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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_271</title> <link rel="stylesheet" href="reset.css" type="text/css" media="all"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <table summary="top nav" border="0" width="100%"> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_270.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_271</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_272.html">next page ></a></td> </tr> <tr> <td id="ebook_page" align="left" colspan="3" style="background: #ffffff; padding: 20px;"> <table border="0" width="100%" cellpadding="0"><tr><td align="center"> <table border="0" cellpadding="2" cellspacing="0" width="100%"><tr><td align="left"></td> <td align="right"></td> </tr></table></td></tr><tr><td align="left"><p></p><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td align="right"><font face="Times New Roman, Times, Serif" size="2" color="#FF0000">Page 271</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td align="center"><font face="Times New Roman, Times, Serif" size="3"><img src="dfc613a2013f19798ded8bd034a6187a.gif" border="0" alt="0271-01.GIF" width="381" height="124" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td align="center"><font face="Times New Roman, Times, Serif" size="2">Figure聽7.13<br />Single-frequency聽base聽station聽design聽with聽correction聽filtering.聽Thick<br />lines聽represent聽vector聽variables,聽<img src="dc2204b6f1ad7b9e3d3759365aeaf528.gif" border="0" alt="C0271-01.GIF" width="42" height="15" />,聽and聽<img src="19f47eff1d30f783314822ba1608e028.gif" border="0" alt="C0271-02.GIF" width="43" height="16" />.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">The state-space model is therefore</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="7592ad4d5726bbef05df92067b676749.gif" border="0" alt="0271-02.GIF" width="364" height="108" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">where </font><font face="Symbol" size="3">t</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>M</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> is of the order of minutes of </font><font face="Symbol" size="3">t</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>i</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> is of the order of hours. The spectral density of the white-driving-noise vector is selected to match the steady-state covariance (see the example of Sec. 3.4.4) of the (uncorrected) acceleration (i.e., <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>a</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">), multipath (i.e., <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>M</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">), and ionospheric states (i.e., <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>i</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">): diag(Q</font><font face="Symbol" size="1"><sub><i>w</i></sub></font><font face="Times New Roman, Times, Serif" size="3">) = 2[0, 0, <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>a</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">/</font><font face="Symbol" size="3">t</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>a</i></sub></font><font face="Times New Roman, Times, Serif" size="3">, <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>M</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">/</font><font face="Symbol" size="3">t</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>M</i></sub></font><font face="Times New Roman, Times, Serif" size="3">, <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>i</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">/</font><font face="Symbol" size="3">t</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>i</i></sub></font><font face="Times New Roman, Times, Serif" size="3">, 0].</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Figure 7.13 shows in block diagram form the implementation of the single-frequency base station that incorporates filtering to reduce the effects of code multipath and measurement noise. Note that the clock bias estimation portion of the implementation is identical to that of Fig. 7.12.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Figures 7.147.19 show performance plots for a single-frequency base station, assuming perfect modeling. A complete covariance analysis including error budgets and sensitivity analysis is not included. These figures were generated by propagation of the Kalman filter covariance equations under the following assumptions. Single-frequency code and phase measurements were processed at a 1.0 Hz rate for 160 min. The measurement-noise standard deviations were 0.5 m for code measurements and 0.01 cycles for phase measurements. These are typical values for receivers. More expensive receivers would result in smaller errors, especially in the code measurements. The steady-state values for the (uncorrected) acceleration and ionospheric states were defined to be <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>a</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3"> = 1.0 脳 10</font><font face="Times New Roman, Times, Serif" size="2"><sup>-4</sup></font><font face="Times New Roman, Times, Serif" size="3"> (m/s</font><font face="Times New Roman, Times, Serif" size="2"><sup>2</sup></font><font face="Times New Roman, Times, Serif" size="3">)</font><font face="Times New Roman, Times, Serif" size="2"><sup>2</sup></font><font face="Times New Roman, Times, Serif" size="3"> and <i>P</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>i</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3"> = 100.0 m</font><font face="Times New Roman, Times, Serif" size="2"><sup>2</sup></font><font face="Times New Roman, Times, Serif" size="3">. The five different plots in each figure correspond to the results of five different simulations. Each simulation used a different PSD for the code multipath driving noise. From bottom to top on each figure the plots correspond to steady-state (uncorrected) multipath errors with standard deviations of 0.1, 0.5, 1.0, 2.0, and 3.0 m.</font><font face="Times New Roman, Times, Serif" size="3" color="#FFFF00"></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table><p><font size="0"></font></p>聽 </td> </tr> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_270.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_271</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_272.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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