PROJECT TITLE :
Toward Solving Multichannel RF-SoC Integration Issues Through Digital Fractional Division - 2016
In fashionable RF system on chips (SoCs), the digital content consumes up to 85percent of the IC chip area. The recent push to integrate multiple RF-SoC cores is met with serious resistance by the remaining RF/analog circuitry, that creates various sturdy aggressors and weak victims leading to RF performance degradation. A key such mechanism is injection pulling through parasitic coupling between various LC-tank oscillators plus between them and strong transmitter (TX) outputs. Any static or dynamic frequency proximity between aggressors (i.e., oscillators and TX outputs) and victims (i.e., oscillators) that share the identical die causes injection pulling, which produces unwanted spurs and/or modulation distortion. During this paper, we tend to propose and demonstrate a brand new frequency planning technique of a multicore TX where every LC -tank oscillator is separated from other aggressors beyond its pulling range. This can be done by breaking the integer harmonic frequency relationship of victims/aggressors within and between the RF transmission channels using digital fractional divider based on a phase rotation. Each oscillator's center frequency can be fractionally separated by ~28% but, at the identical time, both producing closely spaced frequencies at the part rotator outputs. The injection-pulling spurs are so so much away that they're insignificantly tiny (-eighty dBc) and coincide with the second harmonic of the carrier. This technique is experimentally verified during a 2-channel system in 65-nm digital CMOS, each channel comprising a high-swing category-C oscillator, frequency divider, and phase rotator.
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