On the effect of ground‐plane thickness on an aperture‐coupled dielectric resonator antenna

A hemispherical dielectric resonator antenna excited by a microstrip feedline through a narrow slot in a thick ground plane is studied theoretically and experimentally. A numerical method based on a combination of the spectral Green's function, modal Green's function, and the method of moment is used to investigate the input characteristics of the dielectric resonator antenna system. The effects of ground‐plane thickness on input resistance, resonant frequency, and impedance bandwidth of the dielectric resonator antenna are discussed. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 271–277, 2000.     

A CPW‐fed band notched wideband circularly polarized ZOR antenna based on CRLH‐TL approach

This article presents design and analysis of three wide band zeroth‐order resonance antennas (antennas I, II, and III) using composite right and left‐handed transmission line (CRLH‐TL) approach. Coplanar waveguide technology, single layer via‐less structures are used to have the design flexibility. The bandwidth characteristics are analyzed by using lumped parameters of CRLH‐TL. By introducing a simple slot in the ground plane of antenna I both bandwidth enhancement and circularly polarization characteristics are achieved in antenna II. Another quarter wave L‐shaped slot has been introduced in the ground plane of antenna II to introduce a notch band in the frequency response of antenna III. Achieved measured 10 dB return loss bandwidth of antenna I and antenna II are 960 (3.3‐4.26 GHz) and 2890 MHz (2.77‐5.66 GHz), respectively. Antenna III offers measured 10 dB return loss bandwidth of 3220 MHz (2.32‐5.54 GHz) with a band notch from 2.39 to 2.99 GHz that isolates the 2.4 GHz WLAN and 3.5 GHz WiMAX band. Antenna II and antenna III have circular polarization property with measured axial ratio bandwidth of 440 MHz. The measured peak realized gain of antennas II and III is around 1.53‐2.9 dBi.     

Application of a defected ground structure and alternative transmission line for designing a quasi‐elliptic lowpass filter and reduction of insertion loss

A new defected ground structure (DGS) consisting of two square ring slots connects with a rectangular ring slot by two thin transverse slots under a microstrip line is proposed. In the frequency characteristics of proposed unit pattern, an attenuation zero is observed close to the attenuation pole. As a result, better transition sharpness, lower passband insertion loss and broader stopband are observed compares to dumbbell DGS. An equivalent lumped L‐C network is proposed to model the introduced DGS unit and corresponding L‐C parameters are extracted. Insertion loss is reduced by alternative transmission line on the top plane of the DGS unit. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Ultra‐wideband bandpass filter on coplanar waveguide: Proposal and implementation

In this paper, a novel ultra‐wideband (UWB: 3.1 ～ 10.6 GHz) bandpass filter on coplanar waveguide (CPW) is presented, designed and implemented. At first, an open‐ended nonuniform or multiple‐mode resonator with three distinctive sections is constructed and investigated toward generating the first three resonant modes occurring around the lower‐end, center, and higher‐end of the UWB band. Then, a CPW interdigital capacitor element with enlarged ground‐to‐ground distance is characterized to excite two additional resonant poles below and above the UWB's center. As a result, a five‐pole UWB bandpass filter with only one full‐wavelength is constituted. Its performance is studied on the basis of a simple cascaded transmission‐line network, whose parameters are extracted from our self‐calibrated method of moments. After the optimized results are confirmed by full‐wave simulation over the filter layout, a UWB filter sample is fabricated to demonstrate the actual UWB passband behavior with the 2.8–10.2 GHz bandwidth, where the insertion loss is less than 1.5 dB and variation in group delay is less than 0.33 ns. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Harmonic suppressed bandpass filter using composite right/left handed transmission line

A wideband composite right/left handed transmission line (CRLH TL) in conjunction with its corresponding equivalent circuit model is studied based on a cascaded complementary single split ring resonator (CCSSRR).The characterization is performed by theory analysis,circuit simulation,and full-wave electromagnetic (EM) simulation.The negative refractive index (NRI) and backward wave propagation performance of the CRLH TL are demonstrated.For application,a bandpass filter (BPF) with enhanced out-of-band selectivity and harmonic suppression operating at the wireless local area network (WLAN) band is designed,fabricated,and measured by combining the CRLH TL with a complementary electric inductive-capacitive resonator (CELC).Three CELC cells with wideband stopband performance in the conductor strip and ground plane,respectively,are utilized in terms of single negative permeability.The design concept has been verified by the measurement data.     

A computer‐aided approach for designing dielectric‐covered planar array antennas consisting of longitudinal slots

A straightforward design approach is proposed to design arrays of longitudinal slots covered with dielectric slabs. The design of the arrays is accomplished via linking the slotted array antennas fed by the waveguides to a corresponding array of the loaded slots cut in an infinite ground plane and covered with dielectric slab. In this regard, the Elliott's design equations are modified for the dielectric‐covered longitudinal slotted array antennas. The introduced design equations are employed to find the final dimensions of the slot antennas while the updated mutual admittances of the corresponding array of the loaded slots are used iteratively in the design equations. Employing the introduced design equations, a two by three slotted array antenna was designed, simulated and tested. The proposed design approach is verified by the simulation and the measurement results.     

