Coffee-Can Radar

Team 1

 Introduction

RADAR is an acronym for

“RAdio Detection And Ranging ”

• It is a system that uses radio waves to detect objects, determine the speed of moving objects and create topographic maps.

• It does these things by bouncing radio waves off the objects in question to determine their location, shape and speed.

The Story behind RADARs

• Great Britain was one of the leading developers of radar in the years leading up to World War II.

• The word "radar" was first used by the U.S. Navy in 1940. At that time, the United States and several other countries were secretly developing radar systems for use in World War II.

wurzburg-reise-radar

Applications overview:

• Auto Parking in Cars.• Automotive safety including collision

avoidance.• Biological research: includes tracking

birds and insects to trace their migration patterns

• Weather-sensing radar systems: they are mostly used to measure wind direction and speed.

• Missile guidance systems: they are used to locate the target of a missile. This is often present in military aircraft.

• Air traffic control: it is used to safely control air traffic where there are no airports.

• Oil and Gas exploration

Water exploration on the surface of other planets as Mars.

Mines inspection.

Locating underground pipes.

Military applications: important part of air defense system, target detection, target tracking.

2. Radar, from theory to implementation:

Basic concept:

• A radar theory is mainly based on the reflection of electromagnetic waves incident on objects of dimensions near their wavelengths are reflected.• So we can detect an objects range if EM

waves are intentionally transmitted at controlled frequencies associated with wavelengths near the required target dimensions, the intercepted waves are received and their delay time measured .

• The range is then simply calculated from the equation:

• It is the simplest form of radar systems which ore called ranging radar, it defines only the target’s range so they are optimized for Parking assist and Measuring long distances.

Transmitters, Receivers:

• Therefore, the basic building blocks for a radar system are signal transmitter and receiver; they use antennas, which are means for radiating or receiving electromagnetic waves,

• In our case we‘ll use Cantennas

• A radar may use one antenna for transmitting and receiving, they are called mono static radars, but will need a duplexer to switch the antenna between the transmitter and receiver and may suffer interference between both

• in our implementation we are using bi static configuration with separate antennas.

Need for Signal Processing :

• In practical cases , it’s inefficient to calculate the time shift for one pulse as in the case of 10 meter target , the shift is equal to = 66 ns which isn’t practically measurable without error, • So another approach is needed , it’s to measure the shift in

frequency for one time instance between the transmitted and delayed signals, the two signals are modulated together making it possible to be used in continuous wave radars • This emphasizes the need for a signal-processing unit in a

radar system.

Doppler Effect Radars:

• Motivated by the need to acquire more information about the target, modifications can be made in the processing stage, for example, we can define the target’s speed using of waves’ Doppler effect of waves, • It’s the frequency shift between the emitted

and received waves due to the relative speed between the wave source “transmitter” and target.• Radars based on this effect are called

Doppler radars, they are optimized for applications like meteorology, aviation and police speed guns.

Synthetic aperture radars:

• Further improvement can be made using the motion of the Synthetic aperture radar antenna over a target region , it provide finer spatial resolution than is possible with conventional beam-scanning radars , they are used in more powerful applications like topographic maps, 2D and 3D imaging and UAVs but they use more complex Algorithms .

Signal Processing:

• In radars, the most important part is signal processing, RF blocks as transmitter and receiver have many physical limitations - antenna size for example – so signal processing comes as a promising research field that determines the overall system capability the most .• It includes analog and digital processing approaches• Analog processing deals with techniques as pulse compression,

coherent Integration

Analog processing

a- pulse compression : • to have a better Signal-to-Noise Ratio we should increase

the average sending power , by increasing the source power “illogical solution”

or increasing the pulse width .• to have a better resolution we should have a wider signal

spectrum .• From Fourier transform waveforms with continuous or long

pulse widths are associated with narrow signal spectrum . • Here we arrive at a trade-off .

• The solution is to use transmitted signal with linearly swept frequency across the pulse width .• It is associated with wider signal spectrum and having

long pulse width . • That satisfies both criteria ! . • Can be achieved using linear signal input to the VCO . • We can use a filter that delays the signal an amount of

time that varies with the frequency of the signal or simply adjust that in Matlab.

b- Coherent Integration:

• A process in which we insert a coherent integrator between the matched filter and amplitude detector .• It sums the received data so that the target power is

increased while noise is random so they can be integrated destructively .

• we use pulse compression technique using a ramp generator and a VCO .

• We adopt digital processing in our implementation because analog processing requires special filters and analog circuits, which means extra cost and complexity .

• These functions can be accomplished instead by digital processing because of their capability, and ability to be performed with Matlab or c codes.

