DOCSLIB.ORG

Simulation of Direction Finding Algorithm and Estimation of Losses in an RWR System

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Simulation of Direction Finding Algorithm and Estimation of Losses in an RWR System INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 3, ISSUE 8, AUGUST 2014 ISSN 2277-8616 Simulation Of Direction Finding Algorithm And Estimation Of Losses In An RWR System Gowri Satheesh, Athena Karumbaya Abstract: Radar warning receiver (RWR) systems are used to detect radio emissions of radar systems. Its primary purpose is to issue a warning when a radar signal that might be a threat is detected, and subsequently, evade it. RWR systems can be installed in all kind of airborne, sea-based, and ground- based assets and is used for identifying, avoiding, evading or engaging threats. This paper focuses mainly on airborne military RWR systems. The RWR usually has a visual display somewhere prominent in the cockpit to provide visual cues to the pilot regarding the position of the incoming threat. A suitable method of direction finding is required to detect the position of the threat. In this paper, the design of the radio direction finder is based on amplitude comparison to find the angle of arrival (AOA) of the received signal by four antennas circularly distributed. The characteristics of the signal (maximum amplitude and frequency) are specified to provide the identification of the source in addition to the direction. The AOA is determined by taking the ratio of the signal amplitudes between two adjacent antennas due to their associated AOA over 360 degrees direction. This system operates in a wide band of frequency (over 2-18GHz). Software simulations are carried out to validate and find the DF accuracies of the algorithms under various conditions. The effect of external Gaussian white noise, cable losses and phase losses are simulated and studied. Index Terms: RWR, direction finding, Gaussian noise, amplitude comparison, phase loss, cable loss,radar,AOA. ———————————————————— 1 INTRODUCTION 2 SYSTEM DESIGN With the development of radar technology and the The type of antenna proposed to be used in such system must complication of target background, more and more information be frequency independent antenna such as cavity backed o which is not range but also angle need be known to target in spiral antenna, with a half power beam width of 75 . Each an- order to track and orientate accurately. Passive radio direction tenna is followed by a Low Noise Amplifier (LNA) with high finders (DF) are used for finding the angle of arrival of the stability over the frequency band (2-18) GHz. All amplifiers received signal over the whole (360o) direction. This facility must be identical in all lines. Each amplifier is followed by a makes these systems important in military and civilian detector to detect the envelop signals. The analog to digital applications. To simplify the amplitude comparison analysis, converter is used to convert the analog values of signals to the ratio between signal levels which are fed from receiving digital forms to be fed to the signal processing unit which is antennas of the proposed DF is used. This method makes the used to calculate the angle of arrival of the signal. There exists system simple in analysis and implementation and gives a a Pulse Descriptor Word (PDW) Generator block. The purpose good accuracy and resolution over a wide range of of this block is to extract the properties of the received signal, frequencies. The proposed system operates over a wide band like frequency, pulse amplitude, pulse width etc. Then pulse of frequencies and covers the whole (360o). In this system, the amplitudes of the received signal from each receiver channel amplitude comparison is applied between each two adjacent are input to the amplitude comparison block [1]. The SPU also antennas to select the largest and next to the largest has two memories: one is for database including the amplitude to provide the AOA of the received signal. In real specifications of the signals and their associated sources to radio communication channels, it is often found that the provide the source identification. The other is for lookup tables dominant source of interference contains a significant noise including the pre calculated values of the gain for each o component that is impulsive, indicating the probability of large antenna at their associated angles over 360 direction. The interference levels. final part of the system is the console which displays the results. 