Achieving both high linearity and high efficiency together in a Radio Frequency (RF) Power Amplifier (PA) system is challenging. Typical designs for highly efficient PAs (i.e., greater than 40% DC power efficiency) involve operating devices in their non-linear range, i.e., at or near compression (saturation). A PA operating in its nonlinear region inherently creates distortion to the RF signal, which results in message or bit errors that hinder overall system performance.
To achieve linear performance in a PA the most basic approach is to apply “back-off,” which means to reduce the input signal such that the PA output operates far below the 1 dB compression point (P1dB). The downside to this, however, is the more linear the operation the less efficient the PA is at transferring DC power to RF energy. A common technique to achieve linear performance at higher power efficiency levels is to insert a predistortion linearizer prior to the PA such that the back-off employed is to a lesser degree. Predistortion can be implemented in the digital or analog domains. Analog predistortion is generally more advantageous for a stand-alone PA module because it does not require digital access to the transmitter prior to conversion to the analog realm. However, analog predistortion linearizers are very limited in instantaneous bandwidth.
Another approach to improve both the efficiency and linearity of power amplifiers across multiple frequency bands while minimizing the size, weight, and power (SWaP) impact to the PA system is to implement a digital predistortion system. NuWaves recently undertook an effort to better apply this digital approach to a standard off the shelf power amplifier by partnering with a leading player in the field. A NuWaves 10-watt L and S band SSPA (NW-PA-12B01A) was utilized during the exploration effort. Data was collected both with and without the application of a digital predistortion topology for purposes of comparison. The results are promising, as the team realized a 20-dB improvement in the IMD3 performance while achieving substantial efficiency gains over a traditional “Back-off” approach. A standard LTE waveform with a PAPR of around 10 dB was utilized in the experiment. You can obtain more information about the investigation and possible applications for your system by contacting NuWaves today.
NuWaves Engineering has developed a wide variety of off-the-shelf RF amplifiers with rich features to support mission-critical CONOPS in telemetry, ISR, and tactical communication systems applications. Frequency ranges are available from UHF through C-band with output power levels ranging from 5 to 50 W. All NuPower PAs are designed, built and tested in-house under NuWaves’ Quality Management System (QMS) certified to AS9100:2016 and ISO 9001-2015 standards, which ensures that each product arrives on-time and defect-free. Most models are in-stock. NuWaves also boasts a full suite of state-of-the-art design and simulation tools, test and measurement equipment, prototyping equipment and a full-scale production facility to provide custom solutions to your specifications. Contact NuWaves today to extend the range of your communications systems and don’t forget to check out our RF Power Amplifiers