Quasi-elliptic Function Response Research Articles

Electrically Coupled Folded Arm Resonators with the Feedline Patch Antenna for Spurious Harmonic Suppression and Bandwidth Improvement

This paper presents a new design of the filtering antenna with a quasi-elliptic function response. The basic structure of the proposed filtering antenna is consists of a four-folded arms open-loop resonator (OLR). The proposed filtering antenna is simulated, improved and, analyzed by using 3D Computer Simulation Technology (CST) electromagnetic simulator software. The design has good spurious harmonic suppression in the upper and lower stopbands. The Insertion Loss of the proposed filtering antenna IL=0.2 dB and the Return Loss RL= -25.788 dB at the center frequency fo=5.75 GHz. The passband bandwidth which is relatively wide, and equal to 0.793 GHz. The microstrip filtering antenna circuit shows good design results compared to the conventional microstrip patch antenna. The filtering antenna design circuit with etched ground plane structure also has good design results compared to the filtering antenna design which has a complete ground plane structure.

Ultra-Broadband Bandpass Filter Using Linearly Tapered Coupled-Microstrip Line and Open Loop Defected Ground Structure

This brief presents a novel highly compact ultrabroadband bandpass filter (BPF) using linearly tapered coupled-microstrip line (LTC-ML) and open loop defected ground structure (OL-DGS). The filter structure consists of a LTC-ML with open-circuited stubs (OCSs) and an OL-DGS etched on the ground. The linearly tapered and tightly coupled microstrip OCS can function as two resonators, and with an associated enhanced coupling structure to OL-DGS, it leads to a very compact three-pole filter. The proposed filter also exhibits a quasi-elliptic function response, where two transmission zeros (TZ) closer to each side of the passband to improve selectivity and one TZ at higher side of the upper stopband, can be observed. An approximate in-line synthesis of the proposed third-order filter with three TZs has also been performed, which shows similar characteristics like the desired response. The simulated and measured results of the filter are in good agreement with each other, showing a wide 10 dB return loss (RL) bandwidth from 4.5 to 12 GHz, insertion loss better than 1.5 dB and group delay variation of lesser than 0.2 ns in the whole passband. Furthermore, it has a very compact size of 0.31λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> × 0.55λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> at the central frequency of 8.25 GHz.

The Reentrant Four-Layer Quasi-Elliptic Bandstop Filter

The novel microwave quasi-elliptic bandstop filter, which uses the initially uncoupled strip transmission lines, is considered in this work. The proposed filter is based on the reentrant structure, where the metallic body with a floating potential is asymmetric. Generally speaking, the internal and external dielectric fillings must have their unequal relative permittivities. As a result, additional symmetrical reflection zeros are reached at the lower and upper pass bands of the stop band leading to the quasi-elliptic function response that improves the filter selectivity. The general transverse electromagnetic (TEM) circuit model for the proposed filter in terms of a series connection of the multi-ports is presented and then used to predict the initial electrical and geometrical parameters. An experimental printed circuit prototype has been manufactured and evaluated to validate the design concept. The measured filter parameters correlate well with the simulation-derived ones and that increases the degree of freedom in the fabrication of microwave frequency selective components.

Parallel-coupled linear-phase superconducting filter

A novel double coupling planar structure (a single microstrip line coupled with two resonators coincidental) is presented for the first time. Based on this structure, a six-pole parallel-coupled high-temperature superconducting band-pass filter with both linear phase response and quasi-elliptic function response is designed. The filter has a 40 MHz passband with a center frequency of 2,000 MHz. Its dimension is 18.67 mm × 25.96 mm. At 77 K, minimum insertion loss is 0.26 dB in passband. The group delay variation is <3 ns over 70 % of the filter bandwidth.

