SDRT Release status: experimental [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

Description

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).

Board

Overview

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

26 Mhz TCXO +-2 ppm 1.8V

Low pass

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

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

ADRF6701

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

todo

teensy software