Steven Gao

A broad-band dual-polarized microstrip patch antenna with aperture coupling

In this communication, a dual-polarized aperture-coupled microstrip patch antenna with a broad-bandwidth high-isolation low cross-polarization levels, and low-backward radiation levels is designed and its features are presented. For broad bandwidth and easy integration with active circuits, it uses the aperture-coupled stacked patches. The corner feeding of square microstrip patches is applied and the coupling aperture is the H-shaped aperture. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. A dual-polarized antenna is designed, fabricated, and measured. The measured return loss exhibits an impedance bandwidth of over 24.4% and the isolation is better than 30 dB over the bandwidth. The cross-polarization levels in both E and H planes are better than -23 dB. The front-to-back ratio of the antenna radiation pattern is better than 22 dB. Both theoretical and experimental results for S parameters and radiation patterns are presented and discussed.

Dual-polarized broad-band microstrip antennas fed by proximity coupling

This work presents a novel broad-band dual-polarized microstrip patch antenna, which is fed by proximity coupling. The microstrip line with slotted ground plane is used at two ports to feed the patch antenna. By using only one patch, the prototype antenna yields a bandwidth of 22% and 21.3% at the input port 1 and 2, respectively. The isolation between two input ports is below -34 dB across the bandwidth. Good broadside radiation patterns are observed, and the cross-polar levels are below -21 dB at both E and H planes. Due to its simple structure, it is easy to form arrays by using this antenna as an element.

Antennas for Modern Small Satellites

Modern small satellites (MSS) are revolutionizing the space industry. They can drastically reduce the mission cost, and can make access to space more affordable. The relationship between a modern small satellite and a ldquoconventionalrdquo large satellite is similar to that between a modern compact laptop and a ldquoconventionalrdquo work-station computer. This paper gives an overview of antenna technologies for applications in modern small satellites. First, an introduction to modern small satellites and their structures is presented. This is followed by a description of technical challenges in the antenna designs for modern small satellites, and the interactions between the antenna and modern small satellites. Specific antennas developed for modern small-satellite applications are then explained and discussed. The future development and a conclusion are presented.

Multiple Band-Notched UWB Antenna With Band-Rejected Elements Integrated in the Feed Line

To mitigate potential interferences with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.35 GHz, or 5.725-5.825 GHz bands, four novel band-notched antennas suitable for ultra-wideband (UWB) applications are proposed. These include UWB antennas with a single wide notched band, a single narrow notched band, dual notched bands, and triple notched bands. Each antenna comprises a half-circle shaped patch with an open rectangular slot and a half-circle shaped ground plane. Good band-notched performance is achieved by using high permittivity and low dielectric loss substrate, and inserting quarter-wavelength horizontal/vertical stubs or alternatively embedding quarter-wavelength open-ended slots within the feed line. The results of both simulation and measurement confirm that the gain suppression of the single and multiple band-notched antennas in each desired notched band are over 15 dB and 10 dB , respectively. The radiation pattern of the proposed triple band-notched design is relatively stable across the operating frequency band.

Electrically Small and Low Cost Smart Antenna for Wireless Communication

A compact low-cost low-power smart antenna has been proposed in this paper. To reduce the cost and power consumption, it employs the structure of an Electronically Steerable Parasitic Array Radiator (ESPAR) antenna. To reduce the size of the antenna, a top-disk loaded monopole and six folded monopoles are employed as the driven element and parasitic elements, respectively. The proposed antenna is called “folded monopole ESPAR antenna”. The heights of the top-disk loaded monopole and folded monopoles are reduced to be less than . Furthermore, the radius of the folded monopole ESPAR antenna is reduced by using capacitive loading technique. An equivalent circuit model is proposed for analyzing the antenna. To validate the concept, a prototype is developed and the antenna operates from 2.3 GHz to 2.55 GHz. The measured results confirm that the folded monopole ESPAR antenna can achieve electronically beam scanning in horizontal plane over a 360 range. The prototype antenna achieves a gain of 4.0 dBi and a front-back ratio of 20 dB. The parasitic elements are loaded by varactors and beam forming is achieved by controlling the DC voltages applied to the varactors.

High-efficiency power amplifier design including input harmonic termination

This letter presents the design of a high-efficiency Class-F power amplifier in pseudomorphic high electron mobility transistor technology using a novel load-pull/source-pull simulation-based approach. The second harmonic input termination is shown to have a critical influence on performance, which is justified by the shape of the simulated waveforms. Experimental validation is carried out on a 2-GHz practical circuit using a medium-power packaged device. Two cases are compared both theoretically and experimentally: for the best and worst case second harmonic input terminations, 76% and 42% saturated power-added efficiency are measured, respectively. In addition, the worst case termination degrades the saturated C/I3 by 7.5dB.