Compact Varactor-Tuned Microstrip High-Pass Filter With a Quasi-Elliptic Function Response

This paper presents a novel circuit topology of a tunable high-pass filter with a quasi-elliptic function response. A detailed theoretical analysis for the performance operating mechanism is demonstrated. With the assistance of mutually inductive coupling introduced, a pair of tunable transmission zeros (TZs) is synthesized at the lower passband edges and significantly improves the filter selectivity. Experiments are carried out by using the liquid crystal polymer bonded multilayer printed circuit board technology to validate the design. It is found that the implemented filter achieves a wide continuous tuning range covering from 1030 to 2150 MHz with low insertion loss, and which indeed are limited by the Schottky diodes used. It is also illustrated that two measured TZs are properly controlled at each tuning stage, which not only offers a sharp cutoff frequency response with a rejection level greater than 22 dB, but also provides an approximately unchanged response shape. Good agreement between the measured and simulated results can finally be observed.

ULTRA-WIDEBAND MULTI-STUB LOADED RING RESONATOR BANDPASS FILTER WITH A NOTCHED-BAND

In this paper, a novel compact ultra-wideband (UWB) microstrip bandpass fllter (BPF) with a notched band using the proposed multi-stub loaded ring resonator (MSLRR) is presented. The MSLRR is constructed by loading four open stubs in a ring resonator, i.e., one pair of high-impedance stub at the top side and another two low-impedance stubs at the bottom side locations. Five modes, including two odd modes and three even modes, could be designed within UWB band. Moreover, two transmission zeros (TZs) are generated by the ring structure, leading to a quasi-elliptic function response that enhances the selectivity signiflcantly. Two slotline split- ring resonators (SRR) are used to create a narrow notched band at 8.6GHz. The simulated and measured results are in good agreement and show good in-band flltering performance and sharp selectivity.

Compact Quasi-Elliptic Wideband Bandpass Filter Using Cross-Coupled Multiple-Mode Resonator

A novel compact wideband bandpass filter (BPF) is proposed based on cross-coupled multiple-mode resonator (MMR). The proposed resonator is constructed by introducing cross coupling between the high-impedance lines of a classical MMR. It is shown that new symmetrical pairs of transmission zeros (TZs) can be generated at the lower and upper stopbands, respectively, leading to a quasi-elliptic function response that enhances the selectivity and out-of-band rejection significantly. One filter prototype is designed, fabricated and measured for validation and shows the expected performance.

Highly selective ultra wideband bandpass filters with quasi-elliptic function response

This study presents a new type of compact highly selective ultra wideband (UWB) bandpass filter (BPF) that exhibits a quasi-elliptic function response. By using the quasi-lumped element concept, a broadside coupled resonator is designed to implement a transmission zero at lower stopband, and some shunt resonators are adopted to generate transmission zeros at the upper stopband. Hence, very selective performance with a quasi-elliptic function response is achieved. Two UWB filters are designed for the demonstration. The first filter is designed with a passband from 3.1 to 10.6 GHz for the Federal Communications Commission (FCC)-defined indoor limit application, and the second filter is designed with an even wider passband from 3.0 to 16.2 GHz, showing the flexible wide passband performance of the proposed filters. Experiments are carried out to validate the designs. A low cost multilayer liquid crystal polymer technology is deployed to implement the proposed filters. Small sizes for fabricated filters are achieved, which are 8.8 mm×9.0 mm×0.5 mm and 6.4 mm×5.9 mm×0.2 mm, respectively. All the measured filters have excellent performance, including low insertion losses, flat group delay and high selectivity. The proposed new type of UWB BPF is favourable for practical UWB communication and radar systems.

QUASI-ELLIPTIC FUNCTION BANDPASS FILTER WITH UPPER STOPBAND EXTENSION AND HIGH REJECTION LEVEL USING CROSS-COUPLED STEPPED-IMPEDANCE RESONATORS

Planar microstrip fllters are designed to have a quasi- elliptic function passband and extended upper stopband with a rejection level of 40 or 50dB. The design employs stepped-impedance resonators in a compact 2 £ 2 cross coupled conflguration. The geometric parameters of the resonators are planned to shift the third resonance as high as possible, and then the transmission zeros created by the structure are devised to suppress the second resonance, so that a wide upper stopband up to more than 4.5 times the passband frequency can be achieved. By employing the skew-symmetric input/output feeds, three transmission zeros in the frequency band of interest can be created. The leading two zeros are allocated on the both sides of the passband, generating a quasi-elliptic function response with enhanced roll-ofi rate in the transition bands, and the last zero incorporating with a zero created by anti-coupled-line at higher frequencies are employed to extend the rejection bandwidth. The measurement data agree very well with the simulation responses.

