Simo Hietakangas

Learn More
An efficiency enhanced power amplifier is presented. The amplifier uses envelope tracking (ET) technique and static predistortion to achieve high linearity. The effects of drain voltage modulation to experimental amplifier's gain, phase as well as bandwidth are measured using simple single-tone tests and discussed. Then the amplifier's ET performance is(More)
The purpose of this work is to study feedthrough cancellation methods available for a class E amplified polar transmitter. A mathematical feedthrough cancellation using measured S-parameters is presented. The results show a clear improvement to the nonlinear behaviour of a class E amplifier. Also, a transistor level possibility of feedthrough cancellation(More)
AM-PM distortion causes spectral regrowth in RF transmitters with modulated signals. One reason for AM-PM is the fact that signal-dependent transistor input capacitance pulls the frequency response of the input matching network and causes phase shift already at the input of the transistor. This paper studies the Miller capacitance effect in most common(More)
This paper discusses the effects of unequal signal delays in the input network of a multi-finger transistor in a switching RF power amplifier. In a design that employs a distributed transistor, the driving signal must be delivered to each transistor finger by conductor segments that usually are unequal in length. The effects of the consequent(More)
This paper studies the effect of feedback capacitance on the input matching of a class E switching power amplifier. The on/off switching causes the input to see the feedback capacitance either amplified by the Miller effect or not and therefore, this feature is dependent on the gain of the amplifier. The time-varying feedback appears at the gate as negative(More)
This work demonstrates a new integrated inverse class E amplifier circuit, employing a pHEMT switching device and fully integrated output network for pulse shaping. The circuit is particularly suitable for full integration, since it does not need any RF choke for biasing, and no DC blocking capacitor is needed between the switch and the output network(More)
  • 1