A 128-kHz mechanical channel filter with finite-frequency attenuation poles

The paper describes the design and manufacture of a miniaturized 128-kHz pole-type mechanical channel filter for FDM communication systems. By introducing a new phase inversion structure to realize the finite attenuation poles, and by minimizing sensitivity in the circuit design, we have designed and manufactured a miniaturized high-performance mechanical channel filter. The filter volume is 10.7 cm³, which is about ⅙ that of conventional LC channel filters. The passband response satisfies the 1/20 CCITT Recommendation. With this filter, we have developed a channel modem compact enough to mount 900 channel units per standard bay. Manufacturing steps and material characteristics are described in some detail. We also briefly discuss some future considerations in further miniaturizing the channel filter.     

BNKLT无铅压电陶瓷梯形中频带通滤波器的研制

利用发明的[Bi0.5(Na1-x-yKxLiy)0.5]TiO3(BNKLT)系无铅压电陶瓷,采用全电极径向振动模式制作了插入损耗小于6 dB,阻带损耗大于30 dB,频率特性曲线平滑,并具有良好选择性的中频(IF=460 kHz)多节带通滤波器。与含铅压电陶瓷多节滤波器相比,BNKLT无铅压电陶瓷滤波器的特性有待进一步改进。     

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 waveguide filters with multiple attenuation poles using dual-behavior resonance of frequency-selective surfaces

This paper develops novel waveguide filters consisting of frequency-selective surfaces (FSSs) in order to realize both the drastic size reduction and multiple attenuation poles in stopbands at both sides of passband. The FSS provides not only a passband but also attenuation-pole frequencies in stopbands since the FSS has both the aperture-element and the patch-element behaviors. In the present design method, the shape of each FSS is designed by a genetic algorithm so that the resonant curve of FSS can be fitted to that obtained from an equivalent-circuit approach. By using such FSSs and quarter-wavelength waveguides, a bandpass filter with six attenuation poles like an elliptic-function filter has been constructed. Furthermore, a technique of the size reduction by controlling adequately the resonant response of each FSS is presented. In this filter, the FSSs are closely located at the interval of the length much shorter than a quarter wavelength. It is shown from the design example that the half longitudinal length of the former example can be obtained, keeping both the passband response and attenuation poles in stopbands. The effectiveness of the waveguide filters with FSSs is validated by good agreement between the calculated and the measured results.     

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     

PCM编解码器中高性能开关电容滤波器设计

基于PCM(Pulse-Code-Modulation, 脉冲编码调制)语音编解码器设计了其中的发送端开关电容滤波器,包括高通滤波器和低通滤波器.对高通滤波器和低通滤波器的设计分别采用两种不同的方法--级联法和梯形法,然后把这两部分级联起来就实现了带通滤波器.仿真结果表明开关电容带通滤波器通带波纹0.24 dB,阻带衰减37 dB,对60 Hz以下频率的衰减大于32 dB,动态范围达到90 dB,满足D4信道处理单元发送滤波器的技术要求[1].设计的开关电容滤波器在一款PCM语音编解码芯片中成功实现.     

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.     

新型的平面双模椭圆函数带通滤波器

根据传统的方形贴片双模滤波器,提出了一种新颖的带有两个切角的平面双模带通滤波器结构.该结构使用单个贴片谐振器并且没有耦合缝隙,通带两端各有一个衰减极点,有效减小了滤波器的辐射损耗.对该滤波器结构进行改进,又提出了一种带有两个相互正交、长度不等槽线的双模椭圆函数带通滤波器结构.该滤波器在中心频率1.8GHz处,回波损耗达到31.53 dB,通带内最小插损达到0.01 dB,3 dB相对带宽为19.44%.采用Ansotf公司的En-sem ble 8.0仿真软件进行的仿真研究.仿真结果表明该结构可以更加有效地减小辐射损耗,增加带宽,且体积比传统滤波器减小了约40%,有利于小型化.     

