Search

THE rapid expansion in the millimeter-wave (mm-wave) frequency domain has completely changed the course of wireless communication. One of the most important steps to make smart cities, the Internet-of-Things (IoT), smart homes, and vehicular communication a reality is to use mm-wave frequencies for wireless applications. The rise in the number of wireless appliances has also led to a rise in data traffic [1]. The adoption of mm-wave frequencies enabled several gigahertz of bandwidth, allowing data rate and latency limits to be exceeded. The availability of a broad electromagnetic spectrum and frequency reusability are the most important characteristics of mm-wave deployment [2]. Although mm-wave systems have a shorter effective communication distance than microwave systems due to increased propagation loss, they are sufficient to cover small cells that span hundreds of meters [3]. So, the use of mm-wave systems in providing high-speed wireless connectivity in indoor venues, such as shopping centers, stadiums, and auditoriums, is very effective. To satisfy the network coverage in such scenarios, omnidirectional antennas for mm-wave frequencies are key. High gain antennas are also required to mitigate losses due to obstacles, including walls, buildings, and trees, which makes the mm-wave bands more beneficial as larger antenna arrays can be realized in small form factor.

A dual-port dual-sense wideband circularly- polarised (CP) printed slot antenna is proposed. The compact coplanar waveguide (CPW)-fed antenna is proposed for ambient energy harvesting applications. Two identical CPW feeds excite ±45° fan-shaped stubs in the elliptical slot, providing a wide bandwidth. By separating the ground plane and slot by two narrow strips, an isolation better than 19.4 dB between the ports is achieved. The measured impedance bandwidth is 850 MHz (2.08 GHz to 2.93 GHz) and the 3dB axial-ratio bandwidth is 870 MHz (2.04 GHz to 2.91 GHz).

In this letter, a compact beamsteering MIMO antenna is proposed for Directional Modulation (DM) applications. A generalization of the beamsteering principle is presented and by exploiting the antenna’s unidirectional beamsteering capability within the entire azimuth plane, the system realizes secure steerable transmissions in the direction of the legitimate receiver, with a low Bit Error Rate (BER) of 10^(-5), while a high error rate of 10^(-1) is seen outside the desired regions. Numerical and experimental verifications are carried out to validate the proposed concept and comparisons with circular arrays are conducted, revealing that the system achieves comparable performance but with up to 35% and 71% reduction in antenna diameter and profile, respectively. The method is proposed as a good candidate to enhance the security of small (IoT) devices.

Refined optimization of complex curve–linear-shaped radiators, such as traveling-wave Vivaldi antennas, can be achieved by considering simulated near fields to interpret in detail the structural influences of a design. The relationships between the space and time distributions of electromagnetic (EM) energy clusters and the geometric features are revealed with appropriate use of impulse response analysis combined with the multiple signal classification (MUSIC) algorithm. This article reports a deeper approach when applied to the adjustment of the geometric features of a traveling-wave antenna based on an analysis of near-field propagation features.

Energy harvesting is a potential source of power for integrating compact low-power and self-sustainable wireless devices in ambient backscatter communication systems and IoT networks. In this paper, an electrically small circularly polarised (CP) slot antenna for harvesting is proposed. The measured CP bandwidth for axial ratio values less than 3 dB is 990 MHz (1.7 GHz to 2.69 GHz), while the measured impedance bandwidth is 1,930 MHz (1.45 GHz to 3.38 GHz). The proposed structure can harvest energy from common radio frequency signal emitters operating in GSM 1800/1900, 3G/LTE 2100, 3G/LTE 2300, 4G/LTE 2500, and 2.4GHz Wi-Fi bands, which makes it an attractive design within energy harvesting technology.

A printed edge-fed counterpart of wire Bruce array antenna, with open-stopband mitigation at broadside, is presented. The proposed antenna comprises of 11 meandered unit-cells periodically modulated in congruence with wire Bruce array antenna's theory. To mitigate the effects of open-stopband, the horizontal and vertical lengths of unit-cell are adjusted along with the addition of an inward bent element allowing seamless scanning from backward to forward endfire region. The antenna has two distinct frequency scanning ranges between 18.0 GHz and to 37.20 GHz with Sidelobe level ≤ -10 dB. A dual Bruce array, using two-way Klopfenstein tapered feedline power divider, is then proposed to increase the peak realized gain to 18.61 dBi followed by a two-port solution to widen the scanning range of the antenna.

The article proposes methodology to use circularly polarized (CP) ultra-wideband (UWB) signals for simultaneous measurement of orientation and distance changes between transmitter and receiver. The proposed technique uses the rotational Doppler effect on CP pulsed communication. The amplitude of a CP signal is immune to polarization misalignment in the presence of rotation; however, the phase is subjected to a frequency-invariant shift proportional to the rotation angle. This significantly distorts the pulse shape in the time domain and can be used for the measurement of the rotated angle. By combining the technique with the well-known localization capability of UWB systems, one can precisely measure not only the distance but also the orientation. This is demonstrated by both numerical and experimental studies presented in this article.

