The harmonic injection technique for short-wave HF power amplifier

This paper proposes a technique for reducing the level of harmonic distortions in the short-wave HF power amplifier. This technique is based on the introduction of injection channels in the HF path to compensate harmonic distortions in full range of output frequencies. The algorithm and system for generating signals for the injection channels, as well as architecture implementing the proposed technique are proposed. Positive results are presented using the proposed technique for reducing the level of harmonics in the short wavelength of the HF power amplifier.

I. Introduction

Nonlinearity distortions in power amplifier are presented not only in the form of intermodulation products in the baseband, but also in the form of higher order harmonic distortions in the output spectrum. At this time, even if the input to the nonlinear power amplifier receives a signal with a constant envelope, the output spectrum of such a power amplifier will include the frequency of carrier wave and many frequencies of harmonic distortions. In the short-wave range, this leads to the fact that during operation of several radio transmitters, even at a considerable spatial distance, harmonics of one radio transmitting device may fall within the operating frequency band of another radio transmission device, that causes interference on the receiving side of communication channel and accordingly be an invalid signal receiving. In order to avoid the interference of the radio transmitting devices special subrange harmonic tunable filters [1], located at the output HF path in radio transmitters are used. The harmonic filters reduce the level of harmonic distortions in the output spectrum of the radio transmitting devices, but have a few number of significant disadvantages: high cost, high complexity, hard implementation, great time hopping between the bands.