Toshiba today announced that it has developed a circuit technology that removes distortion in wireless transmissions. The technology can be directly integrated into a CMOS radio frequency (RF) power amplifier.
The new circuit will be unveiled on February 20, 2012 at the 2012 IEEE International Solid-State Circuits Conference (ISSCC) in San Francisco.
The various wireless communication standards deployed today use different frequency ranges, but in all of them the output radio frequency signals are amplified by power amplifiers designed for these standards.
For successful transmission to a base station, the amplitude of the signal, and therefore its power, is boosted by an RF power amplifier. As RF power amplifiers in mobile phones consume a lot of power, high efficiency is essential to extend the battery life.
The most widely used power amplifiers for mobile phones are compound semiconductors, but they are large and difficult to fabricate. CMOS could be a more compact alternative and easier to fabricate. However, CMOS power amplifiers require a distortion correction circuit that is relatively big, as it has to perform a huge number of calculations. Such a circuit is too big for integration into the power amplifier, and even for embedding into a mobile phone as a peripheral circuit.
Toshiba identified the threshold beyond which the distortion degrades the RF signal and has successfully created a simple distortion correction circuit, compact enough to be integrated into a CMOS power amplifier. Correction is applied only when the output power from the power amplifier exceeds 0.2W, the level required for communication with a relatively distant base station.
Toshiba claims that the CMOS power amplifier with the circuit improves the power efficiency by 1.4 times. It secures high level RF signal stability by correcting distortion automatically. Another advantage is the increased versatility secured by removing the need for an external correction circuit that allows simple integration into the system design of a typical mobile phone.
Toshiba will first apply the CMOS power amplifier to WCDMA devices and also aims to apply it to next-generation communications standards. Going forward, the company will develop related peripheral circuits, toward realizing even more compact, low power CMOS power amplifierse.