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A low profile omnidirectional patch antenna with filtering response is investigated in this paper. The triangular patch antenna is axially fed by a probe at its center, exciting both its TM10 and TM11 modes. Comparing with the traditional circular patch, the triangular patch can not only minimize the patch size but also can generate a radiation null at the upper band edge. A ring slot and a series of shorting vias are introduced into the patch to merge the two modes, enhancing the bandwidth of the passband. The combination of the two elements simultaneously generates a radiation null at the lower band edge. Consequently, a compact filtering patch antenna with quasi-elliptic bandpass response is obtained without involving specific filtering circuits. The prototype with profile of $0.03 λ0 has a 10-dB impedance bandwidth of 8.9% (4.3-4.7 GHz), an average gain of 6.0 dBi within passband, an out-of-band suppression level of more than 30 dB within lower stopband (0-3.6 GHz), and more than 20 dB within upper stopband (5.1-6.3 GHz).

A low-profile crossed dipole antenna with wide bandwidth is investigated in this letter. The double-sided printing crossed dipoles consisting of four-stepped rectangular patches are fed by a pair of vacant-quarter printed rings, generating circularly polarized radiation. Two adjacent axial-ratio (AR) passbands with AR < 3 dB are generated due to the stepped rectangular patches, and they are merged together by adding an additional dielectric slab above the ground plane, resulting in a very wide AR bandwidth. Also, an irregular ground plane is used for the antenna, which can desirably enhance the boresight gain without involving high-profile cavity. To verify the feasibility of the proposed design, a prototype operating at C-band has been fabricated and measured. Reasonable agreement between the simulated and measured results is obtained. The prototype has a low profile of 0.13 λ0 (in terms of the center frequency of passband), a 10-dB impedance bandwidth of 66.9%, a 3-dB AR bandwidth of 55.1%, and an average gain of approximately 10.4 dBic within passband.

This paper presents a low-profile dual-band filtering antenna element and its application to long-term evolution (LTE) multiple-input multiple-output (MIMO) system for wireless customer premise equipments (CPEs). The proposed element consists of two separate U-shaped patches operating at different frequencies and a multistub microstrip feed line. For size miniaturization, the smaller U-shaped patch is embedded in the larger one. In addition, the multistub feed line can generate two controllable resonant modes as well as two nulls in realized gain at the boresight direction. Since the modes of the patches and multistub feed line can be controlled individually, the two operating bands can be tuned to desired frequencies. Also, the radiation nulls in boresight gain can be controlled, high roll-off rate and out-of-band radiation rejection levels are thus obtained. For demonstration, a low profile ( $0.009\lambda _{0})$ dual-band filtering antenna element operating at 1.9 and 2.6 GHz for TD-LTE applications (B39- and B38-bands) is implemented. Dual-band bandpass responses and four radiation nulls are observed in the experiment. Measured in-band gains are 6.7 and 7.3 dBi, whereas out-of-band gains are less than −10 dBi. Based on this element, a four-element MIMO antenna is further designed for LTE CPEs, where low profile and high integration of multiple components are required. A low mutual coupling of less than −19.2 dB and the low envelope correlation coefficients of better than 0.2 are obtained with a small edge-to-edge spacing of $0.15\lambda _{0}$ .

To introduce the experience of professor JIA Chun-sheng in treatment of primary and simple enuresis. Professor JIA Chun-sheng believes that most children with pediatric enuresis have the manifestation of both spleen deficiency and kidney deficiency, and it is rare that the patients have one of the two kinds of manifestation. The pathogenesis is as follows: kidney yang deficiency and depletion, steaming weakness, and caused by spleen qi deficiency qi deficiency and sinking, and the bladder failing to ensure retention results in failure of body fluids to be stored, so that enuresis is induced. On the basis of the above theory, professor JIA Chun-sheng proposed the treatment rules of “nourishing earth and banking up original qi, opening the orifices and awakening the spirit”, and selected Baihui ( GV 20), Qihai ( CV 6), Guānyuan ( CV 4), Zusānlľ ( ST 36), Sānyīnjiāo ( SP 6) and Taixī ( Kl 3) as the basic acupoints. Corresponding acupoints were increased or reduced according to different patterns, and good efficacy has been obtained.

