Efficiency and linearity analysis of a burst mode RF PA with direct filter connection

Abstract

Burst mode operation is proposed as an efficiency improving technique for power amplifiers. The core idea is to modulate the amplitude of the envelope signal into a series of square-wave pulses such that the width of the signal burst or the total amount of pulses are varied according to the envelope. The phase information is still contained by the timing of the pulses. This work presents the efficiency and linearity analysis of burst mode radio frequency (RF)/power amplifier (PA). In addition, the efficiency performance is compared when the burst mode RF power amplifiers (PA) is connected to a wideband load or a narrowband filter. It is shown that burst mode PAs are more efficient than the conventional Class B PAs. To achieve an even more favorable efficiency, a transmission line is inserted between the output of the switching RF PA and the filter to improve the filter's impedance characteristic. Additionally, the efficiency and linearity of the burst mode PA with and without transmission line has been studied and simulated thoroughly. To demonstrate the validity of the efficiency formulas and linearity considerations, a printed circuit board (PCB)-mounted burst mode PA using a laterally diffused metal oxide semiconductor (LDMOS) transistor was fabricated. Measurements show a peak efficiency of 78% and 28.8 dBm of output power.

Efficiency Enhancement Techniques for RF and MM-Wave Power Amplifiers

“…This out-of-band energy possibly violates spectral mask requirements of the wireless standard. Dissipating the out-of-band energy, reduces the efficiency and a similar efficiency-versus-output power curve as the square root behaviour in class B condition would be the result [33][34][35][36]. These extra requirements to improve efficiency, out-of-band impedance and the spectral mask requirements, result in an increase of the cost of the bandpass filter at the output.…”

“…Also coding can be helpful to reduce the generated out-ofband power. As proof of concept, this has been implemented in [31,33,[35][36][37][38].…”

“…A more detailed study on the trade-off between efficiency and the filter requirements in the burst mode power amplifier is presented in [39].…”

A fully digital delay-line based GHz-range multimode transmitter front-end in 65-nm CMOS

“…In order not to degrade efficiency too much, those bursts should be long enough [5], [10], [11]. As a rule of thumb, f c /f s should be at least 10 in any operating mode.…”

Radio frequency carrier amplitude‐burst transmitters – from architecture to circuit

“…So, in order to protect the SMPA, the researchers inserted an isolator, at the expense of a substantial degradation of the system power efficiency. This interaction between the SMPA and the BPF was studied in [13], where the researchers observed that by changing the length of the connection between these two blocks, the performance changed but, the proposed zero length connection is strongly restrictive. Staying with the initial configuration, the complete system was tested and measured in [14], where the obtained 43% of drain efficiency (and further dropping at lower input power values) is quite far from the theoretical expectations.…”