Utilization of electromagnetic band-gap (EBG) structures is becoming attractive in the electromagnetic and antenna community. In this paper, a mushroom-like EBG structure is analyzed using the finite-difference time-domain (FDTD) method. Its band-gap feature of surface-wave suppression is demonstrated by exhibiting the near field distributions of the electromagnetic waves. The mutual coupling of microstrip antennas is parametrically investigated, including both the E and H coupling directions, different substrate thickness, and various dielectric constants. It is observed that the E-plane coupled microstrip antenna array on a thick and high permittivity substrate has a strong mutual coupling due to the pronounced surface waves. Therefore, an EBG structure is inserted between array elements to reduce the mutual coupling. This idea has been verified by both the FDTD simulations and experimental results. As a result, a significant 8 dB mutual coupling reduction is noticed from the measurements.

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Microstrip antennas integrated with electromagnetic band-gap (EBG) structures: a low mutual coupling design for array applications

The market for driver assistance systems based on millimeter-wave radar sensor technology is gaining momentum. In the near future, the full range of newly introduced car models will be equipped with radar based systems which leads to high volume production with low cost potential. This paper provides background and an overview of the state of the art of millimeter-wave technology for automotive radar applications, including two actual silicon based fully integrated radar chips. Several advanced packaging concepts and antenna systems are presented and discussed in detail. Finally measurement results of the fully integrated radar front ends are shown.

Millimeter-Wave Technology for Automotive Radar Sensors in the 77 GHz Frequency Band

This paper presents a novel single-patch wide-band microstrip antenna: the E-shaped patch antenna. Two parallel slots are incorporated into the patch of a microstrip antenna to expand it bandwidth. The wide-band mechanism is explored by investigating the behavior of the currents on the patch. The slot length, width, and position are optimized to achieve a wide bandwidth. The validity of the design concept is demonstrated by two examples with 21.2% and 32.3% bandwidths. Finally, a 30.3% E-shaped patch antenna, resonating at wireless communication frequencies of 1.9 and 2.4 GHz, is designed, fabricated and measured. The radiation pattern and directivity are also presented.

Wide-band E-shaped patch antennas for wireless communications

Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

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Electromagnetic Band Gap Structures in Antenna Engineering

The recently developed uniplanar compact photonic bandgap (UC-PBG) substrate is successfully used to reduce surface-wave losses for an aperture-coupled fed patch antenna on a thick high dielectric-constant substrate. The surface-wave dispersion diagram of the UC-PBG substrate has been numerically computed for two different substrate thickness (25 and 50 mil) and found to have a complete stopband in the frequency range of 10.9-13.5 and 11.4-12.8 GHz, respectively. The thicker substrate is then used to enhance broadside gain of a patch antenna working in the stopband at 12 GHz. Computed results and measured data show that, due to effective surface-wave suppression, the antenna mounted on the UC-PBG substrate has over 3-dB higher gain in the broadside direction than the same antenna etched on a grounded dielectric slab with same thickness and dielectric constant. Cross-polarization level remains 13 dB down the co-polar component level for both E- and H-planes.

Aperture-coupled patch antenna on UC-PBG substrate

This paper presents the use of selective lateral etching based on micromachining techniques to enhance the performance of rectangular microstrip patch antennas printed on high-index wafers such as silicon, GaAs, and InP. Micromachined patch antennas on Si substrates have shown superior performance over conventional designs where the bandwidth and the efficiency have increased by as much as 64% and 28%, respectively. In this work, the silicon material is removed laterally underneath the patch antenna to produce a cavity that consists of a mixture of air and substrate with equal or unequal thicknesses. Characterization of the micromachined patch antenna is presented herein and includes a discussion on the bandwidth improvements, radiation patterns, and efficiency of the patch. In addition, antenna placement on the reduced index cavity with respect to the high-index substrate is described to achieve efficiency improvements over conventional patch antennas.

Micromachined patch antennas

The authors design a rectangular patch antenna operating at f=23 GHz (K-band), with a dielectric constant of /spl epsiv//sub r/=10.8 and thickness of h=25 mils, with a suppressed TMo surface wave mode. Since for the given substrate, higher order modes exist at frequencies above 40 GHz, only the dominant mode needs to be eliminated.

Surface wave mode reduction for rectangular microstrip antennas

Microstrip patch antennas have been used extensively in vehicle and communication systems for the past several decades These antennas provide low profile, low-weight, and low-cost along with easy integration into planar circuit designs and array configurations The conventional planar microstrip geometry, however, has limited bandwidth and poor efficiency as well as limited power capability when probe fed or microstrip fed There are several factors which influence these parameters, the patch geometry and medium directly, and feeding structure indirectly Currently, designs are often implemented on low index materials for high patch efficiency, and wide bandwidth which can be increased further using wideband impedance matching networks and or aperture coupling methods Herein, an alternative approach is proposed which allows for easy implementation using micromachining The goal of this approach is to develop an "effective" low index material underneath the antenna while the feeding circuit is kept on the high index one The design of a conventional patch antenna fed by a microstrip is developed using micromachining techniques to decrease the height of the high index material underneath the patch while the material under the feedline remains unaltered This approach reduces the value of the effective dielectric constant only in the area under the antenna, since it is comprised of a mixed dielectric medium of high index material and air

I. Papapolymerou

Papers

Micromachined patch antennas

Surface wave mode reduction for rectangular microstrip antennas

Microstrip patch antennas on micromachined low-index materials