electronics Article Influence of Aircraft Power Electronics Processing on Backup VHF Radio Systems Jan Leuchter 1,* , Radim Bloudicek 1, Jan Boril 1, Josef Bajer 1 and Erik Blasch 2 1 Faculty of Military Technology, University of Defence, 66210 Brno, Czech Republic; [email protected] (R.B.); [email protected] (J.B.); [email protected] (J.B.) 2 MOVEJ Analytics, Dayton, OH 45433, USA; [email protected] * Correspondence: [email protected] Abstract: The paper describes the influence of power electronics, energy processing, and emergency radio systems (ERS) immunity testing on onboard aircraft equipment and ground stations providing air traffic services. The implementation of next-generation power electronics introduces potential hazards for the safety and reliability of aircraft systems, especially the interferences from power electronics with high-power processing. The paper focuses on clearly identifying, experimentally ver- ifying, and quantifiably measuring the effects of power electronics processing using switching modes versus the electromagnetic compatibility (EMC) of emergency radio systems with electromagnetic interference (EMI). EMI can be very critical when switching power radios utilize backup receivers, which are used as aircraft backup systems or airport last-resort systems. The switching power electronics process produces interfering electromagnetic energy to create problems with onboard aircraft radios or instrument landing system (ILS) avionics services. Analyses demonstrate significant threats and risks resulting from interferences between radio and power electronics in airborne sys- tems. Results demonstrate the impact of interferences on intermediate-frequency processing, namely, Citation: Leuchter, J.; Bloudicek, R.; for very high frequency (VHF) radios. The paper also describes the methodology of testing radio Boril, J.; Bajer, J.; Blasch, E. Influence immunity against both weak and strong signals in accordance with recent aviation standards and of Aircraft Power Electronics guidance for military radio communication systems in the VHF band. Processing on Backup VHF Radio Systems. Electronics 2021, 10, 777. Keywords: aircraft electronics; radio navigation; electromagnetic compatibility; electromagnetic https://doi.org/10.3390/electronics interference; radio interference; power electronics 10070777 Academic Editor: Mohd. Hasan Ali 1. Introduction Received: 1 March 2021 Safety-critical avionics situations arise when a radio signal is unavailable for pilots Accepted: 20 March 2021 Published: 25 March 2021 who need commands and information for their flight as well as for air traffic controllers (ATC) who provide air traffic services in their airspace. The circumstances can be more Publisher’s Note: MDPI stays neutral serious during an approach to landing or in critical conditions when pilots and ATCs must with regard to jurisdictional claims in reliably communicate beyond standard phraseology. Such a radio signal degradation from published maps and institutional affil- avionics equipment, known as electromagnetic interference (EMI), can directly decrease safety iations. in air traffic transport, surveillance, and travel. Current avionics power systems implement power electronics devices for energy gen- eration, conversion, and distribution over electrical networks. Power electronics switching circuits can improve the efficiency performance of modern airborne power systems. The number of switched power elements in airborne systems is expected to steeply rise in Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. the next decade, where every subsystem or device working as a part of an electrical or This article is an open access article electronic aircraft system already contains or will contain power electronics. An important distributed under the terms and recent power technology is switching converters based on pulse-width modulation (PWM) conditions of the Creative Commons switching. These PWM converters are one of the fastest developing technologies that are Attribution (CC BY) license (https:// used in the modern aircraft using electric drives. Power electronics circuits for electric creativecommons.org/licenses/by/ drives allow the control of the directional flow of both data and power between sources 4.0/). and consumers backward and forward in an entire aircraft power system. Two main factors Electronics 2021, 10, 777. https://doi.org/10.3390/electronics10070777 https://www.mdpi.com/journal/electronics Electronics 2021, 10, x FOR PEER REVIEW 2 of 27 Electronics 2021, 10, 777 2 of 26 sources and consumers backward and forward in an entire aircraft power system. Two main factors participate in the power switching improvement: (1) recent high-voltage de- participatevices based in on the