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.

A novel and compact dual-polarized (DP) chipless radio-frequency identification (RFID) tag is presented in this paper. This tag can read both vertical and horizontal orientations within its frequency band, which improves the robustness and detection capability of the RFID system. The proposed tag makes use of the slot length variation encoding technique to improve the encoding capacity. This technique can duplicate the encoding capacity, thereby reducing the overall tag size by almost 50%. In particular, the proposed tag has an encoding capacity of 20 bits in the 3–8 GHz frequency band and achieves data density of around 15.15 bits/cm². Three prototypes are fabricated and tested outside an anechoic chamber. Furthermore, one tag is tested at different distances (10 cm, 30 cm, and 60 cm) from the reader and the measured results are compared. The simulated and measured results are in reasonable agreement, with acceptable shifts at some frequencies due to fabrication and experimental errors.

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.