RF to DC converter

A converter 200 converts a received radio frequency (RF) signal into a DC signal for powering a load 300. The converter 200 comprises a first rectifying arm 207 and a second rectifying arm 209. Each rectifying arm 207, 209 has a rectifier 220a, 220b for generating a DC signal and one or more harmonics together with a component of the RF voltage input. Each rectifying arm 207, 209 also has a first planar transmission line 210a, 210b to guide RF voltage to the rectifier 220a, 220b and a second planar transmission line 230a, 230b to receive the DC signal and to reflect the harmonics back towards the rectifier 220a, 220b. The first planar transmission line 210a, 210b then reflects the reflected signals back towards the rectifier 220a, 220b. The received RF signal provides the voltage difference between the first RF voltage input and the second RF voltage input. An inductor and capacitor 216 may be connected between the first and second rectifier arms 207, 209.