Tuesday, May 12, 2009

Subharmonic mixers in superhet designs

The subharmonic mixer being such a success in direct conversion receivers, the question is, would those mixers do a good job in as product detectors, with the BFO running on half the intermediate frequency? What about using subharmonic mixers in a bi-directional stage being modulator and product detector?
Standard frequencies [MHz] that would allow for such a configuration:
  • 1.0000, 2.0000
  • 1.8432, 3.6864
  • 2.0000, 4.0000
  • 2.0480, 4,0960
  • 2.097152, 4.194304
  • 2.4576, 4.9152
  • 2.5000, 5.0000
  • 3.0000, 6.0000
  • 3.0720, 6.1440
  • 3.2768, 6.5536
  • 3.579545, 14.31818 (*)
  • 3.6864, 7.3728
  • 4.0000, 8.0000
  • 4.4336, 8.8672
  • 5.0000, 10.0000
  • 5.1200, 10.2400
  • 6.0000, 12.0000
  • 6.1440, 12.2880
  • 7.3728, 14.7456
  • 8.0000, 16.0000
  • 9.2160, 18.4320
  • 10.0000, 20.0000
  • 11.0592, 22.1184
  • 12.0000, 24.0000
  • 12.2880, 24.5760
  • 16.0000, 32.0000
  • 18.0000, 36.0000
  • 24.0000, 48.0000
The pair marked with (*) uses four times the oscillator frequency, technically possible, however, I got doubts about the usefulness of that respective pair.

For some of the (lower) frequencies, CMOS oscillators are available, making some of the design particularly simple.

1 comment:

  1. Please, if you know more pairs, share them with me.

    ReplyDelete