SDRT

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SDRT

Release status: obsolete [box doku]

Description use the VGA port to transmit I/Q signals on any frequency
Author(s)  siro (siro)
Last Version  0.1
License  GPL

Software Defined Radio Transmitter[Bearbeiten]

Description[Bearbeiten]

Hardware to transmit anything on any frequency. That means any information / modulation can be transmited on a channel between 750 and 1150 Mhz, which is the possible internal PLL frequency-range for ADRF6701. The I/Q signals are feed through a VGA-compatible 15pole-DSUB connector.
This board is intended to be used with VGAtoBaseband.
This is a prototype with a teensy controlling the ADRF6701. The frequency can be adjusted using a USB terminal connection. The board has a 50Ohms SMA connector transmitting about 0dBm using VGA signals (0.7Vpp).

Sdrt top.jpg

Board[Bearbeiten]

Overview[Bearbeiten]

  • VGA DSUB connector, baseband input
  • power jack DC 5.5V - 6.0V, > 300mA
  • 4 LEDS
    • power
    • teensy alive
    • rf enabled
    • unused
  • teensy
  • SMA connector, rf output
  • switch (rf disable/enable)

Clock[Bearbeiten]

26 Mhz TCXO +-2 ppm 1.8V

Low pass[Bearbeiten]

I'm using one 9Mhz 3rd order Bessel low pass filter on each channel. This isn't included in the schematics. All three channels are terminated using 75 Ohms.

SPI[Bearbeiten]

The SPI interface should have series resistance of more than 50 Ohms.

ADRF6701[Bearbeiten]

  • reference design
  • internal vco and pll is used
  • LO path is disabled
  • input multiplier 1:1
  • internal LO divider 1:4
  • fin: 26Mhz ac coupled
  • lo output freq:
fout = fin / 4 * ( INT + (mod / frac) )
where:
INT, MOD, FRAC are register values

Layout[Bearbeiten]

todo

TODOs[Bearbeiten]

  • use ADRF6755
  • shrink board size
  • don't use eeprom 24C02
  • don't use teensy, maybe Attiny
  • don't use sot-123 diodes
  • rf power amplifier
  • use a display to show the current freq.
  • rotary switch

Summary[Bearbeiten]

  • new i/q filter design is critical
  • adrf6703 doesn't work as intended (write only, no debug pins)
  • new design done -> this part is now obsolete

Links[Bearbeiten]