Asymmetric Stepped-impedance Resonators Research Articles

Design of a high band-isolation diplexer based on asymmetric stepped-impedance resonators with side-coupling structure

In this paper, a high band-isolation diplexer based on two bandpass filters (BPFs) formed using asymmetric stepped-impedance resonators is presented. The passbands of the diplexer are operated at 1.8 GHz for global system for mobile communications (GSM) and 2.4 GHz for wireless local area network (WLAN). Side-coupling structure is adopted in BPFs to create two additional transmission zeros, thus enhancing the band isolation and stopband region. The measured results of the proposed diplexer show the passband at 1.8 GHz with a low insertion loss of 1.09 dB, a 3 dB fractional bandwidth (FBW) of 9.4% in the first channel and a passband at 2.4 GHz with an insertion loss of 2.6 dB, a 3 dB FBW of 6.2% in the second channel. The measured results of the fabricated diplexer also show a good agreement with the simulated ones.

A NEW TRI-BAND BANDPASS FILTER FOR GSM, WIMAX AND ULTRA-WIDEBAND RESPONSES BY USING ASYMMETRIC STEPPED IMPEDANCE RESONATORS

In this paper, a design of new tri-band bandpass fllter for the application of GSM (1.8GHz), WiMAX (2.7GHz) and UWB (3.3{ 4.8GHz) is proposed. The flrst two narrow passbands are created, and the bandwidth of the third passband can be tuned by properly selecting the impedance ratio (R) and physical length ratio (u) of the asymmetric stepped-impedance resonator. To improve passband performance and form the UWB passband, a U-shape defected ground structure and extra extended coupling lines are integrated with the asymmetric SIR. Due to the three transmission zeros appearing near the passband edges, the band selectivity of the proposed fllter is much improved. The fllter was fabricated, and the measured results have a good agreement with the full-wave simulated ones.

Independently Controllable Dual-Band Bandpass Filters Using Asymmetric Stepped-Impedance Resonators

This paper presents a dual-band bandpass filter with independent switchability of each passband. By taking advantage of harmonic ratio of asymmetric stepped-impedance resonators, 2.4- and 5.2-GHz resonators are designed. The second resonance of 2.4-GHz resonators is designed to be suppressed by a transmission zero created by extended feed lines. To achieve a wide upper stopband, 5.2-GHz resonators are designed with a scheme that the second peak of these resonators would not appear at a frequency lower than a third peak of 2.4-GHz resonators. Several design graphs for deciding both geometric parameters and transmission zeros are plotted by using the information obtained from electromagnetic simulations. While extracting coupling coefficients between resonators, an external quality factor at 50-Ω port is fixed to determine the precise transmission zeros. Two kinds of feed lines, such as a hook type and a spiral type, are developed, and spiral-type feed lines are chosen for realizing switchable filters. By controlling p-i-n diodes, four states of switchable dual bands are clearly presented in simulations and experiments.

Simple method to design a tri‐band bandpass filter using asymmetric SIRs for GSM, WIMAX, and WLAN applications

AbstractThis paper presents a simple method to design a tri‐band bandpass filter (BPF) using asymmetric stepped‐impedance resonators (SIRs) with one‐step discontinuity.Only two SIRs are needed in the filter structure. The tri‐band passband responses can be achieved by properly selecting the length ratio (u) and the impedance ratio (R) of the asymmetric SIRs. The performances can be further well tuned by the lengths of two enhanced coupling structure and gap of two asymmetric SIRs. A filter example for the applications of GSM at 1.8 GHz, WiMAX at 3.5 GHz and WLAN at 5.2 GHz was designed and fabricated. The measured results are in good agreement with the full‐wave simulation results. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26037

A New Quad-Band Bandpass Filter Using Asymmetric Stepped Impedance Resonators

A new quad-band microstrip bandpass filter (BPF) using asymmetric stepped impedance resonators (SIRs) is proposed. The filter only employs two sets of the asymmetric SIRs. One set is designed to operate at the first and third passbands (2.4/5.2 GHz) and the other set is employed at second and fourth passbands (3.5/6.8 GHz). By tuning the impedance and length ratios of the asymmetric SIRs, a multi-band filter can be easily achieved. This study provides a simple and effective method to design a quad-band filter with low insertion loss and compact size. Experimental verification is provided and good agreement has been found between simulation and measurement.