Three S-containing highly porous metal–organic frameworks, namely, [((CH3)2NH2)Cd(MIPA)]n·xG (n = 4 (1), 2 (2), 1 (3) G = guest of DMF/DMA and H2O), featuring with high adsorption capacities and high selectivity for methylene blue (MB), were successfully assembled by subtly varying the synthesis conditions including solvents and temperatures. Compounds 1–3 crystallize in P21/c, I2/a, and R3m, respectively. The anionic frameworks of them are homologues and multiple crystal phases of the {[Cd(MIPA)]n}n−. Compounds 1 and 2 demonstrate the same 3,6-connected binodal net (42·6)(48·64·83), encapulating ca. 18 A × 18 A hexagonal channels and three other types of micropous channels. Compound 3 shows a different topology of a 4,4-connected binodal net (43·62·8), which has the highest crystalline density, highest solvent-accessible void, and accessible special surface area, as well as the highest symmetry among them. Circular channel, ca. 13 A × 13 A, and two other types of micropore channels are found in six dire...

This paper presents a dual-polarized patch antenna with quasi-elliptic bandpass responses. The proposed antenna is mainly composed of a feeding network, a driven patch, and a stacked patch, with its entire height being $0.09\lambda $ . The feeding network consists of two orthogonal H-shaped lines that coupled to the driven patch, each for one polarization. The elaborately-designed feeding lines not only ensure a sharp roll-off rate at the lower band edge, but also help to achieve low cross polarization and high isolation between two feeding ports. On the other hand, the upper stacked patch provides improved suppression levels at the upper stopband and also an enhanced gain within passband. Consequently, a compact dual-polarized antenna with satisfying filtering performance is obtained, without using extra filtering circuits. For demonstration, an antenna is designed to fit the specification of LTE band (2.49–2.69 GHz). The implemented antenna achieves an average a gain of 9 dBi, a cross-polarization ratio of 29 dB, an isolation of 35 dB within LTE band. The out-of-band suppression level is more than 40 dB within the 2G and 3G frequency bands from 1.71–2.17 GHz. It can be used as the antenna elements in multiband base station antenna arrays to reduce the mutual coupling.

This paper presents a novel dual-band base station antenna array using filtering antenna elements for size miniaturization. It consists of two $1 \times 6$ subarrays arranged side by side, which are designed for Digital Cellular System (DCS: 1710–1880 MHz) and Wideband Code Division Multiple Access (WCDMA: 1920–2170 MHz) applications. The two subarrays are composed of filtering antenna elements with high in-band radiation efficiency and out-of-band radiation rejection levels. The radiation of the DCS subarray is suppressed in the WCDMA band and vice versa. Mutual coupling between the two subarrays, therefore, can be suppressed and high isolation can be obtained with reduced subarray spacing. For demonstration, a dual-band filtering antenna array is designed and fabricated. The overall width of the array is only 206 mm, which is much narrower than that of typical industrial products ( $\sim 290$ mm). An isolation of 35 dB is obtained between the two subarrays without any decoupling network. The measured antenna gains are about 14.2 and 14.5 dBi for DCS and WCDMA bands, respectively, and the 3-dB beamwidths of the horizontal radiation patterns are 65° ± 5°. In addition, null filling below the main beam in the vertical radiation patterns is realized by elaborately designing a feed network to manipulate the output magnitude and phase of each array element. The proposed array is suitable for potential base station applications.