Computer-Aided Group Delay Equalization for Broad-Band Satellite Transponder Applications

Equalization of the group delay characteristic of a satellite repeater has been examined. The channel group delay includes the transmit and receive filter group delay, and the transponder filter group delay. The perturbation of the transponder group delay of a satellite channel caused by the dual-path transmission effect resulting from an adjacent channel has also been studied. Various combinations of filter and equalizing sections have been examined. In the realization of wide passband filters, equalization of group delay presents some difficulties, especially when it is achieved by networks with many sections. The minimum peak-to-peak group delay deviation in the specified passband has been achieved by using a recent nonlinear programming technique with a penalty function approach.     

Designing IIR filters with a given 3-dB point

Often in infinite impulse response (IIR) filter design, our critical design parameter is the cutoff frequency at which the filter's power decays to half (-3 dB) the nominal passband value. This article presents techniques that aid in the design of discrete-time Chebyshev and elliptic filters given a 3-dB attenuation frequency point. These techniques place Chebyshev and elliptic filters on the same footing as Butterworth filters, which traditionally have been designed for a given 3-dB point. The result is that it is easy to replace a Butterworth design with either a Chebyshev or an elliptic filter of the same order and obtain a steeper rolloff at the expense of some ripple in the passband and/or stopband of the filter.     

B-spline design of maximally flat and prolate spheroidal-type FIRfilters

A digital FIR filter is described that offers excellent passband and stopband characteristics for general applications. Design formulae include parameters that adjust the magnitude response from one having characteristics like the maximally flat designs of Hermann (1971) and Kaiser (1975, 1979) to one having characteristics like the minimum-sidelobe energy approximations of Kaiser and Saramaki (1989). The impulse response coefficients are more straightforward to obtain than these filter designs while offering preferable response characteristics in many instances. Unlike FIR filters designed by window- or frequency-sampling methods, the filter coefficients are determined from the inverse Fourier transform in closed form once B-splines have been used to replace sharp transition edges of the magnitude response. Although the filters are developed in the frequency domain, a convergence window is identified in the convolution series and compared with windows of popular FIR filters. By means of example, adjustment of the transitional parameter is shown to produce a filter response that rivals the stopband attenuation and transition width of prolate spheroidal designs. The design technique is extended to create additional transitional filters from prototype window functions, such as the transitional Hann window filter. The filters are particularly suitable for precision filtering and reconstruction of sampled physiologic and acoustic signals common to the health sciences but will also be useful in other applications requiring low passband and stopband errors     

New type of time-varying octave filter

Double quadrature-modulation realisations of lowpass and highpass filters were described recently by Saraga. Extensions to these methods lead to the design of an octave filter using one carrier oscillator rather than the two needed for an equivalent filter designed by the technique referred to above. If the output frequencies are not required to be identical to the input frequencies, this filter also uses fewer modulators. By employing two carrier oscillators, any desired bandwidth may be obtained; the bandwidth and passband position may then be independently varied.     

基于SIW技术的毫米波滤波器研究与设计

基于基片集成波导（substrate integrated waveguide,SIW）结构设计了两款四阶的耦合带通滤波器,使用三维全波电磁场仿真软件HFSS对设计的两款滤波器进行了仿真设计和优化.由仿真结果分析得出,两款滤波器的工作频率均位于毫米波频段.第一款SIW滤波器实现了切比雪夫型响应,中心频率为20 GHz,带宽为2 GHz,通带内的插入损耗低于1.5 dB,回波损耗低于-20 dB,在阻带中对信号的衰减程度可以达到50 dB.第二款SIW滤波器实现了准椭圆函数型的响应,中心频率为29.1 GHz,带宽为300 MHz,通带内的插入损耗低于1 dB,回波损耗低于-20 dB,在通带到阻带的过渡中实现了两个陷波点.仿真结果表明,在毫米波滤波器设计中引入SIW结构,有利于优化滤波器尺寸,得到较好的滤波器性能指标,是毫米波滤波器发展的一个重要方向.     

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.     

E-Plane Integrated Circuit Filters with Improved Stopband Attenuation (Short Papers)

Improved stopband attenuation is achieved by thick strips, by reduced waveguide sidewall dimensions, and by double planar integrated circuits. In contrast to thick strips which may cause high passband insertion losses and filters with reduced waveguide dimensions which require additional tapers, double planar E-plane integrated circuit filters combine the advantages of low costs, high stopband, and low passband insertion losses. Computer-aided design of a four-resonator Ka -band double metal insert filter achieves a calculated stopband attenuation between 40 and 60 GHz of more than 50 dB, the calculated minimum passband insertion loss is 0.43 dB (measured 1.8 dB). Higher order mode excitation and finite thicknesses of the inserts are included in the calculations.     