Compact dual-passband microstrip bandpass filters with larger design flexibility and multi-spurious suppression

Compact folded stepped impedance resonators (SIRs) with a novel asymmetric structure are used to design dual-passband filters with multi-spurious suppression. A complete design procedure enhancing both overall design flexibility and suppressing spurious responses is detailed. The new asymmetric SIR structure can effectively increase the degree of freedom (DOF) in the dual-passband bandwidth design. Extra DOF is simultaneously incorporated so that transmission zeros of the coupling stages may be adjusted to suppress unwanted spurious responses. Owing to circuit symmetry and a short coupling length, the circuit can be easily folded and the size is decreased by 62% compared with the previous work. The measured results agree well with the simulation and show that the attenuation level of the upper stopband is greater than 30%dB up to more than 20%GHz (8.16 f 0 ).

Design of Dual-Passband Microstrip Bandpass Filters With Multi-Spurious Suppression

A systematic design method for microstrip bandpass filters with both dual-passband response and multi-spurious suppression is proposed in this letter. The filter is composed of stepped impedance resonators (SIRs). A novel asymmetric SIR structure is proposed to effectively increase the degree of freedom in the dual-passband bandwidth design. As a consequence, the transmission zero of the coupling stage could be used to suppress the unwanted higher order spurious responses. A complete design procedure considering both the synthesis of passband responses and the suppression of spurious responses is also depicted in detail. A fifth order filter is designed and fabricated to demonstrate this idea. The measured results show that the upper stopband can have an attenuation level near 30 dB up to more than 20 GHz (8.16 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ).

A Compact Dual-Band Bandpass Filter with High Band Selectivity using Cross-Coupled Asymmetric Sirs for Wlans

In this paper, we have proposed the design of novel compact dual-band bandpass filter (BPF) with high band selectivity by using only two asymmetric stepped impedance resonators (SIRs) with one step discontinuity. By arranging the cross-coupled SIRs, three transmission zeros near the passband edges and a high isolation between two passbands are introduced to improve the band selectivity of the proposed filter. The dual-band frequencies of this BPF is implemented by properly selecting the impedance ratio (R) and physical length ratio of the asymmetric SIRs. The bandwidths and the coupling coefficients of the two passbands (2.4/5.2 GHz) can be designed by adjusting the coupling gap between the resonators. The proposed BPF has a smaller circuit size in comparison with previous works using conventional direct-coupling SIRs. The measured results are in good agreement with the full-wave simulation ones.

Design of a Triple-Passband Microstrip Bandpass Filter with Compact Size

This paper presents the triplepassband microstrip bandpass filter (BPF) with compact size. Two sets of the coupled asymmetric stepped impedance resonators (SIRs) and uniform impedance resonators (UIRs) are arranged for generating the triple-passband properties. It is convenient to control the triple-passband properties by tuning the impedance ratio (K) and length ratio (γ) of the asymmetric SIRs. The UIRs are also employed to enhance the coupling between the coupled resonators at 3rd passband. The filter is designed at 2.4/5.2/8.2 GHz and achieves nearly 50% circuit size reduction compared with the previous works. This study provides a simple method to design a triple-passband filter with compact circuit size. Experimental verification is provided, and good agreement has been found between simulation and measurement.

Design of the Compact Dual-Band Bandpass Filter With High Isolation for GPS/WLAN Applications

In this letter, a novel compact dual-band bandpass filter (BPF) is designed to achieve the characteristic of low insertion loss and high isolation for global position system (GPS)/wireless local area network (WLAN) applications. This BPF is implemented by properly selecting the impedance ratio (R) and physical length ratio (alpha) of the asymmetric stepped-impedance resonator (SIR) with one step discontinuity. The coupling coefficient between the coupled asymmetric SIRs is calculated by using full-wave simulator IE3D. The proposed filter has very good measured characteristics including a low insertion loss of 1.1 dB for both passbands, a high isolation insertion loss of 55 dB between the two passbands and a wide stopband rejection of 38 dB from 2.7 to 5.3 GHz. Good agreement with responses of electromagnetic (EM) simulation and measurement is compared.

