Artificial transmission line using t-coil sections

Patent metadata

Field	Value
Publication number	US-11005442-B2
Application number	US-201916421226-A
Country	US
Kind code	B2
Filing date	May 23, 2019
Priority date	May 23, 2019
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

An electrical circuit can be formed at least in part using lumped or discrete circuit elements to provide an artificial transmission line structure that can mimic the electrical properties of a corresponding actual transmission line structure. Such an artificial transmission line structure can generally consume less area than an actual transmission line structure lacking such lumped or discrete elements. Such an artificial transmission line structure can be formed using two or more “unit cells” such as by cascading such cells as shown and described herein. The present inventors have recognized, among other things, that a unit cell of an artificial transmission line structure can include a t-coil section comprising magnetically-coupled inductors. Such an artificial transmission line structure can be used for applications such as phase shifting or to provide a delay line having a substantially constant group delay, among other applications.

First claim

The claimed invention is:

1. An electronic circuit defining an artificial transmission line structure comprising at least two unit cells, wherein a respective unit cell amongst the at least two unit cells comprises:
a first t-coil section defined by a first inductor mutually magnetically coupled and conductively coupled in series with a second inductor, and a first shunt capacitor coupled to a node between the first inductor and the second inductor; and
a third inductor conductively coupled in series with the second inductor, the third inductor located between the second inductor and an output node of the respective unit cell;
wherein the third inductor is arranged to suppress or inhibit mutual magnetic coupling of the third inductor with the first inductor and to suppress or inhibit mutual magnetic coupling of the third inductor with the second inductor.

2. The electronic circuit of claim 1 , comprising a fourth inductor conductively coupled in series with the first shunt capacitor.

3. The electronic circuit of claim 1 , comprising a second capacitor connected to bypass the first and second inductors, the second capacitor connected between an input node of the first t-coil section and an output node of the first t-coil section.

4. The electronic circuit of claim 1 , wherein values of the first, second, and third inductors are specified to provide a substantially linear phase response in a specified range of frequencies.

5. The electronic circuit of claim 1 , wherein a coupling coefficient corresponding to mutual magnetic coupling between the first inductor and the second inductor is established at an intermediate value between zero and one to provide a substantially linear phase response.

6. The electronic circuit of claim 5 , wherein the intermediate value is between about 0.5 and about 0.7.

7. The electronic circuit of claim 1 , wherein the first and second inductors have the same self-inductance value.

8. The electronic circuit of claim 1 , wherein the respective unit cell comprises a second shunt capacitor coupled to a node of the third inductor.

9. The electronic circuit of claim 8 , wherein the respective unit cell comprises a second t-coil section defined by the second inductor and the third inductor, the second t-coil section comprising the second shunt capacitor coupled to a node of the third inductor between second inductor and the third inductor.

10. The electronic circuit of claim 9 , comprising a fourth inductor in series with the first shunt capacitor.

11. The electronic circuit of claim 8 , wherein the second shunt capacitor j coupled to the output node at the third inductor opposite the node between the second inductor and the third inductor.

12. The electronic circuit of claim 1 , wherein the first and second inductors are defined by a symmetrical differential inductor.

13. The electronic circuit of claim 1 , wherein the first and second inductors have the same self inductance value.

14. The electronic circuit of claim 1 , comprising a phase shifter circuit including at least two selectable electrical paths coupling an input port to an output port, wherein one of the at least two selectable electrical paths comprises the artificial transmission line structure.

15. An electronic circuit defining an integrated phase shifter circuit, the electronic circuit comprising:
a first electrical path to provide a first specified phase shift, the first electrical path comprising an artificial transmission line structure comprising at least two unit cells, wherein a respective unit cell amongst the at least two unit cells comprises:
a first t-coil section defined by a first inductor mutually magnetically coupled and conductively coupled in series with a second inductor, and a first shunt capacitor coupled to a node between the first inductor and the second inductor; and
a third inductor conductively coupled in series with the second inductor, the third inductor located between the second inductor and an output node of the respective unit cell;
wherein the third inductor is arranged to suppress or inhibit mutual magnetic coupling of the third inductor with the first inductor and to suppress or inhibit mutual magnetic coupling of the third inductor with the second inductor; and
a second electrical path to provide a second specified phase shift different than the first specified phase shift;
at least a first switch to selectively couple an input signal through the first electrical path or the second electrical path in response to a control signal.

16. The electronic circuit of claim 15 , wherein values of the first, second, and third inductors are specified to provide a substantially linear phase response in a specified range of frequencies.

17. The electronic circuit of claim 15 , wherein a coupling coefficient corresponding to mutual magnetic coupling between the first inductor and the second inductor is established at an intermediate value between about 0.5 and about 0.7.

18. A method for controlling a delay value for an electrical signal using a phase shifter circuit, the method comprising:
receiving a control signal and, in response, selectively coupling the electrical signal through one of a first electrical path to provide a first specified phase shift or a second electrical path to provide a second specified phase shift different than the first specified phase shift;
wherein the first electrical path comprises an artificial transmission line structure comprising at least two unit cells, wherein a respective unit cell amongst the at least two unit cells comprises:
a first t-coil section defined by a first inductor mutually magnetically coupled and conductively coupled in series with a second inductor, and a first shunt capacitor coupled to a node between the first inductor and the second inductor; and
a third inductor conductively coupled in series with the second inductor, the third inductor located between the second inductor and an output node of the respective unit cell;
wherein the third inductor is arranged to suppress or inhibit mutual magnetic coupling of the third inductor with the first inductor and to suppress or inhibit mutual magnetic coupling of the third inductor with the second inductor.

19. The method of claim 18 , wherein values of the first, second, and third inductors are specified to provide a substantially linear phase response in a specified range of frequencies.

20. The method of claim 18 , wherein a coupling coefficient corresponding to mutual magnetic coupling between the first inductor and the second inductor is established at an intermediate value between about 0.5 and about 0.7.

Assignees

• Analog Devices International Unlimited Co

Inventors

• Wang Xudong
• Bagwell Michael W
• Beckwith William B
• Schiltz Thomas E

Classifications

• H03H7/32 Primary

  with lumped inductance and capacitance · CPC title

• H03H7/18 Primary

  Networks for phase shifting · CPC title

• H03H7/20

  Two-port phase shifters providing an adjustable phase shift · CPC title

• H03H7/09

  Filters comprising mutual inductance · CPC title