This paper proposes an all-hardware architecture to perform the subpixel refinement operation in the scale invariant transform algorithm. Although the literature describes several hardware implementations of this algorithm, due to its complexity, most of them are based on simplifications of it. These implementations normally exclude the subpixel refinement stage, which, however, is an essential process to obtain accurate results in image matching applications.The architecture has been described in very high-speed integrated circuit hardware description language at register transfer level and synthesized on a Xilinx Zynq 7020 device. The latency of the proposed architecture to generate a refinement operation is 211 clock cycles, and the throughput achieved exploiting pipeline techniques is 64 cycles. The architecture uses fixed-point data representation and has been tested with images from known databases, yielding very good performance compared with the floating-point software implementation of the algorithm.

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This paper presents a pipeline analog to digital converter (ADC) consisting of five stages with 2.5 effective bit resolution. Several techniques were combined for the reduction of the power consumption and to preserve the converter linearity. To reduce the power consumption, the circuit has two scaled operational transconductance amplifiers (OTAs), which are shared by the first four pipeline stages. The last fifth stage is a single decoder with 2.5 effective bits. Each OTA includes additional circuitry to adapt the power consumption according to the stage that uses the OTA. This technique changes the bias current depending on the stage in operation. The ADC was optimized to obtain 11-bit resolution with frequencies from 1 kHz to 10 MHz. The technology used to simulate the ADC is a 3.3 V 0.35 µm CMOS process and the circuit consumes 17.9 mW at 20 MSample/s sampling rate. With this resolution and sampling rate, it achieves 67.28 dB SNDR and 10.88 bit ENOB at 0.1 MHz input frequency. The Figure of Merit is 0.473 pJ/step.

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