Tunable microstrip patch antenna and control system therefor

An antenna system including:

• an antenna having:
• a first patch that is electrically conductive and is dimensioned such that it has a resonant frequency when RF energy is fed thereto,
• a tuning strip that, when RF energy is electrically connected between said tuning strip and said first patch, changes said resonant frequency of said first patch, and
• a switch that electrically connects and disconnects RF energy between said first patch and said tuning strip;
• an RF feed that feeds RF energy to said first patch;
• and
• a control system coupled to said switch that applies predetermined DC biases to cause said switch to electrically connect and disconnect RF energy between said tuning strip and said first patch.

A method of controlling an antenna having a first patch that is electrically conductive and is dimensioned such that said first patch has a resonant frequency when RF energy is fed thereto, and a plurality of tuning strips, each of said tuning strips, when RF energy is electrically connected between said each tuning strip and said first patch, changes said resonant frequency of said first patch, said method comprising:

• connecting RF energy between certain of said tuning strips and said first patch while isolating other of said tuning strips from said first patch in accordance with a desired frequency so that said resonant frequency of said first patch approaches said desired frequency;
• preparing a table for respectively associating a plurality of predetermined combinations of said tuning strips with a plurality of predetermined resonant frequencies;
• receiving said desired frequency;
• looking up one of said predetermined resonant frequencies closest to said desired frequency in said table;
• and
• controlling the connection of RF energy between said first patch and one of said predetermined combinations of said tuning strips associated with said one of said predetermined resonant frequencies.

An antenna including:

• a ground plane that is electrically conductive having a first side surface;
• a superstrate having a first side surface and a second side surface opposite said first side surface;
• a first patch on said first side surface of said superstrate, said first patch being electrically conductive and having at least one edge;
• a dielectric layer positioned between said superstrate and said ground plane, said dielectric layer including:
• a first side surface in contact with said first side surface of said superstrate;
• and
• a second side surface in contact with said first side surface of said ground plane;
• at least one tuning strip on said second side surface of said superstrate that is electrically conductive, said tuning strip being spaced from said at least one edge of said first patch and spaced from said ground plane by said dielectric layer and said superstrate;
• an RF feed connected to said first patch;
• a switch, responsive to an applied DC bias, that electrically connects and disconnects RF energy between said at least one tuning strip and said first patch.