My hardware is an analog device SDR+Xilinx FPGA (sdr = fmcomms4-ebz). The direct conversion transceiver (ad9364) has a tunable channel bandwidth of 200Khz - 56Mhz. I am employing BPSK modulation on a PRN code of 100K bits in length (repeats itself).My Tx Sampling rate is 6 Msps, thus the highest frequency present in my transmitted signal (barring harmonics) is 6Mhz.
1) According to Nyquist criterion the minimum bandwidth should be (Fs/2) where Fs is the sampling frequency. However, the main lobe of the BPSK spectrum is 2*Fs wide. Is my minimum Tx bandwidth 3Mhz or 6Mhz ?
2)On the Receiver side if I am oversampling by a factor of 2 (ie Fs_Rx = 2*Fs_Tx) should I adjust my Receiver's channel bandwidth to the sampling rate of the receiver or the transmitted signal? ie should my Rx channel bandwidth be equal to my transmitters channel bandwidth or double ?
3) Beyond the appearance of higher order harmonics and inefficient use of bandwidth, are their negative effects to using an arbitrarily large bandwidth for both my Tx and Rx nodes? (effects like ISI,RF interference)
Pulse shape currently using root raised cosine filter, however I am also testing unfiltered data i.e. rectangular pulses. How does this effect the bandwidth (i assume the root raised cosine would allow for lower bandwidth)
Inquiring about both (sorry I should have specified). My current understanding is that the required bandwidth at baseband is half that of passband. Is that correct?