MODELING OF ANALOG BLOCKS IN VERILOG-A
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Keying) with a symbol rate of 1.2288 Mega-symbols/s and a sample rate of
4.9152 Mega-samples/s. Two separate 16-bit pseudo-noise generators
generate the I and Q spreading sequences operating at the sample rate. Each
sequence is filtered with a 48-tap FIR filter.
GSM Signal Source (GSM-xmtr)
Using GMSK (Gaussian Minimum Shift Keying) modulation the GSM
(Group Special Mobile) source generates a signal conforming to the GSM
mobile communication standard. The first part of the GSM signal source is a
random binary generator with a bit rate of 270833.333 bits/s. The following
FIR filter is a Gaussian filter implemented with 32 taps and signal gain. In
the next step the signal is integrated using a modulo 2 integrator and split
into I and Q channels.
/4-DQPSK Signal Source (pi_over4_dqpsk)
The /4 differential QPSK baseband signal source generates random
binary data with a bit rate of 48.6 kbits/s. The data is converted from serial
to parallel (2 bits). A phase state coder maps pairs of bits to phase shift and
the following differential encoder shifts the symbol phase. Next the I and Q
channels are filtered. The FIR filter used is implemented with 64 taps.
The constellation diagram in Figure 10-13 depicts how the differential
encoded binary signal is mapped to the carrier phase.
00
01
11
10
I
Q
Figure 10-13. Constellation diagram
Eye-diagram generator
The eye-diagram is a widely used plot format to evaluate the quality of
digital modulated signals. The signals are plotted over a period of an integer
multiple of the symbol duration. This functionality is realized in the
Summary :
GSM Signal Source (GSM-xmtr) Using GMSK (Gaussian Minimum Shift Keying) modulation the GSM (Group Special Mobile) source generates a signal conforming to the GSM mobile communication standard. /4-DQPSK Signal Source (pi_over4_dqpsk) The /4 differential QPSK baseband signal source generates random binary data with a bit rate of 48.6 kbits/s.
Tags :
signal,source,rate,gsm,phase,filter,binary,fir,differential,symbol,mobile,filtered,gaussian