Patch antenna syntheses - from direct feed, to broadband L-probe and to bandwidth controlled T-square feeds

Patch antenna synthesis is carried out through interpreting the available results, past and present. Briefly, the results are: (a) connected directly to a transmission line, a feed point on a patch of thin substrate generally gives a narrow frequency band of about 2 %, if the substrate has a low ε_r, of say 2.5; the resonant frequency can be determined by a simple formula with fringe field included; (b) fed by an L-probe, if the substrate is made quite thick to say 0.1λ_g, (in substrate), the patch is very broadband say 40 % especially if the substrate is air or foam; (c) fed by a probe in the shape of a T-square on a drafting board (i.e., the patch), with a moderate substrate thickness of say, 0.05 λ_g, then, the patch now has a bandwidth that is controllable by various dimensions of the T-square. This part of the results is new.