| dc.description.abstract | The ultra wide-band (UWB) systems are demanding for communication systems, radars, or spectroscopy stems. Recently, researchers have focused on expanding the use of RF/Microwave circuits and systems for multi-disciplinary applications. This dissertation aims to find new ways to integrate microwave broadband (MB) sensors and systems on CMOS integrated circuits (ICs) since system on chip (SoC) has great potential in the IC industry due to having a cheaper cost, more functionality, and smaller area. However, integration of these systems and sensors is challenging for their high-frequency operation, small area, low power consumption, required high sensitivity and accuracy. Furthermore, for today’s microwave and mm-wave circuits and systems, miniaturization is an inevitable requirement. Therefore, developing novel miniaturized sensors/systems to reduce the physical size of the entire system while keeping their high-performance characteristics is highly desirable.
Various solid and liquid materials either absorb, transmit or reflect the microwave signal differently depending on several parameters such as their molecular structures, material compositions, shapes, and thicknesses. CMOS broadband dielectric spectroscopy (BDS) systems in RF/microwave frequencies intend to distinguish materials based on their complex relative permittivity, a unique response to an external microwave electric field at different frequencies. The CMOS BDS systems make it feasible to characterize materials over wide frequency ranges using a silicon-based mm-sized integrated chip that miniaturizes the overall system with low fabrication cost, high accuracy, and a smaller sample volume of the material under test (MUT). Due to its non-destructive, label-free, and real-time nature, microwave broadband dielectric spectroscopy (MBDS) is promising for various applications, such as food and drug safety, chemical/biological sensing, oil exploration and processing, disease diagnosis/tissue characterization, and biothreat detection. Traditional MBDS systems utilize either frequency-domain (FD) or time-domain (TD) measurement techniques. Conventional FD methods require bulky, heavy, and expensive instruments such as a high-cost vector network analyzer (VNA) and measurement setup that restrict the use of the spectroscopy systems to only special applications in industry and laboratories. On the other hand, miniaturized CMOS TD MBDS systems first capture the output in the TD and then convert it to the FD using the fast Fourier transform (FFT), providing the MUT’s dispersive and dissipative dielectric behavior versus frequency, while they can be convenient, cost and time-efficient, and have the potential of being portable in comparison with those FD methods. This dissertation addresses two CMOS integrated TD UWB spectroscopy systems for liquid chemicals’ dielectric permittivity characterization.
In the first project, the first CMOS TD MBDS system with a homodyne RF transceiver architecture including an on-chip multitone excitation pulse generation and the contactless sensor consisting of two UWB Vivaldi antennas located in the near-field region is presented. The contact-less system is implemented in a bistatic free space radar method where two antennas are placed on either side of MUTs, and the transmission signal is measured in TD to identify the complex permittivity from the phase delay and the amplitude mismatch introduced by the MUTs at the transmitted signal. The baseband signal is upconverted to RF frequencies in the transmitter using a UWB single-sideband (SSB) mixer to suppress the lower sideband of the exciting signal and prevent the signal distortion at the configured dc-free direct down-conversion receiver output. The system sub-blocks are designed with flat gain and constant group delay over the frequency range of 3-10 GHz to alleviate the impact of the entire system on MUT characterization. A prototype is fabricated in 65-nm CMOS process with an active chip area of 1.24 mm2. The complex dielectric permittivity of different pure organic chemical liquids and mixtures has been detected and reported. The proposed CMOS MBDS system achieves an RMS permittivity error of less than 0.2%, and 0.4% for r and r over the entire operation bandwidth.
In the second project, the first CMOS integrated UWB microwave coherent dual-comb spectroscopy (DCS) system with two on-chip frequency combs that have tunable and slightly different repetition frequency rates is presented for liquid chemicals detection. One of the frequency combs (CombRF ) interrogates a coplanar waveguide (CPW) planar transmission line sensor loaded with the material under test (MUT) while the other identical empty sensor is excited by the second comb (CombLO). Two frequency combs are then heterodyned using a UWB mixer to generate the dual-comb output representing the MUT’s properties from microwave frequencies mapped to low-frequencies, eliminating the need to use high-frequency analog-to-digital converters (ADCs). To achieve detection of both real and imaginary parts of the complex permittivity of liquid sam-ples, an adaptive sampling method along with phase-locking of all sources is utilized. The 3-10 GHz microwave DCS system is fabricated in 65-nm CMOS process and occupies a chip area of 1.98 mm2. The proposed CMOS broadband microwave DCS system achieves an RMS permittivity error of less than 0.24%, and 0.37% for r and r over the entire desired bandwidth compared to sensor outputs. | |
