| dc.description.abstract | This dissertation focuses on the research of on-chip Ruthroff-type transmission-line transformers. By utilizing the broadband and low-loss on-chip Ruthroff-type transformers, a wideband and high-efficiency power amplifier and a wideband low-loss passive mixer were successfully achieved. Besides, The Integrated Passive Devices (IPD) technology was utilized to further reduce the insertion loss of the transformers and to improve the efficiency of RF circuits. In this dissertation, two types of transformers are presented. The first type is two unbalanced-to-unbalanced (un-to-un) transformers with the impedance transformation ratio of 1:4 and 1:9, respectively. The other type is three balanced-to-unbalanced (balun) transformers with impedance transformation ratio of 1:4, 1:1 and 9:4, respectively. The 1:4 and 1:9 un-to-un transformers were fabricated using IPD process. They exhibit the minimum insertion losses of 0.5 dB and 0.57 dB and the correspondent 1-dB fractional bandwidths of 175% and 140%, respectively. Moreover, utilizing the flip-chip package technology, a CMOS-IPD PA produced using vertical heterogeneous integration of standard 0.18 m CMOS technology and IPD technology was fabricated with an output power of 26.18 dBm, a PAE of 47.4%, and the 1-dB fractional bandwidths of 33.8%. In the balun type of transformers, the 1:4 Ruthroff-type balun was first designed using standard 0.18 m CMOS technology with a minimum insertion loss of 0.71 dB and the 10-dB return loss fractional bandwidths of 94.2% which is defined as the in-band return loss exceeds 10 dB. Utilizing the broadband and low-loss characteristics of Ruthroff-type balun, a simple single-balanced mixer with the balun demonstrates a minimum conversion loss of 12.48 dB with a 3-dB bandwidth from 2.5 to 7 GHz while the LO drive of 6 dBm.
The 1:4 Ruthroff-type balun is an impedance step-up balun whose balanced impedance is higher than that of the unbalanced one. For utilizing Ruthroff-type balun as a broadband and low-loss power combiner in CMOS power amplifiers, two new modified Ruthroff-type baluns with step-down impedance transformation, whose balanced impedance is lower than that of unbalanced one, were developed using IPD technology. Compared with 1:4 Ruthroff-type baluns which transfers the impedance from 50 Ω to 200 Ω, the proposed 1:1 and 9:4 baluns not only perform the impedance transformation from 50 Ω to 50 Ω and from 50 Ω to 22.2 Ω, respectively, but also have the center tap at the secondary winding of balanced ports. A power amplifier with a balun of having a center tap at the balanced winding can obviate the need of RF choke, which could improve the efficiency of power amplifier and reduce the chip area and cost. The proposed 1:1 balun exhibits an insertion loss of 0.46 dB with the 10-dB returned loss fractional bandwidths of 73.2%, and the proposed 9:4 balun exhibits an insertion loss of 0.75 dB with the 10-dB returned loss fractional bandwidths of 52.8%. To further verify the function of the proposed balun with a center tap, the testkeys of 1:1 and 9:4 baluns using a bypass capacitor and a DC block capacitor as ac ground were also developed using IPD technology. The measured results have good agreements with the simulations and show that the in-band performances of the balun with a center tap are close to those of the balun without additional capacitors. | en_US |