Design of highly controllable and low jitter CMOS circuits for wide-band and radiation applications.

In recent years, ultra-wideband (UWB) signal based radar and imaging systems have been investigated for the use in harsh industrial environments. UWB localization can be used for tracking robots, persons, etc. The present work extends the use of UWB in harsh industrial environments to radiation environments. In these environments, robust UWB systems can extend the capabilities of for instance robotics used in radiation environments. Next to the ranging capabilities, UWB imaging can be used to create an image of the surroundings or see through the surface of an non-transparent object.

This work focuses on the design of universal CMOS circuits, which can be used in the proposed harsh environments. To estimate the effect of the many applications and different operation conditions, a 1-D transmission line model has been proposed. This model estimates the reflection and transmission parameters of the used electromagnetic (EM) signals for a certain application. These results can then be used to determine the minimal hardware requirements.

In order to be able to easily adapt to the changing environment (depending on the application) and to the different regulations, an industrial UWB sensor must be highly adjustable. In the transmitter, a mixer based UWB pulse generator structure is proposed. Here, a baseband pulse will be up-converted to the correct frequency spectrum using a frequency mixer. This allows to decouple the center frequency and spectral width of the UWB pulse, and so allowing for a highly flexible output signal.

In a first part of this dissertation, two versions of a UWB baseband pulse generator are presented and designed in 40 nm CMOS. The first chip introduced a triangular wave baseband pulse generator with a pulse width adjustable between 280 ps and 7.5 ns. However, over this entire pulse width tuning range, the pulse amplitude has a 38\% variation. In the second chip, this pulse amplitude variation is minimized by implementing an independent pulse amplitude control loop. This system reduces the amplitude variation to only 13% while still providing a 660 ps to 3.8 ns pulse width tuning range.

Next, a novel frequency mixer architecture is proposed in order to compensate the Voltage Controlled Oscillator (VCO) leakage signal at the output of the mixer. The design introduces the use of a replica mixer, which only generates this leakage signal. The replica's output can then be used to compensate the leakage at the output of the original frequency mixer.

A second main part of the research focuses on a Radiation Hardened By Design (RHBD) time-accurate data transmitter and receiver design. In the envisaged ranging and imaging systems, the information is embedded in the timing of multiple signals. In harsh environments it may be useful to transfer these signals over a long distance. Here, this is done using signals based on the Low Voltage Differential Signaling (LVDS) / Scalable Low Voltage signaling (SLVS) standard. To enable the use in time accurate systems, both the transmitter and the receiver need to minimize the difference in the rise and fall output delay. Additionally, the jitter of both systems needs to be minimized. Hence, any noise or distortion introduced by this link will decrease the resolution of the entire system. Both the transmitter and receiver are designed in 65 nm CMOS.

In the receiver, the propagation delay of the rising and falling output edges are equalized using a replica receiver, measuring this imbalance. This measured imbalance is then used to adjust the slew rate of the output edges. This compensation loop minimizes the variations in the output delays of the rising and falling edges generated by the process, temperature and power supply (PVT) variations and the total ionizing dose (TID) radiation effects. The proposed design only showed a 0.5 ps increase in this imbalance at a TID radiation level of 500 Mrad (= 5 Mgy). This is a 27 times improvement compared to the open loop receiver. Additionally, the effect of the mismatch between the original and replica receiver is analyzed.

In the time-accurate data transmitter, the RHBD is mainly focused on the architecture. The proposed design uses a resistor based current driver architecture. Hence, only an imbalance in these resistors will have an effect on the propagation delay. Results showed a low imbalance in the propagation delay of the output edges due to process corners, temperature and power supply variations. Moreover, at a TID level of 500 Mrad (= 5 Mgy), the proposed architecture only shows a 0.55 ps increase in the imbalance between the rise and fall output delays, without the need of adding extra compensation loops. Finally, the proposed design is capable of generating a highly flexible pre-emphasis signal.