A rectangular filtering dielectric resonator antenna (FDRA) with low profile, wide bandwidth, and high gain is first investigated in this communication. It is fed by a microstrip-coupled slot from bottom, with open stub of the microstrip feedline elaborately designed to provide two radiation nulls at band edges for a filtering function. A separation is introduced in the slot to provide a good suppression level in lower stopband, while two parasitic strips are parallelly added to the microstrip feedline to offer good suppression in the upper stopband, and consequently, a compact FDRA with a quasi-elliptic bandpass response is obtained without involving specific filtering circuits. Based on the design, a modified DRA fed by a pair of separated slots is proposed to further enhance the gain by $\sim 4$ dB. A prototype operating at 5 GHz has been fabricated and measured for demonstration. The reflection coefficient, the radiation pattern, and the antenna gain are studied, and reasonable agreement between the measured and simulated results is observed. The prototype has a 10-dB impedance bandwidth of 20.3%, an average gain of 9.05 dBi within passband, and an out-of-band suppression level of more than 25 dB within a wide stopband.

Differential evolution (DE) is a simple yet powerful evolutionary algorithm for both single objective and multiobjective optimizations (MOPs). In nature, good parents are more likely to produce good offspring, because genes from good individuals propagate throughout the population. Inspired by this phenomenon, a two-step subpopulation strategy is proposed, in which individuals in the current population are sorted based on evaluation metrics, and are divided into superior and inferior subpopulations. The inferior subpopulation evolves to generate offspring. If the generated offspring has better evaluation metric values than individuals in the superior subpopulation, they will replace the latter and be used as vectors for mutation strategies. The proposed strategy is incorporated into several advanced DE variants for both single-objective optimization (SOP) and MOPs to verify its effectiveness. Experiments are conducted on 25 single objective, 5 bi-objective, and 4 tri-objective Deb, Thiele, Laumanns and Zitzler (DTLZ) benchmark problems. Results indicate that the proposed subpopulation strategy is capable of improving the performance of both single objective and multiobjective algorithms. The application of the proposed approach is demonstrated by solving a microwave circuit design problem with stringent requirements. The better performance achieved by the proposed approach in quality of solutions, convergence rate, and diversity is verified by the performance comparison with competitive optimization algorithms in the literature.

A low-profile, high-gain, and wideband metasurface (MS)-based filtering antenna with high selectivity is investigated in this communication. The planar MS consists of nonuniform metallic patch cells, and it is fed by two separated microstrip-coupled slots from the bottom. The separation between the two slots together with a shorting via is used to provide good filtering performance in the lower stopband, whereas the MS is elaborately designed to provide a sharp roll-off rate at upper band edge for the filtering function. The MS also simultaneously works as a high-efficient radiator, enhancing the impedance bandwidth and antenna gain of the feeding slots. To verify the design, a prototype operating at 5 GHz has been fabricated and measured. The reflection coefficient, radiation pattern, antenna gain, and efficiency are studied, and reasonable agreement between the measured and simulated results is observed. The prototype with dimensions of 1.3 $\lambda_{0}\times1.3\ \lambda_{0}\times0.06\ \lambda_{0}$ has a 10-dB impedance bandwidth of 28.4%, an average gain of 8.2 dBi within passband, and an out-of-band suppression level of more than 20 dB within a very wide stop-band.

There is an ever increasing demand for both function integration and improved performance in wireless communication devices. Therefore, the integration of efficient linearizing amplifying and bandpass filtering functions is proposed for the first time in this paper. A new Doherty amplifier configuration with attractive behaviors including bandpass filtering, wideband harmonic suppression, and enhanced efficiency, is presented. A component crucial to the successful implementation of the proposed configuration is the bandpass quadrature coupler with arbitrary coupling coefficient. Owing to the flexibility of a circular patch in locating the frequencies of different operational modes, it is thus possible to implement good bandpass characteristics. With the introduction of this new component, the Main and Auxiliary amplifiers can be driven more efficiently, resulting in both linearity and efficiency improvements. To verify the validity of the proposed configuration, a Doherty amplifier has been designed and fabricated. Its measured performance is compared with the conventional design and found to exhibit a bandpass filtering characteristics with a wide suppression band up to the third harmonic frequency. Meanwhile, the proposed amplifier achieves a measured power-added-efficiency improvement of 10% and an ACLR improvement better than 5.8 dB at the higher output power region.

