RasHAWK - Geon Technologies, LLC
Contents
1. RasHAWK Distributed EM Situational Awareness Based on Raspberry Pi and REDHAWK AOC Susquehanna Tech Challenge 2013 Final Report March 7 2014 AN Y GCON z Technologies LLC MORGAN STATE UNIVERSITY www geontech com Contents e Ko er TO sii Ee oii sas cbt neta tenentur in 1 2 EGAN COMIPOSINIOM EE 2 DS SYSE DES CHIP COM eec 2 3 1 REDHAWK in 30 Seconds maybe more 2 3 2 DySEeroxte MILE e Carrs a cist opens E tu ipso uar f DEDE 3 A S bsystem Descriptions eebe 5 4 Ras HAWKE E EE 6 4 1 1 Rap SDC YP EE 7 4 1 2 RUE SDR USB Radio DOn le ene tei eege 11 4 3 Antenna Switching Subsystem EE 11 5 Application Software Description e ecce eee ee eee eee eee ee teet e eee e s tee eee oaa 13 5 1 Processing Waveform Description cccccccccccceceeasseeeseeseeeeeeeceeeeeeeeeeeeeeaaaags 13 32 DE Technique Descriptio EE 16 5 3 Control User Intel Tae ess ec E ra Md pc dul tel seats 17 5 4 le EE 18 G Applicati n Scenarios n iios eee otro Eno eera aE a oa raias 19 6 1 Distributed Sensor Deployments ice beh Dui ERR P PERDER ee Eeer 20 6 2 Spectrum Situational Awareness and Monitoring ccccccsesssseeseseeeeeeeeeeeeees 20 6 3 Coarse Emitter Locat OM EE 20 7 Demonstration Eet 21 8 Known Limitations of the System cccsscccccsssssssssccccccsssssssssscscccsssssssssscscees 21 9 sensor Elek rial esses css ooo ie eio oto aE oio eO EE eroi 22 O 2013 Geon Technologies LLC 12. Figures Figure 1 RasHAWK System Architecture e 4 Pieur e 2 RASA W Ko SCS E 6 Figure 3 RasHAWK Sensor Block Diagram sees d Figure 4 Raspberry Pi Internal View with Arduino cccccccceeeceeeeeeeeeeeeeeeeeeeeeeeeeeeeees 8 Figures Raspberry Pt Inftercontee UOS eebe 8 Figure 6 raspberry pi Node and its Devieesg seen 10 Figure RTL SDROUSB Radio Dongle uui SQUE a UE 11 Figure 8 Antenna Switch for Pseudo Doppler DF 12 Figure 9 Antenna S witch SCCM all Costs ioo deiecti sends orsi poe idus e pee eds poder 12 Figure 10 RasHAWK Ereegnes en eo eee NUR ede tet NU ege 14 Figure 11 FRS Radio Channel Allocation and Baseband Tuning Offsets 15 Figure 12 Notional Pseudo Doppler DF Swatem 16 Ereegnesser E E SE 17 Figure 14 UI Display Updates as New Waveforms are Launched ooooeeeeeeeeeeeeeereeeeen 18 Figure 15 Mapping Interface Example with Plotted LOBS esses 19 Figure 16 Spectrum and Audio Plots Displayed for Each Sensor 20 Tables Table EECH 2 Table 2 Characterization of the Antenna Switch BC esses 13 Table 3 Antenna Switch Billof Material 22 3 92 21 5000 anne talc oo uei vase 13 Table 4 RasHAWK Sensor Final Bill of Material ccceecessessessessseesesesessessseeseeeens 22 O 2013 Geon Technologies LLC ll 1 Introduction The RasHAWK team has used a Raspberry Pi as the basis for a networked RF sensor capable of suppo
3. JQuery Javascript libraries are used to create a more dynamic user interface The backend uses the open source Python Tornado framework to instantiate an asynchronous webserver on a host laptop O 2013 Geon Technologies LLC 18 This framework is based on the idea of asynchronous connections between the client and server allowing for a persistent bi directional connection between the server and Mapping Interface via Websockets This allows Information updates to be sent in near real time from the server to the client browser Nodes registering with the Domain changes in position and line of bearing LOB data are passed from the server to the Mapping Interface to be updated on the browser display Figure 15 shows an example of the Mapping Interface with node locations and LOBs to the emitter c e E 2 E 5 4 G c a St a lt o D 895 E AB Te d 3 eme EastbournelAve ZS Map data 2014 Google Imagery 2014 Commonwealth of Virginia DigitalGlobe Sanbom U S Geological Survey USDA Farm Service Agency Terms of Use Reporta map error o wr RA Figure 15 Mapping Interface Example with Plotted LOBs 6 Application Scenarios In the system demonstration the goal 1s to demonstrate the following three use cases for the RasHAWK sensor network e Distributed Sensor Deployment e Spectrum Situational Awareness and Monitoring e Coarse Emitter Location These scenarios will be explained brief
