Periodic structures and lumped elements in microwave passives

Licentiatavhandling, 2004

The ambition of this work is the incorporation of ferroelectric varactors as tuneable elements in Si integrated circuits (ICs). This thesis presents partial fulfillments of the work. The achieved results are divided into two rather separate topics: "tuneable periodic structures using ferroelectric materials" and "synthetic transmission lines in MMICs". Periodic structures demonstrate the potential of the ferroelectric varactors. The concept of tuneability was first demonstrated in one dimensional (1D) electromagnetic bandgap (EBG) structures. Then, tuneable true-time delay lines with a delay time per unit length of 40 ps/mm, losses of 0.049 dB/ps, and tuneability 20 % were accomplished. Integration with BCB is demonstrated by simple series resonators with varactors integrated into the groundplane of a microstrip line. The second order lattice balun (SOLB), a novel balun topology based on right/left handed (RH/LH) transmission lines (TLs), is synthesized. The circuit demonstrate excellent balancing performance over bandwidths larger than one octave. Lumped quadrature power splitters (LQPSs), also based on RH/LH TLs, are capable of, for many applications, acceptable quadrature generation over octave bandwidths. Closed form design equations for the component values are derived for both the SOLB and the LQPSs. The theoretical work is validated by implementations in a commercial GaAs MMIC foundry. For the balun, the measured amplitude and phase errors are less than 1.1 dB and 3 degrees , respectively, over the frequency range 1.6-3.4 GHz. The re°ection loss is better than 17 dB within the same frequency range. The LQPSs have amplitude and phase errors of 0.3 dB and 3 degrees within the range 2-3 GHz. The re°ection loss is better than 10 dB within the same range.