3 THEORY A. Gaussian Field Pattern It can be assumed that the antennas type is circular aperture with Gaussian current distribution and has Gaussian field ______________________________ patterns. The field pattern of the antenna assembly system is shown in Figure 1 GowriSatheesh is currently pursuing an undergraduate program in electronics and communication engineering in Vellore Institute of Technology, PH-919994820988. E-mail: [email protected] Athena Karumbaya is currently pursuing an undergraduate program in electronics and communication engineering in Vellore Institute of Technology, PH-919597432121. E-mail: [email protected] Fig. 1: Antenna Gain Pattern 29 IJSTR©2014 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 3, ISSUE 8, AUGUST 2014 ISSN 2277-8616 Receiver Boresight Direction (in deg) amplitudes are taken into consideration to be used in the DF Forward Left (FL) 45 algorithm. The direction finding system considered consists of Forward Right (FR) 135 a circular array of 4 equally spaced antennas. It is assumed Aft Left (AL) 225 that there is a single transmitter and the signal arrives at the antenna at the angle of arrival. Aft Right (AR) 315 The received signal is given by TABLE I: Antenna boresights relative aircraft north 푠푡 = 퐴푅푡 휃 − 휃푖 + 푛푖 (2) When a signal strikes the antenna assembly, the individual Where θ and A represents AOA and amplitude of the incoming channel amplitude is measured as well as the difference signal respectively. Ri denotes the gain pattern of the antenna, between each two adjacent antennas to allow the selection of th ii is the angular position of the i (i=1,2,3,4,) antenna and ni is the channels having the largest and next to the largest the receiver noise. The gain pattern of the antenna is given by amplitude. Amplitude comparison RWRs typically use broad- band cavity-backed spiral antenna elements whose patterns ∅ −푘( )2 can be approximated by Gaussian-shaped beams. Gaussian- 퐺 ∅ = 휃 ∅퐵 /2 (3) shaped beams have the property that the logarithmic output ratio slope in dB is linear as a function of angle of arrival. Where ∅ is the angle of incoming signal, and ∅퐵is the antenna Thus, a digital look-up table can be used to determine the half-power beamwidth [3]. The received signal is calculated for angle directly. Each antenna has 180 coverage [2]. The all the four antennas. The two antennas receiving the boresight (pointing direction) of the antenna in each receiver is maximum amplitude are deter-mined and the ratio of the two directed relative to the aircraft pointing direction, according to amplitudes is found. A lookup table of gain ratios of adjacent Table I. Antenna gain is approximated by the following formula antennas is made for angles at an interval of 5.625. The amplitude comparison algorithm relies on the fact that ratio of 훼 2 퐺푑푏 훼 = 퐺푚푎푥푑퐵 − 3( ) (1) the amplitudes received by the antennas is equal to the ratio 휃/2 of the gains corresponding to the two antennas. The amplitude ratio found is compared with the gain ratio lookup table until a B. Gaussian White Noise match is found. The corresponding angle is displayed. A white noise signal is constituted by a set of independent and identically distributed random variables. In a discrete sense, the white noise signal constitutes a series of samples that are 5 LOSSES independent and generated from the same PDF. The PDF can A few other losses have been taken into account when a be described mathematically for a Gaussian distribution. White signal is received. A suitable correction factor must be devised Gaussian noise can be generated using 'randn' function in to minimize the effect of these losses. Matlab that generates random numbers that follow a Gaussian distribution. The algorithm implements the discrete Fourier A. Cable Loss transform to transform data from time into the frequency A coaxial cable carries radio frequency (RF) energy be-tween domain. Via the inverse Fourier transform we filter out the the antennas and the radio equipment. An antenna cable noise. The filtered signal is plotted. The signal is now ready for introduces signal loss in the antenna system for both the amplitude comparison Figure 5 is a possible Gaussian transmitter and the receiver. Loss of signal strength is directly distribution, where the mean (µ ) is 0 and standard deviation (α proportional to the length of the cable segment. As signal ) is 1. This type of probability distribution curve is called the frequency increases, loss increases. The loss is called Standard Normal Distribution. attenuation, which can be measured in decibels per meter. Choosing the appropriate coaxial cable is vital to the success of any antenna installation. If the correct cable is not used, signal loss will be high and transmit/receive performance poor. Important factors to be considered are: 1. Frequency- The higher the frequency, the higher the signal loss over any given cable run distance. 2. Length of cable run- The longer the cable run, the more signal lost. 3. Cable attenuation- The better quality solid core cables deliver lower signal loss Fig. 2: Gaussian distribution curve The transmission losses due to the cables used in the antenna assembly are calculated using the formula given below. The cable considered is an Ultra Low Loss (solid inner conductor) 4 AMPLITUDE COMPARISON ALGORITHM SHF3M cable, manufactured by RADIALL The amplitudes from two antennas, which are directed to the emitter, are used instead of using all of the received 퐴푡푡푒푛푢푎푡푖표푛 푑퐵/푚 = 0.365/ 퐹 (4) amplitudes.
