High isolation switch in balanced lines
A balanced line switching apparatus that provides high isolation at an expense of a marginal increase of loss. Practical implementation can give as much as 40 dB isolation in a single stage.
1. A high isolation switch comprising:
a balanced line including:
a first conductor having an input section and an output section, and
a second conductor having an input section and an output section;
a first switch connected in series between the input and output sections of the first conductor;
a second switch connected in series between the input and output section of the second conductor;
a third switch cross connected between the input section of the first conductor and the output section of the second conductor; and
a fourth switch cross-connected between the input section of the second conductor and the output section of the first section,
wherein an anode of the first switch and an anode of the third switch are connected at the input section of the first conductor, wherein an anode of the second switch and an anode of the forth switch are connected at the input section of the second conductor, wherein a cathode of the first switch and a cathode of the fourth switch are connected at the output section of the first conductor, and wherein a cathode of the second switch and a cathode of the third switch are connected at the output section of the second conductor.
2. The high isolation switch of claim 1 , wherein each of the first, second, third, and fourth switches have a high impedance state and a low impedance state.
3. The high isolation switch of claim 1 , wherein the conductors and switches are integrated on a silicon substrate.
4. The high isolation switch of claim 1 , wherein the first, second, third and fourth switches comprise diodes.
5. The high isolation switch of claim 1 , wherein the first, second, third and fourth switches comprise bipolar junction transistors.
6. The high isolation switch of claim 1 , wherein the first, second, third and fourth switches comprises multi-terminal devices.
7. The high isolation switch of claim 1 , wherein the first, second, third and fourth switches have substantially the same impedance in the high impedance state.
8. The high isolation switch of claim 1 , wherein in the off-state, the voltages coupled on each of the output sections by the input sections of the first and second conductors substantially cancel.
9. A switch comprising:
a balanced line including:
a first conductor having an input section and an output section, and
a second conductor having an input section and an output section;
a first switch connected in series between the input and output sections of the first conductor;
a second switch connected in series between the input and output section of the second conductor;
a third switch cross connected between the input section of the first conductor and the output section of the second conductor; and
a fourth switch cross-connected between the input section of the second conductor and the output section of the first section,
wherein the first and second switches are operative to switch between the high and low impedance states, and
wherein the third and fourth switches are biased to stay in the high impedance state.
10. A high isolation switch comprising:
a balanced line including:
a first conductor having an input section and an output section, and
a second conductor having an input section and an output section;
a first switch connected in series between the input and output sections of the first conductor;
a second switch connected in series between the input and output section of the second conductor;
a third switch cross connected between the input section of the first conductor and the output section of the second conductor; and
a fourth switch cross-connected between the input section of the second conductor and the output section of the first section,
wherein the first and second switches are operative to switch between the high and low impedance states,
wherein the third and fourth switches are biased to stay in the high impedance state,
wherein the high isolation switch has an on-state in which the first and second switches are in the low impedance state and the third and fourth switches are in the high impedance state, and
wherein the high isolation switch has an off-state in which the first and second switches are in the high impedance state and the third and fourth switches are in the high impedance state.
11. A high isolation switch comprising:
a balanced line including:
a first conductor having an input section and an output section, and
a second conductor having an input section and an output section;
a first switch connected in series between the input and output sections of the first conductor;
a second switch connected in series between the input and output section of the second conductor;
a third switch cross connected between the input section of the first conductor and the output section of the second conductor; and
a fourth switch cross-connected between the input section of the second conductor and the output section of the first section, and
wherein the high isolation switch is operative to provide high isolation over a broadband range of frequencies.