Abstract-We present an analysis of the propagation of measurement uncertainty in microwave transistor nonlinear models. As a case study, we focus on residual calibration uncertainty and its effect on modelled nonlinear capacitances extracted from small-signal microwave measurements. We evaluate the uncertainty by means of the Polynomial Chaos Expansion (PCE) method and compare the results with the NIST Microwave Uncertainty Framework, which enables both sensitivity and Monte-Carlo (MC) analyses for uncertainty quantification in microwave measurements. We demonstrate that, for the considered application, PCE provides results in agreement with classical MC simulations but with a significant reduction of the computational effort.Index Terms-Microwave measurements uncertainty, FET, nonlinear modeling, polynomial chaos expansion.
The Internet of Things requires highly efficient ultra-wideband antenna systems that yield high performance at low manufacturing cost. Therefore, a novel ultra-wideband circular air-filled substrateintegrated-waveguide (AFSIW) cavity-backed annular slot antenna is proposed that enables straightforward integration into general-purpose materials by means of standard manufacturing techniques. The cavity top plane, serving as antenna aperture, contains two concentric annular slots, both split into two by shorting tabs that create a virtual electric wall. This enables the generation of a TE 11,slot even mode in both parts of each annular slot, giving rise to a conical radiation pattern. By exciting two such modes and judiciously positioning their resonance frequencies, all the unlicensed national information infrastructure (U-NII) [5.15-5.85] GHz radio bands are covered. The annular slot antenna is then made polarization reconfigurable through an innovative excitation of the slot modes by replacing the shorting tabs with four pairs of the PIN diodes. These dynamically switch between two orthogonal linear polarizations by changing the dc control current at the antenna RF port through an external bias tee. This simple, yet effective, bias network enables the integration of all polarization control electronics inside the antenna cavity to protect them from environmental effects. A low-cost antenna substrate was realized through standard additive manufacturing in a 3D-printed substrate, while a standard high-frequency laminate was used to implement the upper conducting plane containing the radiating elements and the polarization reconfiguration electronics. The antenna features an impedance bandwidth of 0.93 GHz, a front-to-back ratio of 14 dB, a total antenna efficiency higher than 95%, and 4.9 dBi gain for each polarization state.INDEX TERMS Additive manufacturing, air-filled substrate-integrated-waveguide (AFSIW), cavity-backed slot antenna, circular cavity, in-cavity electronics, PIN diode, partially-filled circular waveguide, polarization reconfiguration, reconfigurable antenna, substrate-independent, ultra-wideband.
In this paper, we present an ultra-wideband impedance sensing board for the radio-frequency front-ends used in wireless units for the Internet of Things and the fifthgeneration wireless communication systems. We adopt as an impedance sensing board a six-port junction which was designed, fabricated, and tested experimentally in the frequency range from 5 GHz to 6 GHz. Moreover, the sensing board functionality was fully validated with load-pull measurements carried out in the same frequency range.
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