Wakeup Receiver Correlation Chains for Spread Spectrum Detection
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Solution Overview
Problem
Low power receivers face challenges in accurately detecting wakeup commands due to energy loss in spread spectrum signals, particularly with modulation schemes like OOK and FSK, leading to diminished detection capabilities.
Innovation Solution
A receiver splits incoming RF signals into multiple paths, delays, and multiplies them with delayed versions to auto-correlate symbols, using correlation chains to determine sub-sequence lengths without decoding, enabling efficient baseband conversion and accurate detection of wakeup codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If an envelope detector circuit is used to convert the incoming signal to baseband, then the receiver can avoid using local oscillators and conserve power, but half the energy or more of the incoming signal is spread to harmonics instead of being converted to baseband, leading to incorrect determination of wakeup commands
Solution Approach 1:
The incoming signal is divided into multiple components (in-phase and quadrature components) through complex correlation processing. This segmentation allows the receiver to process different aspects of the spread spectrum signal separately, preserving energy that would otherwise be lost to harmonics in a simple envelope detector.
Solution Approach 2:
A complex correlation processor acts as an intermediary between the incoming spread spectrum signal and the detection stage. This intermediary performs matched filtering with the expected wakeup code sequence, coherently combining signal energy and rejecting harmonic components, thereby resolving the energy loss problem while maintaining low power operation.
2Reliability
If spread spectrum modulation is used for wakeup signals, then the signal can be transmitted with robustness against interference, but the energy is spread to harmonics instead of being concentrated at baseband, diminishing detection capabilities
Solution Approach 1:
The system uses correlation feedback by comparing the received signal with the expected wakeup code sequence. The correlation processor continuously monitors the matched filter output and uses this feedback to determine whether a valid wakeup signal is present, maintaining detection accuracy despite the spread spectrum energy distribution.
Solution Approach 2:
The receiver changes the processing parameters by using complex correlation with specific delay values corresponding to the expected code length. This parameter adjustment allows the system to concentrate the spread spectrum energy at the correct temporal position, improving detection accuracy while preserving the robustness benefits of spread spectrum modulation.
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 method reduces power consumption and energy loss, allowing for more accurate detection of wakeup commands using modulation schemes like PSK and ASK, enhancing sensitivity and reducing harmonic energy spread.
Implementation Method 1
A receiver splits incoming RF signals into multiple paths, delays, and multiplies them with delayed versions to auto-correlate symbols
Data Source
AI summary
Methods, systems, and devices for a wakeup receiver operation is described. The apparatus may include a splitter that splits a received signal into a first component signal and a second component signal. The signal may include a code sequence, where each symbol of a plurality of symbols of the code sequences includes one of a set of sub-sequences. The apparatus may delay the first component signal and multiply the first component signal with the delayed first component signal and delay the second component signal and multiply the second component signal with the delayed second component signal to generate a first and second output. The apparatus may also determine a representation of the code sequence based on a sequence of levels of the first output and the second output over the plurality of symbols.