Yizhu Shen

A Low-Cost UWB-RFID System Utilizing Compact Circularly Polarized Chipless Tags

In this letter, circularly polarized (CP) chipless tags for a ultrawideband radio-frequency identification (UWB-RFID) system are demonstrated for the first time. Different from conventional linearly polarized tags, CP tags not only help to significantly reduce the mutual coupling between the transmitting and receiving antennas in a UWB-RFID reader, but also greatly lessen the signal ratio between structural and antenna modes to improve system performance. In addition, short delay line is adopted to make the chipless CP tag with compact size. Nevertheless, a short delay line usually results in the structural and antenna modes being overlapped. To separate these signals, a time-domain processing scheme is then proposed and validated. Measured results and system demonstration show that the compact chipless CP tag is a very promising candidate for low-cost UWB-RFID applications.

A microstrip-fed quasi-spiral circularly polarized ultra-wideband antenna

A circularly polarized (CP) quasi-spiral antenna for ultra-wideband (UWB) applications is proposed in this paper. By carefully choosing the offset feeding point and adopting an impedance transformer, the developed quasi-spiral antenna can be directly fed by a microstrip tapered line. The measured 10-dB return loss bandwidth and 3-dB axial-ratio (AR) bandwidth are 72.4% (5.15 to 11 GHz) and 44.3% (6.37 to 10 GHz), respectively. The measured antenna gain is about 3 dBi. Moreover, it can realize almost omni-directional radiation covering the upper UWB frequency range (7 – 10 GHz).

5.8-GHZ suppressed UWB bandpass filter employing modified CRLH-TL of two and three unit cells

This paper presents a novel modified composite right/lefthanded (CRLH) unit cell to achieve sharp rejection at 5.8 GHz. Design formulas are theoretically derived and numerically verified. Based on this unit cell, ultra-wideband (UWB) bandpass filters with two and three cells are designed, fabricated, and on-wafer measured. The measurement results show that the CRLH bandpass filter has a rejection of > 60 dB at 5.8 GHz, a minimum insertion loss of 1.1 dB, and 3-dB bandwidths of 3.09–4.79 GHz and 3.22–4.61GHz for the two and three unit cells, respectively.

IR-UWB-based chipless RFID system

This paper presents a chipless radio frequency identification (RFID) system, based on impulse radio ultra-wideband (IR-UWB) technology. This UWB-RFID system consists of a transmitter, a receiver, two tapered slot antennas, and several chipless tags. Covering the lower UWB frequency band in 3–5 GHz, the transmitter integrated circuit generates signals with high peak-to-peak amplitude of 6.6 V and short pulse duration of 1 ns. The receiver front end consists of amplifiers and filters, with total front-end gain up to 36 dB. This is followed by an equivalent time sampling analog to digital converter to sample the equivalent RF signals directly followed by digital signal processing in MATLAB. The tapered slot antenna has a high and relatively flat gain of 10 dBi. The chipless tag is uniplanar and with a size of 23 × 23 × 0.508 mm3 only. Based on these hardware designs developed in our research group, a novel method is proposed to separate two overlapped time-domain signals. This method, which is experimentally validated in this paper, greatly simplifies the hardware designs, especially the chipless tag. This chipless UWB-RFID system is an excellent candidate to realize a low-cost, low-power, and high-performance system for next-generation RFID applications.

Ultra-Wideband Measurement of the Dielectric Constant and Loss Tangent of Concrete Slabs

This paper is to investigate the dielectric properties of concrete slab and propagation characterization of ultra-wideband (UWB) frequency signals in the range of 3 to 5 GHz through the concrete slab. An insertion transfer function is obtained through frequency-domain measurement in free space in the presence and absence of the concrete slab. The dielectric constant and loss tangent of three concrete slabs are then calculated using a single-pass analysis method. Explanation has been given that the pulse shape distortion is mainly due to dispersion and attenuation of the concrete slab more than the interior multi-pass reflection.

A brief review of wideband circularly-polarized planar antenna design

Wideband circularly-polarized antenna is one of the key components in the wireless systems. This paper briefly reviews the design mechanisms of circularly-polarized antenna, and discusses their advantages and disadvantages. In addition, two circularly-polarized planar antennas for ultra-wideband systems developed in our group are also presented and discussed in this paper.

38 GHz folded reflectarray antenna for point-to-point 5G communications

With the rapid technology development and market expectation of wireless communication, 5G is the trend, bringing great opportunities as well as challenges. This paper presents a 38 GHz folded reflectarray antenna, which is a good candidate to satisfy the requirements in the 5G point-to-point communication, such as high gain, low profile, and low cost. The proposed antenna achieves high gain of 30.9 dBi, high efficiency of 53.73%, low sidelobe level about −23 dB, high cross polarization of 30 dB, and narrow beam width of 4.4°. It also achieve relatively wide gain bandwidth.

An ultra-wideband localization system for concrete debris tracking

Due to the limitations of traditional high speed video camera, ultra-wideband (UWB) technology is proposed to track debris of concrete in explosion. The UWB enabled debris tracking system is composed of active integrated tag embedded in concrete with size of only 25 × 25 × 25 mm, four sensors and one locator. The successful 2D position tracking test in real time in an indoor open area of 10 meters by 30 meters indicates the feasibility of the whole system and future application. Both variation of displayed position of tag updated in real time when concrete block moves, and the off-line computed trajectory with locator running in logging mode are with high accuracy.

Generating millimeter-wave Bessel beam with orbital angular momentum using reflective-type metasurface inherently integrated with source

Metasurfaces, orbital angular momenta (OAM), and non-diffractive Bessel beams have been attracting worldwide research. Combining the benefits of these three promising techniques, this paper proposes a metasurface-based reflective-type approach to generate a first-order Bessel beam carrying OAM. To validate this approach, a millimeter-wave metasurface is analyzed, designed, fabricated, and measured. Experimental results agree well with simulation. Moreover, this reflective-type metasurface, generating a Bessel beam with OAM, is inherently integrated with a planar feeding source in the same single-layer printed circuit board. Therefore, the proposed design features low profile, low cost, easy integration with front-end active circuits, and no alignment error between the feeding source and the metasurface.

Low-cost horn with unique radiation to evaluate probe-fed antenna measurement setup

This paper presents a low-cost back-to-back horn antenna in printed circuit board to evaluate an advanced millimeter-wave (mmWave) measurement setup for probe-fed antennas. Compared with conventional antennas with broadside radiation and smooth main beams, this back-to-back horn antenna features two unique characteristics, i.e., omnidirectional radiation and rippled beam at E-plane. These two characteristics significantly increase the measurement difficulties and make this horn antenna as one of the most difficult designs for probe-based measurement. Therefore, this antenna is an ideal candidate to evaluate a mmWave measurement setup for probe-fed antennas, by verifying its measurement capability of return loss, gain, 3D radiation pattern, efficiency, resolution, and dynamic range.