Compact ultra‐wideband bandpass filter with configurable stopband based on diamond‐shape resonator

An ultra‐wideband compact bandpass filter (BPF) with configurable stopband by tuning transmission zeroes is proposed in this paper. The ultra‐wideband bandpass response is based on a diamond‐shape resonator consisting of a pair of broadside coupled diamond‐shape microstrip lines, within which a diamond shape defected ground structure (DGS) is etched in the middle. Flexible transmission zeros realized by open and short stubs can be easily adjusted to improve band selectivity and harmonic suppression. Measurement result shows that the dedicated device has a 3 dB fractional bandwidth of 148% (0.94‐6.36 GHz) with 20 dB rejection stopband from 6.87 to 9.7 GHz (77.5%) which agrees good with the simulate performance. The overall size of the proposed BPF is 0.27 λ_g × 0.23 λ_g.     

Miniaturized frequency‐agile bandpass filter integrated single‐pole double‐throw switch

This article presents a miniaturized frequency‐agile bandpass filter (BPF) integrated single pole double throw (SPDT) switch using common LC resonator. The BPF‐integrated on‐sate channel is constituted by the capacitively coupled LC resonators with loaded varactor diodes and reverse‐biased p‐i‐n diodes. The off‐state channel with high suppression is built when the p‐i‐n diodes loaded LC resonators is forward‐biased. As an example, a frequency‐agile BPF‐integrated SPDT switch with constant 3‐dB fractional bandwidth of 18.4% is designed. Its fabricated circuit area including bias circuit but excluding feeding lines is 0.105 λ_g × 0.079 λ_g. Measured results show that its 3 dB operating frequency bandwidth covers from 0.499 to 1.077 GHz with in‐band insertion loss varying from 4.15 to 3.15 dB. Off‐state suppression better than 37.8 dB, port‐to‐port isolation better than 51.1 dB, and good return loss can be also observed.     

Compact differential dual‐band bandpass filter using single quad‐mode metal‐loaded dielectric resonator

This letter presents a novel miniaturized differential dual‐band bandpass filter (BPF) using a single quad‐mode metal‐loaded dielectric resonator (DR). The differential dual‐band BPF is designed in a single‐cavity configuration with one quad‐mode DR and four feeding probes, featuring compact size. The rectangular DR is directly mounted on the bottom of the metal cavity and covered by a metal plate on the top surface. It allows two pairs of orthogonal modes (LSE₁₀ and LSM₁₀), which can be differentially excited and coupled by introducing proper perturbation for constructing dual‐band differential‐mode frequency response. To validate the proposed idea, a compact differential BPF with good performance using a quad‐mode DR cavity is designed, fabricated, and measured. The simulated and measured results with good agreement are presented.     

Coplanar waveguide‐fed electrically small dual‐polarized short‐ended zeroth‐order resonating antenna using Ω‐shaped capacitor and single‐split ring resonator for GPS/WiMAX/WLAN/C‐band applications

This work explains the design and analysis of a triple‐band electrically small (ka = 0.56 < 1) zeroth‐order resonating (ZOR) antenna with wideband circular polarization (CP) characteristics. The antenna compactness is obtained due to ZOR frequency of composite right/left‐handed (CRLH) transmission line (TL) and wideband CP radiation are achieved due to the introduction of single‐split ring resonator and asymmetric coplanar waveguide fed ground plane. The proposed antenna obtains an overall electrical size including the ground plane of 0.124 λ₀ × 0.131 λ₀ × 0.005 λ₀ at 1.58 GHz and physical dimension of 23.7 × 25 × 1 mm³ are achieved. The antenna provides a size reduction of 44.95% compared to a conventional monopole antenna. The novelty behind the ohm‐shaped capacitor is the generation of extra miniaturization with better antenna compactness. The antenna provides dual‐polarized radiation pattern with linear polarization radiation at 1.58 and 3.54 GHz, wideband CP radiation at 5.8 GHz. The antenna measured results shows good impedance bandwidth of 5%, 6.21%, and 57.5% for the three bands centered at 1.58, 3.54, and 5.8 GHz with a wider axial ratio bandwidth (ARBW) of 25.47% is obtained in the third band. The antenna provides a higher level of compactness, wider ARBW, good radiation efficiency, and wider S₁₁ bandwidth. Hence, the proposed antenna is suitable for use in GPS L1 band (1.565‐1.585 GHz), WiMAX 3.5 GHz (3.4‐3.8 GHz) GHz, WLAN 5.2/5.8 GHz (5.15‐5.825 GHz), and C‐band (4‐8 GHz) wireless application systems.     

