The objective of this book is: (1) To analyse, review and select the most appropriate geometric patch antenna to be used for automotive and Microsystems applications. (2) To design and simulate a rectangular patch antenna with three resonant frequencies of 2.45 GHz, 5.20 GHz, 5.80 GHz with bandwidths of 50 MHz around all resonant frequencies at -10 dB. (3) To simulate the full 3 dimensional electromagnetic field (E, H, Gain, Directivity, total efficiency) of a patch and adjust the size to meet the specifications. (4) To design the quarter wavelength for less reflected power between the antenna and the rest of the circuitry with a characteristic impedance of 50 Ω. (5) To review, select and simulate the best plastic used for automotive body parts before embedding the microstrip antenna. (6) To fabricate both patch antennas in free space and embedded in an ABS plastic. (7) To compare near and far field measurements of both antennas.