A fully integrated multi-band ED-mode pHEMT VCO using variable transformer and switched resonator

A systematic approach to the design of a reconfigurable LC-coupled voltage-controlled oscillator (VCO) is proposed in this article. The focus is on the choice of the reactive elements of the resonance tank which are most suitable to switch to the desired oscillation frequencies. The optimum Q of the tank will be determined by the selected component. We report a 0.5-μm enhancement-depletion (ED) mode pHEMT (HEMT, high-electron mobility transistor) multiple-frequency VCO, and the generation of multiple frequencies are achieved using switched resonator topology. LC-tank circuit is built by square transformers. By careful selection of the reactive elements, evenly distributed results showed at each designed band. The multi-band ED-mode pHEMT VCO showed the output power of -4.7dBm for 2GHz band, -6.67dBm for 3.86GHz band and -5.9dBm for 4.5GHz band, respectively. The phase noises at 1MHz offset frequency from carrier were -112.8dBc/Hz for 2GHz, -105dBc/Hz for 3.86GHz and -103.3dBc/Hz for 4.5GHz, respectively. The total chip size is only 1.17×0.83mm ².