Spoof surface plasmon polariton band‐stop filter with single‐loop split ring resonators

A novel band‐stop filter with single‐loop split ring resonators (SRRs) is proposed for spoof surface plasmon polaritons (SPPs) at millimeter wave frequencies, achieving a miniaturized size of 0.052λ₀ × 0.278λ₀ at its resonant frequency. The SRRs provide both a low‐pass response as the rectangular corrugations used in the conventional SPPs and an additional band‐stop response induced by the resonance of SRRs. To verify this design, a back‐to‐back device with two coplanar waveguides as the input and output feeding was fabricated and characterized, the measured S‐parameters of which agree well with the simulation. The measured stop band is centered at 49 GHz with a ?10‐dB bandwidth of 4.1 GHz and a high Q‐factor of 93, in which the maximum attenuation is 31 dB. The filter has a low insertion loss of less than 2.8 dB in the pass band. Such approaches may find many applications to achieve compact millimeter wave circuits.     

A compact reconfigurable bandpass/lowpass filter with independent transmission zeros based on generalized NRI metamaterial

This article introduces a new design and analysis of a compact reconfigurable bandpass/lowpass filter based on compact negative refractive index metamaterial transmission line. The filter equivalent circuit has been designed as a cascade of three cells of bisected‐Π/Π configuration. The reconfigurable function was achieved using inserted switches in ON and OFF modes within the cells. The filter works as bandpass when all switches are in ON condition and for lowpass switch‐1 is in OFF and switch‐2 in ON condition. The low pass filter has 3‐dB cutoff frequency of 3.25 GHz with a selectivity of 170 dB/GHz. The bandpass filter is cantered at 3.65 GHz and has a well‐matched pass band with insertion loss of 0.2 dB and wide stop band with two transmission zeros (TZs). The frequency positions of TZs are independently varying with series and shunt loading elements. The filter performance has been validated through circuit model, electromagnetic simulation, and experimental measurements. The electrical size of bandpass filter excluding feed line is 0.22 λ_g × 0.20 λ_g (12 × 11 mm²) at center frequency of 3.65 GHz and for lowpass filter is 0.19 λ_g × 0.18 λ_g at cutoff frequency of 3.25 GHz. The filter can be applied in suitable for different wireless applications.     

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.     

Modified Wilkinson power divider with harmonics suppression and compact size for GSM applications

In this article, a modified microstrip Wilkinson power divider with harmonics suppression for GSM communications applications is presented. For low‐pass filter designing, one open stub, one radial resonator, and two rectangular resonators are used. According to results related to insertion losses (|S₂₁| and |S₃₁|), stopband is wide and equal to 7.5 GHz (3.4‐10.9 GHz), under the condition of 20 dB harmonic suppression level. The results show that at the designed frequency of 1.8 GHz, the input return loss (|S₁₁|) and output return losses (|S₂₂| and |S₃₃|) are better than 22 dB, and the isolation between of output ports (|S₃₂|) is better than 30 dB. The size of the proposed power divider is compact and equal to 10.6 × 14.6 mm². Finally, the proposed power divider was fabricated and the measurement results illustrate a good agreement with simulation results.     

Metamaterial‐inspired miniaturized antenna loaded with IDC and meander line inductor using partial ground plane

In this article, a novel omnidirectional compact dual band metamaterial‐inspired antenna with CPW feed has been proposed for application of GSM 1800 (1.71‐1.785 GHz/1.805‐1.879 GHz), GSM 1900 (1.85‐1.91 GHz/1.93‐1.99 GHz), UMTS (1.92‐2.17 GHz), WLAN/Wi Fi (4.9, 5, 5.9 GHz), HiperLAN1 (5.15‐5.3 GHz), and HiperLAN2 (5.47‐5.72 GHz) using a combination of meander line inductor and interdigital capacitor (IDC). The antenna consists of complimentary right/left handed (CRLH) transmission line on both sides of patch to excite zeroth order mode (n = 0). The rectangular slotted stubs act as a virtual ground for the structure using a short circuit condition at the end of the IDC. The zeroth order resonance (ZOR) frequency is mainly controlled by IDC and partially with the meander line inductor. The designed antenna operates from 1.72 to 2.22 GHz and 4.25 to 5.88 GHz with radiating size of 0.56λ_o × 0.35λ_o (32 × 20 mm²), where λ_o is the free‐space wavelength at ZOR frequency of 5.27 GHz. The proposed antenna offers measured impedance bandwidth (|S₁₁| <?10 dB) of 25.3 and 18.7% at 1.95 and 5.28 GHz and covers the targeted frequency bands. The proposed structure offers omnidirectional radiation patterns are congruous throughout the working band.     

