GTP Transceiver output waveform

[ma]

Hello,

we would like to use Artix-7 GTP 6.6 Gb/s transmitter for DC-free pseudo-random-sequence generation in a civil radar application. Since we use an analog receiver we don't care about ISI and eye diagrams. We are curious about using the emphasis feature to suppress frequency content above 3.3 GHz since this is our aliasing frequency. Of course will also use analog filters.

UG482 page 114-120 and DS181 describes the transmitter. We tried to derive output currents of the 3 transmitters (pre, post and main) from the datasheets but did not succeed. It seems like TXDIFFCTRL sets TXMAINCURSOR to 51-80 which is then corrected by the amout of emphasis as in TXPOSTCURSOR and TXPRECURSOR.

Is it possible to invert emphasis with TXPOSTCURSORINV to generate a pulse as in Fig. 1? How can we calculate driver currents to simulate using our circuit simulator?

Fig 1: one symbol of pseudo-random sequence, properties of whole sequence is calculated by convolution in time domain / multiplication in frequency domain, which means frequency content is defined by this symbol consisting of several zeros and ones of the transmitter (we used "11110000" for better visibility, later we will use "1100")

Kind Regards,
ma

 

[roym]

Not completely sure what you are trying to do but it looks like you want to have 2 periods of preemphasis and 2 periods of post emphasis to soften the transition edges.  This can't be done, however you do get some softening of the edges using the inverted emphasis.  But there is no way to invert the emphasis dynamically.