基于枝节加载型SIR的可调滤波器

基于枝节加载型阶梯阻抗谐振器(SIR)设计了一种加载变容二极管的微带可调带通滤波器。SIR结构利于抑制高次谐波且可实现滤波器的小型化,提出的模型通过在SIR的中心平面加载2个枝节构成多模谐振器。通过奇偶模方法分析了枝节加载型SIR的谐振特性;通过加载变容二极管实现了对滤波器奇偶模谐振频率的独立控制,利用变容二极管容值的变化实现了滤波器的中心频率可调,中心频率随变容二极管偏置电压的增加而增大。该可调滤波器实现了在0.82~1.17 GHz范围内中心频率可调且插入损耗小于5 dB,回波损耗大于10 dB。     

基于方开环谐振器的双陷波超宽带滤波器

针对超宽带系统易受窄带信号干扰的问题,设计了一种可以抑制无线局域网络(WLAN)和卫星通信信号干扰的双陷波超宽带带通滤波器。该滤波器的主要谐振结构由T型枝节加载的多模谐振器组成,改进的T型枝节增加了两个传输零点,同时减小了滤波器尺寸;通过耦合方开环谐振器,实现了两个陷波特性,调节谐振器尺寸,可以得到所需的陷波频率。测试结果表明,该滤波器的尺寸仅16.7mm×8.5mm,中心频率为6.9GHz,通带为3.0~10.8GHz,陷波中心频率在5.8GHz和8.04GHz,衰减最低点分别为-27dB和-18dB,仿真与测量结果有较好的一致性。     

基于双枝节“U”型谐振器的双频段微带带通滤波器

利用一种新型的双枝节"U"型谐振器结构,设计了一款双通带微带带通滤波器。该谐振器是在"U"型谐振器的中间和侧臂上各引入了一个枝节得到的,调节侧臂上枝节的特性导纳能够在不改变一次谐波与基波频率比f_1/f_0的情况下自由改变二次谐波与基波频率比f_2/f_0的值,该特性能在实现指定的双通带的同时获得较好的带外抑制性能。对中心频率分别为0.9GHz和1.36GHz,相对带宽分别为12%和4%的双频段的微带带通滤波器进行了仿真和测试,测试结果与仿真结果吻合良好,证实了该双枝节谐振器的有效性。     

基于加载非对称开路枝节谐振器的带通滤波器

基于新型的加载非对称开路枝节的阶梯阻抗谐振器,设计了一种具有高频率选择性的单频微带滤波器.该滤波器采用非对称的开路枝节作为容性负载,抑制高次杂散频率,具有较宽的上阻带,中心频率(2.4 GHz)处的插入损耗为0.6 dB.与传统结构相比,该滤波器在相同的谐振频率下尺寸减小了45％.调整新型阶梯阻抗谐振器的尺寸,还能实现中心频率为3.5 GHz单频和2.4 GHz/3.5 GHz双频带通滤波器.     

一种中心枝节折叠的新型超宽带滤波器

为了改善超宽带滤波器存在插入损耗较大,带外抑制特性较差等问题。采用中心加载折叠枝节多模谐振器结构,设计了一种新型超宽带滤波器。改变该滤波器多模谐振器的参数,可调节谐振器的谐振频率。该滤波器整体性能良好,具有结构紧凑,尺寸小,插入损耗小及带外抑制特性好等优点。仿真结果表明,该滤波器的中心频率为6.85GHz,通带为3¹0.7GHz,实现相对带宽112%。实物测试结果与仿真结果基本一致。     

12 GHz枝节匹配宽带微带均衡器

给出了一种匹配良好的宽带微带均衡器的设计。它由在枝节上加载了薄膜电阻的微带枝节谐振器构造而成。通过大量的试验和仿真研究了电阻值对谐振器的影响。当加载薄膜电阻在枝节谐振器上时，可以得到可调的品质因数。利用HFSS分析可以看到电阻加载的枝节谐振器不仅频率可调，而且衰减可调、品质因数可调。文中利用四个加载了不同阻值的枝节谐振器得到了一个12GHz带宽的微带均衡器，给出了结构图和特性曲线。结果表明这种加载电阻的谐振器结构很适合宽带微带均衡器设计。     