A slot-fed rectangular dielectric resonator antenna (DRA) with a small ground plane is investigated. By combining the radiation patterns of different resonant modes, a uniform hemispherical radiation pattern can be obtained without requiring any other element. The difference between the maximum and minimum gains is less than 3 dB in the upper half space, and moreover, the front to back ratio is as high as 30 dB.

A wideband, low profile and high gain dielectric resonator antenna is investigated in this letter. The antenna consists of two dielectric layers with different permittivities and it is centrally fed by a rectangular slot. By placing the dielectric layer of low permittivity (2.2) below that of high permittivity (15), the antenna with low profile of $0.1{\lambda _0}$ can obtain a 10-dB impedance bandwidth of $\sim 40\% $ and an average gain of $\sim 9~\hbox{dBi}$ .

This paper presents a novel kind of patch antenna with high-selectivity filtering responses and high-gain radiation performance. The proposed antenna is mainly composed of a driven patch and a stacked patch, with its entire height being ${0.09\lambda }$ . Three shorting pins and a U-slot are embedded in the driven patch to enhance out-of-band suppression levels and skirt selectivity near the lower band-edge, whereas the stacked patch provides a sharp roll-off rate at the upper band-edge and also an enhanced gain. Without using extra filtering circuits, the proposed antenna exhibits a quasi-elliptic boresight gain response with three radiation nulls. For demonstration, an antenna is implemented covering the LTE band (2.3–2.7 GHz). The antenna achieves an average gain of 9.7 dBi within passband, and out-of-band suppression levels of more than 21 dB.

A compact unidirectional ring dielectric resonator (DR) antenna (DRA) with lateral radiation patterns is investigated for the first time. The unidirectional patterns are obtained by combining an equivalent horizontal magnetic dipole of the DR $\text{HEM}_{{11\delta} + {1}}$ mode and a vertical electric dipole located at the center of the DR. A wideband version of the design is also investigated, in which the higher-order DR $\text {HEM}_{{11\delta} + {2}}$ mode is excited and merged with a slot mode to give a wideband magnetic dipole. The wideband electric dipole is obtained by making use of the parasitic effect of the DR. To demonstrate the idea, the original and wideband DRAs were designed in WLAN (2.40–2.48 GHz) and WiMax (3.4–3.7 GHz) bands, respectively. Their prototypes were fabricated and measured, and reasonable agreement between the measured and simulated results was obtained. In each design, the measured and simulated front-to-back radiation ratios are both over 15 dB, with measured and simulated 3-dB beamwidths of at least 117°.

In this letter, a compact quadrature coupler based on a circular sector patch element with metallic posts loading along the edge, is proposed to provide a wide range of coupling coefficients, which is difficult to achieve using existing topologies. Instead, this can be achieved by simply adjusting the ratio of the radii of circular sector patch resulting in a simple design procedure. To verify the proposed configuration, a series of quadrature couplers operating at 30 GHz with different coupling coefficients are designed, fabricated and measured. Excellent performance is achieved with a significant size reduction of 84.1% compared to the miniaturized substrate integrated waveguide cruciform directional coupler reported in literature.

This paper presents a simple design method for dual-band patch antenna array using a novel feeding scheme to integrate bandpass response. The array has no filtering circuits but reveal high filtering performance. Only a microstrip transmission feed line is coupled to radiating patches and specific coupling regions are employed to obtain the desired current distribution on the radiating patches. In the operating band, the induced currents on the patches are in phase, resulting in high boresight gain. At the out-of-band frequencies, the patches are not excited or the induced currents on them are 180° out-of-phase, resulting in radiation suppression. Using this method, out-of-band radiation can be suppressed without degrading the in-band performance. For demonstration, a dual-band patch array is implemented. Dual-band bandpass response is observed and in-band gains are 12.6 / 13.0 dBi, whereas out-of-band suppression is more than 15 dB.

