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Narrowband RF Receiver For use by the Illinois Natural History Survey

Narrowband RF Receiver For use by the Illinois Natural History Survey. Graham Alvey Noah Hughes Yi Zhang TA: Han Seok Kim. Outline. What we did and why Receiver specifications Stage by stage analysis Complete circuit results Conclusions. Project Motivations.

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Narrowband RF Receiver For use by the Illinois Natural History Survey

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  1. Narrowband RF ReceiverFor use by the Illinois Natural History Survey Graham AlveyNoah HughesYi ZhangTA: Han Seok Kim

  2. Outline • What we did and why • Receiver specifications • Stage by stage analysis • Complete circuit results • Conclusions

  3. Project Motivations • Design and construct a radio frequency receiver • Detect continuous wave pulses from electronic beacons tagged to wildlife • Help wildlife studies and surveys become more efficient at detection with eventual large autonomous network Image courtesy of Ronald Larkin: http://nhsbig.inhs.uiuc.edu/~rlarkin/DBI.html

  4. Receiver Specifications • Electronic beacon center frequency: 302  2.5 MHz(Adjacent tags separated by only 1 kHz) • Expected -145 dBm power level of incoming signal with a lot of noise • 5 kHz passband window • 1 kHz tuning resolution • Less strict specifications • Inexpensive (allow for cheap duplication for each antenna in network) • Low power (self sustaining towers with solar/wind)

  5. Original Design Block Diagram • Pre-Amplifier & Pre-Selector filter • Image Reduction Filter • Mixing/Filter/Amplifier Stage #1 (302  2MHz  45MHz) • MC13135 FM receiver chip Why not this design?

  6. BFO Final Design Block Diagram • Pre-Amplifier • Mixing/Filter/Amplifier Stage #1 (302  2MHz  60.7MHz) • Mixing/Filter/Amplifier Stage #2 (60.7MHz  10.7MHz) • Mixing/Filter/Amplifier Stage #3 (10.7MHz  455kHz) • Beat Frequency Oscillator (BFO)

  7. Preamplifier • Based on amateur radio moonbounce preamplifier • Amplify and coarse filter weak low level signal 302  2MHz • High power gain • Low noise figure • Still needs refinement

  8. Preamplifier Features 50Ω Matching Gain and Pass band • 3 chambers separated by copper foil • Input • Output • Bias circuit • Mitsubishi Gallium-Arsenide FET MGF1302 • Similar GaAs FET may get better gain and noise figure

  9. Preamplifier Verification 302 MHzGain: ~20 dB Input: -40dBm 302 MHz • Network Analyzer to measure the gain and passband • Noise Figure Meter to measure the noise figure. • Enclosure extremely helpful • Without enclosure: Gain = 14 dB, Noise figure = 3dB • With enclosure: Gain 20 dB, Noise figure = 0.3 dB • Conductive foam helps reduce feed back by absorbing oscillations

  10. 60.7 MHz IF Strip Features • Tunable 241  2MHz LO Frequency • Eventually realized with DDS, improved by HPF (should be BPF) • Elliptical band pass filter • Passband of 55-67 MHz, matched to 50Ω • MAR-2 Amplifiers • Sufficient gain, low power consumption, available in the parts shop

  11. 60.7 MHz Component Validation 60.7 MHz-.704 dB 155 MHz-3.3 dB 240 MHz-.3 dB 120 MHz-20.3 dB 46.6 MHz-20.7 dB 78 MHz-20.7 dB Chebyshev Filter Passband Elliptical Filter Passband • Elliptical 60.7 MHz filter • Check passband and passband & stopband attenuation • Chebyshev Filter for LO • Check passes 241MHz and attenuation of DDS leakage (120 MHz). Filter should be BPF rather than HPF. • Amplifier circuit: Verify gain • Mixer: Check proper functioning, acceptable attenuation

  12. 60.7 MHz 60.7 MHzGain: 34 dB 241 MHz Unwanted 241 MHz Harmonics 60.7 MHz Module Validation Expand frequency axis  • Correct Pass band: • Use Vector Signal Analyzer to verify transmission • Appropriate Gain: • Use Vector Signal Analyzer to measure the total gain of the system at 60.7 MHz and compare to the theoretical value • Low-Noise Level: • Use Vector Signal Analyzer to check the output for spurious signals in the system. Input: -60 dBm 302 MHz, LO: 7 dBm 241.3 MHz

  13. 50 MHz Oscillator 50MHzStrength: ~15dBm DampedHarmonics • Fox H5C-2E 50 MHz oscillator (erratic behavior) • Match to 50Ω • Since active, use VSA and maximize output power • Turned out to be matched already • Low pass filter to improve spurious response • Crystal oscillator would probably be better (less erratic), but no 50 MHz crystals on hand

  14. 10.7 MHz IF Strip Features • Chose 10.7 MHz • Industry standard IF frequency, many choices available. • ECS Crystal filter • Narrow pass band (7.5 kHz) to decrease noise through. • MAR-1 & MAR-2 Amplifiers • Low power consumption for amount of gain, both available in parts shop

