Reduced gain variation against temperature with thermistor on HPA module for W-CDMA system
A high-power amplifier (HPA) module for wide-band code division multiple access (W-CDMA) system with small gain variation against temperature is presented in this paper. Two temperature compensation techniques, which contain gain control bias circuits that correspond to temperature or thermistors were investigated. Comparison between the above techniques indicated that the technique with thermistors was more effective in reducing gain variation without affecting linearity. A fabricated two-stage HPA module for W-CDMA system with a thermistor in its input matching network provided a small gain variation within plusmn1 dB and an ACLR under -36 dBc in the temperature range from -10 to +85degC when ACLR was measured under load mismatched conditions, VSWR=1.4:1.
A 20-mA quiescent current two-stage W-CDMA power amplifier using anti-phase intermodulation distortion
This paper explains how the adjacent-channel-leakage-power ratio (ACLR) of power amplifiers (PAs) can be reduced by using gain-expansion amplifiers in tandem and generating anti-phase intermodulation distortion (IMD) in the driver stage to cancel the IMD in the output stage. The power-added-efficiency (PAE) can thus be increased by using near-class-B-biased driver- and output-stage amplifiers, which inherently have gain-expansion characteristics and high PAE at low output power as well as at maximum output power. At a supply of 3.5 V and an output power of 27.1 dBm, the fabricated PA with a quiescent current of only 19.8 mA exhibited a PAE of 44%, a gain of 25.2 dB, and an ACLR of less than -38.0 dBc. This is state-of-the-art performance for a two-stage W-CDMA PA with an extremely low quiescent current.
In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs
Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.