4. feasible Our submission to the judges will be a short presentation on the system followed by a brief video of an actual outdoor test of the system The outdoor test will show the system performing the three application scenarios listed earlier If possible we would like to bring a sensor and laptop into the conference room if possible to show the judges Note that both the laptop and sensor will have WiFi capability although we can disable that 1f required While the system is capable of monitoring frequencies from 24 to 1766 MHz for practical reasons demonstration and testing will use unlicensed Family Radio Service FRS radios as the RF target rabbit The rabbit emitters will be GPS enabled networked REDHAWK nodes with the transmitters controlled from the C2 laptop The system demonstration will use FRS radio channels 1 7 covering UHF frequencies from 462 5625 to 462 7125 MHz A grid of three RF sensors will be deployed over an area of approximately 1 2 square mile 8 Known Limitations of the System The RasHAWK system is intended to demonstrate the utility of inexpensive software and components to perform operations typically requiring much more expensive equipment and software That said RasHAWK does not pretend to be a fully capable ISR system it is a demonstration targeted at one particular class of radio transmitter in one frequency band The REDHAWK framework underpinnings of the system are sound and given the correct equipment a
5. 2 fm dataFloat out Ne _ audio in 4 Ve E WS pm dataFloat out M Waveform running on C2 Laptop lobCalc lobCalc 1 Plot Port FFT Plot Port Data dataFloat rz Lim dakarisat ini EI BB PSD Waterfall Audio Figure 10 RasHAWK Processing Waveform O 2013 Geon Technologies LLC 14 The waveform automatically connects to an rtl sdr device using an allocation property in the waveform s Software Assembly Descriptor SAD XML file A separate waveform 1s launched for each active sensor in the system The component ports from which spectrum and audio plots are generated during the system demonstration are also shown in Figure 10 Each component in the application waveform 1s described below sensorIngest Removes any residual DC bias from the RTL baseband data and converts the 16 bit signed integer shorts output from the RTL to floating point values compatible with the next input port in the chain TuneFilterDecimate A stock REDHAWK component which does just that performs a frequency translation of the complex input followed by an adjustable bandpass filter and finally decimates the oversampled filter output For RasHAWK we use the TuneIF mode which extracts the input sample rate from the SRI to determine the bandwidth of the input signal The tuning limits in this mode are sample rate 2 For our demonstration we tune the RTL receiver to a center frequency of 462 6375 MHz FRS Channel 4 with a sample
6. 2 11N wireless router to establish an infrastructure WLAN for the sensor Nodes and Domain to remotely communicate This model router was chosen primarily because its three antenna configuration looked impressive Transmitter Node A late addition to the RasHAWK system is a Transmitter Node that allowed us to remotely key up a slightly modified FRS Radio The transmitter node is essentially a Raspberry Pi sensor node with an added transmit enable device that closes a relay to effectively press the radio s transmit key An old MP3 played is used as an audio source so we didn t have to constantly say Testing testing 1 2 3 The position of the transmitter as determined by the GPS dongle is relayed to the laptop and plotted on the terrain map O 2013 Geon Technologies LLC 5 4 Subsystem Descriptions This section describes each of the main RasHAWK subsystems in detail with particular emphasis on the use of the Raspberry Pi within the system 4 1 RasHAWK Sensor The centerpiece of the RasHAWK system 1s the Raspberry Pi based RF sensor shown in Figure 2 The sensor electronics are mounted on a plywood panel connected to a PVC pipe shaft that holds the four antenna DF array The entire assembly is on a tripod and powered by a 12V 5 0Ah rechargeable battery Alternately the system can be powered from a 12V solar panel or car battery The nominal current draw of the sensor is 330 mA at 12V A block diagram of the sensor showing the interconnect
7. a re purposed USB DVB T terrestrial digital video broadcast dongle that can be used as inexpensive radio receiver to stream downconverted and digitized I Q baseband samples to a host computer for further processing The RTL SDR dongle used in RasHAWK sensors is capable of tuning over a 24 1766 MHz range with just over a 2 MHz bandwidth Additional information on the RTL SDR can be found at http sdr osmocom org trac wiki rtl sdr Figure 7 RTL SDR USB Radio Dongle 4 1 3 Antenna Switching Subsystem The Antenna Switching Subsystem Figure 8 was designed fabricated and assembled by team members at Morgan State University The board was fabricated using a PCB milling machine in the University s RF design lab The schematic for the design is shown in Figure 9 O 2013 Geon Technologies LLC 11 LTI903 d Yolupe Rpzatane ci Res Semi Rex Semi UN CHE L 3 GNEP In Cap Semi Cap Semi Ira Let i i Cap Semi E Wan Lira a aa Lt GMD MCX 5 un is Lo ced o Poni ai e 1 Tee a aND MCK E nun E GNE pu DND ad SI PH SA SPAT 2i pin TSS GME Figure 9 Antenna Switch Schematic 2013 Geon Technologies LLC 12 GN The antenna switch uses an Analog Devices ADG904 4 1 RF mux to switch between antennas under Arduino control One design challenge was properly conditioning the supply and signaling voltages from the Arduino to be compatible with the 1 65 to 2 75V operating voltage range of