the power SiC (silicon switching carbide) improvement: technology (1) permit recent more high-voltage dynamical devices and reliable based oncontrol the SiC of the (silicon energy carbide) flow; technologyand (2) significantly permit more more dynamical accurate real and-time reliable monitoring control of of the the energyaircraft flow; system and power (2) significantly use [1,2]. more accurate real-time monitoring of the aircraft system powerThe use implementation [1,2]. of power electronics, including the power switching sources in real Theaeronautical implementation systems, ofneeds power to comply electronics, with includingcurrent aeronautical the power standards switching and sources their inimplement real aeronauticalation directives. systems, The needs probability to comply of occurrence with current of aeronauticalan electromagnetic standards compati- and theirbilityimplementation (EMC) hazard is directives. very low, but The the probability requirement of occurrencehighlights a of risk an assessment electromagnetic of in- compatibilityduced signal (EMC)susceptibility hazard issuch very as low, category but the Z requirementof 1800 volts highlights × meters a[3 risk]. The assessment RTCA DO of- induced160 standard signal contains susceptibility basic suchEMC asrequireme categorynts Z of and 1800 EMC volts testing× meters on aircraft [3]. The and RTCA general DO- 160test standard procedures. contains Hence, basic this EMC paper requirements brings to and attention EMC testing several on aircraftpotential and EMC general threats test procedures.caused by a Hence,switching this power paper bringssupply to and attention their effects several on potential the reliability EMC threatsof, for example, caused by th ae switchingaeronautical power backup supply system and theirwith effectsvery high on the frequency reliability (VHF of, for) services example,, which the aeronautical are not cur- backuprently well system described with veryin aeronautical high frequency standards (VHF) [3] services,. which are not currently well described in aeronautical standards [3]. 1.1. Overview of Aeronautical Radio Backup Systems 1.1. Overview of Aeronautical Radio Backup Systems As backup power systems are inseparable components in many onboard and off- As backup power systems are inseparable components in many onboard and off-board board aircraft technologies, there is a need to understand the impacts on system perfor- aircraft technologies, there is a need to understand the impacts on system performance. mance. Some backup sources are similar to the main systems, but the onboard systems Some backup sources are similar to the main systems, but the onboard systems are subject are subject to placement and weight restrictions. to placement and weight restrictions. As for radio equipment, there is the main communication very high frequency As for radio equipment, there is the main communication very high frequency (COM- (COM-VHF) radio (see Figure 1), working in the bandwidth of 117–137 (144) MHz. The VHF) radio (see Figure1), working in the bandwidth of 117–137 (144) MHz. The com- communication signal is typically designed using software-defined technology, where ra- munication signal is typically designed using software-defined technology, where radio dio frequency (RF) blocks are efficiently shielded from interferences coming from other frequency (RF) blocks are efficiently shielded from interferences coming from other elec- electronic devices; however, such shielding can increase weight, size, and other power tronic devices; however, such shielding can increase weight, size, and other power supply supply requirements (filtering, signal processing, etc.), in comparison to electronic devices requirements (filtering, signal processing, etc.), in comparison to electronic devices working inworking environments in environments without anywithout interferences. any interferences. A backup A VHFbackup communication VHF communication receiver re- is typicallyceiver is typically built as a built simple as a or simple double-heterodyne or double-heterodyne receiver inreceiver a low-dimension in a low-dimension RF design. RF Indesign. addition, In addition, there are there emergency are emergency radio devices radio devices in military in military aviation aviation as a part as of a apart pilot’s of a survivalpilot’s survival kit. These kit. These radio radio receivers receivers are based are based on regenerative on regenerative reception, reception, having having simple sim- designsple designs and and compact compact dimensions. dimensions. Likewise, Likewise, the the radio radio receivers receivers must must survive survive a a pilot’s pilot’s ejection,ejection, carrycarry theirtheir ownown powerpower source,source, andand