Frequencies Of Transmission Zeros Research Articles

Novel Topology and Design for Wideband Bandpass Filter With Frequency- and Attenuation-Reconfigurable In-Band Notch

A novel topology and the design method are proposed for a wideband bandpass filter (BPF) with frequency- and attenuation-reconfigurable in-band notch by engineering the complex frequencies of transmission zeros. The proposed topology consists of a fifth-order wideband BPF and two coupled notch resonators. With the two coupled notch resonators, a pair of complex in-band transmission zeros are formed. By controlling the frequency difference between the two notch resonators, a frequency- and attenuation-reconfigurable notch can be obtained in the passband of the wideband BPF. A matrix analysis method is presented to characterize the frequency- and attenuation-tunable in-band notch precisely. The relationship between complex transmission zeros and in-band attenuation is also investigated. To demonstrate the proposed techniques, a prototype using microstrip and evanescent mode resonators is designed and fabricated. The proposed wideband BPF exhibits a reconfigurable in-band notch with frequency tuning from 1.494 to 2.004 GHz and attenuation tuning from 2 to 79 dB. The simulated and measured results are in good agreement with each other, validating the proposed design and method.

An Intrinsically Switched Tunable CABW/CFBW Bandpass Filter

In this paper, a novel intrinsically switched tunable bandpass filter based on a dual-mode T-shaped varactor-loaded resonator is presented. The varactors loaded in the T-shaped resonator are capable of efficiently tuning the resonant frequencies of the even and odd modes, as well as the transmission-zero frequency. Without any additional RF switches, the passband of the filter can be intrinsically switched off by adjusting the transmission zero to the resonant frequencies. In the switch-on state, the constant absolute bandwidth (CABW) or constant fractional bandwidth (CFBW) passband can be achieved by controlling the frequency space between the two resonances. For a demonstration, a 0.8–1.1 GHz intrinsically switched tunable bandpass filter with 74 MHz CABW or 8.5% CFBW was fabricated and tested. In the whole operating band with |S11| < 10 dB, the insertion losses for CABW and CFBW are better than 3.3 dB and 3 dB, respectively, and the isolations are better than 20 dB in the switch-off state. The measured results have a good agreement with simulated results, which verifies the design theory.

A Dual-Mode Microwave Resonator for Liquid Chromatography Applications

This work presents a microwave microfluidic sensor for high performance liquid chromatography (HPLC) applications. The sensor is based on a modified square ring loaded resonator (SRLR), where a transmission line and a ring are electrically shorted with a center gap. A microfluidic channel is bonded above the gap for liquid-under-test (LUT) measurement. When the dielectric constant of LUT is above a threshold value, two degeneration modes of the resonator are separated, resulting in two transmission-zero frequencies. The threshold dielectric constant can be easily tuned by the gap size. High sensitivity is achieved when LUT dielectric constant is close to the threshold value. These features enable the proposed resonator to be optimized for different microfluidic applications. To validate the design, three resonators with 10 μm, 30 μm and 90 μm gap sizes are built and tested with water-methanol solutions in various volume fractions. Additionally, the sensor is connected in series with HPLC system for caffeine and sucrose detection. The detection linearity is characterized by measuring water-caffeine samples from 0.77 ppm to 1000 ppm. A 0.231 ppm limit of detection (LOD) is achieved, revealing a comparable sensitivity with commercial ultraviolet (UV) detectors. The compatibility of the proposed sensor to gradient elution is also demonstrated.

Design of Microstrip Filters Using Paired Fan-Shaped Capacitors with Controllable Transmission Zeros

ABSTRACT In this paper, microstrip filters using paired fan-shaped capacitors with controllable transmission zeros are proposed. The paired capacitors are employed to replace the conventional single capacitor to reduce parasitic self-inductance. As a result, the rejection bandwidth and level have both been improved. In the simulated and measured results, several transmission zeros (TZ) have been created in the stopband without any jitters. The frequencies of TZs have been derived in the analysis process using the equivalent circuit. The out-of-band TZs can be controlled flexibly with the component values. The proposed method can be utilized to control the position of out-of-band transmission zeros flexibly to increase figure of merit (FOM) of low-pass filters.

