Stopband-Extended Balanced Bandpass Filter Using Coupled Stepped-Impedance Resonators

A novel fourth-order balanced bandpass filter is proposed based on the half-wavelength (lambda/2) stepped-impedance resonators (SIRs). By properly adjusting the parameters of each SIR, the proposed filter may be made compact and its stopband may also be extended simultaneously. Specifically, a balanced filter with acceptable common-mode rejection is implemented with its differential-mode and common-mode stopbands extended up to 5.5 f_o ^d, where f_o ^d is the center frequency of differential-mode passband.     

Novel Balanced Dual-Band Bandpass Filter Using Coupled Stepped-Impedance Resonators

A novel balanced dual-band bandpass filter, using coupled stepped-impedance resonators (SIRs), is proposed in this letter. The differential- and common-mode equivalent half circuits are given. By properly designing the resonators, associated with the filter composed of eight SIRs, dual-band differential-mode bandpass response can be obtained. To improve the common-mode suppression level, two open stubs with different lengths are added to the connection point of two resonators. A prototype balanced filter operating at 2.4 and 5 GHz has been realized to validate the proposed concept and theory.      

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     

Balanced Dual-Band BPF With Stub-Loaded SIRs for Common-Mode Suppression

A new fourth-order balanced dual-band band-pass filter (BPF) designed using four coupled bi-section half-wavelength ( $lambda /2$) stepped-impedance resonators (SIRs) is presented. To obtain the required differential-mode (DM) operation with suppressed common-mode (CM) transmission, the SIRs were designed to have the same odd-mode, but different even-mode, resonant frequencies. For that purpose, the two inner SIRs were loaded at the center with T-shaped open stubs of different dimensions so that their even-mode resonant frequencies are shifted away from those of the outer SIRs and that their odd-mode ones remain almost intact. For the fabricated prototype BPF, the measured minimum DM insertion losses for the first and second bands are 2.4 and 2.82 dB, respectively, whereas the measured CM insertion loss is larger than 25 dB in 1–7 GHz.      

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.     

A Differential-Mode Wideband Bandpass Filter on Microstrip Line for UWB Application

A differential-mode wideband bandpass filter (BPF) on microstrip line is proposed with good common-mode suppression. A four port two stage branch-line differential-mode BPF is first designed. Then, open circuited stubs are attached to the middle of two of the vertical branches. As such, its two-port bisection becomes a bandpass or bandstop filtering topology under differental- or common-mode excitations, respectively. The lengths and widths of these stubs can be properly adjusted to produce a highly attenuated and widened stopband under the common-mode operation. Finally, a wideband differential-mode BPF is designed and fabricated. The predicted and measured performances are in good agreement with each other, showing good common-mode suppression with an insertion loss higher than 20 dB over the differential-mode passband with a fractional bandwidth of 65%.     

Compact Electronically Switchable Parallel-Coupled Microstrip Bandpass Filter With Wide Stopband

In this letter, a compact electronically switchable parallel-coupled microstrip bandpass filter (BPF) based on quarter- wavelength resonators and p-i-n diode switch is proposed. The proposed filter occupies only half the circuit size of the conventional parallel-coupled filter. In addition, the type and length of each coupled-line section is suitably chosen such that the inherent transmission zeros associated with the coupled-lines can be used to reject the spurious passbands effectively. By adding only one p-i-n diode along with a simple bias control circuitry, the proposed filter becomes electronically switchable with no current consumption when the filter is turned off. Specifically, a switchable fourth-order microstrip BPF with a center frequency f₀ of 2 GHz, passband insertion loss less than 3 dB, and wide stopband up to 7.7 f₀ in the ON state is demonstrated. The isolation of the filter is better than 30 dB from dc up to 7.7 f₀ in the OFF state.     

