EMBEDDED SYSTEM-SIGNAL PROCESSING RADAR

                              

  Abstract:

         This contribution describes radar signal processing using embedded system as a computational unit. The idea presented in this paper is that the basic algorithms of radar signal processing are simple enough to be executed in real time through the inexpensive devices with low power consumption and compact size. Such solution can be utilized in many mobile applications including the multi-modal fusion of radar data with video. This paper describes the overall approach and the achieved results.

INTRODUCTION

Nowadays, the ground radar systems are mostly used for controlling airspace or making weather. These systems consist of large antenna, a lot of the electronic equipment and very powerful computational unit . Smaller versions of these systems are often carried on the board of planes but still they are quite complex devices. Much simpler versions of the systems mentioned above but still using the same basic principles are small compact devices for measuring speed of vehicles, determination distance of a robot from the obstacle, or even a movement detection for opening doorsor turning lights on. In these applications, the compact all-in-one solution (the radar module) can be used. Then real time processing of a radar signal can also be much simpler. For the above mentioned simple applications, it is possible and reasonable to have small devices with low power consumption that perform real time processing algorithms. Typical todays embedded ARM based processor solutions have enough computational performance and their electric input is also very low. Moreover, the dimensions of processor boards are very compact and they can be easily integrated into very small cases. Thats is why it is good to transfer radar signal processing algorithms to the embedded system.The recent development in the radar signal processing presents new ideas in frequency modulated radars , and in fusion of the Doppler radar and video information for automated traffic surveillance.

EMBEDDED SYSTEM

An embedded system is a special-purpose computer system designed to perform a dedicated function. Unlike a general-purpose computer, such as a personal computer, an embedded system performs one or a few pre-defined tasks, usually with very specific requirements, and often includes task-specific hardware and mechanical parts not usually found in a general-purpose computer.

Small Scale embedded systems

 The system which is used in small scale industry is known as small scale embedded systems. It is designed with 8 or 16 bit micro controller. These systems have little hardware and software complexity. This involves board level design and also battery operated. The programming tools which are used in this system are an editor, assembler, cross assembler and micro controller. The C language is used for developing the small scale embedded systems. Also C program compilation is done into assembly. The main important thing is the software has to fit within the memory available.

Medium Scale embedded systems

 The system which is used in medium scale industry is known as medium scale embedded systems. It is designed with single or few 16 or 32 bit micro controller. Instead of the micro controller, DSP/RISC may be reduced. The medium Scale embedded systems have both hardware and software complexity. The programming tools used for this medium Scale embedded systems are RTOS, source code engineering tool, simulator, debugger and Integrated Development Environment (IDE). In this an assembler is used as a little bit. The medium Scale embedded systems may employ readily available ASSPs and IPs for various functions.

Sophisticated Scale embedded systems

 The system which is used in large scale industry is known as sophisticated Scale embedded systems. The sophisticated Scale embedded types of systems have enormous software and hardware complexities. The sophisticated Scale embedded systems need scalable processors and programmable logic arrays. This sophisticated Scale embedded systems are used for cutting edge applications. The some of the function of hardware resources in sophisticated Scale embedded systems can be implemented by the software. The development tools for these sophisticated Scale embedded systems may not readily available. The software functions such as encryption can be implemented in hardware to get an high speed.

CHARACTERISTICS:

Common characteristics of these systems are the following:

Frequently, embedded systems are connected to the physical environment through sensors collecting information about that environment and actuators controlling that environment.

Embedded systems have to be dependable. Many embedded systems are safety-critical and therefore have to be dependable. Nuclear power plants are an example of extremely safety-critical systems that are at least partially controlled by software. Dependability is, however, also important in other systems, such as cars, trains, airplanes etc. A key reason for being safety-critical is that these systems are directly connected to the environment and have an immediate impact on the environment.

EFFICIENCY OF EMBEDDED SYSTEM:

Embedded systems have to be efficient. The following metrics can be used for evaluating the efficiency of embedded systems:

1. Energy: Many embedded systems are mobile systems obtaining their energy through batteries. According to forecasts [SEMATECH, 2003], battery technology will improve only at a very slow rate. However, computational requirements are increasing at a rapid rate (especially for multimedia applications) and customers are expecting long run-times from their batteries. Therefore, the available electrical energy must be used very efficiently.

2 Code-size: All the code to be run on an embedded system has to be stored with the system. Typically, there are no hard discs on which code can be stored. Dynamically adding additional code is still an exception and limited to cases such as Java-phones and set-top boxes.

Due to all the other constraints, this means that the code-size should be as small as possible for the intended application. This is especially true for systems on a chip (SoCs), systems for which all the information processing circuits are included on a single chip. If the instruction memory is to be integrated onto this chip, it should be used very efficiently.

