Microstrip antennas

FIGURE 8.9 Geometry of an equilateral-triangular microstrip circularly polarized microstrip antenna with (a) an H-type and (b) two 0 -inclined narrow slots... 

FIGURE 8.10 (a) Input impedance for the two equilateral-triangular microstrip antennas, (b) Optimum return loss frequency /rl and AR frequency /ar for different values of lengths h and g, concerning the 6 -inclined antenna... 

T. Kashiwa, T. Onishi, and I. Fukai, Analysis of microstrip antennas on a curved surface using the conformal grids FD-TD method, IEEE Trans. Antennas Propag., vol. 42, no. 

K. L. Wong, Compact and Broadband Microstrip Antennas. Piscataway, NJ Wiley Interscience, 2002. 

K. P. Prokopidis and T. D. Tsiboukis, FDTD algorithm for microstrip antennas with lossy substrates using higher-order schemes, Electromagn., vol. 24, no. 5, pp. 301—315, July 2004. 

Stauffer, P. R., Rosseno, F., Leoncini, M., and Gentili, G. B., 1998, Radiation Patterns of Dual Concentric Conductor Microstrip Antennas for Superficial Hyperthermia, IEEE Trans. Biomed. Engineering, 45(5) 605-613. 

Microstrip antennas, often referred to as patch antennas, are very well known and have received remarkable attention during the last four decades, even though the first idea dates back to the 1950s [5]. The success of microstrip and patch antennas is mainly... 

Varadan, V.K. Jose, K.A. and Varadan, V.V. Design and development of electronically tunable microstrip antennas. Smart Mater. Struct., 8 (1999), pp. 238-242... 

A microstrip patch is a representative candidate for a wearable integration, because it can be thin, lightweight, low maintenance, robust, and easily integrated into a garment and coupled with RF circuits (Wang et al., 2012). Moreover, the conductive textile used for antenna purposes has to have a low and stable electrical resistivity (<10/sq.) to minimize losses (Locher et al., 2006). Several properties of the materials can influence the behavior of the antenna properties. For instance, the permittivity and the thickness of the substrate change the bandwidth and the efficiency of a planar microstrip antenna (Liu et al., 2011). In general, fabrics present a complex structure, in term of density of fibers and hence air volume and size of the pores, which allow a very low dielectric constant with a reduction of the surface wave losses and an increase of the impedance bandwidth. 

In order to improve volume efficiency and reduce payload weight for earth-orbital remote-sensing applications, low-mass membrane-based synthetic aperture radar array concepts are being developed. One such system is an inflatable deployable SAR consisting of thin fabrics or membranes that are deployed for L-band operation with dual polarisation. The entire assembly is flexible before employment and is rolled up onto the spacecraft bus. The antenna comprises three membranes positioned vertically over one another the ground plane, the radiation patch, and the microstrip transmission line membranes74. 

Having determined the fundamental properties of higher order FDTD algorithms, a set of more complicated problems will be studied in this section. These include the analysis of microstrip, cavity-backed or dielectric resonator antennas with different polarizations, fractal arrays, and metamaterial-loaded structures. 

Microstrip patch and cavity-backed antennas constitute an indispensable part of many devices [ 1,9—18]. Their notable properties and adjustable features lead to various efficient designs, which comprise the fundamental elements of many up-to-date configurations in telecommunication technology. 

In traditional microwave systems antennae are fabricated on rigid substrates, as wires or as hollow structures. Antennae on textiles have been demonstrated earlier but only with limited design variations, mainly as microstrip patch or slot antennae. There is a need to explore different structures especially in view of multi-fiequency or wideband operation. 

D. M. Pozar, Finite Phased Arrays of Rectangular Microstrip Patches, IEEE Trans. Antennas Propag., Vol. AP-34, May 1986, pp. 658-665. 

Suitable topologies for the realization of wearable textile antennas exhibit a low profile and compact dimensions. Those features are particularly convenient for on-body placement and seamless integration into garments. For this reason, the majority of existing textile antennas are microstrip or patch antennas. 

G.A. Deschamps, Microstrip microwave antennas, in Third USAF Symposium on Antennas, 1953. 

S. Chen, T. Kaufmann, C. Fumeaux, Wearable textile microstrip patch antenna for multiple ISM band communications, in 2013 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2013. 

Several RF devices were fabricated (see Figure 10.6) using the above process. They include a 50-microstrip line, a patch antenna, a 4-by-l antenna array with feed network, and a spiral antenna. We note that all these structures remained intact after repetitive flexing and stretching. 

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