Slides ma sc defense final

Broadband Microwave Negative Group Delay Transmission Line Phase Shifters

Sinan KeserM.A.Sc. Thesis Defense

October 1, 2012

2

Outline

• Introduction

• Background

• Loaded Transmission Lines

• Negative Group Delay (NGD) Phase Shifter Design

• Simulation & Experimental Results

• Conclusions

3

Phase shifters Basics

phase 𝜙 = arg 𝑆21

phase delay 𝜏𝑝 = −𝜙

𝜔

group delay 𝜏𝑔 = −𝜕𝜙

𝜕𝜔

phase BW Δ𝜔 ≈𝜙𝑡𝑜𝑙

𝜏𝑔 𝜔0

Transmission-type phase shifter

4

Motivation

• Design a NGD network to cascade with an equivalently matched phase shifter with an equal but positive group delay to achieve a flat phase response (zero group delay).

5

Background – NGD Circuits

NGD feedback Amplifier

Kandic, et al. (2011)

NGD & NRI Loaded TL Unit Cell

Mojahedi, et al. (2004)

Microwave NGD FET Amplifier

Ravelo, et al. (2007)

X Non reciprocal

X Narrowband

X High Return & Insertion Loss / Poor Efficiency

X Combining Gain and NGD into one stage is not beneficial

6

Background – Metamaterial TLs

Negative Refractive Index

Transmission Line (NRI-TL)

Eleftheriades, et al.

Composite Right/Left-Handed

Transmission Line (CRLH-TL)

Caloz, et al.

Passive

Broadband

Low Return loss

Low Insertion loss

Positive or Negative Phase Delay

… But Always Positive Group Delay

7

Proposal

• Design a broadband impedance matched loaded TL with a specified negative group delay, and:

– Determine relationship between NGD, Insertion Loss and NGD Bandwidth. (trade-offs)

– Minimize the frequency variation of both group delay and gain.

• Given the specifications of a phase shifter:

– Select either positive or negative phase delay on the basis of group delay minimization, and

– Combine with NGD unit cell to produce a zero group delay phase over a wideband.

8

Loaded TL Unit Cell

𝑍

𝑍0=

𝑌

𝑌0≪ 1

Metamaterial-TL (MTM-TL)

𝜃𝑇𝐿 ≪ 1

𝐿𝑇𝐿 = 𝑗𝑍0𝜃𝑇𝐿

𝐶𝑇𝐿 = 𝑗𝑌0𝜃𝑇𝐿

Host TL Loading Elements

Small host TL

Balanced Condition

𝑆 𝑀𝑇𝑀 ≈ 𝑒−𝑗𝜃𝑇𝐿 0 𝑒−𝑍 𝑍0

𝑒−𝑍 𝑍0 0

Impedance matched

and Reciprocal

9

MTM-TL Characteristics

ln 𝑆21 = −1

𝑍0

𝑅1 + 𝑅2 + ⋯+ 𝑅𝑛

𝜙21 = −1

𝑍0

𝑋1 + 𝑋2 + ⋯+ 𝑋𝑛

𝜏𝑔 =1

𝑍0 𝜕𝑋1

𝜕𝜔 +

𝜕𝑋2

𝜕𝜔 + ⋯+

𝜕𝑋𝑛

𝜕𝜔

• Insertion Losses add

• Phases add

• Group delays add

𝛾 =1

𝑍0

𝑍𝑛

𝑛

Equivalent TL

10

Lossless MTM-TL & Group Delay

• Lossless unit cells always have a positive group delay proportional to the stored energy Wav (in reactive elements)

Use 1st order MTM-TLs to minimize group delay

𝜏𝑔 =𝑊𝑎𝑣

𝑎 2 =

1

𝑍0

𝜕𝑋

𝜕𝜔> 0

𝜔𝑐 =1

𝐿𝐶, 𝑍0 = 𝐿/𝐶

11

Low-Pass & High-Pass S21 Responses

• The balanced NRI-TL is the combination of both low-pass and high-pass unit

cells (band-pass).

• To minimize its group delay, the host TL length should be minimized.

low loss

𝜙𝐿𝑃 ≈ −𝜔/𝜔𝑐

𝜙𝐻𝑃 ≈ 𝜔𝑐/𝜔

𝜔 ↑ 𝜔 ≫ 1

𝜔 ≪ 1

S21 Polar Plot

12

Proposed NGD Unit Cell

𝛾 =𝑍

𝑍0=

𝑌

𝑌0=

𝐴

1 + 𝑗𝑄 𝜔𝜔0

−𝜔0𝜔

𝐴 =𝑅𝑧

𝑍0=

𝑍0

𝑅𝑦 , 𝑄 =

1

𝑅𝑧

𝐿𝑧𝐶𝑧

= 𝑅𝑦 𝐶𝑦𝐿𝑦

, 𝜔0 =1

𝐿𝑧𝐶𝑧=

1

𝐿𝑦𝐶𝑦

NGD

S21 Polar Plot

13

NGD Unit Cell Phase and Magnitude Response

𝜏𝑔 ,𝑚𝑎𝑥 = 2𝐼𝐿𝑚𝑎𝑥

Δ𝜔𝑁𝐺𝐷

Δ𝜙𝑝𝑝 = ILmax = 𝐴

Δ𝜔𝑁𝐺𝐷 =𝜔0

𝑄

𝜏𝑛𝑔𝑑 ,𝑚𝑎𝑥 =2𝐴𝑄

𝜔0

14

Constant NGD with varying Insertion Loss

A=3dB

A=1dB

A=5dB

A=5dB

A=3dB

A=1dB

For a constant NGD, Bandwidth increases with increasing Insertion Loss

BW1

BW3

BW5

𝐼𝐿𝑚𝑎𝑥

Δ𝜔𝑁𝐺𝐷= 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡

15

Maximum Return Loss per NGD unit cell

Max. Return Loss vs. Max. Insertion LossReturn Loss vs. Frequency

• Return loss increases as Insertion loss increases

• For a low return loss, the insertion loss (and thus bandwidth-

NGD product) per unit cell must be kept sufficiently low.