Load more

Recommended publications
  • Reconfigurable Antenna Based System for Spectrum Monitoring
    Reconfigurable Antenna based System for Spectrum Monitoring and Radio Direction Finding Hassan El-Sallabi, Abdulaziz Aldosari, and Saad Alkaabi Emri Signal and Information Technology Corps Qatar Armed Forces Doha, Qatar Abstract A reconfigurable antenna based system for spectrum monitoring and radio direction finding is proposed. The proposed system provides lower complexity and smaller physical size compared to existing direction finding systems based on phase difference of multiple antenna elements or systems based on mechanically rotating antenna. Instead of using multi-element antenna arrays or rotatable directional antenna, we use reconfigurable antenna that has the capability to reconfigure its characteristics to match frequency and minimize polarization loss of incoming signals. The other main feature of the reconfigurable radio direction finder is the use of multiple directional antenna pattern states with multiple pointing directions that cover the azimuthal 360 degrees. I. Introduction Spectrum range dedicated for radio communications is scarce. Communications industry worldwide and new wireless services offered in market increased the demand for the RF spectrum. These demands have a major consequences on frequency allocations to meet no electromagnetic interference requirements. Spectrum management is helps to maintain interference free environment. Part of spectrum management process is spectrum monitoring to ensure proper operation of radio communication systems without harmful interference as required by spectrum management activities. Spectrum monitoring has the following the goals: 1) find out any interference on local, regional and global scale; 2) ensuring acceptable quality in operating systems; 3) provides information on actual use of spectrum bands; 4) provide measurement based inputs to programs organized by ITU to eliminate harmful interference.
    [Show full text]
  • Methods of Radio Direction Finding As an Aid to Navigation
    FWD : MWB Letter 1-6 DP PA RT*«ENT OF COMMERCE Circular BUREAU OF STANDARDS No. 56 WASHINGTON (March 27, 1923.)* 4 METHODS OF RADIO DIRECTION F$JDJipG AS AN AID TO NAVIGATION; THE RELATIVE ADVANTAGES OB£&fmTING THE DIRECTION FINDER ON SHORg$tgJFcN SHIPBOARD By F. W, Dunmo:^, Associate Physicist Now that the great value of the radio direction finder as an aid to navigation is being generally recognized, consider- able importance attaches to the question whether Its proper location is on shipboard, in the hands of the navigator, or on shore. The essential part of a radio direction finding equipment or '‘radio compass'' consists of a coil of wire usually wound on a frame from four to five feet square, so mounted as to be rotatable about a vertical axis. Suitable radio receiving apparatus is connected to this coil for the reception of the radio beacon signals. The construction and operation of the direction finder have been discussed in detail in Bureau of Standards Scientific Paper No. 438, by F.A.Kolster and F.W. Dunmore, to which the reader may refer for further . informa- tion.* The present paper is concerned primarily with a com- parison of the relative advantages of the location of the •direction finder on shore and on shipboard, The two methods may be briefly described as follows; 1. Direction Finder on Shore. --This method, usually con- sists in the use of two or more radio direction finder station installations on shore, each of these compass stations being connected by wire to a controlling transmitting station.
