Off Grid Interconnected Devices. Rick Campbell Portland State University

Transcription

1 Off Grid Interconnected Devices Rick Campbell Portland State University

2 SV Kwai Departed Hawaii last Friday Oct 24 Due Kiritimati Island ~ Nov 1-5 svkwai.com

3 This Talk: What is Off Grid? What is are Interconnected Devices? Why are they worth our time? An interesting example......with some engineering details

4 What is Off Grid? A: No power grid harvest your own power conserve energy B: No Internet infrastructure RI Real Intelligence Simple and elegant

5 What are Interconnected Devices A: Information transfer without wires either long distance or mechanical challenges B: Intelligent bandwidth how much information? I m OK mom once a day

6 Why are they worth our time? A: The solutions are not in the textbooks forces creativity and invention B: The solutions are not in the textbooks extra-curricular education C: The solutions are not in the textbooks no academic limitations

7 Let s Go! Shut the textbook open the notebook and start sketching...think DaVinci or Bach

8 A Classic Problem Far Off Grid Kon-Tiki status, position operator skill

9 Path Length 10,000 km Bounce signals off Ionosphere Ionospheric weather dependent: like sailing and solar energy it doesn t work every day......but when it works, it s good

10 Experimental Data for 10,000 km path 1. US and Russian Navy MHz beacon transmitters 2. A million Radio Amateurs 100 watts SSB Voice Communication Wire antennas Ionospheric science

11 Some basic engineering: SSB voice bandwidth 2.5 khz Our information 100 bits PER DAY! Minimum bandwidth set by path We did some experiments amateur station K7XNK coherent integration time at MHz approximately 4 seconds

12 More basic math: SSB bandwidth 2.5 khz Our bandwidth 250 millihertz we need 40 db less transmit power for similar reliability 40 db less than 100 watts = 10 mw about the same as a dim LED

13 Wait...so you are claiming that you can transmit data around the world without wires using less power than a flashlight? Yes...theoretically...and that s good because solar yard lights operate off-grid with a little solar panel and storage battery.

14 But this is not the: Microwave Theory Society We use the whole scientific method, not just the theory part. We design and build the hardware and do the experiments. Engineers are judged not by what they can think, but by what they can do.

15 After a 30-year flirtation with virtual everything, the engineering world has rediscovered: Hardware is Hard

16 We make it possible by dividing hardware requirements into smaller blocks. Antennas Radio Power supply Package MTT talk, so we ll focus on the radio...

17 ...and limited time so we ll focus on a receiver......which is harder than the transmitter... Requirements: -204 dbw noise floor 9v at < 10 ma dc power good dynamic range

18 Receiver Block Diagram filter mixer filter amplifier weak RF signal millivolt baseband signal local oscillator

19 Generate a sine wave--local oscillator Oscillator Select individual weak signal at receiver Filters Convert received frequency to baseband Mixer Amplify zeptowatt level received signals Amplifiers

20 ... The most basic radio: k + 100u 1k:8 audio 100n 560n 4.7k 47k 560p k k 39 1N4148 1N n 3.9mH 680n 560n 100n 10k u Improved MicroR1 from p 8.4 EMRFD Note: select crystal and DTC for frequency range of interest minimalist Vladivostok receiver

21 Filters Oscillator Mixer Amplifier

22 By independently designing and building each piece, we progress from minimalist to lab-grade receiver performance Oscillator v 3 ma 16 MHz crystal 10k C1 10k N k 4.7 v zener 2N u 100n 8t trifilar FT t T C1 optional VXO capacitor MHz +2 dbm...and spinoff reference designs.

23 Oscillator PSU/Handbook oscillator/multiplier 4 second integration time at MHz requires better than one part in ten to the seventh frequency stability...

24 Frequency Stable Oscillator packing foam and diecast box

25 Filters Front-End Crystal Filter

26 Mixer baseband I RF RF 0 0 LO 90 0 Q 2009 mixer

27 Mixer Research and Development 2009 bench experiment

28 Mixer Research and Development 2013 serious R&D I Q mixer

29 Mixer Research and Development Continued effort in 2014

30 Amplifiers 10 MHz amplifier baseband amplifier analog signal processor

31 Instrumentation lab receiver circa 2009 works great, but 12 v at 60 ma supply

32 2014 4mA at 9v analog signal processor With 4mA LO, meets 9v at <10mA spec

33 Instrumentation lab receiver circa 2009 Rule: Don t wait for new hardware to do good science with old hardware.

34 Instrumentation lab receiver circa 2009 dipole antenna baseband FFT analyzer MHz receiver with 1 Hz stability

35 Waterfall plot showing 35 mw Hillsboro signal received in Seattle 20 minutes AE7XA Hillsboro 400 Hz

36 Higher frequency hardware looks different: 1.3 GHz 23cm wavelength RF stages note resonators with Q=1000

37 Instrumentation IF transmitter-receiver circa System stability is 1 part in 10

38 That s enough for one day... Concluding thoughts:

39 Off-Grid, No Textbooks, No Infrastructure Real Intelligence, Evolve the hardware, Respect the Math and Physics, Generate and Conserve power...

40 Thanks! These slides are at: