## 3 Current Status of the Circuit Component in the MMW Regime
### Voltage Control Oscillator (VCO)
#### 3.5.1 VCO in CMOS Technology  
Figure 14 illustrates the measured phase noise of the published MMW CMOS VCOs. In [165], a CMOS MMW low voltage VCO with the AC-coupled LC tank is reported. Wide tuning range and pushing by the high order harmonics are achieved by using the AC-coupled LC tank, simultaneously. The differential tuning is performed by an extra varactor biasing terminal without large resistors for a differential PLL. In [166], a fundamental double-stacked cross-coupled VCO were implemented in 32 nm SOI CMOS technology. The additional negative source degeneration resistance improves the overall negative resistance of this oscillator, in turn; the loss of the varactor at high frequencies is compensated. As a result, the phase noise and the loop gain will be improved. In [167], a high tuning range and high output power VCO is proposed. The tuning range is enlarged by exploiting either a variable capacitor or controlling the phase/delay between the coupled oscillators. In [168], a novel varactorless VCO is presented. Between the source and drain nodes of the cross-coupled pair, source degeneration and capacitors are adopted to alter the frequency of the VCO. In [169], according to the nonlinear dynamic theory, the phase shift and frequency are dominated by the coupling between the cores. The harmonic power, which is generated by the coupling of the two multiple oscillators, will be transfer to the output without varactors. In [170], the conventional cross-coupled 38 GHz VCO with a doubler was implemented in 65 nm CMOS with a phase noise of \(-\)88 dBc/Hz at 1 MHz offset and a measured output power of 6 dBm at 77 GHz. In [171], the extension of the output frequency range and reduction of the phase noise are achieved by standing-wave transmission line resonators. The VCO, which exploits the standing-wave transmission line resonators, has lower phase noise instead of the one, which does not use.  
Except for the recent published works, some representative MMW VCOs will be illustrated.  
**A V-band VCO and a Q-band VCO** are reported in [172]. The tuning range of the V-band VCO is 16% and the Q-band DCO has 18 bits and 14% tuning range with the variable inductor techniques. The tuning mechanism of the variable inductor, which is composed of a transformer and a variable resistor, is to changing the variable resistor to adjust the inductance. In this fashion, wide frequency tuning range and multi-band operation can be achieved without lowering the operation frequencies. Figure 15. See also, Figure 16. The VCO and DCO are both fabricated in 90 nm CMOS technology. The tuning range of VCO is 9.1 GHz that is from 52.2 GHz to 61.3 GHz. The measured phase noise is about 118.75 dBc/Hz at 10-MHz offset at 61.3 GHz with the output power of \(-\)6.6 dBm. The dc power consumption is 8.7 mW with a 0.7-V supply, and the chip size is 0.28 \(\times\) 0.36 mm\({}^{2}\). S for the DCO, it has a tuning range about 5.8 GHz that is from 37.6 to 43.4 GHz. The measured phase noise is about \(-\)109 dBc/Hz at 10-MHz offset with the output power is \(-\)11 dBm at 43 GHz. The dc power consumption of the DCO is 19 mW with a 1.2-V supply. It has a chip size of 0.5 \(\times\) 0.15 mm\({}^{2}\).  
Figure 14: Phase noise of the recent published MMW CMOS VCOs. Data is taken from [165, 166, 167].  
Figure 15: VCO schematic [172].