Wide‐stopband and high selectivity step impedance resonator bandpass filter using T‐network and antiparallel coupled line

A wide-stopband attenuation with high-selectivity step impedance resonator (SIR) bandpass filter (BPF) is presented in this study. The T-network stubs are used to produce transmission zeros (TZs) close to the centre frequency ( f 0 ) with a high-selectivity. Moreover, the antiparallel coupled lines can produce a TZ at spurious frequency of conventional SIR BPF for all step impedance ratio ( K ). For the validation, a half-wavelength ( λ /2) SIR BPF with T-network stubs at the input/output ports was designed at f 0 of 2.6 GHz. From the experiment, the insertion and return losses at f 0 were determined to be 0.91 and 21.25 dB, respectively. The insertion and return losses were better than 1.1 and 16.5 dB, respectively, of the 180 MHz bandwidth. The TZ frequencies ( fZ 1 , fZ 2 , and fZ 3 ) were located at 1.69 GHz (0.63 f 0 ), 2.98 GHz (1.12 f 0 ), and 3.17 GHz (1.19 f 0 ), respectively, with a high selectivity. The stopband attenuation was better than 25 dB from DC to 2.23 GHz and from 2.89 to 9.82 GHz.

Filtering balanced-to-single-ended power dividing network

In this article, the filtering balanced-to-single-ended power dividing networks are proposed. Except the fundamental functions of differential-mode transmission, common-mode suppression, and out-of-phase single-ended output ports with isolation, the proposed designs show the advantages of wide controllable range of differential-mode bandwidth, multiple transmission zeros (TZs), and wide bandwidth for high out-of-band suppression. The frequencies of TZs, bandwidth, isolation, and common-mode suppression can be controlled by the parameters. For demonstration, three prototypes (Deigns I, II, and III) with two, four, or six TZs are implemented. The measured results show that design I (II and III) has an insertion loss of 0.38 dB (0.7 dB and 0.8 dB), an operating bandwidth of 12.5% (7.5% and 6.9%), and a bandwidth for 30-dB out-of-band suppression of 0.06f0 (0.09f0 and 0.14f0). The isolation and common-mode suppression inside the passbands of the three prototypes are all larger than 17 and 38 dB, respectively.

Compact Wideband Balanced Bandpass Filters With Very Broad Common-Mode and Differential-Mode Stopbands

Compact balanced bandpass filters based on a combination of multisection mirrored stepped-impedance resonators and interdigital capacitors are presented in this paper. The considered filter topology is useful to achieve wide bandwidths for the differential mode, with broad stop bands for that mode, as well as very efficient common-mode suppression. By conveniently adjusting the transmission zeros for both operation modes, the differential- and common-mode stopbands can be extended up to significantly high frequencies. Filter size and this differential- and common-mode stopband performance are the main relevant characteristics of the proposed balanced filters. The potential of the approach is illustrated by the design of a prototype order-5 balanced bandpass filter, with central frequency $f_{0} = 1.8$ GHz, 48% fractional bandwidth (corresponding to 55.4% −3-dB bandwidth), and 0.04-dB ripple level. The filter is automatically synthesized by means of an aggressive space-mapping software tool, specifically developed, and two (pre- and post-) optimization algorithms, necessary to determine the transmission-zero frequencies. The designed filter is as small as $0.48\lambda _{g} \times 0.51\lambda _{g}$ , where $\lambda _{g}$ is the guided wavelength at the central filter frequency, and the differential-mode stopband extends up to at least 6.5 GHz with more than 22-dB rejection. The common-mode suppression is better than 28 dB from dc up to at least 6.5 GHz.

A high-temperature superconducting filter with controllable transmission zero**Project supported by the National Natural Science Foundation of China (Grant No. 61371009) and the Chinese Ministry of Science and Technology (Grant No. 2014AA032703).

This paper presents a novel microstrip feedline structure to introduce an extra and controllable transmission zero (TZ) with high rejection for a narrowband filter. This structure loads a reconfigurable capacitor at the end of the input feedline without changing the main structure of the filter. The capacitor is recognized by a 2-bit inter-digital capacitor array. The asymmetrical microstrip feedline structure is suitable for multiple-pole filter designs. A low-loss six-pole high-temperature superconducting bandpass filter with a reconfigurable TZ is designed and fabricated. The center frequency of the filter is 5.22 GHz with TZ at the lower stopband. The TZ can be tuned among four different states. The out-of-band rejection at the TZ frequency is higher than 90 dB, and the insertion loss is lower than 0.92 dB. The measured results are consistent with the simulations.

Design of Frequency Selective Band Stop Shield Using Analytical Method

In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) shield is designed using multilayer square loop while each loop resonates at the specific desired frequency. The glass material is picked out as the preferred substrate for the designing process. In contrast to the computationally intensive numerical approaches (software), the equivalent circuit model offers a simple alternative method in FSS (frequency selective surface) analyses which is useful for quickly predicting the performance of FSS. The proposed FSS can be synthesized based on microwave filter theory and the synthesized FSS can control transmission-zero frequencies. A three zero-transmission transparent window is designed using the proposed method, in which 30dB insertion loss is achieved for 6 to 10 GHz bandwidth and optical opacity of the structure is 85%. The response of the analytical model is compared with the results of full-wave simulation. As a result, it predicts quite well the resonant frequencies of the designed FSS.

