双环耦合结构及其在多路耦合器中的应用

腔体宽带超高频(UHF)多路耦合器因其结构原因导致滤波器端口至其合路点的等效电长度过长,造成通带性能下降。为解决这一问题,提出了一种应用于腔体可调带通滤波器的双环输入/输出耦合结构。对这种结构进行了理论分析以及仿真和实验验证。结果表明:利用这种结构能够在不显著降低可调滤波器通带特性的同时实现对其阻带反射特性的独立调节,可以有效减小可调滤波器端口的等效电长度。设计了采用双环耦合结构的同轴腔可调滤波器,并且利用四个双环滤波器制作了四路的UHF多路耦合器,实验结果显示了这种耦合结构的有效性。     

基于液晶的可调谐太赫兹双折射滤波器的设计

液晶双折射滤波器具有室温下工作,调谐简单方便,带宽窄等优点。为了达到设计不同调谐范围和带宽的这种滤波器的目的,以满足实际应用的需要,扩大其应用范围,采用数值模拟的方法,进行参数计算和设计思路的总结,并设计了一套窄带输出的滤波器实例。结果表明,通过对影响滤波器调谐范围和输出带宽的关键参数的数值模拟和分析,为设计不同调谐范围的液晶双折射滤波器提供了依据;设计实例基本上满足预期的设计要求,调谐范围0.691~0.866 THz。     

新型谐波抑制的四分之波长微带带通滤波器

提出了一种新型谐波抑制的四分之波长微带带通滤波器。该滤波器由一对平行耦合线与矩形开路端相连的谐振器以及两端对称的L形微带输入输出馈线构成。分析了不同的结构参数对滤波器性能的影响。实验仿真结果表明,该滤波器结构紧凑、尺寸小,具有良好的级联特性。一级、二级滤波器带外抑制能达到中心频率的瓴处,且二级滤波器带外衰减都大于35dB,适用于多种微波通信系统。     

新颖的高平坦度高功率掺铒光纤光源

报道了在前向结构中光纤前端输出处加用3dB耦合器制作的光纤圈反射器形成双程后向输出结构,实现了一种高平坦化的高功率光源。通过调节抽运功率及光纤长度等参量,实现3dB带宽达35．28nm(基本完全覆盖C波段),功率为7．679mW(8．85dBm)和平均波长为1545．881nm的超荧光光纤光源(SS)。与常用技术相比,该技术更简单,实用,同时提高了光源效率,稳定性好,易于降低成本,设计方便。由于L波段的超荧光的本身平坦度较好,此方案可得到高平坦度的C L波段高功率宽带超荧光输山,尤其适用于需要高平坦度高功率超荧光的场合。     

Increasing precision of measuring the radiofrequency dynamic range of a receiver

A circuit of a device for measuring the radiofrequency dynamic range of a receiving unit is suggested, which provides high precision due to the use of digital blocks for determining maximal and minimal signal values at the output peak detectors, connected to the outputs of the selective pass band filters of the linear circuit.     

Autoassociative neural networks and noise filtering

We introduce linear autoassociative neural (AN) network filters for the removal of additive noise from one-dimensional (1-D) time series. The AN network will have a (2M+1)/spl times/L/spl times/(2M+1) architecture, and for M fixed, we show how to choose the optimal L value and output coordinate from square error estimates between the AN filter outputs and the clean series. The frequency response of AN filters are also studied, and they are shown to act as matched band filters. A noise variance estimate is also derived from this analysis. We numerically illustrate their behavior on two examples and also compare their theoretical performance with that of optimal Wiener filters.     

Distributed fiber Raman amplifiers with localized loss

Backward pumped C- and L-band distributed fiber Raman amplifiers are described, where discrete losses from 0-8 dB were added at various positions to examine the effect of localized loss. Below 3-dB additional loss, the overall optical performance degraded similarly, regardless of loss position in a hybrid Raman and erbium-doped fiber amplifier. Above 3 dB, the performance degradation worsened as the loss position became closer to the signal output. The spectral shape change of the fiber output against loss variation was made tolerable within /spl plusmn/0.4 dB simply by balancing the output power of L band with that of C band, unless the loss was close to pump input. The tolerance provides design flexibility for hybrid optical amplifiers and allows the use of fixed gain-flattening filters.     

