Projects:2015s1-21 Inexpensive Portable Radar System

The Inexpensive Portable Radar System project is a continuation of the MIT Coffee Can Radar. The project is now in its third year of development.

This project is primarily being undertaken to expand on team members knowledge on radar and related areas which have previously been unexplored. Such areas include programming, RF design, and power supply systems. The final product shall be used by a continuing honours team next year and eventually as a classroom demonstration tool. With the potential of becoming a teaching instrument, many future students may benefit from the successful completion of this project.

Project Team

Student Members

Mohammad Hasan

Bachelor of Engineering (Honours)(Telecommunications)

Kieren Nelson

Bachelor of Engineering (Honours)()

Angus Reid

Bachelor of Engineering (Honours)(Electrical and Electronic) with Bachelor of Mathematical and Computer Science

Wenkai (Kelvin) Zhu

Bachelor of Engineering (Honours)()

Academic Supervisors

Dr Brian Ng

Dr Hong Gunn Chew

Project Aims and Objectives

This years Inexpensive, Portable Radar Project team shall focus on three distinct project aims;

1. Reduce Cost- Produce a final product that is cheaper than last years product of $700.

2. Improve Portability- Reduce the overall size of the project (~500x200x200mm) by 30%.

3. Add new functionality- Implement at least one new function to the system.

It was decided to accomplish these aim by undertaking the following objectives: 1. Reimplementing Processing Procedure:

An onboard processor shall process all data, removing the need of a laptop and MATLAB licence. The processor will be required to process the radar data and produce images for both the Range and Doppler mode.

2. Implementing an Interface:

A small, portable screen shall be used as the output of the system to display data processed by the Raspberry Pi via a customised GUI. A 7inch touch screen is available from last years project.

3. Reimplementing RF System:

A new PCB RF system shall replace the current, bulky system as PCB RF components are significantly smaller and cheaper.

4. Reimplementing Power Source:

With new system components, it has been found that a new range of voltages may be required for the system. This requires a new power distribution method which is capable of outputting powers of 6 and 12W (potential to change as system design finalised) and is sufficiently powerful enough to run all components.

5. Implement Radar Scanning:

A rotation system shall be added onto the radar allowing it to calculate the distance of multiple objects in different directions from a single location.

If these proposed objectives are implemented, the finished product will move closer to its desired final state of being a truly inexpensive, portable radar. Such a radar has the capability of being continued on as a Honours Project with a different focus or becoming a classroom teaching tool for the university.

History

Radar is an acronym for RAdio Detection And Ranging. As its name implies, a radar system uses radio waves to detect and capture information regarding distant targets. This information can include the targets range, velocity, or shape. Radar first became industrialised in WWII, however its development began well before then. The first operating radar was built in 1904 by the German Christian Hulsmeyer. This device was a CW radar operating at 650MHz and was capable of detecting ships at sea within 3.2km, however it was unable to determine their distance or movement. The radar was developed concurrently by multiple nations, one of which was the United States. For the US, true progress began in 1934 when Robert M. Page was able to track a plane 1.6km away using a 60MHz pulse radar. With the evolution of the electronics industry, in particular digital to analog converters, the radar has continued to develop to this day. Modern radars are capable of a large number of functions including search, surveillance, target tracking, fire control, and weather monitoring. The use of digital systems has allowed modern radars to increase their sensitivity and overcome performance restrictions from problems such as clutter.

Radar Principle

The basic principle of how a radar works is stated below.

A RF signal is transmitted towards a target.

If the signal hits the target, it will be reflected or scattered off of it. Some of this reflected signal, or echo, will be directed back towards the radar system.

The echo is picked up by the receive antenna of the radar system and is processed for the desired information.

The following radar equation shows how specific radar characteristics relate to one another. Pr = (Pt)G^2*sigma(lambda)^2/((4pi)^3(R)^4)

It can be seen that as the distance of the target R increases the received power, Pr, decreases at a rate of R^4. This indicates that the range of the target plays a crucial role in the radars performance.

Radar Types

The functionality and application of a particular radar depends on several factors including which frequency it opperates at, what type of waveform is transmited, antenna style and placement, and scan strategies. Several radar variations are described below.

Bistatic and Monostatic Radar; A bistatic radar is one where the transmit and receive antenna are seperated by a significant distance (comparable to the target distance). A monostatic radar is one where the transmit and receive antenna are at the same location.

Passive Radar; A passive radar is one which is able to detect a target by processing reflections from non-cooperative sources such as communication or broadcast towers.

Planar Array Radar; This type of radar uses a high-gain planar array antenna. All of the elements in the antenna array are in the same plane, and are capable of directing the transmit signal by varying the relative phase of each element.

Pulse-Doppler Radar; This radar system determines the range of a target using a pulse wave, and uses the Doppler effect of the received signal to determine the object speed. This method combines the features of the pulse and continue wave radars.

Monopulse Radar; A monopulse radar splits the transmit beam into two beams, resulting in two signals being transmitted from the radar in slightly different directions. The received signals are amplified separately and then compared. The stronger of the receive signals indicates the general direction of the target. This method is capable to be used to track a target and is used by most modern radars.

Over the Horizon (OTH); OTH radars are systems capable of detecting targets which are beyond an ordinary radars horizon. Two common methods that can be used to achieve this are to reflect the signal off of the atmosphere, or to use low-frequency radio waves that

follow the curvature of the earth due to refraction.

2015 Honours Radar

The 2015 Honours radar has the following characteristics;

FMCW Waveform

2.4 to 2.5GHz operating frequency

12 to 12.5cm wavelength

Monostatic antenna positioning

1.79m range resolution