RF STEP ATTENUATOR

• US 20090108965A1
• Filed: 10/30/2007
• Published: 04/30/2009
• Est. Priority Date: 10/30/2007
• Status: Active Grant

• Current Assignee: Giga-tronics, Inc.
• Original Assignee: Giga-tronics, Inc.
• Inventors: Fuentes, Carlos
• Granted Patent: US 7,639,100 B2
• Time in Patent Office: Days
• US Class Current: 333/81.B
• CPC Class Codes: H01P 1/227 Strip line attenuators H01P1/23 takes precedence

Abstract

A broadband, high-speed RF step attenuator implemented using long-lifetime PIN diode switches is presented which provides step attenuation across a significant portion of the entire RF frequency spectrum while maintaining minimal insertion loss, return loss, and harmonics.

Claims

1. A PIN diode switch having a switch input port and a switch output port, the switch configured to switch between a pass-through state connecting the switch input port to the switch output port and a high impedance state isolating the switch input port from the switch output port, the switch comprising:

at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the series-connected long-lifetime PIN diodes each connected to the switch input port and the respective cathodes of the series-connected long-lifetime PIN diodes each connected to the switch output port;

at least two shunt-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the series-connected PIN diodes and the respective cathodes of the shunt-connected long-lifetime PIN diodes connected to a circuit ground; and

a control port configured to receive a control signal, control port connected to the respective cathodes of the series-connected long-lifetime PIN diodes and to the respective anodes of the shunt-connected long-lifetime PIN diodes.

2. The switch of claim 1, wherein each of the series connected long lifetime PIN diodes and the shunt-connected long lifetime PIN diodes are characterized by a capacitance of less than 0.15 pF across the entire RF frequency spectrum.

3. The switch of claim 1, wherein the switch input port is connected to a first section of a signal line of a transmission line and the switch output is connected to a second section of a signal line of the transmission line.

12. The attenuation section of claim 10, connected in series with at least one additional attenuation pad of claim 1 to form a step attenuator circuit.

4. A PIN diode switch having a switch input port, a first switch output port, and a second switch output port, the switch programmable by way of a control signal and a complement control signal to connect the switch input port to one or the other of the first switch output port and the second switch output port, the switch comprising:

a first set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the first set of series-connected long-lifetime PIN diodes connected to the switch input port and the respective cathodes of the first set of series-connected long-lifetime PIN diodes connected to the first switch output port;

a first set of at least two shunt-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the first set of shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the first set of series-connected PIN diodes and the respective cathodes of the first set of shunt-connected long-lifetime PIN diodes connected to a circuit ground;

a second set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the second set of series-connected long-lifetime PIN diodes connected to the switch input port and the respective cathodes of the second set of series-connected long-lifetime PIN diodes connected the second switch output port;

a second set of at least two shunt-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the second set of shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the second set of series-connected PIN diodes and the respective cathodes of the second set of shunt-connected long-lifetime PIN diodes connected to the circuit ground; and

the respective cathodes of the first set of series-connected long-lifetime PIN diodes and the respective anodes of the first set of shunt-connected long-lifetime PIN diodes connected for control by the control signal, and the respective cathodes of the second set of series-connected long-lifetime PIN diodes and the respective anodes of the second set of shunt-connected long-lifetime PIN diodes connected for control by the complement control signal.

5. The switch of claim 4, wherein each of the PIN diodes in the first and second set of series connected long lifetime PIN diodes and the first and second sets of shunt-connected long lifetime PIN diodes are characterized by a capacitance of less than 0.15 pF across the entire RF frequency spectrum.

6. The switch of claim 4, the switch input port connected to a grounded coplanar waveguide signal line, the first switch output port connected to a non-attenuated signal line path, and the second switch output port connected to an attenuated signal line path.

7. A PIN diode switch having a first switch input port, a second switch input port, and a switch output port, the switch programmable by way of a control signal and a complement control signal to connect one or the other of the first switch input port and the second switch input port to the switch output port, the switch comprising:

a first set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the first set of series-connected long-lifetime PIN diodes each connected to the first switch input port and the respective cathodes of the first set of series-connected long-lifetime PIN diodes connected to the switch output port;

a first set of at least two shunt-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes connected to the respective cathodes of the first set of series-connected PIN diodes and the respective cathodes connected to a circuit ground;

a second set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes each connected to the second switch input port and the respective cathodes connected to the switch output port;

a second set of at least two shunt-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes connected to the respective cathodes of the of the second set of series-connected PIN diodes and the respective cathodes connected to the circuit ground; and

the respective cathodes of the first set of series-connected long-lifetime PIN diodes and the respective anodes of the first set of shunt-connected long-lifetime PIN diodes connected for control by the control signal, and the respective cathodes of the second set of series-connected long-lifetime PIN diodes and the respective anodes of the second set of shunt-connected long-lifetime PIN diodes connected for control by the complement control signal.

