40 GSPS All Optical ADC with ENOB of 6.6 using EO Polymer Optical Deflector and Spatial Quantizer
Résumé
40GSPS analog-to-digital converters (ADC) are
required for realization of digital receivers up to 20GHz. An all
optical ADC is presented using an optical deflector for spatial
sampling. The optimized design of optical deflector is based on
optical beam propagation and finite element modeling
electromagnetic modeling. An effective number of bits (ENOB) of
6.6 ADC is achieved under a ±20V RF voltage swing and by
minimalizing angular resolution with a leaky waveguide of 2cm
long. Design and implementation of a polymer waveguide are
presented, meeting the leaky waveguide coefficient of 0.1Np/cm
and low optical attenuation with quality optical waveguide
surface flatness better than 20nm. A broadband (2 - 40GHz)
transition from coplanar waveguide (CPW) to coupled microstrip
(CMS) transmission lines is presented that overcomes the RF
attenuation to achieve under 0.06Np/cm variation by using a preemphasis
filter with a flat group delay of less than 70ps.