Jeffrey S. Fu

Chaotic phase code for radar pulse compression

This paper presents a novel binary phase coding scheme for radar pulse compression, which is derived from the logistic-map equation in the chaotic theory. The proposed logistic-map-based binary phase code (LMBPC) makes it feasible to achieve superior performance in detection range. The logistic-map equation in the chaotic theory is range resolution and Doppler tolerance simultaneously. The properties of LMBPC, including autocorrelation function, ambiguity diagram, performance under various noisy backgrounds, and the maximum Doppler tolerance, have been analyzed and compared to those of the conventional schemes, such as linear FM. The properties of LMBPC are very similar to those of the random binary codes. However, the generation of LMBPC is much simpler, and the available LMBPC is virtually infinite and not limited by the length of code. A parallel correlator structure for the pulse compression filter has also been introduced, which serves to improve the Doppler tolerance.

Particle swarm optimization and finite-element based approach for microwave filter design

A novel approach is proposed for compact planar microwave filter design. The powerful particle swarm optimization (PSO) and finite-element method (FEM) are combined together to allow optimal filter design with arbitrary geometries. This approach is much more flexible than traditional ones. An example using this PSO-FEM approach shows that this approach is effective to make the structure variation converge to the desired target and the final optimal filter structure has much smaller size.

A novel compact wide-band planar antenna for mobile handsets

A novel printed compact wide-band planar antenna for mobile handsets is proposed and analyzed in this paper. The radiating patch of the proposed antenna is designed jointly with the shape of the ground plane. A prototype of the proposed antenna with 30 mm in height and 50 mm in width has been fabricated and tested. Its operating bandwidth with voltage standing wave ratio (VSWR) lower than 3:1 is 870-2450 MHz, which covers the global system for mobile communication (GSM, 890-960 MHz), the global positioning system (GPS, 1575.42 MHz), digital communication system (DCS, 1710-1880 MHz), personal communication system (PCS, 1850-1990 MHz), universal mobile telecommunication system (UMTS, 1920-2170 MHz), and wireless local area network (WLAN, 2400-2484 MHz) bands. Therefore, it could be applicable for the existing and future mobile communication systems. Design details and experimental results are also presented and discussed.

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.

Empirical mode decomposition of micro-Doppler signature

Micro-Doppler induced by mechanical vibration or rotation of structures in a radar target is potentially useful for target detection, classification and recognition. In order to exploit the time-varying micro-Doppler signature, time frequency analysis techniques are used. However, they can not represent this useful information clearly all the time. In this paper, we introduce a novel algorithm to extract the micro-Doppler signature using a technique called empirical mode decomposition. Both simulation and the experimental results indicate that EMD provides us an effective way to give better time frequency representation of the micro-Doppler signature.

Low Hysteresis Dispersion La2O3 AlGaN ∕ GaN MOS-HEMTs

AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) using electron-beam evaporated high-dielectric-constant (high-k) lanthanum oxide layer (La 2 O 3 ) as the gate insulator have been investigated and compared with the traditional GaN HEMTs. The dielectric constant of the La 2 O 3 insulator layer developed in this study was 13.1. In addition, a negligible hysteresis voltage shift in the capacitance-voltage curves can be obtained after high temperature annealing. The compositions and the crystalline structures of La 2 O 3 with different annealing temperatures were observed by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The La 2 O 3 thin film achieved a good thermal stability after 200, 400, and 600°C postdeposition annealing owing to its high binding energy (835.7 eV) characteristics. Moreover, the gate leakage current of a traditional metal gate GaN HEMT can be suppressed for 1 order of magnitude after inserting a La 2 O 3 insulator between Ni and AlGaN, resulting in a better pulsed-mode operation. The device linearity was also improved due to its flat and wide transconductance (g m ) distribution, which was analyzed by a polynomial curve-fitting technique. Therefore, La 2 O 3 is a potential candidate high-k material for the gate insulator to enhance the GaN-based field effect transistor performance while scaling down the device dimension and device reliability at high power operation.

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.

28-GHz patch antenna arrays with PCB and LTCC substrates

Ka-band spectrum is relatively abundant and therefore attractive for services of satellite communication, targeting radar, and wireless broadband access technologies. However, Ka-band patch antenna is difficult in realization because the accurate manufacturing is indeed a challenge in obtaining excellent antenna performance at such high frequencies. This study develops three patch antenna arrays for operation at 28 GHz. Two of the three patch arrays with 2×2 and 4×1 patches, respectively, are realized on microwave printed circuit boards (PCBs). The experimental PCB patch arrays have bandwidths up to 5.7% and gains up to 13 dBi. Another 2×2 stacked-patch antenna array is fabricated with low temperature co-fired ceramic (LTCC) technology for further bandwidth enhancement. This LTCC stacked-patch array comprises a novel opposite-side feeding structure to prevent any electrical effect on the parasitic patch. A measured gain of 10.35 dBi and a wide bandwidth of 10.1% (26.75–29.6 GHz) are achieved.

Data fusion of multiradar system by using genetic algorithm

Detection system with distributed sensors and data fusion. are increasingly being used by surveillance systems. There has been a great deal of theoretical study on decentralized detection networks composed of identical or non-identical sensors. To solve the resulting nonlinear system, exhaustive search and some crude approximations are adopted. However, those methods often cause either the system to be insensitive to some parameters or the suboptimal results. In this paper, a novel flexible genetic algorithm is investigated to obtain the optimal results on constant false alarm rate data fusion. Using this approach, all system parameters are directly coded in decimal chromosomes and they can be optimized simultaneously. The simulation results show that adopting the proposed approach, one can achieve better performances than the reported methods and results.

Signal processing for automotive radar

With rising accident rates, researchers are looking for solutions to reduce fatalities. Some enhance car designs to protect drivers more adequately. Some propose improvements to the traffic and road systems to reduce the chances of accidents. Still others propose the installation of special gadgets to improve the situational awareness of drivers and to alert them to dangerous circumstances. A motor vehicle may be equipped with a radar sensor that checks the spatial environment around the vehicle. The radar is the most commonly adopted sensor for this purpose due to its all-weather capability. In this paper, a 77-GHz FMCW automotive radar signal processor is developed and implemented using the Renesas (previously Hitachi) SH7615 solutions engine development board. The project includes building additional required hardware, the DSP algorithm and a data simulator program to generate test data for testing. The main purpose of the automotive radar signal processor is to detect legitimate targets from unwanted clutter (e.g. road surfaces), and to extract target information from the radar returns. In this paper, the application of the new AND-OR CFAR is also introduced. The simple mathematical fusion models of the AND-OR CFAR are provided and explained here as well. This manuscript is divided into sections. The first section will delve into the basics and the building blocks of the automotive radar. The signal processing portion of this work will be presented in the second section. The data simulator built to simulate testing data is explained in the third section. Results from testing are put forward in section four. Conclusions drawn from the experience are presented in the last section.