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Low temperature photoluminescence spectroscopy is used to analyze the effects of the postgrowth thermal annealing on the electronic structure ad carrier dynamics of GaAs∕AlGaAs quantum dot and quantum ring structures grown by droplet epitaxy. All the samples show a large increase in the photoluminescence efficiencies after the thermal treatment due to sizeable reduction in the material defectivity. Modifications of the photoluminescence band, which depend on thermal annealing temperature, are found and quantitatively interpreted by means of a simple model based on the Al–Ga interdiffusion.

A 0.13-um CMOS fourth-order notch filter for the rejection of the 5–6 GHz interference in UWB front-ends is reported. The filter is integrated into an analog front-end for Mode #1 UWB. A thorough analysis based on a simplified model of the filter is carried out. An algorithm for the automatic tuning and calibration of the filter is also discussed and demonstrated. Two versions of the circuit are designed and fabricated: the first comprises a low-noise amplifier and the filter, and the second expands it to a complete front-end. In the latter version the filter was also redesigned. The filter provides more than 35 dB of attenuation and has a tuning range of 900 MHz, adding less than 30% power consumption to the LNA. The out-of-band IIP3 (higher than -13.2 dBm with the filter off) takes a 9-dB advantage from the filter and the compression of the gain due to the out-of-band blocker is reduced by at least 6 dB in the complete front-end. The conversion gain of the front-end is 25 dB per channel, its average noise figure is lower than 6.2 dB, and its in-band 1-dB compression point is higher than -30 dBm at a power consumption of 32 mW

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A fully integrated differential low-power low-noise amplifier (LNA) for ultrawideband (UWB) systems operating in the 3–5-GHz frequency range is presented. A two-section ladder input network is exploited to achieve excellent input match in a wideband fashion and to optimize the noise performance. Prototypes fabricated in a digital 0.13-um complementary metal oxide semiconductor technology show the following performance: 9.5-dB peak power gain, 3.5-dB minimum noise figure, -6-dBm input-referred 1-dB compression point, and -0.8-dBm input-referred third-order intercept point, while drawing 11 mA from a 1.5-V supply. The realized LNA is compared with previously reported LNAs tailored for the same frequency range

We present a behavioral analysis of two different transceiver architectures for UWB breast cancer imaging employing a SFCW radar system. A mathematical model of the direct conversion and super heterodyne architectures together with a numerical breast phantom are developed. FDTD simulations data are used on the behavioral model to investigate the limits of both architectures from a circuit-level point of view. Insight is given into I/Q phase inaccuracies and their impact on the quality of the final reconstructed images. The result is that the simplicity of the direct conversion makes the receiver more robust towards the critical circuit impairments for this application, that is the random phase mismatches between the TX and RX local oscillators

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