Photonic Signal Generator for Phased Array Antenna Beam Steering
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Solution Overview
Problem
Phased array antennas face the squint phenomenon when using electronic phase shifters for broadband signals, leading to different frequencies aiming at different angles, which can be mitigated by employing true-time delays, but existing photonics-based solutions require separate RF signal generation and conversion, increasing complexity and cost.
Innovation Solution
A signal generator that directly generates RF signals from optical signals using a mode-locked laser, modulator, dispersion unit, and filters to introduce true-time delays, eliminating the need for separate RF signal generation and reducing conversion requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electronic phase shifters are used for broadband signals, then beam steering is achieved, but squint phenomenon occurs causing different frequencies to aim at different angles
Solution Approach 1:
The patent replaces electronic phase shifters with a photonic true-time delay system. Optical signals are used to carry RF signals through dispersive media (optical fibers with different dispersion values) to achieve frequency-independent time delays, eliminating the squint phenomenon while maintaining fast beam steering capability.
Solution Approach 2:
The system changes the delay parameter dynamically by selecting different optical paths with specific dispersion characteristics. By adjusting which optical fiber path is activated (with different dispersion values), the system achieves both time delay and frequency compensation, resolving the contradiction between steering speed and pointing accuracy.
2Measurement precision
If true-time delays are used to avoid squint, then beam pointing accuracy is improved, but system complexity increases due to separate RF signal generation and conversion requirements
Solution Approach 1:
The patent merges the RF signal generation function with the true-time delay function into a single photonic system. The optical signal directly carries the RF signal through the dispersive medium, eliminating the need for separate RF generation and multiple conversion stages, thus reducing system complexity while maintaining beam pointing accuracy.
Solution Approach 2:
The optical signal serves multiple functions simultaneously: it carries the RF signal, provides true-time delay through dispersion, and enables beam steering. This multi-functionality reduces the number of separate components needed, addressing the complexity issue while achieving accurate beam pointing.
3Measurement precision
If photonic true-time delay systems are implemented, then squint is avoided and beamforming accuracy is improved, but system weight and power consumption increase
Solution Approach 1:
The patent uses optical copies (light signals) to transmit and delay RF signals instead of using heavy electronic components for each delay channel. Optical fibers are lightweight compared to equivalent electronic delay lines, and the photonic system consumes less power while achieving the same beamforming accuracy.
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 flexible wideband multiple-signal beamforming with high phase stability, avoiding squint and reducing system complexity and cost, while providing electromagnetic interference immunity and low weight and power consumption.
Implementation Method 1
a laser light source, in the form of a mode-locked laser (MLL) 2. The mode-locked laser 2 is configured to generate a plurality of discrete wavelengths, corresponding to longitudinal modes of the laser
Implementation Method 2
At least one of the wavelengths of the mode-locked laser 2 is modulated with a modulator 4. The modulator 4 is an electro-optic modulator
Implementation Method 3
The dispersion unit 8 is configured to introduce chromatic dispersion to the modulated optical signals
Implementation Method 4
an optical heterodyning device 12 configured to heterodyne spectral components associated with different ones of the spaced wavelengths of the laser light source to generate a plurality of RF signals
Data Source
Figure 1
Figure 2a~2c
Figure 3~4
AI summary
A signal generator for a phased array antenna (18) comprises a laser light source (2) arranged to provide an optical spectrum comprising a plurality of spaced wavelengths (31). The signal generator further comprises a dispersion unit (8) arranged to introduce a delay to a plurality of spectral components (31, 32, 33) of the optical spectrum associated with the spaced wavelengths. The delay is dependent on the wavelength of the spectral components of the optical spectrum. The signal generator further comprises a heterodyning device (12) configured to generate a signal for the phased array antenna by heterodyning the spectral components associated with different ones of the spaced wavelengths of the laser light source (2).