Photonic bandpass filters with high skirt selectivity and stopband attenuation

A new photonic signal processor topology that simultaneously achieves both a high-Q and a high skirt selectivity and stopband attenuation filter response is presented. It is based on a novel dual-cavity bandpass optical structure in which two pairs of active fiber Bragg grating cavities are used with an optical gain offset to control the poles and stopband attenuation characteristics of the filter. This concept enables a large improvement in the filter stopband attenuation, rejection bandwidth, and skirt selectivity to be realized. Measured results demonstrate both a narrow bandpass bandwidth of 0.4% of center frequency and a skirt selectivity factor of 16.6 for 40 dB rejection, which corresponds to a 6.5-fold improvement in comparison to conventional single cavity high-Q structures. To our knowledge, this is the best skirt selectivity reported for a photonic bandpass filter to date. The new photonic filter structure has been experimentally verified and excellent agreement between measured and predicted responses is shown.     

Double Coupler Amplified Recirculating Delay Line Microwave Photonic Bandpass Filter

Theoretical and experimental investigations on a double coupler amplified recirculating delay line (ARDL) microwave photonic bandpass filter are presented. These show that the system involves both coherent and incoherent summation of optical signals. This enables a higher order filter transfer function to be realized, which results in a high-performance frequency response that cannot be achieved by the conventional single coupler ARDL structure. Experimental results are presented that demonstrate a sharp, high skirt selectivity and high stopband rejection level bandpass filter response.     

Tunable photonic bandpass filter with high-frequency response performance

A continuously tunable RF/microwave photonic bandpass filter that simultaneously achieves high skirt selectivity and high stopband attenuation is presented. It is based on controlling the signal polarisation state in a reflective amplified recirculating delay line loop with a polariser at the output. A technique to overcome the phase noise limitation in the structure is also presented. Experimental results demonstrate continuous tuning of the high-performance photonic bandpass filter and a continuously tunable photonic bandpass filter with a low-noise performance.     

An Ultra-Broadband Coplanar-Waveguide Bandpass Filter With Sharp Skirt Selectivity

An ultra-broadband coplanar-waveguide (CPW) bandpass filter (BPF) is demonstrated. The proposed CPW BPF is designed via cascading CPW lowpass and bandpass structures. As compared to the classical CPW BPFs, the ultra broadband is realized relatively easily by separately adjusting the cutoff frequencies of the CPW lowpass and bandpass structures. The cascaded CPW BPF is of greater than 120% 3-dB fractional bandwidth, very sharp skirt selectivity, good stopband rejection, and no repeated passbands     

Novel reduced-size coplanar-waveguide bandpass filter using the new folded open stub structure

Proposes a novel folded skill and a simpler method than that of older methods. The advantages of this new structure reveals a better skirt factor than that of the conventional folded /spl lambda//4 series open stub, and it reduces the folded area of the conventional structure by at least 50%. Besides, by using the new folded /spl lambda//4 open stub to realize a bandpass filter, the size of the circuit will be reduced greatly and achieve better stopband rejection.     

Dual-band microstrip bandstop filter using dual-mode loop resonator

A dual-band bandstop filter (DBBSF) with a dual-mode loop resonator is presented. In order to allow the DBBSF to exhibit high skirt selectivity and to generate a wide rejection bandwidth a capacitive coupled-line section is introduced. By properly controlling the length of the coupled-line section and the cross-coupled capacitor, more than two finite transmission zeros were inserted at the stopband and enhanced the rejection bandwidth.     

Classes of Sub-Miniature Microwave Printed Circuit Filters with Arbitrary Passband and Stopband Widths

Four new classes of microwave bandpass filters are defined herein. They are realized in triplate stripline and are exceedingly small devices as a result of using transmission line elements which are a quarter-wavelength well above the frequency of the passband. Each filter corresponds to a bandpass S-plane prototype which is derived using exact synthesis procedures from a specification of transmission zero locations. Passband and stopband widths may be independently specified and an extremely high degree of selectivity can be achieved when necessary. The slope of a filter skirt can he chosen to be such that 60 dB of attenuation is reached at a frequency < 3 percent from the comer of the passband.     

