A widely tunable bandpass filter adopting novel fully tunable resonators

A widely tunable bandpass filter adopting a novel fully tunable resonator is proposed in this letter. The fully tunable resonator is mainly consisted of an open ring, a frequency tuning structure, and a coupling tuning structure. Adopting the fully resonators, the center frequency, the input/output external Q value, and the coupling coefficients can be tuned at the same time. And the tuning range of a tunable filter adopting the novel fully tunable resonators can be expanded. The fully tunable resonators can be combined to achieve more excellent suppression performance. A widely tunable bandpass filter consisted of five fully tunable resonators with 86.5% frequency tuning range is designed, fabricated, and measured. The simulated results are in good agreement with the measured ones.     

A bandpass filter using modified half mode substrate integrated waveguide technique

This article reports a novel bandpass filter using modified half mode substrate integrated waveguide technique. The via‐fences are deployed as impedance inverters for the proposed filter to reduce its footprints, which are extracted by using a full‐wave electromagnetic simulator HFSS for the filter design. Detailed design procedure is discussed. A bandpass filter having a center frequency of 10.03 GHz and a pass band from 9.78 to 10.3 GHz is designed for demonstration, and experiments are carried out for the validation. Good agreements between experiment and simulated results are obtained, which show that the proposed filter has a compact size, a low insertion loss, and a high selectivity. It is attractive for the radio communication system. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:277–281, 2015.     

A novel wideband bandpass filter based on CSRR‐loaded substrate integrated folded waveguide

A novel wideband bandpass filter based on folded substrate integrated waveguide (FSIW) is presented in the article. Five square complementary split‐ring resonators (CSRRs) are etched in the middle layer of the FSIW. By adjusting the physical size of the CSRR structure, the resonant frequency of the CSRRs can be tuned at the same time and the stopband performance can be changed. As transverse electromagnetic (TEM) mode can be transmitted in the stripline, FSIW excited by stripline shows wider passband than that excited by microstrip line directly. To achieve perfect impedance matching, two microstrip lines to stripline transitions are added in two ports of the filter. The proposed bandpass filter exhibits compact size, high selectivity, good stopband rejection, lower radiation loss, and wideband performances. The measured results show that the fractional bandwidth of the filter is about 35.5%. The measured return loss is better than 15 dB from 4.84 GHz to 6.90 GHz, and the insertion loss is less than 1.2 dB. The comparison between the simulated results and the measured ones validate the possibility of the technology that combines the FSIW and CSRR.     

A tunable third‐order bandpass filter based on combining dual‐mode square‐shaped substrate integrated waveguide resonator with triangular‐shaped resonator

A frequency reconfigurable third‐order bandpass filter based on two substrate integrated waveguide (SIW) cavities is presented in this article. The purposed filter consists of a dual‐mode square‐shaped resonator and a triangular‐shaped resonator. In the square‐shaped cavity, four lumped capacitors are loaded as electrical tuning elements in the area where the electric fields of diagonal TE₂₀₁ and TE₁₀₂ modes are strongest. And an another capacitor is loaded at the suitable region of the triangular‐shaped cavity. Square‐shaped cavity introduces two transmission zeros and the triangular‐shaped cavity can suppress out‐of‐band spurious modes. The method that combines the resonators with different shapes and multiple modes into an organic whole cannot only achieve synchronous tuning but also have complementary advantages and improve out‐of‐band rejection. To verify its practicality, a SIW reconfigurable bandpass filter is simulated when the capacitance value varies from 0 to 1.4 pF and measured at 0.7, 0.8, and 0.9 pF, respectively. Measured results show that when the center frequency is tuned from 3.42 to 3.52 GHz, the proposed filter exhibits good tuning performance with insertion loss of less than 2.5 dB and return loss of better than 10 dB, which is suitable for fifth‐generation communication system.     

