This paper focuses on the 60 GHz band, which is known to be very attractive for enabling next-generation abundant multi-Gbps wireless connectivity in 5G communication. We propose a novel concept of a double-layer antenna, loosely inspired from standard log-periodic schemes but with an aperiodic geometry, reduced size, and a limited number of elements while achieving excellent performance over the entire 60 GHz band. To maximize the antenna’s efficiency, we have developed a design that differs from those traditionally used for millimeter-wave communication applications. We aim to simultaneously maximize the gain, efficiency, and bandwidth. The reflection coefficient of the proposed design achieves a bandwidth of 20.66% from 53.9 GHz up to 66.3 GHz, covering the entire frequency band of interest. In addition, this proposed structure achieves a maximum realized gain of 11.8 dBi with an estimated radiation efficiency of 91.2%. The proposed antenna is simulated, fabricated, and tested in an anechoic chamber environment. The measurement data show a reasonable agreement with the simulation results, with respect to the bandwidth, gain, and side-lobe level over the operational spectrum.

Chipless radio frequency identification (RFID) technology recently observed a growing interest, mainly because of its wide area of applications, and huge potential market, with the advent of Internet of Things era. Recently, in the demonstration of high capacity chipless RFID tags, ultra-wide-band technology has been proposed. It can enable development of robust chipless RFID systems with the promising features of low cost, compact, and lightweight. In response, we propose a novel scheme of broadband chipless RFID tagging that is based on slot coupled tapered slot antenna (TSA) loaded with a set of resonators, referred to as multi-resonators filters (MRF). Using numerical simulations, out of 256 combinations, randomly selected 14 different 8-bit MRF circuits operating over the frequency band 4 to 9 GHz are designed and their spectral and time domain responses under short and open terminations are recorded. The time domain signatures, generated due to high impedance mismatches along the microstrip lines of MRFs terminated with open and short circuits, are quantified by finding the cross-correlation among the signals and that is done by calculating the pulse fidelity factor. The designed MRFs are integrated with TSA to develop chipless RFID tags, referred to as MRF-TSA tags. Our designed TSA operates over 3.5–18 GHz band with an average gain that exceeds 6.5 dBi. The retransmitted time domain signals from the MRF-TSA tags are modulated by loading the antenna with MRFs terminated with either short or open loads. The recorded time domain signals are reasonably distinguishable since 85% (96%) of fidelity factor values among the 14 different MRF-TSA tags with open/short termination are less than 0.70 (0.8), respectively. Finally, for verification purposes, two different MRF-TSA based chipless tags are designed and fabricated. RFID monostatic measurements based on the use of vector network analyzer are also reported.

We present a 4 × 4 slot-coupled Vivaldi antenna (SCVA) array unit cell, which offers wide bandwidth and high gain (~23 dBi) at the millimeter wave (mmW) frequencies of 28 GHz and 38 GHz. A single SCVA element is first presented, which has a bandwidth of 25–40 GHz with an average gain of ~13 dBi at the frequencies of interest. This antenna element is then used to design a 1 × 4 linear SCVA array matched to a 50 Ω impedance via a modified Wilkinson power divider (WPD). Next, the 1 × 4 linear array is used to construct a 4 × 4 antenna array unit cell. The proposed 4 × 4 antenna array unit cell is fabricated, and the characteristics of its elements (i.e., the single SCVA, 1 × 4 linear array, and WPD) are thoroughly investigated. Further, the 4 × 4 array is tested for signal reception of various digital modulation formats at lab environment using high-speed digital signal oscilloscope. In particular, a 2.5 Gbps data rate is successfully transmitted achieving receiver sensitivity of −50 dBm at 2 × 10⁻³ bit error rate (BER) for 32 quadrature amplitude modulation (QAM) with a system baud rate of 500 MHz. The wide bandwidth and high gain along with the excellent performance of the proposed 4 × 4 antenna array unit cell makes it an excellent candidate for future 5G wireless communication applications.

Chipless radiofrequency identification (RFID) technology is very promising for sensing, identification, and tracking for future Internet of Things (IoT) systems and applications. In this paper, we propose and demonstrate a compact 18-bit, dual polarized chipless RFID tag. The proposed tag is based on L-shaped resonators designed so as to maximize the spectral and spatial encoding capacities. The proposed RFID tag operates an over 4 GHz frequency band (i.e., 6.5 GHz to 10.5 GHz). The tag is simulated, fabricated, and tested in a nonanechoic milieu. The measured data have shown good agreement with the simulation results, with respect to resonators’ frequency positions, null depth, and null bandwidth over the operating spectrum. The proposed design achieves spectral and spatial encoding capacities of 4.5 bits/GHz and 18.8 bits/cm², respectively. This, in turn, gives an encoding density of 4.7 bits/GHz/cm². For code identification, we exploit the frequency content of the backscattered signals and identify similarity/correlation features with reference codes.

Diabetes is a chronic disease where millions of sufferers invasively prick their skin over the course of a day to take blood samples. Non‐invasive glucose monitoring would bring relief to diabetics because it offers reduced skin damage. Microwave sensors are becoming a good choice for non‐invasive glucose monitoring. This Letter presents two designs based on microwave sensors. The sensors have elliptical shapes and consist of a patch reflector and dielectric resonator (DR) that resemble a human thumb. A four‐layer thumb model is presented, with a focus on the permittivity of the blood layer. The thumb was moved to various positions on the two microwave sensors to observe the effect it had on the frequency shift with various blood permittivity values. Observations showed that the elliptical DR sensor was less sensitive to errors and thumb positioning when taking glucose measurements than the elliptical patch sensor. The elliptical DR had an error of 55 MHz from the centre frequency, whereas that of the elliptical patch was 140 MHz. The effects of thumbs with various blood permittivity values were explored and explained.