Design of compact triple‐mode bandpass filter using double center stubs‐loaded resonator

AbstractA compact microstrip triple‐mode bandpass filter using half‐wavelength (λ/2) open‐ended microstrip line with double center loaded stubs is proposed in this article.By introducing a radial‐line stub to the traditional dual‐mode resonator, a triple‐mode resonator is realized and the mode characteristics of the resonator are discussed. Also, an equivalent lumped circuit is proposed and the method of parameters extracting is given. The proposed filter exhibits a quasi‐elliptic function response with a compact circuit dimension. At last, an experimental filter is fabricated and a good agreement between simulations and measurements is reached. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2109–2111, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25364

A high-performance narrowband high temperature superconducting filter

Recent development of a high-performance narrowband high-temperature superconducting (HTS) filter is presented. A 10-pole quasi-elliptic function response filter with two pairs of transmission zeros (for high selectivity), which has a center frequency of 2.185 GHz and a 3 dB bandwidth of 10 MHz (a fractional bandwidth of 0.45%), is introduced. The filter was fabricated on a 40 mm×16 mm×0.5 mm MgO wafer with double-sided YBCO films. The measured results show that the filter has 0.15 dB insertion loss at the center of the passband and a return loss better than −22.5 dB at a temperature of 67 K. Band edge steepness reaches over 28.3 dB/MHz at both the low and high frequency edges. The out-of-band rejection is over 78 dB at 8 MHz away from the center frequency and close to 100 dB in a wideband range.

Neural Model for Left-Handed CPW Bandpass Filter Loaded Split Ring Resonator

Compact left-handed coplanar waveguide (CPW) bandpass filter loaded split ring resonator (SRR) is presented in this paper. The proposed filter exhibits a quasi-elliptic function response and its circuit size occupies only 12 × 11.8 mm2 (≈0.21 λg × 0.20 λg). Also, a simple circuit model is given and the parametric study of this filter is discussed. Then, with the aid of NeuroModeler software, a five-layer feed-forward perceptron neural networks model is built up to optimize the proposed filter design fast and accurately. Finally, this newly left-handed CPW bandpass filter was fabricated and measured. A good agreement between simulations and measurement verifies the proposed left-handed filter and the validity of design methodology.

8-GHz Narrowband High-Temperature Superconducting Filter With High Selectivity and Flat Group Delay

This paper reports a development of a narrowband high-temperature superconducting filter with both high selectivity and flat group delay. The filter has a center frequency of 8.625 GHz and a 3-dB bandwidth of 42 MHz (a fractional bandwidth of 0.49%). In order to achieve both high band-edge steepness and excellent group-delay flatness, we introduce a 14-resonator quasi-elliptic function response with three pairs of transmission zeros (one pair for high selectivity and two pairs for flat group delay) in the cascaded quadruplet coupling structure. We also develop a novel low radiation resonator (double-folded resonator) to reduce the parasitic coupling and meet other requirements for the 8-GHz filter. The filter was fabricated on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBCO films. The measured results show a midband insertion loss of 1.6 dB and a return loss better than 15.5 dB. Band-edge steepness reaches over 11.7 dB/MHz at both the high- and low-frequency edges. The 60-dB rectangle ratio is less than 1.25. The out-of-band rejection is over 70 dB at 5.98 MHz from the 3-dB band edge. The variation of group delay is less than 23 ns over 33 MHz (78.5% of 3-dB bandwidth), and less than 30 ns over 34.5 MHz (82% of 3-dB bandwidth).

Superconducting Narrowband Filter for Receiver of Weather Radar

We have developed a high-temperature superconducting (HTS) filter with narrow bandwidth characteristic for receiver of weather radar in order to reduce interference between adjacent radar channels. To realize a filter with which a narrow bandwidth and low insertion loss are compatible, resonators with high unloaded Q (Qu) value are required. Hairpin microstrip resonators with 1.5 times wavelength were adopted to suppress the radiation loss and achieve a high Qu value. The developed HTS filter has 8-pole quasi-elliptic function response for sharp skirt characteristic. The measured frequency response of the developed filter shows center frequency of 5370MHz, insertion loss of 2.04dB and maximum return loss of 15dB, which agrees with the designed responses.

