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Dream - DRM Receiver Software

User Guide

Evaluation Dialog DRM - Main Plot

In the center of the Evaluation Dialog there's a graphical display of different vectors of the DRM decoder.
The different plots can be selected by the buttons on the right side.
Main Plot Main Plot - Input Spectrum Main Plot - Shifted Power Spectral Density of Input Signal Main Plot - Channel Transfer Function / Group Delay Main Plot - Channel Impulse Response Main Plot - Main Plot - FAC Constellation Main Plot - SDC Constellation Main Plot - MSC Constellation Main Plot - Audio Spectrum DC Frequency Offset Sample Frequency Offset Doppler / Delay MSC CRC LED SDC CRC LED FAC CRC LED Frame Sync LED Time Sync Acq LED I/O Interface LED DRM Mode / Bandwidth Interleaver Depth SDC / MSC Mode Prot. Level (B/A) Number of Services Received time - date Signal to Noise Ratio (SNR) Frequency Interpolation Time Interpolation Time Sync Tracking Flip Input Spectrum Mute Audio MLC, Number of Iterations Log File Save Audio as WAV Freq Filter Evaluation Dialog (DRM Mode)
Input Spectrum
This plot shows the Fast Fourier Transformation (FFT) of the input signal. This plot is active in both modes, analog and digital. There is no averaging applied. The screen shot of the Evaluation Dialog shows the significant shape of a DRM signal (almost rectangular). The dashed vertical line shows the estimated DC frequency.
In AM mode this line is very important for the analog demodulation. Each time a new carrier frequency is acquired, the red line shows the selected AM spectrum. If more than one AM spectrums are within the sound card frequency range, the strongest signal is chosen.
Dream - DRM Evaluation Dialog - Plot: Input Spectrum
Shifted Power Spectral Density of Input Signal
This plot shows the estimated Power Spectrum Density (PSD) of the input signal. The DC frequency (yellow dashed vertical line) is fixed at 6 kHz. If the frequency offset acquisition was successful, the rectangular DRM spectrum should show up with a center frequency of 6 kHz. This plot represents the frequency synchronized OFDM spectrum. If the frequency synchronization was successful, the useful signal really shows up only inside the actual DRM bandwidth since the side loops have in this case only energy between the samples in the frequency domain. On the sample positions outside the actual DRM spectrum the DRM signal has zero crossings because of the orthogonality. Therefore this spectrum represents not the actual spectrum but the "idealized" OFDM spectrum. (The screenshot was taken with BP filter off.)
Dream - DRM Evaluation Dialog - Plot: Shifted Power Spectral Density of Input Signal
Channel Transfer Function / Group Delay
This plot shows the squared magnitude (green line) and the group delay (blue line) of the estimated channel at each sub-carrier.
Dream - DRM Evaluation Dialog - Plot: Transfer Function / Group Delay
Channel Impulse Response
This plot shows the estimated Impulse Response (IR) of the channel based on the channel estimation. It is the averaged Hamming Window weighted Fourier back transformation of the transfer function. The length of PDS estimation and time synchronization tracking is based on this function. The yellow dashed vertical lines show the beginning and the end of the guard-interval. The two blue dashed vertical lines show the estimated beginning and end of the PDS of the channel (derived from the averaged impulse response estimation). If the "First Peak" timing tracking method is chosen, a bound for peak estimation (horizontal dashed yellow line) is shown. Only peaks above this bound are used for timing estimation.
Dream - DRM Evaluation Dialog - Plot: Impulse Response
FAC Constellation
This plot shows the constellation of the FAC logical channel of the DRM stream. The FAC has 4-QAM modulation. (To get a realistic view the Evaluation Dialog should be stretched vertically.)
Dream - DRM Evaluation Dialog - Plot: FAC Constellation
SDC Constellation
This plot shows the constellation of the SDC logical channel of the DRM stream. Depending on the current transmitter settings the SDC can have 4-QAM or 16-QAM modulation. (To get a realistic view the Evaluation Dialog should be stretched vertically.)
Dream - DRM Evaluation Dialog - Plot: SDC Constellation
MSC Constellation
This plot shows the constellation of the MSC logical channel of the DRM stream. Depending on the current transmitter settings the MSC can have 16-QAM or 64-QAM modulation. (To get a realistic view the Evaluation Dialog should be stretched vertically.)
Dream - DRM Evaluation Dialog - Plot: MSC Constellation
Audio Spectrum
This plot shows the frequency spectrum of the AAC encoded audio signal.
Dream - DRM Evaluation Dialog - Plot: Audio Spectrum
DigiBC · DRM Last modified: 09/25/2004