A compact dual‐band zeroth‐order resonator antenna loaded with meander line inductor

A novel zeroth‐order resonator (ZOR) meta‐material (MTM) antenna with dual‐band is suggested using compound right/left handed transmission line as MTM. In this article, suggested antenna consists of patch through series gap, two meander line inductors, and two circular stubs. The MTM antenna is compact in size which shows dual‐band properties with first band centered at 2.47 GHz (2.05‐2.89 GHz) and second band is centered at 5.9 GHz (3.70‐8.10 GHz) with impedance bandwidth of (S₁₁ < ? 10 dB) 34.69% and 72.45%, respectively. At ZOR mode (2.35 GHz), the suggested antenna has overall dimension of 0.197λ_o × 0.07λ_o × 0.011λ_o with gain of 1.65 dB for ZOR band and 3.35 dB for first positive order resonator band which covers the applications like Bluetooth (2.4 GHZ), TV/Radio/Data (3.700‐6.425 GHz), WLAN (5‐5.16 GHz), C band frequencies (5.15‐5.35, 5.47‐5.725, or 5.725‐5.875 GHz) and satellite communication (7.25‐7.9 GHz). The radiation patterns of suggested structure are steady during the operating band for which sample antenna has been fabricated and confirmed experimentally. It exhibits novel omnidirectional radiation characteristics in phi = 0° plane with lower cross‐polarization values.     

Novel hybrid resonant structures and its applications in compact multiband bandpass filters

A novel hybrid resonant structure which can realize compact multiband bandpass filters (BPFs) and its design method are proposed in this article. The hybrid resonant structure is a dual‐plane structure which is an effective combination of a pair of microstrip stepped impedance resonators on the top layer and two nested dual‐mode defected ground structure resonators on the bottom layer. A triband BPF adopting this hybrid resonant structure was presented which was operating at 2.4/5.7 GHz (wireless local area network application) and 3.5 GHz (worldwide interoperability for microwave access application). The size of this filter is only 0.14λ₀ × 0.11λ₀. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:690–696, 2014.     

Ultrawideband high‐gain dual‐polarized antenna with anti‐interference capability

In this article, a high‐gain dual‐polarized antenna with band‐rejection capability for ultrawideband (UWB) applications is proposed. Tapered dipoles are chosen as a primary radiator to achieve UWB operation and it is reflected by a metallic cavity reflector for high gain radiation. A notch at WLAN band is realized by etching a set of four bent slots in the radiating elements. The measured results demonstrate that the proposed design with overall dimensions of 0.69λ _L × 0.69λ _L × 0.16λ _L (λ _L is free‐space wavelength at the lowest operating frequency) has operating bandwidth of 95.1% (3.2‐9.0 GHz) and the rejected frequency band from 5.0 to 5.9 GHz. Additionally, good unidirectional radiation patterns with a broadside gain from 8.1 to 11.5 dBi and radiation efficiency of better than 90% are also achieved.     

Independently controllable dual‐band microstrip bandpass filter using quadruple‐mode stub‐loaded resonator

In this article, a quadruple‐mode stub‐loaded resonator (QM‐SLR) is introduced and its four modes are excited using a simple approach, which can provide a dual‐band behavior. By changing the length of the loaded stubs, independently tunable transmission characteristics of the proposed quadruple‐mode stub‐loaded resonator were extensively described for filter design. Moreover, microwave varactors were adopted to represent the length variation of the loaded stubs for the dual‐band tunability. The equivalent circuit modeling of the open stub with microwave varactor was given and discussed. Then, adopting the compact quadruple‐mode stub‐loaded resonator with three varactors, an independently controllable dual‐band bandpass filter (BPF) was designed, analyzed, and fabricated. Its separated bandwidths and transmission zeros can be tuned independently by changing the applying voltage of the microwave varactors. A good agreement between simulated and measured results verified the design methodology. The proposed filter possesses compact size, simple structure, and excellent dual‐band performances. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:602–608, 2016.     

