(A) CMOS OOK receiver design using spin torque nano oscillator

Abstract

Since Slonczewski proposed a new mechanism for exciting the magnetic state of a ferromagnet and a nano-structure that generates spin transfer torque in 1996 [1], various researches have been carried out to utilize this quantum mechanics effect efficiently. STT-MRAM and Spin-torque-nano-oscillators (or Spin-transfer-nano-oscillators, STNOs) are two representative applications using spin transfer torque. Especially STNOs have been investigated as one of the next-generation oscillators. Conventional LC-tank oscillators which are widely used in today’s wireless transceivers limit the possibility of shrinking the chip size. However, STNOs are normally 50 times smaller than the conventional LC-tank oscillators, and have wide frequency tuning range. With these two superiorities, STNOs can replace the position of LC-tank oscillators if STNOs make up for their low output power and high phase noise properties. This thesis presents a low-power OOK receiver for spin-torque nano-oscillator. The designed OOK receiver consisted of LNA, RF-amplifier, balun-amplifier, envelope detector and baseband amplifier. Each stage was designed and allocated considering the characteristics of STNOs. The first stage basically provided low noise figure to lower the whole noise figure of receiver. The LNA should be matched with wide frequency range to cover the oscillating frequency of STNOs. In addition, the gain boosting scheme was adopted to provide additional DC current path and increase trans-conductance. RF amplifier mixes series inductive LNA and resistive feedback LNA to take advantage of both topology. By designing series inductive resistive feedback LNA, it is possible to get low noise figure and high gain covering from 2 GHz to 3GHz. Balun amplifier generates differential output to drive differential input envelope detector. Since differential detector reduces ripple problem and enhance the sensitivity, balun amplifier is needed, and it shows 0.63dB gain error, and $6^\circ$ phase error. As mentioned earlier envelope detector adopted differential input and gain boosting scheme to enhance conversion gain. The last stage baseband amplifier consisted of comparator, common source amp, and output buffer. It was designed to demonstrate video module wireless communication. It shows 32.7dB voltage gain whose 3dB bandwidth is from 0.42MHz to 40 MHz. The proposed receiver consumes 27.35 mW including baseband stage. It was designed to cover LO carrier frequency from 2GHz to 3GHz, and LO power from -76dBm, and pulse data rate over 1Mbps. The receiver chip size is $1.415 mm^{2}$ including pads.