    [Show full text]
  • LORAN-A Historic Context
    ' . Prepared by Alice Coneybeer U.S. Coast Guard, MLCP (se) Coast Guard Island, Bldg. 540 Alameda, CA 94501-5100 Phone 510.437.5804 Fax 510.437.5753 U.S. Coast Guard- Maintenance & Logistics Command Pacific • • • • • • • • • • LORAN-A Historic Context Alaska (District 17) September 1998 ENCLOSURE(2.} ( LORAN-A Context 1. TABLE OF CONTENTS 1. TABLE OF CONTENTS .........•.....................................................•......................•........•..................................•. 1 2. TECHNICAL BACKGROUND ......................................................................................................................... 2 3. IDSTORY OF LORAN-A STATIONS.............................................................................................................. 2 4. LORAN-A IN ALASKA. ..................................................................................................................................... 3 5. LORAN-A DURING THE COLD WAR IN ALASKA (1945-1989) ............................................................... 4 6. NATIONAL REGISTER ELIGffiiLITY EVALUATION .............................................................................. 4 6.1 SIGNIFICANCE OF LORAN-A WITIIIN TilE CONTEXT OF TilE DEVELOPMENT OF AIDS TONAVIGATION ............................................................................................................................... 5 6.2 SIGNIFICANCE OF LORAN-A WITIIIN TilE CONTEXT OF WORLD WAR II IN ALASKA .............. 5 6.3 SIGNIFICANCE OF LORAN-A WITIIIN TilE HISTORIC CONTEXT
    [Show full text]
  • Radio Direction Finding in Air Traffic Services
    A. Novak: Radio Direction Finding in Air Traffic Services ANDREJ NOVAK, D. Se. Traffic Engineering E-mail: [email protected] Review University of Zilina, Faculty of Operation and Economics U. D. C.: 654.165:351.841.31 of Transport and Communications Accepted: Apr. 11,2005 Univerzitna 8215/1, 010 26 Zilina, Slovak Republic Approved: Sep.6,2005 RADIO DIRECTION FINDING IN AIR TRAFFIC SERVICES ABSTRACT Another reason for the importance of Radio Di­ rection Finding lies in the fact that frequency-spread­ The paper analyses the Radio Direction Finding principle ing techniques are increasingly used for wireless com­ for navigation and swveillance system. Radio Direction Find­ munications: this means that the spectral components ing involves locating the bearing of a transmitter called a radio can only be associated with a certain emitter if the di­ beacon. A radio beacon's signal is received aboard a vehicle by rection is known. Direction finding therefore is an in­ a device called radio direction finder (RDF). The navigator turns the antenna ofthe radio direction finder to find the direc­ dispensable first step in radio detection; the more as tion of the radio beacon. The RDF shows when the antenna is reading the contents of such emissions is usually im­ pointing towards the beacon. Radio direction finding is one of possible. the oldest electronic navigation systems for aircraft and ships. It The localization of emitters is often a multistage is generally used as a piloting aid along coastal waters. The process. Direction finders spread across a country al­ range of a radio direction finding signal depends on the type of lowing the transmitter to be located to a few kilo­ radio beacon.
    [Show full text]
  • Radio Navigation Signals
    Radio Navigation Signals This series of articles about radio navigation signals appeared in the WUN-newsletters of November and December 1995 and January 1996. © Worldwide Utility News / Ary Boender 1995-1996 Systems covered in the articles: Alpha DECCA LENA Ralog-20 SYLEDIS AN/SSQ-72 Del Norte Trisponder LORAN-A RANA TACAN AN/TRQ-112 DGPS LORAN-C Raydist Timation AN/TRQ-114 Diff Omega LORAN-D RDF TORAN P100 AN/TRQ-32 GEE MARS-75 RS-10 Transit NNSS Argo DM-54 GeoLoc Maxiran RS-WT1 Tsikada Artemis-3 GLONASS Mini Ranger RS-WT1S Tsyklon Autotape GPS NDB RSBN VOR-DME Bathymetric Guardrail Omega Seafix WJ-8958 BRAS-3 HI-FIX/6 Parus / Tsikada-M SECOR Chayka Hydrotrac Pulse/8 Shoran Consol Hyper-Fix Quick-Fix SPRUT Radio Direction Finding (RDF) Radio Direction Finding (RDF) is the most widespread of radio navigation systems. Most pleasure boats, fishing vessels and larger commercial and naval vessels have RDF equipment onboard. Various countries installed radio direction-finder equipment at points ashore. These stations will take radio bearings on ships when requested, passing that info by radio to the ships. I will explain it in detail using Norddeich Radio as an example. Unfortunately the North Sea DF-net no longer exists, but it gives you a good idea how it works. There are still direction-finder stations in Norway, Pakistan, Bangladesh, Panama and Russia. The radio direction-finding control station of the North Sea direction finding network was Norddeich Radio. Bearings were taken on the freqs 410 and 500 kHz and on freqs between 1605 and 3800 kHz.
