Baoxin Gao

A compact planar inverted-F antenna with a PBG-type ground plane for mobile communications

The ground plane affects the characteristics of a planar inverted-F antenna (PIFA) significantly. Using the idea of the high-impedance surface to construct the ground plane, a new type of compact PIFA with a photonic bandgap type (PBG-type) ground plane is proposed. Both the traditional PIFA and the proposed antenna are analyzed using the finite-difference time-domain (FDTD) method in detail. It is found that the two antennas have similar directivity pattern characteristics, but the size of the latter can be reduced obviously. The results also show that the bandwidth of a traditional PIFA is not greatly affected by the thickness of the metallic ground plane and that the shapes of the directivity patterns are not greatly affected by the ground plane under the small size condition. The operating-frequency band of the proposed antenna can be adjusted by changing the dielectric substrate thickness of the ground plane. They are suitable for mobile communication applications.

Influence of a metallic enclosure on the S-parameters of microstrip photonic bandgap structures

Planar microstrip photonic bandgap (PBG) structures are periodic arrays of holes etched in the ground plane of a conventional microstrip line. Most of the published studies considered the PBG as an unshielded structure. However, to fabricate a circuit with a PBG structure, a metallic enclosure is often needed. Thus, the S-parameters of the PBG structure will be altered correspondingly. In this paper, the influence of the metallic enclosure on a shielded PBG structure as well as the finite ground plane on an unshielded PBG structure on the S-parameters are analyzed using the finite-difference time-domain (FDTD) method. Conditions for which the influence can be neglected are obtained. The results are useful for the applications of PBG structures.

CAD models for asymmetrical, elliptical, cylindrical, and elliptical cone coplanar strip lines

By the conformal mapping method, we give analytical closed form expressions for the quasi-TEM parameters for asymmetrical coplanar strip lines (ACPSs) with finite boundary substrate. Then, based on the analysis of ACPSs, elliptical coplanar strip lines (ECPSs) and cylindrical coplanar strip lines (CCPSs), and elliptical cone coplanar strip lines (ECCPSs) are studied. Computer-aided-design oriented analytical closed-form expressions for the quasi-TEM parameters for ACPSs, ECPSs, CCPSs, and ECCPSs are obtained. All of the expressions are simple and accurate for microwave circuit designs and are useful for transmission-line theory and antenna theory. The reasonableness of the method and results are verified and various design curves are given.

Novel Microstrip Photonic Bandgap Cell Structures

In general, a planar microstrip photonic bandgap (PBG) structure os a periodic array of holes etched in the ground plane of a microstrip line. To use a circuit with a PBG, the PBG structure cannot be fixed on a metal base and needs to be shielded. In this paper, two kinds of novel microstrip PBG unit cells with special patterns etched in the strip line, which can be used as the conventional microstrip circuits, are proposed and analyzed in detail. The results show that the transmission line theory is valid for the theoretic analysis of PBG circuits.

A new method of designing MEMS class E amplifier

This paper presents the design and fabrication of metal contact MEMS switches for high efficiency Class E amplifier application. The efficiency of the amplifier is 64.3%, which agrees well with the simulation result. With properly selecting the metal contact MEMS switch, the amplifier efficiency may reach up to 99%. To our knowledge, this result presents the first published performance of Class-E amplifier using MEMS switch.

Comments on "CAD models for asymmetrical, elliptical, cylindrical, and elliptical cone coplanar strip lines"

For original paper see Z.Du, K.Gong, J.S.Fu, Z.Feng and B.Gao, ibid., vol.48, no.2, pp.312-6 (Feb 2000). In the original paper, Du et al. present analytical closed-form expressions for the quasi-TEM parameters for asymmetrical coplanar strip lines with a finite boundary substrate by using the conformal mapping technique. In this paper Gorur and Karpuz comment on their results. A reply to their comments by the original authors is included.

Design and implementation of a millimeter wave monolithic integrated mixer

This paper discusses design and implementation of a millimeterwave monolithic integrated balanced mixer, the measured performance compared with the predicted one is also reported. By designing this MMIC mixer, various mathematical methods are used, in which the Method of Conversion Matrix has been extended by the author to meet the requirement of inter-modulation analysis. The mixer is realized in a 2×3mm2GaAs chip, working in Ka band with bandwidth of 5GHz with a noise figure less than 10 dB.