Hong-Li Peng

A New Type of Periodically Loaded Half-Mode Substrate Integrated Waveguide and Its Applications

A new type of half-mode substrate integrated waveguide (SIW) periodically loaded with different lumped elements and structures is proposed in this paper. The propagation constants, Bloch impedances, and voltage distributions of the Floquet TE-modes are all characterized by solving the eigenvalues of the generalized transmission matrix of a single period. Several typical capacitor-loaded, inductor-loaded, corrugated, and electromagnetic-bandgap (EBG)-loaded half-mode SIWs were fabricated to demonstrate their modal dispersion behavior. The measured and simulated S -parameters, group delays, and simulated electric field distributions in these novel structures are presented, with good agreements obtained for all samples. In particular, their unique controllable cutoff frequencies, multiple bandgaps, and separated monomode regions are also illuminated numerically and experimentally. To further show their applications, a tunable phase shifter is developed using a varactor-loaded structure, with its 3-dB bandwidth of 50% and a maximal tunable range of 88°. In addition, a bandpass filter based on EBG-loaded half-mode SIW is also realized and presented with its special characteristics. It demonstrates that the filter has a sharp upper slope side and a good performance of spurious suppression.

A COMPACT DUAL-POLARIZED BROADBAND ANTENNA WITH HYBRID BEAM-FORMING CAPABILITIES

A broadband dual-polarized four-port (DPFP) antenna is presented in this paper, which consists of a radiation element and a feed network. It is very compact in size, with the diameter of 150.0mm and the height of 47.0mm, with the following unique properties: (1) it has hybrid beam-forming capability and operates at two modes, which depends on its excitation; (2) its operating frequency range is from 0.96 to1.78GHz, and the return loss is about 10dB; (3) its insertion loss is (3 § 0:5)dB, with its balanced power splitting over the relative bandwidths of 37% at Mode 1 (180 - § 5 - phase shifting) and 55% at Mode 2 (§5 - phase shifting), respectively; (4) an isolation of 30dB at Mode 1 is obtained between the dual polarized ports, with the gain of 7.6dBi and 42 - of the 3dB-bandwidth at 1.25GHz; and (5) the gain difierence between Modes 1 and 2 is about 7dB, within the angle of i15 - • µ • 15 - for the same polarization at 1.25GHz. For the application of DPFP, a hybrid beam forming algorithm is proposed with an angular precision of 7 - and is validated by measurement.

Compact Quasi-Elliptic Wideband Bandpass Filter Using Cross-Coupled Multiple-Mode Resonator

A novel compact wideband bandpass filter (BPF) is proposed based on cross-coupled multiple-mode resonator (MMR). The proposed resonator is constructed by introducing cross coupling between the high-impedance lines of a classical MMR. It is shown that new symmetrical pairs of transmission zeros (TZs) can be generated at the lower and upper stopbands, respectively, leading to a quasi-elliptic function response that enhances the selectivity and out-of-band rejection significantly. One filter prototype is designed, fabricated and measured for validation and shows the expected performance.

PERFORMANCE EVALUATION OF UWB ON-BODY COMMUNICATION UNDER WIMAX OFF-BODY EMI EXISTENCE

A study of UWB on-body communication system performance, with the WiMax ofi-body electromagnetic interference (EMI) existence, is presented. Firstly, a compact UWB antenna with good on-body performance is verifled and chosen as our reference antenna. Using this realistic antenna, channel transfer function (CTF) of UWB on-body channel in an indoor room is investigated by measurements. Based on the measured data, the parameters of its pathloss model and its power delay proflle (PDP) model are extracted respectively. Secondly, a new body channel communication system model, composed of the on-body and ofi-body dual-link channel, together with UWB and WiMax signal models are presented. Finally, UWB on-body communication performances under difierent WiMax ofi-body EMI levels are studied by simulation. Simulated results show that this on-body system performance is quite limited and easily afiected by the ofi-body WiMax EMI. It is pointed out that the existing UWB on-body communication abilities should be greatly improved when WiMax ofi-body EMI signals are considered.