基于枝节线加载谐振器的可调滤波器设计

传统基于变容二极管的双频电可调滤波器由于外部容值的加入,该类滤波器的插损变大,同时相对带宽锐减。基于多模谐振器结构,提出了一种新型的工作频段独立、电可调的双频带通滤波器。该滤波器由短路枝节线加载谐振器和一对1/4 波长谐振器组成。在各自的谐振器末端加载带有变容二极管的外部偏置电路,1/4 波长谐振器构成第一通带,短路枝节线加载谐振器构成第二通带,两通带之间互不干扰,单独调节。应用奇偶模分析法及调节耦合间距的方法,确保双通带均出现两个极点,保证其带宽的稳定性。该电可调滤波器第一通带可调范围为0.7 ~0.85 GHz,第二通带可调范围为0.9 ~1.05 GHz,同时双频带的相对带宽基本保持在10% 以上,较以往的双频电可调滤波器,该款滤波器的相对带宽有了较为明显的提升。     

基于枝节加载谐振器的新型三频带通滤波器设计

提出了一种新型平面三频带通滤波器,该滤波器由一个加载短路枝节的阶梯阻抗谐振器,一对加载开路枝节的背靠背E型谐振器,以及包含源负载直接耦合的馈电结构组成.所采用的枝节加载谐振器的多模工作特性使滤波器的体积大大减小,同时每个通带的位置及其耦合特性都能够独立调谐.另外,通过源负载直接耦合引入通带两侧的传输零点,实现了滤波器良好的频率选择性.最后设计并加工了一款高选择性小型化三频带通滤波器,其三个通带的中心频率分别为2.0GHz,3.95GHz和6.35GHz,插入损耗均小于2.5dB,带内回波损耗均优于14dB,实验结果与仿真结果吻合良好.     

基于折叠枝节加载多模谐振器的超宽带滤波器

针对超宽带滤波器的插入损耗和选择性问题,提出一种基于折叠枝节加载多模谐振器结构的超宽带滤波器。通过调节谐振器的阻抗比及电长度比,可以控制谐振频率。仿真与实验结果吻合良好,表明采用折叠枝节加载形式,可以使滤波器具有低插入损耗和良好的选择性。通带范围在2.9~10.7 GHz,带内插入损耗优于1 d B,实现相对带宽114%。     

基于环形谐振器的平衡式带通滤波器

提出了一种基于多模环形谐振器实现的平衡式带通滤波器, 其主要由加载了电阻和短路枝节的环形谐振器和两对平衡端口构成.所提出的滤波器能够以单个谐振器获得差模的双模响应, 并且具有结构简单, 共模抑制高, 带宽可进行有限控制(4% ~ 9%)的优点.为验证理论预期的可实现性, 在RO4003C基板上设计了一个工作在1.87 GHz的平衡式带通滤波器.实验结果表明该滤波器的20-dB阻抗匹配带宽为8.9%, 中心频率处的插入损耗为0.86 dB, 在1 ~ 3 GHz频率范围内的共模抑制大于30 dB.     

Design of Dual-Band Bandpass Filters Using Stub-Loaded Open-Loop Resonators

In this paper, open-loop resonators loaded by shunt open stubs are proposed to design compact dual-band bandpass filters with improved out-of-band rejection characteristics. The second passband of the dual-band filter is obtained by tuning higher resonant modes of the open-loop resonator by the stub length and position. A tapped-line input/output feed structure is used for external coupling. Required external coupling is obtained by adjusting the tapping position and dimension of the stub-loaded resonator. A lossless transmission line model is used to determine the resonance properties of the resonator and the external quality factor. Theoretical predictions are verified by the experimental results of three dual-band filters.     

Discriminators for Instantaneous Frequency Measurement Subsystem Based on Open-Loop Resonators

The authors have studied a new way to design an instantaneous frequency measurement subsystem (IFMS). The method is based on bandstop filters. The device uses rectangular open-loop resonators instead of delay lines. The resonance frequency is adjusted by a resonator perimeter that must be approximately a half-wavelength long, and also by coupling distance between the resonators and the main transmission line. Simulated and experimental results are presented for a 5-bit IFMS.     

SIR带状线带阻滤波器的设计

将具有阻带特性的微带马刺线结构引入到带状线中,设计了一款中心频率为2.32 GHz,相对带宽为9.5%,阻带衰减为50 dB的三阶马刺线式带阻滤波器。相比于传统的并联开路短截线型带阻滤波器,马刺线式带阻滤波器的横向尺寸大为减小,结构更加紧凑。采用SIR(stepped-impedance resonator)结构,按相同指标设计了一款三阶SIR马刺线式带阻滤波器。与马刺线式带阻滤波器相比,SIR马刺线式带阻滤波器结构更为紧凑,纵向尺寸缩小约17%,并具有更好的谐波抑制特性。     

High-selectivity single-ended and balanced bandpass filters using ring resonators and coupled lines loaded with multiple stubs

High-selectivity single-ended and balanced bandpass filters (BPFs) using dual-mode ring resonators and coupled lines loaded with multiple stubs are proposed in this paper. With the help of the loaded short-circuited and open-circuited stubs, six deep transmission zeros (TZs) from 0 to 2f₀ (f₀: center frequency of the passband) can be realized in both of single-ended and balanced BPFs to improve the stopband suppressions. The functions of the loaded short/open stubs and calculated analysis of TZs’ positions have been presented. For further demonstration, two examples of single-ended BPF and balanced BPF with high common-mode suppression are designed and fabricated, whose center frequencies are both at 2.1 GHz. Their measured 3-dB fractional bandwidths are 23.7% and 24.7% (differential-mode), respectively. The simulated results and measurements of these two filters are in good agreement.     

