Transceiver CFO Compensation via Multi-Carrier Phase Difference
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Solution Overview
Problem
Existing distance measurement techniques between transceivers are inaccurate in the presence of carrier frequency offset (CFO), particularly in Bluetooth Low Energy (BLE) and IoT applications, due to sensitivity to multipath fading and environmental influences.
Innovation Solution
A transceiver circuit that includes a controller configured to estimate CFO and generate I/Q measurement data across multiple frequencies, allowing for accurate distance estimation by compensating for CFO errors and mitigating phase incoherency issues through Two-Way Multi-Carrier Phase Difference (TWMCPD) methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-based ranging techniques are used to determine distances between transceivers, then distance measurement capability is provided, but measurement accuracy deteriorates in the presence of carrier frequency offset (CFO)
Solution Approach 1:
The patent changes the parameter of frequency by performing measurements at multiple discrete frequencies across the band of interest. By measuring phase differences at multiple frequencies and combining these measurements, the system achieves accurate distance estimation that is resilient to carrier frequency offset, transforming a single-frequency vulnerable measurement into a multi-frequency robust measurement process
Solution Approach 2:
The patent introduces an intermediary processing step that measures and estimates the carrier frequency offset (CFO) between transceivers. This CFO estimate acts as a mediator that compensates for frequency mismatches before distance calculation, allowing the system to maintain measurement accuracy despite frequency offsets caused by crystal tolerances and environmental factors
2Device complexity
If single-frequency phase measurement is performed, then measurement process is simple, but measurement accuracy deteriorates due to multipath fading and environmental influences
Solution Approach 1:
The patent segments the measurement process into multiple discrete frequency points across the available bandwidth. Instead of performing a single phase measurement, the system divides the frequency band into multiple measurement points, collecting phase difference data at each point. This segmentation allows the system to overcome multipath fading effects that affect single-frequency measurements, as different frequencies experience different fading conditions
Solution Approach 2:
The patent implements periodic frequency hopping across the band of interest, systematically cycling through multiple discrete frequencies in a predetermined sequence. This periodic action at different frequencies allows the system to collect diverse phase measurements that can be combined to achieve accurate distance estimation while being resilient to time-varying environmental conditions and multipath effects
Data Source
AI summary
A transceiver circuit is disclosed. The transceiver circuit includes an antenna, a receiver RF chain configured to receive a receiver RF signal from the antenna, a transmitter RF chain configured to transmit a transmitter RF signal to the antenna, and a controller configured to access a CFO (carrier frequency offset) estimate, and to, for each of one or more working frequencies: cause the receiver RF chain to receive a receiver RF signal from the antenna at each working frequency, generate I/Q measurement data based at least in part on the received receiver RF signal and the CFO estimate, store the I/Q measurement data, and cause the transmitter RF chain to transmit a transmitter RF signal to the antenna at each working frequency, where the controller is further configured to cause the transmitter RF chain to transmit the I/Q measurement data for each working frequency to the antenna.