Peak and average power emissions of the newly emerging ultra wideband (UWB) radio are supposed to be limited by regulatory constraints. Impact of emission constraints on direct sequence (DS-) UWB communications that use arbitrary chip-duty is discussed in this letter. Depending on the communication pulse shape, a minimum chip-duty below which average emission cannot be increased with bandwidth, or in other words, permissible average emission limit cannot be reached due to the peak constraint is pointed. Effect of the emission constraints on the system capacity is also investigated and compared with the same with no constraint. It is shown that a peak constraint slows down the capacity increment with bandwidth.
The authors propose an Optical Tandem Single Sideband (OTSSB) system using orthogonal subcarriers that double bandwidth efficiency by allowing transmission of different channels in the upper and lower sidebands of the same optical carrier. A mathematical model and simulation results are presented to demonstrate this new technique.
The spectral organization in a noisy speech is different during noise-only portions and speech portions. Such chaotic difference can be tracked by using negentropy as a measure. Accordingly, a Voice Activity Detector (VAD) based on the negentropy measure of magnitude of spectral components of the pseudo-stationary segments of speech is proposed and has been used for the estimation of noise statistics from the noisy speech signal in very low SNR conditions. The results show the effectiveness and usefulness of the proposed method under very noisy conditions.
We propose in this paper an improved method for binarizing document images by adaptively exploiting the local image contrast. The proposed method aims to overcome the common problems encountered in low quality images, such as uneven illumination, low contrast, and random noise. Experiments have been conducted and the results are presented to show the effectiveness of the proposed method.
Recently, the authors introduced two new second-order single-resistance-controlled oscillators (SRCO) employing four/three unity-gain cells (unity-gain voltage followers and unity-gain current followers). In this communication, a novel family of SRCOs has been presented which employ a reduced number of (only two) unity-gain cells as active elements. The workability of the new circuits has been confirmed by the SPICE simulations of their CMOS-implementable versions.
We propose a P-HEMT structure with a strained InSb barrier inserted and investigate its resistivity against plasma-induced fluorine damage with Hall measurements and a SIMS evaluation. The fluorine intrusion into the active layers of the P-HEMT during the RIE process was greatly suppressed by the ultra thin InSb barrier layer and the values of the carrier density and electron mobility improved by 43% and 35% from those for a conventional P-HEMT. After thermal annealing, the number of accumulated fluorine atoms in the δ-doped layer also decreased and the carrier density and electron mobility improved by 36% and 11% from those for a conventional P-HEMT. This indicated the strained InSb barrier was very effective in suppressing the plasma-induced fluorine damage in the P-HEMT.
We investigated the frequency dependences of Y22 of FD-SOI MOSFETs, in which the drain current response delay is observed for the first time. Short channel FD-SOI devices operating in linear region show significant drain current response delay. It is confirmed that FD-SOI MOSFET's RF behavior can be well reproduced with the proposed model including the drain current response delay.