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In this letter, a transformer-based current-reuse Colpitts voltage controlled oscillator (VCO) is proposed, which combines a N-type and P-type Colpitts oscillators using a 5-port transformer in a complementary form to provide the differential outputs. The proposed VCO has low phase noise due to the low noise Colpitts oscillator topology and the negative- ${Gm}$ boosting technique with half of the DC-current consumption using the current-reusing method. The proposed VCO has the frequency tuning range from 8.57 to 10.21 GHz, and shows low phase noise of $-110.6~{\rm dBc}/{\rm Hz}$ at 1 MHz offset frequency at 9.41 GHz and high figure of merit with tuning range ( ${\rm FoM}^{T}$ ) of $-191.8~{\rm dBc}/{\rm Hz}$ . The power consumption is 2.1 mW from 1.2 V supply voltage. The VCO is implemented using 0.13 $\mu {\rm m}$ CMOS process with chip area of 0.45 ${\rm mm}^{2}$ .

This paper presents a new position-determination estimator for trilateration location. The proposed estimator takes the measurement bias into consideration and improves the location accuracy of a mobile location system. In case that a mobile station (MS) utilizes signals from a set of base stations for its location, the computed location is largely affected by nonline-of-sight (NLOS) error in signal propagation. A constrained optimization method in a three-stage estimation structure is proposed to estimate and eliminate the measurement bias contained in each pseudorange and mainly caused by the NLOS error. A linear observation model of the bias is formulated, and the interior-point optimization technique optimally estimates the bias by introducing a feasible range of the measurement bias. It is demonstrated that the new three-stage estimator successfully computes an accurate location of an MS in a realistic environment setting. The location accuracy of the proposed estimator is analyzed and compared with the existing methods through mathematical formulations and simulations. The proposed estimator efficiently mitigates the effect of a measurement bias and shows that the iterated least square (ILS) accuracy of 118 m [67% distance root-mean-square (DRMS)] can be improved to about 17 m in a typical urban environment

An AC free-electron laser (FEL) with a superconductor cavity and a FEL with a plasma wave wiggler are analyzed. The AC FEL has a small effective wiggler wavelength and higher wiggler strength. Therefore, it can supply high-power coherent radiation with a short wavelength. From the linear fluid theory and Maxwell's equations, the dispersion relation is derived. When the coupling term is much less than unity (F >