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Home » Researches » Mitigation of Passive Intermodulation on Planar Microstrip Circuits with Distributed Current-Driven Nonlinearities

Mitigation of Passive Intermodulation on Planar Microstrip Circuits with Distributed Current-Driven Nonlinearities

Dr. Senad Bulja 06/02/2023Download Here

Passive RF components, such as duplexers, filters and antennas, are essential elements of base stations (BS) for wireless communications. Although these components are commonly regarded as linear in low and medium power applications, their behaviour in the systems operating at high-powers exhibits appreciable electrical nonlinearity, which results in the generation of harmonics and spurious intermodulation products. Such a form of intermodulation distortion that occurs in passive components is called passive intermodulation (PIM) [1].

It was experimentally demonstrated that printed circuit board (PCB) components, currently widely used in high power applications, such as radar and telecommunication systems, could be a potential source of unacceptable generation of PIM distortions [2]. From the physical point of view, PIM generation on microstrip circuits is characterized by several important features, such as multiple competing nonlinear sources and their distributed nature. This leads to additional issues during the design and manufacturing process of PCB components and makes their nonlinear properties commonly unpredictable. For these reasons it is of paramount importance to develop new means of PIM mitigation. Preferably, such means should be post-production oriented in order to retain the low cost of PCB manufacture, and also due to the need of retrofitting into existing designs.

This paper presents a simple technique for effective mitigation of passive intermodulation generated in planar microwave circuits fabricated on commercial printed circuit board laminates. The proposed procedure is based on covering the edges of a microstrip lines with a thin layer of a material of a high dielectric constant, such as tantalum pentoxide (Ta2O5) which reduces the electric field intensity (displacement field) and, hence, nonlinear distortions due to high current density, Fig. 1. The obtained results indicate that an adequate choice of electrical and geometric parameters of the coating dielectric material result in a significant mitigation of passive intermodulation (over 10 dB), while small signal scattering parameters of the measured circuit remain constant, Fig. 2. 

Fig. 1. Sol deposition (left) and UV curing (right)
Fig. 1. Sol deposition (left) and UV curing (right)
Fig. 2. Measured S-parameters (left) and reverse PIM3 level (right) of the tested microstrip line before and after Ta2O5 film coating
Fig. 2. Measured S-parameters (left) and reverse PIM3 level (right) of the tested microstrip line before and after Ta2O5 film coating

[1] P. L. Lui, “Passive intermodulation interference in communication systems,” Electronics & Communication Engineering Journal, vol. 2, no. 3, pp. 109-118, June 1990.

[2] A. G. Schuchinsky, J. Francey and V. F. Fusco, “Distributed sources of passive intermodulation on printed lines,” in Proc. 2005 IEEE Antennas and Propagation Society International Symposium, Washington, DC, 2005, pp. 447-450.

 

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Profile & Bio

Senad Bulja, Ph.D., FIET, SMIEEE 

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PROFESSIONAL Profile

  • Accomplished career of over 19 years demonstrating consistent success as a Researcher, Leader and Mentor in the Wireless industry research environment.
  • Excellent Scientific contributions in the field of RF, EMC and telecommunications with 4 Nature Journal publications and over 70 peer-reviewed articles and conference papers
  • Strong leadership skills demonstrated by leading Ph.D. level educated cross-continental and cross-departmental teams to successful project execution.  
  • Proven Strategic Business Impact – introduced own developed technology into Nokia’s future technology roadmap (RF filters) and business transfer of the smart surface technology. 
  • Creative, internationally awarded and well-driven inventor with over 70 filed patents in the area of hardware for Radio Frequency (RF), Wireless Sensor Networks (WSN), Internet of Things (IoT) and wireless systems architectures. E.g. Nokia patent award entitled: “A top inventor in implementation patent first filings”, 2020.
  • Significant contribution in the identification of high revenue IP assets and leadership on the creation of Nokia’s patent portfolio roadmap. 
 

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