An Optically Powered CMOS Receiver System for Intravascular Magnetic Resonance Applications

Abstract

This paper presents a low-power optically powered receiver system designed in 0.18 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu {\rm m}$</tex> </formula> triple well UMC complementary metal–oxide–semiconductor (CMOS) technology. Optical transmission is used for both power delivery and signal transmission. The power of the whole system can be supplied in two different configurations, namely continuous and intermittent mode configurations. In the continuous mode configuration, the optical power of a 650-nm laser source is received and delivered to the electronic circuits by a set of on-chip CMOS photodiodes. In the intermittent mode configuration, a low voltage DC-DC converter is used to boost a single on-chip CMOS photodiode voltage of 0.65 V up to 1.8 V. Additionally, in this configuration, optical switching is used for charging and discharging of a storage capacitor to obtain currents in milliampere range for the proper operation. The front-end part of the receiver consists of a fully differential low noise amplifier (LNA), a fully differential gain stage, a single output double balanced Gilbert-cell mixer, and a laser driver. The front-end part can operate properly by one on-chip photodiode voltage of 0.65 V . System performance is demonstrated for a sample 1.5 T magnetic resonance imaging (MRI) application. Experiments show that LNA of the receiver has a low input referred noise voltage density of 4 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm nV}/\sqrt {\rm Hz}$</tex></formula> at the supply voltage of 0.65 V . The receiver transmits the signal via a fiber-coupled infrared (IR) laser diode ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda = 1310$</tex></formula> nm). The results show that the system can continuously process a minimum detectable signal (MDS) of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-70$</tex></formula> dBm at an incident optical power of 20 mW while the total power consumption of the receiver and the IR diode is 700 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu {\rm W}$</tex> </formula> . In the intermittent mode configuration, the system gain is measured to be 6 dB greater, and the average power consumption is measured as 214 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu {\rm W}$</tex></formula> when the incident laser is modulated with a rectangular pulse wave of 40 ms period with 95% duty cycle.