    [Show full text]
  • RADIO NAVIGATION AIDS, Pub 117 Searchable Electronic Version Distributed by Starpath School of Navigation
    RADIO NAVIGATION AIDS, Pub 117 searchable electronic version distributed by starpath school of navigation Chapter 1 RADIO DIRECTION FINDER AND RADAR STATIONS PART I RADIO DIRECTION FINDER STATIONS 100A. General. 100B. Accuracy of Bearings Furnished by Direction Finding Stations . 100C. Obligations of Administrations Operating Direction Finding Stations . 100D. Procedure to Obtain Radio Direction Finder Bearings and Positions . 100E. Plotting Radio Bearings. 100F. Radio Bearing Conversion. 100G. Direction Finding Station List . PART II RADAR STATIONS 110A. Coast and Port Radar Station List . Chapter 2 RADIO TIME SIGNALS 200A. General. 200B. The United States System . 200C. The Old International (ONOGO) System . 200D. The New International (Modified ONOGO) System . 200E. The English System . 200F. The BBC System . 200G. Codes for the Transmission of UTC Adjustments. 200H. Shortwave Services Provided by the NIST WWV-WWVH Broadcasts . Station List. Chapter 3 RADIO NAVIGATIONAL WARNINGS 300A. General. 300B. Coastal and Local Warnings . 300C. Long Range Warnings . 300D. Worldwide Warnings. 300E. Worldwide Warnings Message Content . 300F. Warning Message Format . 300G. SPECIAL WARNINGS and Broadcast Stations. 300H. NAVTEX. 300I. U.S. NAVTEX Transmitting Stations . 300J. Worldwide NAVTEX Transmitting Stations . 300K. Ice Information . 300L. Navigational Warning Station List . 300M. WorldWide Navigational Warning Service NAVAREA Coordinators . Chapter 4 DISTRESS, EMERGENCY, AND SAFETY TRAFFIC PART I 400A. General. 400B. Obligations and Responsibilities of U.S. Vessels . 400C. Reporting Navigational Safety Information to Shore Establishments. 400D. Assistance by SAR Aircraft and Helicopters. 400E. Reports of Hostile Activities . 400F. Emergency Position Indicating Radio Beacons (EPIRBs) . 400G. Global Maritime Distress and Safety System (GMDSS) . 400H. The Inmarsat System . 400I. The SafetyNET System . 400J. Digital Selective Calling (DSC) .
