industry  wireless networks


When GaAs technology is employed in antenna-switch design, the use of depletion-mode FETs and their biasing requirements limits the maximum achievable linearity for a given device size. On top of this,GaAs, unlike UltraCMOS, has a fundamental flaw – it lacks an insulating gate oxide


+75 dBm. We expect the linearity of our switches to continue to improve as we develop new generations of our UltraCMOS processes, as it has throughout the last five generations. For example, STeP5 switches have demonstrated third-order harmonic improvements of more than 30 dB over that of STeP2 switches.


In comparison, when GaAs technology is employed in antenna-switch design, the use of depletion- mode FETs and their biasing requirements limits the maximum achievable linearity for a given device size. On top of this, GaAs, unlike UltraCMOS, has a fundamental flaw – it lacks an insulating gate oxide. A metal semiconductor junction connects the gate to the channel, and gate current flows into the channel in both the on and off states. The upshot is that, at high power levels, when the GaAs FET gate voltage is modulated, distortion products increase and make it more difficult to meet LTE’s stringent linearity requirements.


One of the trends within the handset is an increasing number of signal paths. This drives the need for higher on-die isolation, which prevents the coupling and bonding of signals that can degrade a multi-band RFFE’s performance.


For example, in a multiband cellular handset, the PCS1900 transmit band overlaps with the DCS1800 receive band. Without isolation of 35 dB or better, unwanted in-band signals can pass through the filters and desensitize the receiver, resulting in dropped calls. To address this complexity, we launched the SP12T PE426171 switch, which maintains a minimum of 35 dB isolation at 2 GHz on all paths, in a form factor smaller than 3 mm2


.


This product and others in our portfolio meet the requirements of today’s 4G LTE networks. The SOS technology on which these products are created enables higher levels of integration, isolation, and linearity than other compound semiconductor products (see table 2 for details).


Table 2: Comparison of performance parameters of a commercially- available SP10T GaAs device to those of a commercially-available SP10T UltraCMOS device reveals that UltraCMOS technology performs better across many parameters.Note that the GaAs numbers are for two DIE – one being the RF switch and the other,the controller


Further reading 1.Andoh,Yoshiyasu (Navian Inc).RF Devices/Modules For Cellular Terminal Quarterly Market Report CY2012 2Q, Oct.5,2012: page 153.


January / February 2013 www.compoundsemiconductor.net 59


Switches are not the only SOS product that Peregrine manufactures for the RFFE. We also produce digitally tuneable capacitors, digital attenuators, mixers/upconverters, prescalers and frequency synthesizers.


Our portfolio of over 180 products enables designers to stay ahead of the curve with regard to advances in wireless communication devices and the infrastructure that supports them.


© 2013 Angel Business Communications. Permission required.


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