Noise Level in System

Hello,

We are currently using custom designed PCB and software to interface the Myriad RF board to an FPGA with the intention of collecting GPS signals. We have success using an RF signal generator the mimic the GPS carrier frequency, but when attempting to use an antenna we have noticed that the noise floor of our system is very high. We are seeing a noise floor with no inputs connected to the Myriad RF board of roughly -30dB.

Does anyone have any numbers for a similar test setup? (no input to Myriad RF, any combination of components such as LNA and LPF enabled or disabled). We know of a few issues in the current PCB that should hopefully reduce the noise level, but we were hoping to get a better idea of the typical Myriad noise floor as well.

Thanks a lot.

Hi,

I am looking for similar graphs, please provide me at the earliest if you spectrum analyzer screenshots for the same.

Looking for o/p noise level when no input is connected to TXINI and TXINQ pins for VGA1 = -4dB and VGA2 = 25. and TXLPF = 14MHz and when input is fed with an sine wave.

regards,
Subrahmanya K S

Adding Spectrum Analyzer screen grabs which shows increased noise floor with peaks. Peaks are at the TxLPF Cutoff frequency. TxVGA gains are at -4 and 25.

Is this a typical observation on Myriad RF + ZIPPER board setup ? or there is a potential setup issue at my end ?

regards,
Subrahmanya K S

Hello,

This is typical filter performance when the TX is driven throughout the analog inputs. The noise is generated by internal filters close to the cut off frequency.

Rich

Hello,

Do we observe similar increase in noise floor if I use internal DAC to generate the TX IQ signals ? is this issue only observed when we use Analog IQ input signals ?

regards,
Subrahmanya K S

Hi,

The filter noise is dominant when you use analog inputs. When you engage DACs, you will see higher inband noise due to DAC quantization noise.

Rich.

Hi,

Is there a method to reduce this noise ? Is there a document which capture Tx output spectrum for CW and OFDM signals ?

regards,
Subrahmanya K S

I realize this is an old post, but you should be able to just bypass the LPF right? If you are inputting a signal from the signal generator to the analog I and Q, most likely that signal is fairly clean without the LPF. Bypassing the LPF will prevent the filter noise from being injected.

Correct!