Conservatively Speaking [Microwave Bytes]

Are there any new ideas under the sun? We are all aware of those ideas that reappear, sometimes after several decades, as new and effective solutions to current problems. A good example of this is the Doherty power amplifier (DPA), which was first invented and reported by W.H. Doherty [1] in 1935 for the efficient amplification of amplitude-modulated (AM) radiofrequency (RF) signals. The original idea used vacuum tubes for the active devices. The DPA was rediscovered in the 1990s as an efficient and effective means of amplifying cellular wireless signals; this new implementation used LDMOS transistors. Nowadays, the DPA is virtually ubiquitous in cellular base stations.