Phased-array antenna (PAA) is a form of antenna system that has the ability to scan radiated radio frequency beams without mechanically moving the antenna structure. PAA systems offer higher reliability, improved signal-to-noise ratio, and lower transmission power.
Most PAA systems use electronic components to generate the phase shifts required for beam steering. Phase shifters are frequency dependent and inherently narrowband. All electronic PAAs are usually bulky, sensitive to electromagnetic interference and are expensive due to the installation of a large amount of electrical cables and radio frequency/microwave phase shifting devices.
There is a need for frequency independent beam steering of compact size, light weight, broad instantaneous bandwidth and better electromagnetic interference immunity performance. All these features could be realised by integrating optical/photonic system into the PAA system to realise frequency independent true-time delay (TTD) operation, which is crucial for the broadband beam forming.
At the Centre of Excellence in Microphotonic Systems, our researchers have demonstrated the principle of a TTD unit employing an Opto-VLSI processor, a broadband optical source using amplified spontaneous emission, and high dispersion fibres, which can be reconfigured to synthesise multiple arbitrary time delays.
This TTD unit has the capability to simultaneously generate multiple delay line taps for each antenna element and the flexibility to adjust the weight of each tap, making it attractive for broadband null-steering in phased array antennas.