梳状线可调带通滤波器的设计与仿真

针对现有的微带可调滤波器中心频率调节范围较窄的问题,依据梳状滤波器的原理和变容二极管的特性,设计出一种梳状线可调带通滤波器,经ADS仿真可得其中心频率可调范围达到0．49～5．08GHz、相对带宽仅为6．1％～9．4％,该梳状线可调带通滤波器具有中心频率调节范围很宽、结构简单、易于实现、易于扩展等优点,在工程上具有一定的推广应用价值。     

A novel substrate integrated waveguide equivalent inductive‐post filter

A novel substrate integrated waveguide equivalent inductive‐post filter is presented and optimally designed by HFSS and equivalent circuit method. The filter is fabricated with a standard low cost PCB process. Measured data are in agreement with the simulated results. Excellent performance in selectivity, out of band rejection and passband insertion loss are shown. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Compact reconfigurable triple‐mode triple‐band substrate integrated waveguide bandpass filter

In this study, a reconfigurable triple‐band triple‐mode substrate integrated waveguide filter is designed and fabricated in the C‐band spectrum. A novel and simplified design procedure based on analytical equations is proposed. The filter design also benefits from a reconfigurable structure, using metallic via holes as perturbation, allowing wide‐band selectivity of the C‐band spectrum (from 4.4 to 6.9 GHz). Moreover, the filter benefits from a magnetic coupling solution between the resonators, which only couples the first three modes and rejects the next resonating modes. Therefore, a large bandgap in the spectrum is achieved. The proposed structure is fabricated and measured, and a high similarity between the simulation and fabrication is observed. The measured results show that the first band can be tuned in the frequency range of 4.4 to 7, the second band can be tuned in the range 5.8 to 7.7 GHz, and the third band from 5.8 to 7.7 GHz. The insertion loss 1.5 to 2.5 dB, 2 to 3 dB, and 2.5 to 3.5 dB for the first, second, and third bands, respectively.     

Design and optimization of a planar folded substrate integrated waveguide bandpass filter exploiting aggressive space mapping

Substrate integrated waveguide (SIW) is a new structure for microwave transmission. In this paper, a planar folded sixth‐order SIW filter is designed with aggressive space mapping (ASM) algorithm. Its center frequency is 22 GHz, 3 dB bandwidth 1 GHz, and in‐band return loss 22 dB. The filter satisfies design specifications after four iterations, and is fabricated using micro‐electro‐mechanical systems (MEMS) technology with a chip size of 7.5 mm × 8.5 mm × 0.4 mm. Measurement results show that the center frequency of the filter measures at 22.2 GHz, 3 dB bandwidth at 1 GHz, insertion loss at 3.57 dB, return loss at 22 dB and out‐of‐band rejection at 40 dB.     

A tunable 0.86‐3.83 GHz bandpass filter with high selectivity

This letter presents a tunable bandpass filter (BPF) with wide tuning range of center frequency and high selectivity. The wide frequency tuning range is achieved by two pairs of switchable varactors‐tuned parallel coupled line resonators with direct‐feed structure, which can be switched to lower and higher frequency resonator modes by using p‐i‐n diodes. Since the electromagnetic mixed coupling and frequency‐variant source‐load coupling are incorporated in this configuration, three self‐adaptive transmission zeros (TZs) close to the tunable passband are obtained. Also, three TZs can almost keep the same relative location of passband to achieve continuous high selectivity and good out‐of‐band rejection over the whole frequency tuning range. Meanwhile, by selecting a proper coupling region, a constant fractional bandwidth (CFBW) in the frequency tuning process can be realized. For verification, a tunable 0.86‐3.83 GHz BPF with a 12% CFBW and high selectivity is designed, fabricated and measured. The experimental results show the proposed filter has the advantages of wide tuning range and high selectivity.     

