An UWB VCO with tunable active inductors using a 0.18-m CMOS standard process was presented in this article. The active inductors provide inductance from 1.7 to 3.6 nH with the qualityfactor Ͼ10 via a tunable feedback resistance. By utilizing the tunable active inductors in VCO design, the novel VCO exhibits oscillation frequencies from 2.16 to 6.16 GHz with a tuning-range of more than 100%. Comparisons of the proposed VCO with a conventional topology show that the proposed circuit achieves better performance coupled with a significantly wider tuning-range and compact chip size. The designed VCO can be used for the applications in low-frequency band of UWB system.
ACKNOWLEDGMENT
A new class of electronically beam-steerable corrugated substrate integrated waveguide (CSIW) slot array antenna operating at 26 -29 GHz has been developed. The conventional via based walls of SIWs or stub-based walls of CSIWs have been replaced with an inter-digitated capacitor (IDC) structure to enable reconfigurability. This novel IDC-CSIW is shown to have a lower transmission loss compared with conventional CSIWs in the literature. A new mathematical method has been described to calculate the cut-off frequency of CSIWs. The surface of the IDC-CSIW is then loaded with longitudinal slots, building a leaky-wave architecture. Radiation from individual slots is controlled by shorting the IDC at specific points using PIN diodes. The antenna is fed at either end using a singlepole-double-throw (SPDT) switch to achieve a 2D reconfigurable beam. A compact switched array of two IDC-CSIWs is demonstrated to produce a continuous full sector coverage of 120° in the azimuth plane, and ±15° in the elevation plane, providing a 2D beam-steer with a stable gain of ~13.5 dBi and an efficiency greater than 80%.
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