Transistor switches with single-polarity control voltage
View Patent ↗Contrary to phase shifters which require complimentary polarity control voltages, a phase shifter may be driven with a single polarity control voltage. The phase shifter comprises an input node in communication with both a high pass network and a low pass network which are both in communication with an output node, where the phase shifter further comprises a first single pole double throw switch and a second single pole double throw switch configured to selectively pass an RF signal from the input node to the output node by way of one of said high pass network and said low pass network. Furthermore, the first and second single pole double throw switches are configured to select between the high pass network and the low pass network based on a single control signal having a voltage greater than or less than a reference voltage.
1. A single pole double throw (SPDT) field-effect transistor (FET) switch comprising:
a first FET comprising a first gate terminal, a first drain terminal, and a first source terminal;
a second FET comprising a second gate terminal, a second drain terminal, and a second source terminal;
an RF input node to communicate an RF input signal to the first and second drain terminals;
a first RF output node connected to the first source terminal;
a second RF output node connected to the second source terminal;
a first reference voltage node to bias the first source terminal and the first drain terminal based on a first reference signal, wherein a first bias circuit element is connected between the first source terminal and the first drain terminal, wherein the first reference voltage node is connected to the first source terminal, and wherein the first reference voltage node is connected to the first drain terminal via the first bias circuit element;
a control voltage node to provide a single control signal to the first gate terminal, and to bias the second source terminal and the second drain terminal based on the single control signal, wherein a second bias circuit element is connected between the second source terminal and the second drain terminal, wherein the control voltage node is connected to the second source terminal, and wherein the control voltage node is connected to the second drain terminal via the second bias circuit element; and
a second reference voltage node to provide a second reference signal to bias the second gate terminal.
2. The SPDT FET switch of claim 1 , wherein the second reference voltage node is a DC ground.
3. The SPDT FET switch of claim 1 , wherein the first bias circuit element comprises a first resistor, and wherein the second bias circuit element comprises a second resistor.
4. The SPDT FET switch of claim 1 , further comprising:
a first shunt FET located between the first RF output node and the first FET, wherein the first shunt FET is biased by the single control signal from the control voltage node, and the second reference voltage node provides the second reference signal to a gate of the first shunt FET;
a second shunt FET located between the second RF output node and the second FET, wherein the second shunt FET is biased by the first reference signal from the first reference voltage node, and the control voltage node provides the single control signal to a gate of the second shunt FET.
5. The SPDT FET switch of claim 1 , wherein the first FET turns on and the second FET turns off in response to a first voltage level of the single control signal, wherein the first FET turns off and the second FET turns on in response to a second voltage level of the single control signal, wherein the first voltage level is greater than the voltage level of the first reference signal, wherein the second voltage level is less than the voltage level of the first reference signal, and wherein the first voltage level is a positive voltage.
6. The SPDT FET switch of claim 1 , wherein a first RF path is from the RF input node, through the first FET, to the first RF output node, wherein a second RF path is from the RF input node, through the second FET, to the second RF output node, and wherein the first RF path and the second RF path comprise identical passive elements.
7. A single pole double throw (SPDT) field-effect transistor (FET) switch comprising:
a first FET comprising a first drain terminal and a first source terminal;
a second FET comprising a second drain terminal and a second source terminal;
an RF input node to communicate an RF input signal to the first and second drain terminals;
a first RF output node connected to the first source terminal;
a second RF output node connected to the second source terminal;
a first reference voltage node to bias the first FET based on a first reference signal from the first reference voltage node;
a control voltage node to provide a control signal to the first FET and to bias the second FET based on the control signal; and
a second reference voltage node to provide a second reference signal to the second FET;
wherein the first FET turns on and the second FET turns off in response to a first voltage level of the control signal, wherein the first FET turns off and the second FET turns on in response to a second voltage level of the control signal, wherein the first voltage level is greater than a voltage level of the first reference signal, wherein the second voltage level is less than the voltage level of the first reference signal, and wherein the first voltage level is a positive voltage.