Miniaturized substrate integrated waveguide 5G LTCC bandpass filter exploiting capacitive loaded cavities

In this article, a compact bandpass filter with a pair of transmission zeros exploiting capacitive loaded cavities is presented. The proposed filter structure is mainly composed of coplanar waveguide (CPW) feeding structures and four substrate integrated waveguide (SIW) resonators. The size of the filter has been greatly reduced due to the capacitive loaded circle metallic septum and the vertical coupling of stacked cavities in three dimensional structures by low temperature co‐fired ceramic technology. The filter not only achieves the advantages of high‐selectivity, a much wider upper stopband bandwidth, but also realizes a miniaturized volume of 3.35 × 2.10 × 0.66 mm³. The simulated and measured results show the bandpass filter achieves a center frequency of 28 GHz with 3 dB fractional bandwidth of 8%. The filter is suitable for application in 5G wireless communication.     

基于共平面波导的可调低通滤波器的设计和制作

介绍了一种使用多触点MEMS开关实现的新型可调微波MEMS低通滤波器,应用MEMS制作工艺在石英衬底上实现滤波器结构.滤波器基于慢波共平面波导周期性结构,具有尺寸小、插损低、可与单片微波集成电路工艺兼容等优点.滤波器截止频率的大小取决于MEMS开关的状态.实验结果表明,当MEMS开关受到激励时,低通滤波器的3-dB截止频率从12.5GHz转换至6.1GHz,带内纹波小于0.5dB,带外抑制大于40dB,开关的驱动电压在25V左右.     

A folded dual‐mode bandpass filter with circular waveguide

In this article, a folded circular waveguide dual‐mode filter without tuning screws is designed for the fifth‐generation (5G) mobile communication system. The folded filter is composed of two stacked circular cavities operated at 3.5 GHz. Each cavity has two resonant modes, which can generate and control two transmission zeroes at specific frequencies. Through a coupling iris, the two single‐cavity filters are connected together, and can control four poles, which helps to expand the 3dB fractional bandwidth to 11.4%. The measured insertion losses are around 0.5 dB in the passband (from 3.4–3.6 GHz). The experiment results show an excellent agreement with the simulation results. Such folded filters have the advantages of very low insertion loss, compact size, high frequency selectivity, and low cost.     

A novel E‐plane substrate inserted bandpass filter with high selectivity and compact size

In this article, a novel E‐plane substrate inserted waveguide bandpass filter with high selectivity and compact size is proposed in Ka‐band. By integrating an extra resonator between two metal septa, the E‐plane waveguide filter is achieved with two transmission zeros at both sides of the passband which contribute to the high‐skirt selectivity. One sample is fabricated, whose total length is just 5 mm, namely, less than 0.5 and the minimum insertion loss is only about 0.3 dB. Good agreements between simulated and measured results are obtained. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:451–456, 2014.     

Design of miniaturized substrate integrated coaxial line bandpass filters with quarter‐wavelength spiral resonator

In this article, several miniaturized bandpass filters (BPFs) with substrate integrated coaxial line quarter‐wavelength spiral resonators were proposed. The coupling coefficients and external quality factors of proposed structures were examined by using the commercial simulation software. With different combinations of the proposed resonators, three two‐order and two high‐order miniaturized BPFs operating at 1.2 GHz with 3‐dB fractional bandwidth of 8% were designed, fabricated, and measured. The measured results showed that all the return losses were better than 10 dB over the entirely passbands, and the overall circuit sizes of two‐order and high‐order BPFs were only 0.044λ₀ × 0.028λ₀ and 0.047λ₀ × 0.047λ₀, where λ₀ is the wavelength in free space at the center frequency of the passband. Good agreements were observed between the simulated and measured results. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:489–495, 2016.     

