This dissertation addresses the design of monolithically integrated phase shifters at S- and L- frequency bands using a commercially available GaAs process from Triquint. The focus of the design is to operate over a wide bandwidth with full 360° phase shift capability, 50 Ω input/output impedance match and low RMS phase and gain errors. The first version of the design is based on passive all-pass phase shifters integrated with wideband amplifiers to compensate for insertion loss. This design uses a 4-bit system to achieve the required phase shift and each bit consists of 3 sections of all-pass filters designed at separate frequencies within the 0.8 – 3 GHz band. Simulation results show a complete 360° phase shift with RMS gain error of less than 0.6 dB and RMS phase error of less than 2.5°. The system is also shown to achieve good input and output impedance matching characteristics. However, the fabricated prototype fails to perform with full functionality due to the excessive number of passive inductors in the design and the resulting mutual coupling. The mutual coupling issue could be solved by spacing out the layout to allow more separation among the inductors. Unfortunately, in the S- and L-bands, this is not an option for this research work as the fabricated design already uses the maximum allowed chip size as determined by the foundry. In addition, larger chip sizes considerably increase the cost in practical applications. To address the challenging needs of small size, wide bandwidth and low frequency applicability, the second design introduced in this dissertation proposes a novel phase shifter implementation that utilizes tunable active differential inductors within all-pass networks. The inductor tuning is used to achieve phase shifts up to 180⁰. A switchable active balanced to unbalanced transition circuit (balun) is included in front of the all-pass network to complement its phase shift capability by another 180°. In addition, the all-pass network is followed by a variable gain amplifier (VGA) to correct for gain variations among the phase shifting states and act as an output buffer. Although active inductors have been previously used in the design of various components, to the best of our knowledge, this is the first time that they have been used in an all-pass phase shifter. The approach is demonstrated with an on-chip design and implementation exhibiting wideband performance for S and L band applications by utilizing the 0.5 µm TriQuint pHEMT GaAs MMIC process. Specifically, the presented phase shifter exhibits 1 × 3.95 mm2 die area and operates within the 1.5 GHz to 3 GHz band (i.e. 2:1 bandwidth) with 10 dB gain, less than 1.5 dB RMS gain error and less than 9° RMS phase error. Comparison with the state-of-the-art MMIC phase shifters operating in S and L bands demonstrates that the presented phase shifter exhibits a remarkable bandwidth performance from a very compact footprint with low power consumption. Consequently, it presents an important alternative for implementation of wideband phase shifters where all-passive implementations will consume expensive die real estate.

As wireless devices and radar systems become more ubiquitous, there is a growing need for wideband multi-standard RF-SOCs. To enable the advantages of multi-standard systems, reconfigurable RF front ends are needed. Because of the large number of RF signals in wideband systems, tunability and linearity become important parameters. Prior work has shown tunable LC filters to be advantageous in the microwave regime. A balanced-to-unbalanced (balun) transformation circuit is required to support the differential nature of a tunable LC filter. An active balun that also performs as a transconductor to drive the LC tank would relax the design requirement for the LNA and remove a passive balun that would have to precede the LNA. This thesis discusses the linearization of active baluns and presents a comparison between two 4 to 7 GHz tunable BPF designs with active baluns implemented in 0.18 μm SiGe BiCMOS technology. Fourth order filtering is achieved by subtracting two 2nd order LC-tanks. This approach allows 3-dB bandwidth to be tunable from 10% to 20%. In each design, a linearized input active balun is employed to drive the LC-tanks from a single-ended input while preserving noise figure and IIP3 performance. Two different linearization techniques are applied for the balun designs. Simulated NF ranges from 7.5 to 13 dB and IIP3 averages about 5 dBm with the peak value of 21 dBm. / Master of Science / As wireless devices and radar systems become more ubiquitous, there is a growing need for Radio Frequency (RF) integrated circuits that can support multiple frequency bands and standards. Because of the large number of RF signals, robust tunability and power handling of the electronics become important parameters. Power handling is important because the amplifier and the filter can generate distortions if the power going through them becomes too high. Prior work has shown integrated tunable inductor-capacitor (LC) resonance based filters to be advantageous in the microwave frequency regime compared to integrated switched capacitor based filters. A balancedto-unbalanced (balun) conversion of the RF signals is needed to support the differential nature of the LC resonators. This thesis discusses transistor-based balun designs that can be integrated into front-end LC filter chips. The goal is to reduce distortion in the filter under the present of large number of RF signals and to keep noise of the circuit in reasonable range. The designs are implemented in 0.18 μm SiGe BiCMOS integrated circuit technology and simulated in commercial computer aided design software; predicted performance is competitive with the state of the art. The fabricated chips will be characterized in future work.