8. The SPDT FET switch of claim 7 , wherein the SPDT FET switch is employed in a phase shifter.
9. The SPDT FET switch of claim 7 , wherein the second voltage level is a negative voltage.
10. The SPDT FET switch of claim 7 ,
wherein a first bias circuit element is connected between the first source terminal and the first drain terminal, wherein the first reference voltage node is connected to the first source terminal, and wherein the first reference voltage node is connected to the first drain terminal via the first bias circuit element; and
wherein the control voltage node provides the control signal to a first gate terminal of the first FET, wherein a second bias circuit element is connected between the second source terminal and the second drain terminal, wherein the control voltage node is connected to the second source terminal, and wherein the control voltage node is connected to the second drain terminal via the second bias circuit element.
11. The SPDT FET switch of claim 7 , further comprising:
a first shunt FET located between the first RF output node and the first FET, wherein the first shunt FET is biased by the control signal from the control voltage node, and the second reference voltage node provides the second reference signal to a gate of the first shunt FET; and
a second shunt FET located between the second RF output node and the second FET, wherein the second shunt FET is biased by the first reference signal from the first reference voltage node, and the control voltage node provides the control signal to a gate of the second shunt FET.
12. The SPDT FET switch of claim 7 , wherein a first RF path is from the RF input node, through the first FET, to the first RF output node, wherein a second RF path is from the RF input node, through the second FET, to the second RF output node, and wherein the first RF path and the second RF path comprise identical passive elements.
13. The SPDT FET switch of claim 7 , wherein the second reference voltage node is a DC ground.
14. A single pole double throw (SPDT) field-effect transistor (FET) switch comprising:
an RF input node;
a first RF output node connected to the RF input node via a first FET, defining a first RF path;
a second RF output node connected to the RF input node via a second FET, defining a second RF path; and
a control voltage node to provide a single control signal that causes switching between the first RF path and the second RF path; wherein the first RF path and the second RF path are symmetric and comprise identical passive elements.
15. The SPDT FET switch of claim 14 , further comprising:
a first reference voltage node to bias a first drain terminal and a first source terminal of the first FET based on a first reference signal;
a second reference voltage node to provide a second reference signal to a gate of the second FET;
wherein the control voltage node biases a second drain terminal and a second source terminal of the second FET based on the single control signal from the control voltage node.
16. The SPDT FET switch of claim 15 , wherein the control voltage node is connected to a gate of the first FET.
17. The SPDT FET switch of claim 15 , further comprising:
a first shunt FET located between the first RF output node and the first FET, wherein the first shunt FET is biased by the single control signal from the control voltage node, and the second reference voltage node provides the second reference signal to a gate of the first shunt FET;
a second shunt FET located between the second RF output node and the second FET, wherein the second shunt FET is biased by the first reference signal from the first reference voltage node, and the control voltage node provides the single control signal to a gate of the second shunt FET.
18. The SPDT FET switch of claim 15 , wherein a first bias circuit element is connected between the first source terminal and the first drain terminal of the first FET, wherein the first reference voltage node is connected to the first source terminal, and wherein the first reference voltage node is connected to the first drain terminal via the first bias circuit element; and
wherein the control voltage node provides the single control signal to a gate of the first FET, wherein a second bias circuit element is connected between the second source terminal and the second drain terminal, wherein the control voltage node is connected to the second source terminal, and wherein the control voltage node is connected to the second drain terminal via the second bias circuit element.
19. The SPDT FET switch of claim 15 , wherein the second reference voltage node is DC ground.
20. The SPDT FET switch of claim 15 , wherein the first FET turns on and the second FET turns off in response to a first voltage level of the single control signal, wherein the first FET turns off and the second FET turns on in response to a second voltage level of the single control signal, wherein the first voltage level is greater than the voltage level of the first reference signal, wherein the second voltage level is less than the voltage level of the first reference signal, and wherein the first voltage level is a positive voltage.