Beamforming is a traditional signal processing technique that uses multiple antennas to either maximize transmitted radio frequency (RF) energy to a certain point in space or to maximize the received RF energy from a certain direction. The performance and capabilities of a beamformer depend on the geometry of the antenna elements. Spacing these elements far apart increases the effective aperture of the antenna array, which improves spatial resolution, but if the antennas are placed too far apart then spatial ambiguities are introduced. Historical beamforming techniques are limited to antenna spacing less than the wavelength of the signal divided by 2 to avoid these ambiguities. Unfortunately, this limits the spatial resolution of the antenna array, and building larger arrays requires a large number of antennas.
Researchers at Arizona State University have developed single- or multi-stage distributed beamforming for distributed mosaic wireless networks. The single- or multi-stage beamforming dramatically increases the power delivery from a transmitter to a receiver using distributed relay networks or simple radios (mosaics). An aspect of this system is the computation and optimization of the filters at the mosaic(s). Filters are computed that effectively distribute the transmit energy for each channel in the optimal directions to maximize the energy that arrives at the receiving radio(s).
This technology offers several advantages over traditional beamforming techniques. For example, carrier phase ambiguities are resolved by precise distributed coherence, so the mosaic elements may be widely separated in space, thereby increasing the effective aperture of the synthetic arrays and improving the spatial resolution of the beamformer. The processing gain of this technique is higher than that of traditional techniques, so either more energy can be delivered to a receiver with the same transmit energy or the same amount of energy can be delivered to a receiver with less transmit energy. The system is more robust to external interference, which makes it more stable in increasingly congested spectral environments.
- Cellular communication systems
- Emergency response communication systems
- Covert communication systems
- Radio interferometry
- Positioning, navigation, and timing (PNT) systems
- Other radio frequency (RF) systems
Benefits and Advantages
- Increasing effective aperture by switching from fixed antenna arrays to flexible, distributed arrays
- Carrier phase ambiguities are resolved
- Improved spatial resolution
- Higher processing gain
- More robust to external interferences, thus more stable in congested spectral environments
- Provide better positioning performance for commercial aircraft, UAVs, and consumer transportation vehicles (e.g., cars, buses, etc.)