A wideband low-profile omnidirectional circularly polarized (CP) patch antenna is proposed and investigated in this communication. The design utilizes two monopolar modes of a circular patch which connects to a modified ground plane by a set of conductive vias, to achieve wide-band impedance matching. The curved branches introduced at the edge of circular ground plane excite a degenerate mode and create CP fields. To verify the design, a prototype operating at 2.4 GHz-WLAN band has been fabricated and measured. Measured reflection coefficient, axial ratio (AR), radiation pattern, and antenna gain agree well with simulation results. The proposed prototype has a low profile of 0.024 λ0, a 10-dB impedance bandwidth of 19.8% and a 3-dB AR bandwidth of 19.3%. To further characterize the design concept, a parametric study of the proposed antenna is carried out using HFSS, and general design guidelines are provided.

The quasi-isotropic dielectric resonator antenna (DRA) is investigated for the first time. It uses a small ground plane which also serves as an electric dipole. The electric dipole combines with the equivalent magnetic dipole of the DRA to generate quasi-isotropic fields. A choke (balun) is connected to the outer conductor of the coaxial cable to suppress stray radiation. ANSYS HFSS was used to simulate the antenna, and a prototype operating at 2.4-GHz WLAN band was fabricated to verify the simulation. Results show that the difference between the measured maximum and minimum radiation power densities is 5.6 dB over the entire pseudo spherical radiating surface. By using a narrower ground plane and a higher dielectric constant, the gain difference can be reduced to 3.4 dB, approaching the theoretical limit of 3 dB.

Singly-fed 45 ° slant-polarized (SP) omnidirectional antennas without complex feed network are proposed in this letter. The antennas consist of a feeding probe that radiates monopolar omnidirectional vertically polarized (VP) fields and parasitic metallic/dielectric parallelepiped elements that convert omnidirectional VP fields into 45 ° SP fields. Two prototypes with metallic and dielectric parallelepipeds operating in C-band were designed. The bandwidths of the SP metallic and dielectric antennas are given by 15.1% and 31.9%, respectively.

Design of a dual-band omnidirectional cylindrical dielectric resonator antenna (DRA) using TM011 and TM012 modes is investigated in this letter. The limit of frequency ratio is found, and formulas that determine the dimensions of the DRA from two given frequencies have been provided. To verify the theory, a dual-band omnidirectional cylindrical DRA operating in 3.5-GHz WiMAX and 5.8-GHz WLAN bands is designed and tested. The reflection coefficient, radiation pattern, and antenna gain are studied, and reasonable agreement between measurement and theory is observed.

A circularly polarized (CP) dielectric resonator antenna (DRA) loaded with a modified circular patch is proposed for dual-band applications. The antenna is centrally fed by a probe, giving omnidirectional patterns with different senses of circular polarization in two bands. It is observed that the lower and upper bands are controlled by the patch and dielectric resonator (DR), respectively, making design of the dual-band antenna very easy. For demonstration, a prototype has been designed, fabricated, and measured. The antenna features 10-dB impedance bandwidths of 2.64% and 18.03% and 3-dB axial-ratio (AR) bandwidths of 3.16% and 5.06% in lower and upper frequency bands, respectively.

This paper presents, for the first time, a patch coupler configuration that can be designed with an arbitrary coupling coefficient and phase difference at the output ports. Four circular sector patches are combined to form the patch coupler resulting in ease of design and fabrication. To demonstrate and verify this, a patch quadrature coupler configuration is proposed to realize a wide range of coupling coefficients by adjusting the radii of each quadrant. To extend this concept of an arbitrary coupling coefficient for 180 $^{\circ}$ patch couplers, different patterns are etched underneath the circular patch to realize the required power division ratio while maintaining good impedance matching and desired phase characteristics at the input/output ports. Finally, a circular patch coupler is demonstrated to exhibit an arbitrary phase difference between output ports maintaining an equal power division.

