Analog Optical Links for Wide Bandwidth Radar Receivers Sean Morris & Brian Potts MQP Presentation Group 33 14 October 29 This work was sponsored by the Space and Missile Systems Center, under Air Force Contract No. FA8721-5-C-2. The opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government. Approved for public release; distribution is unlimited. MQP Presentation-1
Motivation Replace coaxial transmission line in radar receiver with analog optical link to: Receive full bandwidth signal at the control center Improve accessibility of receiver hardware Allow remoting of radar back-end hardware Example instrumentation radar system MQP Presentation-2
Goals & Objectives Goal Determine feasibility of using an analog optical link for transmission of a received radar signal Objectives Conduct a cost-benefit analysis of coaxial cable vs. analog optical links Create tools that model the performance of the receiver side of a radar system Become familiar with a commercial analog optical link Determine if a design can be realized with a currently available commercial analog optical link MQP Presentation-3
Technical Overview Receiver Side of Radar System Antenna In LNA Receiver Output to ADC Front-End Loss Cable Loss =Attenuation Analog Optical Link Source: C. H. Cox, Analog Optic Links: Theory and Practice. Cambridge, UK: Cambridge University Press, 24, pp. 288. MQP Presentation-4
Specifications to Meet Instantaneous Dynamic Range (5 db) Saturation Noise Figure Dynamic Range MQP Presentation-5
Specifications to Meet Instantaneous Dynamic Range (5 db) Saturation Noise Figure Sensitivity (3 db signal-to-noise ratio (SNR) for 1m 2 target at distance of 1 km) Noise Figure A B B A MQP Presentation-6
Coax vs. Analog Optical Links Performance Analysis Attenuation Source: C. H. Cox, Analog Optic Links: Theory and Practice. Cambridge, UK: Cambridge University Press, 24, pp. 288. MQP Presentation-7
Attenuation (db) Relative Attenuation (db) Coax vs. Analog Optical Links Performance Analysis Attenuation Coax Attenuation Slope 12 1 8 6 4 2 Attenuation of Coaxial Cable vs. Frequency for Varying Lengths ft. 1 ft. 2 ft. 3 ft. 4 ft. 5 ft. 6 ft. 7 ft. 8 ft. 9 ft. 1 ft. 6 5 4 3 2 1 Relative Attenuation of Coaxial Cable vs. Frequency for Varying Lengths ft. 1 ft. 2 ft. 3 ft. 4 ft. 5 ft. 6 ft. 7 ft. 8 ft. 9 ft. 1 ft. 9.5 1 1.5 Frequency (GHz) 9.5 1 1.5 Frequency (GHz) *Approximation of data provided by IW Microwave for IW486 Cable MQP Presentation-8 *Approximation of data provided by IW Microwave for IW486 Cable
Noise Figure of Link (db) Coax vs. Analog Optical Links Performance Analysis Attenuation Coax Attenuation Slope Noise Temperature 3 25 725 576 457 48 576 Overall Noise Temperature of Receiver (K) 3625 2295 725 912 1445 9125 23 Coax MITEQ LBL-1M4P5G Analog Optical Link MITEQ SCML-1M11G Analog Optical Link 363 2 457 48 343 457 576 3625 23 15 324 343 363 48 725 912 1445 2295 9125 363 1 48 343 324 457 576 3625 36.5 324 363 343 48 725 912 2295 1445 5-2 -15-1 -5 5 1 15 2 MQP Presentation-9 Gain of Link (db)
Noise Figure of Link (db) Coax vs. Analog Optical Links Performance Analysis Attenuation Coax Attenuation Slope Noise Temperature 3 25 29 3 SNR (db) for 1 m 2 target at a distance of 1 km versus noise temperature 31 29 3 28 26 24 22 14 Coax MITEQ LBL-1M4P5G Analog Optical Link MITEQ SCML-1M11G Analog Optical Link 31.5 18 32 29 28 26 2 31 31.5 32.25 31 3 22 14 24 15 32.5 32.25 32 31.5 18 32 28 26 1 31.5 32.25 32.5 32.74 32.5 32.25 32 31 29 3 31.5 24 22 5-2 -15-1 -5 5 1 15 2 MQP Presentation-1 Gain of Link (db)
Cost ($) Coax vs. Analog Optical Links Performance Analysis Attenuation Coax Attenuation Slope Noise Temperature Economic Analysis 3 Cost vs. Distance for Coaxial and Analog Optical Link 25 2 15 1 IW 486 Coax with Equalizers and Amplifiers SCML-1M11G Analog Optical Link & Tyco 166495-5 Fiber 5 2 4 6 8 1 Distance (ft.) MQP Presentation-11
dbm Voltage (V) Modeling Antenna In Front-End Loss LNA Cable Loss Receiver >> RadarReceiver Signal Setup: Frequency of Main Signal (GHz): 1 Average Power of Main Signal (dbm): -19 System Bandwidth (GHz): 1 Plot signal and amplitude spectrum of initial signal?(y/n): y Output to ADC =Attenuation 1 Initial Signal.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum of Initial Signal -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-12
dbm Voltage (V) Modeling Antenna In Front-End Loss LNA Cable Loss Receiver Front-End Parameters Gain of Front-End (db): -1 Noise Figure of Front-End (db): 1 System Bandwidth (GHz): 1 Plot signal and amplitude spectrum of current signal?(y/n): y Output to ADC =Attenuation 1 Signal after Front-End Losses.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum After Front-End Losses -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-13
