Proceedings with Extended Abstracts (single PDF file) - Radio ...

samples. We normally use the three filter stages as fix filters matched to the widest analogsystem BW and perform further filtering in the PC for software convenience, but otherconfigurations are available if desired. When further filtering is performed in the PC, thedynamic range is further enhanced.We use a single 64 MHz local oscillator to generate the ADC, digital filter and radarcontroller clock as well as the transmitter excitation frequency. This guarantees thecoherence of the receiver and transmitter frequencies.Following we summarize the digital receiver advantages:• Dynamic range greater than 85dB.• No cross talk.• Perfect coherent quadrature detector.• Exact control of BW shape.o Same in multiple receivers.o Same for I and Q.• Programmable filter and perfect match filter.On version 2 we plan to implement 4 digital receivers with a single control card. In thisversion the configuration of the receivers is performed using the same PCI card it is used fordata taking. More receivers can be easily implemented by duplicating the system withadditional interface cards.Illustrative resultsOn figure 3 we show a range time intensity plot showing signals from the equatorialElectrojet, Spread-F and Incoherent-Scatter signals from the F region. On figure 4 we showthe same signals for two different times, this time showing the signal power profile andspectrum for the two receivers (left and right). On figure 5 we show power profiles andspectrum of Electrojet echoes as well as echoes from the 150-km irregularities. Note thelarge dynamic range for all, although we are still not exercising the full dynamic range of thesystem. The radar parameters for the two experiments shown are displayed in Table 1.370