VARIABLE ATTENUATION CIRCUIT UTILIZING VARACTOR DIODES

Abstract

A variable attenuator circuit is disclosed. The variable attenuator circuit comprises a plurality of varactor diodes configured to attenuate an RF signal between an RF input and an RF output; a reference voltage input, and a control voltage input configured to vary the attenuation of the variable attenuator circuit based upon a control voltage. A radio frequency module and wireless device comprising said variable attenuator are also provided.

Description

Claims

1. A variable attenuator circuit comprising: a plurality of varactor diodes configured to attenuate a radio frequency (RF) signal between an RF input and an RF output;a reference voltage input; anda control voltage input configured to vary the attenuation of the variable attenuator circuit based upon a control voltage.

2. The variable attenuator circuit of claim 1 wherein the control voltage is configured to vary the attenuation of the variable attenuator circuit by changing the capacitances of one or more of the plurality of varactor diodes.

3. The variable attenuator circuit of claim 1 wherein the plurality of varactor diodes is arranged in a T-type or an L-type attenuator configuration.

4. The variable attenuator circuit of claim 1 wherein the plurality of varactor diodes is arranged in a pi-type attenuator configuration.

5. The variable attenuator circuit of claim 4 wherein the pi-type attenuator configuration comprises a first varactor diode connected in a series position between the RF input and the RF output and a second varactor diode and a third varactor diode, the second and third varactor diodes each connected in a shunt position on either side of the first varactor diode.

6. The variable attenuator circuit of claim 5 further comprising a first resistor arranged in parallel with the first varactor diode, a second resistor in a shunt position and in series with the second varactor diode, and a third resistor in a shunt position and in series with the third varactor diode.

7. The variable attenuator circuit of claim 6 wherein the second and third varactor diodes are connected to ground and are arranged in series between the ground connection and the second and third resistors, respectively.

8. The variable attenuator of claim 6 further comprising a first direct current (DC) blocking capacitor arranged in series with the first varactor diode, optionally such that the first resistor is arranged in parallel with both the first DC blocking capacitor and the first varactor diode.

9. The variable attenuator of claim 5 further comprising a second DC blocking capacitor arranged between the RF input and the shunt position of the second varactor diode.

10. The variable attenuator of claim 9 further comprising a first inductor arranged in a shunt position between the second DC blocking capacitor and the RF input.

11. The variable attenuator of claim 5 further comprising a third DC blocking capacitor arranged between the RF output and the shunt position of the third varactor diode.

12. The variable attenuator of claim 11 further comprising a second inductor arranged in a shunt position between the third DC blocking capacitor and the RF output.

13. The variable attenuator of claim 5 wherein at least one of the first, second, and third varactor diodes is formed as a bipolar junction transistor having emitter and collector terminals connected together.

14. The variable attenuator of claim 13 wherein the at least one of the first, second, and third varactor diodes formed as a bipolar junction transistor is an NPN bipolar junction transistor.

15. The variable attenuator of claim 5 further comprising a fourth varactor diode arranged in series with the first varactor diode and in an opposite direction in a back-to-back arrangement.

16. The variable attenuator of claim 5 further comprising a fifth varactor diode arranged in series with the second varactor diode and in an opposite direction in a back-to-back arrangement and/or a sixth varactor diode arranged in series with the third varactor diode and in an opposite direction in a back-to-back arrangement.

17. The variable attenuator of claim 1 implemented on a gallium arsenide substrate.

18. A radio frequency module comprising a variable attenuator, the variable attenuator having: a plurality of varactor diodes configured to attenuate an RF signal between an RF input and an RF output;a reference voltage input; anda control voltage input configured to vary the attenuation of the variable attenuator circuit based upon a control voltage.

19. A wireless communication device comprising a variable attenuator, the variable attenuator circuit having: a plurality of varactor diodes configured to attenuate an RF signal between an RF input and an RF output;a reference voltage input; anda control voltage input configured to vary the attenuation of the variable attenuator circuit based upon a control voltage.