Two planar metallic patch (MP) antennas with low profiles are investigated and compared in this paper. The MP of each antenna consists of metallic patch cells and it is centrally fed by a rectangular slot. Two modes with close resonance frequencies are excited, providing a quite wide bandwidth. The antenna principle is explained clearly through a parametric study. Simulated and measured results show that the MP antennas with profile of 0.06λ0 can obtain a 10 dB impedance bandwidth of ~32% and an average gain of ~10 dBi.

The dual-function glass dielectric resonator antenna (DRA) that simultaneously serves as a light cover is investigated for the first time. This paper is the first part, which demonstrates the idea using omnidirectional hollow rectangular glass DRAs. Both linearly polarized (LP) and circularly polarized (CP) designs are given. The glass DRA can generate CP fields by adding metallic patches onto its side walls, with a 3-dB axial ratio bandwidth of ~ 7%. To obtain an entirely light-transmissible CP glass DRA, conducting indium tin oxide (ITO) patches are used in place of the metallic patches. For each of the LP and CP designs, powered light emitting diodes (LEDs) are placed inside the hollow region of the glass DRA to serve as the light source. It is shown that practically the lighting and antenna parts do not interfere with each other. The reflection coefficient, axial ratio (CP designs only), radiation patterns, and antenna gains of the proposed LP and CP antennas are studied, and good agreement between measured and simulated results is observed.

A wideband circularly polarized (CP) antenna with a conical radiation pattern is investigated. It consists of a feeding probe and parasitic dielectric parallelepiped elements that surround the probe. Since the structure of the antenna looks like a bird nest, it is named as bird-nest antenna. The probe, which protrudes from a circular ground plane, operates in its fundamental monopole mode that generates omnidirectional linearly polarized (LP) fields. The dielectric parallelepipeds constitute a wave polarizer that converts omnidirectional LP fields of the probe into omnidirectional CP fields. To verify the design, a prototype operating in C band was fabricated and measured. The reflection coefficient, axial ratio (AR), radiation pattern, and antenna gain are studied, and reasonable agreement between the measured and simulated results is observed. The prototype has a 10-dB impedance bandwidth of 41.0% and a 3-dB AR bandwidth of as wide as 54.9%. A parametric study was carried out to characterize the proposed antenna. Also, a design guideline is given to facilitate designs of the antenna.

This paper is the second part of our study that investigates using glass dielectric resonator antennas (DRAs) as light covers. To begin, designs of dual-band hemispherical DRAs are investigated for the first time. Both broadside and omnidirectional dual-band DRAs are included in the study. The former makes use of the broadside TE111 and TE112 modes of a hollow hemispherical DRA, whereas the latter utilizes the endfire TM101 and TM103 modes of a solid hemispherical DRA. New design formulas that determine the radii of the two dual-band hemispherical DRAs are found. To demonstrate the usefulness of the formulas, two dual-band hemispherical DRAs for WLAN/WiMAX applications were designed and fabricated using K9 glass. ANSYS HFSS was used to simulate the DRAs, and the results agree reasonably well with our measurements. Results of using the DRAs as light covers are reported.

This paper presents a new miniaturized dual-band base-station array using a novel filtering antenna with high in-band radiation efficiency and out-of-band radiation level. It consists of two 1 × 6 sub-arrays arranged side by side, which are designed for DCS (1710–1880 MHz) and WCDMA (1920–2170 MHz) applications. Since the filtering antenna elements feature sharp frequency selectivity, the radiation of the DCS sub-array is suppressed at the WCDMA band and vice versa. Thus, mutual coupling between the two sub-arrays can be suppressed, and high isolation can be obtained with reduced sub-array spacing. For demonstration, a dual-band filtering antenna array is designed and fabricated.