Design of dual‐band SIR bandpass filter with a broad upper rejection band for WLANs

AbstractIn this letter, we proposed the design of novel dual‐band bandpass filter (BPF) with a broad upper rejection band using only two asymmetric stepped impedance resonators (SIRs), which has a smaller circuit size in comparison of previous works. The feature of the asymmetric SIR is only one‐step discontinuity, which is different from the conventional SIR with two‐step discontinuities. By selecting properly the impedance ratio (R) and physical length ratio (α) of the proposed asymmetric SIRs, the low loss dual‐band BPF centered at 2.4/5.2 GHz with a wide upper rejection band from 6 to 14 GHz can be implemented perfectly. The bandwidths and the coupling coefficients of the two passbands can be tunable by adjusting the coupling gap distance between the resonators, which are calculated by using full‐wave simulator IE3D. Good agreement between the electromagnetic (EM) simulation and measurement is reported. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1143–1146, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24227

High-selectivity dual-band bandpass filter using asymmetric stepped-impedance resonators

A dual-band bandpass filter with high selectivity is presented. Using only a single set of asymmetric stepped-impedance resonators, this filter can create five transmission zeros near the passband edges and between the two passbands to improve the selectivity. Based on the proposed idea, a microstrip dual-band bandpass filter is implemented.

Design of the Compact Wideband Bandpass Filter With Low Loss, High Selectivity and Wide Stopband

In this letter, a novel compact wideband bandpass filter using the asymmetric stepped-impedance resonator (SIR) with one step discontinuity is designed and implemented to achieve characteristics of low loss, wide stopband and very high passband selectivity, simultaneously. The first two resonant modes of the asymmetric SIR are coupled together and applied to create a wide passband. The design procedure is discussed in detail. The proposed filter at center frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> of 4 GHz has very good measured characteristics including a low insertion loss of 0.5 plusmn 0.3 dB, the bandwidth of 2.9-5.3 GHz, sharp rejection due to two transmission zeros in the passband edge. Experimental results of the fabricated filter show a good agreement with the predict results.

A novel compact dual‐band bandpass filter using asymmetric SIRs for WLANS

AbstractIn this article, a novel compact dual‐band bandpass filter (BPF) using asymmetric stepped impedance resonators (SIRs) has been presented for the first time. The feature of the proposed asymmetric SIR is only one step discontinuity, which is different from the conventional SIR with two step discontinuities. The frequency response of the dual‐band at 2.4/5.2 GHz can be achieved by determining the impedance ratio (K) and physical length ratio (α) of the asymmetric SIR. The coupling coefficient between the coupled asymmetric SIRs is calculated by using full‐wave simulator IE3D. A dual band BPF is designed, fabricated, and measured. The measured results are in good agreement with the full‐wave simulation results. Additionally, the BPF has a smaller circuit size in comparison of previous works. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1237–1240, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23339

Compact Microstrip Lowpass Filter Using Asymmetric Stepped-Impedance Hairpin Resonator and Slotted Ground Plane

In this paper, a newly compact low pass filter is introduced. This filter is constructed by using novel asymmetric stepped-impedance hairpin resonator and slotted ground plan for size reduction and spurious suppression. Furthermore, the equivalent circuit model of the proposed resonator is set up and analyzed. Additionally, slotted ground plane are adopted to obtain a good stop band characteristics. Finally, this compact filter was designed, fabricated, and measured. The experimental results of the filter have a good agreement with the simulated results.

Stepped-Impedance Hairpin Resonators with Asymmetric Capacitively Loaded Coupled Lines for Improved Stopband Characteristics

New microstrip bandpass filters with extended stopband bandwidths are proposed by using new asymmetric stepped-impedance hairpin resonators (ASIHRs). The size of the proposed resonators has been reduced around 16%, comparing with the conventional stepped-impedance hairpin resonators (SIHRs) structure. The first bandpass filter is a combination of differ resonators with the same fundamental frequency but differ in harmonic frequencies, resulting in improved suppression spurious responses in stopbands. Furthermore, another bandpass filter uses the ASIHRs periodically loaded on a microstrip line to improve stopband characteristics. The proposed filters not only have compact size of resonators, but also provide improved upper stopband characteristics. The proposed filters provide 20 dB rejection levels in the stopband up to 6f 0 . The measured filters responses agree very well with the simulated expectations.

Design of a New Bandpass Filter Using Anti-Parallel Coupled Asymmetric SIRs

In this paper a newly designed internally-coupled asymmetric stepped-impedance resonator (SIR) bandpass filter (BPF) is proposed. The asymmetric SIR structure not only can effectively reduce the circuit size but also can provide two flexibly tunable transmission zeros near the lower and upper passband edges. The first transmission zero is due to the series resonance of the quarter-wavelength open stepped-impedance stub, and the second one is produced by anti-parallel coupling between adjacent SIRs. The proposed BPF was fabricated and simulated using the commercial software HFSS, and agreement between the measured and simulated results was observed. A 0.9-dB insertion loss and a shape factor of 3.6 were achieved in the passband, thus indicating that the proposed filter structure is of practical value.