This paper presents an LC VCO with auto-amplitude control （AAC）, in which pMOS FETs are used,and the varactors are directly connected to ground to widen the linear range of Kvco. The AAC circuitry adds little noise to the VCO but provides it with robust performance over a wide temperature and carrier frequency range.The VCO is fabricated in a chartered 50GHz 0.35μm SiGe BiCMOS process. The measurements show that it has - 127. 27dBc/Hz phase noise at 1MHz offset and a linear gain of 32.4MHz/V between 990MHz and 1.14GHz.The whole circuit draws 6. 6mA current from 5V supply.
A DC-offset cancellation scheme in a 5GHz direct-conversion receiver compliant with the IEEE 802.11a wireless LAN standard is presented. An analog feedback loop is used to eliminate the DC-offset at the output of the. double-balanced mixer. The test results show that the mixer with the DC-offset cancellation circuit has a voltage conversion gain of 9.5dB at 5.15GHz, a noise figure of 13.5dB, an IIP3 of 7.6dBm, a DC-offset voltage of 1.73mV eliminating 76% of DC-offset,and a power consumption of 67mW with a 3.3V supply. The direct conversion WLAN receiver has been implemented in 0.35μm SiGe BiCMOS technology.