Need for signal modulation:

• A great challenge is the limitation from EM theory to the frequency used for transmitted signals, to reach reasonable ranges and detect practical targets a transmitter should operate in frequencies of Gigahertz .• While the same time the

signal is limited by electronics technology in the processing blocks , circuits are limited to frequencies about megahertz as they suffer from parasitic effects .

How to satisfy both limitations?

• Signal modulation and demodulation techniques are used . • Modulation is the process of varying one or more

properties of a periodic high frequency signal, called the carrier signal with a modulating signal that typically contains information to be transmitted.• Therefore, we use Demodulation, which is the act of

extracting the original information-bearing signal from a modulated carrier wave; we apply demodulation on the reflected signal to extract information in required processing frequencies.

• Mixer circuits are used for the processes.• They are based on the mathematical

concepts that multiplying “mixing” to sinusoidal functions results in the sum of two new frequency-shifted functions ,• One is has frequency equal to the

difference in frequencies which is needed in demodulation and the other is omitted using appropriate filter.• and all waveforms can be reduced to a

summation of sinusoidal of different weight and frequencies .

Conclusions so far:

Following this reasoning, we arrive to the basic blocks for a functioning radar, which are: • Cantennas as Separate

transmitter, receiver.• Simple ranging radar with

ability to consider Doppler Effect using Matlab processing.• Digital signal processing • Use of modulators

Antenna

Definitions

• Antenna Gain• Beam Width• Front to back ratio• Polarization• Input Impedance and VSWR • EIRP• Aperture

Parabolic Antenna

Cylindrical Antenna Pattern (Coffee-Can Radar)

Aperture

Parabolic antenna

Analog Signals Circuit

Basic Communication System

Modulation

• Amplitude Modulation • Frequency Modulation

Triangle modulation in FM-CW Radars Principle

Coffee-Can Radar

Transmitter Blocks

Modulator• a- Produces linear ramp which modulates OSC1 Vtune

input pin– Vtune voltage is proportional to transmit frequency – Linear Ramping of Vtune causes OSC1 to produce a linear FM chirp used for transmit and receive – Set up-ramp time to 20ms, for 40ms triangle wave period– Set magnitude of ramp to desired transmit bandwidth

• b- Produces receive trigger signal synchronized with start

of linear ramp

RF Power Amplifier

An RF power amplifier is a type of electronic amplifier used to convert a low-power radio-frequency signal into a larger signal of significant power, typically for driving the antenna of the transmitter. It is usually optimized to have high efficiency, high output Power (P1dB) compression

SplittersA splitter is a passive device which accepts an input signal and delivers multiple output signals with specific phase and amplitude characteristics. The output signals theoretically possess the following characteristics:

• equal amplitude • 0° phase relationship between any two output signals • high isolation between each output signalInsertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels (dB).

Resistive Power splitters

• Advantages• Simplicity• Cost• Frequency response

• Disadvantages• loss

Hybrid power splitters

• Advantages• loss

• Disadvantages• Complexity• Cost• Frequency response

Receiver LNA

Low-noise RF amplifier (LNA) is an electronic amplifier used to:

1-amplify possibly the very weak signals captured by an the antenna. It is usually located very close to the detection device to reduce losses in the feedline.

2- Provide enough selectivity to reduce the image-frequency response by rejecting these unwanted signals and adds to the sensitivity of the receiver. The borders of the bandwidth of this amplifier are chosen to eliminate the image frequencies.

Mixer• A mixer is used to provide

frequency translation from the input signal to the output signal. When a mixer is used for down-conversion, the input is the RF signal and the output is the IF;

• For given RF and LO frequencies, two nominally equal-amplitude output signals are produced at the sum and the difference of the RF and LO frequencies. Since only one of these sidebands is utilized in most applications

Video Amplifier

Gain stage to amplify output of the Mixer, prevents aliasing of PC’s input audio port

Aliasing is the misidentification of a signal frequency, introducing distortion or error.

Aliasing occurs when a signal is sampled at a less than twice the highest frequency present in the signal.

ADC & SPI

Analog to digital converter

It is used to convert analog signal to digital data using number of steps:

1. Sampling.

2. Quantization.

Why ADC ?

In the real world, most data is characterized by analog signals. In order to manipulate the data using a microprocessor, we need to convert the analog signals to the digital signals.

the microprocessor will be able to read, understand and manipulate the data.

How does an A/D Converter work ?

• The main goal of A/D Converter is to digitize the analog signals, which means to record and store the analog signals in NUMBERS.• There are two parameters to control in converting the

analog signals to the digital signals: 1- Sampling Rate, fs – controls the number of samples taken in a second

2- Sampling Precision, N – controls the number of different gradations (quantization levels) for the sampling process.

Types of ADCs

• Flash.• Pipelined.• Successive-Approximations Register (SAR).• Integrating or Dual-slope.• Sigma Delta (ΣΔ).

