Linear FM Chirp Waveform for LADAR Transceiver
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Solution Overview
Problem
Existing LADAR systems require complex modulator designs and high bandwidth modulation signals to achieve high resolution, leading to increased size, weight, and power consumption, making it challenging to resolve small target features effectively.
Innovation Solution
A high bandwidth linear frequency modulated (FM) chirp waveform is generated using an array of laser sources with a predetermined optical frequency offset, reducing the modulation bandwidth requirements and eliminating the need for complex electronic modulators, by synchronizing a modulation signal with the timing sequence of the ladder signal produced by the laser array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex modulator designs are used to achieve high bandwidth and meet fidelity requirements, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system segments the high bandwidth requirement into multiple lower bandwidth laser sources operating at different optical frequencies. Each laser source generates a pulse at a specific frequency, and the combination of multiple frequency-offset pulses creates the equivalent of a high bandwidth signal without requiring a single complex high bandwidth modulator. This segmentation approach resolves the contradiction by achieving high measurement precision through multiple simple components rather than one complex component.
2Measurement precision
If high bandwidth modulation signals are used to achieve high resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system replaces the electronic modulation approach with an optical frequency division approach. Instead of using a complex electronic modulator to impose high bandwidth modulation on a single laser, the system uses multiple laser sources inherently operating at different optical frequencies. This substitution of the modulation mechanism eliminates the need for complex electronic modulation circuits while achieving the same high bandwidth effect through optical frequency multiplexing.
3Measurement precision
If complex modulator designs are used to achieve high bandwidth, then measurement precision is improved, but weight increases
Solution Approach 1:
The system divides the high bandwidth functionality into multiple independent laser sources, each contributing a portion of the total bandwidth. By segmenting the functionality across multiple simpler components rather than using one complex high bandwidth modulator, the overall system weight is reduced while maintaining the required measurement precision for resolving small target features.
4Measurement precision
If complex modulator designs are used to achieve high bandwidth, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The system replaces energy-intensive electronic modulation circuits with a passive optical frequency division approach. Multiple laser sources operate at different optical frequencies without requiring complex electronic modulators, thereby reducing power consumption while achieving the same high bandwidth effect. This substitution eliminates the need for high power electronic modulation while maintaining measurement precision.
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 high bandwidth linear FM chirp signals to be generated without the need for high bandwidth modulation signals or complex modulators, resulting in size, weight, and power savings while maintaining high resolution capabilities, enabling the LADAR system to resolve target features smaller than 1 cm.
Implementation Method 1
an array of laser sources configured to generate a series of pulses with each pulse offset in frequency by a respective frequency offset from a previous pulse and a subsequent pulse in the series of pulses
Implementation Method 2
modulating the ladder signal with a modulation signal having a modulation bandwidth corresponding to the frequency offset between each pulse in the series of pulses to generate a linear chirp signal
Data Source
AI summary
Methods and systems for generating a high bandwidth linear FM chirp for a laser detection and ranging (LADAR) transceiver is described herein. The LADAR transceiver includes an array of laser sources configured to generate a series of pulses with each pulse offset in frequency by a respective frequency offset from a previous pulse and a subsequent pulse in the series of pulses. A ladder signal can be generated from the series of pulses and modulated with a modulation signal having a modulation bandwidth corresponding to the frequency offset between each pulse to generate the linear chirp signal. The linear chirp signal can have a chirp bandwidth corresponding to the number of laser sources in an array and a modulation bandwidth of the modulation signal.