Common-mode termination requirements in concurrent dual-band push-pull power amplifiers

Fourier Analysis of Signal Waveforms in An Ideal Concurrent Dual-Band Class-D Power Amplifier

“…Furthermore, Fig. 4 shows the degradation of drain efficiency as the termination impedance of ( ) C V t is lowered, which aligns with the empirical observation of [8].…”

“…The developed theory is then used to derive the 100% ideal drain efficiency of such a configuration. We further demonstrate the utility of the analysis by analytically investigating the deterioration of the PA's efficiency under nonideal common-mode termination conditions [8]. Finally, we validate our theory using Harmonic Balance simulation.…”

“…In Fig. 3, the magnitude of these coefficients, obtained analytically, is plotted using red lines, illustrating large IM2 components, as envisaged in [8]. Furthermore, Fig.…”

“…To further establish the usefulness of the above analysis, we validate it against results obtained from [8]. The authors of [8], using largely numerical and empirical methods, claimed that the common mode voltage ( C V in the current paper) of a concurrent dual-band class-D PA has large second order intermodulation (IM2) components and showed that terminating these components with high impedances (which implicitly holds true for an ideal transformer balun but not necessarily for even an ideal distributed balun) is mandatory for achieving high efficiency. Here, we use (33) to analytically…”

“…Chief among these problems are a reduced efficiency and output power when compared to their singleband counterparts [7]. Taking a page out of the book of singleband PA designs, researchers have recently demonstrated a switch-mode class-D configuration to obtain high efficiency out of a dual-band PA [4,8].…”