trivial TX design question
Should I go:
1) Transmitter, Dig Step Atten, AMP
2) Transmitter, AMP, Dig Step Atten?
3) Either one/doesn't matter?
and please briefly state why..........
My transmitter max TX power is 1dBm
The DSA offers
* .5 - 31.5 dBm of attenuation in .5dB steps
* P1db of 34 dBm
*IP3 of 52 dBm
The AMP offers
* 17 dBm of gain
*P1dB of 24dBm
*IP3 of 43 dBm
Here are things to consider:
attenuator first allows lower IMD in the amplifier. It also produces lower IMD in the attenuator. It has the disadvantage that glitches from changing attenuation get amplified and radiated. It also puts lower signal level in the amplifier reducing the SNR.
in my view both chains are OK as the Tx power is very much lower to the DSA or AMP.
This is valid for Transmit only
Answer these questions please.
1) Since IMD is caused by non-linear devices, is the DSA or TX or Both causing the IMD to go into the amplifier?
2) Lets say that the DSA comes after the AMP, wont the DSA still lower the IMD?
3) Lets say that the DSA come befor the AMP, wont the AMP still increase the IMD?
4) Assuming that the AMP is the last stage and the amp gain is 17dBm is the total chain output just 17 dBm or do you take into account all the components in the chain i.e. the TX power (1dBm) +(-DSA attenuation value) +(17 dBm)?