Abstract: A circuit portion is provided which includes an energy harvesting device producing a DC output; a DC-DC converter having an input connected to the DC output of the energy harvesting device; an output for connection to a load; and a monitoring module including a non-ohmic semiconductor element. The monitoring module is arranged to derive information relating to an output current flowing from the DC-DC converter by measuring a current through the non-ohmic semiconductor element. The monitoring module is arranged to adjust one or more parameters of the DC-DC converter based on the information relating to said output current flowing from the DC-DC converter.

Abstract: A circuit portion is provided which includes an energy harvesting device producing a DC output; an inductor-less capacitor-based DC-DC converter, having an input connected to the DC output of the energy harvesting device; an output connected to a battery; and a voltage limiting module. The voltage limiting module includes a voltage sensor arranged to measure a voltage representative of a voltage at the battery and is arranged to limit a voltage provided by the DC-DC converter if the voltage representative of the voltage at the battery exceeds a threshold.

Abstract: A demodulator for a digital radio receiver comprises a frequency discriminator and a Viterbi decoder. The frequency discriminator receives a series digital signal samples representative of an FSK-modulated signal and performs frequency discrimination on the digital signal samples to generate a series of frequency samples. Each frequency sample represents an instantaneous frequency of the signal in a respective frequency-sample period. There are an integer oversampling factor, N>1, of frequency-sample periods in each symbol period. The Viterbi decoder receives the series of frequency samples, determines branch metrics for each symbol period by determining distances between a vector of N successive frequency samples and each of a plurality of reference waveform vectors, each comprising N elements. It use the branch metrics in a Viterbi process to output demodulated symbol values corresponding to a maximum-likelihood decoding of the FSK-modulated signal.