An enhanced lossy substrate model is developed with important features of broadband accuracy and scalability. The broadband accuracy is justified by a good match with open pad S-parameters measured up to 110 GHz and MOSFETs' S- and Y-parameters over 40 GHz. The proven model can accurately simulate four noise parameters (NFmin, Rn, Re(Yopt), and Im(Y opt)) and power spectral density of current noises (Sid and Sig). The scalability has been validated over nanoscale MOSFETs with different finger numbers and adopting various pad structures (lossy, normal, and small pads). This scalable lossy substrate model attributed to two substrate RLC networks under the pads and transmission lines (TMLs) can consistently predict the abnormally strong finger number dependence and nonlinear frequency dependence of noise figure NFmin) revealed in devices with lossy pads. The enhanced model is useful in guiding pad and TML layouts for effective reduction of extrinsic noises and low noise design. Using a normal pad structure, the NFmin can be effectively suppressed to approach the intrinsic performance, which is nearly independent of finger numbers.
|Number of pages||11|
|Journal||IEEE Transactions on Microwave Theory and Techniques|
|State||Published - 1 Feb 2009|
- Lossy substrate
- Nanoscale MOSFET
- RF noise