A representative from (state-owned) United Instrument Manufacturing Corp that built the weapon described the device to (state-owned) Sputnik News this way:
“The new system is equipped with a high-power relativistic generator and reflector antenna, management and control system, and a transmission system which is fixed on the chassis of BUK surface-to-air missile systems. When mounted on a special platform, the ‘microwave gun’ is capable of ensuring perimeter defense at 360 degrees.
The microwave cannon, if it’s as effective as officials say, runs parallel with U.S. projects to build battle-ready, energy-based weapons. The Navy has shown off its boringly named Laser Weapons System (LaWS) blowing up targets. Meanwhile, Lockeed Martin is developing a death laser of its own. All of that is to say nothing of the Navy’s slightly more conventional “Electric Cannon” (read: railgun).
Given how all the information comes from Russian-owned organizations and there’s no footage of the device in action yet, it’s hard to tell exactly how effective the weapon is. But if it really can knock drones and warheads out of the air with ease, that lends even more power to Russia’s already impressive cold war arsenal.