BAW filters offer high selectivity at 2.4 GHz

EDN Europe, 04 Jun 2008

US-based company Skyworks Solutions has announced a series of parts that it believes will be required to enable the co-existence of wireless LAN and WiMax networks. The bulk-acoustic-wave (BAW) devices are band-pass filters that operate at the 2.4-GHz frequencies used by both standards, and that provide the selectivity to reject signals in nearby channels. The company intends the devices for applications in customer-premises equipment. Skyworks develops integrated RF solutions for a
array of air interfaces and system architectures, and entered the BAW filter market in 2005.
The SKY33107 is a WiFi reject/WiMAX pass, and the SKY33108 is a WiFi pass/WiMAX reject, BAW filter. Both 3 x 3 mm devices have very low in-band insertion loss and input and output return loss. They also exhibit excellent rejection – in the 2.4 gigahertz (GHz) WLAN band for the SKY33107, and 2.495-2.690 GHz WiMAX band for the SKY33108. The SKY33107 is intended for use in 2.495-2.690 GHz WiMAX band transmitter applications which also contain WLAN 802.11 b, g, n transmitters, while the SKY33108 is targeted at 2.400-2.473 GHz WiFi band transmitter applications which also encompass 2.495-2.690 GHz WiMAX transmitters. Both filters can operate over -20 to 85° C.
BAW filter technology, Skyworks says, is suited to the provisions of high selectivity since it works by transducing electrical signals into very low loss (high-Q) resonant acoustic vibrations in piezoelectric structures. Skyworks fabricates BAW filters using semiconductor wafer fabrication techniques similar to those it employs to manufacture heterojunction bipolar transistor (HBT) PAs and pseudomorphic high electron mobility transistor (pHEMT) switches. Engineering samples are available now.