With continued process scaling, CMOS has become a viable technology for the design of high-performance low noise amplifiers (LNAs) in the radio frequency (RF) regime. This paper describes the design of RF LNAs using a geometric programming (GP) optimization method. An important challenge for RF LNAs designed at nanometer scale geometries is the excess thermal noise observed in the MOSFETs. An extensive survey of analytical models and experimental results reported in the literature is carried out to quantify the issue of excessive thermal noise for short-channel MOSFETs. Short channel effects such as channel-length modulation and velocity saturation effects are also accounted for in our optimization process. The GP approach is able to efficiently calculate the globally optimum solution. The approximations required to setup the equations and constraints to allow convex optimization are detailed. The method is applied to the design of inductive source degenerated common source amplifiers at the 90 nm and 180 nm technology nodes. The optimization results are validated through comparison with numerical simulations using Agilent’s Advanced Design Systems (ADS) software.
To improve the Signal to Noise Ratio and the precision of data acquisition systems in the condition of broad bandwidth, an adaptive narrow-band filter circuit has been designed for obtaining weak signals in low-frequency domain. And the problems of classic filter circuits, such as wave form distortion and suffering from non-linearity of varactors, can be solved by the novel design in replacing varactor with voltage control capacitor. Simultaneously, by improving LRC filter circuit, our designs also can increase quality factor in traditional RC filter circuit. Therefore, this design has great advantages over classic filter circuits for its narrow frequency band, high quality factor and low signal deformation. The above properties of this circuit can make it used widely in removing noise for modulation and acquisition circuits with high precision, and can be used to obtain accurate band-pass filtering in low frequency bands, which has been verified by experiments showing superior advantages of improving the SNR and filtering effects.
The paper analyzed flow characteristics in vortex diode with double tangential tube by numerical simulation. Compared to traditional vortex diode with one tangential tube, the structure of double tangential tube can reduce the forward resistance and improve overall performance. The symmetrical design adopted in vortex diode with double tangential tube; the internal flow field in chamber showed symmetrical distribution in the reverse flow, which can improve the flow stability and accelerate the convergence speed in simulation.
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