Design and Development of Quadrature Hybrid Coupler At

Design and Development of Quadrature Hybrid Coupler at

18-40 GHz

External Guide : Internal Guide : Presented by :

Mr. Syed Sadullah Hussaini Mrs.K.Ch.Sri Kavya Mr. B.V.Raj Gopala Rao

Scientist ‘C’ Associate Professor M.Tech ( C&R)

DLRL-Hyderabad K.L.University 10102157

Objective

• The aim of the project is to design and develop hybrid coupler with differentconfigurations at 26.0 – 40.0 GHz and 18.0 – 40.0 GHz.

• Following configurations have been investigated and the effectof DGS has been studied (As DGS makes the design compact and sharpens the cutoff).

Single section Branch line coupler

Cascaded Branch line coupler .

5 – Section branch line coupler.

5 – Section branch line coupler with DGS effect.

Re – entrant mode Coupler or Hopfer Coupler.

• Microwave Tools used :

Advanced Design system (ADS)

ANSOFT Designer

Microwave Components• Microwave components can be categorized by the type of circuit elements

which are used: discrete (or lumped) versus distributed

• Lumped elements in generic electronic circuit such as inductors andcapacitors are generally available only for a limited range of values and aredifficult to implement at microwave frequencies

• Distributed elements are formed using sections of transmission line.Depending on the layout (line width, geometry, etc.) sections of line canbehave very much like capacitors, inductors, or a combination of both

• Advantages of distributed components:» At high frequencies high performance discrete elements must be very small

and can be difficult to manufacture and assemble» Designs using distributed elements can often be made more cheaply, and may

perform better at high frequencies

Continued…..• The key difference between circuit theory and transmission line theory lies in

electrical size.

• A very general distinction between lumped and distributed is:» Lumped elements have a physical size <<<<<<λ» Distributed elements have a physical size comparable to λ

• Thus we can say that a transmission line is a distributed-parameter network where voltages and currents can vary in magnitude and phase over the length of the network.

• Here we will focus on microstrip Transmission line microwave circuits

• One drawback to distributed elements is that the characteristics are highly frequency-dependent

• Another disadvantage of using distributed elements at lower frequencies is larger sizes(because of larger wavelengths at lower freq.'s)

Transmission Line Review

Transmission Line Terminated with Zo

High-Frequency Device Characterization

Reflection Parameters

Transmission Parameters

Low-Frequency Network Characterization

Why use S-parameters??

Measuring S-parameters

Microstrip Transmission line

Its an inhomogeneous Transmission Line structure

Employs a high dielectric substrate, the EM field is concentrated very tightly near the conductor in the free-space region, avoiding excessive radiation loss.

Advantages:» Suitable for etching» ease of mounting components» Accessibility for circuit tuning

Electric E and Magnetic H field lines for fundamental Quasi-TEM in Microstrip

1 ,

)/444.1( ln667.0393.1)(120

1 ),4

8ln(60

eff

0

hw

hwhw

hw

hw

wh

Z eff

Synthesis procedure: Give Z0 to find w / h.

rrrrr

rrr

ZBZA

hwBBB

hw

hw

0

0

2A

A

2377 ),11.023.0(

11

21

60 where

2 ,61.039.0)1( ln2

1)12( ln12

2 2e

8e

Analysis procedure: Give w / h to find eeff and Z0.

)/( 12121

21

whrr

eff

Formulas for Quasi-TEM Design Calculations

Hybrid Coupler

A Hybrid is a passive device which couples part of the transmission power using two transmission lines.Difference between Directional coupler and Hybrid coupler.Applications

To design a Hybrid coupler: Planar Microstrip ConfigurationWide band of 26.0 – 40 GHz and 18.0-40.0GHzTight coupling of -3dBReturn loss > 20dBIsolation >20dB

Applications of Hybrid Couplers :

• Balanced Amplifiers

• Balanced Mixers

• Image rejection mixers

• Phase shifters

• Attenuators

• Beam forming Networks

Direction of Arrival (DOA)Image Rejection Mixer

Balanced Amplifier

Design of -3dB Coupler at 26 – 40 GHz

Z1 , Z2 Series and branch line impedances.

Even and Odd mode Analysis.

Conventional BLC has a limited bandwidth of 15%.

Bandwidth can be enhanced by cascading multiple sections.

Single Section Branch-line Coupler 3-Section branch line Coupler

Even and Odd Mode Analysis

.

Decomposition of the branch-line coupler into even- and odd-mode excitations.(a) Even mode (e). (b) Odd mode (o).

