Hi,
Thanks everyone for the reply.
1. I forgot to mention that this an injection locked oscillator locked to the the third harmonic of 800 MHz i.e. 2.4 GHz
2. The PCB has not been designed very well since it was my first RF PCB. The decaps (5pF, 1nH, 10nH) are far away IC pins. I shall design a new one though.
RCinFLA: How would low frequency supply noise (3.7KHz) appear near 2.4 GHz. Does it get modulated & upconverted?
jiripolivka: Do you mean the supply may have noise at 2.4GHz + 3.7KHz?