Method for differential phase delay resolution of phase referencing VLBI technique and its experimental verification

The phase referencing Very Long Baseline Interferometry (VLBI) technique is a newly developed tool to measure the angular position of a deep space exploration probe in the plane-of-the-sky. Through alternating observations between the probe and a nearby reference radio source, their accurate relative angular separation can be obtained from the radio images generated by this technique. To meet the requirements of the current orbit determination software, differential delay should be firstly derived from those radio images. A method to resolve the differential phase delay from the phase referencing VLBI technique is proposed in this paper, and as well the mathematical model for differential phase ambiguity resolution is established. This method is verified with practical measurement data from the Chang’E-3 mission. The differential phase delay between the Chang’E-3 lander and rover was derived from the phase referencing VLBI measurements, and was then imported into the Shanghai astronomical observatory Orbit Determination Program (SODP) to calculate the position of the rover relative to the lander on the lunar surface. The results are consistent with those acquired directly from radio images, indicating that the differential phase ambiguity has been correctly resolved. The proposed method can be used to promote applications of the phase referencing VLBI technique in future lunar or deep space explorations, and more accurate orbit determination becomes promising.

The Truncated Theta-EM Method for Nonlinear and Nonautonomous Hybrid Stochastic Differential Delay Equations with Poisson Jumps

In this paper, we study a class of nonlinear and nonautonomous hybrid stochastic differential delay equations with Poisson jumps (HSDDEwPJs). The convergence rate of the truncated theta-EM numerical solutions to HSDDEwPJs is investigated under given conditions. An example is shown to support our theory.

Design of power-efficient CMOS based oscillator circuit with varactor tuning control

This paper presents a low-power, wide tuning range CMOS voltage-controlled oscillator with MCML (MOS current mode logic) differential delay cell. Voltage controlled oscillator (VCO) circuit is designed in TSMC 0.25 μm CMOS process. To achieve the broad frequency range concept of variable capacitance is employed in the proposed VCO circuit. Source/drain tuning voltage (Vtune) and body bias voltage (Vb) of I-MOS varactor are used to achieve variable capacitance at different I-MOS varactor widths (W). The dual control voltage of I-MOS varactor results in a tuning range from 0.528 GHz to 2.014 GHz. VCO's figure of merit (FoM) is 152.13 dBc/Hz with phase noise of −93.77 dBc/Hz at 1 MHz offset from the oscillation frequency. The proposed VCO dissipates maximum power of 3.127 mW.