Proposed Design

Port 1 – Input port Port 3 - Direct port

Port 2 – isolation port Port 4 - Coupled port

Z1 = 35.35 Ω , Z2 = 120.7 Ω

Effects of High Frequencies

Effects of Discontinuities

Simulation Results and Discussions• Performance was evaluated using Ansoft Designer microwave Tool.

• Substrate characteristics: Dielectric constant εr = 2.2 Height H = 10mil (0.254mm) Loss tangent δ = 0.001

• Electrical characteristics: Characteristic impedance Z0 = 50Ω Physical Dimensions of the structure Electrical length = 90 degrees Design frequency f0 = 33GHz

Return loss for 1-Section, 3-Section and 5-section branch line couplers

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-37.50

-35.50

-33.50

-31.50

-29.50

-27.50

-25.50

-23.50

-21.50

dB(S

(Por

t1,P

ort1

))Ansoft Corporation PlanarEM1XY Plot 1

m5

m6

m7

m8

m9

Curve Info

dB(S(Port1,Port1))Setup 1 : Sw eep 1

Name X Y

m5 26.0000 -20.0386

m6 28.2000 -37.1955

m7 32.4000 -20.9531

m8 37.4000 -28.2521

m9 40.0000 -23.9196

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-32.50

-30.50

-28.50

-26.50

-24.50

-22.50

-20.50

-18.50

dB(S

(Por

t1,P

ort2

))

Ansoft Corporation PlanarEM1XY Plot 5

m1

m2

m3

m4

m5

Curve Info


Name X Y

m1 26.0000 -19.6803

m2 28.4000 -32.4312

m3 32.8000 -21.0107

m4 37.4000 -27.4584

m5 40.0000 -23.0166

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-4.50

-4.25

-4.00

-3.75

-3.50

-3.25

-3.00

-2.75

-2.50

Y1


m1

m2

m3

m4

m5

m6

m7

Curve Info

dB(S(Port1,Port3))Setup 1 : Sweep 1

dB(S(Port1,Port4))Setup 1 : Sweep 1

Name X Y

m1 26.0000 -4.3967

m2 29.6000 -3.4670

m3 35.8000 -2.9964

m4 40.0000 -2.8619

m5 26.0000 -2.7304

m6 35.8000 -4.1515

m7 40.0000 -4.4356

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-300.00

-250.00

-200.00

-150.00

-100.00

-50.00

0.00

50.00

100.00

ang_

deg(

S(P

ort1

,Por

t3))-

ang_

deg(

S(P

ort1

,Por

t4))

[deg

]


m1

m2 m3 m4

m5

m6m7

Curve Info

ang_deg(S(Port1,Port3))-ang_deg(S(Port1,Port4))Setup 1 : Sw eep 1

Name X Y

m1 31.2000 -268.5467

m2 34.8000 91.5605

m3 37.8000 92.3388

m4 40.0000 92.6918

m5 30.4000 -268.4030

m6 26.8000 90.9216

m7 26.0000 90.0890

Plot for Return loss (S11) Plot for Isolation (S12)

Plot for Coupling between S13 & S14 Plot for Phase Difference between S13 & S14

Defective Ground Structure ( DGS )

• DGS is an etched periodic or non-periodic structure.

• It is a slot in the ground plane which increases effective capacitance andinductance.

• It acts as slow wave structure and also increases the characteristicimpedance.

• Its equivalent circuit is parallel LC ( Tank ckt ).

• Disadv : Radiation from the periodic etched structures.

DGS in ground plane DGS equivalent circuit

5-Section BLC with DGS

5-Sec BLC 3-D Top view

5-Sec BLC 3-D side view

5-Sec BLC with DGS Layout

Comparison of physical dimensions of 5-Section BLC with and without DGS

Results and Discussions

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-4.40

-4.20

-4.00

-3.80

-3.60

-3.40

-3.20

Y1


m1

m2

m3

m4

m5

m6

Curve Info



Name X Y

m1 26.0000 -3.8344

m2 32.0000 -3.6520

m3 40.0000 -4.3821

m4 26.2000 -3.3252

m5 32.0000 -4.1423

m6 40.0000 -4.3194

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-37.50

-35.00

-32.50

-30.00

-27.50

-25.00

-22.50

-20.00

-17.50

-15.00Y

1Ansoft Corporation PlanarEM1XY Plot 1

m3

m4

m5

m6

m7

m8

Curve Info



Name X Y

m3 26.0000 -19.6597

m4 32.6000 -36.3321

m5 40.0000 -18.6091

m6 26.0000 -20.1005

m7 32.8000 -34.6351

m8 40.0000 -18.8491

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-300.00

-250.00

-200.00

-150.00

-100.00

-50.00

0.00

50.00

100.00

ang_

deg(

S(P

ort1

,Por

t2))

