The reflectarray antenna is a low-profile antenna inheriting the
advantages of both reflector antennas and phase arrays. Due to its simple feeding
system compared to normal arrays and low manufacturing cost compared to
reflector antennas, the reflectarray has numerous applications in space or
satellite communications and radars.
The goal of this project is to design an electrically-tunable beam-steering mirror coupled with an antenna for a microwave imaging system to replace conventional tomography system which has many drawbacks in engineering applications. This project produces a reflectarray antenna operating at two bands which is able to steer the reflected beam over a wide range of angle with simple circuitry.
The goal of this project is to design an electrically-tunable beam-steering mirror coupled with an antenna for a microwave imaging system to replace conventional tomography system which has many drawbacks in engineering applications. This project produces a reflectarray antenna operating at two bands which is able to steer the reflected beam over a wide range of angle with simple circuitry.
The radiation pattern of the reflectarray antenna is determined by the shifted phasing of each element to form a single focused beam or multiple beams. The phase-adjustable unit cell of the reflectarray was designed consisting of a square ring, a square patch, and a varactor diode placed across in between. By varying the capacitance of the varactor, the fabricated unit cell was able to produce a maximum of 352° in phase shift in F-band and noticeable shift in S-band.
A10 x10 Reflectarray antenna was fabricated with voltage control circuit and biasing network on the back side. Each column of the array is supplied with an individual voltage source. A combination of multiple voltages will produce a reflected beam at desired angle. The measurements were taken place on a reflective arch range with the transmitting antenna normal to the reflectarry antenna. The receiving antenna was then moved along the arch to measure the reflection from the target at different angles.
Different beam-steering angle can be achieved for different frequencies and with different combinations of the voltages. A maximum shift of 60° was achieved while maintaining a good reflection efficiency.