8. The switch of claim 7, wherein each of the series connected long lifetime PIN diodes and the shunt-connected long lifetime PIN diodes are characterized by a capacitance of less than 0.15 pF across the entire RF frequency spectrum.

9. The switch of claim 7, the switch input port connected to a grounded coplanar waveguide signal line, the first switch output port connected to a non-attenuated signal line path, and the second switch output port connected to an attenuated signal line path.

10. An attenuation section, comprising:

a grounded coplanar waveguide, the coplanar waveguide comprising a ground, an input signal line, an output signal line, a first signal line path connectable between the input signal line and the output signal line, and a second signal line path connectable between the input signal line and the output signal line, the second signal line path having a higher attenuation than the first signal line path;

at least one control port configured to provide a control signal and a complement of the control signal;

a first set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the first set of series-connected long-lifetime PIN diodes each connected to the signal line input and the respective cathodes of the first set of series-connected long-lifetime PIN diodes each connected to the first signal line path;

a first set of at least two shunt-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the first set of shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the first set of series-connected long-lifetime PIN diodes and the respective cathodes of the first set of shunt-connected long-lifetime PIN diodes connected to the coplanar waveguide ground;

a second set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the second set of series-connected long-lifetime PIN diodes each connected to the signal line input and the respective cathodes of the second set of series-connected long-lifetime PIN diodes each connected the second signal line path;

a second set of at least two shunt-connected long-lifetime PIN diodes an anode and a cathode, the respective anodes of the second set of shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the second set of series-connected long-lifetime PIN diodes and the respective cathodes of the second set of shunt-connected long-lifetime PIN diodes connected to the coplanar waveguide ground;

a third set of at least two series-connected long-lifetime PIN diodes each having an anode and a cathode, the respective anodes of the third set of series-connected long-lifetime PIN diodes each connected to the first signal line path and the respective cathodes of the third set of series-connected long-lifetime PIN diodes each connected to the output signal line;

a third set of at least two shunt-connected long-lifetime PIN diodes an anode and a cathode, the respective anodes of the third set of shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the third set of series-connected long-lifetime PIN diodes and the respective cathodes of the third set of shunt-connected long-lifetime PIN diodes connected to the coplanar waveguide ground;

a fourth set of at least two series-connected long-lifetime PIN diodes an anode and a cathode, the respective anodes of the fourth set of series-connected long-lifetime PIN diodes each connected to the second signal line path and the respective cathodes of the fourth set of series-connected long-lifetime PIN diodes each connected to the output signal line;

a fourth set of at least two shunt-connected long-lifetime PIN diodes an anode and a cathode, the respective anodes of the fourth set of shunt-connected long-lifetime PIN diodes connected to the respective cathodes of the fourth set of series-connected long-lifetime PIN diodes and the respective cathodes of the fourth set of shunt-connected long-lifetime PIN diodes connected to the coplanar waveguide ground;

wherein each of the respective cathodes of the first set of series-connected long-lifetime PIN diodes, the respective anodes of the first set of shunt-connected long-lifetime PIN diodes, the respective cathodes of the third set of series-connected long-lifetime PIN diodes, and the respective anodes of the third set of shunt-connected long-lifetime PIN diodes are connected for control by the control signal; and

wherein each of the respective cathodes of the second set of series-connected long-lifetime PIN diodes, the respective anodes of the second set of shunt-connected long-lifetime PIN diodes, the respective cathodes of the fourth set of series-connected long-lifetime PIN diodes, the respective anodes of the fourth set of shunt-connected long-lifetime PIN diodes are connected for control by the complement control signal.

11. The attenuation section of claim 10, wherein all of the PIN diodes are characterized by a capacitance of less than 0.15 pF across the entire RF frequency spectrum.

13. The attenuation section of claim 10, wherein the transmission media comprises a grounded coplanar waveguide.

14. The attenuation section of claim 13, wherein the grounded coplanar waveguide is formed on a soft substrate material having a relative dielectric constant lower than at least 3.5.

15. The attenuation pad of claim 14, the substrate material comprising Duroid®

, or similar ceramic/glass impregnated Teflon®

based substrate material.