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Software Defined Radio
Approach to Distance
Measurement Equipment
PLANS 2014May 7, 2014
May 7, 2014 PLANS 2014 1
Omar Yeste and René Jr. Landry
May 7, 2014 PLANS 2014 2
Outline
1. Introduction
2. Phase I: Design and simulation
3. Phase II: SDR implementation
4. Phase III: Embedded SDR
5. Results
6. Conclusion
1. Introduction
Benefits of SDR for aviation
• Minimization of SWaP-C requirements
– GHG emissions reduction
– Design, development and installation time and cost
– Maintenance, repair and modernization time and cost
• Reprogrammability & reconfigurability
• Scalability
• Reduced number of parts
– Increased reliability
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May 7, 2014 PLANS 2014 4
1. Introduction
Context of the work
AVIO-505 project
• “Software defined radios for highly integrated system architecture”
• Objectives:
– Integration of navigation, communication and surveillance systems under a single universal reconfigurable platform
– Demonstrate the capabilities and performance of SDR in aerospace
– Address new regulatory initiatives (NextGen)
• Partners:
– Academic: ETS Montreal, Ecole Polytechnique Montreal, UQAM
– Industrial: Bombardier, MDA, Marinvent Corporation, Nutaq
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1. Introduction
DME principle of working
1. Introduction
DME’s current status
• Developed in the 50’s
• Fully deployed and operative worldwide
• Federal Radionavigation Plan proposes
DME/DME/IRU as an APNT system
(backup to GNSS)
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1. Introduction
Objective of the work
• Proof of concept:
DME/N implementation into low cost SDR
• Work methodology
– Phase I: Design and simulation
– Phase II: SDR implementation
– Phase III: Embedded SDR
• Initial operability
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2. Phase I: Design and simulation
Idealized simulation environment
1. Complex baseband equivalent input and output
a) Required by hardware
b) Bandwidth reduced for simulation
2. Arbitrary sampling frequency
a) Computational load control
b) Hardware platform independent
3. ADC/DAC resolution
a) Numerical computation issues
b) Generated code compatibility with subsequent phases
4. I/O buffer used for interconnection
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2. Phase I: Design and simulation
Design constraints
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3. Phase II: SDR implementation
GNU Radio SDK
• GNU Radio blocks coded in C++
– Starting point: C++ code generated by Simulink
• Control logic can be added to the executable python code
– Channel selection, calibration step, displaying results, automatic gain control,
(DME/DME PNT computation)
– Dynamic reconfigurability (DME, XPDR, GNSS, etc.)
• Auto-calibrated DME
– Compensation for internal round-trip paths between GPP and antenna (replies
are received after the 2.53 ms window)
– Variable delay
– Pulse pairs transmitted and received at the same frequency (Mode X)
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3. Phase II: SDR implementation
GNU Radio SDK
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3. Phase II: SDR implementation
DME flowchart
• Main components:
– Radio420X: High quality radio module
– Xilinx Zynq FPGA (pass-through mode)
– Dual ARM Cortex-A9
• Features
– Remote and embedded
operation
– GNU Radio support
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3. Phase II: SDR implementation
Nutaq’s ZeptoSDR
RF range:Low band 300-1600 MHz
High band 1500-3800 MHz
PLL setting time 20 µs
Wideband noise floor:Receiver -100 dBc/Hz
Transmitter -124 dBc/Hz
Gain control
Receiver (low band) 79 dB
Receiver (high band) 73 dB
Transmitter 70 dB
Maximum input power -13 dBm
IMD3
Receiver (low band) -61 to -56 dBc
Receiver (high band) -50 to -45 dBc
Transmitter -60 dBc
P1dB outputLow band 20 dBm
High band 15 dBm
Carrier suppression -50 dBc
Side band suppression -45 dBc
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3. Phase II: SDR implementation
Radio420X
Most attractive features:
• High dynamic margin
• Rapid PLL setting time
• Dual ARM Cortex-A9 running Linux Linaro
– GNU Radio compatible
– Only data interface changes (from Ethernet to AXI)
• Computational load
– Optimization of the tasks performed
– IRQ / CPU core usage management to avoid
synchronism loss
– Maximum sampling rate limited to 2 MHz
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4. Phase III: Embedded SDR
Seamless transition
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5. Results
Waveform and spectrum
• No spurious signal
appreciated
• Spectrum mask
respected
• Meets all DO-189
waveform
requirements
May 7, 2014 PLANS 2014 17
5. Results
Bench top setup
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5. Results
Accuracy
Note: IFR-6000’s nominal accuracy ±0.01 nmi (±18.52 m)
Sensitivity:
-85 dBm
Dynamic margin:
70 dB
Maximum output peak
power:
20 dBm
Conclusion
• Feasibility of SDR approach to DME has been
demonstrated in lab
• Design and implementation processes dramatically
accelerated
• Development in three phases:simulation → real time → embedded system
• Design “aware” of subsequent phases optimizes
development time and allows almost seamless
transition
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Future work
• Extensive laboratory testing
– 1st flight test this fall
• Phase IV: Hybrid FPGA-GPP implementation
– Latencies are not compliant with other avionics systems’
requirements
– On-the-fly reconfigurability
• DME/DME navigation using a single radio
– Sequential ground station interrogation and tracking
– Interleave interrogations for simultaneous tracking
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Questions?
Special thanks to our industrial partners
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Contact us: [email protected], [email protected]
