Dual-band Element Research Articles

Reconfigurable Dual-Band Capsule-Conformal Antenna Array for In-Body Bioelectronics

Wireless in-body bioelectronics offer powerful biosensing and therapeutic capabilities. Efficient and robust in-body antenna designs are required to ensure a reliable through-body link, increase data rates, and reduce power budgets. This study proposes and demonstrates a pattern- and frequency-reconfigurable capsule-conformal antenna array that responds to the challenges of next-generation in-body bioelectronics. The array comprises two mirrored dual-band elements operating at 434 MHz and 2.45 GHz ISM bands. Tissue-matched dielectric loading of the array improves the radiation efficiency and ensures quasi tissue-independent operation for both bands. Due to the full ground plane, the antenna is shielded from the capsule payload. The achieved efficiencies are compared to the fundamental limitations and closely approach them. The realized gains are −28.9 and −18.6 dBi at 434 MHz and 2.45 GHz, respectively, when the array is placed in the center of a ø100-mm diameter spherical phantom with muscle-equivalent properties. Using a single switch, the array can be reconfigured to adjust the angular position of the nulls in the radiation pattern in both bands thereby enabling synthesis of an effectively null-free omnidirectional pattern. The array prototypes are fabricated, and the impedance and far-field radiation patterns are characterized to validate the design in tissue-equivalent liquid phantoms.

Dual-band and dual circularly polarized sequential rotation antenna array for vehicle satellite communications

ABSTRACT A novel dual-band dual circularly polarized antenna array is proposed for vehicle satellite communication systems. The dual-band filtering element is presented, in which the dual-band characteristics are realized by vertically feeding method. The ring-shaped frequency selective configurations (RFSC) are added to the feeding network for the filtering function. The sequential rotation array is achieved by rotating four identical antenna elements around z-axis, where the phase difference of adjacent elements is 90° or −90° for the left-hand circular polarization and right-hand circular polarization, respectively. A decoupling approach is introduced to change the current paths on the surface of radiator with cutting orthogonal slots, which solves the problem of serious coupling between the different elements of the sequential rotation array. The prototype is fabricated and measured to verify the reliability of the simulations, and the simulations and measurements have reasonable consistency. The impedance bandwidths of the array are 7.26–7.46 GHz and 8.07–8.36 GHz, respectively. The port isolation of the array is greater than 30 dB in the two bands. The axial ratio (AR) bandwidths are 7.12–7.48 GHz and 8–8.36 GHz, respectively. The designed array has a promising application prospect for vehicles to satellite communications.

A compact low-noise frontend for interleaved Rx/Tx arrays at K-/Ka-Band

AbstractThis contribution deals with a frontend for interleaved receive (Rx)-/transmit (Tx)-integrated phased arrays at K-/Ka-band. The circuit is realized in printed circuit board technology and feeds dual-band Rx/Tx- and single-band Tx-antenna elements. The dual-band element feed is composed of a substrate-integrated waveguide (SIW) diplexer with low insertion loss, a low-noise amplifier (LNA), a bandpass filter, and several passive transitions. The compression properties of the LNA are identified through two-tone measurements. The results dictate the maximum allowable output power of the power amplifier. The single band feed consists of a SIW with several transitions. Simulation and measurement results of the individual components are presented. The frontend is assembled and measured. It exhibits an Rx noise figure of 2 dB, a Tx insertion loss of ~ 2.9 dB, and an Rx/Tx-isolation of 70 dB. The setup represents the unit cell of a full array and thus complies with the required half-wave spacing at both Rx and Tx.

