Projects:2015s1-21 Inexpensive Portable Radar System

Project Background

Project Overview

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.

Project Team

Student Members

Mohammad Hasan

Bachelor of Engineering (Honours)()

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

Mr Hong Gunn Chew

Definitions

CPU: Central Processing Unit

FFT: Fast Fourier Transform

FMCW: Frequency-Modulated Continuous-Wave

GPU: Graphics Processor Unit

GUI: Graphical User Interface

ISM: Industrial, Scientific and Medical

MIT: Massachusetts Institute of Technology

PCB: Printed Circuit Board

PRT: Pulse Repetition Time

RADAR: RAdio Detection And Ranging

RF: Radio Frequency

RPi: Raspberry Pi

SAR: Synthetic Aperture Radar

SVN: Apache Subversion

USB: Universal Serial Bus

VCO: Voltage Controlled Oscillator

Project Aims and Objectives

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

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

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

Add new functionality- Implement at least one new function to the system. (Lost marks for not providing some funcationality choices)

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.

Reimplementing RF System:

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

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.

Implementing an Interface:

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

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.

Motivation and Significance

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 desgin, and power. The final product shall be used by the continuing honours team next year and eventually as a classroom demostration tool. With the potential of becoming a teaching instrument, many future students may benifit from the successful compeletion of this project. Thus this project is motivated by personal gain and the potential to help students get an understanding on the fundamentals of RF engineering. Such a project has vast significance for students as it will help them gain this understanding.

Knowledge Gaps and Technical Challenges

The topic of radar is one which our group has not had exposure too, especially its underlying workings. This introduces many knowledge gaps and technical challenges which will arise throughout the lifespan of this project. As a group, areas such as radar fundamentals, circuit design and workings, programming and power supply are all areas which shall require additional research. Unique knowledge gaps and challenges refering to each objective, stated in section 1, are outlined below.

Objective 1: Reimplementing Processing Procedure Processing Power:

The Raspberry Pi features a 700MHz ARM processor, which is suitable for most applications. However, signal processing requires a large number of calculations (fast fourier transforms specifically) and thus the Raspberry Pi could potentially lack the power to produce results in real time. According to the results of fast fourier transforms at different lengths recorded on the Raspberry Pi, the time taken to perform a FFT with 8192 data points using ARM is approximately 5 seconds. Real-time processing is impossible with the computations taking this amount of time. Fortunately, an alternate method of computing FFTs has been developed. This C library designed specifically for the Raspberry Pi utilizes the GPU to calculate the FFT, speeding up the process by up to 1200%. For a 8192 point FFT, this method only takes and average of 0.7 seconds, allowing for signals to be processed in real time. A caveat of this design slightly reduces precision as single precision floating points are used instead of double precision. Reducing the sampling rate will decrease the time required for calculating the FFT, at the cost of reduced accuracy. Performing FFTs on shorter sequences also reduces the computation time. For example, instead of performing a single FFT over a 1 second period with 8192Hz sampling rate, two 4096 point FFTs can be performed with less overall computation and in therefore less time.

Objective 2: Reimplementing RF System

RF PCB Design:

RF PCB design is not like regular PCB design and comes with a detailed set of requirements and design suggestions. This type of PCB design requires taking into account difficulties such as impedance matching and transmission line charateristics. Along with reviewing hobbyist designs and design documentation, bridging this knowledge gap shall require continuous practice of the design on Altium Designer.

RF PCB Soldering:

Soldering RF components is unlike regular soldering as the PCB and components are far more sensitive to damage. Due to this, it is possible to attach the RF components onto the PCB using a solder gel. To overcome this difficulty, we shall practice attaching unused components onto an unused PCB.

RF PCB Components:

As we have not designed any system like this before, thus the integration of components shall pose new challenges for us. One such challenge includes the correct use and manipulation of component data sheets. As Altium Designer can test a designed PCB, we are able to ensure our design works correctly before moving on from this stage.

PCB Construction:

The contruction of the RF PCB shall be done on a new machine which we have no knowledge on its operated. The university shall provide appropriate tutorials for us to learn how to operate this machine.

Altium Designer:

The design of a 2 or 4 layer PCB on Altium Designer is also new to us. The Altium libraries may not contain all required components for our design, and thus new footprints must be designed from scratch \cite{altium}. Adelaide University provides tutorials for Altium Deisgner and our technical advisor, Pavel Simcik, will be abe to provide guidance.

Objective 3: Reimplementing Power Source

Components Selection:

We havent done any project like this before. The components Selection and integration of components will be the new challenges for us. Such as we dont have enough knowledge about the batterys and PCB components, we have to make sure our selections and design correctly. Otherwise, we will waste time and money.

PCB Design & Construction:

The construction of the power source PCB shall be designed by using Altium Designer. But we dont have enough knowledge for this, the University of Adelaide will provide tutorials for the Altium Designer.

Objective 4: Implementing An Interface

Graphical Data Output:

The output from the radar must be represented in a easy to read, yet meaningful format. This will require learning of C++ graphical implementations. SDL and QT are two possible libraries that could be used, the advantages and disadvantages of both will be considered in terms of performance and funcitonality.

Objective 5: Implement Radar Scanning

Components Selection:

The main challange of implementing the radar scanning is in choosing the right motor system. As the motor needs to be implemented with the Raspberry Pi, a motor system which is compatable is critical.

C++ Implementation:

As the rotating motor system uses many range calculations, ensuring the Raspberry Pi and the stepper motor are synchronised will be challenging. This will require learning C++ implementations.