RF exciter subsystem of Ka-band cloud profiling radar

The radio frequency (RF) exciter configuration briefed in the system description of the Ka-band cloud profiling radar, which is being indigenously developed at Society for Applied Microwave Electronics Engineering and Research (SAMEER) Mumbai [1], has undergone some modifications and advancements. One such added feature, an Ethernet plug-and-play approach, is completely developed and tested. A novel approach to waveform generation is used that utilizes dedicated Analog Devices AD9910 Direct Digital Synthesizer (DDS) integrated circuits that are capable of generating waveforms directly at higher Intermediate Frequencies (IFs). A single-pole-single-throw (SPST) RF-switch based scheme is adopted in the current zenith looking Ka-band radar [2] for realizing pulse modulation and was initially planned in [1]. However, due to the internal pulsing capability of the DDS-scheme being adopted in the modified configuration, the SPST switch is no longer included and a coder circuitry used in [2] for generation of phase coded waveforms is no longer required. With the current pulsing scheme, an isolation of around 60 dB is observed between the on and off periods of the transmit pulses. The RF exciter subsystem has been tested to work seamlessly at both the firmware and hardware level; and has undergone integration testing with other subsystems as well. The specification of the modified configuration is summarized in Table 1.