-ang

_deg

(S(P

ort1

,por

t4))

[deg

]

Ansoft Corporation PlanarEM1XY Plot 4m1

m2m3

m4m5m6

Curve Info

ang_deg(S(Port1,Port2))-ang_deg(S(Port1,port4))Setup 1 : Sw eep 1Name X Y

m1 30.0000 92.1833

m2 40.0000 -263.4659

m3 40.0000 -263.4659

m4 26.4000 90.8551

m5 26.0000 90.7005

m6 26.0000 90.7005

26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00F [GHz]

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

dB(S

(Por

t1,P

ort2

))-d

B(S

(Por

t1,P

ort4

))


m1

m2

m3

m4

m5

Curve Info

dB(S(Port1,Port2))-dB(S(Port1,Port4))Setup 1 : Sw eep 1

Name X Y

m1 26.0000 -0.5483

m2 29.2000 0.2055

m3 32.4000 0.4987

m4 37.0000 0.2384

m5 40.0000 -0.0628

Coupled line theory• When two unshielded lines are placed close together, power can be

coupled between the lines due to the interaction of the EM fields.

• Coupled lines has perfect matching and directivity.

• Exits two types of propagation modes :

Even mode : Currents with same amplitude and in same direction.

odd mode : Currents with same amplitude and in opposite direction.

• Even mode :

• Odd mode :

Design of -3dB coupler at 18-40 GHz

Configurations :

Edge Coupled lines .

Broad side coupled lines.

Vertically installed planar coupled lines.

Off set parallel coupled lines.

Problems :

• Tight coupling requires narrow spacing between coupled lines which is

practically unrealizable.

• In Microstrip , even and odd mode phase velocities are not equal which

effects the directivity ,return loss and isolation

• High frequency effects

-3dB Coupler configurations:

• Lange Couplers

• Tandem couplers

• Re-entrant couplers

Phase velocity compensation techniques for Microstrip lines :

• By adding lumped capacitances at the ends of the coupled lines.

• By adding a dielectric overlay on top of the coupled lines.

• By using Wiggly lines.

Coupler with tight coupling of -3dB has been designed using re-entrant configuration with multiple dielectric layers to compensate narrow spacing between the coupled lines and also to equal the even and odd mode phase velocities of Microstrip coupled lines.

Re-entrant coupler ( Hopfer Coupler ) design

• A , B --- inner coaxial conductors

• C --- Outer conductor

• The conductor C is at floating potential with respect to the conductors A, B and the outer conductor D.

• The transmission line between C and D is in series with the two coaxial lines contained in C, acting as a mutual coupling medium.

• Zo1 ---- Impedance between outer conductor C and ground plane D.

• Z02 ---- Impedance between inner conductors A , B and ground plane D.

Re- entrant cross section using coaxial lines

Design relations

• Even mode impedance

• Odd mode impedance

• Overall impedance

where k -- coupling factorc -- coupling (dB)

Design using Microstrip lines

• The Microstrip version of a re-entrant coupler consists of a coupled line on the

middle layer sandwiched between the floating conductor on the top layer and a

floating conductor in the rectangular ground plane slot underneath the coupled

lines at the bottom layer .

Longitudinal view

Cross sectional view

Hopfer Coupler Design in ANSOFT Designer

3 – Dimensional Views

Results and Discussions

17.50 20.00 22.50 25.00 27.50 30.00 32.50 35.00 37.50 40.00F [GHz]

-50.00

-45.00

-40.00

-35.00

-30.00

-25.00

-20.00Y

1


m1

m2

m3

m4

m5m6

m7

m8

m9

m10

m11m12

Curve Info



Name X Y

m1 18.0000 -28.7634

m2 22.0000 -46.5821

m3 27.0000 -24.6444

m4 31.0000 -27.8985

m5 39.0000 -26.2331

m6 40.0000 -25.3202

m7 18.0000 -31.0848

m8 20.0000 -48.8893

m9 24.0000 -25.5915

m10 30.0000 -28.8321

m11 39.0000 -22.7021

m12 40.0000 -21.3070

17.50 20.00 22.50 25.00 27.50 30.00 32.50 35.00 37.50 40.00F [GHz]

-4.40

-4.20

-4.00

-3.80

-3.60

-3.40

-3.20

-3.00

Y1


m1

m2

m3 m4

m5

m6

m7

m8

m9

Curve Info



Name X Y

m1 18.0000 -3.0992

m2 27.0000 -3.5284

m3 33.0000 -3.8893

m4 39.0000 -3.9161

m5 40.0000 -4.3700

m6 18.0000 -3.4219

m7 22.0000 -3.1247

m8 33.0000 -3.4766

m9 40.0000 -4.2945

17.50 20.00 22.50 25.00 27.50 30.00 32.50 35.00 37.50 40.00F [GHz]

