This paper introduces a new design for a wireless body area network (WBAN) antenna employed as a body central antenna. The role of this central antenna is to receive the data from the on-body and in-body biosensors working at 2.45 GHz and transmit it off-body to a worldwide interoperability for microwave access (WiMax) antenna at 5.8 GHz. The central antenna is a composite structure constructed from a spiral antenna attached to the tip of a monopole. It operates in two modes, on-body mode at 2.45 GHz to receive data from the on-body and in-body biosensors and off-body mode at 5.8 GHz to transmit data to WiMax. The antenna has a compact size and lightweight with total dimensions of 12 × 12 × 8.5 mm and a 10.8% bandwidth (BW) at 2.45 GHz to communicate with in-and on-body biosensors, and wider BW of 23% at 5.8 GHz to allow for high data transmission rates to the WiMax. The radiation pattern is broadside circular symmetric at the lower operating frequency and balloon-like with high gain at the upper-frequency band. The gain at the lower-and upper-frequency bands is 4.9 and 7.1 dBi, respectively. A prototype is fabricated for the monopole/spiral body central antenna. Experimental measurements for the reflection coefficient and the radiation patterns are performed showing good agreement with the simulation results.

The present paper introduces a design methodology to extend the operation of a microstrip patch antenna to operate efficiently at multiple higher-order resonances. This method depends on the geometrical modification of the antenna structure by adding well-designed inductively-loaded and capacitively-coupled elements to the primary patch so that it can efficiently radiate at the desired higher frequency bands. It is explained quantitatively how to use the geometrical parameters of the inductively and capacitively coupled elements for accurate tuning of the multiple resonant frequencies of the antenna. The proposed method is applied to modify a primary hexagonal patch antenna (designed to principally radiate at 28 GHz as its first-order resonance) so as to operate at additional higher frequency bands around 43, 52, and 57 GHz. Also, an alternative design is provided for a quad-band printed antenna of composite patch structure that operates in the same millimetric-wave (mm-wave) bands, 28, 43, 52, and 57 GHz with high radiation efficiency, excellent impedance matching, and satisfactory values of the antenna gain. The corresponding frequency bands are, respectively, (27.7-28.3 GHz), (42.7-43.3 GHz), (51.2-53.0 GHz), and (55.7-57.5 GHz). The dimensions of the area occupied by the primary patch and the parasitic elements are 5.2 × 3.3 mm . The two antennas are fabricated for experimental assessment of their performance including the impedance matching and radiation patterns. It is shown that the experimental measurements come in agreement with the simulation results over all the four operational mm-wave frequency bands. One of the advantages of the proposed method is that it can be applied to patch antennas of arbitrary shapes and is not restricted to hexagonal patch antennas. Furthermore, this method is not restricted by extending the operation of the antenna to radiate at four frequency bands. It is capable of adding any desired number of frequency bands so that the antenna can operate at five or, even, more bands.INDEX TERMS MIMO, multi-band antenna, Patch antenna, 5G mobile communications

This paper proposes a novel design of a software-defined matched filter (MF) for digital receivers of synthetic aperture radar (SAR). The block diagram of the proposed receiver is described in detail. The purpose of this filter is to produce a SAR pulse with higher compression ratio (CR) and lower side lobe level (SLL) than that produced by the conventional MF. The proposed design is based on the idea of time windowing of the SAR pulse to construct the transfer function of the receiver filter. The shape of the proposed time-domain window is optimized to achieve the filter design goals including the minimization of the SLL and the realization of the target value of the CR. The transmitted SAR pulse is, first, subjected to linear frequency modulation and then subjected to the optimized window. The width (time duration) of the proposed window is divided into equal time intervals. The proposed time-domain window is constructed as a sequential continuous piecewise linear segments. The instantaneous value of the time-domain window at the start of each time interval is optimized so as to achieve the optimization goals. The width of the time-domain window is shown to be proportional to the width of the compressed pulse after optimization. The number of the time intervals into which the time duration of the window is divided is shown to have a significant effect on the optimization results. The particle swarm optimization (PSO) technique is then applied to get the window shape that minimizes the SLL for a specific predetermined value of the pulse CR. It is shown that the iterations of the PSO are fastly convergent and that the applied algorithm is computationally efficient. Also, it is shown that the desired value of the pulse CR is achieved with accuracy of 100%. Moreover, the achieved SLLs are about − $$65\,\mathrm{dB}$$ 65 dB , $$- 90\,\mathrm{dB}$$ - 90 dB , $$- 114\,\mathrm{dB}$$ - 114 dB , and $$- 133\,\mathrm{dB}$$ - 133 dB for pulse CR of 5, 3, 2, and 1.5, respectively. Finally, for practical implementation of the introduced SAR pulse processing technique, the proposed optimized window is placed as a building block in a software-defined receiver of the SAR system.

In this paper, a modified rhombic‐shaped wide‐flare two‐arm antenna is proposed for super‐wideband applications of the next generations of mobile technologies. To enhance antenna input impedance and to improve its performance, the copper arms are lithographed on a dielectric substrate with multilayers and fed through a wideband balun that is designed to feed the balanced two‐arm antenna through the conventional (unbalanced) coaxial line. The proposed antenna is fabricated for experimental validation of the simulation results. It is shown through electromagnetic simulation as well as experimental measurements that the proposed antenna is operational in the range of frequencies (). Parametric study is performed to obtain the optimum design of the proposed antenna. The distributions of the surface current on the antenna arms at different frequencies are presented and discussed for more understanding of the antenna operation over the entire frequency band. It is shown that the antenna has a radiation efficiency of greater than 96%, percentage bandwidth of 164%, ratio bandwidth of 10, bandwidth‐to‐dimension ratio of 1360, and maximum gain that exceeds .

A novel design of dual-band circularly polarized patch antenna is proposed for millimeterwave applications of the future generations of mobile communication handsets. The antenna structure is composed of a primary circular patch and four parasitic printed elements. The circular patch has two notches on its perimeter. The primary circular patch is designed to operate at 38 GHz as its first-order resonance with perfect impedance matching over the frequency band (37 -38.5 GHz). Four parasitic elements with Yshaped slots are capacitively coupled to the primary patch to get it operational at an additional higher frequency with perfect impedance matching over a wideband (48.2 -50.1 GHz). Defects in the ground plane are made as two square slots. The notches on the circumference of the circular patch and the square slots in the ground plane are aligned to a diagonal that makes 45° with the axis of symmetry of the feeding line. The width of each slot and the diagonal distance between them are the design parameters that can be set to produce circular polarization with satisfactory axial ratio (AR). The outline of the composite planar antenna structure has a square shape so as not to degrade the circular polarization. Also, to satisfy the impedance matching without disturbing the circular polarization, the primary patch is fed through a tapered microstrip line instead of using a microstrip line with inset feed. The achieved gain, AR, and radiation efficiency are 6.6 dBi, 0.6 dB, and 92%, respectively, at 38 GHz and are 6.7 dBi, 1.6 dB, and 75%, respectively, at 50 GHz. The antenna is printed on a substrate of thickness 0.25 mm and the outer dimensions of the planar composite patch structure are 2.9 mm × 2.9 mm. The antenna bandwidth to provide good circular polarization with perfect impedance matching at the same time are 800 MHz (37-37.8 GHz) and 200MHz (49.9-50.1 GHz) for the lower and higher frequency bands, respectively. The proposed antenna is fabricated and its performance assessed by simulation is validated by comparison with the results of microwave measurements. Both the simulation and measurement results show good performance of the proposed antenna over the lower and higher frequency bands of operation.