8. a switching software Dr Willie Research Professor Morgan Technical guidance on the DF subsystem Thompson State Thomas Goodman Geon Technologies LLC Software development on Raspberry Pi Raspberry Pi ARM processor 3 System Description Since the RasHAWK system architecture makes extensive use of the REDHAWK Software Defined Radio SDR framework a brief description of the REDHAWK framework is provided Much more information can be found at REDHAWK SDR FOSS website http redhawksdr org 3 1 REDHAWK in 30 Seconds maybe more REDHAWK is a free and open source software FOSS package that provides a robust architecture for distributed computing Some key REDHAWK definitions and concepts are provided below Domain A Domain can be thought of as the central controller ina REDHAWK based SDR system The Domain is responsible for launching and controlling radio applications called waveforms along with maintaining a registry called the Naming Service of all resources that are available in the system In the RasHAWK system our Command and Control C2 laptop serves as the Domain Manager orchestrating all of the operations conducted by the system As we ll see later by remotely accessing the Domain Manager we can navigate the entire system architecture and examine and control any device or software component Device A Device is a software abstraction or proxy for a piece of hardware in the system that allows us to g
9. dio C Update Sensor 2 Center Freq MHz 462 6375 IFRS Ch 7 DF O P Bandwidth Hz 256000 Audio i7 Update Sensor 3 Center Freq MHz 462 6375 FRs Ch 2 DF Y Bandwidth Hz 256000 Audio No Waveforms Active One Waveform Active Three Waveforms Active Figure 14 UI Display Updates as New Waveforms are Launched Using UI the operator has control of the following key processing parameters in the system e Center frequency and bandwidth of each sensor e FRS radio channel currently being processed by a waveform e Enabling FM demodulated audio output on the laptop soundcard e The DF function can be turned on off on a per sensor basis The user must click the Update button in order for any parameter changes to take effect 5 4 Mapping Interface The Mapping Interface utilizes standard web technologies and open source software to display sensor information in near real time without the need for additional plug ins or proprietary software packages Common HTMLS design practices are used to create an RF Common Operating Picture COP that will be supported by most modern browsers including Firefox and Chrome and on any platform supporting a browser including laptops tablet computers and smartphones HTML JavaScript and CSS are used to create a webpage based frontend UI that requires no plug ins or proprietary software only a modern browser that supports the Websockets protocols The Google Maps and
10. erminal Block Philmoree L Baynesvlle Power Supply 1 129 120 L wore bay aT ive sacer 4 039 389 SMASMTCom IL eBay X SMTSMAfemaleconnctor 1 100 100 TOTAL 16 46 5 Application Software Description The following sections describe the processing application software on the C2 laptop 9 1 Processing Waveform Description After a sensor 1s powered on and registers with the laptop Domain s Naming Service the processing waveform shown in Figure 10 is manually launched on the laptop from the REDHAWK IDE The waveform ingests data from the sensor and performs the required signal processing functions to recover the audio and determine LOB to the transmitter 2013 Geon Technologies LLC 13 Raspberry Pi GPP mS Devices running on propEvent 8 Raspberry Pi Node prt sdr device o antenna entr al M Ort sdr device 1 lantenna control 1 dataShort Out message nut p message in message ing atransmit control l gns receiver amp ltransmit control 1 amp lgps recelver 1 GPS idi Automatic connection made over WiFi when Waveform is launched Developed for RasHAWK Laptop sensoringest t TuneFilterDecimate AmFmPmBasebandDemod AudioSink e sensoringest 1 1 TuneFilterDecimate 1 AmFmPmBasebandDemod 1 AudioSink 1 1 dataFloat out dataFloat Out M am dataFloat out Jj dataShort in C dataFloat In 1 _ dataFloat In