A low profile, high gain and wideband parasitic patch antenna with filtering response is investigated in this paper. The parasitic patches are fed by two separated microstrip-coupled slots from the bottom. Good filtering performance in the lower stopband is achieved by the separation between the two slots together with a shorting via, whereas a sharp roll-off rate at upper band edge for the filtering function is produced by the elaborately designed parasitic patches. The parasitic patches also simultaneously work as a high efficient radiator, enhancing the impedance bandwidth and antenna gain of the feeding slots. The prototype with profile of 0.06 λ0 has a 10-dB impedance bandwidth of 30.0%, an average gain of 8.9 dBi within passband, and an out-of-band suppression level of more than 22 dB within ∼0–3.9 GHz and more than 30 dB within 6.4–9.7 GHz.

In this paper, two kinds of filtering patch antennas without using extra filtering circuits are introduced, one for single-polarization and the other one for dual-polarization. The single-polarized antenna is composed of a stacked patch and a driven patch embedded with three shorting pins and a U-slot. A quasi-elliptic bandpass response with three radiation nulls generated by the stacked patch, shorting pins and U-slot in the boresight gain is achieved. The dual-polarized antenna consists of two orthogonal H-shaped feeding lines, a driven patch and a stacked patch. Also, a quasi-elliptic bandpass response with two radiation nulls provided by H-shaped line and stacked patch is achieved for the dual-polarized filtering antenna.

A wideband omnidirectional circularly polarized (CP) rectangular dielectric resonator antenna (DRA) is investigated in this communication. An inclined slot, loaded by a parasitic conducting strip, is fabricated on each sidewall of the DRA. The parasitic strips can excite a CP mode, which combines with the CP DRA mode to provide a wideband axial-ratio (AR) bandwidth of more than 25%. To fully utilize the increased AR bandwidth, the impedance bandwidth is also broadened by introducing a hollow cylinder at the center of the DRA. The hollow region is also used to accommodate a coaxial probe that excites the antenna. The reflection coefficient, AR, radiation pattern, antenna gain, and efficiency of the antenna are studied, and reasonable agreement between the measured and simulated results is observed. A parametric study was also carried out to characterize the proposed wideband CP omnidirectional antenna.

In this study, flexible and uniform multiwall carbon nanotube embedded polydimethylsiloxane (PDMS) sheets were prepared using a vacuum filtration and transfer process. The resistance of the sheets and microstructures were investigated for the fabrication of ideal probe-fed and microstrip-fed patch antennas. Simulation results showed that the resonance and gain of an antenna were affected by the conductivity of the patch significantly. The return loss and gain are acceptable when a conductivity of 10 5 S/m is used. The stretchability test indicated that a gold-coated sheet was more stable than a pristine sheet. Its resistance has a change of 0.5% only, with a displacement of 2500 μm. The frequency-tuning capability was demonstrated using an air inflatable microstrip-fed patch antenna. The working frequency can be tuned by 6.5% with a displacement of 1500 μm, which was higher than that of previously reported MEMS bridge and electrostatic force tunable antennas. This is the first time that a frequency tunable antenna fabricated by PDMS/carbon nanotube is reported. The optimization methods for this type of antenna are discussed and some potential applications such as remote wireless pressure sensors are proposed.

The rectangular dielectric resonator antenna (DRA) centrally fed by a probe is investigated. Its operating mode is analogous to the TM011 mode of a cylindrical DRA. The DRA radiates like an electric monopole, generating omnidirectional linearly polarized (LP) fields. Based on this LP design, a novel omnidirectional circularly polarized (CP) DRA is studied for the first time. Slots are introduced to the sidewalls of the DRA, exciting a degenerate mode for the generation of CP fields. To demonstrate the idea, an omnidirectional CP DRA was designed for WLAN (2.4-2.48 GHz) applications. The reflection coefficient, axial ratio (AR), radiation pattern, and antenna gain are studied, and reasonable agreement between the measured and simulated results is observed.