Wide stopband harmonic suppressed low‐pass filter with novel DGS

In this article, a wide stopband 20 dB harmonically suppressed low‐pass filter (LPF) using novel defected ground structures (DGSs) is proposed. The DGSs has been analyzed as a low pass filter which shows a significant harmonics suppression in the stopband. The lumped parameter equivalent of the DGSs has been developed to show its effectiveness. The modified equivalent circuit model of the filter helps in placing the transmission zero near ?3 dB cutoff frequency. The LPF is designed on a 0.10 λ_g× 0.09 λ_g substrate size where λ_g is guided wavelength at ?3 dB cut‐off frequency (f_c) equal to1 GHz. The simulation shows a 20 dB harmonic suppression up to 50 f_c. The prototype of the LPF has been developed and with the available vector network analyser, the S‐parameters have been measured upto 20 GHz (20 f_c).The state of the art comparison of the LPF shows a high figure of merit equal to 26 250 which is higher than many recently published works.     

Circularly polarized stacked patch antenna array with enhanced bandwidth for S‐band applications

In this article, a circularly polarized coupled slot 1 × 4 stacked patch antenna array with enhanced bandwidth is proposed for S‐band applications. Initially, a patch antenna radiating at 2.79 GHz is designed and maximum energy from feedline to patch element is coupled using two rectangular slots. Whereas, a parallel feedline structure is designed to provide polarization flexibility by creating 0, 90 , and 180^o phase differences. Then, a truncated patch element is vertically stacked in the design to achieve broader bandwidth of 600 MHz over frequency range from 2.4 to 3.0 GHz. Finally, a coupled slot 1 × 4 array stacked antenna array having feedline line structure to provide 90^o phase difference for circular polarization is designed and fabricated for measurements. It is observed that the final design achieved target specification having impedance matching (|S₁₁ | (dB) < ?10 dB over 2.4 to 3.0 GHz, broad band circular polarization, and 11.5 dBic total gain. Overall, a good agreement between simulated and measurement results is observed.     

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.     

Design and optimization of a tunable W‐band subharmonic cavity based Gunn diode oscillator using computer‐aided design technique

In this work, a systematic computer‐aided design technique is proposed to minimize the fabrication iteration for the design and development of W‐band subharmonic Gunn diode oscillator with wideband tunable bandwidth at W‐band. Gunn diode based single diode oscillator structure was divided into passive and active parts to facilitate the modeling of the component on appropriate simulation environment. Resonating structure and package of Gunn diode are modeled as passive circuit in high frequency structure simulator (HFSS). To satisfy the oscillator design equation, disc‐post resonating structure is tuned in HFSS and its S‐parameters are collaborated with the model of Gunn diode in advanced design system. Magnitude and phase of reflection coefficient (S11) is observed to ascertain the desired frequency of oscillation. Proper tuning of disc‐post structure is done on simulation platform, which reduces the fabrication complexity and cost as well. The measurement results validate the models designed using EM and circuit simulator. The measured maximum stable RF power without any fabrication iteration is 14.2 dBm. A tunable bandwidth of 4 GHz with power output ripple of ±1 dB is measured by using a movable backshort.     

CSRR‐loaded T‐shaped MIMO antenna for 5G cellular networks and vehicular communications

This article proposes a multiple input multiple output (MIMO) antenna for 5G‐based vehicular communication applications. The designed MIMO antenna consist of two element iterated T‐shape antenna with defected ground structure (DGS) and split ring resonator. The antenna providing reflection coefficient S₁₁ s₁₁ ≤10 dB and bandwidth of 6.3 and 3.96 GHz over the frequency range of 26.83 to 33.13 GHz and 34.17 to 38.13 GHz, respectively. For the suitable future vehicular millimetric wave communications, this antenna achieved resonant frequencies at 28, 33, and 37 GHz. The designed antenna has achieved peak gain of 7.11 dB in operating band. It is fabricated on 12 x 25.4 x 0.8 mm³ Rogers RT duroid 5880 substrate with dielectric constant (ε_r) of 2.2. The antenna is placed on vehicle in virtual environmental using ANSYS SAVANT tool and the simulated results are showing good matching with the measured results of proposed MIMO antenna.     

A wideband circularly polarized slot antenna with antipodal strips for WLAN and C‐band applications

A single‐fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90° phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz‐7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S₁₁| < ?10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C‐band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ₀ × 0.40λ₀ and thickness of 0.02λ₀ where λ₀ is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15‐5.85 GHz) and a wide variety of C‐band wireless applications.     

