NI Home > Community > NI Discussion Forums

IF-RIO

Reply
Member
tigr
Posts: 18
0 Kudos

coherent bpsk modulator

Hello

 

I need coherent BPSK modulator, i.e. the phase of IF carrier should start at the same value (let say zero) for each bit. Placing LUT in FPGA vi does not solve the problem and the starting phase is changed in stochastic manner  from bit to bit

 

thank you for any idea

 

tigr

 

Active Participant
Posts: 219
0 Kudos

Re: coherent bpsk modulator

[ Edited ]

Hello tigr,

I am not sure I fully understand what you are trying to accomplish but I can offer a few suggestions based on what I think you are attempting. I believe you want each generation to begin at a set phase (i.e. zero phase). You are seeing random carrier phase on each bit which is expected if the carrier is not a multiple of the message frequency. I believe you have two options, either generate the signal such that the IQ rate and the Carrier frequency are multiples of one another so that the message signal will align to the carrier signal, or rest the NCO in the digital upconverter (DUC) before each bit is sent. This can be done by switching DAC profiles, which forces a reset of the NCO.  

JaceD
Signal Sources Product Support Engineer
National Instruments