Perfect signal processing (filtering) is essential for best decoding results, which are achieved by using the correct filters in the receiver. Doing so prevents blocking effects from strong nearby signals. However correctly processed signals may be unavailable, e.g., when a receiver does not offer optimum filters or when using recorded signals. To overcome these obstacles additional passband filters are included in the WAVECOM decoders to assist the operator in separating signals within the analyzed frequency spectrum.
In the WAVECOM GUI a passband (PB) tuning bar is placed below the tuning FFT window. If tuning FFT is not available, as is the case for some modes, the parameters can be set in the Demodulator Menu.
For many modes the parameters PB Center, PB Bandwidth and Center can be individually controlled (see the table below).
|
Item |
PB Conf. |
Remarks |
|
DSP |
+ |
Freely configurable |
|
AM |
+ |
Freely configurable |
|
CW |
+ |
Freely configurable |
|
GFSK |
+ |
PB center frequency controlled from offset frequency setting |
|
FFSK |
+ |
PB center frequency controlled from offset frequency setting |
|
- |
PB automatically adjusted depending on center, shift and speed | |
|
MFSK |
- |
Individual tones are filtered and PB automatically adjusted depending on tone spacing, center and speed |
|
DTMF |
- |
Individual tones are filtered and PB automatically adjusted depending on tone spacing, center and speed |
|
BR6028 |
- |
Preconfigured filters that cannot be changed. The location of the pilot tone can be manually set |
|
BPSK |
+ |
Freely configurable |
|
QPSK |
+ |
Freely configurable |
|
OQPSK |
+ |
Freely configurable |
|
DPSK |
- |
PB bandwidth automatically adjusted depending on center, shift and speed. The center frequency can be manually set |
|
DXPSK |
- |
PB bandwidth automatically adjusted depending on center, shift and speed. The center frequency can be manually set |
|
DBPSK |
- |
PB bandwidth automatically adjusted depending on center, shift and speed. The center frequency can be manually set |
|
DQPSK |
- |
PB bandwidth automatically adjusted depending on center, shift and speed. The center frequency can be manually set |
|
D8PSK |
- |
PB bandwidth automatically adjusted depending on center, shift and speed. The center frequency can be manually set |
|
D16PSK |
- |
PB bandwidth automatically adjusted depending on center, shift and speed. The center frequency can be manually set |
|
IQ |
+ |
Freely configurable |
|
ANALYSE |
+ |
Freely configurable |
|
FFT |
- |
No filtering implemented |
|
TIME |
- |
No filtering implemented |
|
OFDM |
- |
No filtering implemented |
|
SUBTONE |
- |
No filtering implemented |
|
DISCRIMINATOR |
- |
No filtering implemented |
|
EXT-DEM |
- |
No filtering implemented |
|
BYPASS |
- |
No filtering implemented |
The PB parameters can be set to maximum bandwidth (switched off) with the Maximize Passband button.