Signalgenerator

What is it?

A homemade RF signal generator with these features:

• Frequency range: 5MHz to 2.1GHz
• Amplitude range: approx. -40dbm to +15dbm (slightly frequency dependent)
• Modulation
  • AM
  • FM
    • Up to 12.5MHz frequency deviation
  • QAM
    • Up to 32 constellation points
    • Up to 33M samples per second
    • Up to 36 samples per symbol
    • Pulse-shaping and differential encoding
  • External I/Q inputs
    • AC/DC coupling
    • Up to +30dbm/10Vpk input
    • Up to 10MHz of bandwidth
• Spectral purity@+10dbm:
  • Harmonic:
    • f >= 150MHz: <-30dbc
    • f >= 10MHz: <-25dbc
    • f < 10MHz: <-15dbc
  • Non-harmonic:
    • <-50dbc (limited by noise floor for lower output power)
  • Phase noise:
    • <-80dbc/Hz@10kHz offset

Why was it build?

• Gain experience with RF circuit design
• Unwilling to pay the price for commercial generators (of course this one can't compete with a commercial one but should be good enough for simple RF experiments)

How does it work?

For a high level overview see the description of the RF generation. For the effect of RF shielding see these measurements.

More Pictures:

The inside: (I reused the frontpanel PCB from this project) The external modulation input PCB: The main RF board: