Chow-Yen-Desmond Sim

A Compact Monopole Antenna for Super Wideband Applications

A planar microstrip-fed super wideband monopole antenna is initially proposed. By embedding a semielliptically fractal-complementary slot into the asymmetrical ground plane, a 10-dB bandwidth of 172% (1.44-18.8 GHz) is achieved with ratio bandwidth >;12:1. Furthermore, the proposed antenna also demonstrated a wide 14-dB bandwidth from 5.4 to 12.5 GHz, which is suitable for UWB outdoor propagation. This proposed antenna is able to cover the DVB-H in L-band (for PMP), DCS, PCS, UMTS, Bluetooth, WiMAX2500, LTE2600, and UWB bands.

Compact Slot Antenna for UWB Applications

A novel compact microstrip-fed slot antenna design is proposed. By properly loading a notch to the open-ended T-shaped slot and extending a small section to the microstrip feed line, multiple resonant frequencies are excited and merged to form a large enough 10-dB return loss bandwidth (measured from 3.1 to 11.45 GHz) for ultrawideband (UWB) applications. The vital parameters of the proposed antenna are illustrated, and a prototype is constructed and experimentally studied. The measured results show good radiation patterns and stable signal transmission within the band of interest.

Coupling-Feed Circularly Polarized RFID Tag Antenna Mountable on Metallic Surface

A square patch passive RFID tag antenna designed for UHF band is presented in this article. To achieve compact size and circular polarization (CP) radiation, the square patch is embedded with a cross slot, while an L-shaped open-end microstrip line linked to a tag-chip and terminated by a shorting pin is capacitively coupled to the patch. By selecting an appropriate length for the microstrip line and its coupling distance with the radiating element, easy control on the input impedance of the proposed tag antenna which leads to excellent impedance matching is achieved. The measured 10-dB return-loss bandwidth of the tag antenna is 50 MHz (904-954 MHz), while its 3-dB axial-ratio bandwidth is 6 MHz (922-928 MHz). Further experiment shows that the tag antenna can provide better reading range when mounted on a metallic surface.

A Slot Loaded Circularly Polarized Patch Antenna for UHF RFID Reader

The design of a simple UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna that operates within the 900 MHz band (902-928 MHz) is studied. To generate circular polarization (CP) radiation, a novel method of loading a semicircular slot into the main circular radiating patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the L-shaped probe-feed technique is employed in this design. From the experimental results, besides achieving a gain level of more than 7 dBic, the proposed antenna can also yield an impedance bandwidth (10-dB return loss) from 880 to 1100 MHz, while good CP performances between 901 to 930 MHz are exhibited. To further validate the experimental results, parametric studies are also carried out via simulation.

Compact Broadband Dual Coupling-Feed Circularly Polarized RFID Microstrip Tag Antenna Mountable on Metallic Surface

A square-shaped microstrip RFID tag antenna designed for 915 MHz band is proposed. The antenna is capacitively excited by a dual-offset coupling feed network with one of the feed lines a quarter-wavelength longer than the other. By selecting appropriate dimensions for the coupled lines and feed-lines, along with desirable coupling distance between the coupled line and square patch, the input impedance of the proposed tag antenna can be easily controlled, which results in excellent impedance matching. Moreover, by incorporating the dual-offset feed technique with the method of embedding a cross slot of unequal arm lengths into the square patch, the bandwidth of the circularly polarized (CP) operation can be enhanced. The measured 6-dB return-loss bandwidth of the tag antenna is 25 MHz (902-927 MHz), and its corresponding 3-dB axial-ratio (AR) bandwidth is 20 MHz (903-923 MHz). Further experimental results show that the proposed tag antenna can provide slightly better reading range and gain when mounted on a large metallic surface.

Planar UWB Antenna with 5 GHz Band Rejection Switching Function at Ground Plane

The design of an octagonal-shaped microstrip-fed planar monopole antenna for ultrawideband (UWB) operation is studied. Two inverted T-shaped slits are embedded on the ground plane to allow band rejection characteristic from 5 to 6GHz (for VSWR < 2). To enable switching capability for this band rejection function, a PIN diode is connected to each slit via a specifled chip inductor that will be further investigated. Several prototypes were constructed and the measured results show that the proposed antenna can provide an operating bandwidth from 3.07 to 10.7GHz, except for the rejected band. Simulation analyses are also carried out to validate the experimental results.

4G/5G Multiple Antennas for Future Multi-Mode Smartphone Applications

A hybrid antenna is proposed for future 4G/5G multiple input multiple output (MIMO) applications. The proposed antenna is composed of two antenna modules, namely, 4G antenna module and 5G antenna module. The 4G antenna module is a two-antenna array capable of covering the GSM850/900/1800/1900, UMTS2100, and LTE2300/2500 operating bands, while the 5G antenna module is an eight-antenna array operating in the 3.5-GHz band capable of covering the C-band (3400-3600 MHz), which could meet the demand of future 5G application. Compared with ideal uncorrelated antennas in an 8 × 8 MIMO system, the 5G antenna module has shown good ergodic channel capacity of ~40 b/s/Hz, which is only 6 b/s/Hz lower than ideal case. This multi-mode hybrid antenna is fabricated, and typically, experimental results such as S-parameter, antenna efficiency, radiation pattern, and envelope correlation coefficient are presented.

A Frequency Reconfigurable Half Annular Ring Slot Antenna Design

The design of a switchable microstrip-fed half annular ring slot antenna for multi-frequency operation is proposed. By incorporating three switches along the meandered tuning stub that is loaded on top of the half circular patch located within the circular slot, easy reconfigurability of four frequency bands over a frequency ratio of approximately 1.7:1 can be achieved. Furthermore, the proposed antenna structure does not require additional DC biasing circuit. Simulation and measurement results have demonstrated that the four frequency bands can exhibit good impedance matching, stable radiation patterns and desirable gains.

A Single Layer Dual-Band CP Microstrip Antenna for GPS and DSRC Applications

A simple integration design of a single layer, dual-feed circular polarization (CP) microstrip antenna for Global Positioning System (GPS) and Dedicated Short-Range Communication (DSRC) applications is presented. The GPS antenna element is excited by a square patch embedded with a corner-truncated square slot; while the DSRC antenna element is a usual corner-truncated square patch that fits perfectly into the slot with a small gap between them. The experimental results show that when loaded with a superstrate (protective cover) provided, the CP performances of the GPS antenna element are only slightly altered while apparent improvement including radiation pattern and peak gain for the DSRC antenna element is observed. Furthermore, the isolation between both feeding ports is well below –23 dB. Hence, this compact antenna design is suitable for mounting onto any vehicle that requires both GPS and DSRC services.

Microstrip-Fed Ring Slot Antenna Design With Wideband Harmonic Suppression

A microstrip-fed circular ring slot antenna (CRSA) with a fundamental mode at 2.45 GHz is initially studied. To suppress the additional harmonic modes excited by the ring slot, a single inverted U-shaped slot (or defected ground structure, DGS) is integrated into the CRSA. Through this, harmonic suppression over a wide bandwidth (approximately between 3 and 9 GHz) is achieved. This DGS can also be applied to other microstrip-fed ring slot antennas, such as square and triangular ring slot antennas.