Multilayer Dual-Mode Dual-Bandpass Filter

A dual-mode dual-bandpass filter for the U-NII bands is proposed and demonstrated. Its effective size reduction is achieved by using a multilayer configuration. The first and the third layers incorporate microstrip dual-mode bandpass filters with operating center-frequencies of f₁ =5.2 GHz and f₂ =5.8 GHz, respectively. The second layer is used as a common ground plane for both filters, which also serves as a decoupling interface. Capacitive coupling transition is used to connect both filters to I/O coplanar waveguide (CPW) ports. Single and dual-band passband filter prototypes are designed, fabricated, and measured in this work, thus validating the design principle. Designed topologies of single passband filters with center frequencies of 5.2 and 5.8 GHz exhibit an out-of-band rejection better than 40 dB with a 3 dB bandwidth of 5.8% and 6%, respectively. The proposed multilayer dual-passband response with center frequencies of 5.2 and 5.8 GHz provide band-to-band isolation better than 30 dB. Measured insertion losses are lower than 2.76 dB, with 3 dB bandwidth lower than 5%.     

抑制共模噪声的SIW 平衡馈电差分缝隙天线阵*

提出一种利用差分天线在共模激励和差模激励下方向图不同来抑制共模噪声的方法,并基于该理论 设计了6×6 平衡馈电差分SIW 缝隙天线阵进行验证。该天线由6个宽边纵向SIW 缝隙天线子阵列组成。辐射缝隙 被设计为只在差模激励下辐射,达到抑制共模信号的目的。每个天线子阵采用平衡差分馈电方式,使用两个1分6 梳状功分器将6个子阵同时激励。整个天线使用标准PCB 工艺加工,为了测试共模和差模激励,分别设计了带有 180°相移的功分器和T型功分器用来生成差模和共模信号。在差模激励下,天线的最大增益为20.2dBi,S11幅值小 于-10dB 带宽为7.2%(39.6 ~43.8GHz),在共模激励下天线的最大增益为10.1dBi,在整个工作频段内S11幅值大于 -7dB。仿真和实验结果验证了该结构的SIW 缝隙天线对差模信号能够有效地辐射而对共模信号进行抑制。     

一种具有可重构陷波功能的差分宽带带通滤波器

文章提出了一种具有陷波可重构功能的差分宽带带通滤波器,具有良好的差模响应与共模抑制效果。所设计的差分带通滤波器通过采用对称的四阶分支线结构,在差模激励下可等效出电壁,在共模激励下可等效出磁壁。同时,该滤波器通过对称地耦合两个1/4波长的阶梯阻抗谐振器来产生所需频段的陷波特性,并通过改变阶梯阻抗谐振器上变容二极管两端的直流偏置电压来改变阶梯阻抗谐振器的电长度,从而调整陷波的频段。仿真和测试结果表明该差分带通滤波器的工作频带为2.7~7.3 GHz,相对阻抗带宽为92%。在工作频段中,差模回波损耗均大于10 dB,共模抑制大于15 dB。随着变容二极管两端直流控制电压从10.3 V变化到3.6 V,陷波的中心频率从5.6 GHz移动到6.1 GHz,同时滤波器宽带带通特性基本保持不变。     

Sharp-Rejection Wideband Bandstop Filters

In this letter, a novel transmission line configuration has been proposed to design a sharp-rejection, bandstop filter (BSF) with wide rejection bandwidth. The rejection bandwidth and the level of rejection are controlled by the characteristic impedances of the transmission lines. Design equations are obtained by using a lossless transmission line model. The proposed design has been verified in microstrip line by fabricating a prototype BSF of -20 dB fractional bandwidth of 100% at a stopband center frequency f₀ = 1.5 GHz. The filter structure is simple and easy to fabricate.     

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.     

基于双层扇形基片集成波导的双频平衡滤波器

提出了一种表面刻有一对互补开环谐振器(CSRR)的45°扇形基片集成波导谐振腔(SSIWR),设计并制作了一款结构紧凑且具有高选择性的双层双频平衡带通滤波器.分别利用具有带通特性的CSRR和谐振腔内的TM220模实现了差模双频响应;模式间的耦合以及缺陷地结构(DGS)的引入使得滤波器在通带附近产生4个传输零点,提高了带...     

