Research And Design Of RF Front-end Of Six Port Ranging System

The zero-intermediate frequency receiver based on six-port technology has been more and more popular in wireless communication applications. By using six-port demodulation technology, the radiofrequency received signal can be directly demodulated to baseband signal. For one thing, the A/D devices need not to operate at RF band, for another, some expensive device for example, phase detector, is not necessary. Due to these advantages above, we have investigated and designed the RF front-end of six-port measurement system as well as UWB Vivaldi antenna, six-port conjunction and local oscillator(LO) that consist of the RF front-end.The major subject and novelty of this dissertation are included below:1.Analysis and research of six-port receiver system. Based on pros and cons of various receivers, the principles and advantages of direct frequency conversion receiver using six-port technology have been illustrated, and the demodulation formulas of six-port technology have been deduced, the application of which in minor movement measurement has been figured out, and its principle and demodulation method have been deduced theoretically.2. The most principal part of the system. The six-port conjunction. In this article, a micros trip six-port conjunction based on Wilkinson power divider and 90 hybrid has been designed, which consist of a Wilkinson power divider and three 90 hybrids and operates between 5.6 GHz-6.2GHz. The six-port conjunction has been simulated and fabricated afterwards, and the simulation and measurement results match well. At the whole band, the simulated transmission parameters of port1 and port2 are better than-7dB, and the phase difference between each two of four output ports holds stable; the measured transmission parameters of port1 and port2 are better than-7.5dB, and isolation between LO and RF port is better than-20 d B.3. Design of UWB Vivaldi antenna. Two UWB Vivaldi antennas have been designed, each of which operates at 4-11 GHz, and one is traditional Vivaldi antenna, the other is a novel one. Aiming at the gain degradation at lower and higher band, rectangular edge and zero refraction index metamaterial have been loaded to rectify this defection. Furthermore, these two antennas have been fabricated and measured. The measured results show that the SWR of each antenna is lower than 2, and novel antenna gain is better than 10 dBi covering the whole bandwidth. In conclusion, the simulation and test results match well.4. Design of single frequency(5.8GHz) source. According to analysis of RF front-end using six-port conjunction technology, an identical frequency source is needed at both LO input port. Therefore, the single frequency source has been designed. The frequency source is implemented by adopting PLL technology. The phase frequency detector IC is ADF4016 from ADI, and the VCO is HMC431LP4 from Hittite. The test results show that phase noise is better than-85dBc/Hz@10kHz, and spur suppression is better than 65 dBc, both of which are better than proposed specifications.