases, the resulting IIR filter is real.     

Novel droop-compensated comb decimation filter with improved alias rejections

This paper presents a novel two-stage comb decimator with the improved magnitude characteristic. Simple multiplierless corrector filters, which are designed using the frequency sampling and IFIR methods, are introduced. The proposed filters compensate the comb passband droop in the wideband passband region and increase the attenuations in the folding bands. Using the multirate identity the filters may be moved to a lower rate. The filter design depends only on the number of the cascaded comb filters and do not depend on the decimation factor M.     

Design of some 2-D filters through the transformation technique

The transformation technique is a powerful tool for designing 2-D FIR filters. However, it is not useful for the design of specially shaped filters with passband/stopband regions not centred around the origin. The authors extend this technique to design two types of filters. A notch filter has a stopband centred about a small region in the 2-D frequency plane. The authors propose an extension to the transformation technique with the windowing concept to achieve the design of notch filters. A directional filter has a passband extending fully along a straight line passing through the origin. The transformation technique is further extended to yield such directional filters. Design and application examples for both these filters are also presented     

Wide-stopband chirped fibre moire grating transmission filters

Efficient, wide-stopband fibre transmission filters with single narrow transmission bands produced using multiply exposed chirped fibre grating resonators are reported. Tailored combinations of these structures with additional chirped gratings have achieved single passband transmission with an effective finesse of 48. This demonstrates the feasibility of fabricating all-fibre transmission filters with arbitrary passband/stopband combinations     

Least-mean-square (minimum integrated power loss ratio) lowpass filters with a pair of imaginary-axis zeros

If power is the main interest, then a class of filters with minimum integrated power loss ratio in the passband offers higher cutoff rate than the well known Butterworth filters. A technique is described to improve the cutoff rate further by introducing a pair of imaginary axis zeros, while the integrated power loss ratio in the passband is still kept at minimum. Other advantageous performances of the filters are also indicated.     

A simple and effective method for microstrip dual-band filters design

A new type of novel low loss dual-band microstrip filters using folded open-loop ring resonators (OLRRs) is presented in this letter. Both magnetic and electric coupling structures are implemented to provide high performance passband response. The first passband and second passband of the designed dual-band filter can be easily and accurately shifted to a desired frequency band by adjusting the physical dimensions of OLRRs. Finally, the 2.4-GHz/5.7-GHz and 2.4-GHz/5.2-GHz dual-band filters are illustrated and measured in this letter.     

Planar three-resonator bandpass filters with cross coupling

New designs of planar three-resonator bandpass filters with cross coupling having a large variety of frequency characteristics are considered. In addition to better one-sided selectivity, such filters implement symmetric amplitude–frequency characteristics with an attenuation pole at each side of the passband. These filters can also have constant delay time in the passband. Concatenation of the proposed three-resonator filters leads to multiresonator filters with high selectivity determined by two attenuation poles at each side of the passband. It is found that the type of connection of the middle resonator in the circuit of a three-resonator filter with cross coupling results in substantial differences in amplitude–frequency characteristics. The results of modeling of different frequency characteristics are presented. It is shown that filters have small dimensions, which are comparable to overall dimensions of microwave ceramic filters. For example, dimensions of a three-resonator stripline filter designed for a frequency of 1.9 GHz are 9.4 × 5 × 2 mm for the permittivity of the filter material ε_r = 92 and dimensions of a six-resonator filter are 10 × 9.4 × 2 mm.     

Coplanar waveguide edge-coupled bandpass filters with finite groundplanes

Finite ground plane coplanar waveguide edge-coupled bandpass filters which have no parasitic passband and low insertion loss are demonstrated. Two 5-section filters centred at 10 GHz with a 15% bandwidth with identical design parameters but different ground plane widths; are fabricated on alumina substrate; the measured passband insertion loss is <1.5 dB. The filter with wider ground planes has higher attenuation in its stopbands     

Selective filters using least-mean-square approximation technique

A new clan of all-pole lowpass filters having a flat magnitude characteristic at the origin and at a frequency ?0 in the pass-band is presented. The remaining degree of freedom is used to minimise the characteristic function over the passband using least-mean-square norm. It is shown that the magnitude characteristic of new filters is superior to those for the Butterworth and transitional Butterworth-Cheby?shev filters, both in the passband and in the stopband.     

