Broadbanded microstrip antenna having series-broadbanding capacitance integral with feedline connection

Claim 1

A broadbanded microstrip antenna comprising: a conductive reference surface; a conductive RF radiator element of approximately circular shape having a diameter of approximately one-half wavelength at the mid-point of its usable frequency bandwidth; a conductive standoff post physically and electrically connecting the center of said radiator element to the underlying reference surface and positioning said radiator element less that one-tenth wavelength thereabove; an RF disposed below said radiator element; a conductive RF feedline post connected to said RF input and extending, at least in part, upwardly towards said radiator element, a lower portion of said feedline post being dimensioned to provide series inductance L2; and an upper portion of said feedline post being spaced from the radiator conductor, the feedline post upper portion and the radiator conductor cooperating to establish an RF connection exhibiting a series capacitance C2, said inductance L2 and capacitance C2 being dimensioned to produce a 2:1 VSWR bandwidth of at least 25%.

Claim 21

A method of broadbanding a microstrip antenna of the type including a conductive reference surface and a conductive RF radiator element having at least one resonant dimension and disposed less then one-tenth wavelength above said reference surface so as to define a resonant cavity therebetween and further including an RF feedline structure coupled to a predetermined feedpoint of said radiator element, said feedline structure having an integral series capacitance and inductance, said method including the steps of: (1) modelling with a bandpass filter network model the integral series capacitance and inductance of said RF feedline structure to obtain optimized model parameters; (2) deriving an optimum series inductance value L2 and an optimum series capacitance value C2 for said feedline structure from said optimized model parameters; (3) providing said RF feedline structure dimensioned so as to exhibit approximately said derived optimum series inductance value L2; and (4) capacitively coupling said provided feedline structure to said conductive RF radiator element, including spacing said provided feedline structure a predetermined distance from the radiator element so as to provide a series capacitance therebetween of approximately said derived optimum series capacitance value C2.

Claim 22

A method of broadbanding a microstrip antenna of the type including a conductive reference surface and a conductive RF radiator element having at least one resonant dimension and disposed less then one-tenth wavelength above said reference surface so as to define a resonant cavity therebetween and further including an RF feedline structure coupled to a predetermined feedpoint of said radiator element, said feedline structure having an integral series capacitance and inductance, said method including the steps of: (1) modelling with a bandpass filter network model the integral series capacitance and inductance of said RF feedline structure to obtain optimized model parameters; (2) deriving an optimum series inductance value L2 and an optimum series capacitance value C2 for said feedline structure from said optimized model parameters; (3) providing said RF feedline structure dimensioned so as to exhibit approximately said derived optimum series inductance value L2; and (4) capacitively coupling said provided feedline structure to said conductive RF radiator element, including spacing said provided feedline structure a predetermined distance from the radiator element so as to provide a series capacitance therebetween of approximately said derived optimum series capacitance value C2.