    [Show full text]
  • New Aspects of Progress in the Modernization of the Maritime Radio Direction Finders (RDF)
    New Aspects of Progress in the Modernization of the Maritime Radio Direction Finders (RDF) Dimov Stojče Ilčev This paper as an author contribution introduces the the past, the RDF devices were widely used as a radio navigation implementation of the new aspects in the modernization system for aircraft, vehicles, and ships in particular. However, of the ships Radio Direction Finders (RDF) and their modern the newly developed RDF devices can be used today as an principles and applications for shipborne and coastal navigation alternative to the Radio – Automatic Identification System (R-AIS), surveillance systems. The origin RDF receivers with the antenna Satellite – Automatic Identification System (S-AIS), Long Range installed onboard ships or aircraft were designed to identify radio Identification and Tracking (LRIT), radars, GNSS receivers, and sources that provide bearing the Direction Finding (DF) signals. another current tracking and positioning systems of ships. The The radio DF system or sometimes simply known as the DF development of a modern shipborne RDF for new positioning technique is de facto a basic principle of measuring the direction and surveillance applications, such as Search and Rescue (SAR), of signals for determination of the ship's position. The position Man over board (MOB), ships navigation and collision avoidance, of a particular ship in coastal navigation can be obtained by two offshore applications, detection of research buoys and for costal or more measurements of certain radio sources received from vessels traffic
    [Show full text]
  • The Historical Impact of Revealing the Ultra Secret
    DOCID: 3827029 Harold C. Deutsch UNCLASSIFIED @>pproved for Release bv NSA on 10-26-2006. FOIA Case# 51639 The Historical Impact of Revealing The Ultra Secret (Reprinted, with permission from Parameters Journal ofthe U.S. Army War College) We really should not have been greatly surprised. Enigma messages.3 To say this much was, of course, to When Group Captain (Colonel) F. W. Winterbotham·s affirm that the machine had not been invulnerable, that work, The Ultra Secrel, burst on our consciousness in its secrets had been at least partially unveiled, and that it 1974, it undoubtedly produced the most sweeping was Soviet rather than Western specialists who had sensation thus far created by an historical revelation.1 It achieved the near-impossible. Kahn did make one was sweeping. especially, in the sense of seeming to reference to the term " Ultra" but seemed to regard it as demand immediate and wholesale revision of historical merely another designation for the solving of the Japanese assumptions about virtually all that determined the course cipher system known as·· Magic." of World War II in the Atlancic sector. In view of the bombshell impact of Winterbotham's It astonishes one to reflecr on how little speculation book in the following year, it is astonishing how little there had been hitherto about the extent of codebreaking sensation resulted from the publication in 1973 of on the part of the Western Allies and how few pressures Gustave Bertrand's Et1ig"14 ou /11 p/111 grll'flde enigme de there had been on governments to answer perplexing la guerre 1939-1945.
    [Show full text]
  • Direction Finding - Wikipedia
    Direction finding - Wikipedia https://en.wikipedia.org/wiki/Direction_finding Direction finding Direction finding ( DF ), or radio direction finding (RDF ), is the measurement of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication, including radar signals detection and monitoring (ELINT/ESM). By combining the direction information from two or more suitably spaced receivers (or a single mobile receiver), the source of a transmission may be located via triangulation. Radio direction finding is used in the navigation of ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. RDF was important in combating German Radiotriangulation scheme using two direction- threats during both the World War II Battle of Britain and the finding antennas (A and B) long running Battle of the Atlantic. In the former, the Air Ministry also used RDF to locate its own fighter groups and vector them to detected German raids. RDF systems can be used with any radio source, although very long wavelengths (low frequencies) require very large antennas, and are generally used only on ground-based systems. These wavelengths are nevertheless used for marine radio navigation as they can travel very long distances "over the horizon", which is valuable for ships when the line-of- sight may be only a few tens of kilometres. For aerial use, where the horizon may extend to hundreds of kilometres, higher frequencies can be used, Direction finding antenna near the allowing the use of much smaller antennas. An automatic direction finder, city of Lucerne, Switzerland which could be tuned to radio beacons called non-directional beacons or commercial AM radio broadcasters, was until recently, a feature of most aircraft, but is now being phased out [1] For the military, RDF is a key tool of signals intelligence.
