Digital Impulse Radio Ultra Wide-Band Transmitter

Abstract

A CMOS impulse radio ultra wide-band (IR-UWB) digital transmitter is presented as the up-link communication module of a 64-channel parallel cortical recording implanted system. The transmitter is capable of transmitting live recording data at programmable rates of 1.5/3/6/12 Mb/s using a single 4 MHz clock. A novel all-digital delay locked loop (AD-DLL) serves as an 8-array pulse position modulator (PPM) enabling aggressive duty-cycling of the transmitter (Tx). The 8-PPM modulation scheme provides intrinsic scrambling of the pulse position which attenuates the spectral peaks. The UWB pulse generator is implemented using finite impulse response synthesis of the raised-cosine pulse. A symmetric pulse-combining technique is proposed to reduce the number of power amplifier elements by half, which enables reducing the parasitic at the Tx output, as well as enhancing the tuning range capability of the transmitter. The transmitter is implemented in a 90 nm CMOS technology, consumes 540 $\upmu$W from a 1 V power supply, which results in an energy efficiency of 45 pJ/bit with an output power of ${-}26$ dBm. The active silicon area is $0.37\,\mathrm{{mm}}^{2}$. The modulated spectrum of the transmitter is fully compliant with USA Federal Communications Commission (FCC) effective isotropic radiated power (EIRP) modulation masks for indoor and outdoor UWB communication devices.