A 47-GHz Voltage Controlled Oscillator in 90-nm CMOS Process

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In this thesis, a low-cost and compact 47-GHz voltage-controlled oscillator in a 90-nm CMOS technology for millimeter-wave communication is proposed. This circuit uses the cross-coupled transistors to generate a negative resistance that makes it easier to maintain oscillation conditions at high frequencies. The VCO increase the output power to 2.7 dBm with a buffer and a voltage amplifier. The power consumption is 49.65 mW from a 1.2 V supply. In order to increase the tuning range of the oscillator, this thesis proposes to add 8 sets of switchable capacitors to the oscillator circuit, so that it can increase the tuning range of the VCO by switching the capacitors. While the oscillator is operated at 47-GHz, the single tuning range is 3.16%, and the total tuning range is 10.38%. The phase noise at 1 MHz offset from the carrier is -86.82 dBc/Hz in post-simulation. In order to provide the eight digital control bits to switch the capacitors of the VCO, and to avoid adding too much pads in this chip result in increasing the chip size, this thesis propose a low-delay and low-cost 3-wire digital control circuit that added to the VCO front end. A series of digital signals are provided to the 3-wire circuit through the communication interface of the SPI, and the digital control bits in the signal are stored in the shift register. Then, using the parallel register, the required eight control bits are extracted from the received digital signal to the VCO. At this time, only three input pins (Clk (Clock), LE(Parallel-out Enable), D_in(Digital Data)) are needed in this chip to generate the digital control bits required by the oscillator so that the pads for inputting the digital control bits can be effectively reduced, and the chip size will be greatly reduced.