A 50MHz bandwidth multi-mode PA supply modulator for GSM, EDGE and UMTS application

Abstract

-This paper describes the design and measurement results of a supply modulator for a PA for GSM, EDGE and UMTS application. The modulator combines a high-bandwidth class-AB linear regulator with an efficient DC/DC converter in a master-slave configuration. The DC/DC converter is currentmode controlled and has been designed to operate at switching frequencies between 1MHz and 25MHz. A damped dualinductor LCR filter has been inserted in the output branch of the DC/DC converter for ripple suppression. The chip has been fabricated in a 0.25µm CMOS process with an additional gate oxide for 6V transistors and has an active area of 1.5mm 2 . It achieves a bandwidth of 50MHz (for UMTS) with a peak output power of 3.2W (for GSM) and output rms ripple of less than 4mV.

An overview of fast DC-DC converters for envelope amplifier in RF transmitters

“…A similar power stage is used in [13][14] but the switched converter is current controlled by means of a hysteretic loop with variable frequency switching in the MHz range. In [13], the contribution to the bandwidth provided by this stage is 200kHz, and the linear part provides up to 50MHz.…”

“…In [13], the contribution to the bandwidth provided by this stage is 200kHz, and the linear part provides up to 50MHz. A deep optimization of the envelope amplifier is carried out in [ 14].…”

“…Including a parallel linear regulator (group A.2) makes easier to achieve a high bandwidth ( [13] [14]). The solution that presents a good trade-off between power and bandwidth is the one based on the multilevel with series regulator [17] (group C).…”

Survey of architectures and optimizations for wide bandwidth envelope amplifier

“…When it is necessary to obtain wide bandwidth of the envelope amplifier, it is very common to use a hybrid solution based on a buck converter in parallel with a linear regulator [13][14][15][16]. The idea is based on the fact that the major part of the envelope energy lies in the low frequency part of the spectrum, while the high frequency part, which defines the bandwidth of the EA, is practically negligible from the point of view of the envelope's energy.…”

Comparison of two different cell topologies for a multilevel power supply to achieve high efficiency envelope amplifier

“…These solutions do not exceed the bandwidth of few hundred kHz and the output power is from the range of mW up to several tens of watts [11]. In [12], [13] a buck converter is integrated and the switching frequency is in the range of several MHz, but with small output power, in the range of mW. A possible implementation for the envelope amplifier would be a dc-dc converter, as it is necessary a high efficiency for the solution.…”