An attempt is made to receive pulsar signals at a frequency (22 MHz) lower than they have been received before. The problem of high galactic background radiation is the dominant one. The receiver used optimizes the ratio of signal to sky background noise. The technique uses the property that pulsar signals are dispersed by intervening electrons. Using the known dispersion relation it is possible to predict the phase of the pulsar signal at one frequency (22 MHz) if it is known at another frequency (150 MHz). The receiver then tracks the pulse in frequency vs. time with a bandwidth which is small enough to match the instaneous bandwidth of the signal. Although it was found that pulsar signals from CP 1919 are still too weak to be received on such a system, an upper limit to their strength was obtained by measuring its sensitivity. At the time of observation (August, 1969) the signal strength at 22 MHz, averaged over 2600 pulses, was less than 1.0 x 10⁻²⁶ joules per m² of capture cross-section per unit bandwidth. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

M.Ing. (Electrical & Electronic Engineering) / Please refer to full text to view abstract

M.Ing. (Electrical & Electronic Engineering) / Please refer to full text to view abstract

Metal detection systems currently available to the general public ordinarily verify the presence of conductive material, not the shape. Shape detection is important for discrimination between dangerous and benign items. Test setups are developed useful for identifying the value of microwaves for shape detection behind selected material types. The behavior of this electromagnetic energy in homogeneous, isotropic, locally linear, temporally dispersive material is examined in the time and frequency domains. The results of the evaluations determine the behavior of continuous-wave microwave radiation and microwave pulses in such media. A unique method is then developed for detecting the shape of concealed conductive objects utilizing pulsed microwave ultrawideband spectra.

No description available.

No description available.

No description available.

No description available.

This report summarizes the design of a 25kW peak power pulse modulator for an airborne medium--range weather radar. It is the purpose of the modulator to collect and store energy over a certain time period and to form this energy into a short, high-power pulse. The modulator is required to drive a coaxial magnetron with a pulse of 5kV at 5A. System considerations make a pulse width of 3.5us and repetition rate of 99Hz necessary. The pulse is generated in a line-type pulse circuit which utilizes an SCR as a switching device. It is shown that a solid-state modulator can use a commercial grade SCR for the pulse generation. Although currents of 100A are switched, the instantaneous power dissipation in the SCR is reduced significantly through the use of a saturable delay reactor. A pulse transformer is used to achieve maximum power transfer from the modulator to the magnetron. The pulse transformer is insulated with semi-rigid epoxy. Corona generation is avoided by limited the voltage gradients in the insulation to 80V/mil.

Ultra wideband (UWB) is a promising technology for short range and high-speed wireless communications such as home entertainment, wireless video downloading, wireless LAN, wireless USB and so on. This dissertation studied several important issues in the application of UWB technology and its contributions are summarized as follows. First, a 2-stage optimal UWB pulse shaping filter design procedure is proposed, which not only satisfies the FCC transmission spectral masks but also suppress the multiple access interference (MAI). The major advantages of the proposed joint optimization method are: (1) it has superior MAI suppression capability; (2) it can achieve the best system performance by optimizing transmitting and receiving filters jointly. Second, a pulse shaping optimizer is proposed to achieve the best received signal-to-noise ratio (SNR). Since the objective function of the SNR optimization has multiple maxima, genetic algorithms are adopted in this all-pass filter optimization. Third, a novel analytical method of assessing the narrowband performance degradation due to UWB interferences is proposed. This method models the UWB interferences as a composite signal of white Gaussian noise and jamming tones. Finally, a RAKE receiver simulation model under a realistic UWB channel is proposed and numerical results are presented. Overall, this dissertation investigates several important issues in the application of UWB technology, and provides some insights on the role of UWB technology in the evolving course of wireless communications. / Ph. D.