Compact tri‐notched ultrawideband bandpass filter design using CSRR,DGS, and FMRR configurations

The folded multiple‐mode resonators with complementary split ring resonator (CSRR), and defected ground structures (DGS) are introduced for notched ultrawideband (UWB) bandpass filter (BPF) design in this article. Using the CSRR, FMRR, notched wide‐band BPF, a notch response can exist in the UWB passband for blocking the interference. Adjusting the size factor of CSRR, the wide tuning ranges of notch frequencies included the desired frequencies of 5.2/5.8 GHz are achieved. The lower insertion loss (0.31 dB), higher rejection level (?48.40 dB), wider bandwidth (FBW 75%), and wider stopband (extended to 2.01 f₀ below ?20 dB rejection level) of UWB band at the central frequency f₀ = 4.58 GHz are obtained. Second, design a CSRR, DGS, FMRR, tri‐notched UWB filter, the wider bandwidth (3.1–9.8 GHz) with FBW = 126%, lower insertion loss (0.26 dB), and higher rejection level (?44 dB) of UWB band at central frequency f₀ = 5.6 GHz are presented. Using the CSRR and interdigital couple, three notch responses can exist in the UWB passband for blocking the interference signals. Adjusting the size factor of CSRR and interdigital couple, the wide tuning ranges of notch frequencies included the desired frequencies of 5.18/6.10/8.08 GHz are achieved. The wide tuning ranges of three notched frequencies cover from 5.0 to 8.4 GHz. It is a simple way to control the notch responses. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:571–579, 2014.     

High inter‐port isolation dual circularly polarized slot antenna with interdigital capacitor

A planar dual circularly polarized slot antenna is presented. The designed antenna has two tilted “8” shaped slots fed by microstrip lines, one each for transmission (T_X) and reception (R_X) operations. The isolation between the two ports (T_X and R_X) is augmented by means of an interdigital capacitor based bandstop filter. The proposed antenna has an impedance bandwidth of 361 MHz centered at 2.293 GHz (2.113‐2.474 GHz) with the isolation between the ports being >17.6 dB which goes up to a value as high as 46 dB within the band of operation. The 3 dB axial ratio (AR) bandwidth is 11.52% centered at 2.1275 GHz (2.005‐2.25 GHz). Because of its high inter‐port isolation within the AR bandwidth, the design is suitable as a full‐duplex antenna for applications in S‐band.     

Band‐pass filter design using modified CSRR‐DGS

In this article, a novel compact band‐pass filter (BPF) with sharp cutoffs and a wide stop‐band is presented. The BPF is basically designed by cutting a modified complementary split‐ring resonator (CSRR) from the ground of two separated microstrip feed lines and has a 71% fractional bandwidth from 4.1 to 9 GHz. Because of the high insertion loss, the designed filter should be packed in a metallic cavity that has undesirable resonances in the stop‐band of the BPF. For eliminating cavity resonances, an evolutionary optimization technique based on changing the pixels of the CSRR defected ground structure is used. A prototype of the final structure obtained from the optimization technique is fabricated. The measurement results show that the optimized filter have a pass band from 4 to 8 GHz with a rejection better than 15 dB from 4 to 15 GHz. The designed filters have compact dimensions of 12 × 12 × 0.787 mm³. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:544–548, 2014.     

A modified split ring resonator based printed compact monopole UWB antenna with spiked elliptical radiator having five band rejection features

A coplanar waveguide (CPW) fed printed compact monopole antenna with five band rejection features is presented. Wide bandwidth was achieved by beveling the lower part and adding a modified ellipse on the upper portion of the patch. An inverted circular arc, single circular split ring resonator (SRR) with wide opening and two symmetrical circular single SRRs were embedded for obtaining three stop‐band characteristics. Two symmetrical slits were inculcated in the ground forming defected ground structure (DGS) to get another stop‐band characteristic. Two concentric rectangular modified SRRs were etched to obtain a higher frequency stop‐band feature. The proposed antenna was designed, fabricated, and experimentally tested for the validation of results. The overall dimensions of the proposed antenna were 29 mm × 24 mm × 1.6 mm. The measured impedance bandwidth of the antenna was 2.87 to 13.3 GHz at | S₁₁ |< ? 10 dB. The measured results show that the proposed antenna has five band notches centred at 3.96, 4.35, 5.7, 8.54, and 9.95 GHz to reject WiMAX band (3.65‐4.04 GHz), ARN band (4.29‐5.18 GHz), WLAN band (5.5‐6.9GHz), ITU‐8 band (7.37‐8.87), and amateur radio band (9.2‐10.3 GHz) respectively. The proposed antenna maintains omnidirectional radiation pattern in H‐Plane and dumbbell‐shape radiation pattern in E‐plane. Further, stable gain over the whole UWB except at notched frequency bands was reported.     

