| dc.description.abstract | Phase shifters are essential components in phase arrays. In most applications, full 360° phase shift is necessary. In the past, all-pass networks (APNs) have been used for phase shifter design. When the coupling coefficient k of the two inductors in an APN is positive, the phase shift can be increased. In this thesis, we design analog phase shifter based on magnetically coupled all-pass networks (MCAPNs) with positive k, aiming to achieve full 360° phase shift with only two stages of the magnetically coupled all-pass phase shifters.
The proposed MCAPN-based analog phase shifters are designed to operate at 2.45 GHz. The variable capacitors required in the phase shifters are realized using ferroelectric varactors. Based on different types of layout of the coupled inductors, three different single-stage phase shifters and two different two-stage phase shifters are designed. Simulation results show that, when the ferroelectric varactors exhibit a tunability of 2.3, all single-stage phase shifters are able to provide a full 360° phase shifter with an insertion loss less than 6 dB and return losses greater than 10 dB. Furthermore, both two-stage phase shifters are able to provide a full 360° phase shifter with an insertion loss less than 13 dB and return losses greater than 10 dB.
The proposed phase shifters are fabricated using a ferroelectric integrated passive device (IPD) process developed by our lab. The fab process is done on a high-resistivity silicon substrate and offers four front-side metal layers, backside metal, and through-silicon vias (TSVs). The devices that can be fabricated with this process include ferroelectric thin-film varactor, spiral inductor, and CrSi2 thin-film resistor. Measurement results show that we have successfully fabricated the ferroelectric varactors, the ferroelectric varactors with TSVs, the CrSi2 thin-film resistors, and coupled spiral inductors. However, due to the low yield, no complete phase shifter responses can be measured.
In this work, we design MCAPN-based analog phase shifters with large amount of phase shift, and fabricate them with the ferroelectric IPD process developed by our lab. Due to the low yield, only individual passive devices are measured. In order to successfully realize a complete circuit, the yield still has to be improved in the future.
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