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4) If non-shielded antenna interconnects are used (like spring fingers or pogo pins) give these interfaces special attention with regard to exposure to noise sources.

Unfortunately, it is difficult or impossible to completely understand the full extent of any self-interference until a device is actually operating in the form-factor it will ultimately use. Therefore, it is critical to design shielding and other self- interference mitigations into the device from the very beginning and then to measure and analyze the self-interference situation as early as possible to avoid problems with receiver sensitivity during PTCRB testing.

4.5.3 Co-existence with Other Wireless Technologies Today, wireless devices often have multiple transceivers, operating in various bands: Wi-Fi (possibly with Multiple Input Multiple Output or MIMO), Bluetooth, ZigBee, GPS, 915 MHz ISM, other Part 15 devices all of which have antennas associated with them. On a small device, antennas must sometimes be placed very close to one another. Most of these wireless technologies will transmit their own intentional signals and also generate noise, both of which can interfere with the cellular band reception. Conversely, the cellular band transmitter generates large-amplitude signals (most often the largest signals a device produces) that can overwhelm a nearby receiver and cause severe distortion. The transmitter output of the typical cellular radio is high enough to interfere with a nearby Wi-Fi or GPS receiver, even though the frequency bands are separated by hundreds of MHz. As with self-interference, co-existence issues are difficult to quantify before a product is assembled and operating so good design decisions early in the process are important another reason to obtain qualified advice as early in a project as possible. Co-existence issues are also an opportunity for the radio module manufacturer to provide advice and lessons learned from experience.

5. Antenna Performance Measurements

Antenna Fundamentals Technical Brief


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