Overview

This applet demonstrates many of the concepts taught in the Radar section of the U.S. Naval Academy course ES300, Principles of Navaly Weapons Systems. This applet was written by LCDR Ellery A. Blood in the fall of 2009.

Display

The display has three parts. In the upper left box, the physical arrangement of the radar, pulses, and targets is displayed. In the lower left box, the signal from the radar receiver is displayed. In the lower right box, the image of the Plan Position Indicator (PPI) is displayed.

Radar Receiver Signal

The signal from the radar receiver is plotted as a graph of receiver intensity (dB) (blue jagged line) vs. time from when the pulse was transmitted. A return pulse is indicated by an increase in intensity which is hopefully larger than the noise signal. The receiver threshold level is also plotted on the graph (red horizontal line). An intensity above this line registers as a target and is displayed on the PPI.

Plan Position Indicator (PPI)

The PPI indicates targets from the receiver that exceed the threshold level. The targets are indicated as either an arc or a dot (depending on settings) located with a range consistent with the delay between the transmitted pulse and the target signal being detected. The azmuthal angle is consistent with the direction of the antenna at the time of the received pulse.

Control Panel

The upper right box contains all controls for this applet. The pulldown menu at the top allows you to select one of four submenus: Target Scenarios, Rx Parameters, Tx Parameters, and Antenna Parameters.

Target Scenarios

This menu allows the selection of several pre-programmed scenarios which demonstrate different concepts of radar operation.

Circle Targets

X-Section Demo

Range Demo

Linear

Default

This menu also allows the simulation speed to be modified and paused/resumed.

Receiver (Rx) Parameters

This menu allows the setting of various parameters associtated with the radar receiver:

Threshold Level

Duration of PPI Indications

Receiver Noise

(not really a receiver setting, but useful in simulating the effects of various noise levels on radar operation such as in the case of jamming)

PPI Settings

You can set the PPI to indicate targets as dots or arcs. The width of the return pulse that was received is indicated by the diameter of the dot or the depth of the arc segment. The beamwidth of the transmitted pulse is indicated by the width of the arc segment. You may also choose to display the current antenna direction as the area bounded by two white lines on the display.

Transmitter (Tx) Parameters

This menu allows the setting of various parameters associtated with the radar transmitter:

Pulse Width

Change the width of the pulse (micro seconds). Affects range resolution and duty cycle.

Pulse Repetition Time

Changes how frequently pulses are transmitted. Affects update rate, duty cycle, and max unambiguous range.

Transmitter Peak Power

Changes the intensity of the transmitted pulse. Affects signal to noise ratio.

Antenna Parameters

Beam Width

Adjust the width of the pulse (Degrees). Affects cross range resolution and gain.

Omega (Antenna Rotation Rate)

Adjust how rapidly the antenna rotates. Degrees per pulse [ (Degrees/sec) / (Pulses/sec) ]

Antenna Angle

Move the antenna by a small amount left or right.