Kin-Fai Tong

A broad-band U-slot rectangular patch antenna on a microwave substrate

A broad-band U-slot rectangular patch antenna printed on a microwave substrate is investigated. The dielectric constant of the substrate is 2.33. The antenna is fed by a coaxial probe. The characteristics of the U-slot patch antenna are analyzed by the finite-difference time-domain (FDTD) method. Experimental results for the input impedance and radiation patterns are obtained and compared with numerical results. The maximum impedance bandwidth achieved is 27%, centered around 3.1 GHz, with good pattern characteristics.

Circularly Polarized U-Slot Antenna

Circularly polarized single-layer U-slot microstrip patch antenna has been proposed. The suggested asymmetrical U-slot can generate the two orthogonal modes for circular polarization without chamfering any corner of the probe-fed square patch microstrip antenna. A parametric study has been carried out to investigate the effects caused by different arm lengths of the U-slot. The thickness of the foam substrate is about 8.5% of the wavelength at the operating frequency. The 3 dB axial ratio bandwidth of the antenna is 4%. Both experimental and theoretical results of the antenna have been presented and discussed. Circular polarization, printed antennas, U-slot.

New Proximity Coupled Feeding Method for Reconfigurable Circularly Polarized Microstrip Ring Antennas

A new simple single-feed method for circularly polarized ring antennas has been investigated. Experimental and theoretical investigation show that either right-handed (RH) or left-handed (LP) circular polarization (CP) can be easily achieved by selecting one of the two input ports of the antennas. The proposed U-shaped microstrip feed line excites the fundamental TM11 mode of the ring radiating elements through proximity coupling along the semi-annular section of the line. The induced rotating surface currents on the ring radiators contribute to the circular polarization behavior of the antennas. Two types of rings have been investigated. Square ring prototypes operate at 2.7 GHz have been designed, fabricated and evaluated to show the basic operating principles of the antennas, while annular ring radiating elements operate at 2.255 GHz are realized to demonstrate the reconfigurable capability of the new feeding structure. In the reconfigurable design, a high isolation RF switch is used to direct the input signal between the two input ports. With suitable biasing arrangement of the RF switch, the antenna is capable to radiate at either types of circular polarization. The reconfigurable design is fed by a single microstrip line. Return losses, axial ratios, gains and radiation patterns of the prototype antennas have been measured for verifications. A parametric study of the new feeding structures with a square ring has been carried out for important design guidelines.

Microstrip Patch Antennas—Basic Characteristics and Some Recent Advances

The basic geometry of a microstrip patch antenna (MPA) consists of a metallic patch printed on a grounded substrate. Three commonly used feeding methods are coaxial feed, stripline feed, and aperture-coupled feed. The patch antenna idea was first proposed in the early 1950s, but it was not until the late 1970s that this type of antenna attracted serious attention of the antenna community. The microstrip patch antenna offers the advantages of low profile, conformability to a shaped surface, ease of fabrication, and compatibility with integrated circuit technology, but the basic geometry suffers from narrow bandwidth. In the last three decades, extensive studies have been devoted to improve the performance of this antenna and the MPA has found numerous applications in both the military and the commercial sectors. This article begins with a brief description of the modeling techniques and basic characteristics of the MPA. Methods of broadbanding, dual and multiband designs, size-reduction techniques, and design for circular polarization are then reviewed. The paper ends with some concluding remarks.

Frequency diverse array with beam scanning feature

In this paper, the radiation characteristics of frequency diverse array (FDA) are explored by EM simulation. An intuitive beam scanning feature is observed from the transient field simulation results. The scanning speed is proved to be related to the frequency increment between two neighboring elements. Moreover, the relation between beam angle and time is derived for pulsed applications and verified mathematically.

Planar Endfire Circularly Polarized Antenna Using Combined Magnetic Dipoles

A novel planar circularly polarized antenna with endfire radiation beam in parallel with the antenna substrates plane is proposed. The operation principle of the antenna is analyzed and design guidelines are laid down. Then, an optimized loop-aperture combined antenna is designed and demonstrated to exhibit an endfire beam in parallel with its plane within 5.74-5.88 GHz for |S11| lower than -10 dB and axial ratio smaller than 3 dB. The proposed antenna can be used as a low-profile, cost-effective, hand-held reader antenna for radio frequency identification systems .

A Survey of Emerging Interconnects for On-Chip Efficient Multicast and Broadcast in Many-Cores

Networks-on-chip (NoC) have emerged to tackle different on-chip communication challenges and can satisfy different demands in terms of performance, cost and reliability. Currently, interconnects based on metal are reaching performance limits given relentless technology scaling. In particular, a performance bottleneck has emerged due to the demands for communication in terms of bandwidth for multicasting and broadcasting. As a result, various state-of-the-art architectures have been proposed as alternatives and emerging interconnects including the use of optics or radio frequency (RF). This article presents a comprehensive survey of these various interconnect fabrics, and discusses their current and future potentials and obstacles as well. This article aims to drive the research community to achieve a better utilization of the merits of on-chip interconnects and addresses the challenges involved. New interconnect technologies, such as optical interconnect, wireless NoC (WiNoC), RF transmission lines (RF-I) and surface wave interconnects (SWI), are discussed, evaluated and compared. Consequently, these emerging interconnects can continue to provide the cost efficiency and performance that are highly demanded for future many-core processors and high performance computing.

A miniature monopole antenna for mobile communications

Strip monopole antennas printed on high-permittivity substrate are studied experimentally. Compared with the case without the dielectric slab, the resonant frequency of the monopole antenna is decreased by 50% when the antenna is fabricated on material of dielectric constant equal to 80. A wide impedance bandwidth of 35% can be achieved. The radiation patterns of the antennas and gain are insensitive to the dielectric constant of the substrate. The effect of the characteristic of the antennas by changing both the width of the dielectric material and the width of the strip of the monopole antenna is investigated.

Wideband coplanar waveguide fed coplanar patch antenna

We have presented simulation and experimental results of wideband coplanar waveguide fed coplanar patch antennas. The antennas were developed to widen the narrow bandwidth of the newly suggested coplanar patch antennas. This was achieved by introducing two identical parasitic patches next to the resonant edges of the main patch. Simulation was done by a commercial package. Antennas operating at 10 GHz were designed and fabricated. The return loss, radiation patterns and gain of the antennas were measured. An impedance bandwidth (return loss <-10 dB) of about 8.0 % and stable radiation patterns were observed, and the gain of the antennas were about 9.0 dBi. Design procedures and the experience of using the antennas have been discussed.

Dual-Band Loop-Dipole Composite Unidirectional Antenna for Broadband Wireless Communications

The design of a novel dual-band loop-dipole composite unidirectional antenna for broadband wireless applications is proposed. First, design guidelines of the antenna are presented, and then, a step-by-step derivation of the antenna geometry is drawn. The antennas operation principle is analyzed by carrying out parametric studies of surface current distribution, impedance and radiation patterns. The reflection coefficient, radiation patterns and gain of the antenna are numerically and experimentally studied to verify the operation principle and the design approach. It is demonstrated that two pass-bands, from 1.54 to 3.24 and from 4.88 to 6.80 GHz, of reflection coefficient smaller than -10 dB are obtained. The antenna has stable and unidirectional radiation pattern with low cross polarization within its pass-bands. The average gain of the antenna is 6.7 dBi at low frequency band and 6.5 dBi at high frequency band.