Colloidal quantum dots (QDs) combined with a graphene charge transducer promise to provide a photoconducting platform with high quantum efficiency and large intrinsic gain, yet compatible with cost-efficient polymer substrates. The response time in these devices is limited, however, and fast switching is only possible by sacrificing the high sensitivity. Furthermore, tuning the QD size toward infrared absorption using conventional organic capping ligands progressively reduces the device performance characteristics. Here we demonstrate methods to couple large QDs (>6 nm in diameter) with organometal halide perovskites, enabling hybrid graphene phototransistor arrays on plastic foils that simultaneously exhibit a specific detectivity of 5 × 10 Jones and high video-frame-rate performance. PbI and CHNHI co-mediated ligand exchange in PbS QDs improves surface passivation and facilitates electronic transport, yielding faster charge recovery, whereas PbS QDs embedded into a CHNHPbI matrix produce spatially separated photocarriers leading to large gain.

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Direct delta-sigma receiver architecture is introduced for wireless communication systems, such as LTE or WiMax. Architecture is based on direct downconversion, delta-sigma feedback that is up-converted to RF, and N-path filtering technique. Hence, the core receiver functions including channel selection filtering are embedded to a RF ADC with excellent linearity performance. This is achieved by transforming narrow-band filtering partially to RF injecting feedback into the input of the second amplifier stage, hence relieving requirements of the most critical subsequent stages. A 900-MHz direct delta-sigma receiver prototype occupies an active area of 1 2 mm 2 in 65-nm CMOS. The receiver for low-band cellular operations achieves NF of 2.3 and 6.2 dB in conventional and delta-sigma modes, respectively, and out-of-band IIP3 up to +4 dBm when the delta-sigma loop is active. The chip consumes 80 mW from a 1.2-V supply.

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Localized spectrum sensing is an alternate for database centric approaches to solve secondary use of spectrum in cognitive radios. This can be carried out by using collaborative spectrum sensing where larger amount of small devices is utilized for local spectrum sensing. This paper describes an mobile device scale implementation of multi-mode, multi-band spectrum sensor for cognitive radio. Cyclostationary feature detector algorithm is utilized to detect digital television (DVB-T/H) on UHF band and IEEE802.11a/g on 2.4/5 GHz (ISM/WLAN) bands. A miniaturized spectrum sensing device encounters physical challenges; like limited size and battery capacity, but provides opportunities to establish a dense network and fast response to dynamic chances in signal conditions.