11. et status control and data from that hardware For example a receiver Device will have software configurable control variables called Properties such O 2013 Geon Technologies LLC 2 as center frequency bandwidth gain etc that an application can set and get Setting these software properties in the Device results in the corresponding parameters being changed on the hardware In the RasHAWK system we wrote several Devices which reside on the Raspberry Pi to manage and control the hardware devices GPS RTL Receiver Antenna Controller connected to the Pi s USB and GPIO ports Node A Node 1s a collection of Devices under the control of a Device Manager The Device Manager runs on the node s host processor and starts each Device proxy in the node The Device Manager is also responsible for contacting the system s Domain Manager and registering the nodes Devices with the Naming Service In the RaSHAWK system each Raspberry P1 has its own Device Manager that contacts the C2 laptop and joins the system Domain on power up Components From the REDHAWK User s Manual A Component is a modular software building block that can be inserted into any number of signal processing applications to perform a specific and reusable function A Component is fully defined by its interfaces Properties and functionality Many of the software Components used in the RasHAWK system came with the standard installation of the REDHAWK framework Ot
12. f open source capabilities centered on the RTL USB radio dongle Secondly there is currently much interest in the REDHAWK SDR framework but unfortunately there is an absence of easily sharable applications that use REDHAWKkK in any significant way A Raspberry Pi based sensor network using the RTL SDR dongle and REDHAWK seemed a good way to learn more about the RTL dongle while providing a meaningful reference design demonstrating REDHAWK capabilities for distributed processing This report presents an overview of the system architecture followed by a detailed description of all of the main sub systems with particular emphasis on the hardware and software that comprise the Raspberry Pi sensor Since a basic knowledge of the REDHAWK framework and terminology is necessary in order to understand how it 1s applied in the sensor and system a brief REDHAWK overview is provided 2013 Geon Technologies LLC l 2 Team Composition The RasHAWK sensor development was a joint effort between Geon Technologies LLC and Morgan State University s Center of Excellence for Tactical and Advanced Communications Technologies CETACT A list of contributors including their affiliation and area of responsibility is provided in Table 1 Table 1 List of Contributors Individual Affiliation Area of Responsibility a Pannu een Student Morgan DF antenna switch analysis design State fabrication and construction Antonio Samuel Student Morgan State Antenn
13. hers such as the component that calculates Line of Bearing LOB were developed specifically for RasHAWK Waveforms Waveforms also referred to as applications are sets of interconnected Components that are launched together to perform some specific signal processing function In the RasHAWK system all of the signal processing waveforms are launched on the C2 laptop s host processor These waveforms connect to Devices in the remote Nodes in order to ingest data from the Node s receivers CORBA Common Object Request Broker Architecture CORBA 1s the middleware in REDHAWEK that enables the interconnection of Components and Devices seamlessly across a network A programmer does not need to know specifically where a Component or Device resides on the network CORBA and the Naming Service seamlessly manage this location information greatly simplifying programming on a distributed system In the RasHAWK system the C2 Laptop and each sensor Node launch their own a CORBA Object Request Broker ORB to manage data transfers within the system Events Events are an asynchronous mechanism used to disseminate status information throughout a REDHAWK system Components and devices can subscribe to event topics of interest so that they are aware of a significant change in the system such as a parameter update in another component In the RasHAWK Sensor we use events to signal changes in the antenna switching mode between the antenna control device a
14. ifferent operating environments on each processor In operation the Raspberry Pi sets the DF MODE pin high to signal the Arduino to begin antenna switching The red LED turns on when DF MODE is high The Arduino then controls the AO and A1 port select lines to the switch to achieve the desired switching pattern As it switches between antennas the Arduino outputs the switching status to the Pi on the ANT SELO 3 lines The Pi polls these pins in the antenna control Device and the switching status 1s included in the SRI that 1s sent along with the baseband data from the sensor to the C2 Laptop The antenna array is made up of four magnetic mount antennas that come with the RTL radios mounted on a steel plate extra antennas were ordered separately for this effort The antennas are separated by approximately 1 4 wavelength of the anticipated target signal frequency Since our target signal for this demonstration is the unlicensed FRS radios a nominal frequency of 462 MHz was used to calculate the 74 wavelength spacing approximately 6 4 Antenna ground radials were constructed from lawn marker flags like the ones that were marking the locations of my neighbor s sprinkler heads until recently This hopefully provides a better ground plane for the antenna array than the metal plate alone More detail on the DF technique used will be presented in a later section 4 1 1 2 Software Configuration For this effort the Raspberry P1 based sensor r
