A rectifier for wireless power transfer, the rectifier comprising: an electromagnetic signal receiving element operable to be driven with an electromagnetic signal oscillating at a first frequency; a first tank circuit comprising a first inductor and a first capacitance in series, wherein the first inductor is in series with the electromagnetic signal receiving element; a second tank circuit in parallel with the series connection of the electromagnetic signal receiving element and the first inductor, the second tank circuit comprising a second inductor and a second capacitance in series; a rectifying element in parallel with the first capacitance; and a third capacitance in series with the parallel connection of the rectifying element and the first capacitance; wherein: the series connection of: (i) the third capacitance and (ii) the parallel connection of the rectifying element and the first capacitance is in parallel with the series connection of the electromagnetic signal receiving element and the first inductor, the first inductor is in series with the electromagnetic signal receiving element between the electromagnetic signal receiving element and the second tank circuit, the first capacitance is between the second tank circuit and the third capacitance, and the second inductor and the second capacitance are selected such that the resonant frequency of the second tank circuit is an integer multiple, greater than one, of the first frequency. an electromagnetic signal receiving element operable to be driven with an electromagnetic signal oscillating at a first frequency; a first tank circuit comprising a first inductor and a first capacitance in series, wherein the first inductor is in series with the electromagnetic signal receiving element; a second tank circuit in parallel with the series connection of the electromagnetic signal receiving element and the first inductor, the second tank circuit comprising a second inductor and a second capacitance in series; a rectifying element in parallel with the first capacitance; and a third capacitance in series with the parallel connection of the rectifying element and the first capacitance; wherein: the series connection of: (i) the third capacitance and (ii) the parallel connection of the rectifying element and the first capacitance is in parallel with the series connection of the electromagnetic signal receiving element and the first inductor, the first inductor is in series with the electromagnetic signal receiving element between the electromagnetic signal receiving element and the second tank circuit, the first capacitance is between the second tank circuit and the third capacitance, and the second inductor and the second capacitance are selected such that the resonant frequency of the second tank circuit is an integer multiple, greater than one, of the first frequency. the series connection of: (i) the third capacitance and (ii) the parallel connection of the rectifying element and the first capacitance is in parallel with the series connection of the electromagnetic signal receiving element and the first inductor, the first inductor is in series with the electromagnetic signal receiving element between the electromagnetic signal receiving element and the second tank circuit, the first capacitance is between the second tank circuit and the third capacitance, and the second inductor and the second capacitance are selected such that the resonant frequency of the second tank circuit is an integer multiple, greater than one, of the first frequency.