宽阻带阶跃阻抗发夹线带通滤波器设计

提出了新的抑制微带带通滤波器寄生通带的方法。这种方法通过级联阶跃阻抗发夹线谐振器构成的椭圆函数低通滤波器于带通滤波器的输入/输出端,显著改善了后者的阻带抑制特性。本文基于新的等效电路模型,推导出了此类低通滤波器的阻带传输零点位置。设计了L波段宽阻带阶跃阻抗发夹线带通滤波器验证了理论分析和设计过程的正确性。     

Compact two-order bandpass filter with three finite zero points

A novel two-order bandpass filter (BPF) is proposed. The parallel coupling paths as well as similar zero point generation mechanism for the fundamental frequency and the first spurious frequency give the filter three controllable finite zero points in the stopband without adding any extra elements. Good skirt selectivity and controllable stopband characteristics can be achieved simultaneously.     

高选择性发夹型带通滤波器的设计

微带发夹型带通滤波器具有尺寸小、结构简单、性能稳定等优点,在射频微波领域有着广泛的应用。 本文使用ADS 软件设计仿真了一种高选择性抽头式发夹型带通滤波器。与一般发夹型滤波器相比,该滤波器在输 入输出端并联四分之一波长开路微带线,通过在寄生通带增加传输零点的方法提高滤波器的带外抑制性能。另外, 在该滤波器的谐振单元上增加并联阶跃阻抗枝节,在通带两侧产生一对传输零点,来提高该发夹型带通滤波器的选 择性。最后对这种高选择性发夹型带通滤波器进行实物加工,测试结果证实了该带通滤波器的良好选择性能。     

高阻带抑制LTCC 滤波器的设计与实现*

提出了一种基于LTCC技术的新型高阻带抑制带通滤波器的实现方法.采用在并联谐振器的圆柱形电感之间引入感性耦合,在高阻带产生一个传输零点,并且能实现非常好的阻带衰减性能.本文对传统的梳状线带通滤波器结构进行改进,利用过孔的寄生电感效应,将过孔用作谐振杆,明显减小了器件的尺寸.并且通过利用空间耦合的寄生效应,实现滤波器的阻带高抑制传输零点,以满足了对特殊频点高抑制的要求.运用该方法设计了中心频率1.65 GHz,通带200MHz,带外2GHz处衰减大于60dBc的五级带通滤波器.实物测试结果和全波电磁仿真结果吻合较好.     

Design of Compact Tri-Band Bandpass Filters Using Assembled Resonators

A novel approach for designing tri-band bandpass filters with independently controllable center frequencies and improved stopband rejection characteristic is presented in this paper. The assembled resonator constructed by a stepped impedance resonator and a common half-wavelength resonator is employed to obtain tri-band response. The stepped impedance resonator is designed to operate at the first and third passbands and the other resonator is designed to operate at the second passband. Two kinds of filter configurations with cascaded and pseudointerdigital formats are proposed. Based on lossless lumped-element equivalent circuit, it is found that both filter structures can introduce transmission zeros between passbands. To verify the proposed approach, two filters are designed and fabricated, the measured results exhibit tri-band bandpass responses with high selectivity.     

Parallel-Coupled Coplanar-Waveguide Bandpass Filter With Multiple Transmission Zeros

A compact parallel-coupled coplanar-waveguide bandpass filter with good selectivity and stopband response is proposed. By using the quarter-wavelength resonators in implementation, the filter size can be reduced and no spurious passband is observed at twice the center frequency (2f₀). In addition, by suitably introducing the capacitive and inductive cross-coupling effects, four transmission zeros around the passband edges may be created for improving the filter selectivity. For design purpose, the equivalent-circuit models are also established. In this study, the compact fourth-order filter with multiple transmission zeros for improving the selectivity is implemented, and its stopband is extended up to 3.43f₀ with a rejection better than -30dB     

Wide-stopband microstrip low-pass filter using modified semi-circle patch resonator

In this article, a compact microstrip low-pass filter with elliptic-function response is proposed. To achieve wide stopband, modified semi-circle patch resonator in series with semi-circle stepped impedance resonator is used. The proposed structure achieves a wide stopband and a high selectivity within a small circuit area. The proposed filter has 3-dB cutoff frequency at 1.71?GHz and 20?dB rejection at 2.1?GHz. The stopband with the attenuation level better than ?18.7?dB is from 2.08 up to 16?GHz, and consequently we have reached the high and wide rejection in stopband as well as compact size. The structure is simulated, fabricated and measured. The measured results are in good agreement with the simulated results.     

