Larger value of bias current leads to lower carrier lifetime (see expression for N ) and hence lower RC time constant. The capacitor in Figure 1(a) is effective during transient, but plays no role to limit the steady values of gain.A typical plot of frequency response versus the frequency of the modulating current is shown in Figure 7. When no parasitic element is included, the bandwidth is as high as 1.59 GHz, when I bias ϭ 40 mA, I ac ϭ 10 mA, input power ϭ Ϫ35 dBm and carrier lifetime ϭ 100 ps. With decrease of carrier lifetime dc gain as well as small signal gain decreases. When parasitic elements are included in the circuit, bandwidth is reduced, the values of which are mainly limited by the series resistance R s and total shunt capacitance C S . The parameters used are: R p ϭ 10 ⍀, L p ϭ 10 nH, R d ϭ 1 ⍀, R sh ϭ 1 M⍀, and reverse saturation current I s ϭ 0.3856 A. The frequency response has been shown in Figure 7 for C S ϭ 5 and 10 pF; the values of corresponding bandwidth are 0.64 and 0.395 GHz, respectively. These results could not be compared with any measured values due to nonavailability of data.
CONCLUSIONSA circuit model for TW-SLA has been developed using PSpice simulation techniques. In this circuit steady state and dynamic behaviors of SLA are modeled. The results of the circuit analysis are in close agreement with measured results and the results from numerical analysis of TW-SLA. The present time domain lumped circuit model can include electrical parasitics. As the rate equation parameters are related with the circuit elements the effects of changing them on the performance of TW-SLA can be examined quite easily. [7,8]. In particular, the advantage of wide-slot antennas is their wide operating bandwidth, especially for those with a modified tuning stub, such as the fork-like tuning stub [9 -13]. However, although many microstrip-fed wide-slot antennas have been proposed for triple-band applications, studies on the triangular slot antenna with fork-like tuning stub for triple-band applications are rare.In this article, we report the study of a new triangular slot antenna design with a fork-like tuning stub for triple-band operation, and we also investigated the radiation characteristics of such a design. The fork-like tuning stub studied here is all positioned within the slot region in the opposite side of the printed triangular slot. Through proper selection of the parameters of the fork-like tuning stub, it can be expected that the coupling between the fork-like tuning stub and printed triangular slot can be controlled more effectively, which makes triple-band operation possible with the triangular slot antenna. The antenna was fabricated with the use of a conventional RF-4 material, which is often used in making printed circuit boards and is therefore easy to manufacture. The results of the experiment conducted on the antenna's broadband impedance bandwidth, radiation pattern, and gain are discussed in detail below.
ANTENNA DESIGNThe schematic configuration of the proposed antenna design for...
