This paper presents a direct conversion transceiver intended for use in a microfluidic NMR flowmeter. It consists of an H-bridge power amplifier, which drives a hand-wound milimeter-sized coil with RF signals, and a direct conversion receiver, which amplifies the NMR signals picked up by the coil, and then digitizes them with an asynchronous 8 bit SAR ADC sampling at 70 MHz. Fabricated in a 65 nm CMOS technology, the receiver achieves a noise spectral density of 1 nV/sqrt(Hz) at 21 MHz, while dissipating only 36 mW. A microfluidic flowmeter based on the transceiver and a handheld 0.5 T permanent magnet can measure flow rates up to 96 ml/h in a 0.8 mm inner-diameter channel with pm 1.3 % full-scale error. To the authors' best knowledge, this is the first reported portable NMR flowmeter.

This paper presents a portable and contactless microfluidic flowmeter based on the Nuclear Magnetic Resonance (NMR) principle, which can measure flow rates up to 2.7 ml/min with \pm 16\ lmin (±0.6% full-scale) error. It consists of a millimeter-size RF coil wound around a microfluidic channel, custom readout electronics and a 0.5 T permanent magnet with 50 ppm inhomogeneity. To our knowledge, this is the first reported low-field NMR microfluidic flowmeter.