Variable inductor technique

An integrated circuit variable inductor comprising:

• a first inductor on a substrate;
• a second inductor arranged over said substrate and above said first inductor to permit inductive coupling with said first inductor, said second inductor having a first front-end node at its front end and a first back-end node at its back end, said second inductor having a contiguous conductive path between its front end and back end;
• a third inductor arranged under said substrate and below said first inductor to permit inductive coupling with said first inductor, said third inductor having a second front-end node at its front end and a second back-end node at its back end, said third inductor having a contiguous conductive path between its front end and back end;
• a switching network to selectively shunt together said first front-end and first back-end nodes so as to form a short circuit about said second inductor, and to selectively shunt together said second front-end and second back-end nodes so as to form a short circuit about said third inductor, and to selectively shunt together said first front-end node to said second back-end node and said first back-end node to said second front-end node so as to serially interconnect said second and third inductors in a closed circuit loop.

A variable inductor comprising:

• a first inductor having a first spiral arm, a first front-end node and a first back-end node;
• a second inductor having a second spiral arm, a second front-end node and a second back-end node, said second spiral arm being above said first spiral arm;
• a third inductor having a third spiral arm, a third front-end node and a third back-end node, said third spiral arm being below said first spiral arm;
• a switching network for selectively shunting together said second front-end node to said second back-end node, and for selectively shunting together said third front-end node to said third back-end node.