一种低插入损耗的180 GHz腔体滤波器

基于H形感性窗结构设计了一款低插入损耗的8阶波导腔太赫兹滤波器.经Ansoft HFSS对滤波器进行仿真优化后,滤波器采用传统的数控铣进行实物加工.测试结果表明:滤波器的中心频率位于179.1 GHz,1 dB相对带宽为8.7％.滤波器中心频率处的插入损耗为0.34 dB,回波损耗优于18.9 dB.所设计的太赫兹腔体...     

Ultra-wideband bandpass filter using CPW-to-microstrip coupling structure

A novel ultra-wideband bandpass filter based on a back-to-back microstrip-CPW transition structure is presented. The filter is composed of two microstrip-CPW transitions and a section of microstrip line used as a multiple-mode resonator. The filter has been investigated numerically and experimentally. Both simulated and measured results show that the filter has a good performance, including a small insertion loss, a group delay variation of less than 0.2 ns, stopband of up to 16.0 GHz at high frequencies, and an out-of-band rejection level of below -20.0 dB.     

A Wideband and High Rejection Multimode Bandpass Filter Using Stub Perturbation

A novel multimode bandpass filter with high and wide rejection band is proposed by using an open stub. The open-stub has two functions in the filter: (1) perturbation for the multimode operation and (2) zero point generation at the stopband for the stopband control. With proper input/output coupling, additional two poles, i.e., four poles, can be generated for the proposed filter structure. The design is then verified by experiment. The single structure four-mode filter has low insertion loss, good stopband performance, and compact size and linear phase.     

小型化多层带线谐振腔缺陷地结构LTCC宽带带通滤波器

利用多层宽边耦合带状线谐振结构实现小型化LTCC(LowTemperature Co-fired Ceramic)宽带滤波器。采用了两层、三层耦合带线谐振结构,利用这两种谐振结构可以有效减小滤波器的尺寸。利用四个谐振腔结构,实现较宽的频带和较强的选择特性;输出、输入引入电感反馈产生两个传输零点,利用DGS(Defected Ground Struc-ture)可使滤波器在阻带和镜像频率处产生较大的衰减。设计出侧面印刷互连和侧面通孔互连两种工艺结构的滤波器,利用LTCC工艺加工出侧面印刷互连的滤波器性能良好,测试性能和仿真结果基本吻合。     

Novel Coherence-Free RF/Microwave Photonic Bandpass Filter

A new structure for realizing an equivalent multitap bandpass filter response without coherent interference and phase noise limitations is presented. It is based on intensity modulating a continuous-wave light multiple times to obtain many taps, and also enables windowing to be employed. Experimental results are presented that demonstrate a multiple-tap bandpass filter with high rejection ratio and with no coherence and phase-induced intensity noise limitations.      

Ultra Wideband Bandpass Filter Using Embedded Stepped Impedance Resonators on Multilayer Liquid Crystal Polymer Substrate

This letter proposes an ultra wideband (UWB) bandpass filter (BPF) based on embedded stepped impedance resonators (SIRs). In this study, broad side coupled patches and high impedance microstrip lines are adopted as quasi-lumped elements for realizing the coupling between adjacent SIRs, which are used to suppress stopband harmonic response. An eight-pole UWB BPF is developed from lump-element bandpass prototype and verified by full-wave simulation. The proposed filter is fabricated using multilayer liquid crystal polymer (LCP) process and measured using vector network analyzer. Good agreement between simulated and measured response is observed. The measurement results show that the fabricated filter has a low insertion loss of 0.18 dB at center frequency 6.05 GHz, an ultra wide fractional bandwidth of 127.3% and excellent stopband rejection level higher than 32.01 dB from 10.9 to 18.0 GHz.