Compact planar and vialess composite low-pass filters using folded stepped-impedance resonator on liquid-Crystal-polymer substrate

A compact composite low-pass filter, designed by the image parameter method and semilumped component approach, will be described and results for cutoff frequency ranging from C- to V-band will be presented. This composite design combines four filter sections and the presence of a strong attenuation pole near the cutoff frequency provides an extremely sharp attenuation response, while ensuring good matching properties in the passband, making this filter design very attractive for harmonic spurious response suppression or diplexing. The lumped-element schematic of the filter has been implemented using a combination of a stepped-impedance filter and folded stepped-impedance resonators. The overall folded layout has been optimized using full-wave simulation and occupies an ultra-compact area of only 5/spl times/5 mm/sup 2/ for a C-band filter. Measured results exhibit rejection of the attenuated pole greater than 40 dB. Similar filter designs have been realized for C- and V-bands. These filters have been fabricated on a liquid-crystal-polymer substrate demonstrating a high performance, ultra-compact, and very low-cost solution for RF and millimeter-wave applications.     

Analysis of the coupling coefficients of stripline resonators in the designs of suspended-substrate filters

Expressions for the frequency-dependent coupling coefficients of stripline resonators in miniature designs of suspended-substrate filters are obtained. The effect of the design parameters of such filters on the coupling coefficients of their resonators is theoretically studied and frequency-selective properties of the device are analyzed. It is shown that interaction between resonators at frequencies of the filter passband is predominantly inductive in the presence of small capacitive interaction and the attenuation poles of the amplitude-frequency response (AFR) observed beyond the passband are caused by the mutual cancellation of inductive and capacitive interactions. Frequency dependences of coupling coefficients can be used to explain features of the AFRs of suspended-substrate filters. It is shown that experimental AFRs agree well with theoretical AFRs calculated in quasi-static approximation with the use of 1D models.     

Some Special Design Considerations for a Mechanical Filter Channel Bank

The technical concept realized by the channel bank is optimum with respect to a variety of requirements. Considerations of size and fabrication technology recommend a frequency of 50 kHz for the mechanical filter. The general concept of the modulator suggests a filter design with tuned conventional transformers. Since subsequent adjustment of the assembled mechanical part of the filter is undesirable, the provision of finite attenuation poles has been abandoned at the expense of adding two extra resonantors. The design imposes only modest demands as to the reproducibility of the mechanical couplings. By tuning the transformers it is possible to correct minor production tolerances. A special design of the channel and associated signal filter results in a very low temperature dependence and permits to connect both filters directly in parallel.     

All-planar dual-mode asymmetric filters at Ka-band

All-planar dual-mode inductive asymmetric filters utilizing new planar microstrip to dielectric-loaded rectangular waveguide transitions at Ka-band were presented and built in this work. The conventional, three-dimensional metallic rectangular waveguide dual-mode filters can be implemented into mature PCB technology with a much easier and lower-cost fabrication process on the basis of the all-planar feature of the transition. This work demonstrates two Ka-band filter examples with center frequency at 31 GHz and bandwidth at 1 GHz and 2 GHz. The measured minimum insertion loss of each case was, respectively, 2.68 and 1.12 dB, with greater than 10 dB return loss in the passband. Moreover, the measured side-band attenuation (near passband) is larger than 30 dB due to the transmission zeros at each side of the passband.     

Waveguide Sandwich Filters

A new class of waveguide filters is introduced, constructed from several thin plates sandwiched together. The combination of alternate plates having large and small rectangular apertures leads to a propagating structure which possesses a bandstop response and prescribed characteristic impedance. This basic element may be used as a simple compact bandstop filter, particularly where the main passband and stopband are well separated, such as in harmonic rejection. For filters with many stopbands, combinations of several waveguide sandwich filter elements are used to provide the main passband and the required attenuation characteristics in the prescribed stopbands. Although the filter is ideally suited for bandstop filtering due to its small size, low cost, low loss, and high power handling capability, additional applications to bandpass filtering and dispersive delay line operation are also cited.