Section 2.5. Summary

2.5. Summary

The measurement and simulation of indoor UWB channels are examined in this chapter. Both time domain and frequency domain measurement techniques are discussed. The advantages and disadvantages of each technique are pointed out. Time domain measurements are more intuitive and clearly illustrate the transient behavior of the channel response. However, the signal-to-noise ratio for time domain measurements is lower than that of the frequency domain results because of the smaller dynamic range of the time domain measurement setup. The chief advantage of the frequency domain method is its much larger dynamic range. In this method, the measurand is the channel transfer function, which is a complex quantity, requiring both magnitude and phase information. The difficulties associated with phase measurements for UWB channels involving long propagation distances is examined. A scalar frequency domain technique is presented in which the phase information is extracted from the magnitude data by means of the Hilbert Transform. Other important issues, such as triggering, calibration, interference, noise, and jitter, are also addressed. Sampled measured results in both domains are presented. Signal distortions due to the transmit and receive antennas, as well as the dispersive properties of building materials in the propagation channel, are pointed out.

The electromagnetic simulation of ultra wideband signal propagation in indoor environments is discussed. This simulation is based on ultra wideband ray tracing techniques and the uniform theory of diffraction. The simulation accounts for the radiation characteristics of the transmitting and receiving antennas and reflections, refraction, and diffraction of waves by the surrounding walls and objects in the channel. Frequency dependence of materials used in the structure of indoor channels, such as wood, drywall, bricks , and so on, can be accounted for in simulation of the channel. Sample simulation results for propagation of electromagnetic pulses with FWHM duration of less than 0.1 ns in a hallway are presented and compared with the corresponding measured results. It is noted that simulation and measured received signals are in good agreement.

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