The Conformal HIE-FDTD Method for Simulating Tunable Graphene-Based Couplers for THz Applications

An improved hybrid implicit-explicit finite-difference time-domain (HIE-FDTD) method is proposed for simulating graphene-based patch couplers at terahertz (THz) for different physical and geometrical parameters, where the Drude model of monolayer graphene and the associated auxiliary differential equation (ADE) technique are implemented. In order to accurately model the curved graphene boundaries, the conformal FDTD method is further hybridized with the HIE-FDTD method, which results in a conformal HIE-FDTD method. Numerical results are presented for S-parameters and field distributions of the coupler, which can be adjusted effectively by changing the chemical potential and layer number of graphene patch or substrate permittivity.

Compact Tunable Bandpass Filter With a Fixed Out-of-Band Rejection Based on Hilbert Fractals

This paper proposes a new type of compact tunable bandpass filter with bandwidth tuning and out-of-band fixed rejection. Because we employ the modified Hilbert fractal structure loaded with varactors as resonators, the tunable filter has a very compact configuration and a constant shape over the entire tuning range. The frequency selectivity is improved by introducing a cross coupling between the source and the load. As a result of the utilization of a pair of properly designed feedlines, the frequency tuning and the out-of-band rejection of the filter are independent of each other, which simplifies its operation significantly. Two filter prototypes have been realized with the same size of 25.0 × 17.0 × 1.0 mm3. Their superior performances have been demonstrated experimentally, with good agreement obtained between their simulated and measured S-parameters.

A Novel Compact Dual-Band Antenna Array With High Isolations Realized Using the Neutralization Technique

A novel compact dual-band antenna array with high isolations is presented in this paper. It consists of four antenna elements with two feeding networks, and it operates at dual-band of 0.89-0.96 and 1.7-2.2 GHz with return loss more than 9 dB, respectively. Two feeding networks are made of a wideband balun and a Wilkinson power divider, respectively. The two-port symmetrical array is constructed using the neutralization technique (NT), leading to the array port isolation over 30 dB from 0.5 to 3.0 GHz. Such a compact dual-band antenna array is realized and its gains and normalized patterns for both ports P1 and P2 are measured, with good agreements obtained in comparison with the simulated ones.

A New Wideband Elliptic Bandstop Filter With Cross Coupling

A novel fifth-order elliptic cross-coupled wideband bandstop filter (BSF) is proposed and designed in this letter. It is devised by introducing additional electric coupling into two nonadjacent quarter-wavelength shunt stubs of a conventional commensurate line BSF. The selectivity and stopband rejection can be effectively enhanced by two extra transmission zeros generated from the coupling. The proposed BSF is designed directly from the normalized lowpass prototype by using the design formulas, which are derived based on the rigorous correspondence between the BSF and its lumped prototype in the S-plane. In order to demonstrate our design, a BSF example is developed, with a measured 27.2 dB stopband over a fractional bandwidth of 141.7%.

A Compact Single/Dual-Polarized Broadband Antenna With SUM and Difference Beam Capabilities

A novel compact single/dual linearly polarized antenna with broadband and SUM and Difference Beam capabilities is developed in this letter. An electromagnetic simulated model for its radiation element, together with its dual-mode feed network and antenna bracket, is proposed and verified by measurement. The operation band of the realized antenna is 0.96-1.78 GHz, with 10-dB return loss bandwidth of over 55%. As it operates at Mode 1, its dual linearly polarized port isolation is over 30 dB, and 3-dB gain beamwidth is 42° at 1.25 GHz, with gain of 7.6 dB obtained. The gain difference between Modes 1 and 2 is about 7 dB at 1.25 GHz within the angle of -15° ≤ θ ≤ 15° for the same polarization. The measured radiation patterns agree well with the simulated ones. The whole antenna is very compact in geometry, and its size is only about 155 mm in diameter and 47 mm in height.

Cavity Model Analysis of a Dual-Probe-Feed Circular Microstrip Patch Antenna

The cavity model is extended to analyze a dual-probe-feed circular microstrip patch antenna for both differential and single-ended operations. Particular emphasis is given to the impedance characteristics in order to understand the relationship between the differential and single-ended input impedances. It is shown that the differential input resistance is four times of the single-ended input resistance at the resonant frequency of the fundamental mode.