Evaluation of nonlinear distortion in MIMO transmitters

In this paper, an evaluation of unwanted effects in Multiple Input Multiple Output (MIMO) transmitters is described. Complete 2×2 and 4×4 MIMO Orthogonal Frequency Division Multiplex (OFDM) transmitters are simulated for the purpose of quantifying all potential unwanted effects such as Power Amplifiers' (PAs) nonlinearity, linear and nonlinear crosstalk, and IQ modulator imperfections. An experimental analysis of a 2×2 MIMO transmitter using two-tones and WCDMA signal is presented.

Nonlinear distortion evaluation of reconfigurable RF circuits in wireless communication systems

A compact highly linear microstrip dual - mode optically switchable filter and a reconfigurable power amplifier are presented. The key characteristics of the dual - mode switchable filter are investigated and described. A second order filter design procedure is outlined to facilitate the realisation of Butterworth and Chebyshev functions. The proposed filter was built and tested with an optical switch, which comprised of a silicon dice acti vated using near infrared light. The measured and simulated results are in good agreement. The measured insertion loss in the ON state was 3.0 dB the isolation in the OFF state was 45 dB at the centre frequency. An evaluation of filter distortion is presen ted for digitally modulated M - QAM and M - QAM OFDM singals.

Qualified exceptionalism: the US Congress in comparative perspective

The framers of the American Constitution devised a singular bicameral legislative body, which invested substantial power in both a broadly representative lower chamber and a second "deliberative" chamber that was both insulated from the voters and unrepresentative of the population as a whole. Until the early 20th Century, the singular U.S. Congress changed little, but with growing national responsibilities, it sought to construct organizational forms that could address a consistently stronger executive. Since the 1980s, the Congress has relied increasingly on stronger parties to organize its activities. This development, embraced in turn by Democrats and Republicans, has led to changes that have edged the Congress in the direction of parliamentary democracies. We conclude this analysis has real, but limited utility, as congressional party leaders continue to barter for votes and, in the context, of narrow chamber majorities, often rely heavily on presidential assistance on divisive issues that are important to their party brand. Yet, the traditional features of the American separated system - bicameralism, the committee systems, and the centrifugal forces emanating from diverse congressional districts, increasingly complex policy issues, and the fear of electoral retribution - also remain strong, and effectively constrain the influence of leaders.'Qualified exceptionalism' thus most aptly describes the contemporary American Congress, which remains 'exceptional,' but less than unique, as it responds to many of the same forces, in some of the same ways (e.g., strong parties), as do many other representative assemblies around the world.

Compact high linearity switchable dual-mode microstrip bandpass filters

A compact highly linear microstrip dual-mode electronically switchable filter is presented. The key characteristics of the dual-mode switchable filter are investigated and described. A second order filter design procedure is outlined to facilitate the realisation of Butterworth and Chebyshev functions. The proposed filter was built and tested with NXP pin diode model BAP65-03. The measured and simulated results are in good agreement. The measured insertion loss in the ON state was 3.0 dB the isolation in the OFF state was 45 dB at the centre frequency. An evaluation of filter distortion is presented for digitally modulated 16 QAM and QPSK signals.

Compact tunable bandstop filters using defected microstrip structure for multi-standard wireless systems

A novel compact tunable bandstop filter using Defected Microstrip Structure (DMS) is presented in this paper. The structure utilizes a modified T shaped DMS which helps in miniaturization of the filter. To verify the concept, one such filter was simulated, designed, fabricated and tested. Measurements on a fabricated tunable filter confirm the accuracy of the design procedure. The tuning range of 20% is achieved, ranging from 2.26 GHz to 2.747 GHz. Tuning is achieved by using NXP BB179 varactor diode. A nonlinear distortion evaluation in a tunable filter was experimentally verified. Experimental verification shows the filter is highly linear.