Advanced Direct Wideband Analog to Digital Conversion for Radar

The objective of this program is to achieve direct analog-to-digital conversion of microwave signals with high resolution, using hardware that is universally applicable to a wide range of systems. (This is also referred to as digital downconversion or direct RF sampling.) Doing so will eliminate all analog downconversion stages and will reduce the analog front end of a radar receiver to a single filter and low-noise amplifier. In Phase I of this SBIR program, Photonic Systems, Inc. (PSI) has shown theoretically that this is possible at frequencies up to the mm-wave range, and has also experimentally demonstrated direct analog-to-digital conversion at RF input frequencies up to 19.8 GHz with 16 stated bits of resolution. In Phase II, we will increase the alias-free bandwidth to 500 MHz by changing to a 1 GS/s electronic ADC and increasing the optical pulse rate to 1 GHz. These changes are straightforward. We will also address the excess noise problems that limited the ENOB to ~9, which is 2 bits below what was expected from this system. We will monolithically integrate as many of the photonic components as possible to reduce the size and weight of the PSEQ ADC demonstration system.