  15. 10.7 MHz Span: ~ 8kHz 10.7 MHz Component Validation 3 dB Bandwidth of Filter, and Signal Gain measurements • Match filter impedance using low pass L-network • Use Network Analyzer to match input and output ports to 50Ω at 10.7 MHz. • 10.7 MHz Crystal Filter: • Pass band & stop band attenuation and pass band checked using Network Analyzer. • Amplifier circuit: Verify gain • Mixer: Check proper functioning, acceptable attenuation

  16. 10.7 MHz Module Validation 10.7 MHz Gain: ~42 dBm 50 MHz Oscillator leak Input: -60 dBm 60.7 MHz, LO: 7 dBm 50 MHz • Correct Pass band: Use Network Analyzer to measure transmission from one port to the other. • Appropriate Gain: Use Network Analyzer to measure the total gain of the system and compare to the theoretical value. • Low-Noise Level: Use Vector Signal Analyzer to check the output for spurious signals in the system.

  17. 10.245 MHz Oscillator • Designed this circuit second, in conjunction with 10.7 MHz circuit to ensure correct drop down to 455 kHz. • Chose 10.245 MHz because industry standard between 10.7 MHz and 455 kHz  established image rejection

  18. 10.245 MHz Oscillator Validation 10.245 MHz Unwanted Harmonics • Use Frequency Counter to validate oscillator output at 10.245 MHz. • Match impedance to 50Ω. • Since active circuit, cannot use Network analyzer for matching • Use Vector Signal Analyzer. • Adjust matching network to achieve highest output power. • After best match achieved, power out (~ -3.5 dBm) not enough for input to mixer (~7 dBm). • Add amplifier stage. • Finally achieved ~5 dBm output. Close enough.

  19. 455 kHz Circuit • First circuit constructed • Very important to final performance • Make filter selection, then amplifiers. • TOKO Bandpass Ceramic filter: 455 kHz (industry standard), narrow pass band (4 kHz), inexpensive, small size • MAR-1 Amplifiers: Low power consumption per gain, available in parts shop.

  20. 455 kHz Circuit Validation 455 kHz Span: ~ 6kHz Network Analyzer: 20dB Bandwidth and Gain • Match filter impedance to 50Ω at input and output using low-pass L-network • Use Network Analyzer to match reflections at ports to 50Ω at 455 kHz • Individual component attributes • Filter: Use Network Analyzer to test Pass band & stop band attenuation. • Amplifier circuit: Check gain using Network Analyzer. • Mixer: Insertion attenuation measured using Vector Signal Analyzer.

  21. 455kHz Circuit Validation 455kHz Gain: ~22dBm Input: -60 dBm 10.7 MHz, LO: 5 dBm 10.245 MHz • Module Testing • Correct Pass band: Use Network Analyzer to measure transmission from one port to the other. • Appropriate Gain: Use Network Analyzer to measure the total gain of the system and compare to the theoretical value. • Low-Noise Level: Use Vector Signal Analyzer to check the output for spurious signals in the system.

  22. BFO Complete Circuit • Combination of Modules: • All modules are connected via N-type or coaxial connections. • 10.245MHz oscillator connected to 455kHz stage, 50MHz oscillator connected to 10.7MHz stage, signal generator as tuning LO • Signal generator simulating weak transmitter signal

  23. Testing of Complete Circuit 455kHz Input: -136dBm 302MHz without preamp • Total Gain: ~ 103dBm • Complete circuit powered and receiving a signal from signal generator. Compare gain from input signal to output signal using Vector Signal Analyzer setup. • Spurious Signal Amplification / Elimination • Complete circuit setup combined with signal generator and Vector Signal Analyzer. Spurious signal generation is observed as the generated signal gain is varied. • Total Power Consumption = 3.66W (without BFO) • 12V modules: 3.42W, 5V module: 0.2W, 3.3V module: 0.04W

  24. 60.7 IF Strip 10.7 MHz IF Strip 455 kHz IF Strip Preamp 50 MHz Oscillator 10.245 MHz Oscillator Real-time Receiver Output Complete Circuit (without biasing or interconnects) Transmitter Pulse Output

  25. Cost Summary

  26. Future Work • Remove oscillations in 60.7 MHz and 10.7 MHz IF strips • Ensure reliable operation in weather • Obtain and code the DDS chip for the tunable local oscillator • Make the BFO • Transfer to a well designed PCB

  27. Acknowledgements and Thanks • Han Seok Kim for his invaluable advice, his time, giving us parts galore, loaning us the ECE 353 Course Notes, teaching us how to use testing equipment, and more • Ron Larkin and Ben Kamen for the project idea, and letting us climb the antenna tower • Professor Franke for his ECE 353 Course Notes, without which we would have been at a loss • Professor George Swenson for his initial ideas at our design review • Professor Gary Swenson for running such an eye-opening course

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