Compact quad‐channel high‐temperature superconducting diplexer based on stub‐loaded square ring resonator

A compact quad‐channel high‐temperature superconducting diplexer based on stub‐loaded square ring resonator (S‐LSRR) is proposed. The proposed resonator consists of a square ring with symmetrically loaded two open‐circuited stubs and provides four resonant modes for quad‐channel applications. Even‐ and odd‐mode methods are applied to analyze the S‐LSRR. Analytical study shows that four resonant modes of one S‐LSRR can be designed in two pairs and applied to construct two of four channels of the designed diplexer. A square patch is added to the resonator for providing an additional parameter to tune the resonant modes. Based on the proposed resonator, a quad‐channel diplexer with center frequencies of 2.4, 3.2, 3.9, and 5.6 GHz is designed. For demonstration, the diplexer is fabricated on 2‐in‐diameter 0.5 mm‐thick MgO wafer with double sided YBa₂Cu₃O_y films and measured at 77 K. Good agreement between the simulation and measurement is obtained. The diplexer has a compact size of 0.25 λ_g × 0.45 λ_g, where λ_g is guided wave length at the center frequency of first channel.     

Compact Dual‐/Tri‐/Quad‐Band banpass filters using shorted stub loaded stepped‐impedance resonator

In this article, the shorted stub loaded stepped‐impedance resonator (SSLSIR) with the individually tunable first even resonant mode and first odd resonant mode is applied to design dual‐, tri‐, and quad‐band bandpass filters (BPFs). The SSLSIR dual‐band BPF with asymmetrical coupling is realized using the first even resonant modes and the first odd resonant modes of a set of SSLSIRs. Then, the high‐impedance feeding lines of SSLSIR dual‐band BPF is modified to produce a new passband, and thus a new tri‐band BPF is realized. The proposed quad‐band BPF consists of two sets of SSLSIRs with symmetrical coupling. Each of the designed circuits occupies a very compact size and has a good in‐band out‐of‐band performance. Good agreements are observed between the simulated and measured results. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:601–609, 2015.     

A thin‐layer dielectric and metamaterial unit‐cell stack loaded miniaturized SRR‐based antenna for triple narrow band 4G‐LTE applications

This article presents the design of a miniaturized dual‐band antenna for long‐term evolution (LTE) application is presented. In the basic antenna design, split ring resonator was loaded in the radiating plane of the patch and frequency of resonance was further modified with the help of E‐shaped stub. The antenna has been fabricated using FR‐4 substrate and the measured dual bands at 2.11 and 2.665 GHz are found in a close match with the simulated data. By placing a thin dielectric resonator of permittivity ε _r = 10.2 and thickness of 1.27 mm, two closely spaced narrow bands are obtained at 2.217 and 2.28 GHz. A novel metamaterial unit‐cell having near‐zero refractive index is designed and mounted above the dielectric resonator. This stack configuration generates triple narrow frequency band in the LTE 2 GHz spectrum range. The overall size of the proposed antenna is 20 × 25 mm².     

A vertex‐fed hexa‐band frequency reconfigurable antenna for wireless applications

Present article embodies the design and analysis of an octagonal shaped split ring resonator based multiband antenna fed at vertex for wireless applications with frequency‐band reconfigurable characteristics. The proposed antenna is printed on FR4 substrate with electrical dimension of 0.4884 λ × 0.4329 λ × 0.0178 λ (44 × 39 × 1.6 mm³), at lower frequency of 3.33 GHz. The antenna consists of SRR based vertex fed octagonal ring as the radiation element and switchable reclined L‐shaped slotted ground plane. Antenna achieves six bands for wireless standards viz: upper WLAN (5.0/5.8 GHz), lower WiMAX (3.3 GHz), super extended C‐band (6.6 GHz), middle X band (9.9 GHz—for space communication), and lower K_U band (15.9 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The proposed design achieves hexa band characteristics during switching ON state of PIN diode located at reclined L‐shaped slot in the ground plane. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.     

