Measurement Journal Issue 6

Making the measurements Given the test setup and instrumentation previously described, the following tests can be performed to help evaluate GPS receiver performance and validate GPS products in a controlled environment.1 Time to first fix (TTFF): The test objective here is to measure the time required by the GPS receiver to achieve a GPS navigation fix from a cold start. A cold start is defined as a receiver that is turned on without current ephemeris data. Typically, a cold start can be achieved by a receiver that has been turned off for at least two hours. The TTFF is deﬁned as the time interval between the GPS receiver startup (power up) and the ﬁrst-valid navigation 3D-data point, derived from the simulation (Figure 6). The GPS simulation is ﬁrst started on the E4438C before the GPS receiver is turned on. At least 20 valid sample TTFFs should be collected. The mean, minimum and maximum values for these samples are analyzed and the standard deviation computed. Warm start time to ﬁrst ﬁx: The objective is to measure the time required by the GPS receiver to achieve a GPS navigation ﬁx from a warm start. This is similar to the cold-start TTFF test but, in this case, the receiver contains current ephemeris data for all satellites in the simulation. Typically, this can be achieved by a receiver that had previously been on and was then turned off for a short period of time. The GPS simulation is ﬁrst started on the E4438C. The GPS receiver is turned on and allowed to achieve a location ﬁx. This ensures the presence of current ephemeris data in the GPS receiver. Next, the GPS receiver is turned off for a short period of time and then on again. The time interval from this turn-on to a valid 3D location ﬁx is the TTFF. At least 50 valid sample TTFFs should be collected. The mean, minimum and maximum values for these samples are analyzed and the standard deviation computed. Figure 6. U-center software, printed with written permission from U-blox Time to ﬁrst ﬁx (TTFF) 3D ﬁx HDOP hoizontal dilution of precision Eight satellite identiﬁcation Satellite orientation C/No ratio 21 Agilent Measurement Journal

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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