I've been evaluating the CC1101 for use as the transmitter/receiver in a simplex radio link design. I've noticed a drop in recevier sensitivity when the channel selected happens to be certain multiples of 13 MHz. I'm guessing this is due to a high order harmonic of the the reference frequency (half the XTAL frequency of 26 MHz) falling bang on the receive channel. This result comes directly from standard development boards running at around 400 to 500 MHz.
I'm wondering if I might be able to reduce the effect by slowing the edges of the crystal waveform down (I suppose this assumes that the harmonic is from the crystal, in other words a multiple of 26 MHz and not the divided crystal frequency). Any suggestions would be welcome.
Note that I was hoping to deliberately operate the CC1101 transmitter on an exact multiple of 13 MHz, in other words force the CC1101 synthesizer to run in INTEGER N mode instead of FRACTIONAL N in order to reduce the transmitter spurious components which is important in my application. This works very well and results in a really clean spectrum but the drop in recevier sensitiity is preventing this approach.
Thoughts?
Steve