Flash ADC

• Flash converters have a resistive ladder that divides the reference voltage in 2N equal parts.• For each part, a comparator compares the input signal

with the voltage supplied by that part of the resistive ladder. The output of all the comparators is like a thermometer: the higher the input value, more comparators have their outputs high from bottom to top

• A dedicated component called "Priority Encoder" translates this gauge into a binary code, which corresponds to the position of the last comparator with high output, counting from the bottom up.

Pipelined

SAR • A successive approximation ADC is a type of analog to

digital converter that converts a continuous analog waveform into a discrete digital representation via a binary search through all possible quantization levels before finally converging upon a digital output for each conversion.• Steps:1. A sample and hold circuit to acquire the input voltage

 (Vin).2. An analog voltage comparator that compares Vin to the

output of the internal DAC and outputs the result of the comparison to the successive approximation register (SAR).

• 3.A successive approximation register subcircuit designed to supply an approximate digital code of Vin to the internal DAC.

• 4.An internal reference DAC that, for comparison with VREF, supplies the comparator with an analog voltage equal to the digital code output of the SARin.

SPI

• It is a synchronous serial communication protocol used for short distance, single master communication, for example in embedded systems, sensors, and SD cards.• Devices communicate in master/slave mode where the

master device initiates the data frame. Multiple slave devices are allowed with individual slave select lines.

Connection between ADC & MCU

• The ADC works in Normal Mode, and as a slave. MCU is configured as a master and provides clock signal as well as control signal (SS) to the ADC.

• ADC sends back converted data from its SDO pin to SDI pin of MCU.

PCB Circuits

we have 3 PCB circuits in our project:

1- power supply circuit .2- video amp cicuit . 3- ramp generator circuit ( modulator ) .

Power Supply Circuit

Input: 6 v & 12v power from battries .Output: 5 v & 10 v & 12 v . Func: regulate the voltage to 5 & 10 & 12 v .

Video Amp Circuit

Input: signal came from MXR .Output: signal to data acquisition.Func: amplifies the received signal by 28 db and makes low pass filtering by sallen Kelly.

ramp generator circuit (Modulator)

Input: nothing Output: 1- modulated triangle wave form to OSC .2- sync signal to audio cable . Func :1- creates the triangle wave that required to chrip the frequency of the oscillator output .

2- makes the synchronization signal to the data acquisition to start processing by the rising edge of the signal .

Online Calculations

• project needs to do two main tasks:

Complete data acquisition in real time Displaying this data to the user.

• MATLAB is unusable, as it cannot process data fast enough in order to give a real-time data. Since compiled code works much faster (in most cases) than interpreted code,• either C++ or a C derivative language would be desired.• C# was as settled on as Visual Studio is able to create

and modify GUI’s very easily.• there is a lot of supported functionality built into C# via the

.NET framework.

The main signal processing support needed is an efficient FFT algorithm. Unlike MATLAB, C# does not directly include FFT support.

However, its functionality can be expanded upon, and a library of FFT and GUI. The Exocortex Digital Signal Processing library was used for FFT support.surpassed. Though the .NET framework does support serial interfacing, which can be extended to USB support, it does not directly support taking data from Line-in ports.

To accomplish this, another 3rd party library was used, which interfaces between the DirectX functionality in Windows, and the C# GUI. This open source library came from The Code Project, and had very good examples to work from.

•In November, it was decided to shift towards supporting the Audio Line-in port in order to show the real-time code works.

•Future work regarding the GUI could go a number of ways. Make the code more efficient, and memory conscious

•Also, porting the code out to a more universally supported language wouldalso be a good step ‘next step’ ,since C# will only work for windows.

Flow Chart

References:

• Introduction to Radar Systems , Dr. Robert M. O’Donnell• Gregory L. Charvat-Small and Short-Range Radar Systems-CRC Press (2014)• W. L. Briggs, V. E. Henson, The DFT, an Owner's Manual for the Dis- crete

Fourier Transform• Radar Systems Analysis and Design Using MatLab - Mahafza Bassem R• https://www.google.com/patents/US5128681?dq=pulse+compression&hl

=en&sa=X&ei=gJTeU_XUGfTy7AaX1IDQBQ&ved=0CBwQ6AEwAA• http://en.wikipedia.org/wiki/Radar

http://en.wikipedia.org/wiki/Continuous-wave_radarhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Pulse_compressionhttp://en.wikipedia.org/wiki/Synthetic_aperture_radar

• http://www.radartutorial.eu/10.processing/sp50.en.html http://www.radartutorial.eu/09.receivers/rx05.en.htmlhttp://www.radartutorial.eu/09.receivers/rx06.en.html