Measurement Journal Issue 6

Reacquisition time: This test establishes the time required to reacquire a navigation ﬁx following a short blockage of all GPS signals during normal operation. The method of blockage can be achieved in a number of ways. The two most common ways would be to attenuate the signal by inserting an attenuation of at least 60 dB in the feed line or to disconnect the feed line from the simulator to the receiver. Measurement data is similar to the TTFF measurement. The GPS simulation is ﬁrst started on the E4438C. The GPS receiver is turned on and allowed to achieve a location ﬁx. Next the GPS signal is interrupted by pressing the RF On/Off button on the E4438C. The signal is then restarted by pressing the RF On/Off button to simulate a short signal blockage. The reacquisition time is the interval between the reconnection of the GPS signal and the ﬁrst-valid navigation data point derived from the simulation. At least 50 valid reacquisition samples should be collected. The mean, minimum and maximum values for these samples are analyzed and the standard deviation computed. Static navigation accuracy: The objective is to characterize the accuracy of the receiver location ﬁ x with respect to the simulated location. In this test, a static (non-moving) scenario is used as the GPS simulated signal. The GPS simulation is ﬁrst started on the E4438C. The GPS receiver is turned on and allowed to achieve a location ﬁx. Valid 2D or 3D navigation data points, as deﬁned by the GPS receiver, are counted over the GPS simulation period. The interval of the data collection is based solely on the receiver’s outputnavigation data rate. Typical GPS receiver evaluation software provides location ﬁx information. This data, usually longitude, latitude and altitude information, can be converted to Earth-centered, Earth-ﬁxed (ECEF) Cartesian coordinates for evaluation of the simulated, versus calculated, GPS receiver locations. ECEF coordinates (x, y and z) of a point P can be determined from its geodetic coordinates (F, l and h) using the following algorithms.2 x = (R + h) cos F cos l y = (R + h) cos F sin l z = (R + h – e2R) sin F where R = a/(1 – e2 sin2 F)1/2 F is the geodetic latitude l is the geodetic longitude h is the altitude a is the ellipsoidal equatorial radius e is the eccentricity of ellipsoid b is the ellipsoidal polar radius, b = a(1 – e2)1/2 Agilent Measurement Journal 22

Table of Contents Feed for the Digital Edition of Measurement Journal Issue 6

Measurement Journal Issue 6 Using a Few Words to Convey a Deeply-Held Spirit Charting a Unique Path to Technology Innovation Contents Announcing First Commercial GC/MS Metabolites Library Assessing Nonlinear Behavior Testing Combines Form and Function Testing Multiplay Networks Higher Sensitivity LC/MS Easing Military Radio Test Stepping Up Calibration Accuracy Increasing Spectrum Analyzer Bandwidth 3GPP Tool Supports TS 36 Standards The Olympic Story Spotlights Agilent's Continuing Contribution to Technology Innovation Ensuring a Level Playing Field in Competitive Sports GPS: Coming of Age Resolving Design Issues in HSPA Mobile Devices Achieving Accurate Results with Oscilloscope-Based Jitter-Analysis Software RF Handheld Testers Guarantee Traffic Stability Under Olympic-Sized Stress Conditions Utilizing LAN-Based Instrumentation to Measure Total Harmonic Distortion in Remote Facilities IMT-Advanced: 4G Wireless Takes Shape in an Olympic Year EPO Doping: A Speed Engine, Turbo-Charged by Chemistry

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