A Balanced-to-Unbalanced Microstrip Power Divider With Filtering Function

In this paper, a balanced-to-unbalanced microstrip power divider based on branch lines with several stubs and one resistor is proposed. The functions of power dividing, frequency selectivity, isolation between output ports, and common-mode suppression can be realized at the same time. The even–odd-mode equivalent circuits combining with the standard S-parameters and the mixed-mode S-parameters are adopted to derive the analytical equations at the center frequency. One or two transmission zeros can be achieved to enhance the out-of-band suppression. The center frequency, bandwidth, isolation, common-mode suppression, and the frequencies of transmission zeros can be controlled by the design procedure. To verify the theoretical prediction, two fabricated prototypes are designed and compared. One gets 7.7% 1-dB bandwidth with 0.6-dB insertion loss and one transmission zero. The other gets 1-dB bandwidth of 5% with 0.7-dB insertion loss and two transmission zeros. The isolation and common-mode suppression for both prototypes are better than 15 and 20 dB within the whole passband, respectively.

Comment on sharp‐rejection and ultra‐wide bandstop filter with five transmission zeros frequencies

In this letter, explicit transmission zero conditions, for the ultra-wide bandstop filter (BSF) with five transmission zeros, are derived using even-odd mode, analysis. The BSF topology is obtained by folding the two connecting transmission lines in a conventional optimum BSF to compose a stub-loaded coupled-line section and using λ g/2 end open-stubs. A necessary and sufficient condition is explored for the crucial coupled-line section to produce three transmission zeros. Further, it is shown that the same five zeros BSF stopband bandwidth and rejection level performance is obtained with compact three zeros BSF (without λ g/2 open-stubs) with improved passband flatness and return loss.

Synthesis of Quasi-Elliptic Bandpass Frequency-Selective Surface Using Cascaded Loop Arrays

A new quasi-elliptic bandpass frequency-selective surface (FSS) is presented by cascading a two-dimensional periodic array of double square loops (DSLs) and an array of gridded square loops (GSLs). The proposed FSS can be systematically synthesized based on microwave filter theory. The synthesized FSS can control not only the passband characteristics, but also transmission-zero frequencies at both ends of the passband, thus resulting in high selectivity and quasi-elliptic filtering response. The operating principle, detailed synthesis procedure, and implementation guidelines for this FSS are presented and discussed. As an example, a prototype of the proposed FSS is designed, fabricated, and tested. Measured results demonstrate that the proposed FSS has a simple structure, high selectivity, and stable bandpass response under a large variation of the incident angle.

VERY MINIATURE DUAL-BAND AND DUAL-MODE BANDPASS FILTER DESIGNS ON AN INTEGRATED PASSIVE DEVICE CHIP

This work presents extremely compact dual-mode and dual-band bandpass fllter designs based on dual-resonance composite resonators developed by using integrated passive device (IPD) technology on a glass substrate. A dual-mode bandpass fllter is also devised using a symmetric composite resonator with a perturbation element of grounding inductor to determine the fllter bandwidth. Additionally, a feedback capacitive coupling path on the proposed dual-mode fllter is implemented to produce three transmission-zero frequencies in the stopband. Furthermore, the proposed dual-band bandpass fllter is designed in a high-density wiring transformer conflguration with magnetic and electric mixed coupling. In addition to individually determining the fractional bandwidth of dual passbands, the magnetic and electric mixed coupling provides multiple transmission zeros to enhance the isolation between the two passbands and greatly improve the stopband rejection.

Packaged Ultra-Wide-Band Bandpass Filter Based on Inverted-T Multiple-Mode Resonators and Inverted-F Impedance Transformers [TC Contests

The packaged UWB bandpass filter based on the inverted-T multiple-mode resonator and inverted-F impedance transformer was designed, fabricated and measured. The inverted-T multiple-mode resonator was designed to have three resonance modes locating inside the passband (3.1-10.6 GHz), ensuring the flat passband insertion loss. The stepped-impedance open stubs in both inverted-T multiple-mode resonator and inverted-F impedance transformer bring numerous desired transmission zeros, helping enhance the stopband attenuation. The transmission-zero frequency is controllable by the step impedance ratio and step length ratio. The capacitive packaging effect from the Stratedge FP118118-1 is absorbed into the inverted-F impedance transformer design. The parasitic cavity modes excited in the enclosed package are suppressed by the microwave absorber attached on the lid. The integration of inverted-T multiple-mode resonator and inverted-F impedance transformer achieves a compact low-loss UWB filter with significant stopband attenuation. The packaging cases with no lid, 3.3 mm height lid, and 6.6 mm height lid were measured. The filter with 6.6 mm height lid achieves the best measured performance, which are a 4.3 dB insertion loss, 9 dB return loss over the passband of 3.1-10.6 GHz and greater than 37 dB stopband attenuation in the lower (0-2 GHz) and upper (12.515 GHz) stopbands.

