This special issue of the International Journal of Microwave and Wireless Technologies is dedicated to topics discussed during the 21st Bi-Annual French National Microwave Days (21st JNM), held in Caen, France, on May 14–17, 2019. The 21st JNM Conference was co-organized by three research centers: IRSEEM (Institut de Recherche en Systèmes Electroniques Embarqués), CRISMAT (laboratoire de Cristallographie et Sciences des Matériaux), and GREYC (Groupe de Recherche en Informatique, Image, Automatique et Instrumentation). It was sponsored both by Institutional supports: CAEN la Mer, Université Caen Normandie, ESIGELEC, ENSICAEN, CNRS and GREYC and industrial supports: EMCOS, NXP Semiconductors, Keysight Technologies, EV-Technologies, Tektronix-Keithley, Rohde & Schwarz, S2P, XFAB, ROGERS Corporation, DICONEX, FABIXIS, and CISTEME. This very successful event welcomed 495 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 21st JNM was preceded by a one day special topic conference on “5G, the future very high speed mobile network” divided into two parallel sessions “Impact of 5G on Technology” and “Modelling Techniques for 5G Communications” with the contribution of CEA – LETI, NXP, OMMIC, XFAB, ANSYS, ALTAIR, AMCAD Engineering, and EV-Technologies. Professor Ala Sharaiha (IETR) with the Vice President, Professor Philippe Descamps (IRSEEM), chaired the scientific committee of the 21st JNM. In all, 279 papers of a high technical level were presented – 144 during the 32 oral sessions, and 135 in 16 poster sessions – to which must be added four papers presented by invited renowned people. A specific exhibition area hosted 28 exhibitors during the 3 days: CST/Dassault, TEKTRONIX S.A.S., ANSYS, ROHDE & SCHWARZ, CYLEONE, E-V Technologies, FI Science, NXP semiconductors, KEYSIGHT, CISTEME, ALPHA RLH, PYLA, OMMIC, ANRITSU, “GTID anciennement Elliptika,” C.T. Systemes, XFAB France, MB Electronique, AO Technologies, S2P Smart Plastic Products, DICONEX, EXOCIS, ABS Technics, EDA Expert, ARELIS – NAE, ALTAIR, KAPTEOS and Zodiac Data System. Professor Philippe Descamps chaired the local organizing committee, with a team of many enthusiastic volunteers. Dr. Bogdan Cretu and Dr. Matthieu Denoual conducted the scientific organization.

The 21st JNM event was also supported by International Journal of Microwave and Wireless Technologies (IJMWT), IEEE MTT-S, Instrumentation and Measurement societies, European Microwave Association EuMA, and NAE (Normandy Aerospace). These recipients are:

Papers accepted for publication in a Mini-special issue IJMWT:

1. 1) Florent Torres, Eric Kerhervé, Andreia Cathelin, Magali de Matos

   “Un amplificateur de puissance configurable à polarisation corporelle de 31 GHz en CMOS FD-SOI 28 nm pour les applications 5G”

2. 2) Alassane Sidibe, Gaël Loubet, Alexandru Takacs, Guillaume Ferré, Anthony Ghiotto

   “Conception d'antenne de drone miniature pour la détection des avions de ligne”

EuMA Awards:

Vincent Laquerbe, Adrien Laffont, Romain Pascaud, Thierry Callegari, Laurent Liard, Olivier Pascal for their communication titled “Utilisation de la résonance plasmonique de surface d'une décharge plasma pour la conception d'antennes miniatures accordables”

IEEE French section Awards:

Sana Abid, Cyril Decroze, Thomas Fromenteze, Moctar Mouhamadou for their communication titled “Imagerie Radiométrique Computationnelle en Bande Millimétrique”

NAE Awards:

Vincent Gidel, Frédéric Gianesello, Pascal Chevalier, Gregory Avenier, Nicolas Guitard, Cyril Luxey, Guillaume Ducournau for their communication titled “Diode Schottky intégrée en technologie BiCMOS 55 nm visant les applications THz”

UAV antenna design competition student awards sponsored by IEEE MTT and AP France and Rogers Corporation was organized by Anthony Ghiotto (IMS Bordeaux). The recipients were: Alassane SIDIBE, Tran Quang Khai Nguyen and Luca Santamaria, Vincent Olivier, Paul Teillet, Rémi Bouche, Edouard Rochefeuille and Erika Vandelle, Maxime Wawrzyniak and Clément Pornin, Julien Hautmant.

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 18 best papers presented at the 21st 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, two 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 2019. 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.