16

ADS Ideal Microstrip Simulation Setup

• NGD unit cell component values are determined by specifying the phase shifters 1. centre frequency, 2. characteristic impedance, 3. NGD (to produce zero group delay) and 4. maximum Insertion Loss.

TL lengths determine

phase delay

17

Simulated -300 NGD TL Phase Shifter

±20 phase bandwidth

Unloaded TL:105 MHz

NGD: 550 MHz

• Return loss < 40dB

• Insertion Loss < 3dB

NGD

Unloaded TL

NGD

Unloaded TL

NGD

Unloaded TL

NGD Return Loss

18

Simulated -900 (two-cells) NGD TL Phase Shifter

±50 phase bandwidth

Unloaded TL: 87 MHz

NGD: 650 MHz

• Return loss < 37dB

• Insertion Loss < 8dB

NGD

Unloaded TL

NGD

Unloaded TL

NGD

Unloaded TLNGD Return Loss

NGD

unit cell

NGD

unit cell

19

-450 Two-Cell Stagger Tuned NGD Phase Shifter

±20 phase bandwidth

Unloaded TL: 105 MHz

NGD: 905 MHz

two-cell NGD unit cell 1 unit cell 2 Unloaded TL

• Return loss < 33dB

• Insertion Loss < 4dB

• Low IL ripple

input port

output port

NGD

unit cell 1

NGD

unit cell 2

20

Hybrid NRI-NGD 00 Phase Shifter

• Combination of NRI (high-pass) and NGD (lossy

resonator) into one non-symmetric unit cell.

• Low return loss (< 20 dB) & Insertion Loss (< 2.5 dB)

• Reduced size & number of components

±2o Phase bandwidth

NRI only: 79MHz

NGD-NRI: 553MHz

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Beam Squint for a Linear Series-Fed Antenna Array

to remove beam squint :

1) m=0 main lobe NRI-TL

2) equal phase and group delay NGD

𝐴𝑟𝑟𝑎𝑦 𝐹𝑎𝑐𝑡𝑜𝑟 𝐵𝑒𝑎𝑚 𝑆𝑞𝑢𝑖𝑛𝑡

𝜕𝜃

𝜕𝜔=

𝜏𝑔 − 𝜏𝑝 +2𝑚𝜋𝜔

𝜔𝑑𝐸𝑐

cos𝜃

Phase Shifter±50 beam angle

Bandwidth

-3600 Unloaded TL 27 MHz

00 NRI –TL 122 MHz

Hybrid 00 NGD NRI-TL 607 MHz

𝜕𝜃

𝜕𝜔= 0

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Experimental Setup

Rogers RT Duroid 5880 substrate (εr=2.2)

– 50Ω Microstrip TLs

RF surface mount components (0402, 0603)

– Coilcraft ceramic inductors

– Murata ceramic capacitors

– Vishay thick film resistors

Modelithics component models

– Empirical data models

– Substrate scalable, pad dimension scalable

23

-300 NGD TL Phase Shifter (3dB loss)

½ Z Y

R 8 Ω 156 Ω

L 1.5 nH 20 nH

C 16 pF 1.2 pF

component values

24

-300 NGD TL Phase Shifter (3dB loss)

Summary• ±20 phase bandwidth: 610MHz – 1240MHz (63%)

450% increase over unloaded TL (14%)• Measured Insertion Loss < 3.1dB• Measured Return loss < 20dB

25

-300 NGD TL Phase Shifter (2dB loss)

½ Z Y

R 5.9 Ω 210 Ω

L 1 nH 33 nH

C 14 pF 0.8 pF

component values

26

-300 NGD TL Phase Shifter (2dB loss)

Summary• ±20 phase bandwidth: 680MHz – 1160MHz (51%)

364% increase over unloaded TL (14%)• Measured Insertion Loss < 2.12 dB• Measured Return Loss < 20dB• Less Ins. Loss but also less NGD bandwidth

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27

00 NGD NRI-TL Phase Shifter

½ Z Y NRI

R 10 Ω 100 Ω -

L 3.6 nH 30 nH 56 nH

C 11 pF 2.7 pF 27 pF

component values

28

00 NGD NRI-TL Phase Shifter

Measured NGD NRI-TL

phase error (700MHz)

= +3.60

±20 phase bandwidth

NRI-TL: 71 MHz

NGD NRI-TL: 188 MHz

Measured

• Return loss < 14 dB

• Insertion Loss < 3.37 dB

29

Conclusions

• Passive Broadband NGD Unit Cell Proposed– Frequency, Impedance and NGD scalable

– Quasi-linear phase at centre frequency

– NGD, Insertion Loss and Bandwidth trade-off identified

• NGD combined with lossless phase shifters to significantly increase phase bandwidth

• Beam Squint may only be removed entirely with NGD phase shifters.

• Experimentally verified microstrip NGD phase shifters with both positive and negative phase delays at 0.5GHz – 1.2GHz.