Engineers at Fujitsu have developed 240 gigahertz bandwidth capable microwave receiver IC. The Indium Phosphide semiconductor-based receiver IC is a multistage amplifier with high sensitivity. It also features protection against amplifiers oscillator effect. The present 4G capable LTE supporting smart phones operate in the frequency bandwidth of 2 GHz. You can imagine the increase in data speed capability of smart phones if they are integrated with 240 GHz chips. High definition media files can be downloaded hundred times faster compared to the present-day smartphones. To increase the frequency bandwidth of RF receivers, engineers are basically using advanced a compound semiconductor material. Today's RF front end IC chips are built using Gallium Arsenide semiconductor material, they are not suitable for handling the millimeter wave RF signals. Indium Phosphide is a very good material for millimeter wave RFICs.
This IC's sensitivity is increased approximately 10 times to support reception of large data volumes by smartphones or other mobile devices using a compact antenna.
Fujitsu has presented this technology at a event called CSICS 2013, the Compound Semiconductor IC Symposium, held on October 13 in Monterey, California.
When you design an IC chip for receiving millimeter wave signal, designer has to take care of the plenty of leakage possibilities. The leaked signal causes oscillator effect. Fujitsu engineers have taken care of this signal leaking by aligning the input and output at points where the signal has no amplitude (It happens due to very short wavelength).
Fujitsu explains: The leaked signal from an amplifier will always have "antinodes" at specific sites where that signal is at its greatest amplitude, and "nodes" where it has no amplitude at all. If the amplifier's input pin is located in a leaked signal's antinode, then a stronger leaked signal will feed back into the amplifier, creating the oscillation effect . Conversely, if the input pin is located in a node, the leaked signal has no amplitude, and the amplifier will not re-amplify the leaked signal. Fujitsu has aligned the input pin and output pin with the nodes in the leaked signal . Connecting amplifiers designed this way into multiple stages results in high amplification ratios without an oscillator effect.
Aligning the input and output pins of the amplifiers with the nodes limits the dimensions of the amplifier, while the length requirements on the lines create another set of constraints, complicating the task of impedance matching. To resolve this problem, a U-shaped line was deployed and the length and width of the U were adjusted to enable impedance matching regardless of the limitations on the dimensions of the amplifier, describes Fujitsu.
Fujitsu has used impedance-matching technology to efficiently convey the output signal from one stage to the next. This produces a roughly tenfold improvement in receiver-chip sensitivity over previous designs.
Fujitsu is working to develop a compact package that integrates an antenna along with a receiver chip based on this technology, with the goal of conducting transmission testing by sometime in 2015 and practical applications around 2020.