15. ing A four antenna array and RF switch was constructed to perform coarse LOB calculations to target emitters Command amp Control C2 Laptop The C2 Laptop is the main controller for the RasHAWK system It runs the REDHAWK Domain Manager and keeps track of all the sensors that are currently online via the Naming Service The waveforms which perform the signal processing for each sensor feed are launched from the REDHAWK Integrated Development Environment IDE along with spectrum and audio plots A custom User Interface was developed that permits an operator to control a minimal set of key system parameters The laptop also has a USB GPS dongle to provide its position to the mapping web server also running on the laptop Finally an iPhone is used as a WiFi hotspot to tether the laptop to the Internet for real time access to the online Google Maps server Location Mapping Server A web server application is implemented on the laptop that can connect to the running REDHAWK Domain and probe all of the running devices and components for status The mapping server polls the active sensors and laptop for their locations and plots them on a terrain map using calls to the Google Maps API The server also polls the status of the LOB components running on the laptop and overlays active LOBs on the map The map can be displayed in a web browser on any device connected to the RasHAWK WiFi network WiFi Router RasHAWK uses a TP LINK TL WR1043ND 80
16. ion of major components is shown in Figure 3 RTL Receiver Antenna Switch Figure 2 RasHAWK Sensor O 2013 Geon Technologies LLC 6 Magnetic Mount Antennas p 4 1 RF Switch RF Input RIL SDR gt O 5 Scll E DEN ES WiFi Dongle ei O UJ L S Antenna Sie 5VDC SE GPS tatus Control Converter Ge USB amp 5VDC Optional PAYI Vehicle Solar RaspberryPi Gei SS Power SD Card Linux OS Figure 3 RasHAWK Sensor Block Diagram The USB GPS receiver used is a GlobalSat Model BU353 S4 with magnet base mount The USB WiFi dongle used is a no brand Model SL 1504N 802 11N ordered on eBay It was selected mainly for its low price and impressive looking antenna A 12VDC to 5 VDC voltage converter allows the sensor to be conveniently run from a car battery if needed Each subsystem of the sensor is described in the following sections 4 1 1 Rapsberry Pi 4 1 1 1 Hardware Configuration The Raspberry Pi has a Broadcom BCM2835 system on a chip SoC which includes an single core ARMI176JZF S 700 MHz processor and 512 MB of RAM The Morgan State Antenna Switch is mounted on the outside of the unit s case An 8 MHz Arduino Micro Pro microcontroller is mounted to the Raspberry Pi P1 connector to access the Pi s GPIO pins The antenna switching is under the control of the Arduino which serves as an interface between the P1 and the antenna switch This hardware configuration 1s shown in Figure 4 A block diagra
17. led SRI Signal Related Information to the C2 laptop for processing antenna control Device The antenna control Device leverages the open WiringPi library for directly manipulating the Raspberry Pi s GPIO port This Device controls the Arduino board for relatively deterministic timing management of the antenna array switching The Device provides properties for changing the antenna switching pattern and an Event port for signaling a change in the switching pattern to the RTL SDR Device eps receiver Device The gps receiver Device provides serial bus access to the BU353 S4 USB GPS Receiver Using the libnmea library this Device translates the incoming NMEA formatted messages into a variety of fields including latitude longitude signal O 2013 Geon Technologies LLC 10 valid etc These fields are then applied to a FRONTEND GPS port ensuring future compatibility with other REDHAWK entities transmit control Device The transmit control Device also makes use of the WiringPi library for directly manipulating the Raspberry Pi s GPIO port In this case the Device drives two pins 1 enabling the transmitter output and 2 enabling the audio input on an FRS radio The state of each pin 1s controllable by the Device s properties that are then easily accessible by our control applications Note that this device 1s only used on the Node that controls the FRS radio target emitter 4 1 2 RTL SDR USB Radio Dongle The RTL SDR Figure 7 is
