Wideband temperature-variable attenuator
View Patent ↗An absorptive temperature-variable microwave attenuator is produced using a first plurality of shunt resistors separated by quarter-wave transmission lines connected by a series resistor with a second plurality of shunt resistors separated by quarter-wave transmission lines. At least one or more of the resistors are temperature-variable resistors. The temperature coefficients of the temperature-variable resistors are selected so that the attenuator changes at a controlled rate with changes in temperature while attenuator remains relatively matched to the transmission line. In one embodiment, the resistors are thick-film resistors and a variety of temperature coefficients can be created for each resistor by properly selecting and mixing different inks when forming the thick film resistors. Furthermore, attenuators can be created having either a negative temperature coefficient of attenuation or a positive temperature coefficient of attenuation.
1. A temperature-dependent radio-frequency attenuator, comprising:
a first temperature-dependent resistor having a first terminal provided to a first end of a first transmission line section and a second terminal provided to a first end of a second transmission line section;
a second temperature-dependent resistor having a first terminal provided to a second end of said first transmission line section and a second terminal provided to ground;
a third temperature-dependent resistor having a first terminal provided to said first end of said first transmission line section and a second terminal provided to ground;
a fourth temperature-dependent resistor having a first terminal provided to said first end of said second transmission line section and a second terminal provided to ground;
a fifth temperature-dependent resistor having a first terminal provided to a second end of said second transmission line section and a second terminal provided to ground, wherein at least one of said first, second, third, fourth, and fifth temperature-dependent resistors has a first temperature coefficient configured such that said attenuator changes attenuation at a controlled rate with respect to changes in temperature;
a third transmission line section, wherein a first end of said third transmission line section is provided to said second end of said second transmission line section, and wherein a first terminal of a sixth temperature-dependent resistor is provided to a second end of said third transmission line section and a second terminal is provided to ground; and
wherein a characteristic impedance of said third transmission line section is different from a characteristic impedance of said second transmission line section.
2. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said first temperature coefficient comprises a negative temperature coefficient of resistance.
3. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said first temperature coefficient comprises a positive temperature coefficient of resistance.
4. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said first temperature coefficient comprises a positive temperature coefficient of resistance and at least one of said first, second, third, fourth, and fifth temperature-dependent resistors has a negative temperature coefficient of resistance.
5. The temperature-dependent radio-frequency attenuator of claim 1 , wherein at least one of said first, second, third, fourth, and fifth temperature-dependent resistors comprises thick-film resistors.
6. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said first temperature-dependent resistor comprises a printed ink resistor.
7. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said attenuator has a negative temperature coefficient of attenuation.
8. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said attenuator has a positive temperature coefficient of attenuation.
9. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said first transmission line section comprises a microstrip transmission line.
10. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said first transmission line section comprises a stripline transmission line.
11. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said transmission line comprises a co-planar waveguide transmission line.
12. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said transmission line comprises a grounded co-planer waveguide transmission line.
13. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said transmission line comprises a coaxial transmission line.
14. The temperature-dependent radio-frequency attenuator of claim 1 , wherein a VSWR remains below 3 to 1 over a desired frequency band.
15. The temperature-dependent radio-frequency attenuator of claim 1 , further comprising an input transmission line provided to said first transmission line section.
16. The temperature-dependent radio-frequency attenuator of claim 1 , wherein a resistance of said second temperature-dependent resistor is approximately equal to a resistance of said fifth temperature-dependent resistor.
17. The temperature-dependent radio-frequency attenuator of claim 1 , wherein a resistance of said third temperature-dependent resistor is approximately equal to a resistance of said fourth temperature-dependent resistor.
18. The temperature-dependent radio-frequency attenuator of claim 1 , wherein said attenuator is symmetric.