The radar in which beam steering is carried out using frequency control of array antenna type is known as frequency scanned radar.

It uses phased array antenna and it is useful for scanning beam in one angular co-ordinate. This radar consists of series fed array.

Following equation mentions relation between radar frequency and beam scan angle:
Δλ = 2*λo*(d/L)sinθs
Where,
Δλ = Wavelength change
λo = Wavelength which corresponds to broadside direction of beam
d = element spacing
L = length of line which connects adjacent elements

## Frequency Scanned Radar operation with block diagram

Figure-1 depicts block diagram of frequency scanned radar type. The frequency scanned radar uses scanning of various types such as single beam scanning, multiple beam scanning, multiple frequency scan, scanning using reflector antenna etc.

The phase difference between two adjacent elements is expressed as follows:
Φ = 2* π * f * L / v
Where,
L = Length of line connecting two adjacent elements
v = Velocity of propagation
Beam steering in one dimension has been implemented by changing radar frequency. The equation for wavelength change for beam excursion of +/-θs is mentioned above.

This frequency scanned radar uses folded waveguide feed referred as serpentine feed. This is shown on left side of the figure. This configuration is useful for scanning pencil beam in elevation along with mechanical rotation which provides azimuth scan.

• Simple in construction