Analysis and Design of Pulsed Doppler Radar for Weather Forecasting

Learning Outcomes

1. Demonstrate knowledge of system engineering and understand how to make a system more reliable and efficient;
2. Acquire technical knowledge of signalling, switching and call routing in Public Switched Telephone Network (PSTN);
3. Understand Public switched Telephone Network (PSTN) and Digital Microwave Radio Systems;
4. Design microwave links, construct a path profile and obtain a comprehensive understanding of the atmospheric effect on the performance of microwave links;
5. Undertake an economic evaluation of telecommunication systems;
6. Understand Radio Navigational Systems;
7. Apply their knowledge of radar systems and their applications.

Purpose and Background of Assignment

This assignment project motivates students to apply their knowledge in telecommunication systems engineering to learn how radar systems are designed and their application in meteorology to forecast weather. Radar (meaning RAdio Detection and Ranging) is electronic equipment which can detect the presence of an object using the echo of electromagnetic waves or microwave signals.

Radar systems enable us to measure the height above sea level, distance, velocity and direction (both elevation and azimuth) of an object called target, such as precipitation, insects, tornados, cyclones, aircraft and cars, using the echo of transmitted electromagnetic signal. The main principle behind the operation of a radar system (as illustrated in Figure 1) is the reflection of electromagnetic waves by the target. A weather radar system uses Doppler effect from precipitation (e.g. rain, drizzle, snow, hail or graupel) echo to estimate the (radial) velocity of wind.

Figure 1: operation principle of radar systems

Problem Statement

Assume that the Australian Bureau of Meteorology (BOM) needs a new pulsed airborne radar system (i.e. Doppler radar aka whether radar or surveillance radar) to replace an existing one located at Laverton Victoria (E144.752, S37.852) in its network of radar systems. The radar network is used for both nowcasting and forecasting of weather, especially for the estimation of the chance of rain, cyclones and/or thunderstorms in Melbourne geographical area. BOM has therefore consulted your team to design appropriate S-band radar (i.e. λ=7.5-15 cm) for it. The required measurement accuracies of your radar are 250 m for range and 1O for angle/direction. The radar should have a maximum range of 150 km. The height of the radar's beam above the ground level is 14 m and Nyquist velocity of VN = λ*PRF/4 = 52.2m/s, where PRF is the pulse repetition frequency and λ is the radio signal's wavelength.

Design Requirements

1. Students' report should demonstrate an understanding of pulsed radar using Doppler principle.

2. Find the pulse repetition frequency (PRF), duty cycle of the pulsed radar system used and how the latter relates to the maximum unambiguous range and minimum range.

3. Your radar system should minimize any measurement errors caused by echoes from the ocean or ground.

4. Your design should estimate any radar parameter not given in the problem formulation.

5. Your design should explain how a single antenna is connected to both a high-power transmitter and a very sensitive receiver without the former destroying the latter.

6. As part of your design of the appropriate radar system your design should consider:
- an economic evaluation to find the total cost of implementing and operating the radar system
- discussing any radio navigational systems which can use your radar system or applied by your radar.

7. Your design should clearly show how the radar system measures the distance (range), height above ground and direction (using the directivity of the antenna) of an object (aka target).

8. Each team should divide the project into tasks and assign tasks to each student, elect a coordinator and a secretary and meet at least once a week to review assigned tasks and ratify work to meet the assignment deadline. Each meeting should be recorded in dated minutes which are appended to the report to be submitted.