Multifunction RF Power Amplifiers for Space Applications

NASA envisions that data throughput and size, weight, and power consumption (SWaP) requirements levied on future space exploration vehicles due to resource constraints will necessitate that a different approach is taken for communications and radar. Rather than employing individual systems for short-range communications, long-range communications, and radar, respectively, a common architecture would need to be pursued that takes advantage of reconfigurable Software Defined Radio (SDR) and Digital Signal Processing (DSP) technologies in order to limit SWaP of the overall system. However, this sort of multi-function RF front end that NASA desires can only be realized if certain key performance parameters are met, the least of which is consistently high-power efficiency out of the RF power amplifier (PA).

With a common system for comms and radar, the RF front end, and consequently the RF PA, must support a variety of waveforms and signal characteristics. Constant-envelope waveforms, also commonly referred to as continuous wave (CW), allow for operation close to or at saturation of the RF PA. Conversely, complex, amplitude-modulated waveforms with varying degrees of peak-to-average power ratios (PAPR) require greater linearity (less distortion) that can only be achieved when the PA is “backed-off” from saturation.

NASA’s bands of interest for multifunction RF front ends are S-, X-, and Ka-bands. Given that bandwidth is in greater supply at the higher bands, a Ka-band PA module capable of supporting a variety of waveforms while operating at high power efficiencies would likely be most desirable. However, fewer Ka-band power amplifiers are on the market as compared to the other two frequency bands. At time of this writing, there were no identified commercial off-the-shelf solid-state amplifier modules that provided 20 watts of power across 29.5 to 32.5 GHz.

Figure 1: A concept for a Ka-band power amplifier module for a multifunction RF front end.

Figure 1: A concept for a Ka-band power amplifier module for a multifunction RF front end.

NASA’s space missions require the ability to transmit greater amounts of data, which lends itself to higher frequency bands, i.e., Ka-band, and much higher power efficiencies to limit the load on the on-board power system as well as the heat generated in a vacuum. Further, waveform flexibility is desirable, and as such, the power amplifier must be capable of operating both linearly and efficiently. Applications include supporting data communications with satellite, exploratory spacecraft, orbiter, and lander applications. This includes telemetry, tracking, and command (TT&C), deep-space data relay, etc. The Near-Earth Network (NEN), Deep Space Network (DSN) and Space Network (SN), including Tracking and Data Relay Satellite (TDRS), all benefit from advances in Ka-band technologies and its ability to deliver vast amounts of data through highly flexible communications architectures.

NuWaves completed a Phase I SBIR contract (NNX16CA36P) from 2016 topic S3.04, entitled High efficiencY PowER amplIfier for Over-the-horizon communicatioNs (HYPERION). NuWaves Engineering has developed a wide variety of off-the-shelf RF power 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 100 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 find out how our products can help to mitigate signal distortion in your digital communication systems.

 

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