dbm Voltage (V) Modeling Antenna In Front-End Loss LNA Cable Loss Receiver LNA Parameters Gain of LNA (db): 3 Output P1dB of LNA (dbm): 1 Noise Figure of LNA (db): 2 System Bandwidth (GHz): 1 Plot signal and amplitude spectrum of current signal?(y/n): y Output to ADC =Attenuation 1 Signal after LNA.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum After LNA -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-14
dbm Voltage (V) Modeling Antenna In Front-End Loss LNA Cable Loss Specify Type of Link 1) Coaxial 2) Analog Optical (Component Level - External Modulation) 3) Analog Optical (Component Level - Direct Modulation) 4) Analog Optical (Link Level) Enter #: 4 Receiver Output to ADC =Attenuation 1 Signal after Link.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum After Link -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-15
dbm Voltage (V) Modeling Antenna In LNA Receiver Output to ADC Front-End Loss Cable Loss =Attenuation Analog Optical Link Parameters Attenuation Before Link Gain (db): -24 Noise Figure (db): 24 1 Signal after Link.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum After Link -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-16
dbm Voltage (V) Modeling Antenna In LNA Receiver Output to ADC Front-End Loss Cable Loss =Attenuation Link Gain (db): 18 Output P1dB (dbm): 4 Noise Figure (db): 2 1 Signal after Link.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum After Link -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-17
dbm Voltage (V) Modeling Antenna In Front-End Loss LNA Cable Loss Receiver Attenuation After Link Gain (db): -4 Noise Figure (db): 4 System Bandwidth (GHz): 1 Plot signal and amplitude spectrum of current signal?(y/n): y Output to ADC =Attenuation 1 Signal after Link.5 -.5-1.5 1 1.5 2 2.5 x 1-9 2-2 -4-6 -8 Time (s) Single-Sided Amplitude Spectrum After Link -1 9.5 9.6 9.7 9.8 9.9 1 1.1 1.2 1.3 1.4 1.5 Frequency (GHz) MQP Presentation-18
dbm Voltage (V) Modeling Antenna In Front-End Loss LNA Cable Loss RCVR Parameters Gain of RCVR (db): 1 Output P1dB of RCVR (dbm): 1 Noise Figure of RCVR (db): 7 Output Frequency of RCVR (MHz): 7 System Bandwidth (MHz): 2 Plot signal and amplitude spectrum of final signal?(y/n): y Receiver Output to ADC =Attenuation 1 Final Signal.5 -.5-1.5 1 1.5 2 2.5 3 3.5 Time (s) x 1-7 2-2 -4-6 -8 Single-Sided Amplitude Spectrum of Final Signal -1 6 62 64 66 68 7 72 74 76 78 8 Frequency (MHz) MQP Presentation-19
Modeling Direct Modulation Analog Optical Link Parameters: Relative intensity noise (RIN) of transmitter (-15 db/hz) Laser slope efficiency (.15 W/A) Laser bias current (.7 A) Laser threshold current (.12 A) Fiber attenuation ( db/km) Length of fiber ( km) Other excess losses including coupling losses ( db) Photodiode responsivity (.85 A/W) Component Parameter Expected Value LBL-1M4P5G Analog Optical Link with no external circuitry and negligible fiber loss Simulated Value Gain (db) -22 to -23 17.9 Noise Figure (db) 45 to 5 43.2 MQP Presentation-2
Modeling External Modulation Analog Optical Link Parameters: Total excess modulator loss (4 db) V π (5.5 V) DC bias voltage of modulator (2.75 V) Optical output power from CW laser (.1 W) Fiber attenuation ( db/km) Length of fiber ( km) Photodiode responsivity (.5 A/W) Component Parameter Expected Value Mach-Zehnder Modulated Analog Optical Link with no external circuitry and negligible fiber loss Simulated Value Gain (db) 34 31 Noise Figure (db) 49 4 Output P1dB (dbm) 17 16.1 MQP Presentation-21
Testing MITEQ LBL-1M4P5G Analog Optical Link RF Signal Agilent Technologies E8363B Network Analyzer RF Signal Analog Optical Link Fiber Optic Transmitter Optical Fiber Fiber Optic Receiver MQP Presentation-22
Amplitude (db) Testing 2 15 5 m long fiber 2 m long fiber Difference in attenuation slope between two fibers 1 5-5 1 7 1 8 1 9 Frequency (Hz) MQP Presentation-23
Conclusions Using MITEQ SCML-1M11G analog optical link dynamic range specification is met, sensitivity specification is not To meet sensitivity, link must have lower gain or lower noise figure By adjusting component parameters a link can be built to meet both dynamic range and sensitivity specifications Improvement in performance for analog optical link over coaxial cable only occurs once a certain distance is reached Analog Optical Link is only cost-effective for long distances (greater than 3 ft) MQP Presentation-24
Acknowledgements Professor Alexander Emanuel Jeffrey Hargreaves Paul Juodawlkis MITEQ Inc. MQP Presentation-25
Questions MQP Presentation-26