If you are using the 89601A Vector Signal Analyzer (VSA) software, version 6.10 or higher, to demodulate waveforms generated by the N7615C Signal Studio Software, take care to set the appropriate parameters in Demodulation Properties window of the VSA software as noted below.
Ensure that the Reference Specification that is used to generate the waveform corresponds to the standard used in the VSA software for demodulation.
|
Reference Specification |
Standard for VSA |
|---|---|
|
802.16-2004 Cor1/D2 |
P802.16 OFDMA (April 2005) |
|
802.16-2004 Cor1/D3 |
P802.16 OFDMA (June 2005) |
Note that the Nominal BW default value of the VSA is 9.996 MHz in the Demodulation Properties window. This is the value needed to demodulate a 10 MHz bandwidth signal generated by the Signal Studio software. The difference is due to the equation used in each software to calculate the sampling frequency, Fs.
The Signal Studio software uses the floor function according to section 8.4.2.4 in the 802.16-2004 standard: Fs = floor (n x BW/8000) x 8000, where the sampling factor, n, is 8/7 for 802.16 OFDMA. The VSA software does not use the floor function causing this equation to simplify to Fs = n x BW and thus uses a different sampling frequency.
The subcarrier spacing is Df = Fs / Nfft so BW = 1/n x Df x Nfft. In the case of a 10 MHz bandwidth and 1024 FFT, Signal Studio includes the floor function producing a subcarrier spacing of Df = 11.15625 kHz. Using this value yields a VSA nominal BW value of BW = 7/8 x 11.15625 kHz x 1024 = 9.996 MHz.