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.
The parallel waveform relaxation stochastic Runge–Kutta method for stochastic differential equations
For large-scale non-autonomous Stratonovich stochastic differential equations, we study a very general parallel waveform relaxation process which is on the basis of stochastic Runge–Kutta (SRK) method of mean-square order 1.0 in this literature. The convergence of the whole parallel numerical iterative scheme can be guaranteed and the scheme provides better properties in terms of decreasing the load of the computation and operating speed. At the same time, the related limit method is also introduced as the continuous approximation derived from the iterative scheme. In the approximation interval, it is worth noting that the mean-square order of the parallel numerical iterative scheme can be kept consistent with the previous SRK method at any arbitrary time point, not just at discrete points. Some numerical simulations are presented to elaborate the computing efficiency of the parallel numerical iterative scheme.