www.radartutorial.eu www.radartutorial.eu Radar Basics

Cylindrical Phased Array

Figure 1: Basic design of a cylindrical phased array antenna

Figure 1: Basic design of a cylindrical phased array antenna

Cylindrical Phased Array

A cylindrical phased array (CPA) consists of a flat phased array wrapped around a vertical cylinder. It can be used for radar applications and typically has an element-to-element spacing of nearly half the wavelength, like planar phased array antennas.

For a two-dimensional scanning radar, all the lying upon each other antenna elements are combined into a group with mutually constant phase relationships. This can also be a constellation, for example, as used in a Large Vertical Aperture, to generate an approximate cosecant squared pattern vertically.

To rotate the antenna radiation pattern in the horizontal plane, only those vertical antenna groups that are within a sector of 90° are excited. The circular curvature of the active antenna array is electronically compensated by phase shifters so that the radiation is the same as with a flat-distributed phased array antenna. A swivel to the right is achieved by switching off the vertical group on the far left and switching on an additional group on the far right. This sector is thus electronically shifted in a circle so that the radiation is the same as with a mechanically rotating antenna.

If suitable radiators are used, this type of antenna can also be used as circular polarimetric phased array (CPPA) antenna.

The radiation pattern for CPPAR with radius of r and N elements located on a circumference of a cylinder at n = nΔφ,Zm) can be simply calculated as:

(1)

  • N = is the number of elements in H-plane;
  • M = is the number of elements in E-plane;
  • A(n,m) = amplitude excitation of the nmth element;
  • Fn,m(θ,φ) = active element pattern
  • φn, zm the location of nmth element on the cylindrical coordinate system.

Also, the element patterns of CPAR are dependent on the element location and due to symmetry, it can be written as:

(2)

The amplitude excitation A(n,m) contains the amplitude and phase required for array radiation pattern synthesis. For in-phase collimated beam at the angle 00), we have:

(3)

The CPPAR array can be focused on the elevation angle that is not necessarily broadsided or in the plane of the array 0= π/2). Therefore, the array pattern for the cylindrical array in 00) direction would be:

(4)

 

Picture gallery of cylindrical phased array antennas

Figure 3: NESIS 4000 made by Hensoldt

Source: