This special issue of the International Journal of Microwave and Wireless Technologies is dedicated to topics discussed during the 20th Bi-Annual French National Microwave Days (20th JNM). This 20th edition was held at “Le Palais du Grand Large” in Saint-Malo, France, on 16–19 May 2017. It was organized by IETR (Institute of Electronics and Telecommunications of Rennes) and sponsored by THALES/THALES Alenia Space (Platinium sponsor), three CEA entities (CEA-Gramat, CEA-Cestas, and CEA-Leti), CNES, DICONEX, GDR Oxyfun, and KEYSIGHT Technologies.

This very successful event welcomed 515 conference attendees, both from France and abroad. The technical program, through oral and poster sessions, focused on the following topics: “Antennas and Propagation”, “Passive Components”, “Active Components”, “Systems and Associated Processing”, and “Emerging Technologies and Functional Materials”. The 20th JNM was preceded by a 1-day special topic conference on two different themes: “Millimetre waves: from the general public to science” and “Electromagnetic modelling for antennas”.

The scientific committee of the 20th JNM was chaired by Professor Eric Kerhervé (IMS, Bordeaux) with the Vice President, Professor Ala Sharaiha (IETR). A total of 295 papers of a high technical level were presented – 144 during the 32 oral sessions, and 151 in 16 poster sessions – to which must be added five papers presented by invited renowned people. A specific exhibition area hosted 19 exhibitors during the 3 days: ACTIA Telecom, ALTAIR, AMG Microwaves, ANRITSU, ANSYS, AR France, CST, DICONEX, ELHYTE, EuMA, FI Science, GTID, IHP Microelectronics, INOVEOS, MB Electronique, ROHDE & SCHWARZ, TECH INTER, TEKTRONIX, and VERSYS. The local organizing committee, with a team of many enthusiastic volunteers, was chaired by Professor Ala Sharaiha. The scientific organization was conducted by Professor Raphaël Gillard, Dr. Philippe Besnier, and Dr. Christophe Bourlier.

The 20th JNM event was also supported by the European Microwave Association (EuMA), by the European Association on Antennas and Propagation (EurAAP), and jointly by the Métivier Foundation and ESIR with three best paper awards. The recipients were:

EuMA award:

A. Crunteanu, L. Huitema, C.A. Mjema, S. Hang Wong, J.C. Orlianges, C. Guines, and D. Passerieux for their communication entitled “Commutation optique bistable des matériaux à changement de phase: demonstration d'une antenne agile dans le domaine millimétrique”.

EurAAP award:

L. Batel, J.F. Pintos, L. Rudant, and K. Mahdjoubi for their communication entitled “Réseau d'antennes compact, super directif et large bande associé aux éléments non-Foster”.

Métivier Foundation and ESIR award:

Y. Veyrac, F. Rivet, and Y. Deval for their communication entitled “Interface de sérialisation 10 Gb/s pour convertisseur numérique/analogique sur-échantillonné à faible consommation”.

This special issue of the International Journal of Microwave and Wireless Technologies, published by Cambridge University Press in collaboration with EuMA, covers the five topics with papers selected from the 19 best papers presented at the 20th JNM Conference. The authors were requested to submit an extended English version of their papers, six submitted their contributions and 20 international reviewers agreed to review them. Finally, five of those papers were found suitable for publication in this special issue. We wish to acknowledge all the authors for submitting their papers and all the reviewers for their in-depth evaluation from July to December 2017. We hope that this special issue will be enjoyable and for interest to the readers through various topics in the microwave fields developed in France, and also that they will find extensive and useful information for their own research activities.