Hong-Bo Zhu

Improved Frequency Notched Ultrawideband Slot Antenna Using Square Ring Resonator

An improved frequency notched ultrawideband (UWB) microstrip slot antenna with a square ring resonator embedded in the tuning stub is proposed. The antenna is investigated numerically and experimentally for its impedance matching property, frequency notched characteristic and radiation performance in detail. As will be reported, compared with conventional frequency notched slot antennas, after incorporating a square ring resonator with the slot antennas tuning stub, high, sharp band-rejection characteristic of over 20 dB is achieved, which is improved significantly.

Compact frequency notched ultra-wideband fractal printed slot antenna

A novel frequency notched ultra-wideband (UWB) fractal printed slot antenna is proposed. The antenna is similar in configuration to a conventional microstrip-fed wide slot antenna, however, by introducing a Koch fractal slot, not only the size of the antenna is reduced significantly but also frequency notched function is achieved. Several properties of the antenna such as impedance bandwidth, frequency notched characteristics, radiation patterns and gain, have been investigated numerically and experimentally in detail. As will be seen, the operation bandwidth of the antenna is from 2.85 to 12GHz, in which a frequency notched band from 4.65 to 6.40GHz may be achieved, and relatively stable, omnidirectional radiation performance over the entire frequency range has also been obtained.

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 .

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.

Planar Wideband Loop-Dipole Composite Antenna

A novel planar wideband balanced composite antenna is presented. The proposed antenna consists of a symmetrical dipole and an antipodal loop radiator. The return loss, radiation pattern, and gain of the antenna are numerically and experimentally studied. An impedance bandwidth of 129% (20 log |S11| <; -10dB) from 3.26 to 15 GHz has been obtained. Stable end-fire radiation patterns with good polarization purity and flat gain performances are obtained across the operating frequency range. In addition, the time domain responses of the proposed antenna are investigated. The proposed antenna can be used in compact wireless devices for point-to-point applications.

Improved Stable Scheme for the Time Domain Integral Equation Method

A novel technique for improving the stability of time domain electric field integral equation (TD-EFIE) method is presented. The method involving the introduction of a new class of temporal basis functions employs a modified form of TD-EFIE to generate stable transient responses from arbitrarily shaped conducting objects, which possesses the advantage of simplicity in implementation. Numerical examples are given to demonstrate the accuracy and the efficiency of the proposed method

A Novel Planar Endfire Circularly Polarized Antenna With Wide Axial-Ratio Beamwidth and Wide Impedance Bandwidth

A novel wideband planar endfire circularly polarized (CP) antenna with wide 3 dB axial ratio (AR) beamwidth is presented. The operation principle of the proposed CP antenna is described at first through the combination of a planar magnetic dipole and a V-shape open loop. Then, it is demonstrated how its AR beamwidth can be precisely controlled with resorting to the shape and thickness of the open loop element. Finally, the theoretical design approach is numerically verified, and the results are then experimentally validated. It is observed that a 3 dB AR beamwidth is achieved in an extremely wide angular region up to 250° within the principal elevation plane over a frequency range of 2.41-2.51 GHz. The proposed antenna has exhibited a wide impedance bandwidth of 22.23% in fraction, a 3 dB AR bandwidth of no less than 8.00% in fraction, and a simple planar profile in geometry. In addition, its endfire beam is in parallel with its plane.

Loop-Monopole Composite Antenna for Dual-Band Wireless Communications

A novel loop-monopole composite antenna for wireless communications is presented. The proposed antenna is composed of a loop, a monopole, a horizontal ground plane and a vertical reflector. The antennas operation principle is investigated and some design guidelines are laid down in the beginning. Then, an optimized loop-monopole composite antenna is designed. It is demonstrated that the antenna covers two bands from 2.16 to 3.21 GHz and from 4.24 to 7 GHz for |S11| smaller than -10 dB. The antenna has stable, unidirectional radiation pattern within its pass-bands. The average gain of the antenna is 4.5dBi (lower band) and 7.7dBi (higher band). The proposed antenna can be used as an indoor base station antenna for multiband wireless communications.

Ultra-wideband antipodal slot antenna with improved radiation performance

A novel antipodal wide-slot antenna for ultra-wideband (UWB) applications is proposed and studied in detail. The antenna is fed by a microstrip line terminated with a rectangular tuning patch. An antipodal structure is employed to improve the radiation performances. The return losses, surface E-field, current distribution, radiation patterns and gains of the antenna are numerically and experimentally investigated. Results show that the proposed antipodal antenna has an impedance bandwidth from 0.79 to 4.0 GHz, which is about 5:1. Compared with conventional rectangular wide-slot antenna, more stable radiation pattern with lower cross-polarisation level and flatter gain variation over a 3:1 bandwidth can be obtained. Thus, the proposed antenna should be more suitable for future UWB-multiple-input multiple-output applications using polarisation diversity than conventional UWB rectangular slot antennas.

Square loop antenna under even-mode operation: modelling, validation and implementation

ABSTRACT A square loop antenna under even-mode operation is analysed and an approximate model based on equivalent multiple sources is developed to describe its radiation characteristics. The calculated results of the proposed model are validated by a few classical analytical models at first. The proposed model is then applied to analyse traditional linearly polarised (LP) and circularly polarised (CP) loop antennas. Afterwards, it is further used to design a new loop-dipole combined antenna in the step-by-step procedure. It is theoretically exhibited that a loop antenna under even-mode excitation can work together a conventional dipole antenna with odd-mode feeding to form a new complementary antenna with cardiac-shaped radiation pattern. Finally, a prototype antenna is designed, fabricated and measured at the 2–3 GHz band. The operating fractional bandwidth of the proposed antenna can achieve up to 30% in both theory and measurement. In addition to that the proposed approximate model for the square loop antenna under even-mode operation is evidently confirmed, a new loop-dipole combined antenna is proposed and its predicted performance is found in good agreement with numerical and experimental results.