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64.8-GHz Divider Races On 0.13-m CMOS

WITH THE RAPID PROGRESS of complementary-metal-oxide-semiconductor (CMOS) technology, it has become more cost effective to realize 60-GHz receiver front-end circuits or even parts of a complete transceiver in 0.13-m CMOS. Recently, a team of researchers reported a low-power and wide-locking-range, 64.8-GHz injection-locked frequency divider (ILFD) using standard 0.13-m CMOS. A wide locking range of 10.2 GHz from 54.6 to 64.8 GHz (17 percent) was achieved by Chang-Zhi Chen, Tsung-Yen Chen, and Yo-Sheng Lin from China's National Chi Nan University together with Guo-Wei Huang from Taiwan's National Nano Device Laboratory.

The ILFD can be operated with -60 dBm input power. It requires 3.39 mW from a 1-V supply. The chip, which measures 0.90 x 0.73 mm without the test pads, uses a shunt inductor in the source node of the cross-coupled transistor pair to enhance the locking range. In addition, the inductors and capacitors of the LC tank were implemented by low-Q, micro-stripline inductors and high-Q varactors, respectively. A bias circuit also was included to stabilize the tail current source.

Because the divider's internal power is lowered by the large parasitic capacitance, the researchers introduced a shunt inductor at the load node of a tail transistor to maximize its load impedance. As a result, both the divider's locking range and input sensitivity were enhanced. Under +4 dBm injection power, the proposed ILFD achieved a locking range of 8.8 GHz. See "Excellent Sensitivity 64.8-GHz CMOS Injection-Locked Frequency Divider with 10.2-GHz Locking Range," Microwave And Optical Technology Letters, March 2010, p. 518.

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