A solenoid layout technique is used to increase the magnetic coupling between the coils in multi-level spiral transformers. Using this technique, transformers with the following performance are measured: (a) magnetic coupling with coupling factor k>0.95 and insertion loss s21 better than 0.8dB at 5GHz; (b) self-resonant frequency Fres>15GHz with peak Q>10. The effect of high and low resistive substrates Is discussed with measured results. Using this structure, the size of the transformer can be reduced from 50 to 400%.

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Conference 2003 IEEE MTT-S International Microwave Symposium Digest
Fong, N. (Neric), Plouchart, J.-O. (Jean-Olivier), Zamdmer, N. (Noah), Kim, J. (Jonghae), Jenkins, K. (Keith), Plett, C, & Tarr, G. (Garry). (2003). High-performance and area-efficient stacked transformers for RF CMOS integrated circuits. Presented at the 2003 IEEE MTT-S International Microwave Symposium Digest.