**6.1 Identify the main noise source**

202 Wireless Communications and Networks – Recent Advances

From the various platform noise measuring techniques described above, we can summarize

Fig. 31. NFS system and measurement setup.

Table 3. Measurement techniques comparison.

the comparison as Table 3.

The first step to solve the interference problem is to identify the main noise source, and then we can further to implement resolving techniques like filtering, shielding, and re-layout, etc. The procedure can be demonstrated below in Figure 32.

Fig. 32. Use built-in antenna to identify noise source from measured spectrum.

Those engineers who are responsible for resolving noise problem may add the copper foil or put an absorber to cover the IC, routing the antenna cable, re-installing the panel, plugging antenna connector to test port, and they may affect the antenna or noise test results after those activities. Therefore, the antenna VSWR characteristic must be checked before noise measurement. The VSWR measurement of antenna is a quick way to check if the antenna is still kept the same configuration as originally implemented, because 3D radiation pattern and efficiency measurements of antenna usually take 2~3 hours. However, the SNA option described early can provide an embedded VSWR bridge and therefore could automatically check VSWR of each measuring port before noise measurement as shown in Figure 33 for LTE band. There are two kinds of LCD panel testing fixture can be designed for different panel size as shown in Figure 34 and 35.

Fig. 33. VSWR of each measuring port before noise measurement for LTE band.

Fig. 34. LCD panel testing fixture integrated with LNA and SNA result for LTE.

Fig. 35. LCD panel testing fixture with LNA and antenna protected by dielectric material.