Variable bandwidth,wide tunable frequency,voltage tuned filter

This article discusses the development of an electronically tuned filter capable of a wide tunable frequency range and simultaneous 3-dB bandwidth variations at any frequency within its tuning range. Varactor-tunable filters are designed using high-dielectric, soft-substrate material for printed resonators as well as also high-Q ceramic resonators, and their test data are compared. Greater than 50% tuning range with low insertion loss at a center frequency in the L and S frequency bands is demonstrated with a 4:1 change in 3-dB bandwidth—30 to 120 MHz for printed resonators and 14 to 46 MHz for ceramic resonators. The concept of tuning a filter's 3-dB bandwidth with voltage is demonstrated and the effect of the bandwidth tuning elements on the tunable filter performance is discussed. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 64–72, 2004.     

Compact,dual-band,and hybrid filter based on combline and substrate integrated waveguide resonators

A novel compact hybrid dual-band bandpass filter based on combline and substrate integrated waveguide (SIW) resonators is proposed. By exploring an SIW-based hybrid cavity structure, a controllable dual-band response is achieved. The low-frequency passband is obtained by the combline, or mushroom resonators and the high-frequency passband is formed by the TE₁₀₁ and TE₃₀₁ modes. Unlike other designs that use the main mode and the high-order mode of the same resonator, we innovative use the TE301 mode of the rectangular cavity and cleverly divide this rectangular cavity into two small cavities, and use its TE101 mode to form the second passband with the TE301 mode of the large cavity. To improve the selectivity and out-of-band suppression, three transmission zeros are configured in this design. In order to verify the proposed design concept, a compact dual-band filter using this hybrid resonance structure is fabricated and measured. It demonstrates good filtering performance, including a compact size of 0.45 × 1.09 λ₀, a low insertion loss of 0.57 and 1.67 dB in the two bands, and a high-design flexibility.     

Development of a 3D HUD using a tunable bandpass filter for wavelength multiplexing

A 3D stereoscopic head‐up display using a tunable bandpass filter to perform left and right image spectral separation is presented. Using a single filter reduces the size and the cost of the head‐up display optical engine and enables each spectral band to be accurately tuned. Experiments performed on the first prototype demonstrate the ability to continuously tune the bandpass frequency on 30‐nm range while keeping a 20‐nm bandwidth. Such a system avoids the use of a bulky and costly rotating wheel and enables the use of holographic optical elements known to be wavelength selective.     

MEMS集成滤波器技术

滤波器是频率转换系统(如,调谐电路、接收器)的基本构成模块。借助于MEMS技术实现的滤波器不仅带来插入损耗、功耗、线性等性能的改善,也有利于将整个通信前端集成到单一芯片上。综述了MEMS可调滤波器的研究进展。与单一利用MEMS电容的调变实现频率可调的滤波器相比,分形可调MEMS滤波技术有更小的插入损耗和更宽的调频范围。     

A balanced dual‐band bandpass filter with independently tunable differential‐mode frequencies

A balanced dual‐band bandpass filter (BPF) with independently tunable differential‐mode (DM) frequencies is proposed in this letter. The proposed BPF is composed of complementary split‐ring resonators (CSRRs) etched on the ground and varactors loaded on the resonators. A balanced stepped‐impedance microstrip‐slotline transition structure is introduced to transfer the DM signals successfully and block the common‐mode (CM) signals transmission. Good DM transmission and CM suppression can be achieved. Moreover, by changing the reverse bias voltages of the varactors loaded on coupling CSRRs, two DM resonant frequencies of the proposed balanced BPF can be tuned independently. To verify the feasibility of the design method, a balanced BPF with DM frequency ranging from 0.80 GHz to 1.12 GHz and 1.55 GHz to 2.05 GHz is fabricated and measured. Good agreement between the simulation and measurement results demonstrate the validity of the design.     

A novel bandpass filter based on TEM‐SIW cavity

A novel microstrip filter based on transverse electromagnetic (TEM)‐substrate integrated waveguide (SIW) cavities is firstly proposed in this letter. Compared to the traditional SIW cavities, the TEM‐SIW cavities have more compact size and higher Q value. Then, two bandpass filter adopting TEM‐SIW cavities is designed and one of it is fabricated. Both simulated and measured results are presented. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.