At millimeter-wave (mm-wave) frequencies, the size of the dielectric resonator antenna (DRA) may be too small to fabricate precisely. To relax the precision problem of fabrication, it is proposed to obtain a larger DRA by designing it with its higher-order mode. In this paper, the rectangular mm-wave slot-fed DRA excited in a higher-order mode is investigated systematically. It is found that when the slot is centrally located beneath the DRA, a TEpqr mode of the DRA can be excited only when all of the indices p, q, r are odd numbers. The aspect ratio of the DRA that gives a single (higher-order) TE11ry -mode operation is found. Like the fundamental TE111 mode, the higher-order TE11r modes have broadside radiation patterns. To validate our results, two DRAs were designed to operate in the higher-order TE115 and TE119 modes. In each case, the reflection coefficient, radiation pattern, and antenna gain are studied, and reasonable agreement between the measured and simulated results is observed. The effect of fabrication error on the frequency shift of the DRA was also studied. A design rule for minimizing the frequency shift is suggested. The results should be useful for practical designs of the mm-wave DRA.

For the first time, the dielectric waveguide model (DWM) is used to calculate the resonance frequency of the hollow rectangular dielectric resonator antenna (DRA). In the analysis, the transverse transmission line technique is used along with the effective dielectric constant method to obtain characteristic equations of the hollow DRA. Good agreement between the calculation, measurement, and HFSS simulation is observed. The theory was used to facilitate the design of a strip-fed circularly polarized (CP) hollow DRA. It provides a wide 3-dB axial-ratio bandwidth of 12.4%, which is ~ 3 times of that of the solid CP DRA.

A wideband circularly polarized (CP) trapezoidal dielectric resonator antenna (DRA) is investigated in this letter. The DRA is simply excited by a single 45° inclined slot fed by a microstrip feed line. It is found that the 3-dB axial ratio (AR) bandwidth of the proposed antenna can be as wide as 21.5%. The antenna gain varies between 5.28 and 8.40 dBi across the antenna passband (3.11-3.86 GHz). This letter also presents a modified trapezoidal DRA that has a notch at its top. The modified version improves the impedance match, as the AR and gain remain almost unchanged. The reflection coefficient, AR, radiation pattern, and antenna gain of each proposed configuration are studied, and reasonable agreement between the measured and simulated results is observed.

In this paper, a compact differential-fed antenna with filtering responses is proposed. The antenna is composed of two radiating patches and a differential-fed circuit embedded with two u-shape slots which generate two notches. The stacked patch is employed to further improve the impedance bandwidth to fit the LTE communication application. The proposed antenna achieves the 18% impedance bandwidth. The average gain within the bandwidth is 9.5 dBi with less than 0.5 dB variation. The cross polarization ratio is less than 30dB. Out of the operating band, the gain drops sharply, exhibiting a bandpass response.

We would like to correct the values listed in Table I and two typos in Fig. 14 in the communication [1] as follows.

Antennas that are fabricated by traditional processes are hard to be reconfigured to a curved shape after fabrication. While, foldable and stretchable antennas are attractive for applications now, such as sensors and can be integrated into textiles and clothes for wearable electronics and out-of-plane designs. In this research, we used polydimethylsiloxane, carbon nanotubes, gold and some secondary raw materials to design and fabricate two types of frequency-tunable soft composite antennas for wireless sensing, utilizing vacuum filtration and transfer process. And after fabrication, we characterized the frequency properties for both of them.

A compact wideband circularly polarized rectangular dielectric resonator antenna (DRA) with dual underlaid hybrid couplers is investigated for the first time.As no extra footprint is needed for the couplers, the proposed antenna is very compact. The dual hybrid couplers are connected to generate four quadrature signals that are fed to four sequentially rotated excitation strips stuck on the four side walls of the DRA. It is found that the 3-dB axial-ratio bandwidth of the proposed antenna can be as wide as 27.7%. The reflection coefficient, radiation pattern, and antenna gain of the proposed antenna are studied, and reasonable agreement between the measured and simulated results is observed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2789–2791, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25591