QPSK modulator

[lahp0001]

I recenty read a tutorial by charan langton on QPSK

modulation and I would like to comment that it cleared

up a great deal of confusion. I noticed in the tutorial

that some of the constellations may have been made

on Cadence SPW. For a project in my communications

class I am going to build a QPSK modulator on SPW .

I was wondering if anyone could give me a hint on

how do this, for example what blocks would I use

convert binary data to polar( eg 0101 => -11-11)?

And is there a block that converts serial data to

parallel data. Any help would be deeply appreciated.

[Charan Langton]

In SPW you would need to use the complex source>QPSK. You set the baud rate to the symbol rate (not bit rate). Set the sampling frequency to 12 to 16 times the symbol rate. If you want to modulate this on a carrier, then you use a block called "spectral shifter" in series with the QPSK source. Set the frequency of the spectral shifter to your carrier frequency. If you want the signal rrc shaped, then use a time domain raised cosine filter before the spectral shifter.

Voila, you have a QPSK modulator. Modulating is easy, reverse is hard.