Coherent Combining software performs continuous removal of RF carrier phase differences from baseband data, allowing beamforming without grating lobes.
- Allows baseband summation without RF grating lobes.
Tolerates arbitrary, changing, and unknown physical placement.
- Source agnostic: Can combine dishes, phased arrays, dipoles, log periodic…
- Encoding agnostic: PSK, QAM, OFDM
- Accepts encrypted protocols without needing decryption
- Supports modems by preserving symbol shape, such as RRC.
- Accepts fractional samples per symbol – can be used without separate overhead of resampling or hardware pacing changes.
- Protocol agnostic: No training sequences are needed.
- Doppler Shift is preserved, enabling modem-based trajectory validation tools already in place.
In a phased array receiver system, strong, clear signals are created by adding together many weak, noisy signals. Due to angle of arrival, each weak signal’s antenna receives incoming RF carrier signals at a slightly different time than other antennas, resulting in a phase difference between its signal and the others. Adding these signals requires a phase shift to bring each weak signal into alignment before summation.
The phase shift is governed by the wavelength of the RF carrier frequency. Beyond a few wavelengths apart, summing phase shifted RF signals starts to show grating lobes – incoming angles where the phase shifts actually work destructively, destroying the resulting output. Even if the incoming signal is downconverted from RF carrier frequency to baseband data rate, the effect of the RF carrier phase is still present.
Grating lobes dominate phased array system design.
Until now. The Coherent Combining software operates on digitized baseband data, continuously removing the RF carrier phase differences, which then allows the baseband data to be combined coherently without RF grating lobes.
The Coherent Combining software product is fundamentally agnostic to the signal source. It can work with digitized signals from multiple parabolic dish antennas, phased array panels, log periodic directional antennas, or even a heterogeneous mix. The only requirements are that the signals must be sampled at the same rate with synchronized sampling clocks. These requirements can be met with hardware and/or software depending upon your approach to digitization. The combined signal can be streamed digitally to a modem, stored to file, or converted to analog RF via a SDR radio.
Any number of input signals can be combined (within the limits of the underlying computing platform of course). The combining process preserves Doppler shift, enabling existing trajectory and tracking software already present in modems. Combining does not use any protocol-specific information, making it compatible with PSK, QAM, OFDM, and others even if encrypted. No training symbols or QoS packets are required.
The Coherent Combining software has been successfully demonstrated under an Air Force phased array project with ATLAS Space Operations.
The Coherent Combining technology is available for applications in ground-to-space, space-to-space, and ground-to-ground.