摘要(英) |
In this thesis, the transmitter/receiver of a X-band fully polarimetric scatterometer is designed and implemented. Due to the high attenuation of the electromagnetic waves in the coaxial cables at X-band, the superheterodyne structure is applied on the design of transmitter/receiver.
A vector network analyzer (VNA) is used as the signal source. Due to VNA's high ability in signal process, many features such as system calibration and time gating can be easily implemented and performed. The signal from the VNA, which ranges from 1 GHz to 2 GHz, is upconverted to 9 GHz to 10 GHz by mixers. An Amplifier is used to compensate the signal attenuation and thus raise the dynamic range and measurement sensitivity of the scatterometer. A computer-controlled switching system is implemented to alternate different polarization states, so the fully polarization measurement can be achieved. An single dual-mode pyramidal horn in conjunction with circulators is applied to avoid the antenna interference inherent in the multi-antenna system. Therefore the backscatter can be measured in short ranges. In order to conduct automatic measurements, a computer program is developed for data acquisition, switching control, and system calibration. |
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