Search

The speed of the Magnetic suspension compressor is very important for the control of the entire compressor. In general, no additional speed sensor is arranged in the compressor. During the operation of the compressor, the speed of the motor can be estimated by designing an observer for the motor current, voltage and other signals. However, when the motor idles in inertia during shutdown, the current of the motor cannot be obtained by the observer. This article introduces a speed identification method based on phase-locked loop in the idle state of the motor, which can accurately obtain the rotational speed of the motor in the idle state, and provides a solid guarantee for the unbalance compensation of the magnetic bearing in the whole process. The bearings can be stopped in time when the machine stops, making the shutdown process more intelligent.

In this paper, a dual gain control (DGC) technology is proposed to achieve large gain variation range and good gain flatness for every controllable gain in ultra wide frequency band. The DGC technology includes a modified current mirror structure and a dynamic signal feedback structure. Based on the DGC technology, a variable gain amplifier with both large dynamic gain variable range and good gain flatness in the ultrawideband of 3.1∼10.6 GHz are realized.

In this paper, the optical gain characteristics and optical high frequency characteristics of an InP-based uni-traveling-carrier double heterojunction phototransistor (UTC-DHPT) are illustrated. The detailed analysis of UTC effects on those perfomaces show that UTC transport mechanism successfully weaks the space charge effect in the collector junction and breaks the limitation of low mobility of the holes. Compared with traditional single heterojunction phototransistor (SHPT), UTC-DHPT improves its processing ability of high power optical signal and provides high saturation current, high responsivity and high response speed simultaneously.

Compared with BVCEO, BVCES is more related to collector optimization and more practical significance, so that BVCES × fT rather than BVCEO × fT is employed in representing the limit of the product of the breakdown voltage-cutoff frequency in SiGe HBT for collector engineering design. Instead of a single decrease in collector doping to improve BVCES × fT and BVCEO × fT, a novel thin composite of N− and P+ doping layers inside the CB SCR is presented to improve the well-known tradeoff between the breakdown voltage and cut-off frequency in SiGe HBT, and BVCES and BVCEO are improved respectively with slight degradation in fT. As a result, the BVCES × fT product is improved from 537.57 to 556.4 GHzV, and the BVCEO × fT product is improved from 309.51 to 326.35 GHzV.

In this paper, the positive influence of a uni-traveling-carrier (UTC) structure to ease the contract between the responsivity and working speed of the InP-based double hetero-junction phototransistor (DHPT) is illustrated in detail. Different results under electrical bias, optical bias or combined electrical and optical bias are analyzed for an excellent UTC-DHPT performance. The results show that when the UTC-DHPT operates at three-terminal (3T) working mode with combined electrical bias and optical bias in base, it keeps a high optical responsivity of 34.72 A/W and the highest optical transition frequency of 120 GHz. The current gain of the 3T UTC-DHPT under 1.55-μm light illuminations reaches 62 dB. This indicates that the combined base electrical bias and optical bias of 3T UTC-DHPT can make sure that the UTC-DHPT provides high optical current gain and high optical transition frequency simultaneously.