Multi-band single-feed microstrip antenna system

Claim 1

A multi-band single-feed microstrip antenna system, comprising: a. a thin ground plane conductor; b. a plurality of separate thin radiating elements spaced from and electrically separated from said ground plane conductor by a dielectric substrate, one said radiating element for each frequency to be radiated; said respective radiating elements being operable to radiate simultaneously at a different and widely separated frequency from each other, the length dimension of each said respective radiating elements being different and determined by the respective radiation frequency wavelength of each radiating element; c. each of said radiating elements having a respective feed point thereon; d. a single common input point; e. said common input point being fed at all the different respective operating frequencies of said radiating elements; f. each of said radiating elements having its respective feed connected to said common input point by means of a respective single microstrip transmission line; each one of said radiating elements being matched at its respective operating frequency to the common input point while simultaneously being electrically decoupled from each of the other of said radiating elements through its respective one of said single transmission lines which act as transformation circuits, thus permitting all said radiating elements to be fed simultaneously from said common input point through said respective single transmission lines, the lengths and widths of each of the respective single transmission lines determining the interdependence between each of said respective radiating elements; g. each respective single microstrip transmission line which connects said common input point with the feed point on its respective one of said radiating elements being dimensioned to minimize the effect that any one of said radiating elements can have on the other of said radiating elements; the dimensions of said respective single transmission lines being varied such that at the operating frequency of each one of said respective radiating elements the input impedance looking toward the other of said radiating elements from said common input point approaches an open circuit, substantially isolating the respective radiating elements from each other while simultaneously being fed at said different respective frequencies from said common input point; h. any of the length and width dimensions of each of said single transmission lines and the location of the feed point on each of the respective radiating elements being variable to minimize the effects of any one of said radiating elements on any of the other said radiating elements and thus operate to effectively isolate each of said radiating elements from the other of said radiating elements.