High‐efficiency leaky‐wave antenna with continuous wide‐angle scanning using hybrid composite right/left handed structure

A hybrid composite right/left handed (CRLH) structure based leaky‐wave antenna with continuous wide beam scanning is proposed in this article. Six series‐wound periodic units, combining spoof surface plasmon polariton (SSPP) with CRLH, form the radiating portion of proposed antenna. The unit is connected to the ground with metal hole, which provides the equivalent parallel inductance, and the unit is separated from its adjacent unit at prescheduled intervals, which provides the equivalent series capacitance. Additionally, the unit operates at balanced state and the open stopband is obviously suppressed. Dispersion diagram is also used to analyze this continuous scanning. A prototype of proposed antenna is fabricated and measured. The main beam of the antenna scans continuously from ?70° to +40° in the range from 5.2 to 8.8 GHz. The antenna radiation efficiency reaches a maximum of 92% in the working band. Measurement results agree quite well with the simulation, which indicate this leaky wave antenna can find potential applications in communication systems and radars.     

Wideband cavity‐backed log‐periodic‐slot end‐fire antenna with vertical polarization for conformal application

A 6–18 GHz wideband cavity‐backed log‐periodic‐slot end‐fire antenna with vertical polarization for conformal application is presented. The log‐periodic folded slots and parasitic slots with 10 slot elements are applied to cover 6–18 GHz frequency band and the log‐periodic metallic cavity is placed under each slot element to keep wideband performance and prevent the effects of large metallic carrier on radiation patterns. The ground plane etched with log‐periodic slots is reversed and touched directly to the backed cavity and a dielectric cover is added to the antenna, to further improve the antenna performance. Meanwhile, a broadband microstrip‐coplanar waveguide transition is inserted in the antenna for measurements. With these designs, the proposed antenna shows good impedance matching (|S₁₁|<27 dB) and end‐fire gain (>4 dBi) performances in 6–18 GHz. The proposed antenna also keeps low‐profile and easy flush‐mounted characteristic which is suitable for conformal applications of high speed moving carriers.     

Wideband leaky‐wave antenna with consistent gain and wide beam scanning angle based on multilayered substrate integrated waveguide composite right/left‐handed transmission line

In this article, a wideband leaky‐wave antenna is designed for consistent gain and wide beam scanning angle by using the proposed multilayered substrate integrated waveguide (SIW) composite right/left‐handed transmission line (CRLH TL). The proposed SIW CRLH structure consists of two parts: an interdigital fingers slot of rotating 45° etched on the upper ground of the SIW, and a rotated parasitic patch beneath the slot. Due to the continuous phase constants change from negative to positive values of the proposed SIW‐CRLH under the balanced condition, the designed LWA can achieves a continuous beam‐scanning property from backward to forward over the operating frequency band. The designed antenna is fabricated and measured, the measured and simulated results are in good agreements with each other, indicating that the designed antenna obtains a measured continuous main beam scanning from backward ?78° to forward +76° over the frequency range from 7.7 to 12.8 GHz with a consistent gain of more than 9.5 dB. Besides, the designed antenna also exhibits a measured 3‐dB gain bandwidth of 45.1% with maximum gain of 15 dB. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:731–738, 2016.     

Bandwidth and gain‐enhanced composite right/left‐handed antenna for ultra‐wideband applications

A coplanar waveguide‐fed metamaterial antenna is presented for ultra‐wideband (UWB) applications. The proposed antenna is designed with single unit‐cell composite right/left‐handed transmission line (CRLH‐TL) loaded with a split‐ring resonator (SRR). The UWB characteristic is obtained by merging the zeroth‐order resonance of CRLH‐TL with two additional resonances due to the ground plane and SRR respectively. Subsequently, a partial reactive impedance surface is embedded on the rear side of the proposed antenna to enhance the realized gain without affecting the UWB response. The overall size of the antenna is 0.241λ_o x 0.267λ_o x 0.013λ_o (28.8 x 32 x 1.6 mm³), where λ_o is the free space wavelength at 2.51 GHz. The measured results indicate –10 dB fractional bandwidth of 139.19% (2.51‐14 GHz) with realized gains of 2.3, 4.6, and 6 dBi at the resonant frequencies 4, 7.84, and 10.29 GHz respectively. The measured peak realized gain is 6.6 dBi at 10.6 GHz. The radiation efficiency is above 63.85% for the entire UWB range with a peak value of 86.84%. A fairly stable group delay with variation within 1 ns is obtained throughout the operating frequency band. A good agreement has been observed between the measured and simulated results.     

