Quarter-wavelength Stepped-impedance Resonators Research Articles

Design of a Compact Enhanced Stopband Bandpass Filter with Embedded Coupled Stubs

A compact bandpass filter with an enhanced stopband using stepped-impedance resonators is presented in this article. The proposed filter consists of two quarter-wavelength stepped-impedance resonators with a circular structure for compact size. To improve the upper stopband of the proposed filter, embedded coupled stubs are employed. Owing to the mixed electric/magnetic coupling and the embedded coupled stubs, four transmission zeros can be generated in the stopband for improved selectivity and a wider upper stopband. A new bandpass filter centered at f0 (1.38 GHz) has been designed and fabricated to demonstrate the validity of the proposed method. Measured results show that four finite transmission zeros are located at 0.91, 3.01, 4.90, and 7.20 GHz. The spurious frequencies of the upper stopband are suppressed better than 30 dB up to 6.10 f0. The circuit size of proposed filter only occupies 0.09λg × 0.09λg.

Dual‐band bandpass filter with wide upper stopband using quad‐mode stepped impedance stub‐loaded resonator

A novel quad-mode stepped impedance stub-loaded resonator is presented. The even–odd-mode method is applied twice to analyse the modal resonance characteristics due to its symmetry. All the four modes' equivalent circuits are quarter-wavelength stepped impedance resonators, so the proposed resonator has a compact size and higher harmonic frequencies. Stub-to-stub coupling is introduced to split two identical modes and produce two transmission zeros. A dual-band bandpass filter operating at 1.5 and 2.4 GHz is designed using the proposed resonator. The centre frequency and bandwidth of each passband can be controlled by tuning the corresponding physical dimensions, and a wide upper stopband is achieved. Finally, the designed filter was fabricated and measured, and the measured results have good agreement with the simulated ones.

Switchable and High-Isolation Diplexer With Wide Stopband

This letter presents a switchable diplexer composed of a stepped-impedance distributed coupling feeding line, four different quarter-wavelength stepped-impedance resonators (SIRs), two shunt open stubs, two p-i-n diodes, and bias circuitry. Compared with previous works, the proposed circuit features compactness, wide stopband, high selectivity, and independently switchable channels. To suppress harmonics, various quarter-wavelength SIRs with the same fundamental frequency but harmonic frequencies in stagger are used. Open stubs are also adopted to achieve an optimal stopband response. To meet the demands of reconfigurable application in wireless communication systems, switching circuit is integrated into the proposed diplexer to develop a switchable diplexer. In this way, mismatch losses during integration and circuit size are both further reduced. Simulations and measurements have been carried out to verify the design concept with good agreement.

Quarter-Wavelength Stepped-Impedance Resonator Filter With Mixed Electric and Magnetic Coupling

This letter proposes a new type of microstrip quarter-wavelength stepped-impedance resonator (SIR) filter with controllable mixed electric and magnetic coupling. A conducting pin and an open gap between two coupled SIRs are jointly used to create the mixed coupling, and the electric and magnetic coupling can be separately controlled by adjusting the spacing between the gap and the position of the conducting pin. Based on the proposed structure, a second-order filter and a third-order filter are designed and fabricated. Good agreement between the measured and simulated data is obtained.

DESIGN OF A MINIATURIZED DUAL-BAND BANDPASS FILTER WITH HIGH SELECTIVITY

In this paper, a miniaturized dual-band bandpass fllter with high selectivity and band-to- band isolation is presented. The fllter consists of two quarter-wavelength stepped impedance resonators (SIRs) which share a common grounded via-hole and two symmetrical half-wavelength SIRs which are embedded into the inner space to reduce the size of the fllter. Two independent mixed coupling paths which are created by the coupling between these SIRs introduce two difierent passbands. Five transmission zeros (TZs) are generated near the two passbands to achieve high frequency selectivity and band-to-band isolation. To validate the design theory, a dual-band fllter operating at 2.45 and 5.2GHz was designed and fabricated. The size of the proposed fllter only occupies 0:095‚g £ 0:109‚g and the measured 3dB fractional bandwidth (FBW) of the flrst and second passbands is 11.5% and 7.4% respectively. The measured results are in good agreement with the simulated results.

