ULTRA WIDEBANDTAPERED

DIVIDER/COMBINER

Bilkent University Department of Electrical and Electronics Engineering

Okan Ünlü

Advisor: Abdullah Atalar

Contents

• Literature• What is a power divider?• Examples of power dividers• Tapered Lines

• Even mode analysis• Design of a tapered line• Improvement of the

tapered lines

• Odd mode analysis• 4 methods for the isolation

resistors• Odd mode bandwidth

• Combined Structure• Schematic Simulation• EM simulation• Implemented Design• Continuous Isolation

• Results• Design Guideline

Contents

• Literature• What is a power divider?• Examples of power dividers• Tapered Lines

• Even mode analysis• Design of a tapered line• Improvement of the

tapered lines

• Odd mode analysis• 4 methods for the isolation

resistors• Odd mode bandwidth

• Combined Structure• Schematic Simulation• EM simulation• Implemented Design• Continuous Isolation

• Results• Design Guideline

Literature – Power Dividers

• Power dividers/combiners are three port devices• Reciprocal• Matched• Lossless

• Cannot achieve all at the same time!• Examples:• Circulator: Not Reciprocal• T-junction: Not matched• Resistive divider: Lossy

Literature – Wilkinson Power Divider • Wilkinson

Divider/Combiner• Commonly used• Two quarter wavelength

lines• Single Isolation resistor• Narrowband• Reciprocal and Matched• Lossy ??

• Lossy in one direction!

The even mode odd mode analyses

Symmetry Plane(Open circuit)

Odd Mode

Isolation

Other Dividers

• Other Power Divider/Combiner• T-junction• Magic Tee• 3 dB Hybrid Couplers• Rat race couplers• Hybrid Transformers• Resistive dividers

Tapered Lines

• Real impedance matching• Half-wavelength• Large size – quarter wave transformer

• No upper frequency limit

Tapered Lines

• Exponential Taper• Klopfenstein Taper• Triangular Taper

Figure of Merit

• Better bandwidth • N-Section Wilkinson

• Size• Quarter wave at the lowest pass band frequency

Contents

• Literature• What is a power divider?• Examples of power dividers• Tapered Lines

• Even mode analysis• Design of a tapered line• Improvement of the

tapered lines

• Odd mode analysis• 4 methods for the isolation

resistors• Odd mode bandwidth

• Combined Structure• Schematic Simulation• EM simulation• Implemented Design• Continuous Isolation

• Results• Design Guideline

Even mode Analysis of the Proposed Divider• Tapered Line• Exponential Taper• Quarter wavelength

• Exponential Taper Equations

Tapered Line • 100 Ω to 50 Ω Exponential Tapered Line Reflection

Tapered Line • Can be simplified with N section transmission lines

Tapered Line• Design with @ 1 GHz • Simulation• Lower frequency should be improved• Has an upper frequency limit

Tapered Line – EM Structure• Microstrip Structure• Width of each section calculated• Total length calculated• Structure established in CST Microwave Studio

Tapered Line – EM Simulation

Tapered Line – Smith Chart

• Input has some inductance at lower frequencies.

• Compensate @1 GHz

Improved Tapered Line

• A series capacitance• • and

• Place a series capacitance to the input side than the bandwidth is improved.

Improved Tapered Line

• Lower Frequency side

Contents

• Literature• What is a power divider?• Examples of power dividers• Tapered Lines

• Even mode analysis• Design of a tapered line• Improvement of the

tapered lines

• Odd mode analysis• 4 methods for the isolation

resistors• Odd mode bandwidth

• Combined Structure• Schematic Simulation• EM simulation• Implemented Design• Continuous Isolation

• Results• Design Guideline

Odd mode analysis

• Same as N section Wilkinson• There are N resistors• Power coming in from port should be dissipated

Equal power dissipation method• Suggestion:

• Use schematic optimizer• Cohn approximations

• Small reflections does not apply!• Chebychev matching is not possible• Each resistor should dissipate same power

• There is a frequency that all intermediate impedances are real

• Each TL is a quarter wavelength transformer

Equal power dissipation method

•

Equal power dissipation method

Equal power dissipation method

Equal power dissipation method

Equal power dissipation method

Linear Variation Method

• Empirical Method

Linear Variation Method

Bandwidth Improvement

• Empirical method• R(1) has the most effect on bandwidth• as an improvement factor