With the increasing demand for global internet connectivity [1], services like INMARSAT’s Broadband Global Area Network (BGAN) are becoming more widely used. BGAN terminals are portable devices that can be plugged into a laptop or a network in a remote location and provide access to the internet via INMARSAT’s I-4 and the emerging I-6 geostationary satellites. BGAN terminals operate in the L-band with the receive band (Rx) of 1518-1559 MHz and the transmit band (Tx) of 1626.5-1675 MHz.

The paper proposes an Indoor Localization System (ILS) which uses only one fixed Base Station (BS) with simple non-reconfigurable antennas. The proposed algorithm measures Received Signal Strength (RSS) and maps it to the location in the room by estimating signal strength of a direct line of sight (LOS) signal and signal of the first order reflection from the wall. The algorithm is evaluated through both simulations and empirical measurements in a furnished open space office, sampling 21 different locations in the room. It is demonstrated the system can identify user’s real-time location with a maximum estimation error below 0.7 m for 80% confidence Cumulative Distribution Function (CDF) user level, demonstrating the ability to accurately estimate the receiver’s location within the room. The system is intended as a cost-efficient indoor localization technique, offering simplicity and easy integration with existing wireless communication systems. Unlike comparable single base station localization techniques, the proposed system does not require beam scanning, offering stable communication capacity while performing the localization process.

This paper investigates design considerations and challenges of integrating on-chip antennas in nanoscale CMOS technology at millimeter-wave (mm-wave) to achieve a compact front-end receiver for 5G communication systems. Solutions to overcome these challenges are offered and realized in digital 28-nm CMOS. A monolithic on-chip antenna is designed and optimized in the presence of rigorous metal density rules and other back-end-of-the-line (BEoL) challenges of the nanoscale technology. The proposed antenna structure further exploits ground metallization on a PCB board acting as a reflector to increase its radiation efficiency and power gain by 37.3% and 9.8 dB, respectively, while decreasing the silicon area up to 30% compared to the previous works. The antenna is directly matched to a two-stage low noise amplifier (LNA) in a synergetic way as to give rise to an active integrated antenna (AIA) in order to avoid additional matching or interconnect losses. The LNA is followed by a double-balanced folded Gilbert cell mixer, which produces a lower intermediate frequency (IF) such that no probing is required for measurements. The measured total gain of the AIA is 14 dBi. Its total core area is 0.83 mm2 while the total chip area, including the pad frame, is 1.55 \times 0.85 mm2. Science Foundation Ireland

A printed edge-fed counterpart of the wire Bruce array antenna, for frequency scanning applications, is presented in this paper. The unit-cell of the proposed antenna consists of bowtie and semi-circular elements to achieve wide bandwidth from below 22 GHz to above 38 GHz with open-stopband suppression. The open-stopband suppression enables a wide seamless scanning range from backward, through broadside, to forward endfire. A sidelobe threshold level of −10 dB is maintained to evaluate efficient scanning performance of the antenna. The antenna peak realized gain is 15.30 dBi, and, due to its compact size, has the ability to scan from −64° to 76°.

A calibration method for a high-resolution hybrid MIMO turntable radar imaging system is presented. A line of small metal balls is used in the calibration process to measure the position shift caused by undesired effects of the antennas. The unwanted effects in the near-field antenna response are analysed and significantly mitigated based on the referential features of the MIMO configuration.

A tri-band mm-wave planar Bruce array antenna for fifth generation communications (5G) is presented. The 16-element planar Bruce array antenna is simulated and fabricated on Rogers RT/Duroid 5880 substrate with thickness of 0.254 mm. For a compact and simple structure, the antenna has a highly directional fan-beam radiation pattern at broadside and peak realized gain of 14.0 dBi.

A calibration method for a high-resolution hybrid MIMO turntable radar imaging system is presented. A line of small metal spheres is employed as a test pattern in the calibration process to measure the position shift caused by undesired antenna effects. The unwanted effects in the antenna near-field responses are analysed, modelled and significantly mitigated based on the symmetry and differences in the responses of the MIMO configuration.

