The Doherty Power Amplifier: The Workhorse of Nowadays Wireless RF Infrastructure 23 de out. de 2012

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The Doherty Power Amplifier: The Workhorse of Nowadays Wireless RF Infrastructure

Although wireless communications’ infrastructures have always dealt with the fundamental trade-off between efficient energy usage and signal spectrum occupation, nowadays, this compromise has been taken to an extreme because signals band-guards have been reduced to a minimum while wireless operators are trying to reduce their power consumption costs. Unfortunately, signals confined in bandwidth exhibit very high peak-to-average power ratios and must be linearly amplified, which is detrimental to the average efficiency of conventional constant load and constant bias RF class-B or class-AB power amplifiers, PAs. Ideally, what any RF engineer would like to have was a PA that would change its load or its bias according to the input signal drive, this way staying in the linear regime, but always close to its peak efficiency. The talk will show how the Doherty PA configuration conceptually provides a dynamic-load modulation that is an astonishingly good approximation to this ideal scenario. However, it will also show why, in practice, this PA structure is much worse than expected, and so why we had to wait more than 50 years to turn it into the workhorse of modern wireless communications’ front-ends.

José C. Pedro
Professor, University of Aveiro