    [Show full text]
  • Handheld-Radio-Direction-Finder.Pdf
    Handheld Radio Direction Finder Hurrying Nero trellises no pigsty wintles next after Stephen implicated unfittingly, quite plano-convex. Subtropical and natural-born Trent palm, but Pieter upstate grieves her canonisation. Towy and cancroid Sydney gabblings her spinnakers forspeak unpriestly or pardons rightly, is Hy gestic? PDF The paper analyses the resort Direction Finding principle for navigation and underground system. The VECTOR-Finder Series of VHF Radio Direction Finders. Please install the radio contesting is. It is a radio direction finder with the qualities of a receiver in soft hand-held format RF interference is often difficult to detect particularly if parsley is sporadic or hidden. Radio Direction Finding Gloucester County emergency Radio. DF-500 Direction Finder Collins Aerospace. The NOVATECH DF-500N is very hand-held direction finder DF designed to. US4003060A Direction finding receiver Google Patents. Direction Finding & Geolocation Quasar FS. Radio Frequency Detection Spectrum Analysis and Direction. In the result optimum dynamic range sensitivity and direction finding DF accuracy with power given antenna array are obtained The mobile sensor IZT R5506. Stieber Marcel Colman Eric Radio Direction Finding OATD. Radio Direction Finding Basics Copyright Santa Clara County. ACR Vecta 406 Portable Direction Finder ACR PDF. Radio direction finding RTL-SDRcom. The N0GSG Portable Radio Direction Finde N5DUX. Vswr of radio handheld direction finder is difficult courses to leak anyway, it is also, and accessories and. A helpful-held direction finder that when connected to your HT or FM scanner can locate. Discussions regarding direction finding and transmitter location. For over 25 years providing radio emergency data acquisition products for global customers in infant research question search and rescue and oil city gas industries.
    [Show full text]
  • Stationary Radio Direction Finding Station of Hf Frequency Band «Krug-M-A»
    STATIONARY RADIO DIRECTION FINDING STATION OF HF FREQUENCY BAND «KRUG-M-A» Stationary radio direction finder “Krug-M-A” is based on product R-300 antenna-feeder system (code «Krug») and is purposed for destination designation to radio emission sources operating in the frequency band 1 – 25 MHz at the distance of up to 2000 km and more. Radio direction finder “Krug- M-A” operates autonomously and in command-executive mode and provides measuring of azimuth and elevation angle of signal radio wave arrival; also it can be used for position of source by SSL method (Single Station Location) with ionosphere radio waves propagation. Radio direction finding post of station “Krug-M-A” that is currently in production comparing to similar posts of the previous generation due to exclusion of crystal filters in receiving and measuring device provides frequency dynamic (when switching antenna elements) selectivity by adjacent channel 93…100 dB and at detuning far zone 110…115 dB instead of 40…50 dB and 68…70 dB (previous generation). COMPOSITION · Direction finding antenna feeder system (AFS) of product R-300 consisting of single circular antenna array (CAA) with diameter 120 m provides signal reception in two subbands 1.0…12 MHz and 12…25 MHz. CAA contains 40 antenna elements (wideband monopoles) with 7 m height enclosed by parasitic reflector; * · Wideband branching signal amplifiers (8 outputs, able to be switched off) – 40 pcs.; · Unit of matrix switch for 40 inputs and 3 outputs; · Four-channel HF band receiver with digital signal processing unit;
    [Show full text]
  • A Radio Direction Finder for Use on Aircraft
    U.S. Department of Commerce, Bureau of Standards RESEARCH PAPER RP621 Part of Bureau of Standards Journal of Research, Vol. 11, December 1933 A RADIO DIRECTION FINDER FOR USE ON AIRCRAFT By Wilbur S. Hinman, Jr. abstract A new type of radio direction finder is described which does away with phasing difficulties by using a single loop antenna having a field pattern modified by dissymmetry in the loop-antenna circuit. Visual indication of the " course" is given, and the direction finder is bilateral and unidirectional. The indication of the "course" is not distorted at any volume level, including complete overload. The characteristics of the incoming signals are not destroyed when "on-course" indications are received, but a loud audio note is produced when the loop antenna is turned either side of " course." The direction finder may be added as a unit to any radio receiving set. It operates on any received signal, with modulated or unmodulated waves. The sharpness of indication is readily controllable. This direction finder is based on the idea of reversing a dissymmetrical loop antenna with respect to ground, thereby producing two equal but opposite dis- torted field patterns. This is accomplished by alternately grounding the ends of a loop antenna through rectifier tubes and applying the voltage induced in the loop antenna by a radio wave to a radio receiver. The output of the radio receiver is also applied to these rectifier tubes, and a zero-center course indicator is so con- nected that when the loop antenna is grounded at one end, the course indicator deflects right in proportion to the voltage induced in the loop antenna for that condition.
    [Show full text]