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between Q avg and Q t can be obtained with only 1024 samples. This scheme is able not only to reduce the required memory size in the monitoring unit but also to provide estimation for the Q-factor faster than the conventional scheme. CONCLUSIONThis article proposes a novel sampling technique for improving the sampling uniformity with a low number of sampling points. The proposed technique can increase the measurement convergency and accuracy of Q avg by adding deterministic jitter to the sampling pulses. This makes the sampled histogram close to the one obtained with a large number of sampling points. Consequently, we can obtain faster Q-factor monitoring by reducing the data points in a histogram. It also reduces the hardware complexity by reducing the required memory size. The monitoring results are quite independent of the difference between the data rate and the sampling rate. ACKNOWLEDGMENTThis work is supported by the National Science Council (NSC) of Taiwan (R.O.C.) under grants NSC94-2213-E002-061 and NSC95-2221-E-002-194. In recent years, the use and interest in microstrip antennas (MSAs) has become widespread because of its significant merits of smallsize, light-weight, low-profile, low-cost, direct integrability with microwave circuitry, and the ability to conform to the surface of a host object. One of the most attractive features of the equilateral triangular microstrip antenna is that, the area necessary for the patch becomes about nearly half when compared wtih rectangular, square, or circular MSAs designed for the same frequency. Such features make MSAs useful for many applications in radar and wireless communication systems [1]. However, one of the principle limitations of MSAs is their narrow impedance bandwidth. Many techniques are available in the literature for the enhancement of impedance bandwidth of MSAs [2, 3]. One such technique is the use of aperture coupling. This technique is simple and more effective as it has the freedom in designing the required feed line to energize the elements for enhancing the impedance bandwidth. Since in the aperture coupling the microstrip-line feed and the antenna elements are separated by a ground plane, the effect of the feed line radiation on the antenna radiation characteristics is less, which improves the quality of antenna radiation pattern [4]. Further, the slot-loading technique is also effective in broadening the impedance bandwidth. Hence in this study, the aperture coupling and slot loading techniques has been used in designing the antennas. The experimental results are presented and discussed. DESIGNING AND EXPERIMENTAL DETAILSThe proposed antennas are designed using low cost glass epoxy substrate material S 1 of thickness h ϭ 1.66 mm and dielectric constant r ϭ 4.2. The use of high dielectric constant substrate material reduces radiation losses because most of the EM-field is concentrated in the dielectric between the conductive strip and the ground plane. Another benefit of having a high-dielectric constant is that the antenna size decreases ...

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