Spiral inductors with various metal fill-patterns under the spiral is fabricated with SOI CMOS technology and characterized up to 49 GHz. The impact of the fill on the inductor characteristics is found to be very small and changes can be attributed to the increase of parasitic capacitance. A simple model is proposed that can accurately estimate the increase of capacitance. A simple model is proposed that can accurately estimate the increase of capacitance by the fill. Design guidelinesfor optimizing fill patterns are recommended. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 462-465, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop. 10790 Key words: spiral inductors; fill patterns; RF CMOS; silicon-on-insulator; RF inductors INTRODUCTIONIn order to maintain the uniformity and reproducibility of the etching and chemical mechanical polishing (CMP) processes in today's deep sub-micron CMOS technology, incorporation of fill patterns [1,2] in the layout, especially on metal layers, is becoming a standard practice. In analog and RF CMOS circuits, spiral inductors are widely used. However, having conducting fill patterns under a spiral inductor has been considered undesirable based on the intuition that they can alter the field distribution and, therefore, the characteristics of the inductors. Although spiral inductors have been studied extensively for performance optimization [3], analysis of the effects of fill patterns on the same metal layer as the inductor was reported only recently [4,5]. In this work, the effect of fill at metal levels under the spirals, with various configurations on the inductors, is studied. Based on the test results, simple guidelines are provided for the design of the fill. INDUCTORS WITH FILL PATTERNSThe inductors were fabricated using a standard SOI process with three levels of metal [6]. The results reported here should also be applicable to the standard bulk-Si CMOS because the only difference is the presence of a 200-nm-thick buried oxide on top of the 10⍀-cm resistivity Si substrate. The thickness of the Al metal and the oxide between metal layers is 0.6 m. The thickness of the oxide between metal-1 and the Si substrate, including the buried oxide of the SOI wafer, is approximately 0.9 m. Only metal-3 is used as the inductor spiral. Floating fill, consisting of isolated patterns with no connection to ground, is chosen because its capacitance is smaller than that of grounded fill. Furthermore, it can be more easily generated as an add-on to the layout automatically. The purpose of this work is to examine the effect of fill; no attempt was made to optimize the fill patterns. All inductors have 5 turns with an inner diameter of 18 m, and the width and the spacing of the spiral lines are 3 m and 1 m, respectively. The inductor is configured as a one-port device with the center tap connected to ground. As shown in Figure 1, one type of fill consists of squares with a checkerboard arrangement. The side of the square and th...

An accurate and numerically efficient model for the rectangular microstrip antenna is presented. It concerns a transmission-line model which features the following three major improvements with respect to earlier such models: the mutual radiative coupling (both real and imaginary parts) between the equivalent slots is fully taken into account; the influence of the side slots on the radiation conductance is taken into account implicitly; simple analytic expressions are introduced for all relevant model parameters. By way of illustration, the new model is applied to antennas with a single microstrip feed line. Excellent agreement is shown with available experimental and theoretical results for the input impedance of a rectangular antenna. The improvements with respect to previous transmission-line models are illustrated for a square antenna.

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The paper describes a new design method for a wideband array of log-periodically scaled microstrip resonator antennas. The radiating elements are series-fed by a simple coplanar microstrip network. This network consists of an open-circuited feed line with a branch line connected to each radiating element. Both a network and a radiating model for the complete structure are explained. These models predict with good accuracy the input impedance and the radiation pattern as a function of frequency. The results for a 5-element 5-band antenna are presented as an illustrative example. This antenna combines a good impedance match (VSWR < 2.6) with a reasonable power gain in broadside direction (> 5.5 dB) over a 22% bandwidth. This means a tenfold increase in the bandwidth in comparison with a single microstrip resonator antenna. List of principal symbols BW C E,H >nK bandwidth capacitance of resonator electric, magnetic field dielectric constant of substrate absolute permittivity, permeability of free space frequency frequency, angular frequency, free space wavelength at resonance correction factor for surface roughness substrate thickness L, W Q.Q md D D O D P Pcu s t tan 5 x, y, z Z X / 4z m = resonator length, width = expansion factor of log-periodic structure = quality factor, radiation quality factor of resonator md = resonant, copper loss, dielectric loss, radiation resistance of resonator = reflection coefficient magnitude = copper resistivity = specified voltage standing wave ratio (VSWR) = copper thickness = loss tangent of substrate = cartesian co-ordinates = characteristic impedance of quarter-wave transformer line = input impedance of resonator 1