Optically controlled microwave beamformer

Abstract

Optically controlled microwave beam forming networks comprise 2N single frequency DFB lasers of different wavelengths, , 2N electro-optic intensity modulators, 2N *1 passive wavelength division multiplexers, an optical fiber, 1*2N optical beam splitter, 2N fiber collimator, a time delay network module, 2N coupled lenses, 2N photoelectric detectors and 2N low noise amplifiers, wherein N is an integer larger than 2. The optically controlled microwave beam forming networks have the advantages of the high signal to noise ratio, good dynamic performance, high time delay precision, continuous adjustability, and good stability, and are easy to be extended in the system array size.

Description

technical field [0001] The invention relates to a broadband optically controlled phased array radar, in particular to an optically controlled microwave beamformer. Background technique [0002] The beamformer (BFN-Beam Forming Networks) is the core of phased array radar and smart antenna. It controls the phase difference or true delay difference of each microwave link in the array to make the radiation field of each microwave radiation source in the far field The specific direction of the interference is extremely large, and the purpose of energy directional emission (or reception) is achieved. Change the phase difference or true delay difference between microwave links to control the direction of the beam. [0003] Beamforming, essentially processing multi-element reception (transmission) to obtain a specific pattern, is the premise and basis for good tactics and performance of modern radar and electronic countermeasure equipment. [0004] The Optically Controlled Microwa...

AI Technical Summary

Problems solved by technology

[0005] Traditional beamforming networks using phase shifters have beam tilt effects [see literature [1]MichaelY.Frankel and Ronald D.Esman,True Time-Delay Fiber-optic Control of anultrawideband Array Transmitted Receiver with Multibeam Capability]. The noise figure of the optical multi-beamformer of the spectrum light source is more than 30dB higher than that of the external modulation link using a single-frequency light source, which seriously affects the signal-to-noise ratio of the system and limits the dynamic range of the system. It is not suitable for the transmission of vector signals, etc. For occasions with higher requirements (see literature [2] Reconfigurable Optical Beamformer for Simplified Time SteeredArrays, US2002 / 0181874A1, Dec.5, 2002), so this system uses a single-frequency light source, and the signal modulation method adopts an external modulation method; the available beam The delay network part of the former mostly adopts the dispersion characteristics of the medium (see [3] Photonic dual RF beam reception of an X band phased array antenna using aphotonic crystal fiber-based true-time-delay beamformer, Harish subbaraman, Applied Optics , 47,6448,2008) and the time delay generated by the optical switch (see literature [2]Reconfigurable Optical Beamformer for Simplified Time Steered Arrays, US2002 / 0181874A1,Dec.5,2002; literature [4]Optical beam former for high frequency antenna arrays), For time-delay networks using dispersion characteristics, there are disadvantages such as difficult to effectively and quickly control beam scanning, slow beam scanning speed, slow response speed, low delay accuracy, poor real-time performance, and poor operability; For a 4x4 optical beamformer, the number of optical switches required is 16 to generate different delays, and the delay cannot be continuously adjusted. Using optical switches to form a delay array will result in high cost and complicated control structure. It can realize the scanning of some beams, and the practical value is not high;

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