18. ler DF technique The next section describes this technique in detail 5 2 DF Technique Description From the beginning the RasHAWK effort had the stretch goal of performing a line of bearing from each sensor to the target emitter for determining coarse emitter location We use a modification of the Pseudo Doppler DF PDDF technique popular among ham radio fox hunters and used in some commercial DF system such as LoJack Vehicle Recovery System A notional PDDF system is shown in Figure 12 4 1 RF Switch Receiver Switch Sequencer 1 gt 2 gt 3 gt 4 repeat Neg Zero Crossings LOB Phase Detector Figure 12 Notional Pseudo Doppler DF System In this case an RF switch is used to sequence between 4 antennas in a square array with 1 4 wavelength separation based on target signal frequency The switching frequency for typical PDDF systems 1s in the 500Hz to kHz range For a planar wavefront arriving at an angle to the array each antenna receives a slightly delayed or advanced version of the signal relative to the other antennas Switching between antennas produces a phase discontinuity in the carrier sinusoid at the receiver input The step discontinuity in phase produces an impulse out of the FM demodulator These impulses are essentially sample points on a continuous sinusoid with a period equal to the time required to switch through O 2013 Geon Technologies LLC 16 all 4 antennas After so
19. ly in the following sections O 2013 Geon Technologies LLC 19 6 1 Distributed Sensor Deployment The RasHAWK sensors form a distributed sensor network connected to a central C2 Laptop node with wireless connectivity via WiF1 On power up sensors connect via WiFi automatically and register with a REDHAWK C2 node on a laptop then begin forwarding signal and GPS coordinates The sensor locations will be displayed on a satellite view map using Google Maps 6 2 Spectrum Situational Awareness and Monitoring Once the sensor network is established an operator at the C2 laptop 1s able to monitor a sensor s spectrum and listen to target audio from a selected FRS channel using the Control UI described earlier Spectrum plots and an audio waveform time domain display will be active for each sensor during the demonstration see Figure 16 6 3 Coarse Emitter Location Once a signal 1s observed the operator can command the sensors to perform a line of bearing LOB determination on the target The LOB calculations will be performed on the C2 Laptop using data forwarded by the sensors LOBs from each sensor will be displayed on the map for coarse emitter location determination via intersecting LOBs o x L dataFloat out Z3 Bm Figure 16 Spectrum and Audio Plots Displayed for Each Sensor O 2013 Geon Technologies LLC 20 7 Demonstration Plan Given that the Showcase demonstrations are indoors a full demonstration of the system will not be
20. m of the configuration is shown in Figure 5 O 2013 Geon Technologies LLC 7 Figure 4 Raspberry Pi Internal View with Arduino Kg CN D D c c c c o eb Bez c c st lt Antenna 3 Antenna 4 RF Output to RTL Receiver 4 1 RF ou 41RFSwih A1 A0 Switch Out Comms with C2 Laptop 0 O Antenna 1 O0 1 Antenna 2 p 1 1 Antenna 3 1 0 Antenna 4 Command amp Status Set Center Freq 20 21 VCC RAW GND Set Sample Rate i i Set DF Mode Arduino Micro Pro Red LED ON 2 3 4 5 RAW GND DF_MODE Enabled GPS Position DF MODE GPIO 17 Lat Lon DF MODE ANT SEL2 5V DC GND ANT_SELO ANT SEL1 ANT SELO GPIO 27 ANT SEL1 GPIO 22 ANT SEL2 GPIO 23 Data Packets BULKIO 1 43 15 146 2 36 Baseband UO Data short ints Header P1 SRI Signal Related Information Sample rate BW Gs RaspberryPi iF i Radio ID RTL SDR USB Hub Antenna switch state Figure 5 Raspberry Pi Interconnections 2013 Geon Technologies LLC 8 The Arduino was included in the sensor design so that the antenna switching times could be more deterministic than directly using the Dis GPIO lines under program control due to the non deterministic scheduling in the Pi s Linux OS The Arduino is programmed to run bare metal with no operating system which produces near deterministic switching times The configuration 1s a poor man s dual core processor with d
21. me calibration the phase difference between the sampled sinusoid and the antenna switch control signal can be mapped to the angle of arrival of the incident wavefront In a typical PDDF system the antenna switching and receiver components are co located with the FM demod and zero crossing detector making phase comparison of the switching signal and sampled sinusoid trivial In the RasHAWK system the receiver and antenna switcher are located in the remote sensor away from the FM demod and any other processing components in the laptop making exact synchronization between the switcher and FM demod output difficult Our goal is to recreate the sampled sinusoid by measuring the magnitude of impulses out of the FM demod as the antennas switch To accomplish that we have the Arduino switch back and forth between a pair of antennas for a period of time thus producing a sequence of impulses of the same amplitude The rtl sdr device in the sensor reads the state of the Arduino switching and encodes the current antenna switching pair in the SRI that is sent along with the data to the laptop The lobCalc component takes an average of the peaks it detects for each pair of antennas The result after all antenna pairs have been visited are 4 sample values of one period of the pseudo doppler sinusoid Based on the relative amplitudes of these values we can determine the coarse line of bearing of the incident signal 5 3 Control User Interface The RasHAWK Co