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.     

一种新型超宽带带通滤波器的设计

针对超宽带(UWB)系统易受无线网络信号干扰及传统的超宽带带通滤波器阻带较窄,不能有效抑制谐波的问题,提出了一种新型的UWB带通滤波器,该滤波器由两级交指梳状耦合谐振器级联组成,通过增加耦合指的个数来实现陷波特性,然后在两个交指谐振器的中间添加一个槽线锥形谐振器,使该滤波器具有抑制高次谐波特性,达到拓宽高阻带的效果,同时由于槽线谐振器的加入,陷波频段的抑制电平进一步提高.实验结果证明,所设计的滤波器既能保证3.1～10.6 GHz频段内的插入损耗小于3 dB,陷波频段为5.7～5.8 GHz,陷波频段的抑制电平高达-43 dB,同时又能拓宽高频阻带.     

A novel dual-band tunable notch filter with controllable center frequencies and bandwidths

This article proposes a new dual-band tunable bandstop filter. This tunable filter is composed of two separate parts, the transmission line, and coupled stubs that each connect to three varactors. The center frequency and bandwidth in each band can be controlled individually. Moreover, the LC equivalent circuit of the proposed filter is calculated, and the results are simulated. In the proposed filter, the simulations show that the first stopband can be tuned in a frequency range from 1.2 to 1.9 GHz with 10-dB absolute bandwidth 310 ± 30 MHz, whereas the second stopband varies from 2.5 to 3.3 GHz with the 10-dB absolute bandwidth 720 ± 20 MHz. These two stopbands can also be tuned independently. Furthermore, the bandwidth of each fixed center frequency can be changed easily. The fabricated proposed filter validates the simulation results. The compact filter has an effective size of 9 × 27.5 mm².     

Wide-Stopband Microstrip Bandpass Filters Using Quarter-Wavelength Stepped-Impedance Resonators and Bandstop Embedded Resonators

Novel compact microstrip bandpass filters (BPFs) with extended stopband are proposed using both quarter-wavelength (lambda/4) stepped-impedance resonators and bandstop embedded resonators. First, by properly designing the impedance and length ratios of the stepped-impedance resonators, the developed filter may be made compact and its spurious harmonics may be pushed to the higher frequency region. Next, by suitably designing the bandstop structure so as to suppress the lower spurious harmonics of stepped-impedance resonators and then embedding the bandstop structure into the lambda/4 resonators, one may realize the BPFs with wideband spurious suppression. In particular, by connecting the bandstop embedded resonators to the input/output ports, a compact fourth-order BPF of dimension 0.089 lambdag times 0.27 lambdag is implemented and its stopband is extended up to 8.25 f ₀ with an adequate rejection of greater than 32.49 dB, where f ₀ is the passband center frequency and lambdag is the microstrip guided wavelength at f ₀.     

A reduced-size dual-mode bandpass filter with capacitively loaded open-loop arms

A novel type of dual-mode microstrip bandpass filter using degenerate modes of a dual-mode microstrip square loop resonator with capacitively loaded open-loop arms is proposed. Such a dual-mode bandpass filter with a 0.75% bandwidth at the center frequency of 1.603 GHz is designed and fabricated to demonstrate the design of reduced-size microstrip filters. It is shown that the proposed filter has a size reduction of about 59% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop and ring resonator filter.     

Novel Centrally Loaded Resonators and Their Applications to Bandpass Filters

This paper presents several novel centrally loaded resonators and their applications to various types of bandpass filters. Based on the theoretical analysis, it is found that the even- mode resonance of the proposed resonators can be conveniently controlled without affecting the responses at the odd-mode resonant frequencies. Benefiting from this feature, the resonator can be utilized to design not only harmonic-suppressed bandpass filters and dual-band bandpass filters but also tunable bandpass filters. The tunable filter offers a fixed passband and a tunable one. The center frequency of the upper passband can be electrically tuned, whereas the performance of the lower one is maintained constant. To demonstrate these applications, four filters using the proposed resonators are implemented. The experiments verify the theoretical predictions and simulations.