The document discusses temperature compensation techniques for microwave resonators and filters used in satellites. It describes how thermal excursions can significantly impact performance and discusses approaches like using thermally stable materials, temperature control of the environment, and built-in compensation techniques using materials with different thermal expansion properties. Specific compensation methods covered include constrained expansion cavities, dielectric materials, heatpipes, and bimetallic technologies.

1. ESA UNCLASSIFIED - For Official Use
A Review of Temperature Compensation Techniques for Microwave Resonators and Filters
Dr. ing. Marco Lisi Micro and Millimeter Wave Technology and Techniques Workshop ESA–ESTEC, 27/11/2014

2. Marco Lisi | 27/11/2014 | Slide 2
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Summary
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For on-board satellite applications, the performance over temperature of microwave resonators and filters is an important driver in the design;
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In the satellite environment, thermal excursions can be relatively large and thermal control techniques are difficult to implement, especially in components handling of high power levels (e.g. output multiplexers);
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Temperature compensation techniques for microwave resonators and filters are often based on some degree of ingenuity, although associated to a good knowledge of the electromagnetic modeling of resonators and of the physical properties of materials.

3. Marco Lisi | 27/11/2014 | Slide 3
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Temperature Compensation Methods
1.
Using in the design of the microwave resonator or filter materials with high thermal stability, both in terms of physical dimensions and in terms of electrical characteristics (e.g. dielectric constant);
2.
Implementing some sort of temperature control of the component environment, thus removing the cause of the thermal drift;
3.
Designing the component with some built-in compensation technique, based on the use of materials with different physical and/or performance characteristics over temperature.

4. Marco Lisi | 27/11/2014 | Slide 4
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CTEs of Filter Materials

5. Marco Lisi | 27/11/2014 | Slide 5
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Invar Drawbacks
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High density (8050 kg/m3 as compared to the Aluminium 2700 kg/m3);
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Poor machinability;
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Low thermal conductivity (more than one order of magnitude lower than Aluminium);
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Poor electrical conductivity (in order to achieve a high Q value, it is essential to silver plate an invar cavity);
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Is an iron-nickel alloy (i.e., some sort of stainless steel), so it tends to generate PIMs.

6. Marco Lisi | 27/11/2014 | Slide 6
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Constrained-Expansion Cavity Resonator

7. Marco Lisi | 27/11/2014 | Slide 7
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Dielectric Materials Electrical Characteristics
Material Composition Ɛr Tgδ (10-4) TC (Ɛr) (ppm/°C) Non-Organic Dielectric Substrates Quartz SiO2 3.75 1.5 +0.5 Alumina (96%) Al2O3 10.2 2 +7.5 Barium Titanate BaTiO3 85 3 +8 Organic Dielectric Substrates Standard FR-4 Fiberglass 4.5 260 +200 Rogers Duroid 5870 PTFE Random Glass Fiber 2.33 12 -115 Rogers 4003 Woven Glass Reinforced Hydrocarbon/Ceramics 3.38 27 +40 Rogers Duroid 6002 PTFE with Ceramic Fillers 2.94 12 +12 Arlon CLTE-XT Ceramic Powder-Filled Woven Micro Fiberglass Reinforced PTFE 2.94 12 -9

8. Marco Lisi | 27/11/2014 | Slide 8
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Dielectric Materials in DROs and Cavity Filters

9. Marco Lisi | 27/11/2014 | Slide 9
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PCB (Microstrip) Microwave Filters

10. Marco Lisi | 27/11/2014 | Slide 10
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Temperature Controlled (Heatpipe) Filter

11. Marco Lisi | 27/11/2014 | Slide 11
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Temperature Compensated Microstrip Filter

12. Marco Lisi | 27/11/2014 | Slide 12
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Temperature Compensation of Coaxial Resonators
휔휔0C = 1 푍푍0 푡푡푡푡 휗휗
1+훼훼∗푡푡푡푡푡=푡푡푡푡[휗휗1+훼훼2푇푇]
훼훼∗=훼훼1+ 퐿퐿2 퐿퐿1(훼훼1−훼훼2)

13. Marco Lisi | 27/11/2014 | Slide 13
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Temperature Compensated Combline Filter

14. Marco Lisi | 27/11/2014 | Slide 14
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Re-entrant Cap Temperature Compensated Filter

15. Marco Lisi | 27/11/2014 | Slide 15
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Temperature Compensated TE011 Cavity Resonator

16. Marco Lisi | 27/11/2014 | Slide 16
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푻푻푻푻ퟎퟎퟎퟎퟎퟎ Resonant Mode

17. Marco Lisi | 27/11/2014 | Slide 17
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Bi-Metal Technology: John “Longitude” Harrison

18. Marco Lisi | 27/11/2014 | Slide 18
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Ku-Band, Pseudo-Elliptic, Four-Poles Filter Configuration

19. Marco Lisi | 27/11/2014 | Slide 19
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Aluminium Filter Over Temperature (ΔT≅60°C)

20. Marco Lisi | 27/11/2014 | Slide 20
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Compensated Filter Over Temperature (ΔT≅60°C)

21. Marco Lisi | 27/11/2014 | Slide 21
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Conclusion
Microwaves ≠
Microwaves
are
or

22. Marco Lisi | 27/11/2014 | Slide 22
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