The aim of this paper is to show a detailed system design and bring out the challenges for cognitive transceivers in UHF band. An experimental cognitive transceiver is proposed based on commercially available components. The complete system aspects of a filterless implementation are discussed. Along with the intermodulation test for LTE specified by the 3GPP, the intermodulation of Tx leakage with the blocker arising in an FDD scenario is also dealt with. It is shown that even with highly linear RF components, the receiver cannot sustain Tx leakage. The blocker performance and the channel filtering requirements for a SAW-less transceiver are also shown along with an AGC algorithm for a steady SNR. With a brief system analysis, the effect of transmitter noise leaking into the Rx band and its impact on the sensitivity are discussed. The experimental setup has the provision to test the impact of full-FDD, half-FDD and TDD modes on the RF performance in a cognitive environment.
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