When the shape and direction of the radiation field pattern are dependent on the relative phase and amplitudes of the currents present in the individual antenna elements in the array, then such array antennas are called phased array antennas.
Phased array antennas are the best candidates for wireless communication applications, as they provide electronic steering for varying the direction of the beam.
Features such as shaped antenna patterns, dynamic range, beam control, high gain, high directivity, in-band linearity, adaptive interference cancellation, and angle-measurement accuracy make phased array antennas suitable for radar applications.
Phased array antennas are often used in radar systems
Phased array antenna applications are growing in popularity due to advantages such as cost, size, weight, and manufacturability. The limitations of single-element antennas, such as electromagnetic issues of polarization, difficulty in amplitude and phase control, and reliability problems, have driven the popularity of phased array antenna technology. Developments in the field of automation have made the production of phased array antennas easier, and the automated assembly of radiators is one of the reasons that encouraged the use of phased array antennas in mobile communication systems and radar systems. In this article, we will discuss array antennas and their beam control methods as well as phased array antennas and their applications.
To meet the demands of long-distance communication, it is important to design antennas with excellent directive characteristics and high gain. In-single element antennas, the radiation pattern is relatively wide and gives a low value of directivity. Enlarging the dimensions of a single element antenna is one method to accomplish more directive characteristics. However, increasing the electrical size of the antenna may be a limitation in certain applications.
Another solution for enhancing directivity characteristics is to form an assembly of radiating elements, or radiators, in an electrical and geometrical configuration. The multiple radiating elements form an array and are collectively called array antennas.
In array antennas, wires and apertures are used as individual elements of the array. Usually, the radiating elements are identical, and this makes antenna manufacturing simple, practical, and convenient. The total field of the array antenna is given by the vector sum of the fields radiated by the individual antenna elements.
It is important to make the radiation field patterns of the individual elements interfere constructively in the preferred direction and destructively in the remaining directions. There are five main ways to control the overall radiation pattern of array antennas, and they are described in the upcoming section.
Controlling Array Antenna Patterns
The controls that are used to shape the overall radiation field pattern of array antennas are:
- Geometrical configuration of the antenna array - The geometrical configuration can be linear, spherical, circular, or rectangular, depending on the application.
- Excitation phase of individual antenna elements - By varying the phase excitations of the individual array element or changing the frequency of operation, the radiation beams of the required shape can be achieved. This control method requires phase shifters or frequency sweeping.
- Excitation amplitude of individual antenna elements - By varying amplitudes of the individual array element excitations, the required radiation pattern can be achieved. This method alleviates the need for phase shifters and frequency variation.
- Relative displacement between the individual array elements - Individual antenna element separation and orientation influence the radiation characteristics of array antennas.
- Relative pattern of the individual antenna elements - The relative pattern of the array elements influences beamforming because the overall radiation pattern of the array antenna is the vectorial sum of field patterns of individual antenna elements.
Phased Array Antennas
By utilizing the above-mentioned five control methods, the radiation pattern of array antennas can be varied. When the shape and direction of the radiation field patterns are dependent on the relative phase and amplitudes of the currents present in the individual antenna elements in the array, then such array antennas are called phased array antennas.
Phased array antennas overcome the issues in speed and reliability that mechanically steered antennas face. With the aid of electronic beamforming, the size, weight, and power (sWaP) of phased array antennas are greatly reduced compared to mechanically steered antennas. Phased array antennas are used in fields such as defense, communication, and space technology.
Phased Array Antenna Applications
Phased array antenna applications are not limited to broadcasting, satellite communication, optics, weather research, and human-machine interfaces. We will discuss a few other applications of phased array antennas in this next section.
Wireless communication systems require antennas that are able to change the direction of the main beam lobe over time. Phased array antennas are the best candidates for wireless communication applications, as they provide electronic steering for varying the direction of the beam. Phased array antennas produce the minimum sidelobe levels and narrow beamwidths, which increase the effectiveness of the antenna. Cellular and WLAN communication systems make use of phased array antennas in their smart base stations.
The future of communication-5G technology utilizes other technologies such as massive multiple-input multiple-output (MIMO), multiple beams, multiple accesses, and ultra-dense networking to enhance system performance. The antenna systems for 5G applications should be capable of creating multiple independent beams, high gain, and wide azimuthal coverage. Multibeam phased array antennas meet the requirements of 5G technology.
Features such as shaped antenna patterns, dynamic range, beam control, high gain, high directivity, in-band linearity, adaptive interference cancellation, and angle-measurement accuracy make phased array antennas suitable for radar applications. Phased array antennas are often used in synthetic imaging radars and automotive radars used for traffic control and collision avoidance.
Mechanically steered phased array antenna applications are also seen in RF-power harvesting systems. Instead of electronic steering, beam steering is achieved by mechanically shifting the feeding point, thereby maximizing the power delivered into the harvesting circuit. If you are interested, Cadence offers software for phased-array antenna design for beam steering applications.