Improved and compact 0.7 GHz tune-all bandpass filter

A compact tune-all bandpass filter is presented. This electronically tuned filter is based on series-coupled slow-wave resonators. It allows wide simultaneous and continuous tunings of centre frequency (+/-15% around 0.7 GHz) and bandwidth (from 50 to 100 MHz) with insertion loss IL<5.4 dB and return loss RL>11 dB. This two-pole bandpass filter exhibits also a very small surface of only 7.3times10^-3 lambda₀ ² and a -20 dB stop-band that extends up to 10 GHz     

一种基于传输线理论的新型GHz共模噪声抑制电路

基于传输线理论提出一种新型GHz宽阻带共模噪声抑制电路。利用双线传输线模型建立奇、偶模等效电路,在宽频带范围内准确预测了该电路结构的性能。实验结果表明:在1.9-4.5GHz频段内共模噪声抑制深度超-10dB,共模阻带相对带宽达81%;在dc-6GHz频段内差模插损小于3dB且差模信号群时延抖动较小,表明该结构可以很好地保证差模信号传输的信号完整性,性能优良。     

The Design of Coupled Resonator Bandpass Filter With Wide Stop-Band

A compact four-pole bandpass filter with multi-order spurious response suppression is proposed. The combination of dissimilar resonator structures with the same fundamental frequency but with different spurious frequencies may improve the stop-band rejection by the mutual cancellation of spurious responses. The measured results show that better than -20 dB rejection levels in the stop-band up to 4.5 f₀ have been obtained. Moreover, an embedded-resonator topology is used, which makes the structure of filter to be more compact.     

Stopband performance improvement of rectangular waveguide filtersusing stepped-impedance resonators

Rectangular waveguide stepped-impedance resonators (SIRs) are analyzed and employed in the design of an X-band filter with center frequency f₀ = 10 GHz and a bandwidth of 100 MHz. An attenuation of 80 dB is held up to 23.1 GHz and, compared to standard uniform-impedance-resonator filters, a reduction in length of 55 % is achieved at the expense of an increased insertion loss from 0.6 to 1.5 dB. The second resonance of the fundamental TE₁₀ mode can be controlled by adjusting the length and impedance ratio of each resonator. A design procedure that takes into account step discontinuities is described and applied to the design of a number of SIR filters. Finally, the presented theory is supported with experimental results     

Novel approach to the design of I/Q demodulation filters

A novel filter design approach to digital I/Q demodulation is proposed. Two possible realisations are presented using this approach. The first one is based on the highpass filter method which is suitable for B⩽f₀ and while the other realisation is based on the lowpass filter method suitable for B⩽f₀, where B and f ₀ are the IF signal bandwidth and the IF frequency, respectively. Both new realisations maintain the advantages of an earlier lowpass approach such as zero DC offset, matched channel frequency responses, and good performance over a wide bandwidth. At the same time, the new highpass filter realisation method possesses higher computational efficiency than other wideband approaches reported in the literature     

一种基于互补谐振结构的宽带共模噪声滤波器

提出了一种用于高速差分信号传输的宽带共模噪声滤波器,采用在差分线正下方参考地平面上刻蚀内外互补的共面波导1/4波长谐振器和Z字形短路枝节线来实现。滤波器采用内外互补耦合λ/4开路枝节线谐振器结构,有效减小了横向尺寸,利用Z字形枝节线增大互感以改善滤波器的带内增益平坦度,最后用级联实现了共模噪声抑制阻带的展宽。仿真和测试结果表明,该滤波器在4.1~12.5 GHz频率范围内实现了20 dB的共模噪声抑制,共模阻带相对带宽(FBW)为101%,尺寸仅为0.78λ_g×0.18λ_g(15.8 mm×3.6 mm),其中λ_g为阻带中心频率处对应的波长。且该结构在实现共模噪声宽带抑制的同时,还可有效保证差分信号传输特性良好。     

Differential-mode ultra-wideband bandpass filter on microstrip line

A differential-mode ultra-wideband (UWB) bandpass filter on a microstrip line is proposed and implemented with good common-mode suppression. A sixth-stage branch-line differential-mode bandpass filter is designed with the specified UWB passband. By introducing two pairs of open-circuited stubs in the symmetrical plane, the differential-mode frequency response remains unchanged but its common-mode counterpart is reshaped to achieve the stopband in the overall UWB. A filter is then fabricated for experimental verification of the proposed technique.