Cellphone Theory And Testing

Arguably, measuring and tuning RF power-which is directly affected by cable loss-is the most value added service provided by Test Engineering. In general, cable loss is the loss associated with the RF cables, RF switches, and RF connectors between the DUT RF output and the ATE power-measuring instrument. Thus, cable loss maps the measured power on the ATE instrument to the DUT's RF output power.DUT RF output power (dBm)=ATE instrument power (dBm)+cable loss (dB).However, measuring DUT-RF output power (dBm) is not as precise as the above equation implies. In reality, it is imprecise and has many error sources which cause significant measurement uncertainty. The measurement uncertainties and how to reduce them are described and analyzed in detail by Bill Reid in his Global RF Calibration Error Model. doc. From this document we see, one possible contributor to measurement uncertainty is the ATE instrument itself, which has about+/-0.5 dB absolute error. To reduce the DUT RF output power (dBm) measurement uncertainty, the Cal-Cart includes the ATE instrument error (referenced to a power meter) as part of the cable loss value. Thus, the Cal-Cart cable loss definition is:Cal-Cart cable loss (or just cable loss) is the loss between the DUT and ATE instrument plus or minus the absolute instrument error (as referenced to a power meter).In some cases, the required absolute accuracy for DUT RF output power (dBm) measurements by our main line production ATE's is more stringent then any metrology laboratory is willing to sign up to and provide. Indeed the absolute measurement uncertainty requirement can be as little as+/-0.2 dB and this trend will only continue. Although it is difficult to achieve such accuracies, it can be done by: ●Measuring ATE cable loss with the Cal-Cart described in this manual on a fixed schedule determined by Gage R&R analysis.●Keeping the temperature inside production tester racks stable. Power measuring instruments used for production (VSA, Momentum, CMU200, etc) are very sensitive to temperature change.●Insuring the mobile phone (DUT) to tester RF interface has at least 20 dB return loss.Please note, RF couplers and some pogo pin RF interfaces cannot be calibrated because it is not practical to make the same cal-cart/tester interface as the phone/tester interface.We use these coupler/pogo pin RF interfaces in Final UI only and can use SPC to set a relative (with respect to FLAL) error compensation. Thus, it is critical that FLAL cable loss is measured to the absolute standard the cal-cart provides.Now, I'll try to introduce the relevant think—tester.Flash and alignment (Phase Id 335) test place is used for flash programming, accurate RF tests and alignments as well as for some baseband tests. Product (module) is placed to the tester by a manipulator or by an operator. The fixture inside the mechanic consists of two different plates:upper and lower fixture.Final and UI test (phase id 440) is used for assembled (final) product operation checking after final assemblyl. User interface is tested using keypad, vision system (cameras and vision card) and audio system. Product RF capabilities are tested using either a galvanic connection or a coupler. RF tests are only for operation checking, all critical and exact RF measurements are made in FLALI test place.Labeling test place (phase id 455) is used for selecting different language packages (programmed in panel flash), IMEI programming and type label printing. Label test queue may contain some tests, but if possible all tests should be done before this test phase.Base on the rapid of the cell phone's development, we have to increase the test step to match the increasing functions of cell phone. How do we handle the tester to test the cell phone faster? That's a very important thing. Actually, the old technique is not fit for the new situation. We have to find a new way to finish the new test. Non-signaling Test replace by old technique to become the main method in the cell phone business. It could be more quickly, more easily, and more effectively to finish the test. It's helping the mass production in technical aspects.