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.
42% high-efficiency two-stage HBT power-amplifier MMIC for W-CDMA cellular phone systems
This is the first paper to report on a high-efficiency two-stage heterojunction-bipolar-transistor power-amplifier monolithic microwave integrated circuit (MMIC) for 1.95-GHz wide-band code-division multiple-access (W-CDMA) cellular phone systems. Power amplifiers for W-CDMA systems are required to operate at high efficiency and high linearity over a wide range of output power levels. To obtain high efficiency at low output power (P/sub out/) as well as at the required maximum P/sub out/ and obtain a high linearity at the maximum P/sub out/, we chose near-class-B operation. To improve linearity at a medium P/sub out/ range, we suppressed the gain distortion resulting from near-class-B operation by using an adaptive biasing technique. The MMIC exhibited a power-added efficiency of 42%, the highest ever reported, a gain of 30.5 dB, and an adjacent channel leakage power ratio at a 5-MHz offset frequency of -38 dBc at a P/sub out/ of 27 dBm under a supply voltage of 3.5 V with 3.84-Mcps hybrid phase-shift keying modulation.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.