SDR Waveform Timing Calibration for Deterministic Synchronization
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Solution Overview
Problem
Conventional PNT systems exhibit non-deterministic radio frequency characteristics, are susceptible to disruption, and lack encryption, making them vulnerable to jamming and spoofing, especially in GPS-denied environments.
Innovation Solution
The system employs a method and architecture for waveform synthesis that includes transmitting a stimulus signal to a software-defined radio (SDR), determining its delay state, and generating a calibrated signal to adjust time with sub-nanosecond accuracy, thereby controlling RF characteristics and characterizing signal delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PNT systems are used, then basic positioning and timing functions are provided, but RF characteristics are non-deterministic and synchronization accuracy deteriorates
Solution Approach 1:
The system performs preliminary calibration by transmitting test signals through the SDR at different delay states before actual operation. The calibration process pre-determines the relationship between delay states and actual signal delays, storing this mapping for later use. This preliminary action eliminates the need for real-time delay measurement during operation, ensuring deterministic RF characteristics and high synchronization accuracy.
Solution Approach 2:
The system changes the delay state parameter of the SDR to different predetermined values and measures the corresponding actual delay for each state. By establishing a mapping between delay state parameters and actual delays, the system can select appropriate delay states to achieve desired timing characteristics, thereby improving synchronization accuracy and RF determinism.
2Reliability
If GPS-based PNT systems are used, then positioning and timing are provided, but the systems are susceptible to jamming, spoofing, and on-orbit attacks
Solution Approach 1:
The system generates its own calibrated timing signals independently using the SDR with determined delay states, rather than relying on external GPS signals. This self-service capability allows the system to provide accurate timing and positioning functions in GPS-denied environments while maintaining immunity to jamming and spoofing attacks, thereby improving reliability and adaptability simultaneously.
3Measurement precision
If SDR delay states are not calibrated, then the system is simpler to operate, but time synchronization accuracy deteriorates
Solution Approach 1:
The calibration process is performed as a preliminary one-time action before normal operation. During calibration, the system transmits test signals at different delay states and stores the relationship between delay states and actual delays. Once calibrated, the system can quickly select appropriate delay states without repeated complex measurements, achieving high synchronization accuracy while keeping operational complexity low.
Data Source
AI summary
The present application at least describes a method for waveform synthesis. The method may include a step of transmitting a stimulus signal to a software defined radio (SDR) operating in a first state. The method may also include a step of receiving, via the SDR, an output signal based upon the transmitted stimulus signal. The method may also include a step of. determining, based upon the received output signal, a delay state of the SDR from a plurality of predetermined delay states of the SDR. The delay state may be associated with a parameter of the SDR. The parameter may include any one or more of a receive frequency, transmit frequency or bandwidth. The method may further include a step of generating a calibrated signal based upon the determined delay state. The method may even further include a step of sending the calibrated signal to the SDR to adjust a time.