A transmitting circuit. In some embodiment, the transmitting circuit includes a slot antenna and an amplifier. The slot antenna may include a slot in a conductive sheet, and it may have a first resonant frequency, the first resonant frequency being within 20% of a slot frequency which is between a first frequency corresponding, in a first volume, to a wavelength twice the length of the slot, and a second frequency corresponding, in a second volume, to a wavelength twice the length of the slot. The amplifier may be connected to the slot through a connection including a conductive path, between the amplifier and the slot, having a length less than 0.2 times the length of the slot. The magnitude of the output impedance of the amplifier may be less than 0.25 times the magnitude of the impedance of the slot antenna at a first resonant frequency.