Compared Bandwidths

N

Linear variation method Equal power dissipation method Literature

BW (-20 dB) BW with (-20 dB) BW (-20 dB) BW with

(-20 dB)

Chebychev based

Wilkinson BW (-20dB)

Cohn's BW

(-25 dB)

2 3.32 1.3 3.56 2.81 1.20 2.93 2.75 2.003 5.01 1.6 5.66 5.08 1.55 5.64 4.25 3.004 6.68 1.9 7.83 6.84 1.90 8.11 5.80 4.005 8.38 2.15 9.99 8.70 2.15 10.64 7.40 -6 10.06 2.5 12.21 10.43 2.35 13.09 9.00 -7 11.72 2.75 14.41 12.21 2.55 15.46 10.59 10.008 13.42 3.05 16.65 13.97 2.75 17.82 12.21 -9 15.11 3.4 18.89 15.72 3.00 20.37 13.83 -

10 16.76 3.8 21.13 17.48 3.15 22.62 15.46 -11 18.52 4.1 23.36 19.15 3.30 24.97 17.06 -12 20.09 4.1 25.41 20.83 3.50 27.31 18.76 -13 21.78 4.25 27.57 22.62 3.70 29.51 20.37 -14 23.55 4.6 29.81 24.34 3.95 32.07 21.94 -

Compared Size and FoM

NLinear variation

methodImproved BW

linear variation method

Equal power dissipation

method

Improved BW equal power dissipation

method

Chebychev based Wilkinson Cohn's

L' FoM L' FoM L' FoM L' FoM L' FoM L' FoM2 0.23 14.36 0.22 16.24 0.26 10.73 0.25 11.54 0.27 10.31 0.3 6.003 0.25 20.06 0.23 25.10 0.25 20.57 0.23 25.01 0.29 14.88 0.4 8.004 0.26 25.68 0.23 34.53 0.26 26.78 0.22 36.92 0.29 19.72 0.4 10.005 0.27 31.44 0.23 43.91 0.26 33.76 0.21 49.55 0.30 24.86 - -6 0.27 37.11 0.23 53.73 0.26 39.73 0.21 61.48 0.30 30.00 - -7 0.28 42.63 0.23 63.42 0.27 46.05 0.21 72.67 0.30 35.07 0.3 31.438 0.28 48.36 0.23 73.48 0.27 52.26 0.21 83.85 0.30 40.32 - -9 0.28 54.11 0.23 83.46 0.27 58.39 0.21 96.77 0.30 45.58 - -

10 0.28 59.51 0.23 93.49 0.27 64.62 0.21 106.89 0.30 50.89 - -11 0.28 65.70 0.23 103.43 0.27 70.14 0.21 117.88 0.30 56.02 - -12 0.28 70.64 0.23 111.86 0.27 75.76 0.21 128.82 0.30 61.78 - -13 0.29 76.30 0.23 121.20 0.28 82.23 0.21 138.56 0.30 66.97 - -14 0.29 82.57 0.23 131.24 0.28 88.10 0.21 151.54 0.31 71.90 - -

Power Handling Capacity

• Previously,• Equal power dissipation• Linear variation• Improved bandwidth equal power dissipation• Improved bandwidth linear variation

• Power handling capacity?? • Power dominated with one of the resistors

Power Handling Capacity

• Equal Power Dissipation

Power Handling Capacity

• Linear Variation

Power Handling Capacity

• Improved Bandwidth Equal Power Dissipation

Power Handling Capacity

• Improved Bandwidth Linear Variation

Power Handling Capacity

• Wilkinson Divider

Power Handling Capacity

Contents

• Literature• What is a power divider?• Examples of power dividers• Tapered Lines

• Even mode analysis• Design of a tapered line• Improvement of the tapered

lines

• Odd mode analysis• Isolation resistors• 4 methods for the isolation

resistors• Odd mode bandwidth

• Combined Structure• Schematic Simulation• EM simulation• Implemented Design• Continuous Isolation

• Results• Design Guideline

Combined Structure

• Schematic model of new power divider/combiner

Combined Structure

𝐵𝑊=14.60.97

=15.05

Wilkinson divider

• Schematic model of Wilkinson Divider

Wilkinson divider

𝐵𝑊=14.751.25

=11.8

EM model

• Proposed Structure

EM model

• Resistors with surface resistive layers • Ohmic sheet

•

Resistor

A

B

EM model

• CST microwave Studio

EM Model Practical Problems• Capacitor can not be implemented in EM• It is necessary to know internal structure of capacitor