Design of novel compact dual‐band filtering power divider using stepped‐impedance resonators with high selectivity

A novel compact dual‐band power divider with filtering responses is presented in this article. The proposed circuit utilizes coupled quarter‐wavelength stepped‐impedance resonators. By controlling these resonators, dual‐band operation can be realized. Furthermore, a resistor is connected between the two open ends of the input feed line to obtain good isolation at two bands. Source load coupling is utilized to enhance the selectivity. To verify the proposed idea, a filtering power divider with the operating frequencies of 2.4 and 5.8 GHz is implemented. Good agreement between the simulated and measured results validates the proposed idea. The total size of the circuit is 0.23λ_g × 0.28λ_g, where λ_g is the guide wavelength of 2.4 GHz. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:262–267, 2016.     

Novel slotted stepped‐impedance resonator and its application to compact and high performance bandpass filter and diplexer design

By etching slots in the low‐impedance section of the conventional stepped‐impedance resonator, a novel slotted stepped‐impedance resonator (SSIR) is proposed. As two examples, a fourth‐order bandpass filter (BPF) operating at 1 GHz with a size of 0.078 λ_g × 0.062 λ_g and a miniaturized diplexer operating at 0.9/1.57 GHz with a size of 0.054 λ₀ × 0.086 λ₀ are designed based on the proposed SSIR. The fabricated BPF exhibits a high selectivity and a wide ?30 dB rejection upper stopband from 1.13 f₀ to 6.52 f₀, while the fabricated diplexer has up to ?60 dB output isolation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

An equivalent circuit model for the wide‐band band‐pass filter with the modified Minkowski‐island‐based fractal patch

An equivalent circuit model for the wide‐band band‐pass filters (BPFs) using modified Minkowski‐island‐based (MIB) fractal patch are proposed in this article. The BPF is mainly formed by a square patch resonator in which a modified MIB fractal configuration with second‐order iteration is embedded in the patch. By the equivalent circuit model with diamond structure, the wide‐band responses are analyzed. The design procedure included equivalent circuit model is available for wide‐band design. For wide‐band characteristics, at 5.0 GHz central frequency, it has good measured characteristics including the wider bandwidth of 3.14–6.89 GHz (3‐dB fractional bandwidth of 75%), low insertion loss of 0.39 dB, and high rejection level (?48.5/?44.9 dB). The patch size is 7.4 λ 7.4 mm² (0.25 λ_g × 0.25 λ_g) with 14.1% reduction. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:170–176, 2014.     

A novel dual‐band bandpass filter using co‐directional split ring resonators with closely spaced passbands and wide upper stopband

In this article, interdigital capacitor loaded co‐directional split ring resonators (CDSRRs) and their dual‐band bandpass filter applications are proposed. The proposed resonator is formed by nested open loop resonators having open ends at the same place unlike conventional split ring resonators (SRRs). In addition, the inner open loop resonator has interdigital capacitor located between the open ends. The proposed resonator exhibits dual resonance behavior with a small center frequency ratio. Both of resonance frequencies can be controlled due to the changes in the interdigital capacitor and the electrical length of the outer resonator. A dual‐band microstrip bandpass filter is designed by using the proposed CDSRR. Two CDSRRs are used to obtain two poles in each passband. Overall electrical length of the designed filter is 0.23 λ_g × 0.14 λ_g (0.0329 λ_g²), where λ_g is the guided wavelength for the used substrate at the lowest passband center frequency of 1.8 GHz. A small center frequency is obtained by adjusting the second passband at 2.27 GHz. A very wide upper stopband, closely spaced passbands, low insertion losses and high selectivity at both passbands can be obtained by means of the proposed structure. The designed filter was also fabricated and tested. The measured results show a very good agreement with the predicted results.     