Design of Microstrip Quasi-Elliptic Bandpass Filter with Upper Wide Stopband Using Quarter-Wavelength Stepped-Impedance Resonators

In this article, a miniaturized quasi-elliptic bandpass filter using four quarter-wavelength (λ/4) stepped-impedance resonators is presented. With a simple design method, the presence of spurious harmonics can be avoided without using an extra filter or stub elements. The λ/4 stepped-impedance resonators in the structure of the filter resulted in a wide stopband and reduced circuit size. The combination of resonators with the same fundamental frequency but different spurious frequencies improved the stopband bandwidth. The proposed filter has the center frequency at 2.02 GHz and a 3-dB fractional bandwidth of 17.5%. On the other hand, the proposed filter shows wide upper stopband with attenuation level better than −22.2 dB up to 13.86fo, where fo is the passband center frequency. The circuit has a simple structure and a compact size. The designed bandpass filter has been simulated, fabricated, and measured, and there is good agreement between the measured and simulated results.

Design of a wide-stopband bandpass filter using stepped impedance resonators

In this paper, a compact bandpass filter (BPF) with improved stopband characteristics using stepped impedance resonators (SIRs) is proposed. The filter consists of two quarter-wavelength SIRs with radial stubs and a PI-network of capacitance, which is used to suppress the upper frequency spurious signals. An odd- and even-mode analysis is adopted considering the structure’s symmetry. A new BPF centered at 1.57 GHz has been designed and fabricated to verify the validity of the proposed method. Measured results are in good agreement with the electromagnetic simulation. The frequency selectivity was enhanced via introducing two finite transmission zeros (TZs) near the passband, located at 1.21 GHz with 43.5 dB rejection and 3.10 GHz with 62.3 dB rejection, respectively. The spurious frequencies of the upper stopband are suppressed better than 20 dB from 2.07 to 16.25 GHz. And the circuit only occupies 0.09 λg × 0.09 λg.

Compact and switchable dual‐band bandpass filter with high selectivity and wide stopband

A compact and independently switchable dual-band bandpass filter is presented. To achieve high selectivity response, transmission zeros beside the two passbands are generated due to crossed coupling. On the other hand, the use of quarter-wavelength stepped-impedance resonators can not only miniaturise circuit size but also widen the stopband by arranging the resonant frequencies in a stagger with the same fundamental frequency. The pin diodes are loaded at the end of the resonators as the switching devices to independently control each passband.

A six-pole narrow-band high temperature superconducting filter with wide stop-band response at P-band

A quarter-wavelength stepped impedance resonator (QWSIR) is proposed for high temperature superconducting (HTS) filter, offering wide stop-band performance. A six-pole P-band HTS filter with QWSIRs was designed and fabricated. The filter has a fractional bandwidth of 0.8% at 516MHz and shows the lowest spurious frequency at about 2.15GHz. The measured results of the HTS filter are in good agreement with simulations.

Microstrip Dual-Band Bandpass Filter Design With Closely Specified Passbands

An efficient and practical design method for a dual-band bandpass filter (BPF) is presented. The electrical specifications of the filter, such as the center frequency, bandwidth, and transmission zero location, are controllable and adjustable. Once, the desired ratio of the resonant frequency of the two bands is given, the characteristic impedance of the line corresponding to the specific ratio can be accurately determined from the design curve. Compared with the conventional half- and quarter-wavelength stepped-impedance resonators (SIRs), the proposed unequal-length shunted-line stepped- impedance resonator (shunted-line SIR) can provide an efficient way to realize the dual-band filter, especially when two passbands are closely spaced. Furthermore, the multitransmission zeros and one controllable transmission zero are generated near the passbands to improve the out-of-band rejection. The design examples of microstrip dual-band BPFs operating at 2.2/3.45 and 1.95/2.65 GHz with equal absolute bandwidths and high isolation are demonstrated to validate of the design method. In the illustrated cases, a small frequency ratio of 1.3 between two resonant frequencies can be achieved. The proposed design method is very useful for the dual-band BPF design, especially when the two passbands are very close.

