A 1.5-V 45-mW direct-conversion WCDMA receiver IC in 0.13-/spl mu/m CMOS

A 2-GHz direct-conversion receiver for wide-band code division multiple access (WCDMA) is presented. It includes two low-noise amplifiers (LNAs), an I/Q demodulator, and two sixth-order baseband channel select filters with programmable gain. Quadrature local oscillator (LO) signals are generated on chip in a frequency divider flip-flop. An external interstage filter between the LNAs rejects transmitter leakage to relax demodulator linearity requirements. A low-voltage demodulator topology improves linearity as well as demodulator output pole accuracy. The active-RC baseband filter uses a programmable servo loop for offset compensation and provides an adjacent channel rejection of 39 dB. Programmable gain over 71-dB range in 1-dB steps is merged with the filter to maximize dynamic range. An automatic on-chip frequency calibration scheme provides better than 1.5% corner frequency accuracy. The receiver is integrated in a 0.13-/spl mu/m CMOS process with metal-insulator-metal (MIM) capacitors. Measured receiver performance includes a 6.5-dB noise figure, IIP2 of +27 dBm, and IIP3 of -8.6 dBm. Power consumption is 45 mW.     

CIGS thin-film solar cells on steel substrates

Steel foil is an attractive candidate for use as a flexible substrate material for Cu(In_x,Ga_1 − x)Se₂ solar cells (CIGS). It is stable at the high temperatures involved during CIGS processing and is also commercially available. Stainless chromium (Cr) steel is more expensive than Cr-free steel sheets, but the latter are not stable against corrosion. We processed CIGS solar cells on both types of substrates. The main problem arising here is the diffusion of detrimental elements from the substrate into the CIGS absorber layer. The diffusion of iron (Fe) and other substrate elements into the CIGS layer was investigated by Secondary Ion Mass Spectrometry (SIMS). The influence of the impurities on the solar cell parameters was determined by current voltage (JV) and external quantum efficiency (EQE) measurements. A direct correlation between the Fe content in the CIGS layer and the solar cell efficiency was found. The diffusion of Fe could be strongly reduced by a diffusion barrier layer. Thus we could process CIGS solar cells with a conversion efficiency of 12.8% even on Cr-free steel substrate.     

A 2-GHz carrier leakage calibrated direct-conversion WCDMA transmitter in 0.13-/spl mu/m CMOS

A highly integrated 2-GHz, 0.13-/spl mu/m CMOS direct-conversion transmitter for wide-band code division multiple access (WCDMA) is described. Different circuit and calibration techniques are presented that successfully suppress the carrier leakage and enable the direct-upconversion architecture to meet all WCDMA specifications. The transmitter delivers +2.5 dBm output power while consuming only 45 mA from its nominal 1.5-V supply. The overall gain can be programmed in 1-dB steps over a 100-dB range with 0.4 dB accuracy. The transmitter achieves an OIP3 of +19.3 dBm, an error vector magnitude of 4.3%, and an adjacent channel leakage ratio of -38 dBc. The measured output noise of -146 dBm/Hz in the DCS Rx band and -149 dBm/Hz in the UMTS Rx band is sufficiently low to provide an option to increase the integration level even further by eliminating the external Tx interstage filter between the power amplifier and its driver.