The incoherent scattering radar (ISR) is the only ground device on Earth that can detect the parameters of the ionospheric plasma because of its large detection range, high detection accuracy, and high spatial resolution. The prototype ISR system of Nanchang University has been completed now. Compared to the existing ISR systems in the world, which have a high radio frequency (RF) power and antenna array, high power consumption, expensive equipment operation, and maintenance costs, the radar has the advantages of low power consumption, low cost, and modularity. This radar system uses novel techniques of software-defined radio (SDR) and active phased array antennas to detect changes in the ionosphere. This article introduces the system design and antenna array of the software-defined radar prototype. The built-in radar transmitting and receiving equipment and specific radar parameters are described in detail and the radar detection results under different detection conditions are presented.