EMBEDDED SYESTEM DEVELOPMENT KITS:

Processor Designers provide Evaluation and Development kits to their potential customers. If you are starting a new project (or are new to embedded system development field), evaluation kits are the best way to start. These kits come with a Processor and minimum system components. Development kits are a upgraded version of Evlauation kit, which contain domain specific components (e.g. automobile, cellphone, medical electronics). Most vendors provide special discounts on these kits to Students and Universities. Here are some links to the development boards of some popular embedded processors.

• Microchip PIC Starter kits
• MIPS Development Boards
• ARM Development Boards
• Texas Instruments DSP Development Kits
• SHARC Development Boards
• Blackfin Evaluation Kits
• Blackfin Development Boards
• Blackfin uclinux development boards

EMBEDDED IMPLEMENTATION

The presented embedded radar system physically consist of two major components (interconnected through the stereo audio channel). One of them is the radar module, a sensor able to detect objects using microwave signal. Second and equally important part of the system is the embedded processor board that is mainly concentrated on execution operations of the processing algorithm

RADAR MODULE

.

The radar module transmits a narrow beam of microwave energy with the specific frequency. After the moving object reflection, the integrated antenna (situated on the front side of the module) receives appropriate echoes with a slightly different frequency because of the Doppler effect. These two signals are mixed and amplified inside, and the output of this black-box is the signal with the appropriate Doppler frequency. More precisely, the sign of the Doppler shift is indicated by the phase difference of equal frequency components of two corresponding signals on the complex output channel pair (exactly it is +90_ and 􀀀90_). For the purpose of the embedded signal processing, the output voltage levels of the radar module are adapted using stereo amplifiers and further it is possible to process signal the same way as audio.

EMBEDDED PROCESSOR BOARD

The processor board is a platform for real time execution of processing algorithms. These boards usually run one of number of embedded Operating Systems , typically it is the Linux, Windows CE, etc. Compilation of custom applications is performed with the technique called cross   compilation .It means that the building of programs is realized on the side of the host PC, and then it is copied to the embedded device. These processor boards have almost the same functionality as a common computer, only the computational performance is usually significantly lower. Moreover, these processors usually do not have the floating point unit, so the drop of performance in case of the floating point operations is large. On the other side, the best advantage of these processor boards is a very low power consumption and  compact  dimensions.

<!--[if !vml]--><!--[endif]-->

Automotive radar has also been available, as with the other sensor types, chiefly on high-end vehicles. It can have high safety value because of its sensitivity in detecting and locating other vehicles, especially at highway speeds, and is referred to as long-range radar because it looks for obstacles that are 200–300 m ahead. Long-range radar has been combined with the vehicle's cruise control to create what is known as Adaptive Cruise Control.

Here's how it works: Suppose you are driving at 80 mph in the fast lane on an interstate highway and you're using cruise control. The car ahead of you, also  in the fast lane, going at a speed of only 75 mph. The long-range radar will spot the car, note its location and speed, and communicate with your cruise control to lower your speed to 75 mph and to keep a safe distance between the two cars. If the car ahead speeds up to 80 mph or more, or if it moves to the right, Adaptive Cruise Control will boost your speed back up to 80 mph. At any speed, however, long-range radar can work to maintain a safe distance between your vehicle and the vehicle ahead and thus avoid rear-end collisions.

Electronic systems installed in automobiles have generally undergone more rigorous development than systems destined for most other applications. The automotive environment subjects electronics to drastic temperature fluctuations, noxious fumes, and endless shock and vibration. Under normal circumstances, lopping a small percent off the cost of manufacturing a PCB populated with integrated circuits, resistors, capacitors, connectors, and all the rest would be a significant challenge.

We can understand part of the cost if we consider the steps involved in applying a plastic-encapsulated microcircuit (computer chip) to a PCB. The chip is removed from the plastic tube or tape that it was supplied on, is picked up by a vacuum or tweezers, and placed on the solder paste on the PCB. Later, the whole board is heated to around 260°C to melt the solder so that the metal leads sticking out of the microcircuit can make electrical connections with the board. After cooling, the board is cleaned and tested. Many handling steps are involved, presenting many opportunities for damage to the plastic-encapsulated microcircuit.

CHIP IN POLYMER

Chip in Polymer begins with a very thin substrate—much thinner than the typical PCB. The substrate may be FR4 (a glass-reinforced epoxy laminate) or copper. The item to be embedded is typically a silicon chip. The silicon chip, previously thinned to a thickness of approximately 50 µm, is adhesively bonded face up onto this substrate. Then a layer of resin-coated copper is placed on top. The resin conforms to the height of the chip so that the copper layer on top remains flat.

