Gallery: Cool circuits in evidence at the 2015 International Microwave Symposium

Making antennas match

ON Semiconductor showed a variation on its tunable RF components designed to automatically compensate for the changing loads on cell phone antennas as might arise when someone moves their hand around the phone. The company has fielded these components since 2013. At IMS it showed an example of a phone able to handle loading at 4G frequencies. The autotuning circuit basically consists of a directional coupler, a capacitor that changes its capacitance depending on a dc bias voltage, and a controller specifically designed to control the capacitor. The capacitance changes to minimize the amount of energy reflected from the antenna.
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