Analysis and Design of a Chip Filter With Low Insertion Loss and Two Adjustable Transmission Zeros Using 0.18-$\mu{\hbox{m}}$ CMOS Technology

This paper presents the structure of a high-selectivity bandpass filter that is fabricated on low-resistivity silicon substrate with a commercial CMOS technology. The filter is constructed using crossed coplanar waveguide (CPW) lines and metal-insulator-metal capacitors to ensure that it has the desired passband characteristics. An adjustable capacitor between the input and output ports is employed to form a capacitive cross-coupled path, yielding two transmission zeros in the lower and upper stopbands, respectively. Additionally, the coupling mechanism can be modified by turning on or off the gate of an nMOS transistor to adjust the positions of the transmission zeros by applying an externally controlled voltage. To obtain a low passband loss and to minimize the chip size, high-impedance CPW transmission lines are adopted. Our analysis indicates that the CPW line possesses more advantages than the preferred stacked-ground CPW line for constructing the proposed filter. A very compact X -band experimental prototype with a size of 0.88 × 0.54 mm2 was designed and fabricated. The measurements reveal an insertion loss of less than 3.2 dB in the passband, which is from 10.6 to 12.7 GHz, and rejection levels greater than 35 dB at the designed frequencies of transmission zeros. Moreover, the lower and upper transmission zeros can be shifted from 5 to 6.5 GHz and from 18 to 21.4 GHz, respectively, by changing the controlled voltage.

Very Compact Stacked LC Resonator-Based Bandpass Filters With a Novel Approach to Tune the Transmission Zeros

This letter presents very compact stacked LC resonator structures and their coupling and excitation techniques for designing the bandpass filters operating in the 3.5 GHz WiMAX band. Using a coupled stacked LC-resonator structure not only greatly reduces the overall size but also can create multiple transmission zeros to enhance roll-off rate or desired stopband rejection for the designed bandpass filters. Furthermore, this letter develops a simple technique of etching a rectangular C-shaped slot in the bottom ground plane to flexibly adjust the transmission-zero frequencies without changing the size and shape of the filter.

Quarter-Wavelength Side-Coupled Ring Resonator for Bandpass Filters

This paper deals with a dual-mode ring resonator fed by quarter-wavelength side-coupled lines. The resonator synthesis was developed so as to fix the central frequency, bandwidth, and transmission zeros frequencies, as well as the insertion loss in the passband. Based on this resonator, several bandpass filters were designed, which include the cascaded rings and the combination of such ring resonator with coupled line sections. Simulations are proposed throughout the paper to illustrate the various possibilities offered by the concept. The filters' experimental results in microstrip technology are also presented to validate the idea.

Compact semilumped bandstop resonators using the capacitively loaded parallel‐coupled microstrip line

AbstractCompact semilumped bandstop resonators are simply designed using parallel‐coupled microstrip line and lumped capacitors. The lumped capacitors loaded in between coupled lines increase the odd mode electrical length, and the frequency of transmission zero can be controlled by the lumped capacitors. For the accurate estimation of the transmission zero frequency, the four‐port impedance parameter is derived using the even/odd mode analysis in an inhomogeneous dielectric medium. Two types of the bandstop resonators are proposed using the coupled line with the length of λg/8 (@2 GHz), and the calculated and measured results of transmission zero frequency are compared in 1–3 GHz ranges. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 367–369, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22135

Improved coupled-microstrip filter design using effective even-mode and odd-mode characteristic impedances

The transmission zeros of two coupled-microstrip circuits are studied in this research. Estimates for the frequencies of transmission zeros are given. A new concept of effective even- and odd-mode characteristic impedances is introduced. Useful design equations are given for improving the passband responses that are inherently distorted by different mode velocities. Finally, two filters with different topologies are designed for their zeros to be at the frequencies of the spurious harmonics and, thus, yield wide out-of-band rejections.

An analytical technique for the synthesis of cascaded N-tuplets cross-coupled resonators microwave filters using matrix rotations

In this paper, a general simple technique for reducing any canonical n+2 coupling matrix to the more useful modular (i.e., cascaded N-tuplets) form is presented. This is accomplished by performing a suitable sequence of matrix rotations whose angles are not derived through optimization, but are analytically computed from the starting coupling matrix elements and the transmission zeros frequencies. The proposed technique allows the association of a transmission zero to a specific block (i.e., a triplet or a quadruplet) increasing the degree of freedom in the filter design process.