A review of temperature compensation techniques 2014 lisi_v01

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

Marco Lisi | 27/11/2014 | Slide 2


Summary

• For on-board satellite applications, the performance over temperature of microwave resonators and filters is an important driver in the design;

• 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);

• 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.



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.



CTEs of Filter Materials



Invar Drawbacks

• High density (8050 kg/m3 as compared to the Aluminium 2700 kg/m3);

• Poor machinability; • Low thermal conductivity (more than one order of

magnitude lower than Aluminium); • Poor electrical conductivity (in order to achieve a

high Q value, it is essential to silver plate an invar cavity);

• Is an iron-nickel alloy (i.e., some sort of stainless steel), so it tends to generate PIMs.



Constrained-Expansion Cavity Resonator



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



Dielectric Materials in DROs and Cavity Filters



PCB (Microstrip) Microwave Filters



Temperature Controlled (Heatpipe) Filter



Temperature Compensated Microstrip Filter



Temperature Compensation of Coaxial Resonators

𝜔𝜔0C = 1

𝑍𝑍0 𝑡𝑡𝑡𝑡 𝜗𝜗

1 + 𝛼𝛼∗ 𝑡𝑡𝑡𝑡𝜗𝜗 = 𝑡𝑡𝑡𝑡[𝜗𝜗 1 + 𝛼𝛼2𝑇𝑇 ]

𝛼𝛼∗= 𝛼𝛼1 +𝐿𝐿2𝐿𝐿1

(𝛼𝛼1 − 𝛼𝛼2)



Temperature Compensated Combline Filter



Re-entrant Cap Temperature Compensated Filter



Temperature Compensated TE011 Cavity Resonator



𝑻𝑻𝑻𝑻𝟎𝟎𝟎𝟎𝟎𝟎 Resonant Mode



Bi-Metal Technology: John “Longitude” Harrison



Ku-Band, Pseudo-Elliptic, Four-Poles Filter Configuration



Aluminium Filter Over Temperature (∆T≅60°C)



Compensated Filter Over Temperature (∆T≅60°C)



Conclusion

Microwaves ≠

Microwaves are

or



A review of temperature compensation techniques 2014 lisi_v01

Technology

esa unclassified

marco lisi micro

thermal control techniques

use of materials

high thermal stability

thermal excursions

thermal drift3

cavity filters