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We investigated the robustness of the linear detector operating in a Gaussian environment in the presence of a mismatch between the design interference covariance matrix and the actual one. We have suggested that the Gaussian environment consists of a known colored clutter, a white noise and a strong unwanted periodical signal with unknown nonstationary power. It has been obtained the asymptotic inverse covariance matrix of the interference when the unwanted signal power tends to infinite. Using this formula we developed the asymptotic likelihood-ratio test (LRT). The performance of the new test statistic is analyzed and compared with well known optimal detector. The effect of the unwanted signal removing on the performance is evaluated for an example scenario.

The generalized likelihood ratio test (GLRT) for detecting a target signal in autoregressive (AR) noise whose covariance matrix is unknown is presented. We proposed a new constant false alarm rate (CFAR) matched detector whose structure does not depend on noise covariance matrix and level and its performance penalty is small. The evaluation of its performance shows that the loss measured with respect to the corresponding optimum structure with known noise covariance matrix is kept within a few dBs.

We conduct a simulation analysis for assessing the constant false alarm rate (CFAR) behavior of three coherent radar detectors in the presence of correlated Gaussian clutter with unknown covariance. We establish the conditions a detector must fulfil in order to ensure the CFAR property. We discuss several detectors with quasi CFAR property. The analysis of CFAR property and the performance analysis, which has been carried out in the presence of correlated Gaussian clutter with unknown covariance, show that the proposed detectors exhibit a quite acceptable loss with respect to optimum Neyman-Pearson detector

An OFDM transmitter with digital IF is demonstrated. The OFDM modulator is designed with an on-chip digital to analog converter. An image frequency mixer and an RF amplifier chain is realized partly with commercial GaAs MMIC circuits and partly with discrete transistors. About 10% power added efficiency in the power stage is achieved with ACPR level of -35 dB applying an A-class amplifier.

The goal of this work was to find out how the reflected PIM products are affected by different loading conditions at the 2nd and 3rd harmonics of excitation. The assembly, consisting of a GSM900 antenna and a microstrip feeding line with different impedance loads provided at 2nd and 3rd harmonics, was prototyped and measured with respect to PIM performance. As the PIM source, an SMA connector was used at the input of the antenna. Such a connector is very typical in patch antenna feeds and appears to be problematic in PIM sense.

This paper considers passive intermodulation (PIM) effects occurring in passive RF devices like mobile communication antennas where two or more high-power signals can simultaneously be present in the transmitter-receiver path. Due to nonlinear properties of the passive parts, the unwanted PIM components with combination of carrier frequencies may fall within the receive band. In this paper, the main causes of PIM are briefly reviewed. A description of the measurement procedure for testing the PIM performance is presented. In addition, a comparison between the PIM properties of five commercially produced antennas is performed in the GSM 900 frequency region.