Stepped-Frequency Image Reconstruction for Low-Cost High Resolution
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Solution Overview
Problem
Existing sensors using linearly swept sources face issues with range resolution degradation due to nonlinearity, requiring additional hardware for correction and being limited by high manufacturing costs for ideal swept sources, and struggle to increase bandwidth without proportionally increasing costs.
Innovation Solution
A sensor system employing a stepped frequency swept source with a modulator to increase bandwidth, reconstructing images by interfering the modulated stepped frequency waveform with an unmodulated stepped frequency waveform, and processing these signals to form a ptychographic super-resolution image without the need for ideal linear swept sources or additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linearly swept source is used for sensing, then range estimation can be achieved, but range resolution degrades when the swept source is not completely linearly modulated due to nonlinearity
Solution Approach 1:
The patent uses a reference signal that copies the transmitted frequency modulated signal to create a virtual reference branch. This reference signal is generated by delaying and processing a portion of the transmitted signal itself, eliminating the need for physical hardware copies while providing the necessary reference for nonlinearity correction in the range estimation process
Solution Approach 2:
The patent introduces a reference signal as an intermediary element that mediates between the transmitted signal and the received echo signal. This reference signal serves as a bridge to compare phases and correct nonlinearity effects without requiring direct access to the original transmitted waveform or additional hardware paths
2Measurement precision
If a dedicated reference path is added to correct nonlinearity, then nonlinearity correction can be achieved, but device complexity and hardware resources increase
Solution Approach 1:
Instead of creating a physical reference branch with dedicated hardware, the patent creates a virtual copy of the transmitted signal by delaying and processing a portion of it. This digital copying approach eliminates the need for additional physical reference paths while maintaining the functionality required for nonlinearity correction
Solution Approach 2:
The system uses its own transmitted signal to generate the reference signal needed for correction. By processing a delayed version of its own transmitted signal, the system becomes self-sufficient and does not require external or dedicated reference hardware, reducing overall device complexity
3Measurement precision
If high bandwidth swept source is used to increase resolution, then image resolution improves, but manufacturing cost increases significantly
Solution Approach 1:
The patent segments the frequency bandwidth into multiple smaller steps rather than using a single continuous high-bandwidth sweep. By dividing the total bandwidth into discrete frequency steps and processing each separately, the system achieves equivalent resolution using lower-cost, lower-bandwidth components for each segment
Solution Approach 2:
The patent transitions from a single-dimension continuous frequency sweep to a multi-dimensional approach combining discrete frequency steps with temporal processing. By adding the time dimension for sequential processing of multiple frequency steps, the system achieves high resolution without requiring expensive high-bandwidth hardware
4Adaptability or versatility
If stepped frequency swept source with modulator is used, then bandwidth can be increased without proportionally increasing cost, but signal processing complexity increases
Solution Approach 1:
The patent creates a reference signal by copying and delaying the transmitted stepped frequency signal. This reference copy is then used to simplify the processing of received echoes by providing a known reference waveform for correlation and phase comparison, reducing the complexity of analyzing the modulated stepped frequency returns
Solution Approach 2:
The system uses feedback from the transmitted signal itself to generate the reference waveform needed for processing. By feeding back a delayed version of the transmitted stepped frequency signal through the same modulation path, the system automatically compensates for system variations and simplifies the processing of received signals
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 allows for virtually arbitrary bandwidth increase without excessive cost, enabling high-resolution image reconstruction by combining low-resolution images from different step frequencies, overcoming the limitations of nonlinearity and cost associated with traditional sensors.
Implementation Method 1
a mixer to interfere the unmodulated stepped frequency waveform and the reflection of the modulated stepped frequency waveform to produce a beat signal
Data Source
AI summary
A system for a target image reconstruction includes a stepped frequency transmitter configured to emit a stepped frequency waveform having different constant frequencies at different periods of time and a modulator configured to modulate the stepped frequency waveform emitted at each period of time with a modulation signal to output a modulated stepped frequency waveform with an increased bandwidth. The system includes a transceiver configured to transmit the modulated stepped frequency waveform to a target and to accept reflection of the modulated stepped frequency waveform reflected from the target, a mixer to interfere the unmodulated stepped frequency waveform and the reflection of the modulated stepped frequency waveform to produce a beat signal of the interference of the unmodulated stepped frequency waveform with the reflection of the modulated stepped frequency waveform, and a signal processor to reconstruct an image of the target from the beat signal.