Input and Output Cross-Coupled Wideband Bandpass Filter

A new wideband bandpass filter configuration with input-output cross-coupling is investigated. The new filter is based on a transmission line filter with short-circuited stubs. In order to allow the filter to exhibit high selectivity filtering characteristic and to enhance the group delay with only a few resonators, cross-coupling between the input and output feed lines is introduced. As a result, new symmetrical pairs of transmission zeros are generated at the lower and upper stopbands, leading to a quasi-elliptic function response that improves the passband and out-of-band performances. A general circuit model for the proposed filter is presented and a demonstrator with approximately 48% ripple bandwidth at a midband frequency of 3 GHz is developed. The design is successfully realized in theory and verified by full-wave electromagnetic simulation and the experiment, where excellent agreement is obtained.

Wideband Bandstop Filter With Cross-Coupling

A general circuit configuration for cross-coupled wideband bandstop filters is proposed. The distinct filtering characteristics of this new type of transmission line filter are investigated theoretically and experimentally. It is shown that a ripple stopband can be created, leading to a quasi-elliptic function response that enhances the rejection bandwidth. A demonstrator with approximately 80% fractional bandwidth at a mid-stopband frequency of 4 GHz is developed and presented. The proposed filter is successfully realized in theory and verified by full-wave electromagnetic simulation and the experiment. Theoretical, simulated, and measured results are in excellent agreement.

Compact Ultra-Wideband Microstrip/Coplanar Waveguide Bandpass Filter

A novel ultra wideband (UWB) bandpass filter is presented, using a compact coupled microstrip/coplanar waveguide (CPW) structure. The filter comprises of a single CPW quarter-wavelength resonator which is coupled to two microstrip open-circuited stubs on the other side of a common substrate. The two microstrip open-circuited stubs, which are about a quarter-wavelength long at the center frequency, can function as two resonators with associated coupling arrangement to the CPW. This forms a very compact three-pole filter. The proposed filter also exhibits a quasi-elliptic function response, with one finite-frequency transmission zero closer to each side of the passband. Thus, a high selectivity is achieved using a small number of resonators, which leads to low insertion loss and group delay across the passband. The performance is predicated using EM simulations and verified experimentally. The experimental filter shows a fractional bandwidth of 90% at a center frequency of 6.4GHz, with two observable transmission zeros (attenuation poles) at 1.95 and 10.36GHz, respectively. Furthermore, it has a very small size only amounting to 0.25 by 0.08 guided wavelength at the center frequency

Design of Dual-Band Bandpass Filter with Quasi-Elliptic Function Response for WLANs

Design of Dual-Band Bandpass Filter with Quasi-Elliptic Function Response for WLANs

Eighteen-pole superconducting CQ filter for future wireless applications

A recent development of an eighteen-pole high-temperature-superconducting (HTS) bandpass filter with group delay self-equalisation for future wireless applications is reported. The filter is designed to have a 15 MHz pass-band at a centre frequency of 1967.5 MHz. The filter exhibits a quasi-elliptic function response implemented with a cascaded quadruplet (CQ) coupling structure. Two particular cross-coupled quadruplet realisations have been developed to implement either attenuation poles at finite frequencies or linear phase for group delay self-equalisation. The Monte-Carlo sensitivity analysis was performed and the results were used as guidelines for tuning the filter. The filter was fabricated on a 0.43 mm-thick sapphire wafer with double-sided YBCO films. Measured responses are presented to demonstrate the validity of the design as well as the potential of the filter.

Narrowband high temperature superconducting filter for mobile communication systems

The paper reports a recent development of a narrowband high temperature superconducting (HTS) bandpass filter for future mobile communication systems. The filter is designed to have a 5 MHz passband in the UMTS base station's receive band. The filter exhibits an 8-pole quasi-elliptic function response implemented with a cascaded quadruplet coupling structure. The filter was fabricated on a 0.43 mm-thick sapphire wafer with double-sided YBCO films. The measured filter showed a midband insertion loss of 0.5 dB at 1973 MHz and a return loss better than � 15 dB over the passband. It also exhibited an excellent rejection over the entire UMTS base station transmission band.