When the resin has cured, a laser drills holes down through the copper-resin to the contact pads on the chip. The holes are plated with copper, and the copper layer on top is etched in a pattern that leaves only the copper traces that will connect the chip to the rest of the system

 RADAR PPI SCOPE

It is a polar coordinate display of the area surrounding the radar platform. Own position is represented as the origin of the sweep, which is normally located in the center of the scope, but may be offset from the center on some sets. The ppi uses a radial sweep pivoting about the center of the presentation. The sweep rotates on the display just as fast as the radar antenna. This results in a map-like picture of the area covered by the radar beam. A long-persistence screen is used so that the targets remain visible until the sweep passes again.

Advantages

<!--[if !supportLists]-->·         <!--[endif]-->High resolution distance measurement

<!--[if !supportLists]-->Ø  <!--[endif]-->Mm-wave FMCW radars can have very high resolution for ranging, velocity and imaging application.

<!--[if !supportLists]-->Ø  <!--[endif]-->A distance measurement resolution of 2 cm can be easily achieved over 20-30 meters.

<!--[if !supportLists]-->Ø  <!--[endif]-->It  require less processing power.

<!--[if !supportLists]-->Ø  <!--[endif]-->Measurements of moving targets are of course possible, but requires more powerful algorithms

<!--[if !supportLists]-->Ø  <!--[endif]-->and hardware.

<!--[if !supportLists]-->Ø  <!--[endif]-->very limited distances.

<!--[if !supportLists]-->·         <!--[endif]-->Quick updating of measurement

<!--[if !supportLists]-->Ø  <!--[endif]-->Because FMCW mm-wave radars are continuously transmitting a signal, there is little delay in

<!--[if !supportLists]-->Ø  <!--[endif]-->measurement updates, as can be the case with pulsed systems.

<!--[if !supportLists]-->Ø  <!--[endif]-->Systems based on lasers, ultrasonics, or infrared will have similar update speeds to FMCW

<!--[if !supportLists]-->Ø  <!--[endif]-->systems.

<!--[if !supportLists]-->·         <!--[endif]-->Functions well in many types of weather and atmospheric conditions

<!--[if !supportLists]-->Ø  <!--[endif]-->It has excellent performance in rain, humidity, fog and dusty conditions.

<!--[if !supportLists]-->Ø  <!--[endif]-->Heavy rain is generally required before a reduction in range or resolution occurs.

<!--[if !supportLists]-->·         <!--[endif]-->Better at detecting tangential motion than Doppler based systems

<!--[if !supportLists]-->Ø  <!--[endif]-->Infrared and video based systems are also excellent at detecting movement, but may not be able to quantity the direction or magnitude of the movement.

<!--[if !supportLists]-->·         <!--[endif]-->Disadvantages

<!--[if !supportLists]-->·         <!--[endif]-->Reduced range compared to pulse radar

<!--[if !supportLists]-->Ø  <!--[endif]-->Due to the generally lower peak power output of FMCW radar systems, their long range performancecan be lower than compared to pulsed systems.          

<!--[if !supportLists]-->·         <!--[endif]-->More expensive than competing technologies

<!--[if !supportLists]-->Ø  <!--[endif]-->Compared to infrared and ultrasonic systems, FMCW systems will generally be far more expensive.

<!--[if !supportLists]-->·         <!--[endif]-->Susceptible to interference from other radio devices

<!--[if !supportLists]-->Ø  <!--[endif]-->Because they are continuously transmitting across a frequency band, FMCW systems may be moresusceptible to interference from other electronic systems.

<!--[if !supportLists]-->Ø  <!--[endif]-->Pulsed systems can generally overcome interference by increasing transmitted power or by switching frequencies.

<!--[if !supportLists]-->Ø  <!--[endif]-->Distance measurement or detection systems using infrared, video, or lasers are generally immune to interference, given their operating principles.

CONCLUSIONS

It has been demonstrated that the radar signal processing algorithms can be easily executed on the

low cost and not so powerful embedded processors. Due to using the fixed point arithmetic for the

implementation of the critical parts of the algorithm, it is possible to perform the signal processing in

real time. Moreover, these systems has very low consumption and thanks to its compact dimensions

it can be mounted on the robots, integrated to the front mask of cars, used as a movement detector,

etc. Further, the radar data can be fused with the video data for improved detection of the objects in

environment.

REFERENCE

[1] Purdy, R. J., Blankenship, P. E., Muehe, Ch. E., Rader, Ch. M., Stern, E., Williamson, R. C.:

Radar Signal Processing, Lincoln Laboratory Journal, vol.12, no.2, pp.297-320, 2000

[2] Skolnik,M.: Radar Handbook, Third Edition, New York, NY, USA, McGraw-Hill, 2008, ISBN

00-71485-47-3

[3] Griffiths, H.D.: New ideas in FM radar, Electronics Communication Engineering Journal, vol.2,

no.5, pp.185-194, Oct 1990