Stripline bandpass filters with step-impedance resonators

Research results for stripline bandpass filters with step-impedance resonators formed on Al₂O₃ (Alumina, polycor) and operating in the frequency band 1500–2500 MHz are presented in this article. Use of step-impedance resonators breaks repetition factor in frequency positioning of passbands in such filters. This allows suppressing harmonics of output signal in transmitters and widening stopband for parasitic signals in receivers.     

Electronically tunable ring resonator microstrip and suspended-substrate filters

Electronically tunable ring resonator microstrip and suspended substrate microwave filters with high tuning speed are presented. The filters are realised using two coupled ring resonators with GaAs varactors as the tuning elements. Computer optimised circuits are used at the input and the output to obtain better than 10 dB return loss across the tuning band. Tuning ranges of 1.075-2.25 GHz for the microstrip filter and 1.35-2.075 GHz for the narrower suspended substrate filter are predicted by computer simulation.<>     

Compact microstrip resonators for 900 MHz frequency band

A technique to reduce the size of planar resonators is investigated using a transmission line model and a finite-difference time-domain (FDTD) method. New miniaturized square microstrip resonators are proposed for 900 MHz band. The resonators offer low impedance sections leading to a better handling of power. The feasibility of compact filters using the proposed resonators is demonstrated. The input/output coupling lines of a two-pole filter have been positioned in a way that produces a filter response with transmission zeros on the both sides of the pass-band. Sharper skirts and higher out-of-band rejection are obtained for four-pole filters with cross-coupled resonators.     

An efficient channelizer tree for portable software defined radios

Power consumption is one of the most critical issues in the portable software-defined radio devices. A software radio receiver has the need to downconvert, bandwidth limit, and downsample a single narrowband channel from a span of frequencies in the Nyquist zone collected by the input analog to digital converter. In this paper, we present two techniques that perform the receiver function more efficiently than the standard Gray chip architecture formed by its direct digital synthesizer (DDS), and two stages of downsampling with a cascade integrator comb (CIC) filter and a pair of half-band filters. We compare the workload of this conventional architecture to two new architectures by applying them to the task of extracting a single, 30 kHz wide, channel from a 30 MHz band sampled at 90 MHz. One proposed structure replaces the CIC filter with a 10-stage cascade of 2-to-1 downsampling half-band filters with successively narrower transition bandwidths. In the second proposed structure, the DDS is moved to the output of the filtering stages which perform a sequence of 2-to-1 downsampling operations in half-band filters that perform incidental spectral translation by aliasing. We enlarge the set of half-band filter that reside at 0 and fs/2, to also include the Hilbert transform half-band filters residing at ±fs/4. At every stage in the cascade, the selected band resides in one of the four half-band filters. The 2-to-1 downsampling with that filter reduces the bandwidth and aliases the desired center through a sequence of known center frequencies. The desired channel is recovered from the output of the final stage by a complex heterodyne applied (at the low output rate) to obtain the desired spectral shift to base band. The paper provides a detailed workload analysis of the proposed structure along with simulation results that prove its effectiveness.     

Full-Wave Design of$H$-Plane Contiguous Manifold Output Multiplexers Using the Fictitious Reactive Load Concept

In this paper, a new procedure for the design of contiguous band manifold output multiplexers in$H$-plane configuration is presented. Such a configuration eliminates the slots between the T-junctions and the filters allowing high power handling, as well as dramatically reducing the risk of multipactor. This paper pursues the division of the design into tasks with low computational effort. The approach comprises: 1) the singly terminated synthesis of the channel filters and their corresponding full-wave responses; 2) the manifold design using fictitious reactive loads simulating the phase response of every channel out of its corresponding band; and 3) the final full-wave optimization of the whole structure using the simulated-annealing method. In order to validate the above procedure, a five-channel$Ku$-band multiplexer has been designed, manufactured, and measured.     

Method for improving ladder bulk acoustic wave filters rejection

This paper address design guidelines for improving the rejection of ladder bulk acoustic wave filters. An overview of the bulk acoustic wave filters technology enables to outcome the principal features of ladder filters. The lack of out-of-band rejection is currently an important weakness of this topology. The design technique presented enables to improve bulk acoustic wave ladder filters rejection by using their input/output bonding wires. Finally, the technique is used for design and fabrication of a bulk acoustic wave ladder filter for application in W-CDMA reception (2.11–2.17 GHz) front-ends. The filter measurement results show a significant improvement on the filter rejection at the transmission band (from ?19 to 34 dB) and on the return loss (from ?10 to ?16 dB) without considerable modification of filter insertion loss and selectivity.     

