A device for generating an alternating radio-frequency electromagnetic field in a working area (3) comprises an applicator (2) for emitting the electromagnetic field in the working area (3), an oscillator (4) for providing an alternate voltage (VRF) and electric current (IRF) having a predetermined value and a predetermined frequency to the applicator (2), power supply means (5) for supplying a substantially DC voltage (VCC) to the oscillator (4), control means (6) associated with the power supply means (5) for controlling the electrical parameters of the AC voltage, the AC current and/or the frequency provided to the applicator (2) by the oscillator (4). The control means (6) comprise an input port (7) connected to the electric power network (N), a first electronic control circuit (8) which is connected to the input port (7) for substantially instantaneously varying the electrical parameters and instantaneous control of the field emission power, a second electronic control circuit (10) for regulating the operation of the oscillator (4). The first electronic circuit (8) has an output (9) connected to the power supply means (5). A plant comprises the device and a control method for the device. The device allows a quick and dynamic regulation of product treatment temperature and ensures high safety by preventing generation of unexpected electric discharges. The plant allows effective treatment of products without affecting their inherent properties while the control method allows quick and immediate regulation of one or more control parameters of the plant.
