**3. RF coexistence problems on product performance [7]**

Due to the increasing add-on functions demand for consumer electronics, currently multiradios, such as WLAN, WWAN, GPS, Bluetooth, and even DVB-H modules, have all been crowdedly embedded and highly integrated in a tiny space of wireless communications platform. Therefore the wireless devices usually have been equipped with more than one antennas, the purpose is to fit for different communication system such as cellular mobile communications, wireless local area networking, and personal area networking. Under this situation, the performance of various kinds of wireless communications is usually degraded by the mutual coupling and interference of closely arranged antennas inside the mobile device. Since the RF modules co-existence has become a critical design problem for wireless communications, we will discuss the RF coexistence problems in this section.

#### **3.1 Isolation required for RF coexistence**

Platform noise usually raises the RF receiver noise floor and dramatically degrades system performance by push the Eb/N0 to the margin when there in-band or out-of-band interference exists. A frequent cause of poor sensitivity on a single channel, or a small number of channels, is due to receiver's in-band noise from broadband digital noise or spurious signals from other coexistent transmitters. We describe in this section the potential coexistence problem for multimode and multiband RF modules, and also illustrate below in Figure 16 the example of isolation required for various RF systems to achieve better service.

Fig. 16. Tx leakage in FDD system and isolation budget.