CMOS video filters using switched capacitor 14 MHz circuits

In order to realize self-contained analog video LSI, video band switched-capacitor (C) filters, including a two-dimensional filter, have been experimentally fabricated. By using 2-/spl mu/m/spl middot/CMOS technology and high-speed/high-precision circuits, an LSI clock rate of 14 MHz, signal swing of 2 V p-p with a single 5-V supply, random noise S/N of 60-70 dB p-p/r.m.s at LSI output, and power dissipation of less than 5 mW per amplifier have been achieved. Single-stage cascode amplifiers are extensively used to attain video band speed. Neutralization is introduced into fully differential filters to improve their frequency response.     

喇曼自由电子激光器中辐射的输出及测试

获得了喇曼自由电子激光器的激光辐射输出。给出了漂移管、出射及接收喇叭、滤波器等主要元件的设计方法及激光器实验中辐射测试的结果。     

基于PIN开关的可重构双波段功率放大器设计

为满足5G通信中多标准、多模式系统对功率放大器的需求,提出了一种新型的可重构双波段匹配电路结构.首先,在输出匹配网络中加入分布式PIN开关,通过开关的闭合与断开实现两个双波段输出匹配电路的良好匹配;然后,基于带通滤波器理论设计的宽带输入匹配网络,能够实现1.5～2.5 GHz频段内的良好匹配.为验证方法的有效性,采用C...     

宽带压控带阻滤波器分析

在继电保护通讯中,通讯信号在传输过程中通常会受到外部某一宽频段信号的干扰。特别是在载波通讯方面,其严重影响了通讯质量以及继电保护装置动作。但传统的窄带阻滤波器的衰减范围过小,无法达到衰减此宽频段干扰信号的理想效果。而一种宽带压控型带阻滤波器能够满足这一要求,同时具有电路性能稳定、增益便于调节的优点。因此,分析这种压控型宽带阻滤波器,研究其输入与输出电压波形、幅频特性和相频特性,并扩展实例应用,证明其具有一定的现实意义。     

A High-Power S-Band Filter (Correspondence)

This note describes the measured performance of a high-power S-band "waffleiron" filter. Techniques for designing varying-impedance corrugated waveguide filters in rectangular waveguide have been available for some time [1 ]. If propagation is restricted to the dominant TE/sub 10/ mode, these filters have wide well-matched pass bands and wide high-attenuation stop bands. Unfortunately, the filters may have spurious transmissions in the stop band when power is incident upon them in other modes, such as TE/sub 20/ or TE/sub 30/, if the guide wavelength of these modes at the stop band frequencies is equal to the guide wavelength of the TE/sub 10/ mode at the pass-band frequencies of the filter.     

Miniaturised microstrip bandpass filters based on Moore fractal geometry

This paper presents new microstrip bandpass filter design topologies that consist of dual edge-coupled resonators constructed in the form of Moore fractal geometries of second and third iteration levels. The space-filling property for proposed fractal filters has found to produce reduced size shapes in accordance with sequential iteration levels. These filters have been prepared for ISM band applications at a centre frequency of 2.4 GHz using a substrate with a dielectric coefficient of 10.8, dielectric thickness of 1.27 mm and metallisation thickness of 35 µm. The output responses of each fractal bandpass filter have been determined by a full-wave-based electromagnetic simulator Sonnet software package. Simulated and experimental results are approximately compatible with each other. These responses clarify that these fractal filters have good transmission and return loss characteristics with blocked higher harmonics in out-of-band regions.     

Standardizable low-pass voice band hybrid circuit filters for pulse code modulation (PCM) communication systems

A standardizable design approach to realize the voice band low-pass filters for a variety of pulse code modulation (PCM) communications systems is described. This design concept incorporates cascaded RC active filter sections, thick and thin film hybrid technologies, and functional tuning to allow the use of the same hybrid design for both transmit and receive filters, for a range of input and output requirements. Tuning, sensitivity analyses, and implementation tradeoffs are described. Thick film implementations, using NPO chip capacitors, with the new high stability resistor inks as well as thin film implementation, using the usual tantalum integrated thin film technology are presented. Very stringent requirements have been successfully met using state-of-the-art hybrid technologies.