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.     

A compact slot antenna configuration for ultrawideband (UWB) terminals and mobile phones

A novel technique to design a mobile phone antenna by using an ultrawideband (UWB) antenna configuration is proposed. The technique is validated with a novel printed slot antenna configuration. The slot is composed of a circle connected to a trapezoid and fed by means of a 50 Ω microstrip line connected to a patch with similar shape to the slot. An UWB antenna with size of 19 mm × 24 mm and measured ?10 dB bandwidth of 2.97‐11.32 GHz is developed based on the configuration. When the configuration is applied in a system circuit board of 60 mm × 115 mm to design a mobile phone antenna, the simulated ?6 dB bandwidths are 1.0‐1.2 GHz and 2.25‐15 GHz. To enhance antenna bandwidth, another slot with rectangular shape is etched in the ground plane, and the microstrip line is moved to the center of the circuit board and folded to distribute along the rectangular slot. The measured ?6 dB bandwidths of the mobile phone antenna are 0.69‐1.09, 1.68‐2.75, 3.45‐3.52, and 3.62‐15 GHz.     

A polarization reconfigurable CPW fed monopole antenna with L‐shaped parasitic element

A coplanar waveguide fed polarization reconfigurable monopole antenna is proposed in this letter. The proposed antenna consists of L‐shaped stubs placed on either side of a monopole, two p‐i‐n diodes and a slot in the ground plane. In the proposed antenna structure, the switching element is not directly connected to the feed line. Depending on the switching state of the p‐i‐n diodes, the antenna either radiates left/right circular polarization or linear polarization. To validate the proposed design, the antenna was fabricated and its performance was measured. Since the ground plane is electrically small, the effect of the cable and SMA connector on the performance of the antenna is also investigated. The measured impedance bandwidth is 66.78% (3.67 GHz to 7.35 GHz) and the axial ratio bandwidth is 13.62% (4.24‐4.86 GHz) for circular polarization and 23.61% (3.81‐4.83 GHz) impedance bandwidth for linear polarization.     

A wideband patch antenna with a pair of antisymmetric balun as differentially fed network

A novel singly differentially‐fed microstrip patch antenna (DFMA) is proposed, which is composed of a radiating patch, a differentially‐fed network with a twin antisymmetric miniaturized baluns and a ground plane for unidirectional radiation. In the differentially‐fed network, the signal is coupled to the two feedlines on both sides by the two miniaturized baluns. The radiating patch is excited by the coupling feed sheet located below the radiating patch, and the coupling feed sheet is connected to the upper end of the feedline. The lower end of the feedlines is connected to the ground plane, and there is a slot on the ground of the feeding network. Due to the existence of coupling feed sheet and slot, a second nonradiating resonant is achieved, and a wideband property is obtained. Finally, the prototype of the antenna is fabricated and studied experimentally. Simulated and measured results show that the impedance bandwidth of the antenna is 30.3% (1.71‐2.32 GHz) for S₁₁ < ?10 dB. Besides, a stable symmetric radiation pattern is obtained with gain around 9.6 dB and cross‐polarization less than ?21 dB, which demonstrates the designed antenna has the property of wideband, high gain and low cross polarization.     

Optically transparent broadband water antenna

In this article, we investigate an optically transparent broadband water antenna, which is composed of a cross‐shaped slot feeding structure and a thin layer of water supported by a transparent dielectric slab. This water antenna can be analyzed as an embedded stacked dielectric resonator (DR) antenna (DRA) mounted on a ground plane. Two distinct resonator modes—namely, DRA mode and dielectric‐loaded slot (DLS) mode—are excited to achieve a good impendence matching over a very wide frequency range. A prototype antenna is designed, fabricated, and measured. Measured results demonstrate that the designed water antenna exhibits a broad impedance bandwidth of about 37% from 1.07 to 1.56 GHz with antenna efficiency better than 65% and broadside radiation characteristics with low cross‐polarizations.     

New Compact antenna based on simplified CRLH‐TL for UWB wireless communication systems