-300.00

-250.00

-200.00

-150.00

-100.00

-50.00

0.00

50.00

100.00

ang_

deg(

S(P

ort1

,Por

t2))-

ang_

deg(

S(p

ort1

,por

t3))

[deg

]

m1 m2

m3

m4

m5 m6 m7

m8

m9 m10

m11

m12

Name X Y

m1 18.0000 -269.6665

m2 19.0000 -269.6717

m3 23.0000 90.2467

m4 26.0000 -270.0887

m5 27.0000 90.0366

m6 28.0000 90.0617

m7 29.0000 89.8954

m8 32.0000 -271.1468

m9 36.0000 89.1182

m10 37.0000 88.9733

m11 39.0000 -272.6546

m12 40.0000 85.8222

17.50 20.00 22.50 25.00 27.50 30.00 32.50 35.00 37.50 40.00F [GHz]

-0.50

-0.30

-0.10

0.10

0.30

0.50

dB(S

(Por

t1,P

ort2

))-d

B(S

(Por

t1,P

ort3

))


m1

m2

m3

m4

m5

m6

Curve Info

dB(S(Port1,Port2))-dB(S(Port1,Port3))Setup 1 : Sw eep 1

Name X Y

m1 18.0000 -0.3228

m2 22.0000 0.4239

m3 27.0000 -0.0113

m4 33.0000 0.4127

m5 39.0000 -0.4180

m6 40.0000 0.0756

Conclusion

A 3-dB five section branch line hybrid in wide frequency band using a planar Microstrip configuration.

Design satisfied the bandwidth efficiency of 42%.

Hopfer coupler in a frequency band of 18-40 GHz with a bandwidth efficiency of 75%.

Return loss of 20dB throughout the frequency band.

A tight coupling of 3±1dB.

Isolation greater than 15dB.

Phase imbalance of better than ±3°.

Amplitude imbalance of 0.5dB.

References[1] D. M. Pozar ,”Microwave Engineering”, 3rd edition. Newyork: Wiley, 1998.

[2] Andrei Grebennikov,“Power combiners, impedance transformers and directional couplers”, Summit Technical media, LLC , 2008.

[3] Rajesh Mongia,Inder Bahl,Prakash Bhatia,”Rf and Microwave Coupled line Circuits”,Artech House Publications.

[4] S.Kumar, C.Tannous, and T.Danshin ,”A Multisection Broadband Impedance Transforming Branch-Line Hybrid”,IEEE Trans.Microwave

Theory Tech vol.MTT-43,pp.2517-2523,Nov.1995

[5] G. Matthaei, L. Young, and E.Jones, “Microwave Filters, impedance Matching networks and Coupling Structures”, Mc Graw Hill Co, New

York, 1964.

[6] J.Adelman, R. Ben-Michael, S. Casp and S.Hopfer, “The design of millimetre-wave control components”, IEEE Trans. Microwave Theory

Tech, Vol 37, No.2, Feb 1989.

[7] S.B.Cohn, “The re-entrant cross section and wideband 3 – dB hybrid couplers” IEEE Trans Microwave Theory and Tech, July 1963.

[8] S. Hopfer. “A hybrid coupler for Microstrip configuration.” Int. Microwave Symp,1979, Dig., pp. 428-430.

[9] A.M.Abbosh, “Broadband parallel-coupled Quadrature coupler with floating-potential ground plane conductor”, Microwave and optical

technology Letters vol 50, No.9, Sep 2008.

[10] Steven L. March, “Phase velocity compensation in parallel coupled Microstrip,” IEEE MTT-S Dig., pp.410-412. 1982.

[11] Seymour B. Cohn, “The re-entrant cross section and wide-band 3-dB hybrid couplers,” IEEE Trans. on MTT, vol. MTT-

11, pp.254-258, July 1963.

[12] L. Lavendol and J. J. Taub, “Re-entrant directional coupler using strip transmission,” IEEE Trans. on MTT, vol. MTT-24, pp.700-

701, September 1965.

[13]Pavio, A. M., and Sutton, S. K., “A Microstrip re-entrant mode Quadrature coupler for hybrid and monolithic circuit applications,” IEEE

MTT-S Symp., Dig., pp. 573-576, 1990. Authorized

Thank you……………..

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Design and Development of Quadrature Hybrid Coupler At

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