Tomas Mikulasek

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A 2 × 2 microstrip patch antenna array fed by a substrate integrated waveguide (SIW) feeding network for 24-GHz radar applications is proposed in this letter. The microstrip patches are aperture-coupled with the feeding network consisting of a perpendicular coax-to-SIW transition and two Y-junction power dividers. The antenna design is performed in the full-wave electromagnetic solver ANSYS HFSS and verified by measurement. At the operation frequency 24 GHz, a fabricated prototype has a gain of 11.1 dBi and a low sidelobe level below -22 dB in the E-plane and -33 dB in the H-plane.

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This contribution documents and discusses recent wideband radio channel measurements carried out in the intra-vehicle environment. Channels in the millimeter-wave (MMW) frequency band have been measured in 55-65 GHz using open-ended rectangular waveguides. We present a channel modeling approach based on a decomposition of spatially specific Channel Impulse Responses (CIRs) into the large and small scale fading. The decomposition is done by a Hodrick-Prescott filter. We parametrize the small scale fading utilizing Maximum-likelihood estimates for the parameters of a generalized extreme value (GEV) distribution. The large scale fading is described by a two dimensional polynomial curve. We also compare simulated results with our measurement exploiting two-sample Kolmogorov-Smirnov test.

2 Microstrip Patch Antenna Array Fed by Substrate Integrated Waveguide for Radar Applications

This paper aims to present a simple but robust model characterizing the frequency-dependent transfer function of an in-vehicle ultrawideband (UWB) channel. A large number of transfer functions spanning the UWB (3–11 GHz) are recorded inside the passenger compartment of a four-seated sedan. It is found that the complex transfer function can be decomposed into two terms, the first term being a real-valued long-term trend that characterizes frequency dependence with a power law and the second term forming a complex correlative discrete series that may be represented via an autoregressive (AR) model. An exhaustive simulation framework is laid out based on empirical equations characterizing trend parameters and AR process coefficients. The simulation of the transfer function is straightforward as it involves only a handful of variables; however, it is in good agreement with the actual measured data. The proposed model is further validated by comparing different channel parameters, such as coherence bandwidth, power delay profile, and root-mean-square delay spread, obtained from raw and synthetic data sets. It is also shown how the model can be compared with existing time-domain Saleh–Valenzuela-influenced models and related IEEE standards.

In-Vehicle mm-Wave Channel Model and Measurement

A microstrip patch antenna fed by Substrate Integrated Waveguide (SIW) is presented in this paper. The antenna operates in centimeter-waveband, at 9 GHz frequency. In the first step, the antenna is modeled in Ansoft HFSS. Influence of the most important parameters on the return loss of the antenna is investigated. In the second step, the final model of the antenna is simulated, fabricated and measured. At the operating frequency, the antenna reaches 8.8% impedance bandwidth (for s 11 better than −10 dB) and 8.2 dBi gain.

Frequency-Domain In-Vehicle UWB Channel Modeling

This contribution documents an ultra-wide band (UWB) channel measurement performed in an in-vehicle environment for the frequency range 3-11 GHz. An emphasis is placed into an evaluation of a spatial consistency of measured channel characteristics in terms of Pearson correlation between measured channel impulse responses (CIRs). Moreover, the measured CIRs are reproducible via a two-part exponentially decaying envelope-delay profile (EDP). The small scale variation of received signal is parametrized utilizing a random process obeying the generalized extreme value (GEV) distribution. Validation of the channel model is demonstrated utilizing a two sample Kolmogorov-Smirnov (K-S) test.

Microstrip patch antenna fed by Substrate Integrated Waveguide

The randomness in ultrawideband channel for small positional variations around a car, parked in an underground garage, is reported. Keeping the receiver fixed at the conventional rooftop antenna location, the transmitter location is changed to study the variations against distance, angle, and height. The path loss is found to be monotonically increasing with distance, but varies randomly with angle and height and thereby renders signal-strength-based ranging inaccurate for such scenarios. On the other hand, the first peak can reliably provide distance estimate irrespective of transmitter angle or height. The number of clusters in the delay profile reduces with distance, but the shape of the profile remains fairly consistent across angle. The Saleh–Valenzuela parameter values also vary with distance and height, but their average values are close to the IEEE 802.15.3 standard.

In-vehicle UWB channel measurement, model and spatial stationarity

A comparison of two variants of CLEAN, a time-domain serial subtractive deconvolution algorithm, is presented. Appropriate statistical metrics for assessing the relative merit of the deconvolution technique are identified in the context of intra vehicle ultra wide band transmission, and the better variant was selected based on its performance over a standard IEEE channel simulation testbed. The chosen method is then applied to extract important channel characteristics for a real-world channel sounding experiment performed inside a passenger car.

UWB measurements for spatial variability and ranging: Parked car in underground garage

This paper provides a comparison of a real-world intra-vehicular radio channel measurements of the ultra-wide frequency bands, namely the 3-11 GHz and the 55-65 GHz. The measurement campaign was performed utilizing a vector network analyzer (VNA) and a frequency domain method ensuring a high dynamic range of 70 dB and a frequency resolution of 10 MHz. An inverse Fourier transform is exploited for a transition of the measured data into the time domain and to obtain a channel impulse response (CIR). A delay spread and a path loss are derived and compared. Measured data is freely available online: http://www.radio.feec.vutbr.cz/GACR-13-38735S/.

CLEAN algorithms for intra-vehicular time-domain UWB channel sounding

The article presents out-of-vehicle channel measurement results in the 5.8 GHz frequency band which is used in the IEEE 802.11p standard. Experiments for two different distances and three different angles around the parked car are carried out. It is found that a two-term exponential decay model can satisfactorily describe the mean measured power delay profiles. For each measurement, this large scale variation is used to calculate the corresponding channel impulse response and to construct a Rician tap-delay multipath channel model. Bit error rate (BER) performance for each measured location is then evaluated through MATLAB based simulation. The simulation results indicate that the error performances do not vary much and it is possible to determine an average BER curve for the whole set of data.

Intra-Vehicular Path Loss Comparison of UWB Channel for 3-11 GHz and 55-65 GHz

In this paper, a substrate integrated waveguide linearly polarized rectangular ring slot antenna is presented for centimeter wave applications. Its basic properties are described. The designed antenna at the frequency 10 GHz achieves the impedance bandwidth 4.3 % (the measured value), and the gain 8.2 dBi (the simulated value in Ansoft HFSS).