Compact BAW Filters Help Separate WiMAX And WLAN

Sept. 16, 2008
These miniature high-performance BAW bandpass filters help WiMAX and WLAN signals to coexist within their closely located wireless band allocations.

Wireless networks bring a great deal of convenience to the home, office, and factory, although available spectrum has always been a valuable commodity. In the case of wireless local area networks (WLANs) and high-speed WiMAX networks, for example, devices occupy the same general bandwidth centered at around 2.5 GHz. To keep things straight, Skyworks Solutions has developed a pair of high-performance filters based on bulk-acoustic-wave (BAW) technology. In essence, model SKY33107 passes WiMAX signals from 2.495 to 2.690 GHz with minimal loss while rejecting WLAN signals from IEEE 802.11b/g/n wireless transmitters operating from 2.400 to 2.473 GHz. Conversely, model SKY33108 passes WLAN signals with minimal attenuation while suppressing signals from WiMAX transmitters (see figure).

Model SKY33107 is designed to pass WLAN signals and stop WiMAX signals. When tested with 0-dBm signals matched to the filter's 50-ohm ports, it shows insertion loss of typically 2.5 dB for the passband of 2.400 to 2.473 GHz, with passband ripple of typically 0.5 dB. The filter, which is designed for operating temperatures from -20 to +85C, exhibits passband return loss of typically 12 dB and is rated for withstanding voltages to 100 V. Over the frequency band of 2.495 to 2.690 GHz, the BAW filter typical rejects WiMAX transmitter signals by 40 dB. Available in a lead-free, RoHS-compatible package, the model SKY33107 BAW filter is designed to handle maximum input signal levels to +28 dBm. The filter meets Class 1 electrostatic-discharge (ESD) requirements per Human Body Model (HBM) conditions.

Model SKY33108 is designed for use in the 2.495 to 2.690 GHz WiMAX band for transmitter applications that also contain WLAN IEEE 802.11b/g/n transmitters. When tested with 0-dBm input signals matched to the 50-ohm impedance of the filter's ports and at room temperature (+25C), the filter shows typical insertion loss of only 2 dB across the WiMAX transmitter passband of 2.495 to 2.690 GHz with passband ripple of typically only 0.5 dB. The passband return loss is typically 12 dB. The rejection of WLAN transmitter signals across the frequency band from 2.400 to 2.473 GHz is typically 40 dB. As with the model SKY33107 filter, the SKY33108 is rated for withstanding voltage to 100 V and has a maximum input-power rating of +41 dBm. It is also rated for Class 1 ESD per the HBM and is designed for operating temperatures from -20 to +85C. It is also available in a lead-free, RoHS-compatible package measuring a mere 3 x 3 mm.

The tiny filters are fabricated using semiconductor wafer fabrication techniques similar to those already used at Skyworks. The use of semiconductor fabrication methods results in low cost and repeatable performance from lot to lot. In support of higher volumes, Skyworks recently announced that it had approved the Taiwanese foundry, WIN Semiconductors (www.winfoundry. com), as a foundry partner and had started working with WIN to provide Skyworks with GaAs foundry processing services to meet heightened product demands. Skyworks Solutions, Inc., 20 Sylvan Rd., Woburn, MA 01801; (781) 376-3000; Fax: (781) 376- 3100; E-mail: [email protected]; Internet:

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