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Abstract-This contribution analytically studies the influence of IQ mismatch on the performance of multiple-antenna orthogonal frequency division multiplexing (OFDM) systems based on the zero-IF architecture. First a system model for such a multiple-input multiple-output (MIMO) OFDM system experiencing both transmitter (TX) and receiver (RX) IQ imbalance is derived. This is used to obtain analytical expressions for the probability of error in symbol detection for MIMO OFDM systems in Rayleigh faded multipath channels. The derived results can be used to find matching specifications for the TX-and RX-branches for different multicarrier MIMO systems. It is concluded that in fading channels RX IQ imbalance is on average more destructive than TX IQ imbalance. Additionally, it is concluded that the addition of extra RX antennas is beneficial to reduce the dependence on RX IQ imbalance, but increases at the same time the impact of TX IQ imbalance.

Background/purpose Millimeter‐wave reflectometry is a potentially interesting technique to analyze the human skin in vivo in order to determine the water content locally in the skin. Purpose of this work is to investigate the possibility of skin‐tissue differentiation. In addition, it addresses the influence of the pressure of the probe on the skin, the influence of an air gap between probe and skin as well as the influence of a bandage between probe and skin. Methodology Reflection coefficients at various positions on the skin are measured in the 40–60 GHz range and the examined effects are quantified in terms of magnitude and phase of the reflection coefficient. Also, the possibility to perform tissue differentiation is quantified. Results It is indicated that differentiation of skin tissue can be performed on the basis of the magnitude of the reflection coefficient provided that no air gap exists between probe and skin. The influence of probe pressure can be substantial, in particular for phase measurements. The presence of an air gap between probe and skin reduces the differentiation capability of the considered measurement technique, whereas a bandage between probe and skin did not significantly affect the differentiation power. Conclusion The results of this work confirm the potential of millimeter‐wave reflectometry for determination of the water content in skin tissue which may lead to interesting applications as early detection of skin cancer and through‐bandage monitoring of wounds.

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The dielectric properties of glucose solved in pure water as well as in a physiological solution have been measured. The results are considered in the context of noninvasive diabetes control. At least 0.002 percent measurement accuracy is required to achieve the same accuracy as obtained with traditional finger pricking.