The present manuscript details a wideband high power amplifier design, based on a 5-mm GaN power bar. In particular, a broadband input large-signal matching condition has been realized, that ensures optimal power transfer under actual device operation. The measured performance of the PA perfectly matches the expected predictions based on large-signal measurements carried out on a 1.25-mm GaN elementary cell.
The importance of the bandpass reconstruction filter, BPF, in the proper operation of carrier-burst transmitters is widely accepted. However, it is often analyzed as if it could be considered isolated from the other system's components. To fill this gap, this paper presents a detailed study of the carrier-burst transmitter BPF, addressing both its most significant characteristics and its influence in the system. During this analysis, it was found that both the characteristics of the BPF and of the amplifier-BPF interconnection are extremely important to the correct behavior of the system. The proposed theoretically driven design rules are verified by several simulations and supported by corresponding laboratory measurements.
A technique to accurately measure modulated wideband signals in a two-port context is presented. The technique uses a four channel high frequency digital sampling oscilloscope to perform in-situ correction of both amplitude and phase of the modulated stimulus signal. An advantage of the proposed technique is that no assumption about the group delay has to be made. The technique is demonstrated in a source-pull system. The results clearly demonstrate the necessity of using error-correction in tuner based setups due to the large variations in group-delay over the measurement bandwidth.
A combined approach to digital predistortion (DPD) and crest factor reduction (CFR) is proposed. The new CFR is structured similar to DPD and is implemented by introducing a steady-state offset into the DPD coefficients. The DPD and CFR coefficients are estimated using separate adaptive processes but applied to the transmission path in a common module. Results show that CFR lowers the PAPR of the predistorted signal by 5 dB, which reduces the stress on the peaking transistor in a Doherty PA.
Device technology is becoming quite mature and repeatable, but nevertheless, for various reasons, there are statistical variations in device parameters. These process variations will influence the accuracy of the designs and yield in production. The implementation of these variations in Large Signal Models is discussed in the paper.
