A 2-Bit Voltage-Controlled Oscillator (VCO) for Multiband Wireless Applications

This letter presents a fully-integrated 2-bit CMOS voltage-controlled oscillator (VCO) along with a 2-bit buffer, which delivers the highest RF output power among recently reported state-of-the-art to the best of the authors’ knowledge. The proposed 2-bit VCO is designed and fabricated in a $0.18-\mu \text{m}$ CMOS process with a die size of 1.2 mm $\times$ 1.2 mm, which covers four frequency bands of interest. Fine-tuning at each of the four frequency bands is also obtained by utilizing two varactors. The proposed 2-bit VCO delivers a single-ended output power of 6.5/6.8/10.6/12.5 dBm at 0.930/1.157/1.436/1.917 GHz, respectively. This 2-bit VCO can cover frequency ranges of 930–1005, 1046–1157, 1248–1436, and 1540–1917 MHz, thus providing a total frequency bandwidth of 751 MHz. The proposed 2-bit VCO at each frequency band demonstrates −99, −93, −90, and −86 dBc/Hz for phase noise, and −150, −150, −160, and −168 dBc/Hz for figure-of-merit (FOM), respectively.