A single antenna with multiple feeds lets one antenna seem like two or more.
Most new wireless technology adopted today uses multiple antenna arrangements to implement diversity or multiple-input multiple-output (MIMO) techniques to improve link reliability, increased network capacity, or multiply data rate. Common examples include Wi-Fi, WiMAX, HSPA, and Long-Term Evolution (LTE). The key to adopting these techniques is to keep the antennas separated from one another enough so they don’t interfere with one another and reduce efficiency. This is easier to do in larger products like routers and access points that provide the multiple wavelength spacing that’s generally needed. But it’s a real problem in smaller devices with sleek designs like handsets.
SkyCross has solved this problem with its innovative Isolated Mode Antenna Technology (iMAT). Introduced in 2008, iMAT lets one antenna do the work of two or more antennas. It’s a takeoff of the popular meander line antenna (MLA) approach, which lets designers create smaller antennas in a limited space that have the same or better performance as common half- or quarter-wave designs. The iMAT design is a single antenna with two feedpoints that are selected to improve isolation between them. The multiple feedpoints also create two independent antenna radiation patterns that are in effect equivalent to those produced by separate antennas. Benefits include lower cost, simpler integration, and improved aesthetic design without sacrificing performance.
SkyCross’ first iMAT designs were initially incorporated into handsets and other portable devices. The company now has announced a design for 802.11a/b/g/n routers and access points (see the figure). It covers the 2.4-GHz and 5.1- to 5.9-GHz bands and implements MIMO in 802.11g/n designs.The company also has figured out how to eliminate the transmit/receive (Tx/Rx) switch in standard GSM/WCDMA designs. This means the iMAT antenna acts as two separate antennas—one for Tx and the other for Rx. SkyCross worked with Infineon Technologies to create this design for Infineon’s ultra-low-cost handsets targeting China, India, and other expanding economies. This approach is incorporated into Infineon’s XMM1020 platform, including the X-Gold102 chip, which puts all cell-phone functions including baseband, RF, power management, and two SIM interfaces on a single chip plus the SkyCross iMAT antenna.