Tri‐band filter using combined E‐type resonators

A compact microstrip tri-band bandpass filter using novel combined E-type resonators (CETRs) is presented. The CETR consists of a quarter-wavelength (λ/4) stepped-impedance resonator (SIR) and a quarter-wavelength (λ/4) unit impedance resonator through a via-hole. These two components are relatively independent. The first and the third passband centre frequencies can be flexibly controlled by tuning the impedance ratio RZ of the SIR, whereas the second passband frequency is fixed. The centre frequency of the second passband can be independently controlled by tuning the lengths of L2. The filter is designed to operate at 1.95, 5.2, and 3.5 GHz. The simulated and measured results show good agreement.

Design of tri-band microstrip BPF using SLR and quarter-wavelength SIR

A tri-band microstrip bandpass filter (BPF) with compact size and high selectivity is presented by using the stub-loaded resonator (SLR) and quarter-wavelength stepped-impedance resonator (SIR). The quarter-wavelength SIR is designed for the first and third passband and the SLR mainly controls second passband performance, so three passband frequencies can be flexibly tuned. Because of the intrinsic characteristics of the resonators and source-load coupling, multiple transmission zeros can be created to improve the selectivity. Finally, a tri-band BPF prototype located at 0.98 GHz (FRID application), 3.6 GHz (Wimax application), and 5.8 GHz (WLAN application) is designed. Measurement results agree well with the full-wave EM simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:212–215, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27247

Compact interlocked-coupled filter using folded stepped-impedance resonators

A microstrip interlocked-coupled bandpass filter is proposed with a markedly compact structure. The low-impedance open-end line of the quarter-wavelength Stepped-Impedance Resonator (SIR) is replaced by two open-end high-impedance lines, which not only facilitate the coupling mechanism but also provide the strong electric coupling between resonators. With the proper utilization of folded SIRs, the occupied area of coupled-resonator pair can be reduced. By applying the proposed coupled-resonator pair, the passband filter with the compact size can be realized. Good agreement between measured and simulated results is observed. The proposed filter is desirable for compact and high-performance microwave circuit applications.

Design of compact microstrip band-pass filter with ultra-wide stopband

In this article, a microstrip band-pass filter with compact structure and ultra-wide stopband using quarter-wavelength stepped impedance resonators is proposed.Because of the optimal design for stepped impedance resonators, circuit size is reduced and harmonic response is suppressed. To suppress the higher resonant modes further, two open stubs connected to the input/output ports are used to achieve an ultra-wide stopband. The design procedure and additional lateral-resonated response are discussed in detail. As the presence of the two attenuation poles are around the passband edge, high selectivity and good performance is realized. The proposed filter with a fundamental frequency f0 of 0.9 GHz, measured insertion loss of less than 1.5 dB, return loss of better than 16 dB, and wide stopband up to 19 f0 is demonstrated. The stopband level is lower than 23 dB from 1.1 GHz up to 17.1 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1603–1606, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25238

Quarter-Wavelength Stepped-Impedance YBCO Resonators for Miniaturized Dual-Band High-Tc Superconducting Filters

A dual-band high-temperature superconducting (HTS) bandpass filter (BPF) is proposed for wireless local area network applications. Using quarter-wavelength stepped-impedance resonators, the designed filter can be miniaturized and shows a dual-band response. The simulation results show the dual-band feature of two passbands at 2.4 and 5.2 GHz, each with a minimum in-band insertion loss of about 0.02 dB. The filter was made out of patterned double-sided deposited YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (YBCO) films integrated with a gold-coated housing. The realized HTS BPF shows two passbands at 2.41 and 5.24 GHz with minimum insertion losses of 0.86 and 1.97 dB, respectively. The measured results show a good HTS BPF performance. Moreover, the temperature-dependent center frequencies can be well described by the modified two-fluid model based formulas, indicating that the frequency shift in HTS BPF is dominated by the temperature dependence of the magnetic penetration depth.

