Electromechanical phase shifter for a microstrip microwave transmission line

A phase shifter for a microstrip microwave transmission line operating in a frequency band having a center frequency, comprising:

• a conductive base plate;
• a first fixed microstrip transmission line supported parallel to and spaced from the base plate so as to have a predetermined characteristic impedance;
• a second fixed microstrip transmission line supported parallel to and spaced from the first transmission line, and parallel to and spaced from the base plate so as to have said predetermined characteristic impedance;
• a first connector secured to a first end of said first transmission line;
• a second connector secured to a first end of said second transmission line;
• a movable microstrip transmission line in physical and electrical contact with and movable along both said first and second transmission lines toward and away from said first ends, said movable transmission line having said predetermined characteristic impedance;
• and
• a movable conductive ground element coupled to said movable transmission line for movement therewith, said ground element being in physical and electrical contact with said first and second transmission lines and said base plate on the other side of said movable transmission line from said first ends;
• wherein there is a spacing between the point of contact of said movable transmission line with each of said first and second transmission lines and the point of contact of said ground element with each of said first and second transmission lines, respectively, said spacing is equal to one quarter wavelength at said center frequency.