Design and Development of DOA Measurement PCB using FPGA

Transcription

1 Design and Development of DOA Measurement PCB using FPGA 1 B.Sabitha Rani 2 Ch.Viswandham 3 G.Sreelakshmi M.Tech Department of ECE D & ESDGM Associate Professor, Department of ECE Geethanjali College of Bharat Electronics, Geethanjali College of Engineering And Technology IE Nachara, Hyderabad Engineering and Technology Telangana, India Telangana, India Telangana, India Abstract : ESM (Embedded Support Measure) system consists of System antenna, Receiver, Processor and Display subsystem. Receiver is used for measuring radar parameters within few micro seconds (typ. 1µs). These parameters include frequency, pulse width, PRF, amplitude, scan period etc. The receiver measures all these parameters pulse by pulse and provides the data in digital form. DOA measurement is one of the important parameter to be measured. For this purpose Mono-pulse amplitude comparison technique is used. DOA Measurement PCB along with other hardware is required for DOA measurements. This DOA Measurement PCB is to be designed and developed using FPGAs. Keywords:- ESM system, DOA,FPGA, VHDL I. INTRODUCTION RADAR is an electromagnetic system for the detection and location of reflecting objects such as aircrafts, ships, space crafts, vehicles, people and the natural environment. It operates by radiating energy into space and detecting the echo signal reflected from an object, or target. This energy that is returned to the RADAR not only indicates the presence of a target, but by comparing the received echo signal that was transmitted, its location can be determined along with the target-related information. A transmitter generates an electromagnetic signal that is radiated into space by an antenna. A portion of the transmitted energy is intercepted by the target and reradiated in many directions. The reradiated directed back towards the RADAR is collected b y the RADAR antenna, which delivers it to a receiver. There it is processed to detect the presence of the target and determine its location. A single antenna is usually used on a time-shared basis for both transmitting and receiving when the RADAR waveform is repetitive series of Continuous Wave. The range, or distance, to a target is found by measuring the time it takes for the RADAR signal to travel to the target and return back to the RADAR. The term RADAR is contraction of the words Radio Detection and Ranging. The name reflects the importance placed. [4] II. RADAR EQUATION The power P r returning to the receiving antenna is given by the equation: where P r = [1] (ᴨ) P t = transmitter power G t = gain of the transmitting antenna A r = effective aperture (area) of the receiving antenna (most of the time noted as G r ) σ = radar cross section, or scattering coefficient, of the target F = pattern propagation factor R t = distance from the transmitter to the target R r = distance from the target to the receiver. III. Electronic Warfare (EW) systems Electronic Warfare can be defined as an action that involves the use of electro-magnetic energy to determine and that retains friendly use of electromagnetic (EM) spectrum. Such an action can be used to control the EM spectrum, attack an enemy, or impede enemy assaults via the spectrum. EW can be applied from air, sea, land, and space by manned and unmanned systems, and can target communication, radar, or other services. EW systems can be broadly classified into 3 divisions: Electronic Support Measure (ESM) Electronic Counter Measure (ECM) Electronic Counter Counter Measure (ECCM) ISSN: Page 286

2 Military operations are executed in an information environment increasingly complicated by the electromagnetic (EM) spectrum. This portion of the information environment is referred to as the electromagnetic environment (EME). In EW systems, reconstruction of electromagnetic environment depend both on detection of the electromagnetic signals input to the antennas and on characterization of signals. Electronic Support Measure (ESM) involves actions taken to search for intercept, locate and immediately identify radiated EM energy for the purposes of immediate threat recognition and the tactical employment of forces. The ESM system is used to measure the parameters of radar emissions in the operating frequency range along with pulse width, pulse repetition frequency, signal strength, antenna scan period, direction of arrival, etc,. These systems are installed in warships, air crafts and submarines. The major difference between an ESM and RADAR is that ESM is a receiver alone while the latter is a transreceiver. The advantages of ESM systems are that they are completely passive and provide greater ranges than the maximum range of sensors such as RADARs, lasers, SONARs. Key functions of ESM are Intercepting Identifying Analyzing and Locating sources of radar signals. IV. ESM System Features Low weight ESM system, Split AHU for ship suitability Wide frequency range, Single rack for receiver processor and monitor 4-antenna configuration, Menu driven MMI online help menu 4.1 Range of ESM The range of a radar is given by equation R =....(ᴨ) [2] PT = transmitter power GT = gain of the transmitting antenna GS = gain of the ESM system = radar cross section, or scattering coefficient, of the target Ps = power of the ESM system V. Overview The parameters measured by an ESM system include frequency, pulse width, PRF, amplitude, scan period etc. The receiver measures all these parameters pulse by pulse and provides the data in digital form. DOA measurement is one of the important parameter to be measured. For this purpose amplitude comparison technique is used. DOA computation PCB along with other hardware is required for DOA measurements. This DOA PCB is to be designed and developed using FPGAs. Briefly, we can describe the project as follows. It involves design, development and manufacturing of DOA computation PCB for ESM system. It involves design and manufacture of an electronic circuit using digital ICs, FPGAs and interface circuits. The design is to be verified for its functionality before fabrication. BEL standard processing techniques will be used in the work. VI. Direction of Arrival (DOA) It is also called the direction finding (DF) used for accurately determining the direction and the angle of the arrived RADAR signal to the ESM. There are various techniques for determining the DOA (DF). They are Amplitude Comparison DF Digital Bearing Discrimination (DBD) Phase Comparison (Interferometry) DF Differential TOA Rotary DF (RDF) ESM provides greater range than the RADAR. ISSN: Page 287