Dual-Band Balanced BPF Using λ/4 Stepped-Impedance Resonators and Folded Feed Lines

This paper presents a second-order dual-band balanced bandpass filter (BPF) designed using bi-section quarter-wavelength (λ/4) stepped-impedance resonators (SIRs) and folded feed lines. The first two modes of the λ/4 SIRs are designed to resonate in the designated 2.4- and 5.2-GHz WLAN bands. High-impedance folded transmission-line sections are inserted in series with the feed lines to improve the overall impedance matching at the input/output ports, so that the signal transmission can be enhanced. In addition, the feed lines and λ/4 SIRs are properly arranged to form an all-stop-like coupling configuration for common-mode operation. For the first (second) operating band of interest, the fabricated balanced BPF printed on an FR4 substrate was measured to have a minimum differential-mode insertion loss of 3.03 dB (4.3 dB) and a minimum common-mode rejection level of as high as 15.7 dB (22.3 dB).

New Coupling Scheme for Microstrip Bandpass Filters With Quarter-Wavelength Resonators

A new coupling scheme for microstrip bandpass filters with quarter-wavelength (lambda/4) stepped-impedance resonators is proposed. In the proposed coupling scheme, two adjacent lambda/4 stepped-impedance resonators are coupled by directly connecting an admittance inverter between them. By properly designing the connecting position, one may adjust the coupling coefficient between two resonators so that narrow to broad bandwidth filters may easily be fabricated without coupling gaps. Here, the admittance inverter is realized by a lambda/4 stepped-impedance line. Based on the proposed coupling scheme and the conventional magnetic coupling structure, the filters with narrow or wide bandwidth may be designed and implemented. In addition, folded lines are adopted to make the filter size compact. In this study, a two-pole filter with a 3-dB bandwidth of 5.1% and two four-pole filters with 3-dB bandwidths of 33% and 51% are successfully fabricated. Good agreement between measured and simulated results is observed.

A 24-/60-GHz CMOS On-Chip Dual-Band Bandpass Filter Using Trisection Dual-Behavior Resonators

This letter presents the design and implementation of a 24-/60-GHz millimeter-wave dual-band on-chip bandpass filter using a 0.18-mum standard CMOS process. The concept of quarter-wavelength stepped-impedance resonator (lambda/4 SIR) is utilized to realize stopband characteristics at desired frequencies and reduce the chip size. The structure of the open-circuited dual-behavior resonators (OC-DBRs) produces one passband with two transmission zeros on either side. The size of the designed filter is 1.030 times 0.590 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

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 lambda <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> times 0.27 lambda <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> is implemented and its stopband is extended up to 8.25 <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> with an adequate rejection of greater than 32.49 dB, where <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> is the passband center frequency and lambda <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> is the microstrip guided wavelength at <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> .

Miniature Dual-Band Filter Using Quarter Wavelength Stepped Impedance Resonators

A miniature dual-band filter using quarter wavelength (lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> /4) stepped impedance resonators (SIRs) is proposed. Short and open SIRs are coupled together to realize lower and upper passbands, respectively. Miniaturization is achieved due to the use of lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> /4 resonators and a combline coupling structure. Two transmission zeros in a mid-stopband and one in each lower and upper stopbands are achieved. In order to see the capability of this structure to achieve different second passband frequencies, two dual band filters at frequencies of 2.45/5.25 GHz and 2.45/5.75 GHz are realized. Measured insertion losses are 1.3 dB and 2.3 dB and return losses are better than 17 dB and 18 dB at the first and second passband frequencies, respectively, with a mid-stopband attenuation better than 30 dB. The size of the filter is as compact as 19.0 times 5.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> on a RO 4003C (epsiv <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 3.38, h = 0.81 mm) substrate.