A Dual-Band Circularly Polarized Elliptical Patch Reflectarray Antenna for High-Power Microwave Applications

The demand for multi-band high-power antennas, which have been rarely reported, becomes urgent in high-power microwave field. To meet the demand, a C/X dual-band high-power circularly polarized patch reflectarray antenna is proposed in this paper. Two main technologies are adopted to make the proposed antenna realize the high-power feature. Firstly, the elliptical patch with no abrupt structure is proposed to be the dual-band reflecting element to mitigate the electric field concentration. Secondly, the elliptical patches are proposed to be embedded into substrate to avoid the triple junction. The proposed dual-band reflecting element is designed by arranging two embedded elliptical patches with different sizes in a square lattice grid. The larger elliptical patch operates in C-band and the smaller one works in X-band. The elliptical patches are proposed to be rotated to realize continuous $360^{\mathrm {\circ }}$ phase response in both bands. By optimizing the thickness of substrate, the element spacing, and the size of the patches, the dual-band element shows good reflection amplitude and phase response and low mutual coupling performance. An antenna prototype with the aperture size of 345 mm $\times345$ mm is simulated and measured. The measured radiation results of the designed reflectarray antenna are in good agreement with simulations in both C-band and X-band. The measured gain of the antenna at 6.2 GHz is 24.6 dBi, and at 9.3 GHz is 27.8 dBi. Full-wave simulations show that the power capacity of the antenna at 6.2 GHz is about 10.2 MW, and at 9.3 GHz is about 3.9 MW in air condition. The low mutual coupling performance of the proposed antenna is verified both in element level and array level. All of the results show that the proposed antenna has the merits of high-power capacity, dual-band, and low mutual coupling.

A novel dual band patch design for electrical steerable reflectarray antennas

ABSTRACTReflectarray antennas do not necessarily exhibit a better antenna efficiency compared to ordinary reflector antennas. However, flat structure, multiband design capability, and specially, possibility of electrical beam scanning of this type of antenna are attractive to the antenna designers and researchers. By using elements with electrically tunable reflection phases, it is possible to design an electrically steerable beam reflectarray. In this paper, a novel dual band element is presented for which the reflection phase within each band can be controlled independently. Therefore, the reflectarray arranged by this element can perform the functions of two electrically steerable antennas simultaneously. An aperture coupled element and a miniaturized diplexer are used in the proposed structure. The reflection phase of the designed element can be controlled by changing the lengths of the output lines of the diplexer. It is possible to electrically change this line length using MEM switches. As a result, a dual band reflectarray with independent electrical beam scanning capabilities in each of its frequency bands is obtained.

Dual-Band Dual Circularly Polarized Antenna Array Using FSS-Integrated Polarization Rotation AMC Ground for Vehicle Satellite Communications

This paper presents a new dual-band dual circularly polarized (CP) high gain patch antenna array for vehicle satellite communications. The array consists of 16 linearly polarized dual-band elements backed with a new frequency-selective-surface (FSS)-integrated polarization rotation ground. The polarization rotation ground is located underneath the array, which not only acts as a reflector to increase the array boresight gain but also enables the array's dual CP radiation. The electromagnetic (EM) waves reflected by the ground retard either 90° or 270° with respect to the EM waves of the array directly radiated to the upper sphere at two frequency bands, leading to the dual-band dual CP radiation. This is totally different from many of the former counterparts which are based on either the perturbation on the stacked patch or external feeding network. Measured results show the −10-dB impedance bandwidth is from 7.8 to more than 8.5-GHz for X-band and from 14 to 15.3-GHz for Ku-band. The 3-dB axial ratio bandwidth is from 8.15 to 8.35-GHz for the lower band (right-hand CP) and from 14.2 to 14.8-GHz for the higher band (left-hand CP), respectively.

A High-Gain Dual-Band and Dual-Polarized Transmitarray Using Novel Loop Elements

A high-gain dual-band and dual-polarized transmitarray has been designed, fabricated, and measured for Ku-band ( ${\text{12.5/14.25}}$ GHz) satellite communications. The transmitarray unit cell is a combination of two novel loop elements, which are interlaced to form a unit cell for dual-band operation. The transmission response of both interlaced loop elements is almost independent at both frequencies. The three-layer dual-band element achieves $\text{300}^\circ$ phase range in both the frequency bands with less than 2 dB insertion loss. A dual-band transmitarray has been designed by using array theory in each frequency band independently. The measured radiation characteristics of the transmitarray are obtained through a planar near-field measurement setup. The dual-band transmitarray has achieved measured peak gains of 30.2 and 32.3 dBi with aperture efficiencies of 38% and 46% in downlink and uplink frequency bands, respectively.