3 6.1 DOA Waveform The ADC convert bits are stored in the EPROM and fed to the FPGA. The FPGA is fed with the digital video bits along with the 8bit frequency bits. At receiver a 5bit magnitude and 4bit sector bits as output from the FPGA. The magnitude bits and the sector bits are stored in the DOA EPROM and these values can be used to detect the direction of arrival. IX. Field Programmable Gate Array (FPGA) Figure 1. Waveform(Bore sight & Crossover) VII. BLOCK DIAGRAM Field- Programmable Gate Array, a type of logic chip that can be programmed. An FPGA is similar to a PLD, but whereas PLDs are generally limited to hundreds of gates, FPGAs support thousands of gates. They are especially popular for prototyping integrated circuit designs. FPGA IC used in the circuit is XQ4013E (U26).[8] 9.1 Features of FPGA VIII. Figure 2. Block Diagram CIRCUIT DESCRIPTION RAM TM memory: on-chip ultra fast RAM Synchronous write operation Dual-port RAM option Abundant flip-flops Flexible function generators Dedicated high-speed carry logic Wide edge decoders on each edge Hierarchy of interconnect lines Internal 3-state bus capability 9.2 Wave Forms Input from the six video channels is given to peak holding circuit. The peak holding circuit issued to hold the peak of the video signals and vary the pulse width of the video signals. The timing circuits consists of an or gate and a multivibrator for peak holding TAC1 & TAC2 are the input given to the peak hold circuit from the timing circuit from the timing circuit.the timing circuit is mainly intended from timing synchronization.the signals from the peak hold circuit is given to the ADC which coverts it into digital signal. Figure 3. Signal wave Form ISSN: Page 288

4 Hence, there is a scope for the development of a better technique for DOA computation. Figure 4. Timing Circuit X. CONCLUSION Electronic support measures (ESM) are a division of Electronic Warfare (EW) which gathers intelligence through passive "listening" to electromagnetic radiations of military interest. Upon detecting a foreign system, a library of technical and operational data on them is generated. Utilizing that library, ESM provides tactical combat information. The library includes information on various parameters like direction of arrival (DOA). DOA also called the direction finding (DF) is one of the important parameter to be measured as it is used for accurately determining the direction and the angle of the propagating radio-frequency wave incident on an ESM Antenna Head Unit (AHU). DOA can be measured by various techniques. The present techniques used for DF finding such as Magnitude and Sector. This technique provides various estimates of the direction called bearing estimates. This technique includes the problem of discriminating accurate bearing estimates from the given estimates as they are likely to be corrupted by gross error. Moreover, in this technique, the discriminate function is based on the statistics of the noise background. The reliability is also low. Amplitude Comparison technique overcomes these drawbacks and is therefore used in this paper ford direction finding. Amplitude Comparison Technique is a very simple technique. The hardware necessary for this technique is easily available and inexpensive. It provides more accuracy with precision adjustment. This technique is less prone to background noise. It is the best method out of scores of techniques available for direction finding. Our project is a prototype successful working model for DOA computation. The other techniques used for DOA measurement like Digital Bearing Discrimination, Phase Comparison, Differential Time of Arrival (TOA) and Rotary DF should not have antenna mismatch. Matching is stringent in these techniques. However if there is a mismatch in Amplitude Comparison Technique it could be corrected through channel calibration. Channel calibration can be conveniently performed by programming EPROMs. All these drawbacks reinforce the use of amplitude comparison technique for direction finding. XI. REFERENCES [1] Zhizhang Chen, Gopal Gokeda, Yiqiang Yu Introduction to Direction-Of-Arrival Estimation, 1st ed., Artech House, Boston, 2010 [2] Sathish Chandran, "Advances in Direction-of-Arrival Estimation", 1s t ed., Artech House, London, 2005 [3] Johnson, R.L., Miner G.E. Bearing discrimination methods for MUSIC, ESPRI and moving window, Military Communications Conference, MILCOM 90, Conference Record, A New Era IEEE.. [4] [5] [6] Passive Direction Finding.rar [7] [8] programmable_gate_array [9]VHDL Tutorial - Jan Van der Spiegel, University of Pennsylvania, Department of Electrical Engineering ISSN: Page 289

5 BIO DATA OF AUTHOR B. Sabitha Rani had completed B Tech (ECE) from Geethanjali College of Engineering & Technology,cheeryal, Hyderabad, Telangana, India. He is pursuing his Master s degree in Very large-scale-integration (VLSI). from Geethanjali college of Engineering & Technology, Cheeryal Hyderabad. Telangana India. in configuring in-house ESM for Naval platform and had won R&D award from BEL. He has also pursued his Master s degree in Digital systems from Osmania University during work at BEL. He joined IETE recently as FELLOW. Presently he is working as Deputy General Manager in D&E division at BEL, Hyderabad BIO DATA OF AUTHOR (S) Ch Viswanadham joined Bharat Electronics as Deputy Engineer in 1990 after completion of B Tech (ECE) from Nagarjuna University, Guntur, Andhra Pradesh. He has rich experience in Design, Production, Testing, Integration & commissioning of ESM systems on different types of Naval platforms. He was instrumental G.Sreelakshmi working as Associate Professor in Geethanjali college of Engineering and Technology, Department of ECE, cheeryal, Hyderabad, Telangana. She completed her Bachelor s in Electronics and Communication form J.N.T.U. Hyderabad. She did Master s in Digital systems. She has 12 year of experience in teaching profession. VLSI and low power vlsi is an interested area and started her career as Associate Professor in Sreenidi Institute of Science and Technology Ghatkesar, Hyderabad, Telangana, India ISSN: Page 290