The aim of this work was to develop multimodal anthropomorphic breast phantoms suitable for evaluating the imaging performance of a recently-introduced Microwave Imaging (MWI) technique in comparison to the established diagnostic imaging modalities of Magnetic Resonance Imaging (MRI), Ultrasound (US), mammography and Computed Tomography (CT). MWI is an emerging technique with significant potential to supplement established imaging techniques to improve diagnostic confidence for breast cancer detection. To date, numerical simulations have been used to assess the different MWI scanning and image reconstruction algorithms in current use, while only a few clinical trials have been conducted. To bridge the gap between the numerical simulation environment and a more realistic diagnostic scenario, anthropomorphic phantoms which mimic breast tissues in terms of their heterogeneity, anatomy, morphology, and mechanical and dielectric characteristics, may be used. Key in this regard is achieving realism in the imaging appearance of the different healthy and pathologic tissue types for each of the modalities, taking into consideration the differing imaging and contrast mechanisms for each modality. Suitable phantoms can thus be used by radiologists to correlate image findings between the emerging MWI technique and the more familiar images generated by the conventional modalities. Two phantoms were developed in this study, representing difficult-to-image and easy-to-image patients: the former contained a complex boundary between the mammary fat and fibroglandular tissues, extracted from real patient MRI datasets, while the latter contained a simpler and less morphologically accurate interface. Both phantoms were otherwise identical, with tissue-mimicking materials (TMMs) developed to mimic skin, subcutaneous fat, fibroglandular tissue, tumor and pectoral muscle. The phantoms&rsquo, construction used non-toxic materials, and they were inexpensive and relatively easy to manufacture. Both phantoms were scanned using conventional modalities (MRI, US, mammography and CT) and a recently introduced MWI radar detection procedure called in-coherent Multiple Signal Classification (I-MUSIC). Clinically realistic artifact-free images of the anthropomorphic breast phantoms were obtained using the conventional imaging techniques as well as the emerging technique of MWI.

This communication proposes a simple, low-cost multimode patch antenna combining good multi-in multi-out (MIMO) performance with precise angle of arrival (AoA) estimation. The AoA is based on the monopulse antenna concept; however, unlike in radar applications, the necessity for complex circuitry is replaced by the intrinsic properties of even and odd resonant patch modes. This capability is advantageous for future “Internet of Things” antennas, embedded into low-cost and size-constrained devices. The envelope correlation coefficient, measured in an anechoic chamber, is below 1.5%, ensuring good MIMO performance. An exemplary addition to localization algorithm exploiting antenna properties is demonstrated.

A new directional modulation system that uses radiation pattern data for modulation encoding is proposed. The approach allows compact multiport antennas (e.g., MIMO-capable antennas) to be used for directional modulation, replacing extensive arrays. The modulation weighting coefficients are calculated with a fixed, antenna specific equation, thus reducing computational complexity. The solution is intended to enhance privacy in small, battery-operated wireless devices, required for ""Internet of Things"" applications.

The paper provides a first theoretical study on the effect of rotational Doppler on circularly polarized pulsed communication. Despite the circularly polarized communication being considered immune to signal fading due to rotary misalignment, such misalignment will cause a frequency-invariant phase-shift. This phase shift will significantly distort the shape of the time-domain pulse. The property can be used for integration of orientation sensing into well establish pulse-based localization. However, it has also the potential to distort communication for some pulse-modulated UWB systems.

A planar Vivaldi antenna structure with a core element is proposed for high gain. Techniques to achieve a significant gain improvement over the full Ka (24-40 GHz) band are implemented; including a frequency-independent excitation method, the introduction of logarithmic ripple on the lateral edges and enclosing the antenna in a dielectric material.

A back-to- back microstrip patch antenna with a switchable pattern is proposed for WLAN applications. The patch elements, printed on FR-4 substrates with a common ground plane, are switched with a single-pole double-throw PIN diode circuit. Switching the feed selects either of two identical radiation patterns in the opposing hemispheres for spatial diversity that would benefit a distributed network.

In this issue’s “Wireless Corner” column, the authors present a compact, low-cost antenna to be used in smart metering or smart grid devices in the lower ultrahighfrequency band. This low-frequency band has the advantage of providing larger coverage areas, but designing a compact antenna is challenging. The proposed antenna is a meander-line-folded monopole antenna that exhibits a stable radiation pattern and good radiation efficiency. The work shows how well the antenna performs despite material loading and when installed on a concrete wall.

Passive non-magnetic self-interference suppression circuits are currently used as first stages of complex full-duplex radio systems that allow simultaneous reception and transmission within the same channel. This paper introduces the upper efficiency limit for such circuitry. It is demonstrated that for these devices it is not feasible to have simultaneously high efficiency, good transmitter-to-receiver isolation and same propagation channel for transmission and reception. More specifically, the maximum efficiency for most typical case cannot exceed 50% if good isolation is obtained.

A dual-stub co-planar Vivaldi antenna with a parasitic element is presented. The dual stub is coupled between the parasitic element and two tapered slots. The parasitic element shape and size is optimised. The use of slits on the outer edge of the ground plane is shown to provide control of beamwidth and maximum gain. A bandpass filter is used for performance control and sub-harmonic suppression.