Inter‐digital coupled dual‐mode patch resonator with crossed‐island configuration for tri‐band filter design

The miniaturized dual‐mode tri‐band band‐pass filters (BPF) using crossed‐island patch resonator is proposed in this article. The BPF is mainly formed by a square patch resonator in which a crossed‐island configuration is embedded in the patch. The patch size reduction with 74.4% is achieved. By the perturbation and the alternative inter‐digital coupling, the tri‐band responses are obtained. The proposed filter covers the required bandwidths for WLAN band (2.26–3.11 GHz and 5.02–6.0 GHz) and X‐band (7.58–8.41 GHz) applications. Five transmission zeros are placed between three pass‐bands and resulted in a good isolation. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:457–463, 2014.     

Novel configuration of ultra‐wide band uni‐planar configuration of complementary split ring resonator composite right/left‐handed based band pass filter with sharp roll off and good stopband attenuation

In this paper, a compact novel simple design of ultra‐wide bandpass filter with high out of band attenuation is presented. The filter configuration is based on combining an ultra‐wide band composite right/left‐handed (CRLH) band pass filter (BPF) with simple uni‐planar configuration of complementary split ring resonator (UP‐CSRR). By integrating two UP‐CSRR cells, the ultra‐wideband CRLH filter roll‐off and wide stopband attenuation are enhanced. The filter has 3 dB cutoff frequencies at 3.1 GHz and 10.6 GHz with insertion loss equals 0.7 dB in average and minimum and maximum values of 0.48 dB and 1.05 dB, respectively over the filter passband. Within the passband. The transition band attenuation from 3 dB to 20 dB is achieved within the frequency band 1.9 GHz to 3.1 GHz (48%) at lower cutoff and the frequency band 10.6 GHz to 11.4 GHz (7%) at upper stopband. Moreover, the filter has a wide stopband attenuation >20 dB in frequencies 11 GHz to 13.6 GHz (21%) and ends with 3 dB cutoff frequency at 14.8 GHz. Furthermore, the designed filter size is very compact (23 × 12 mm²) whose length is only about 0.17 λ_g at 6.85 GHz. The filter performance is examined using circuit modeling, full‐wave simulations, and experimental measurements with good matching between all of them.     

Poststress RF‐drifts of dual‐band LC VCO in 0.18‐μm CMOS technology

This article studies the RF‐property of a dual‐band voltage‐controlled oscillator (VCO). The designed circuit consists of a dual‐resonance LC resonator and a Colpitts negative resistance cell. The dual‐resonance LC resonator comprises a series‐tuned LC resonator and a parallel resonant resonator. The proposed VCO has been implemented with the TSMC 0.18 μm 1P6M CMOS technology. The VCO can generate differential signals in the frequency range of 3.0–3.37 GHz and 6.95–7.40 GHz with core power consumption of 10.08 and 10.24 mW at the dc drain‐source bias V_DD of 1.4 V, respectively. The die area of the dual‐band VCO is 0.485 × 0.800 mm². The circuit was operated at V_DD = 3 V for 8 h and significant drift in RF parameters was found. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:243–248, 2014.     

Integrated circular polarized microstrip antenna with dual‐mode‐polarization insensitive characteristics

A dual‐mode circularly polarized compact antenna with integrated left‐hand and right‐hand circular polarization (LHCP and RHCP) is presented in this work. A multilayer arrangement of a square patch and square ring structure with an irregular transmission line is analyzed for dual‐band, dual‐CP operation. To realize dual mode propagation the proposed structure is excited using electromagnetic coupling technique. Succeeding proximity feeding with T‐stub match is analyzed, which conveys impedance bandwidth of 180 and 300 MHz within |S₁₁| < ?10 dB at 3.5 and 5.5 GHz. The designed CP elements is suitably arranged with feed line for generating two orthogonal polarization of equal amplitude and a 90° phase difference at both the resonant modes (TM₁₀ and TM₀₁). Alterable LHCP and RHCP performance is realized by altering the compensated position and peculiar angle. Having both LHCP and RHCP polarization this design shows polarization insensitive characteristic. Each LHCP and RHCP antenna element accomplished a 3‐dB AR of 70 and 120 MHz with a gain up to 6 dBi. With a low profile of 0.27λ₀ × 0.27λ₀ × 0.04λ₀, the CP antenna is fabricated, and the performance is validated through experimental analysis. With all the viable characteristics, the antenna is proposed for Wi‐MAX/WLAN communication.