We present a 64-channel cross-correlator system for space-borne synthetic aperture imaging. Two different types of ASICs were developed to fit into this system: An 8-channel comparator ASIC implemented in a 130 nm SiGe BiCMOS process technology performs A/D conversion, while a single 64-channel digital cross-correlator ASIC implemented in a 65 nm CMOS process performs the signal processing. The digital ASIC handles 2016 cross-correlations at up to 3.6 GS/s and has a power dissipation of only 0.13 mW/correlation/GHz at a supply voltage of 1 V. The comparator ASIC can handle sample rates of at least 4.5 GS/s with a power dissipation of 47 mW/channel or 1 GS/s with a power dissipation of 17 mW/channel. The assembled system consists of a single board measuring a mere 136 136 mm and weighing only 135 g. The assembled system demonstrates crosstalk of 0.04% between neighboring channels and stability of 800 s. We provide ASIC and system-board measurement results that demonstrate that aperture synthesis can be a viable approach for Earth observation from a geostationary Earth orbit.

Abstract-A high-speed low-power cross-correlator ASIC has been implemented in a 65-nm CMOS process for the purpose of synthetic aperture radiometry from geostationary orbiting earth observation satellites. The chip performs cross-correlation on all individual signal pairs from 64 digital 1-bit inputs, which amounts to 2016 individual cross-correlation products. The experimental evaluation, using a specially developed PCB, demonstrates that the 3-mm 2 chip has a top performance of 3.6 GHz at a 1.2 V supply, at which it dissipates 790 mW.

We present a high-speed low-power 8-channel comparator tailored for the application of sampling antenna signals in a cross-correlator system for space-borne synthetic aperture radiometer instruments. Features like clock return path, perchannel offset calibration and bias current tuning make the comparator adaptable and gives the possibility to adjust the comparator for low power consumption, while keeping performance within the requirements of the cross-correlator system. The comparator has been implemented and fabricated in a 130-nm SiGe BiCMOS process. Measurements show that the comparator can perform sampling at a rate of 4.5 GS/s with a power consumption of 48 mW/channel or 1 GS/s with a power consumption of 17 mW/channel.

Abstract-We present a cross-correlator ASIC for synthetic aperture imaging of Earth's atmosphere. Reconfigurability as a 2-level 96-channel or 3-level 48-channel cross-correlator provides adaptability to a wider array of applications. Implemented in a 65-nm CMOS process, the cross-correlator is capable of running at clock speeds of up to 3 GHz. In 2-level 96-channel mode, the cross-correlator consumes only 1.1 W at 2.5 GHz and 1.2 V, yielding a power efficiency of 96 µW/prod/GHz. The 450-Mb/s readout speed and double-buffering reduce blanking time of the interferometer system to a minimum.