Voltage variable attenuator, an integrated circuit and a method of attenuation
The present disclosure provides a voltage variable attenuator (VVA) with a controllable matching network. The output of the attenuation portion of the VVA is couple to a matching network. The matching network includes a resistive element, which may be a Field Effect Transistor (FET), whose resistance may be controlled as a function of attenuation. In particular, a control voltage used to control the resistance of the attenuation portion of the VVA is also used to control the resistive element of the matching network. In this manner, the output impedance of the VVA may be maintained at a desired level.
1. A voltage variable attenuator with controllable output matching, the voltage variable attenuator comprising:
an attenuation network comprising at least one series arm and at least one shunt arm coupled to the at least one series arm, wherein a resistance of the at least one shunt arm is controllable in order to vary an attenuation of the voltage variable attenuator; and
a matching network coupled to the attenuation network, wherein the matching network comprises two or more shunt matching arms that are controllable to change an output impedance of the voltage variable attenuator, and a multiplexer coupled to each of the two or more shunt matching arms and to one or more control voltages.
2. The voltage variable attenuator of claim 1 , further comprising a control circuit configured to generate the one or more control voltages, wherein the one or more control voltages comprise a first control voltage arranged to control the resistance of the at least one shunt arm and that is provided to the multiplexer.
3. The voltage variable attenuator of claim 2 , wherein the voltage variable attenuator is configured such that an increase in the first control voltage signal increases the attenuation of the voltage variable attenuator and decreases the output impedance of the voltage variable attenuator.
4. The voltage variable attenuator of claim 1 , wherein the matching network further comprises at least one series matching arm.
5. The voltage variable attenuator of claim 4 , wherein the at least one series matching arm comprises an inductive element and each of the two or more shunt matching arms comprises a capacitive element.
6. The voltage variable attenuator of claim 1 , wherein the at least one series arm comprises at least one of an inductor, a transmission line, or a resistor.
7. The voltage variable attenuator of claim 1 , wherein the multiplexer determines which of the two or more shunt matching arms to select based on a frequency of operation of the voltage variable attenuator.
8. The voltage variable attenuator of claim 1 , implemented on an integrated circuit.
9. A voltage variable attenuator with controllable output matching, the voltage variable attenuator comprising:
an attenuation network comprising at least one series arm and at least one shunt arm coupled to the at least one series arm, wherein a resistance of the at least one shunt arm is controllable by one or more control voltages in order to vary an attenuation of the voltage variable attenuator;
a matching network coupled to the attenuation network, wherein the matching network comprises a first shunt matching arm and a second shunt matching arm that are controllable to change an output impedance of the voltage variable attenuator; and
a control circuit configured to generate the one or more control voltages for controlling the resistance of the at least one shunt arm, and to generate a separate control voltage for the matching network, the matching network further comprising a switch arranged to control which of the first shunt matching arm and the second shunt matching arm is controlled by the separate control voltage.
10. The voltage variable attenuator of claim 9 , wherein the first shunt matching arm comprises a first resistive element having a controllable resistance and the second shunt matching arm comprises a second resistive element having a controllable resistance.
11. The voltage variable attenuator of claim 10 , wherein the first resistive element is implemented as a first field-effect transistor (FET), and the second resistive element is implemented as a second FET.
12. The voltage variable attenuator of claim 9 , wherein the at least one shunt arm of the attenuation network comprises two or more shunt arms.
13. The voltage variable attenuator of claim 9 , wherein the first shunt matching arm comprises a field-effect transistor and a capacitor in series.
14. The voltage variable attenuator of claim 9 , wherein the first shunt matching arm is coupled to the attenuation network by way of an inductor.
15. The voltage variable attenuator of claim 9 , wherein the at least one shunt arm of the attenuation network comprises two or more shunt arms that are separately controlled by the control circuit.
16. A monolithic microwave integrated circuit (MMIC) comprising:
an input port configured to receive a radio frequency signal;
an output port configured to output an attenuated radio frequency signal; and
a voltage variable attenuator electrically coupled to the input port and to the output port, the voltage variable attenuator comprising:
an attenuation network comprising at least one series arm and at least one shunt arm coupled to the at least one series arm, wherein a resistance of the at least one shunt arm is controllable in order to vary an attenuation of the voltage variable attenuator; and
a matching network coupled to the attenuation network, wherein the matching network comprises at least two shunt matching arms that are controllable to change an output impedance of the voltage variable attenuator, and a switch arranged to control which of the at least two shunt matching arms is controlled by one or more control voltages.
17. The MMIC of claim 16 , wherein the voltage variable attenuator further comprises a control circuit configured to generate the one or more control voltages, the one or more control voltages arranged to control the resistance of the at least one shunt arm.
18. The MMIC of claim 17 , wherein the one or more control voltages comprise a first control voltage arranged to control the resistance of the at least one shunt arm and that is provided to the switch.
19. The MMIC of claim 18 , wherein the voltage variable attenuator is configured such that an increase in the first control voltage signal increases the attenuation of the voltage variable attenuator and decreases the output impedance of the voltage variable attenuator.
20. The MMIC of claim 16 , wherein the switch is controlled based on a frequency of operation of the voltage variable attenuator.