Cross-polarized multi-channel W-band radar for turbulent flow velocity measurements

In this paper a cross-polarized multi-channel W-band radar for contactless velocity measurement of turbulent flows (pneumatically conveyed dust or gas) in industrial pipes is presented. The system is based on three linear modulated FMCW radar channels with separate RX/TX, which are fed into wideband orthomode transducers. For maximum SNR each channel has two focused dielectric lens antennas resulting in a narrow beam through the fluid at three different locations with known spacing. The reflectors are implemented by means of wideband trans-polarizing reflectors. This allows high precision cross-polarization (HV,VH) time-of-flight measurements through the pipe to the fixed position targets with reduced influence of the not trans-polarized pipe's window reflections. The flow velocity is extracted by correlating the time-delay between the flowing vortexes as they travel past the three radar beams, by use of an FPGA with real-time processing capabilities. Each radar channel is based on a SiGe transceiver MMIC stabilized by a PLL concept allowing highly linear fractional-N FMCW sweep generation from 68 to 93GHz with adjustable ramp duration. In this paper an overview of the system components is given, and by presenting the first single channel measurement results, the performance is demonstrated.