413x0g2 - CCSDS

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CCSDS REPORT CONCERNING BANDWIDTH-EFFICIENT MODULATIONS3.3.3 4D-8PSK-TCM PHASE NOISE RECOMMENDATIONIt is recommended that the phase noise for all the oscillators of the 4D-8PSK-TCMcommunication chain be limited according to the mask given in figure 3-42 for channelsymbol rates from 1 Ms/s up to 100 Ms/s. The figure shows the double-sided phase noisemask 2L(f) in dBc/Hz versus frequency in Hz.2L(f) in dBc/HzPhase noise mask-20-30-40-50-60-70-80-90-100-110-120-1301E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 1E+8f in HzFigure 3-42: 4D-8PSK-TCM Phase Noise Mask Recommendation3.3.4 CHANNEL FILTERINGChannel filtering is to be obtained by one of the following methods:– Square root raised cosine (SRRC) baseband shaping filter located prior to themodulator, with a channel roll-off factor α of 0.35 or 0.5. This waveform shaping isused in conjunction with a linear modulator and power amplifier.– Post-amplifier shaping using a filter located at the output of a non-linear poweramplifier. In this case, post-amplifier filtering of the NRZ 8-PSK signal is used inconjunction with a non-linear phase modulator or power amplifier.In both cases, the pre-detection filter (matched filter) in the receiver shall be a SRRC filterwith a roll-off factor α of 0.35 or 0.5.CCSDS 413.0-G-2 Page 3-33 October 2009
CCSDS REPORT CONCERNING BANDWIDTH-EFFICIENT MODULATIONS3.3.4.1 Baseband SRRC ShapingBaseband SRRC shaping should be used when the power amplifier is operated in a linearregion, when the symbol rate to center frequency ratio is low, or when there is amplifierlinearization.The normalized transfer function of the SRRC filter, H(f), is given by: 6⎧⎪⎪H ( f ) = ⎨⎪⎪⎩1211 ⎛⎜π+ sin2⎝ 2 fN0⎡⎢⎣fN−αf⎤⎞⎥⎟⎦⎠fNf < ff > fNN(1 −α)(1 −α) ≤ f ≤ f(1 + α )N(1 + α)where f N=1/(2T ChS)=R ChS/2 is the Nyquist frequency, and α is the roll-off factor. Thecorresponding impulse response of the SRRC filter is given by:4αht () =π TChS⎛(1 + α ) πt⎞ T ⎛ChS(1 −α)πt⎞ cos⎜ ⎟+sin ⎜ ⎟⎠⎝ TChS⎠ 4αt ⎝ TChS1−4 /( αt T ) 2The transmitter structure when using baseband SRRC shaping is shown in figure 3-43.ChSSerialdata INS/P converterDifferential encoderTrellis encoderConstellation mapperSRRCshapingα=0.35or α=0.5IQ8-PSKI/Q linearmodulatorLinearpoweramplifierFigure 3-43: Transmit Structure for Baseband Square Root Raised Cosine Shaping6 The unnormalized value of H(f) can be obtained by multiplying its normalized value by TChS.CCSDS 413.0-G-2 Page 3-34 October 2009
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