A NOVEL TECHNIQUE TO CALCULATE THE BANDWIDTH OF RECTANGULAR MICROSTRIP ANTENNA ELEMENTS WITH THICK SUBSTRATES

Existing methods to compute the bandwidth of probe-fed rectangular mic rostrip antenna elements are inaccurate for the range of substrate thi ckness considered for this research. When 0.0815 lambda(0) less than o r equal to h (lambda(0) is the free-space wavelength and h is the subs trate thickness) the effect of surface waves is predominant and must b e taken into account. A novel closed-form expression based on the cavi ty model and the exact Green's function for a grounded dielectric slab has been developed to compute the bandwidth of rectangular microstrip antenna elements, taking into account both the power radiated in spac e waves and the power radiated in surface waves. This method is origin al, simple, and easily included in a CAD system. The calculated result s are in good agreement with measurements. (C) 1996 John Wiley & Sons, Inc.