Compact and wideband microstrip bandstop filter

A novel one-section bandstop filter (BSF), which possesses the characteristics of compact size, wide bandwidth, and low insertion loss is proposed and fabricated. This bandstop filter was constructed by using single quarter-wavelength resonator with one section of anti-coupled lines with short circuits at one end. The attenuation-pole characteristics of this type of bandstop filters are investigated through TEM transmission-line model. Design procedures are clearly presented. The 3-dB bandwidth of the first stopband and insertion loss of the first passband of this BSF is from 2.3 GHz to 9.5 GHz and below 0.3 dB, respectively. There is good agreement between the simulated and experimental results.     

CPW bandstop filter using periodically loaded slot resonators

A new dual-spiral-shaped slot resonator in a coplanar waveguide (CPW-DSR) is studied. Also, its equivalent circuit model is introduced and used for multi-resonant performance analysis. Finally, a bandstop filter using periodically loaded CPW-DSRs is presented and verified by simulations and measurement.     

Compact ultra-wideband antenna with dual bandstop characteristic

A simple and compact ultra-wideband microstrip-fed planar antenna with dual bandstop characteristic is presented. By using a U-slot defected ground structure (DGS) in the feedline, a stopband of 600 MHz (from 5.45 to 6.05 GHz) for band rejection of WLAN is achieved. To obtain another stopband, an arched slot is etched on the radiating patch. Experimental results show that the designed antenna, with a compact size of 30 times 24.5 mm, has an impedance bandwidth of 2.8-11 GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.5-4.25 GHz and 5.45- 6.05 GHz. Moreover, the antenna has good omnidirectional radiation patterns in the H-plane.     

Compact dual-band bandstop filter using folded resonator

A compact dual-band bandstop filter composed of main transmission line and four folded resonators is presented. Through analyzing the structure of folded resonator, it is found that the main transmission line connected with two proposed folded resonators exhibits the characteristic of band-rejection. Simulated results show that the center frequency of stopband is 2.72 GHz. Then, through adding another pair of folded resonator; a compact dual-band bandstop filter is achieved. Simulated results demonstrate that transmission poles are induced to have better selectivity. Additionally, in order to explain the mechanism of proposed structure, the LC equivalent circuit, analysis of parametric effect and surface current distributions are given. Due to the folded structure, the filter dimensions are reduced and the adjustable stopband is another feature. By virtue of optimization, proposed structure is fabricated. Measured results agree well with the simulation.     

Compact frequency and bandwidth tunable stopband filters using split ring resonators and varactors coupled transmission line

Two highly compact tunable stopband filters using microstrip transmission lines coupled with split ring resonators (SRRs) and varactor diodes are presented. Frequency or bandwidth tuning capability of each device is demonstrated. The frequency tunable filter, realized by a single stage, shows a wide tuning range of 19.8% with a maximum bandwidth of 5% and an insertion loss of approximately 20 dB at 4 GHz. The bandwidth tunable filter, realized by double stages, shows a 10-dB bandwidth of 19–34% with a biasing voltage of 0–10 V. The implemented frequency tuning and bandwidth tuning devices show a significant area reduction of 60.1% and 53.5%, respectively, in comparison with a similar frequency or bandwidth tunable structure presented by others. Equivalent circuit models are presented. The measured S-parameters are in good agreement with simulated ones.     

Digital bandpass and bandstop filters with variable center frequency and bandwidth

This paper presents a method of designing wave digital bandpass (BP) and bandstop (BS) filters whereby the center frequency and bandwidth can be independently controlled by simply changing the multiplier values. Also given are the canonic realizations for the BP and BS wave digital filters. This method of designing BP and BS wave digital filter results in a saving of coefficient registers.     

Compact dual-band open-stub bandstop filter with suppression of spurious passbands

In this article, by replacing the series quarter-wavelength connecting line of conventional open-stub bandstop filter (BSF) with the equivalent P-shaped line, a compact dual-band BSF is proposed and designed. Furthermore, it suppresses a lot of spurious passbands of the open-stub BSF. Design equations of P-shaped line are achieved by ABCD matrixes. To validate the design concept, two full-wave electromagnetic simulators are used and the proposed filter is fabricated. The simulate results are in excellent agreement with measurement results. The circuit area of the dual-band BSF is only 50% of the conventional open-stub BSF.     

Microstrip dual-band bandstop filter of defected ground structure and stepped impedance resonators

This article presents a compact microstrip dual-band bandstop filter (BSF), in which one λ_g/4 defected ground structure (DGS) pair is utilised to realise one stopband while two stepped impedance resonators (SIRs) help obtain another stopband and suppress the spurious harmonics. The design strategies and the equivalent circuits are introduced in detail. The measured results indicate 43.8% and 18.7% fractional bandwidth in the two stopbands (2.4 GHZ and 5.2 GHz) respectively, and the return loss is greater than 15 dB in the whole passband. In addition, size reduction can be conveniently achieved by adjusting the length of the SIRs and DGS.     

