Abstract-We describe a high-rate energy-resolving photoncounting ASIC aimed for spectral computed tomography. The chip has 160 channels and 8 energy bins per channel. It demonstrates a noise level of ENC=214 electrons at 5pF input load at a power consumption of <5mW/channel. Maximum count rate is 17Mcps at a peak time of 40ns, made possible through a new filter reset scheme, and maximum read-out frame rate is 37kframe/s.

Abstract-This paper analyzes the limits of FFT performance on FPGAs. For this purpose, a FFT generation tool has been developed. This tool is highly parameterizable and allows for generating FFTs with different FFT sizes and amount of parallelization. Experimental results for FFT sizes from 16 to 65536, and 4 to 64 parallel samples have been obtained. They show that even the largest FFT architectures fit well in today's FPGAs, achieving throughput rates from several GSamples/s to tens of GSamples/s.

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In this paper we describe an open source floatingpoint adder and multiplier implemented using a 36-bit custom number format based on radix-16 and optimized for the 7series FPGAs from Xilinx. Although this number format is not identical to the single-precision IEEE-754 format, the floatingpoint operators are designed in such a way that the numerical results for a given operation will be identical to the result from an IEEE-754 compliant operator with support for round-to-nearest even, NaNs and Inf s, and subnormal numbers. The drawback of this number format is that the rounding step is more involved than in a regular, radix-2 based operator. On the other hand, the use of a high radix means that the area cost associated with normalization and denormalization can be reduced, leading to a net area advantage for the custom number format, under the assumption that support for subnormal numbers is required. The area of the floating-point adder in a Kintex-7 FPGA is 261 slice LUTs and the area of the floating-point multiplier is 235 slice LUTs and 2 DSP48E blocks. The adder can operate at 319 MHz and the multiplier can operate at a frequency of 305 MHz.

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