Abstract: A method of determining a distance between a radio frequency device and a target is disclosed in which the radio frequency device receives a radio frequency signal from the target. The method comprises determining a time domain channel response from the received radio frequency signal, determining an amplitude of a largest peak in the time domain channel response, determining an amplitude of a second, earlier, peak in the time domain channel response, comparing the second peak amplitude to a threshold based on the largest peak amplitude, identifying the largest peak as a shortest path peak if the second peak amplitude is less than the threshold, identifying the second peak as a shortest path peak if the second peak amplitude is greater than the threshold, and calculating the distance between the radio frequency device and the target based on a time corresponding to the shortest path peak.

Abstract: A radio system comprises a radio transmitter apparatus and a radio receiver apparatus. The radio transmitter apparatus is configured to transmit a continuous-wave radio-frequency signal having a first frequency. The radio receiver apparatus comprises: an antenna for receiving the continuous-wave radio-frequency signal; a local oscillator for generating a periodic signal at a second frequency which differs from the first frequency by a frequency offset; a mixer for mixing the received continuous-wave radio-frequency signal with the periodic signal to generate a down-mixed signal; and a processor or other circuitry configured to generate frequency-offset data from the down-mixed signal, wherein the frequency-offset data is representative of an estimate of the frequency offset. The processor or other circuitry is configured to use the frequency-offset data to generate DC-offset data representative of an estimate of a DC offset component of the down-mixed signal.

Abstract: A method for analyzing a frequency stability of a radio transceiver device comprises receiving a first succession of unmodulated radio-frequency signals of different frequencies from a radio transceiver apparatus. For each unmodulated radio-frequency signal, a respective time series of phase-offset values is determined, each phase-offset value being representative of a difference between a phase of the respective received unmodulated radio-frequency signal and a phase of a respective reference signal. The time series of phase-offset values is processed to determine a respective signal-phase-offset value for each unmodulated radio-frequency signal. A frequency-stability value, representative of a frequency stability of the radio transceiver apparatus, is calculated as a function representative of statistical variation in the signal-phase-offset values determined for the first succession of unmodulated radio-frequency signals.

Abstract: A method of determining a distance between a radio frequency device and a target is disclosed in which the radio frequency device receives a radio frequency signal from the target. The method comprises determining a time domain channel response from the received radio frequency signal, determining an amplitude of a largest peak in the time domain channel response, determining an amplitude of a second, earlier, peak in the time domain channel response, comparing the second peak amplitude to a threshold based on the largest peak amplitude, identifying the largest peak as a shortest path peak if the second peak amplitude is less than the threshold, identifying the second peak as a shortest path peak if the second peak amplitude is greater than the threshold, and calculating the distance between the radio frequency device and the target based on a time corresponding to the shortest path peak.