22. nd software components could fulfill the role of a fully capable distributed ISR or JEMSO support system O 2013 Geon Technologies LLC 21 9 Sensor Bill of Material The final Bill of Material with pricing for the RasHAWK Sensor is shown in Table 4 Table 4 RasHAWK Sensor Final Bill of Material Tem Description Part Manufacturer Source Eet 2 Hi Speed USB 2 0 4PotPoweredHub Bekin OfficeMax 2799 3 j RaspberyPi Model B 512MBRam jadafritcom 3995 146 Jadafruitcom 7 9 4 6 ebay 13 9 Extra Mag MountAntennas 1 90 ea 4 total JUNK ebay 7 6 po Lowes 8 0 11 jMiscUSBCabes 1 1 JDolerTre 4 0 L 12 4 1 RF Switch Board Morgan State various 164 x9r 3 DENN 12V to 5V DC DC Converter NEUE Misc Hardware PVC pipe metal plate etc GRAND TOTAL 192 14 O 2013 Geon Technologies LLC 22
23. nd the RTL receiver device 3 2 System Architecture An overview of the RasHAWK system architecture is shown in Figure 1 We ll introduce each major component of the system here More detailed descriptions the hardware and software for each subsystem will be presented 1n subsequent sections O 2013 Geon Technologies LLC 3 Spectrum Displays Custom User Interface enter Free Merz 452 8378 Pagine De s ee aa eins Command amp Control C2 s en Laptop Hencwidth He 88M Seren d wer Frei Mil 3562 5379 FR tie 3 BF Baparph Hr 1548006 Ao Uretat iPhone EER 3 33153 a Hotspot tether to Internet Location Mapping on Tablet REDHAWK Domain Manager Rm Ny Streaming Data l E WiFi Router SSID rashawk wlan Transmitter Node Raspberry Pi RasHawk fr with Antenna Switch Sensors e REDHAWK Device Nodes REDHAWK Device Node Figure 1 RasHAWK System Architecture O 2013 Geon Technologies LLC 4 RasHAWK Sensor The bulk of the work on this project involved development of the RasHAWK Sensors The REDHAWK core framework was ported to the ARM processor on the Raspberry Pi and several REDHAWK Devices were written to remotely control the hardware connected to the P1 Each sensor becomes a REDHAWK node that registers its capabilities with the Domain Manager on the C2 Laptop and relays position information and complex baseband data samples to the laptop for process
24. ntrol User Interface UI provides a simple menu driven operator interface for basic control of sensors in the RasHAWK network The UI is written using the pygtk python graphical user interface library and uses the REDHAWK python Application Programmer Interface API attach to a running REDHAWK Domain discover which resources are currently online and control selected devices and components on demand RasHawk by Geon Sensor 1 Center Freq MHz 462 6375 pech 2 DF M Se d Gah Bandwidth Hz 256000 Audio 0 Sensor 2 Center Freq MHz 462 6375 prs ch 7 X zl Bandwidth Hz 256000 Audio ivi Sensor 3 Center Freq MHz 462 6375 prcch 2 DF F SS 1l Ze Bandwidth Hz 256000 Audio Update Figure 13 RasHAWK Control UI 2013 Geon Technologies LLC 17 When the UI is first launched it attaches to the running REDHAWK Domain and searches for active waveforms every 5 seconds If no waveforms are active then no control entries are displayed on the UI As new waveforms are launched by the REDHAWK IDE in our case the control entries are displayed for the new waveform This sequence is illustrated in Figure 14 As waveforms are released destroyed the corresponding entries are deleted from the UI RasHawk by Geon Sensor 1 Center Freq MHz 462 6375 epsch 2 DF O Center Freq MHz 462 6375 EFRS ch 2 2 DF V Bandwidth Hz 200000 Audio Bandwidth Hz 256000 Au
25. rate of 256 kHz in order to provide sufficient bandwidth to cover FRS Channels 1 to 7 This gives us a baseband tuning bandwidth of 128 kHz The channel spacing for FRS radios 1s 25 kHz so the baseband tuning offset for FRS channels to 7 is shown Figure 11 RF Frequency iod s d MHz a set uw 462 5625 75 000 2 462 5875 50 000 3 462 6125 25 000 s ners a FRS Radio Channels 1 7 1 2 3 4 5 6 T D D D AB AB D D AB AB O O O O O O O O O N N N N N N N N NS RF MHz on CO D D Q O N Q2 OH Oo CA OH Co Q2 N N N N N N N N N o Or c on o o c on o Baseband KHz N N N oe Ol e Oi o C e Oi oo 256 kHz Complex Baseband Bandwidth Figure 11 FRS Radio Channel Allocation and Baseband Tuning Offsets O 2013 Geon Technologies LLC 15 AmFmPmBasebandDemod A stock REDHAWK component that ingests complex baseband data and outputs real demodulated samples We only utilize the FM demodulation capability AudioSink An existing component that ingests audio data samples from the FM demodulator output and plays the audio on the laptop soundcard Downloaded from the Axios Engineering Git repository lobCalc Developed specifically for the RasHAWK application this component ingests FM demodulated data and performs the line of bearing calculation using a variation on the Pseudo Dopp
