Time-frequency multiplexing for time-encoded signals from brain-computer interfaces

Brain-computer interfaces (BCI) provide a way to monitor and treat neurological diseases. These interfaces contain an array of sensors that gather and transmit data. Given low-power and no-clock limitations, asynchronous sigma delta modulators (ASDMs) are considered as an alternative to synchronous analog to digital conversion. ASDMs are non-linear feedback systems that enable time-encoding of analog signals. In this paper we provide an efficient reconstruction of time-encoded band-limited signals using a prolate spheroidal waveform (PSW) projection. Furthermore, we show how a modified orthogonal frequency division multiplexing (OFDM) technique using chirp modulation can be used to transmit an array of time-encoded signals emanating from the BCI. Our method generalizes the chirp modulation of binary streams with non-uniform symbol duration.