A New Design for Digital Ionosonde

In this paper a new design for digital ionosonde is presented based on the concept of directly sampling in the RF domain, and the real time digital down-conversion processing is implemented in FPGA device, which improves the signals identity of I and Q, and enhances the dynamic range of the receiver. In addition, since the digital waveform generation in transmitting path, the digital down-conversion processing in receiving path, data pre-processing, and timing control functions of the whole system are integrated in one FPGA chip, which improved the flexibility of the ionosonde. To verify the design, a high quality digital ionosonde called CAS-DIS (Chinese Academy of Sciences, Digital Ionosonde) has been developed. This paper describes the details of CAS-DIS, its main features and testing results in the ionosphere detection, including in Wuhan ionospheric sounding and calibration station and Wuhan-Beijing oblique ionospheric sounding system, and the observations show that performance of the iononsonde using the proposed design is superior, and the ionosonde can operate in both vertical and oblique sounding mode, to meet a variety of applications in ionospheric detection.