Dual Band, Microwave and TV White Space, Oscillator Design for Mitigation of Rain Attenuation

Abstract

In this research, a new dual band oscillator was designed for the application of frequency diversity of microwave line of sight communication. A different type of attenuation mitigation technique was implemented in Microwave band. Frequency diversity technique is one of attenuation mitigation technique. However, mitigation by frequency diversity using TV white space (TVWS) frequency band, which is a current research area, is a new idea. This technique can be implement on any of rural Microwave link distance starting from 5km to 50km. The level of rain attenuation calculation derived from the collected local rain data and by using specification of Microwave specific link. ITU-R recommendation was used to determine specific attenuation and threshold level. This thesis also consists of a new design of a dual band VCO, which is a small part of RF design but it is a major headache for designer. This VCO can operate in both Microwave (11GHz), and TVWS, which is the secondary user of the television frequency (470-862MHz in Ethiopia case). The design of VCO simulated using a software of AWR Design Environment. This oscillator can generate a required dual frequency band. Switching technique was used to convert from one operating frequency to another. The basic idea of this oscillator is to use single band oscillator at a time and switch off another. Therefore, when the signal of microwave degrades, it switches and uses another frequency band, which is the TV white space band. Switching is the easiest and least power consuming of dual band oscillator techniques. The major performance measurement of oscillator such as (Tuning voltage, phase noise, output power, and tuning frequency range) was measured. The major interesting output of this work is, its low phase noise of the higher and lower band -120@ 1MHz offset and -146 @1MHz offset respectively. In addition to its, figure of merit (FoM) is 167dBc/Hz and -200dBc/Hz of higher and lower band (0.5 and 11) GHz carrier frequency respectively. The power dissipation is 2.2mW, 0.67V DC voltage, 24% tuning range and Qfactor of tank is 22. However, the above result is sufficient, the phase noise gap of the two band is a little high because of a long gap between a higher and lower band. Therefore, this area will need further research.