Active Reflector RF Ranging System Phase Coherence
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Solution Overview
Problem
Existing radio frequency distance measuring systems require simultaneous transmission and reception on two different frequencies, leading to inefficient bandwidth usage and susceptibility to noise, with clock synchronization issues causing range errors.
Innovation Solution
A high-resolution active reflector radio frequency ranging system that enables discontinuous transmissions on multiple frequencies, using thermally-insulated reference oscillators and delta sigma phase lock loops for precise phase and frequency coherence between master and slave units, allowing for frequency hopping and vernier measurements to optimize bandwidth and eliminate multipath data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If simultaneous transmission and reception on two different frequencies is used, then distance measurement can be achieved, but bandwidth utilization becomes inefficient and noise interference increases
Solution Approach 1:
The patent implements periodic transmission bursts at a single frequency rather than continuous simultaneous transmission on two frequencies. The master unit transmits periodic signal bursts to the slave unit, which responds with periodic acknowledgment bursts, allowing distance measurement through time-of-flight calculation while using bandwidth efficiently through time-division rather than frequency-division multiplexing.
Solution Approach 2:
The single frequency channel serves multiple functions: master transmission, slave acknowledgment, and distance measurement all occur on the same frequency at different time intervals. This eliminates the need for separate frequency channels for each function, improving bandwidth utilization while maintaining measurement precision.
2Measurement precision
If clock synchronization is maintained between master and slave units, then accurate range calculation is achieved, but system complexity increases due to synchronization requirements
Solution Approach 1:
The slave unit measures the time interval between receiving the master's transmission burst and sending its acknowledgment burst, then feeds back this timing information to the master unit. The master unit uses this feedback to calculate the round-trip time and determine distance, eliminating the need for complex bidirectional clock synchronization while maintaining measurement accuracy through precise timing measurement and feedback.
3Quantity of substance
If frequency hopping is implemented, then bandwidth optimization and multipath elimination are achieved, but system complexity increases
Solution Approach 1:
The system dynamically switches between different frequency channels based on transmission needs and environmental conditions. The master and slave units can hop to different frequencies for different transmission bursts, optimizing bandwidth utilization and avoiding multipath interference on specific frequencies, while the dynamic nature allows adaptation without requiring overly complex predetermined frequency assignment systems.
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
The system achieves precise distance measurements with minimal bandwidth utilization, reducing range errors and multipath interference, while maintaining phase coherence and power efficiency.
Implementation Method 1
thermally-insulated reference oscillators
Implementation Method 2
delta sigma phase lock loops for precise phase and frequency coherence
Implementation Method 3
phase measurements on radio frequency signals transmitted between two points in space
Data Source
AI summary
A radio frequency ranging system is grounded in establishing and maintaining phase and frequency coherency of signals received by a slave unit from a master unit and retransmitted to the master unit by the slave unit. For a preferred embodiment of the invention, coherency is established through the use of a delta-sigma phase-lock loop, and maintained through the use, on both master and slave units, of thermally-insulated reference oscillators, which are highly stable over the short periods of time during which communications occur. A phase relationship counter is employed to keep track of the fractional time frames of the phase-lock loop as a function of the reference oscillator, thereby providing absolute phase information for an incoming burst on any channel, thereby enabling the system to almost instantaneously establish or reestablish the phase relationship of the local oscillator so that it synchronized with the reference oscillator.