RF Ranging System Fine Time Adjustment
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Solution Overview
Problem
Current RF ranging systems face limitations in accuracy and complexity, particularly in achieving high-precision distance estimation between radios without the need for synchronized clocks, and are constrained by regulatory bandwidth limits and high system costs.
Innovation Solution
The implementation of an RF round-trip time-of-flight asynchronous direct-sequence spread spectrum (DSSS) system that calculates fine time adjustments by measuring peak errors in correlator outputs, allowing for sub-clock cycle time resolution and improved accuracy, while operating as an FCC unlicensed radio in flexible spectrum usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If highly accurate synchronized clocks are used to calculate propagation time, then measurement precision is improved, but device complexity increases due to the need for clock synchronization systems
Solution Approach 1:
The patent extracts and eliminates the clock synchronization requirement from the ranging system. By using a two-way time-of-flight measurement approach where the master radio transmits a signal and the remote radio returns it with a timestamp, the system calculates distance without needing synchronized clocks between devices
Solution Approach 2:
The patent introduces a timestamp as an intermediary carrier of time information. Instead of requiring synchronized clocks, the remote radio attaches its local timestamp to the returned signal, allowing the master radio to calculate propagation time by comparing its own clock with the timestamp from the remote radio
2Adaptability or versatility
If ultra-wideband systems operate within FCC regulations, then adaptability to regulatory requirements is improved, but measurement precision decreases due to limited range and bandwidth constraints
Solution Approach 1:
The patent implements dynamic frequency hopping across multiple channels during the ranging process. The system transmits on one frequency, receives the return signal on the same frequency, then hops to another frequency for the next measurement cycle, allowing compliance with FCC spectral density limits while accumulating precision through multiple measurements
Solution Approach 2:
The patent performs multiple partial measurements at different frequency channels and combines them to achieve the full measurement precision. Instead of requiring a single wideband measurement that would exceed regulatory limits, the system makes multiple narrowband measurements that collectively provide centimeter-level accuracy
3Length of stationary object
If continuous wave systems are used for long distance ranging, then measurement range is improved, but reliability decreases due to poor multipath performance and susceptibility to jamming
Solution Approach 1:
The patent uses periodic frequency hopping sequences where the system systematically cycles through multiple frequency channels in a predetermined pattern. This periodic frequency change makes the signal difficult to jam and provides inherent multipath resistance as different frequency components experience different fading conditions
Solution Approach 2:
The patent dynamically changes the frequency parameter during the ranging measurement process. By transmitting and receiving at multiple different frequencies rather than a single continuous frequency, the system overcomes multipath fading and jamming that affect specific frequency bands, thereby improving reliability
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
This approach enables precise distance estimation between radios with improved accuracy and range, reducing system complexity and cost, while maintaining compliance with regulatory requirements.
Implementation Method 1
RF ranging systems calculate the distance between two objects based in part on the time a radio signal propagates between those objects
Data Source
AI summary
Methods for estimating a distance between an originator and a transponder, methods for calculating a fine time adjustment in a radio, computer-readable storage media containing instructions to configure a processor to perform such methods, originators used in a system for estimating a distance to a transponder, and transponders used in a system for estimating a distance to an originator. The methods utilize fine time adjustments to achieve sub-clock cycle time resolution. The methods may utilize offset master clocks. The methods may utilize a round-trip full-duplex configuration or a round-trip half-duplex configuration. The method produces accurate estimates of the distance between two radios.