BPSK modulation of a baseband signal

[preethi19]

I was reading a paper abt baseband digital transmitter. It was put that the preamble is composed of BPSK symbols ie (1,-1). Suppose we give a digital input to a BPSK block, this binary data is multiplied with a sinusoidal carrier wave and phase is shifted. I get this part but wat will the BPSK output be... Because later the BPSK output wave is differentially encoded and this differential encoding is done on a digital output sequence got from the BPSK output. But how can a BPSK give out a digital output. Because i saw In BPSK modulation binary data is multiplied with carrier wave and the BPSK output is got to be a analog wave( carrier wave) which is phase shifted. So how can this analog wave be differentially encoded. Or is there a way to get digital output in BPSK. I'm totally confused. Pls help. Thank you

 

[kripacharya]

Surely the differential encoding/ decoding is done at the baseband level, and not on the modulated carrier.. ?

 

[preethi19]

but in the paper i studied it was mentioned in that the preamble is of BPSK symbols(which means the baseband is already shifted) and is of (1,-1) and this sequence is of c=(c1,c2....cW) and this sequence is differentially encoded where am=cm xor cm-1.... so am is the differentially encoded sequence. So in this case the encoding seems to be done on the carrier right??? sorry if i am wrong but please help..

 

[D.A.(Tony)Stewart]

The transmitter must use a mixer that is switched digitally ( such as diode bridge is a diode XOR gate logic and also a mixer)

The binary signal thus selects the normal or inverted carrier signal 0, or +180 deg for binary phase shift key (BPSK) the baseband signals are often duo binary or bipolar baseband voltages or +v, -v .

the receiver may have many levels of synchronization;
- frequency locked, phase locked
- bit sync, and polarity sync for bi-phase
- byte sync
- frame sync

There are many types of baseband modulation, NRZ, RZ, Bi-ph-Mark, Bi-Ph-Space, Bi-ph.Invert etc etc not be confused with the carrier modulation.

 

[kripacharya]

but in the paper i studied .....

why don't you post the paper so that we can see it ourselves ?