Compact free-electron laser resonators utilizingelectron-transparent mirrors

The potential advantages and the physical properties of several electron-transparent mirrors (e.g., metal meshes, thin foils, pierced mirrors, and Bragg reflectors) to be used in infrared free-electron laser resonators are reviewed. The conditions under which the effect on the electron beam quality can be kept small are discussed, and experimental results on the angular spread produced by a 2.5-μm-thick metal mesh on a 5 MeV electron beam are presented. The experimental test of a resonator with two different electron transparent output couplers is reported     

一种新型的可调谐窄带脉冲染料激光器

本文报导了一种腔内带有毛细管的Littman式激光谐振腔,与一般Littman式激光谐振腔相比,发现该系统的输出激光在能量、模式和频带宽度等参数上得到明显改善。文中对该系统最新的设计机理也进行了分析讨论。     

Compact dual-frequency PIFA designs using LC resonators

We report our investigation into single-feed dual-frequency planar inverted F antenna (PIFA) designs which make use of LC resonators (or “RF traps”). We introduce three basic methods for incorporating the LC resonator into the PIFA, including a variant of the meandering PIFA. Experimental results are provided and these show that dual-frequency operation at 900 (cellular systems) and 1800 MHz (personal communication systems) can be achieved for all three designs     

Compact interlocked-coupled filter using folded stepped-impedance resonators

A microstrip interlocked-coupled bandpass filter is proposed with a markedly compact structure. The low-impedance open-end line of the quarter-wavelength Stepped-Impedance Resonator (SIR) is replaced by two open-end high-impedance lines, which not only facilitate the coupling mechanism but also provide the strong electric coupling between resonators. With the proper utilization of folded SIRs, the occupied area of coupled-resonator pair can be reduced. By applying the proposed coupled-resonator pair, the passband filter with the compact size can be realized. Good agreement between measured and simulated results is observed. The proposed filter is desirable for compact and high-performance microwave circuit applications.     

Compact bandpass filters using stepped impedance resonators

This paper presents a theoretical analysis of, and experimental results given by, stepped impedance (SI) resonators constructed and used as high-Q resonators in the UHF band. These results made it clear that the Q-factor is higher than conventional capacitor-loaded resonators. Three types of bandpass filters were designed and fabricated using the SI resonators. The filters mentioned in this paper show that excellent performance has been obtained.     

Compact radiating element

A new, compact, low profile radiating element is described which has a number of interesting and useful characteristics that are not easily obtained from microstrip patches or other low profile radiators. The element, which is shaped like a small square metal cap, has a very compact footprint and a height of the order of one-eighth of a wavelength. Both circularly polarised and linearly polarised variants have been investigated, and a bandwidth in excess of 17% has been demonstrated     

Compact wound-type slot antenna with wide bandwidth

A new type of a slot antenna in which a slot is formed in wound-type around a dielectric substrate is proposed. In comparison with a conventional meander slot antenna, the proposed antenna has a wider bandwidth and smaller size. The proposed antenna has been designed on a gallium arsenide (GaAs) substrate and fabricated by integrated circuit process for the integration of the antenna with active components. The fabricated antenna has dimensions of 6.2 /spl times/4.1 mm/sup 2/ and a 10-dB bandwidth of 300 MHz at 5.8 GHz.     

DCG窄带反射滤光片再现波长和带宽的控制方法

本文从DCG的成像特性出发 ,讨论了用DCG制作全息窄带反射滤光片时 ,干板制备、曝光记录、显影处理以及暗反应和后光化反应对全息滤光片的再现波长和反射带宽的影响 ,并给出了控制再现波长和带宽的方法。     

Equivalent lumped elements G, L, C, and unloaded Q's of closed- andopen-loop ring resonators

A transmission-line model is used to extract the equivalent lumped-element circuits for the closed- and open-loop ring resonators. The unloaded Q values of the ring resonators can be calculated from the equivalent lumped elements G, L, and C. Four different configurations of microstrip ring resonators fabricated on low and high dielectric-constant substrates are used to investigate the lumped elements and unloaded Qs. The largest difference between the measured and calculated unloaded Q is 5.7%, which is due to measurement uncertainties and accuracies of the calculation. These simple expressions introduce an easy method for analyzing ring resonators in filters and provide, for the first time, a means of predicting their unloaded Q     

Stacking resonators to increase the bandwidth of low-profile antennas

A method of increasing the bandwidth of low-profile cavity-hacked slot and microstrip patch antennas without appreciably adding to the antenna dimensions is presented. This idea incorporates the stacking of structures which have close resonant frequencies. Energy is coupled between cavities via carefully placed slots in the common wall. An approximate two-and-a-half fold increase in input impedance bandwidth has been observed for a certain cavity-backed slot antenna.     

High-efficiency generation of narrow bandwidth tunable VUV radiation

Frequency tunable VUV radiation has been generated using excimer lasers and very narrow bandwidth dye lasers by two-photon resonant difference frequency mixing in xenon. Conversion efficiencies of >0.1 percent have been achieved.     

可调谐窄带宽的负系数微波光子滤波器

针对负系数微波光子滤波器很难用正系数的光学抽头来实现,提出了一款基于色散器件级联的可调谐、窄带宽、负系数微波光子滤波器。利用整形后的多波长光纤激光器的输出信号作为滤波器的抽头光源,将单模光纤与F-P光纤环级联作为延迟单元,实现滤波器的频率选择性。利用相位调制器和级联的色散器件共同作用,实现负系数的微波光子滤波器。实验得到了波长间隔为0.34 nm的多达37个激光信号的稳定输出,进而基于此实验结果仿真研究了F-P光纤环中C2、C3的耦合系数r、不同长度的可调谐光纤延迟线（TODL）和延迟单元中不同长度的单模光纤等参数对微波光子滤波器性能的影响。