The up growing wireless communication field always need such a system which is simple but more reliable for multiple applications. To fulfill these demands the modern receiver RF frontend can play an important role. A successful design could be a better solution, not only simple but also modern receiver architecture topology is necessary. To design RF circuits is quite challenging and it requires a better combination between the theoretical knowledge and practical experience. In this dissertation, several kinds of RF front-end receiver architecture have been investigated.
For RF networks, a front-end includes tuner and demodulator functions. There is significant physical interaction between both AGC, RF tuning and filter bandwidth selection via dedicated analog control signals from demodulator IC to tuner IC. Creating efficient and high-performance integrated circuits for these high carrier frequencies is very challenging. At the same time, one can observe a clear move of wireless communications solutions into the commodity markets. Consequently, size and cost become key parameters for design and implementation.
These conflicting requirements are from all times – the design of e.g. wireless networks has always turned around striking a balance between capacity, coverage, quality, and costs. Network planners know that fixing three of the design parameters results in an outcome for the remaining one. In case all parameters are fixed, the solution space may turn out to be empty.
In this thesis, we discuss the digital satellite receiver taking into account the most important limitations of the analog RF front-end such as I/Q gain and phase imbalance, non-linear distortion, phase noise and direct current (DC) offset. The aim of our work is to point out the potential of compensating RF impairments jointly with the fading effect by the usage of MATLAB simulation. Here, we have described many of the real world impairments that affect the performance of a satellite based transponder communication link. Optimum operating points and potential problems can be determined and corrected in the design process before costly mistakes occur in the finished product.
The main objective of this thesis is to provide an analysis of the impact of radio frequency (RF) front end impairments (I/Q gain and phase imbalance, phase noise, non-linear distortion and direct current offset) on the performance of a digital satellite receiver. The impact of RF impairments on a receiver depends on RF front-end topologies. The direct conversion receivers often referred to as zero intermediate-frequency (Zero-IF) receivers have become very popular in wireless technology.
Nevertheless, the RF impairments are much more critical in this case, as compared with super-heterodyne receivers for instance. In this thesis, we have presented a system approach to simulate and measure a complete transmission and reception scheme taking into account all parts of the structure, allowing a realistic link budget. Thus, the influence of RF impairments can be evaluated, depending on architecture choices and channel conditions.
To conclude, two countermeasures are thoroughly analyzed in this thesis:
1. Measuring I/Q Amplitude Imbalance.
2. Measuring I/Q Phase Shift.
The Device under test in this thesis is Caliber CR-9500CI digital satellite receiver. Our measurement strategy is focused on the reduction of the testing time. Nevertheless, the accuracy and tolerances of the results should be inside an acceptable range.
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