人造卫星用差接桥型压电陶瓷滤波器

介绍了人造卫星用７０．５ｋＨｚ和９４．５ｋＨｚ差接桥型压电陶瓷滤波器的设计原理和试验结果。该滤波器的主要特点是通带宽且平坦、波动小、插损低和性能优良     

Least-squares monotonic lowpass filters with sharp cutoff

A new class of lowpass-filter functions with no finite zeros and a monotonic magnitude response is first derived by using a least-squares norm to minimise the passband attenuation, and these filter functions are then augmented by adding one pair or multiple pairs of j?-axis zeros. The magnitude characteristics of these filters are compared with those of the generalised inverse Cheby?shev filters and are found to be superior, both in the passband and in the stopband.     

Microwave active filters based on coupled negative resistancemethod

A novel coupled negative resistance method for building a microwave active bandpass filter is introduced. Based on this method, four microstrip line end-coupled filters were built. Two are fixed-frequency one-pole and two-pole filters, and two are tunable one-pole and two-pole filters. In order to broaden the bandwidth of the end-coupled filter, a modified end-coupled structure is proposed. Using the modified structure, an active filter with a bandwidth up to 7.5% was built. All of the filters show significant passband performance improvement. Specifically, the passband bandwidth was broadened by a factor of 5 to 20     

三层单负材料为周期单元对称型一维光子晶体的频率特性

应用传输矩阵法研究了以三层单负材料为周期单元对称型一维光子晶体(ABC)M(CBA)M。结果表明,其带隙结构对入射角的敏感程度与光波的偏振性有关,TE波的高频通带会随着入射角的增大向中心频率移动,而TM波的带隙结构对入射角的变化不敏感。研究还发现各介质层厚度的变化对能带结构的影响规律不相同。当保持各介质层厚度比不变,成倍增大各介质层厚度,高、低频通带变窄并向中心频率移动,低频区通带首先消失。当改变各介质层厚度比时,若保持A、C层厚度不变,减小B层厚度,高、低频通带分别向两侧移动同时收缩变窄;若保持B层厚度不变,增大A、C层厚度,高、低频区通带同样变窄,低频区通带首先消失,带隙同样变宽。最后研究了该光子晶体的零有效相位带隙结构,发现其通带随晶格常数的增大逐渐向中心频率移动同时收缩变窄,这一特性可以用来设计单通道窄带零有效相位延迟滤波器。     

Electronically Tunable Microwave Bandpass Filters

Combline filters with novel input and output coupling networks which enable broad-band tuning to be achieved with minimum degradation in passband performance are discussed. Explicit design formulas for these filters are presented. Computer analysis of varactor tuned combine bandpass filters including the small signal varactor equivalent circuit is presented enabling filter performance to be easily evaluated. The design and experimental performance of a varactor tuned combline filter, realized in suspended substrate stripline is described. This filter toned from 3.2 GHz to 4.9 GHz exhibited low passband insertion loss and its performance was is close agreement with theoretical expectations.     

Integrated-Holographic Coarse-Wavelength-Division Multiplexers Patterned by DUV Photolithography

We demonstrate monolithically integrated four and eight-channel coarse-wavelength-division multiplexers with low insertion loss (IL) and wide flat-top passbands based on integrated-holographic filters. Like thin-film filters (TFFs), integrated-holographic filters function via a multipath interference and thus offer flexible passband control without the IL penalty that passband shaping typically incurs in single-mode angularly dispersive devices. Unlike TFF-based multiplexers, the multiplexers described here are based on the silica-on-silicon planar lightwave circuit platform rather than discrete optics and thus uniquely provide powerful TFF-like filtering function in fully integrated format. The multiplexer performance demonstrated is superior to the integrated solutions demonstrated to date, and competitive with discrete TFF-based devices     

A new approach to designing varicap-tuned filters

A new approach to designing electrically tuned bandpass filters that is based on the use of U-shaped resonators with several varicaps connected to each of the resonators is proposed. This approach makes it possible to improve the characteristics of the existing filters, reduce the filter passband loss and intermodulation distortions, and obtain narrow passband widths of 2% or less. It has been found experimentally that, using the new approach, the insertion loss that is similar to the loss of the filters based on p-i-n diodes has been obtained with tunable filters based on semiconductor varicaps for the first time.     

Dual and tri-band bandpass filters based on novel Π-shaped resonator

A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.