A Decade-Bandwidth Low-Noise Mixer RFIC with a Distortion-Canceling Output Amplifier

This paper presents a 1-10 GHz low-noise downconvert mixer RFIC suitable for wideband receivers. A switched transconductor mixing core is adopted to reduce noise at high frequencies. By adding a series inductor to the RF transconductor, a flat 4-5 dB noise figure (NF) and a high gain of 26.5 dB can be achieved over a broad bandwidth out to 10 GHz. A CMOS output amplifier is also integrated on-chip, employing derivative superposition (DS) for high linearity and an OIP3 of 16.5 dBm. The circuit consumes less than 20 mW of dc power and occupies an active chip area of less than 0.2 mm2.

Fiber-Optic Ring-Down Spectroscopy Using a Tunable Picosecond Gain-Switched Diode Laser

Visible and near-infrared laser light pulses were coupled into two different types of optical fiber cavities. One cavity consisted of a short strand of fiber waveguide that contained two identical fiber Bragg gratings. Another cavity was made using a loop of optical fiber. In either cavity ∼ 40 ps laser pulses, which were generated using a custom-built gainswitched diode laser, circulated for a large number of round trips. The optical loss of either cavity was determined from the ring-down times. Cavity ring-down spectroscopy was performed on 200 pL volumes of liquid samples that were injected into the cavities using a 100 μm gap in the fiber loop. A detection limit of 20 ppm of methylene blue dye in aqueous solution, corresponding to a minimum absorptivity of εC < 6 cm−1, was realized.