Aritomi, Yuhang

We are having issue of offset and bad SNR.

We checked the 14MHz peak from TAMA PD (as shown in figure 1 and 2). Usually it is amplified to -42dBm after an amplification of 21dB from -63dBm. The SNR before amplification is about 14dB, which is increased to about 20dB after the amplification.

The local oscillator used for demodulation is -7dBm, as shown in figure 3 .

The demodulated signal before and after amplification are shown in figure 4 and 5. Compared with the linewidth shown in figure 6, the SNR for demodulated signal is only about 1.5.

We could see that there is a almost constant offset around 8mV. Therefore, a larger LO may solve the offset problem.

(TAMA1991 demodulator was used and shown in this entry. We also tried other two demodulators, which give much larger offset)