A novel S-band circularly polarized patch antenna system suited for earth-observing CubeSats is presented. The antenna consists of four rectangular patches properly excited in order to have the maximum gain in the boresight direction and produce circular polarization. The antenna has a compact size, and its geometry and characteristics are compatible with any CubeSat standard structure. A 57-mm-wide square window allows to accommodate imaging system optics in its center leading to a very compact overall system. A prototype of the designed antenna system has been used to validate simulation results that showed a gain of 7.3 dBi. Experimental measurements confirm that the antenna achieves good impedance match at the desired frequency of 2450 MHz, a directivity of 8.3 dBi, and 60 ^° 3-dB beamwidth, in good agreement with the simulation results.

In this letter, we show the results achieved using a hydrogenated amorphous silicon photosensor for a “label-free” deoxyribonucleic acid (DNA) analysis based on the measurements of the absorbance in the ultraviolet range. The optimization of the sensor structure allowed us to bring the detection limit for a 30-mer DNA sample down to $1\mathrm{nM}\times \mathrm{cm}$ , limited by the experimental setup. Taking advantage of the hypochromic effect, we also demonstrated the detection of single- and double-stranded DNA molecules in a melting experiment. From the noise characterization of our setup, we estimated the minimum DNA absorbance required to detect the occurrence of a hybridization/separation process to be below ${10}^{-3}$ .

A novel signal processing concept for X-ray imaging with directly converting pixelated semiconductor sensors is presented. The novelty of this approach compared to existing concepts is the combination of charge integration and photon counting in every single pixel. Simultaneous operation of both signal processing chains extends the dynamic range beyond the limits of the individual schemes and allows determination of the mean photon energy. Medical applications such as X-ray computed tomography can benefit from this additional spectral information through improved contrast and the ability to determine the hardening of the tube spectrum due to attenuation by the scanned object. A prototype chip in 0.35-micrometer technology has been successfully tested. The pixel electronics are designed using a low-swing differential current mode logic. Key element is a configurable feedback circuit for the charge sensitive amplifier which provides continuous reset, leakage current compensation and replicates the input signal for the integrator. This paper will discuss measurement results of the prototype structures and give details on the circuit design

A flat X-ray detector with lead oxide (PbO) as direct conversion material has been developed. The material lead oxide, which has a very high X-ray absorption, was analysed in detail including Raman spectroscopy and electron microscopy. X-ray performance data such as dark current, charge yield and temporal behaviour were evaluated on small functional samples. A process to cover a-Si TFT-plates with PbO has been developed. We present imaging results from a large detector with an active area of 18 × 20 cm². The detector has 1080 × 960 pixels with a pixel pitch of 184 μm. The linearity of detector response was verified. The NPS was determined with a total dark noise as low as 1800 electrons/pixel. The MTF was measured with two different methods: first with the analysis of a square wave phantom and second with a narrow slit. The MTF at the Nyquist frequency of 2.72 lp/mm was 50 %. We calculated first DQE values of our prototype detector plates. Full size images of anatomic and technical phantoms are shown.