How do you build a 1U Cube-Sat Linear transponder using SDR / DSP technology with limited Power?
Requirements:
Satellite requirements.
- Linear Transponder 70cm (437Mhz) up-link and S band (2.4GHz or 1.2Ghz down) Down-link (Bandwidth ? 250Khz on 70cm ?)
- Satellite Low Earth orbit (LEO) altitude between 650 kilometers. We need this so we can calculate path loss and RF power and antenna gain requirements.
- Available Power 1.5W for transponder from Solar panels and battery system.
- Telemetry mode? CW / AX25 / AFSK 9k6 /....
- UHF Beacon recomendation.
- UHF Beacon interval: about 55 seconds
- UHF Transmit power: ~ 1 W
- AFSK AX25 1k2 and fallback of CW 10WP
- Satellite antennas for 70cm ? and (Polarization ?)
- Satellite antennas for 2.4Ghz / 1.2Ghz and (Polarization ?)
- Telemetry Requirements ? (ID, Temperature, Power in, Power out, Battery left, Transponder Mode status, Antenna Status, Satellite Orientation, ........)
- Inter board Connector Specification (PC/104 communication)
- OBC, SOLAR,charger,Orientation and Battery from existing Satellite ?
- 1 U Cube-Sat Space frame from existing Satellite (10x10x10) 1kg
- DSP 10 to 14Bit A/D /D/A Dynamic range. what is good enough ?
- PCB Board size details PC104 with cutouts for wire.
- Space frame and Solar panel frame and Antenna deployment. (out of scope)
- Solar panels. (Out of Scope)
- Power regulator and Charge regulator and Battery. (out of Scope)
- Orientation controls. (out of scope) (Stabilization)
- RF Linear Transponder using SDR / DSP. (70cm up 2.4Ghz or 1.2Ghz down)
- OBC (In scope ARM M4 or possibly A9) (FreeRTOS)
- Inter board communication standard.
Out of Scope for now:
- Space frame, Solar panels and panels frame.
- Solar panels
- Power regulator and Charge regulator and Battery.
- Orientation controls.
- Linear Transponder using SDR / DSP. (ARM Processor possibly not FPLG due to power constraint.)
- Telemetry TX
- Command control RX
Block diagram.
Transponder SDR transmitter. (Down-link 145.9?? MHz USB) (not confirmed) (250Khz)
Telemetry transmitter
- Estimated TX full power for beacon and transponder (300 mW) when Sat is in sunlight.
- When satellite is in eclipse low power of about (30mW).
Transponder SDR receiver. (Up-link 435.??? MHz LSB ) (not confirmed) (250Khz)
- Estimated maximum TX up-link power of 5 watts with a 7 dBi gain antenna.
Beacon / Telemetry
Here are several DDS signal generators I'm looking at:- AD9833 0 - 12.5 Mhz
- AD9850 0 - 50 Mhz
- AD9851 0 - 70 Mhz
- Si5351 0 - 150 Mhz
- Si5351A 0 - 290 Mhz
- AD9959 0 - 500Mhz
- AD9952 0 - 500Mhz Practical max 160Mhz depending on patern
1.2Ghz band plan for Downlink
TX
- https://github.com/F5OEO/rpitx
- http://ebrombaugh.studionebula.com/radio/txdac/index.html
- https://www.etherkit.com/rf-modules/si5351a-breakout-board.html
- http://www.simplecircuits.com/files/Download/QEX_release.pdf
- http://www.amrad.org/projects/sdr/
- https://myriadrf.org/projects/rdk/
- http://www.eevblog.com/forum/projects/the-sdr32-a-stm32-based-software-defined-radio/
- http://www.stm32-sdr.com/styled/index.html (PSK)
- https://wiki.analog.com/resources/eval/user-guides/ad-fmcomms2-ebz/software/baremetal?rev=1395324588#code_size_information ( AD9361 NON OS Drive)
- https://github.com/GomSpace/libcsp (Cubesat Space Protoco)
- https://github.com/robots/APRS (STM32 APRS code)
- https://michaldemin.wordpress.com/2012/02/27/cheap-afsk-tnc/ (AFSK stm3 2)
- https://github.com/athirasubhash/AX25MODEM (AX25 for STM32)
- www.analog.com/en/education/education-library/videos/3845680080001.html (Video Analog devices)
- https://datasheets.maximintegrated.com/en/ds/MAX2837.pdf (IQ front end Maxim)
- https://www.maximintegrated.com/en/products/analog/data-converters/analog-front-end-ics/MAX5863.html (A/D and D/A MAXIM)
- https://github.com/mossmann/hackrf/blob/master/firmware/common/max2837.c (max2837 c Library)
- http://www.g4jnt.com/DDSVHFBeaconDriver.pdf (DDS beacon generation)
Possible def tools.
- GNU radio
- Math lab
- ARM DEV board tools. (How to setup Eclipse for Arm development)
- Real time OS https://istarc.wordpress.com/2014/08/04/stm32f4-behold-the-project-wizard/
- Installing FreeRTOS on STM32F4 https://istarc.wordpress.com/2014/07/10/stm32f4-deploy-freertos-in-under-10-seconds/
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