University of Oulu
Kuronen, V. (Veli).
Passive intermodulation tester characteristics.
Degree: 2020, University of Oulu
Abstract. Passive intermodulation (PIM) is a severe issue for base transceiver stations. It can cause issues to the receiver of the device or to nearby devices if power levels are high enough. In the past, there have been many studies on the PIM, mostly concerning on modelling and mitigation of PIM. In this thesis, 3rd and 5th order forward PIM levels are measured and analysed from base station filters to determine if they are good enough for receiving of low-level signals. Also, used PIM test setup is simulated with modified component parameters for finding output third order intercept point (OIP3) threshold values of each component for which the setup still provides accurate enough results. Also, noise level calculations and cost estimation of typical PIM test setup is presented.
PIM products were measured with accurate test setups that had residual PIM levels clearly below measured levels. As PIM performance often varies with time all measurements were repeated several times. The best unit out of all 10 measured devices under test (DUTs) had 100 % pass rate and less than 2.5 dB standard deviation. Results were also more than 8.5 dB over the limit in average. All the results were calculated from all measurement samples of DUTs. There were 4 – 16 of measurements per DUT. The worst unit had 25 % pass rate and PIM results that were below limit in average. PIM results suggest that high standard deviation is linked to failed results, usually. Two additional DUTs was tested for finding if the source was electro-thermal nonlinearity. The results suggest that it might have been the source, but due to low quantity of measurements, waterproof conclusion can’t be made.
There are many limiting factors in testing of PIM. First of all, the test results must be clearly above noise floor in order to see the real PIM products. Also, the test setup must have its residual intermodulation at least 10 dB below the measured PIM of DUT. Then, the measured results are considered to be accurate enough. That’s why the components of the setup have to be low-PIM. For these reasons, test setup simulations were done with AWR simulation tool in order to find the threshold values on which the setup still provides reliable test results for each test setup components. It was found out that the combiner should have the highest OIP3 value, of at least 61.3 dBm when ≈ 40 dB notch filter was used before DUT at the measured 3rd order PIM frequency. Without notch, OIP3 should be at least 73.7 dBm. Therefore, notch filter lowered the need of OIP3 by 12.4 dB. Signal generators, power amplifiers and circulators of the setup were limited by their 1 dB compression point.
As a conclusion, this thesis work was successful since the limitations of the setup were found by simulations and calculations. Also, testing and analyzing of PIM products was performed successfully with low residual levels. The theory, calculations and simulations presented in this thesis can be used in acquisition of PIM test setup components. Also, the simulation model can be…
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APA (6th Edition):
Kuronen, V. (. (2020). Passive intermodulation tester characteristics. (Masters Thesis). University of Oulu. Retrieved from http://jultika.oulu.fi/Record/nbnfioulu-202005011589
Chicago Manual of Style (16th Edition):
Kuronen, V (Veli). “Passive intermodulation tester characteristics.” 2020. Masters Thesis, University of Oulu. Accessed June 01, 2020.
MLA Handbook (7th Edition):
Kuronen, V (Veli). “Passive intermodulation tester characteristics.” 2020. Web. 01 Jun 2020.
Kuronen V(. Passive intermodulation tester characteristics. [Internet] [Masters thesis]. University of Oulu; 2020. [cited 2020 Jun 01].
Available from: http://jultika.oulu.fi/Record/nbnfioulu-202005011589.
Council of Science Editors:
Kuronen V(. Passive intermodulation tester characteristics. [Masters Thesis]. University of Oulu; 2020. Available from: http://jultika.oulu.fi/Record/nbnfioulu-202005011589