Power supply for microwave sensing device

摘要

A sensing device comprises a microwave sensor 1 configured to emit microwave radiation and to receive microwave radiation reflected by a moving body in the field of detection of the microwave sensor and a wireless data transmitter 4 configured to transmit data to a remote receiver. A main power supply provides electrical power at a first voltage to the sensing device. A first regulator 6 provided between the main power supply and the microwave sensor 1 provides a sensor power supply to the microwave sensor 1 at a voltage below the voltage of the main power supply. The wireless data transmitter 4 is powered from the main power supply via a transmitter power supply connection arranged in parallel with the first regulator 6. The microwave sensor 1 is provided on a first circuit board and the wireless data transmitter 4 is provided on a second circuit board, with the second circuit board overlying the first circuit board and spaced therefrom. A signal processing device is configured to receive an output signal from the microwave sensor 1 and to generate an occupancy signal indicative of the presence of a moving body in the field of detection of the microwave sensor 1 when the output signal of the microwave sensor 1 exceeds a threshold level. The signal processing device is configured to increase the threshold level temporarily during data transmission by the wireless data transmitter 4, in order to compensate for RF interference due to the data transmission.