X/Ku Dual-Band Single-Layer Reflectarray Antenna

In this letter, X/Ku dual-band single-layer reflectarray antenna is presented. The proposed reflectarray antenna operates in two separated bands with separate feeds. The reflectarray element is composed of a split ring with two phase delay lines and a phoenix patch. The split ring and phoenix patch are designed for operation at X- and Ku-bands, respectively. The split ring is selected as the lower frequency element because of the large enough internal space. The phase shift of these two elements does not depend on variation of external size, which provides a feasible method for designing dual-band elements. The lower band phase shift is obtained by changing the rotation angle of the phase delay lines. The movement of the inner loop of phoenix patch provides the required phase shift for the higher band. The proposed element realizes 360° phase shift range in both bands. The reflectarray is fabricated and measured to validate the design. The measured gains are 22.9 dBi at 8.5 GHz with aperture efficiency of 40%, and 28.8 dBi at 16 GHz with aperture efficiency of 44.8%. Besides, the 1 dB gain bandwidths are 20.5% (7.9–9.7 GHz) at lower band and 13.3% (14.7–16.8 GHz) at higher band.

A dual-band reconfigurable Yagi–Uda antenna with diverse radiation patterns

In this paper, a dual-band pattern reconfigurable antenna is proposed. The antenna comprises of a dual-band complementary split ring resonators (CSRRs) loaded dipole as the driven element and two copper strips with varying lengths as parasitic segments on both sides of the driven dipole. PIN diodes are used with the parasitic elements to control their electrical length. The CSRRs loading provide a lower order mode in addition to the reference dipole mode, while the parasitic elements along with the PIN diodes are capable of switching the omni-directional radiation of the dual-band driven element to nine different configurations of radiation patterns which include bi-directional end-fire, broadside, and uni-directional end-fire in both the operating bands. A prototype of the designed antenna together with the PIN diodes and DC bias lines is fabricated to validate the concept of dual-band radiation pattern diversity. The simulation and measurement results are in good agreement. The proposed antenna can be used in wireless access points for PCS and WLAN applications.

A Low-Mutual Coupling Dual-Band Dual-Reflectarray Antenna With the Potentiality of Arbitrary Polarizations

In this letter, a novel dual-layer dual-band reflectarray element is proposed, which consists of two different topologies: the cross-dipoles with fixed-size rings for Ku-band, and the round patches with variable-size rings for Ka-band. By optimizing the corresponding parameters, the dual-band reflectarray element can achieve not only sufficient phase variation with gentle slope, but also low mutual coupling. Furthermore, the dual-band operation can be obtained with arbitrary polarization due to the symmetric structure of the element. Afterward, a dual-reflectarray antenna with the proposed dual-band element is designed, fabricated, and measured for the first time. The results of measurement agree with that of simulation very well. The measured peak gains are 28.57 dBi at 35 GHz and 24.3 dBi at 16 GHz, respectively. Moreover, the cross polarizations at both bands are under –20 dB. The measured and simulated results indicate the good radiation performance of the antenna, which is a good candidate for dual-band monopulse antenna.

Single-Layer Dual-Band Reflectarray With Single Linear Polarization

This paper presents two kinds of novel elements to design single-layer dual-band reflectarray, with identical polarization in two closely separated bands. Several degrees of freedom of the proposed elements are tuned to match the desired phase compensations at two center frequencies simultaneously. It is noted that the dual-band characteristics are realized by a single integrated element rather than conventional dual-band elements with independent tunable components corresponding to two center frequencies. A 10 × 10-element offset-fed reflectarray operating at 9 and 13.5 GHz, with a ratio of the center frequencies 1.5, is designed and fabricated to validate the performance of the element, and the measured results show reasonable agreements with simulations. Due to the incompleteness of reflection phase distribution at the two center frequencies of the presented element, a complementary element with four resonances is introduced. Then, a 20 × 20-element reflectarray composed of both kinds of elements is also designed, and the measured results demonstrate a good availability of the proposed elements.

