Experimental and simulation studies of antenna-amplifier and relativistic magnetron are being carried out in Nagaoka University of Technology (Japan) and Nuclear Physics Institute (Russia), as an international collaboration. The objective of these studies is to carry out experimental demonstration of antenna-amplifier and to perform experimental and simulation studies of relativistic magnetron with transparent cathode. The new concept of hybrid antenna-amplifier has been studied by three-dimensional particle-in-cell simulation and by experiment ...