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An investigation into the passive intermodulation properties of space qualified materials

Mitchell, Stuart David (1997) An investigation into the passive intermodulation properties of space qualified materials. Doctor of Philosophy (PhD) thesis, University of Kent. (doi:10.22024/UniKent/01.02.85975) (KAR id:85975)


Intermodulation products are spurious frequency components which are produced when two or more signals mix in nonlinear components and devices. Particularly in multi-signal environments like those encountered on satellites, the spurious frequency components may severely degrade system performance through interference.

Nonlinearities are commonly known to exist in the active devices associated with components in transmitters and receivers. However, nonlinearities are also found in passive components and give rise to a phenomenon known as passive intermodulation interference.

This thesis describes the work undertaken during a study of passive intermodulation (PIM). The project was directed towards the characterisation of PIM in materials which are commonly used in spaceborne RF hardware. Satellite systems are particularly vulnerable to interference from passive non-linearities and little information is available to help engineers avoid the problem.

The work described includes the development of a highly sensitive PIM detection system. This involved the design and development of several custom components including connectors, band-stop filters and two different 3 dB couplers. The system was used to perform an investigation into the parameters which affect the generation of PIM signals in aerospace materials. Results are presented for measurements carried out at L-band frequencies.

An extensive review of previous studies on passive intermodulation is presented including descriptions of the nonlinear mechanisms which are most likely to occur in passive structures. The experimental results are then used to propose the mechanisms which are likely to dominate the levels of passive intermodulation in the samples tested.

The measurement system was also used to carry out measurements for the European Space Agency at the European Space Research and Technology Centre. The tests involved the detection and measurement of PIM sources in a test chamber used for characterising satellite payloads.

Item Type: Thesis (Doctor of Philosophy (PhD))
DOI/Identification number: 10.22024/UniKent/01.02.85975
Additional information: This thesis has been digitised by EThOS, the British Library digitisation service, for purposes of preservation and dissemination. It was uploaded to KAR on 09 February 2021 in order to hold its content and record within University of Kent systems. It is available Open Access using a Creative Commons Attribution, Non-commercial, No Derivatives ( licence so that the thesis and its author, can benefit from opportunities for increased readership and citation. This was done in line with University of Kent policies ( If you feel that your rights are compromised by open access to this thesis, or if you would like more information about its availability, please contact us at and we will seriously consider your claim under the terms of our Take-Down Policy (
Uncontrolled keywords: Unmanned spacecraft; satellites
Subjects: T Technology > TK Electrical engineering. Electronics. Nuclear engineering
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Engineering and Digital Arts
SWORD Depositor: SWORD Copy
Depositing User: SWORD Copy
Date Deposited: 29 Oct 2019 16:23 UTC
Last Modified: 08 Dec 2022 15:13 UTC
Resource URI: (The current URI for this page, for reference purposes)

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