The paper proposes an electrically small pattern reconfigurable antenna, which allows flexible beamforming with the antenna diameter being λ/5. The antenna has 3 ports, each designed to radiate a different spherical mode. By applying appropriate phase shift the antenna allows to flexibly sweep its bi-directional radiation pattern across a 360° azimuth, while offering 5 dBi directivity.

A compact ultrawideband (UWB) circularly polarized (CP) slot antenna is proposed with a methodology for automated reoptimization for packaging with proprietary devices. The slot structure employs a dual-feed with an integrated compact UWB phase shifter. The design process involves an advanced optimization algorithm and demonstrates the use of spline curves for generation of CP signals. These allow easy optimization, while preserving phase coherency across a wideband. The prototyped antenna has a CP bandwidth of 54% (from 3.2 to 6.1 GHz).

A 433-MHz antenna is proposed for integration with the insole of footwear for a body-area network. The folded dipole design with an asymmetric groundplane radiates from its edges and considers the close proximity of the human foot and ground surfaces. It functions for different ground conductivity conditions and an on-body communication link with an inverted-F antenna in the upper body area was evaluated on a static and dynamic human subject. The antenna solution was compliant with specific absorption rate (SAR) requirements, remains matched and links with upper body nodes regardless of the body posture and node location.

An innovative method to measure the angular velocity using circularly polarized antennas is proposed. Due to the properties of circular polarization, the angular velocity is frequency modulated (FM) on a wireless carrier. This enables a low-cost precise continuous measurement of angular velocity using a standard FM demodulator. The hardware can be easily adapted for both high and low angular velocity values. The precise alignment angle between the antennas can be determined if the initial antenna orientation is known. The angular error is shown to be

A printed triangular monopole antenna with wideband circular polarization is presented. The wideband circular polarization is achieved by asymmetrical excitation of a triangular ground plane and planar triangular monopole. The combined radiation provides a wide axial-ratio bandwidth spanning from 1.42 to 2.7 GHz (62%). A parametric study of key geometric parameters is given for clear understanding of the radiation mechanism.

A 5G millimeter-wave radio over fibre optical fronthaul system based on optical heterodyning, utilising an externally injected gain switched distributed feedback laser, is successfully demonstrated. Five bands of UF-OFDM are transmitted over 25 km of fibre and a 28 GHz Vivaldi Antenna wireless link. Transmission performance below the 7% FEC limit is achieved with an aggregate total data rate of 4.56 Gb/s.

The paper demonstrates a technique to correct the axial ratio of dual-fed circularly-polarized antennas in the presence of strong coupling with surrounding components or asymmetrically reduced ground plane. It demonstrated - based on a standard GPS L1 patch antenna - that for certain situations a phase shift of up to 135° may be beneficial compared to the routinely used 90°, allowing for AR improvement from 7.8 dB (for 90°) to 2.1 dB (135°).

The usage of driving assistance systems that are based on V2X communication technologies as ITS-G5 are a promising technology to increase road safety as well as traffic efficiency. To allow for communication even in challenging propagation scenarios (such as busy urban intersection), we investigated a new concept for rooftop mounted beam-steerable vehicular antennas which is a 2-element monopole array (parallel and orthogonal to direction of travel) and a switchless reconfigurable antenna. It shows that the monopole array configurations give the best propagation results in any scenario and time step. However, the beams have to be steered dynamically to ensure the best possible communication.

This paper proposes an improved technique to calculate the Envelope Correlation Coefficient (ECC) by directly using the spherical mode spectrum of the antenna under test. The technique avoids errors due to numerical pattern integration and simplifies post-processing for near-field measurements. The technique is successfully tested on two different antenna types, in the total number of four MIMO configurations.

This paper proposes a new approach to reduce weight and complexity of VHF/UHF cubesat antennas by utilizing a dual band antenna, rather than standard two-antenna system routinely implemented in cubesats. Three systems are compared: A standard system with separate transmit/receive dipoles, a dual-band dipole for both transmit and receive and a dual-band monopole, which uses the body of 1U cubesat (10 × 10 × 10cm) as a “groundplane”. Additionally it is demonstrated that with appropriate feed the dipole might be used in monopole configuration in case of deployment system malfunction.

A new equivalent circuit based Wheeler Cap method to calculate MIMO efficiency is introduced. The method works without the necessity for interpolation by avoiding concur of resonating and cavity modes. The method is tested with a set of three differently correlated MIMO antennas. Results are compared with the recently proposed quality factor method for MIMO antennas and efficiency data from spherical near field measurements.

An adaptive radio system combining compact switchless reconfigurable antenna with Software Defined Radio is proposed. The system allows control of the direction of the transmitted signal solely by adjusting the baseband I and Q components of the modulated signal, while maintaining small antenna size through the use of compact multiport antenna. The system is demonstrated in a line-of-sight configuration with QPSK modulation. Experimental results demonstrate good received power and low error vector magnitude of the demodulated signals.