Multi-Antenna Coherent Transmission With Phase and Delay Alignment
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Solution Overview
Problem
Coherent combining of RF signals transmitted via independent antennas separated by a distance significantly larger than the wavelength, with unknown exact locations, is challenging due to the difficulty in setting phase to achieve constructive interference, especially in satellite communication systems with relative motion.
Innovation Solution
A method involving synchronization transmissions and phase adjustments using delay elements and phase shifters to align the phases and timings of signals transmitted from multiple antennas, allowing constructive interference at the satellite, even with unknown antenna locations and relative motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple independent antennas are used for transmission, then transmission reliability and data rate can be improved through coherent combining, but the complexity of achieving coherent constructive interference increases significantly due to unknown antenna locations and relative motion
Solution Approach 1:
The patent applies preliminary action by performing synchronization transmissions before main data transmission. The terminal first transmits synchronization signals via multiple antennas, allowing the network device to estimate channel states and calculate phase differences in advance. This preliminary phase estimation enables the terminal to pre-adjust phase shifters and delay elements, establishing coherent combining conditions before actual data transmission begins, thus resolving the complexity of real-time phase alignment.
Solution Approach 2:
The patent implements feedback mechanisms where the network device receives synchronization transmissions, estimates channel states, and provides feedback information about phase differences and timing offsets to the terminal. The terminal uses this feedback to adjust its phase shifters and delay elements, creating a closed-loop control system that continuously maintains coherent combining conditions despite relative motion between terminal and satellite, thereby improving reliability without requiring complex open-loop phase control.
2Adaptability or versatility
If antennas are separated by a distance significantly larger than the wavelength, then spatial diversity and handover capability are improved, but the precision required for phase setting increases to maintain constructive interference
Solution Approach 1:
The patent introduces intermediary elements - specifically phase shifters and delay elements - that act as adjustable intermediaries between the antennas and the transmission medium. These intermediaries allow dynamic adjustment of phase and timing without requiring precise fixed antenna positioning. The phase shifters provide continuous phase adjustment capability, while delay elements compensate for timing differences, effectively decoupling the handover capability from strict positioning requirements and reducing the measurement precision burden.
Solution Approach 2:
The patent applies dynamics by making the phase and timing parameters adjustable rather than fixed. Phase shifters and delay elements are dynamically controlled based on real-time channel conditions and satellite position changes. This dynamic adjustment capability allows the system to maintain coherent combining despite the large antenna separation and relative motion, converting a static positioning problem into a dynamic control problem that is easier to solve with appropriate actuators.
3Reliability
If phase shifters and delay elements are used for coherent combining, then signal-to-noise ratio can be improved by 6 dB, but the device complexity and cost increase
Solution Approach 1:
The patent segments the phase and timing control functions into separate components - phase shifters handle phase alignment while delay elements handle timing synchronization. This segmentation allows each component to be optimized independently and simplifies the overall control architecture. By dividing the coherent combining function into modular segments, the system achieves 6 dB SNR improvement through coordinated operation of simpler, specialized components rather than requiring a single complex device.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves a combined signal-to-noise ratio (SNR) about 6 dB higher than individual transmissions, enabling increased data rates and reliable communication.
Implementation Method 1
the multiple transmissions may form a coherent constructive interference (coherent combining), or an approximately coherent constructive interference, at the target satellite
Data Source
AI summary
In satellite communication systems, the cost of a terminal often corresponds to a maximum data rate that the terminal is required to transmit towards a satellite. The higher the data rate, the higher the Effective Isotropic Radiated Power (EIRP) the terminal may be required to radiate. The EIRP of the terminal is directly proportionate to the transmission power and to the effective area of the antenna. Using coherent transmission combining may facilitate a similar EIRP while reducing the cost of the terminal through using smaller antennas and lower radiated power. Methods, apparatuses, systems, and computer readable media are described herein for facilitating coherent combining of transmissions.