In this communication we describe a frequency scanning slot array in μcoaxial technology operating from 87-102 GHz. The array achieves a 30° scanning angle over a 15 GHz bandwidth. The device is fabricated using the PolyStrata sequential copper deposition process, which guarantees low loss and small size. A double-array prototype, with a gain of 14 dB at 94 GHz, is fabricated and tested.

This paper describes frequency scanning slot arrays operating from 130 to 180 GHz. The arrays are micro-fabricated using the PolyStrata sequential copper deposition process. Measured reflection coefficient and radiation patterns agree with HFSS full-wave simulations. The voltage standing wave ratio is less than 1.75:1 over the entire frequency range, and the measured scanning is 1.04 degrees GHz from 130 to 150 GHz and 32.5 degrees over the full frequency range. The measured gain is 15.5 dBi for a 10-element array at 150 GHz and 18.9 dBi for a 20-element array at 150 GHz with about 3 dB of variation over the scan range.

This paper presents miniature broadband bias tee networks designed in a micro-coaxial environment. The process for fabricating the air-filled coaxial lines by wafer-scale sequential metal deposition, referred to as PolyStrata™, enables hybrid assembly of surface-mount components such as inductors and capacitors, enabling DC blocks and RF chokes. The microcoaxial lines can be designed with a wide variety of characteristic impedances fabricated in the same process, allowing for easier matching to active devices such as power amplifiers, which typically have low input and output impedances. In this paper, bias tee networks in both 12Ω and 50Ω environments are demonstrated with 0402 capacitors and 0402 inductors, as well as with monolithically integrated coil inductors. The measured performance shows 14 dB insertion loss from 4 to 16 GHz with a better than 0.75 dB return loss and up to 5 A power handling in a circuit with a 8.3 mm2 footprint.

This paper presents several micro-coaxial broadband 2 : 1 Wilkinson power dividers operating from 2 to 22 GHz, a 11 : 1 bandwidth. Circuits are fabricated on silicon with PolyStrata technology, and are implemented with 650 mum times 400 mum air-supported micro-coaxial lines. The measured isolation between the output ports is greater than 11 dB and the return loss at each port is more than 13 dB over the entire bandwidth. The footprints of these dividers can be miniaturized due to the high isolation between adjacent coaxial lines and their tight bend radius. For higher power handling, larger lines with a cross section of 1050 mum times 850 mum are also demonstrated. The effect of mismatch at the output ports is investigated in order to find the power loss in the resistors.

This paper discusses fundamental properties of rectangular micro-coaxial lines fabricated in the PolyStratatrade process for broadband applications from 2-20 GHz. The possible impedance ranges for coaxial lines implemented with both five and eleven Cu layers are discussed and compared with measured results for the lowest impedance (8 Omega) line. Power handling and thermal properties of these miniature lines are analyzed and measured. A 50 Omega line with outer conductor cross-section of 600 mum by 400 mum is experimentally shown to handle 53 W at 2:5 GHz with a 10% duty cycle. Integration with active components is investigated and a 1-10 GHz measurement of a GaN 50 Omega MMIC amplifier shows minimal performance degradation relative to on-wafer measurements.

An overview of components designed and implemented in the PolyStrata micro-coaxial technology at millimeter-wave frequencies will be presented. The components are designed and characterized at the University of Colorado, and fabricated by Rohm and Haas Electronics, in collaboration with BAE Systems. Micro-coaxial air-filled cables with purely TEM propagation up to 450 GHz are fabricated using sequential deposition of 5 to 11 layers of copper, and used to implement couplers, hybrids, Wilkinson dividers/combiners, impedance transformers, etc. from microwave frequencies to W band. Some advanced concepts for THz components are also achievable in this technology.

In this work, a rectangular coaxial transmission line based power amplifier is discussed. This transmission line is created by sequential photolithography and plating processes, resulting in a very wide band, dispersion-less transmission medium which includes integrated passive components. This approach yields a number of advantages over conventional microstrip circuits. This 3D micro-machining technology, called PolystrataTM technology, in which the circuit is the package, and the package is the circuit, enables one other important and far reaching advantage.

Date The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. This thesis presents the analysis, design, and measurements of the front end of a bandpass delta-sigma modulated RF transmitter. Currently, there is considerable interest in " direct " digital RF transmitters for simultaneous multi-task transmitting, where extraordinarily linear signal conversion is required. The delta-sigma modulated conversion provides a promising approach. Conceptually, a delta-sigma modulated RF transmitter has three stages: a bandpass delta-sigma modulator, a one-bit power digital-to-analog converter (DAC), and bandpass filtering circuits. The one-bit power DAC has primary importance in the transmitter implementation , because it directly determines the system linearity performance. In this thesis, a circuit approach is described for analyzing the generation mechanisms of the nonlinear inter-symbol interference (ISI) in the one-bit power DAC. Single-ended and differential converter topologies are theoretically analyzed and experimentally characterized with a three-tone delta-sigma test signal. Additionally, the linearity performance of single-ended and differential configuration DACs with different bandpass filters is discussed, where the fundamental idea is that the load-circuit effect on the linearity performance of the DAC is determined by its input impedance. iii Dedication To mom, dad, and Jia, who I cherish and love the most. Acknowledgments The last six years of the graduate study toward my Ph.D. thesis was a very special and wonderful journey in my life. I am grateful to all the people that I have worked and lived with. Without you, it would not be as colorful as what I memorize today. Laboratory for his suggestions, technical inputs and constructive comments on this thesis work. My sincere thanks also go to the committee members: ideas and help that they offered me generously. I thank Dr. Nestor López and John Hoversten for the discussions on power amplifiers. I would also like to extend my thanks to the past and present members of the Active Antenna Group: Dr. and the others. Without you, I could not image how I would get through the time when I first came to the United States. Finally, I want to thank my parents and my wife, Jia, for their continuous love and understanding. I am truly grateful for being in such a family.