This letter presents the experimental results of a novel planar antenna design which is synthesized using simplified composite left/right‐handed transmission‐line (SCRLH‐TL), which is a version of a conventional composite left/right handed‐transmission‐lines (CRLH‐TL), however, with the omission of shunt‐inductance in the unit‐cell. SCRLH‐TL exhibits a right‐handed response with nonlinear dispersion properties and a smooth Bloch‐impedance distribution. Arranged within the inner slot of the antenna are three smaller rectangular patch radiators. Each patch radiator is embedded with an E‐shaped notch, and located in the antenna conductor is a larger E‐shaped notch next to the 50‐Ω termination. The E‐shaped notches constitute SCRLH‐TL property. The gap in the slot between the smaller patches and the conductor next to the larger E‐shaped notch determines the impedance bandwidth of the antenna. The dimensions of the smaller patches determine the radiation characteristics of the antenna. The antenna is excited using a conductor‐backed coplanar waveguide transmission‐line. The antenna covers a bandwidth of 7.3 GHz between 0.7 GHz and 8GHz, which corresponds to 167.81%. In this band, the antenna resonates at 4.75 GHz and 7 GHz; the gain and radiation efficiency at these frequencies are 4 dBi—80% and 3.6 dBi—73%, respectively. The antenna's performance was validated through measurement. The antenna has dimensions of 0.0504λ₀ × 0.0462λ₀ × 0.0018λ₀, where λ₀ is free‐space wavelength at 700 MHz. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:217–225, 2016.     

Slot loading effect on impedance and radiation performance of high‐gain patch antenna under TM03‐mode operation

Based on antenna's impedance and radiation performance, the slot loading effect on the TM₀₃‐mode high‐gain square patch antenna is investigated in this paper. Three different slot configurations are loaded to the patch along the central line, which can reduce the sidelobe in the E‐plane. However, it is found that the H‐plane beamwidth, impedance bandwidth and radiation Q factor become significantly different in these cases. At first, broader H‐plane beamwidth, lower Q factor and wider impedance bandwidth can be obtained when only single slot is loaded in the center of the patch. In contrast, when two open slots are etched at two nonradiative edges of the patch, it will result in narrower H‐plane beamwidth, higher Q factor and narrower impedance bandwidth. Moreover, better balanced performance can be achieved by simultaneously loading the central and sided slots. For validation, three kinds of antenna prototypes are designed, fabricated, and measured. The measured and simulated results agree well with each other, which demonstrate that different impedance and radiation performance can be freely adjusted and achieved by using different slot configurations.     

Recessed ground microstrip line at 60 GHz and its application of band‐pass filter

The effect of finite‐size recessed ground on characteristic features of a microstrip transmission line is investigated and verified experimentally on alumina substrate of height 0.127 mm with ε_r = 9.8 at 60 GHz. A measured characteristic impedance of 238 Ω, effective dielectric constant of 3.09, and attenuation constant of 3.4 Np/m is achieved by using a recessed ground of dimensions (width × depth) 4.5 mm × 0.95 mm, below a 50‐Ω (on conventional ground plane) microstrip line. The effect of recessed ground on lumped equivalent circuit elements of microstrip line discontinuities including series‐gap, open‐end, and step discontinuities is also studied. To show the usefulness of recessed ground microstrip line, a prototype of fifth‐order Chebyshev‐type recessed ground end‐coupled band‐pass filter is designed and fabricated at 60 GHz. The filter exhibits measured insertion loss lower than 2.2 dB and return loss better than 13 dB over 3‐dB passband of 6% centered at 60 GHz. The measured results show good consistency with simulated results and confirm the usefulness of recessed ground plane microstrip line.     

A new broadband circularly polarized square‐slot antenna with low axial ratios

A new broadband circularly polarized (CP) square‐slot antenna with low axial ratios is proposed in this article. The antenna is comprised of an L‐shaped microstrip line with tapered section and a square‐slot ground plane with some stubs and slots, which are utilized as perturbations for the desirable antenna performance. By loading stubs and slots in the square‐slot ground plane, the 2‐dB axial ratio bandwidth (ARBW) and 10‐dB return loss bandwidth for the presented antenna can be markedly improved. The measured results show that its 2‐dB ARBW is 4.2 GHz (54.2% from 5.65 GHz to 9.85 GHz) and its 10‐dB return loss bandwidth is about 8.9 GHz (92.7% from 5.15 GHz to 14.05 GHz). The proposed antenna features compact structure and broad 2‐AR bandwidth which could completely cover the WLAN (5.725‐5.85 GHz) band. Therefore, the proposed antenna is suitable for circular polarization applications in C band.     

Wideband and spurious‐suppressed differential bandpass filter based on strip‐loaded slot‐line structure

In this article, a wideband and spurious‐suppressed differential bandpass filter based on strip‐loaded slot‐line structure is presented. By means of the differential microstrip‐slot‐line‐microstrip transition, the proposed filter has a wideband bandpass filtering response. Simultaneously, the utilization of the strip‐loaded slot‐line extends its upper stop‐band. The proposed bandpass filter has wider upper‐stopband, wideband bandpass response, and intrinsic high common‐mode (CM) suppression. To verify the design concept, one filter example has been designed, fabricated, and measured. It has a differential‐mode (DM) 3‐dB fractional bandwidth of 157% with a low 0.82 dB minimum insertion loss. What's more, it shows a very wide 20 dB DM stop‐band bandwidth of 6.5 f_0d. The experienced results are in good agreement with the theoretical and simulated results.