Recently, mm-wave applications in CMOS have become feasible and attractive thanks to the aggressive scaling of CMOS technology. W-band frequency, which is defined from 75GHz to 110GHz, is suitable for imaging and radar applications due the small wavelength of EM wave and high detection resolution. The imaging and radar system can be widely used for applications such as medical imaging, security imaging and anti-collision radar. For these applications, a signal source with high output power and high purity is needed to work as the transmitter. However, there are many challenges to implement the W-band transmitters in the low-cost CMOS process. Firstly, a high-purity local oscillator (LO) is required, which is normally designed as the phase-locked loop (PLL). To properly lock the...[ Read more ]

Recently, mm-wave applications in CMOS have become feasible and attractive thanks to the aggressive scaling of CMOS technology. W-band frequency, which is defined from 75GHz to 110GHz, is suitable for imaging and radar applications due the small wavelength of EM wave and high detection resolution. The imaging and radar system can be widely used for applications such as medical imaging, security imaging and anti-collision radar. For these applications, a signal source with high output power and high purity is needed to work as the transmitter. However, there are many challenges to implement the W-band transmitters in the low-cost CMOS process. Firstly, a high-purity local oscillator (LO) is required, which is normally designed as the phase-locked loop (PLL). To properly lock the PLL, a mm-wave frequency divider chain is needed with wide locking range. Besides, a voltage-controlled oscillator (VCO) with good phase noise and wide tuning range is also required to operate at mm-wave frequency. Secondly, a power amplifier (PA) with high output power and efficiency is needed to generate and radiate the high-power signal to increase the operation range of the imaging and radar system. As the operation frequency is close to f_max, the maximum available gain of the transistor will drop, which makes the design of PA very challenging.

In the first part of this dissertation, the building blocks of mm-wave LO generation are discussed. Several novel circuits are proposed to overcome the challenges of mm-wave PLL. Specifically, frequency-tracking injection-locked frequency divider (ILFD) is proposed to achieve ~40% locking range at 60GHz, which is the widest among existing solutions. Two ILFDs based on transformer-distribution tank are also proposed and designed to achieve comparable locking range with lower cost. The proposed two ILFDs are the first to achieve FoM (=locking range/power consumption) higher than 10GHz/mW with small chip area. To further save power, an ultra-low-power ILFD is also proposed consuming only 0.44mW power with comparable locking range. Moreover, the injection-saturation problem is also observed, discussed and solved in this work. In addition to ILFDs, switched-transformer technique is also proposed to enhance the tuning range of mm-wave VCO with competitive phase noise. The proposed switch-transformer VCO can operate at two bands to achieve >20% tuning range with FoM_T of -187dBc/Hz and has very simple scheme for cascading, which is suitable for PLL integration.

Secondly, an ultra-low-power PLL operating at 50/100GHz is designed and demonstrated. The PLL measures competitive phase noise of -94dBc/Hz at 1MHz offset with only 14.1mW power consumption, which makes it suitable for the LO generation of W-band imaging/radar transmitters. Besides, embedded phase shifter is designed and demonstrated in the PLL. The output phase of PLL can be tuned continuously to cover 360° phase shift with 3.9° resolution. The amplitude variation of PLL output is less than 0.1dB across the total phase tuning range, which is suitable for phased-array applications.

To improve the efficiency and power gain of PA, the injection-locked technique is introduced. As the imaging and radar systems are constant-envelope systems, linearity of PA is not a problem. As a result, the injection-locked technique can be utilized to introduce positive feedback to the PA and thus enhance the gain and efficiency. To further improve the output power of PA, power-combining scheme is adopted in the proposed transmitters. The first proposed W-band transmitter is a preliminary work based on 2-way power combining. The 2-way transmitter contains a low-power PLL operating at 47GHz and frequency multipliers/PAs operating at 94GHz. Thanks to the injection-locked technique, only two stages of PAs are needed which significantly reduces the power consumption. Besides, the 2-way power combining scheme can enhance the output power by 3dB theoretically. The proposed two-way TX measures a peak output power of 11.1dBm and a peak efficiency of 9.3%. The second W-band transmitter is a significantly improved version of the first W-band TX. Firstly, to further improve the output power, the 4-way power combining scheme is utilized. Secondly, the single-stage neutralized injection-locked PA is designed and proposed to further enhance the efficiency. Furthermore, spur cancellation scheme is proposed in the PLL to reduce the reference spur and improve the jitter. Finally, automatic-tuning scheme is proposed to cancel the phase mismatch between different paths of the power-combining PA to achieve the optimal output power. The proposed 4-way power combining PA can achieve peak output power of 15.3dBm and efficiency of 9.6%, which can be readily used as the signal source for imaging and radar applications.