Table 3 The comparison of the specifications of the analog system with those of the digital system
From: Software-defined radio-based HF doppler receiving system
| Â | Analog system | Digital system |
|---|---|---|
Channel | 4 | 4 |
Reference Frequency | Rb Frequency Standard | Build in GPS receiver |
System | Direct frequency conversion then A/D | A/D then multiple direct frequency conversion |
Detection | 8Â Hz frequency offset detection | IQ coherent detection |
Filtering | Active LPF and HPF | Digital LPF |
Sampling | 16 bit 100 sps (at the receiver output) | 14 bit IQ 100 Msps (at the receiver input) |