26. rting spectrum monitoring signal intercept and direction finding DF operations All of these are fundamental capabilities of any ISR and EW system For our AOC Tech Challenge demonstration several RasHAWK sensors are deployed in a distributed sensor grid wirelessly tethered to a command and control C2 laptop The system has the following key features and capabilities e Asimple operator interface to configure the sensors e Falling raster and PSD displays to monitor the spectrum for signal activity e Demodulate FM signals from target FRS radios and play audio on selected channels e Perform coarse DF on target emitters e Display a map of the surrounding terrain that is annotated with the positions of the sensors the target emitter and calculated lines of bearing LOB to the target The map provides a RF Common Operating Picture COP with can be viewed on WiFi enabled tablets or smartphones This effort was made feasible by leveraging the existing capabilities of the open source REDHAWkK software defined radio SDR framework In addition to its inherent networked processing capabilities REDHAWK provided a common software development framework that allowed a far flung team to independently develop and test portions of the system software then relatively easily integrate their contributions into the final system The motivation for this particular implementation was twofold First it grew out of a curiosity around the growing body o
27. the ADG904 This was done using a Linear Technologies LT1965 voltage regulator to convert the 5 V Arduino supply voltage to the nominal 2 5V required by the switch A Texas Instruments TXB0104 level translator was used to convert the 3 3V Arduino control signals to 2 5V RF characterization measurements conducted at the Morgan State RF Lab for the completed switch board are shown in Table 2 Table 2 Characterization of the Antenna Switch PCB In ertonnLo Of Isolaton Remum Loss KF Port eg g Port to Port Isolation dB Condition dB dB dB RFI1 RF 40 05 RFI RF3 AN Al VDD 2 5V_Fs A6 RFl 0 53 44 60 0 6f FLRF4 4D5 MHz RF2 RF1 44 95 RF2 RF3 46 1 VDD 25V Frs 462 RF 0 53 44 08 20 741 RF RF4 36 88 MHz I RF3i RFl 39 52 RF3 RF2 41598 VWDD 2 5V F 461 ES em Tum 70689 REXKRF4 43 21 MHz RF4 0 41 439 30 058 EE ARES 35 M RF4 RFi 39 76 nes 3V Fs 462 RF4 RF3 45 68 Hz A bill of materials for the antenna switch 1s provided in Table 3 The use of the Antenna Switch to perform the Pseudo Doppler DF technique will be discussed in Section 5 2 Table 3 Antenna Switch Bill of Material V3 Switch Board Part List Per Board Component Manufacturer Vendor Description Quantity Unit Extended 3738 378 ee M RO4003C Board Material DK 3 38 0 05 Diel Dimension 12 x9 Rogers Corporation Rogers Corp Thickness 16 7 mils TC 99 90 Copper 0 502 sqft PCB T
28. uns the Raspbian distribution of the Linux Operating System OS The REDHAWK core framework was ported to this Linux distribution so that the Pi could act as a REDHAWK node and run the REDHAWK Device Manager Four new REDHAWK Devices were written to support the hardware in the RaaHAWK sensor rtl sdr device gps receiver antenna control and transmit control A new raspberry pi node configuration that includes these devices was also created The REDHAWK IDE graphical view of the raspberry pi node is shown in Figure 6 O 2013 Geon Technologies LLC 9 ii GPP 21GPP 1 propEvent g rtl sdr device Ej antenna control La rtlsdr_ slrtl sdr device 1 4 antenna control 1 dataShort Out g message out A gj transmit control Gi gps receiver a transmit control 1 lgps receiver 1 GPS idl Figure 6 raspberry pi Node and its Devices Each new device developed for the RasHAWK Sensor is described below rtl sdr device Device The rtl sdr device is a REDHAWK wrapper for the freely available librtlsdr library The RTL Device s properties provide RasHAWK with direct access to altering the center frequency sampling rate tuner gains etc associated with this inexpensive SDR receiver The Device provides a property event port for indicating when its hardware settings change and a messaging port to receive the switching pattern from the Antenna Control Device Finally it has a output data port for sending the received baseband data and metadata cal
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