Dual‐band, dual‐circularly polarised antenna element

A dual-band element that operates with dual-circular polarisation in two separate industrial, scientific and medical bands is presented. The design that is based on concentric square slot/shorted-ring configuration is realisable in cost-effective printed circuit board technology making it attractive for low-cost personal communications devices. The antenna element provides a flexible topology that allows for convenient, independent control of the polarisation and impedance bandwidth of two distinct frequency bands with no fundamental limitation on the ratio between the high- and low-band frequency ranges. The topology of this element is presented, and the antenna concept is validated via simulated and measured results.

Dual-Band, Switched-Beam, Reconfigurable Antenna for WLAN Applications

The development of WLAN technology requires antennas with additional capabilities using simple and low-cost mechanisms. This letter presents a low-cost microstrip antenna integrated with simple p-i-n diodes as RF switches. The proposed antenna is capable of steering the beam in a dual-band mode: -19°, -59°, and 61° within the 2.45-GHz band, and 6°, -14°, and 16° within the 5.8-GHz band, which meets the IEEE 802.11a, b/g requirements. The antenna consists of three different dual-band elements, connected using an H-shaped transmission line at the radiating side. The novelty of this structure lies in the ground plane design. The H-shaped transmission line is used to integrate three different ground-plane structures.

A Ka-Band Dual-Frequency Radiator f>or Array Applications

In this letter, a dual-band antenna is proposed for use as an element in Tx/Rx Ka-band arrays. The antenna consists of a shorted annular patch (SAP) antenna integrated with a circular radiating waveguide. The SAP is fed with a stripline coupled through a slot, while for the waveguide, an E-plane stripline probe is used. This letter presents the design of the dual-band element, along with simulated and measured results. It will be shown that the proposed antenna possesses good electrical characteristics and that it can be realized using standard printed technologies.

Genetic Design of Dual-band, Switched-beam Dipole Arrays, with Elements Failure Correction, Retaining Constant Excitation Coefficients

Switched-beam dipole arrays (SBAs) are widely used in order to increase system performance in wireless communications. They represent an attractive alternative to fully adaptive arrays, due to lower deployment and maintenance costs. Dual-band operation and elements failure correction are dealt with in this paper, since they are considered to be key characteristics in modern systems, like WiFi/WiMAX, and remote base stations maintenance respectively. The focus of the presented work is on the preservation of constant excitation coefficients during dual-band operation (coefficients will change after a possible elements failure), but the possibility of retaining universal, constant excitations, even after element failures, is also examined (the term universal means that excitations are kept constant, regardless of element failure or frequency of operation). This is accomplished using a genetic algorithm (GA), and numerical results are presented which demonstrate the eligibility of the proposed technique.

A wide-band slot antenna design employing a fictitious short circuit concept

A wide-band slot antenna element is proposed as a building block for designing single- or multi-element wide-band or dual-band slot antennas. It is shown that a properly designed, off-centered, microstrip-fed, moderately wide slot antenna shows dual resonant behavior with similar radiation characteristics at both resonant frequencies and therefore can be used as a wide-band or dual-band element. This element shows bandwidth values up to 37%, if used in the wide-band mode. When used in the dual-band mode, frequency ratios up to 1.6 with bandwidths larger than 10% at both frequency bands can be achieved without putting any constraints on the impedance matching, cross polarization levels, or radiation patterns of the antenna. The proposed wide-band slot element can also be incorporated in a multi-element antenna topology resulting in a very wide-band antenna with a minimum number of elements. It is also shown that, by using only two of these elements in a parallel feed topology, an antenna with good radiation parameters over a 2.5:1 bandwidth ratio can be obtained.