𝐵𝑊=14.531

=14.53

Implemented Design

• Instead of the surface resistive materials, discrete resistors are used

Implemented Design

• Network Analyzer Outputs

Continuous Isolation Resistor• Filled the gap with surface resistive material

Continuous Isolation Resistor50Ω /𝑠𝑞

Zeven(x)Zeven(x-dx)Zeven(x+dx)

dxdxdx

Zeven(x)Zeven(x-dx) Zeven(x+dx)

Even mode Loss

Continuous Isolation Resistor1000Ω /𝑠𝑞

Contents

• Literature• What is a power divider?• Examples of power dividers• Tapered Lines

• Even mode analysis• Design of a tapered line• Improvement of the tapered

lines

• Odd mode analysis• Isolation resistors• 4 methods for the isolation

resistors• Odd mode bandwidth

• Combined Structure• Schematic Simulation• EM simulation• Implemented Design• Continuous Isolation

• Results• Design Guideline

Conclusion

• Improved tapered line design with quarter wavelength• Four different methods for the isolation resistor

• Linear Variation• Equal Power Dissipation• Improved Bandwidth Linear Variation• Improved Bandwidth Equal Power Dissipation

• Combined Structure• Better BW with same size N section Wilkinson divider• Explanation to Even mode loss• Continuous Isolation Resistor

Design Guide Line

• Decide frequency Bandwidth and • Design a Tapered Line for frequency• Improve Tapered Line with a capacitor to • Decide Isolation Resistors• Simulate Schematic model• Construct EM model and Optimize

References

• [1] D. M. Pozar, Microwave Engineering. Wiley-IEEE Press, 2011.• [2] E. Wilkinson, \An n-way power divider," IRE Trans. on Microwave Theory and Techniques,

vol. 8, pp. 116 { 118, 1960.• [3] S. B. Cohn, \A class of broadband three-port tem-mode hybrids," IRE Trans. on

Microwave Theory and Techniques, vol. 19, pp. 110 { 116, 1968.• [4] J. C. Kao, Z. M. Tsai, K. Y. Lin, and H. Wang, \A modied Wilkinson power divider with

isolation bandwidth improvement," IEEE Transactions on Microwave Theory and Techniques, pp. 2768{2780, 2012

• X. P. Ou and Q. X. Chu, \A modied two-section uwb wilkinson power divider," 2008 International Conference on Microwave and Millimeter Wave Technology Proceedings, ICMMT, pp. 1258{1260, 2008.

• [6] O. Ahmed and A. R. Sebak, \A modied wilkinson power divider/combiner for ultrawideband communications," IEEE Antennas and Propagation Society, AP-S International Symposium, 2009.

• [7] A. Wentzel, V. Sayed, and G. Boeck, \Novel broadband wilkinson power combiner," European Microwave Conference, pp. 212{215, 2008

• [8] U. H. Gysel, \A new n-way power divider/combiner suitable for highpower applications," Microwave Symposium, 1975 IEEE-MTT-S International, pp. 116 118, 1975.

Thank you!

Questions?

Reciprocal Network

• A reciprocal network is one in which the power losses are the same between any two ports regardless of direction of propagation (scattering parameter S21=S12, S13=S31, etc.)

• A network is known to be reciprocal if it is passive and contains only isotropic materials. Examples of reciprocal networks include cables, attenuators, and all passive power splitters and couplers.

• Non reciprocal device: Isolator, Circulator ()• Isotropy comes from the Greek iso, for equal (as in isolateral

triangles) and tropos, for direction. Isotropy means that a particular material property is equal in all directions (X, Y and Z). Anisotropy means that the material property might vary depending on direction.

3 port device

Manufacturing Problems of Ohmic sheet• Used in thin film and thick film processes• Only and its multiples• Very thin lines are problematic• PCB needs additional chemical processes• Long lead times

Analytical results for Capacitor• Future work• Find :

• Improving isolation bandwidth [2]• Improved bandwidth 2 section [3]

Other Dividers Based on Wilkinson Divider/Combiner

Tapered Line on Microstrip

𝑤 (𝑥 )=𝑎𝑡 2+𝑏𝑡+𝑐

Small reflections

• In the odd mode does not apply.

• Some of the power is lost in each section• Monotonically increasing/decreasing