Coaxial variable capacitor

A method of adjusting capacitance of a variable capacitor, comprising:

• providing an enclosure having an interior, a top conductive collar and a bottom contact assembly electrically separated by a cylindrical insulator;
• providing a first movable capacitor plate assembly disposed in the interior of the enclosure, the first movable capacitor plate assembly including a first capacitor plate;
• providing a second movable capacitor plate assembly disposed in the interior of the enclosure, the second movable capacitor plate assembly including a second capacitor plate;
• providing a first flexible structure having a first end sealed to the top conductive collar and a second end sealed to the first movable capacitor plate assembly;
• providing second flexible structure, coaxial with and surrounding the first flexible structure and having a first end sealed to the top conductive collar and a second end sealed to the second movable capacitor plate assembly;
• providing a third flexible structure, coaxial with and surrounding the first and second flexible structures and having a first end sealed to the top conductive collar and a second end sealed to the second movable capacitor plate assembly;
• providing a first fixed capacitor plate assembly disposed proximal to the first movable capacitor plate assembly, the first fixed capacitor plate assembly including a third capacitor plate;
• providing a second fixed capacitor plate assembly disposed proximal to the second movable capacitor plate assembly, the second fixed capacitor plate assembly including fourth capacitor plate;
• providing a first actuator extending through the top conductive collar and through the first flexible structure, a distal end of the actuator engaging with a thrust collar, the first actuator for advancing and retracting the first movable capacitor plate assembly with respect to the fixed capacitor plate assembly;
• and
• providing a second actuator extending through the top conductive collar, the second actuator coupled via a piston structure to the second movable capacitor plate assembly, the second actuator for advancing and retracting the second movable capacitor plate assembly;
• wherein:
• the first and third capacitor plates comprise an interdigitated plurality of concentric cylindrical plates, and the second and fourth capacitor plates comprise an interdigitated plurality of concentric cylindrical plates;
• and
• actuating the first actuator to adjust the capacitance between the first and third capacitor plates, and actuating the second actuator to adjust the capacitance between the second and fourth capacitor plates.