Simon C. Li

Effects of MgO tunnel barrier thickness on magnetohysteresis in perpendicularly magnetized magnetic tunnel junctions of GdFeCo/FeCo/MgO/FeCo/TbFe/Co

The effects of MgO tunnel barrier thickness on the magnetic-transport characteristics of perpendicularly magnetized magnetic tunnel junction device are explored. Saturation magnetization and initial switching field of the free layer decrease with MgO barrier thickness. Increased MgO thickness that extended interaction distance and diminished the influence from the magnetized pinned layer leads to a smaller initial switching applied field required for saturation. The oscillating dependences of the high coercivity of pinned layer and the low coercivity of free layer on MgO thickness are discovered. Moreover, an out-of-phase feature between both layers’ coercivity cyclic variation is exhibited. This unique cyclic varying of coercivity with MgO barrier thickness is revealed and analogous to the recent finding of the magnetoresistance’s periodic variation with MgO thickness.

Implementation of optimal PID control for chaos synchronization by FPGA chip

This paper is concerned with the design of a FPGA-based digital proportional-integral-derivative (PID) controller for synchronization of a continuous chaotic model. By using the EP algorithm, optimal control gains in PID controlled chaotic systems are derived such that a performance index of integrated absolute error (IAE) is as minimal as possible. To verify the system performance, basic electronic components containing OPA, resistor and capacitor elements are used to implement the chaotic Sprott circuits and the proposed digital PID controller is implemented by the FPGA technology. Finally, numerical and experimental results exemplify the synchronization procedure.

Dual Gain Mode Folded-Cascode (DGMFC) Front-End for LTE 4G Handset Receiver

A new 2.6 GHz CMOS front-end for LTE 4G handset receiver is proposed. LTE 4G handset receiver front-end using a dual gain mode folded-cascode (DGMFC) scheme provides a 15.3 dB/24.8 dB forward gain, noise figure of 4.5 dB/4.0 dB, and an IIP3 at -13.8 dBm/5.2 dBm with 13.7 mA/12.9 mA bias current from a 1.0-V power supply in low-gain/high-gain mode, respectively. The fully tunable 2.6-GHz receiver front-end is fabricated using 0.18 μm TSMC CMOS technology.

New Auto-Attenuator Controller for WLAN 802.11 b/g Repeater in WAP

A new low-noise, low-insertion-loss and high accuracy automatic-attenuator controller (AAC) to unify a constant power level into WLAN 802.11 b/g repeater is proposed. With the capability of self-detecting the output power of wireless access point, a feature of limiting the power rating to 802.11 b/g repeater is implemented. To serve equalization and prevent overloading for higher throughput, a regulated output power 5 dBm is set over the input power range 8-18 dBm while return loss is less than 3.5 dB at the center frequency 2.45 GHz.

A 2.4-GHz Low-Power Single-Chip Tunable CMOS Low-IF ISM Receiver

A low power single-chip CMOS single-conversion tunable low-IF receiver operated in the 2.4-GHz ISM band is proposed. With on-chip tunable components in low power LNA and LC-tank VCO circuit, the receiver measures a RF gain of 35dB at 2.4-GHz, sensitivity of -87 dBm at 0.1% BER, IIP3 of -10 dBm, and NF of 4.9 dB with current consumption of 31mA and a chip area of 2850mum times 2850mum

A Compact Planar Inverted-F Antenna for Octa-Band Operations of Smart Handsets

This paper applies planar inverted-F antenna (PIFA) to design a smart handset antenna in accordance with octa-band operations, as GSM 850 (824-894 MHz), GSM 900 (880-960 MHz), GSM 1800/1900, DCS 1800 (1710-1880 MHz), PCS 1900 (1850-1990 MHz), UMTS (1920-2170 MHz), IEEE 802.11b WLAN (2400-2484 MHz) and LTE (700 MHz/2300 MHz/2600 MHz) band operations for S11 -6 dB. The entire antenna is 75 × 22 × 5.8 mm3 with one-quarter wavelength design of hub. With the inter-coupling between dual branch circuit radiation and multiple branch circuit radiation, the wideband for GSM 1800/1900, DCS, PCS, UMTS, IEEE 802.11b WLAN and LTE 700/2300/2600 is generated. When integrating with mobiles, the designed ground plane area is also taken into consideration. In this case, the ground plane area can be increased in accordance to the system motherboard.

WiMAX bandpass filter using hybrid microstrip Defected-Ground-Structure

A novel and compact WiMAX microstrip bandpass filter is proposed. The filter employs a very wide bandwidth from 2 to 11 GHz under NLOS environment of the IEEE 802.16-2004 standard, and with a 3-dB fractional bandwidth of greater than 138%. The proposed hybrid WiMAX band-pass filter had return loss more than 17 dB in the passband, and also demonstrated a reject band from 12.4 GHz to more than 20 GHz at −20 dB.

A Tunable Fully Integrated Low-Power Low-IF Rx for 2.4 GHz ISM Wireless Applications

A fully integrated single conversion CMOS low-IF receiver for 2.4-GHz ISM band is proposed. With on-chip tunable components in low power LNA and LC-tank VCO circuit, the receiver measures a RF gain of 35 dB at 2.4-GHz, sensitivity of -87 dBm at 0.1% BER, IIP3 of -10 dBm, and NF of 4.9 dB with current consumption of 31 mA and a chip area of 8.12 mm2.

Device Tunnel Parameters for CoFe/Al-O/CoFe 1T1MTJ MRAM

Dielectric tunnel device parameters of CoFe/Al-O/CoFe MTJ of MRAM cell are measured and analyzed. General mathematical derivations for dielectric tunnel parameters in bright and dark region of MTJ cell are derived. The symmetry variation of dielectric tunnel charge in dark region of MTJ demonstrates a good balanced charge-conserved ferromagnetic plate capacitor. Parameters extraction and equivalent circuit model of dielectric tunnel capacitance C and resistance R from current-voltage curves for data 0 and 1 during 1T1MTJ read mode are proposed and demonstrated

In-Plane and Perpendicular Hall Magnetoresistance Ratio in MgO/FeCo/Pt/GdFeCo

AGM hysteresis and Hall magnetoresistance ratio (HMR) with in-plane (IP) fields and perpendicular (P) fields of multilayered films of amorphous RE-TM layers separated by a Pt inter-layer, are measured and compared. Hall voltage variation with P-field is twice larger than IP-field. It indicates more charges were deflected by the P-field than IP-field. Discrepancy of P-HMR and IP-HMR in forward (-B to +B) and reverse trace (+B to -B) are consistent with AGM hysteresis. Measured P-HMR and IP-HMR are almost 10 times over conventional MR