FDTD Analysis of a Dual-Frequency Microstrip Patch Antenna

Characteristics of a single-layer, dual-frequency microstrip patch antenna, which uses a T-strip loaded rectangular microstrip patch, are studied. This antenna is easy to achieve good impedance matching at both frequencies by tuning the feed position and other design parameters. Another advantageous aspect is that it has high polarization purity. A detailed parameter study is performed and the theoretical analysis is based on the finite-difference time-domain (FDTD) method. The FDTD programs are developed and validated by measurement results. The effects of various antenna parameters on two resonant frequencies, frequency ratio, and radiation pattern characteristics of the antenna are analyzed and discussed. It is shown that various frequency ratios (1.5–2.49) can be obtained by varying the design parameters of this antenna. Similar radiation patterns with same polarization are obtained at two resonant frequencies. Several design curves are presented. 156 Gao, Li, and Sambell

Low-Cost Broadband Circularly Polarized Printed Antennas and Array

This paper presents the design, simulation, and measurements of two low-cost broadband circularly polarized (CP) printed antennas: an element and an array at 2 GHz. To realize the broadband circularly polarized antenna element, a circular microstrip patch is electromagnetically coupled by crossed slots cut in the ground plane, which is fed by an L-shaped microstrip feed. Two orthogonal modes in the patch are excited by using the crossed slots, and a single L-shaped feed provides a 90deg phase shift between two orthogonal slots. The antenna element achieves a 9.6% bandwidth for an axial ratio (AR) below 3 dB and a voltage standing wave ratio (VSWR) below 1.5. To further improve the performance, a sequentially rotated feed network is designed for a 2 times 2 array. The axial ratio value of the array is below 3 dB within a 27.2% bandwidth, from 1.75 GHz to 2.3 GHz. The return loss is above 10 dB within a 41% bandwidth, from 1.62 GHz to 2.45 GHz. Details of the proposed antenna element and the array design are described, and both the simulation and the experimental results are presented and discussed.

Multimode Resonator-Fed Dual-Polarized Antenna Array With Enhanced Bandwidth and Selectivity

A novel design concept of multimode filtering antenna, which is realized by integrating a multimode resonator and an antenna, has been applied to the design of dual-polarized antenna arrays for achieving a compact size and high performance in terms of broad bandwidth, high-frequency selectivity and out-of-band rejection. To verify the concept, a 2×2 array at C-band is designed and fabricated. The stub-loaded resonator (SLR) is employed as the feed of the antenna. The resonant characteristics of SLR and patch as well as the coupling between them are presented. The method of designing the integrated resonator-patch module is explained. This integrated design not only removes the need for separated filters and traditional 50 -Ω interfaces but also improves the frequency response of the module. A comparison with the traditional patch array has been made, showing that the proposed design has a more compact size, wider bandwidth, better frequency selectivity, and out-of-band rejection. Such low-profile light weight broadband dual-polarized arrays are useful for space-borne synthetic aperture radar (SAR) and wireless communication applications. The simulated and measured results agree well, demonstrating a good performance in terms of impedance bandwidth, frequency selectivity, isolation, radiation pattern, and antenna gain.

Integrated antenna/power combiner for LINC radio transmitters

This paper presents integrated antennas, which can fulfill both the functions of an antenna and a power combiner, thus reducing the circuit loss. This will be useful for linear amplification using nonlinear components systems, where the circuit-level power-combiner losses degrade overall efficiency. Two antennas, which use a single-layer structure and a multilayer structure, respectively, are designed. Both antennas achieve good impedance-matching characteristics under both even- and odd-mode excitations. The single-layer antenna has a narrow bandwidth, and the even-mode radiated power at boresight is 33 and 26 dB lower than that of the odd-mode radiated power at the E- and H-plane, respectively, thus demonstrating the effective suppression of even-mode radiation. The other antenna using multilayer structure achieves a broad-band bandwidth (S/sub 11/<-10 dB) of 15.5% and 8% under the odd- and even-mode excitation, respectively. Across the bandwidth, broadside radiation patterns with low cross-polar levels (<-21 dB) are achieved under the odd-mode excitation, while the even-mode radiation is also suppressed.