Dual‐functional QM SIW cavity integrating two‐element MIMO antenna and second‐order bandpass filter

A quarter‐mode (QM) substrate‐integrated‐waveguide (SIW) cavity is designed as a dual‐functional component. By etching three slots, four sub‐cavities are formed and then two of them with the same size are individually fed by a coaxial port. Three resonating frequencies are excited in the single QM SIW cavity. One of them can radiate cavity energy input by these ports into free space, implying a two‐element multiple‐input‐multiple‐output (MIMO) antenna, whereas the other two can transmit energy from one port to the other port, indicating a second‐order bandpass filter. Moreover, antenna isolation and filter bandwidth can be adjusted to a certain degree. A prototype with the overall size of 0.40λ₀ × 0.40λ₀ × 0.02λ₀ has been fabricated. The integrated bandpass filter demonstrates the measured center frequency of 3.8 GHz and operating bandwidth of 32 MHz while the integrated MIMO antenna exhibits the frequency of 3.4 GHz, bandwidth of 67 MHz, port isolation of 18.0 dB, radiation gain of 4.0 dBi, and envelope correlation coefficient of 0.25.     

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.     

Stub‐loaded square loop bandpass filter with equiripple response in both delay and magnitude

It is shown that a stub loaded square loop filter, composed of six sections of commensurate transmission line, can achieve equiripple response in both magnitude and group delay simultaneously, when the admittances of the lines are properly chosen. Design formulas are given to calculate the admittances by given specifications such as fractional bandwidth and in‐band magnitude ripple. An interesting property of this filter is that the group delay can be adjusted while the in‐band magnitude response keeps almost unchanged. For verification, a filter sample is designed, fabricated and measured. In experiment, it exhibits a delay variation of 0.22 ns and minimal insertion loss of 0.21 dB within its passband (|S₁₁| < ?13.8 dB) from 0.48 to 1.52 GHz, which agree well with the theoretical predictions.     

Design and its state‐of‐the‐art of different shaped dielectric resonator antennas at millimeter‐wave frequency band

This review article provides an extensive literature survey on the research progress of dielectric resonator antenna (DRA) at millimeter‐wave frequency band that includes concepts of DRAs, their empirical formulae and design methodologies for different shaped DRAs at 60 GHz frequency band. The different shaped DRAs such as cylindrical, rectangular, hexagonal, and octagonal at 60 GHz are designed, simulated and analyzed using CST microwave studio solver. The ?10 dB impedance bandwidth of cylindrical, rectangular, hexagonal, and octagonal DRAs are 52.7 to 62.8 GHz, 57 to 62.2 GHz, 55.8 to 64.2 GHz, and 54.2 to 63.5 GHz, respectively. The idea behind getting broad impedance bandwidth is due to use of double‐layer substrate with different permittivity (ε_r1 = 4 and ε_r2 = 11.9). Empirical formulae are deduced for hexagonal and octagonal DRA, by studying the analogy of dielectric resonator geometry. Consequently, the mode of different shaped DRAs, that is, HEM₁₁₁ and TE₁₁₁ are investigated by the electric field and magnetic field distribution. With these analysis, a comprehensive research review over the period of the last two decades is carried for investigating various techniques, targeted to realized gain, circular polarization, and impedance bandwidth. Along with these analysis the state‐of‐the‐art at different shaped DRAs at mm‐wave frequency band are also reported.     

A compact UWB MIMO antenna with neutralization line for WLAN/ISM/mobile applications

A novel design of 2 × 2 multiple‐input‐multiple‐output (MIMO) antenna is reported for ultra‐wideband applications. The neutralization line is implemented to minimize the mutual coupling between the radiating patches. The overall dimension of the designed antenna is 21 × 34 × 1.6 mm³. This antenna covers the measured bandwidth of 95.0% (3.52‐9.89 GHz) with better isolation (≤?22 dB) over the entire operating frequency band. The measured gain varies from 3.08 to 5.12 dBi over the entire band. The various antenna parameters such as S‐parameters, gain, efficiency, envelope correlation coefficient, mean effective gain, channel capacity loss, total active reflection coefficient, and radiation patterns are calculated and corresponding results are validated with the measured results.