![]() ![]() I also encountered sporadic screen-refresh problems while I was resizing text, and the program occasionally truncated the text labels at the tops of the bars in one of my charts. Unlike other chart components, which display handles when you click on them, the chart background doesn’t give you any visual feedback to let you know when you’ve selected it. But to hide or reveal the chart’s legend or grid, you have to select options in the Data Viewer window there are no corresponding controls in any of the Inspector windows. For example, to set attributes for most chart elements, you first select the component with the mouse and then click on an icon to reveal an Inspector window (see “Inspector Gadgets”). If the file contains multiple charts, each one becomes a separate slide, and you can even choose which Keynote theme to use for the presentation.Ĭhartsmith’s chart-editing interface suffers from a few annoying inconsistencies. In addition to letting you export individual charts in several graphic formats, Chartsmith lets you save an entire document as an Apple Keynote presentation (mmh April 2003). Chartsmith also lets you drag entire charts into the document windows of other running applications - including Microsoft PowerPoint - in PDF or TIFF format. If you press the option key while you’re dragging the swatch, you can preview the effect before you commit. For example, you can drag a swatch from Chartsmith’s color palette onto any chart element to alter the element’s hue. All rights reserved.Any use is subject to the Terms of Use as given at the website.Chartsmith’s interface relies extensively on dragging and dropping. 26-5.Standing wave ratio (SWR) can be defined in terms of reflection coefficient:Downloaded from Digital Engineering Library McGraw-Hill (© 2004 The McGraw-Hill Companies. These points areplotted at “A” and “B” in Fig. Calculatethe reflection coefficient: pwr P ref(26-19)P inc pwr 2.8 W(26-20)10 W pwr 0.28.(26-21)The voltage reflection coefficient () is found by taking the square root of thepower reflection coefficient, so in this example it is equal to 0.529. (26-16)I incPower is proportional to the square of voltage or current, so:P pwr 2(26-17) pwr P ref.(26-18)P incExample: Ten watts of microwave RF power is applied to a losslesstransmission line, of which 2.8 W is reflected from the mismatched load. For voltage or current:and E refE inc(26-15)or I ref. These scales are calledthe radially scaled parameters and they are both very important and often overlooked.With these scales, you can determine such factors as VSWR (both as a ratioand in decibels), return loss in decibels, voltage or current reflection coefficient, andthe power reflection coefficient.The reflection coefficient () is defined as the ratio of the reflected signal to theincident signal. Notice that the upper half-circle is calibrated 0 to 180 and the bottomhalf-circle is calibrated 0 to 180, reflecting inductive or capacitive reactancesituations, respectively.Radially scaled parametersThere are six scales laid out on five lines (“D” through “G” in Fig. All rights reserved.Any use is subject to the Terms of Use as given at the website.Ĥ72 The Smith chartThe Smith chartcircuit at the load end of the line reflects the signal back toward the generator180 out of phase with the incident signal an open line (i.e., infinite impedance)reflects the signal back to the generator in phase (i.e., 0) with the incident signal.This is shown on the Smith chart because both scales start at 0 on the righthandend of the pure resistance line, which corresponds to an infinite resistance,and it goes half-way around the circle to 180 at the 0-end of the pure resistanceline. Recall from transmission line theory that a shortDownloaded from Digital Engineering Library McGraw-Hill (© 2004 The McGraw-Hill Companies. These scales are the relative phase angle betweenreflected and incident waves. Thus, 0.12 on the outer scale corresponds to (0.50–0.12) or 0.38 on the innerscale.The angle of transmission coefficient and angle of reflection coefficient scalesare shown in circle “C” in Fig. These two scales are complementary at allpoints. The outer scale is calibrated clockwise and it represents wavelengthstoward the generator the inner scale is calibrated counterclockwise and itrepresents wavelengths toward the load. The Smith chartSmith chart components 47126-4 Continued.Although both wavelength scales are of the same magnitude (0–0.50), they areopposite in direction. ![]()
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