| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 93 === The aim in this thesis is mainly based on the design of 2.45/5.2 GHz dual-band low-power direct-conversion harmonic mixer in the receiver front-end of 802.11a/b wireless local area network (WLAN) system using standard 0.18um CMOS process. Also, a narrow band 5.2GHz step-gain direct-conversion harmonic mixer is designed and analysis for 802.11a WLAN system. The two harmonic mixers were verified through individual chips.
In the first chip, a 5.2GHz step-gain direct-conversion harmonic mixer for 802.11a WLAN system is designed and analyzed. The harmonic mixer cancels the odd harmonic of LO signal by connecting the drains of the differential pair. It adopts a third-order low-pass filter with inductive peaking increasing the second harmonic level. This optimizes conversion gain and noise performance with a restricted bias current. Controlled by a switch, the simulation result shows that the mixer offers two gain levels of 18dB and 8.7dB. At high-gain mode, it achieves noise figure of 16dB at 1MHz frequency, and third-order input intercept point of -3.1dBm. At low-gain mode, it achieve noise figure of 25.7dB at 1MHz, and third-order input intercept point of -5.6dBm. Differential LO power level is chosen as -10dBm. With a supply voltage of 1.8V, the total power consumption is about 4.6mW.
In the second chip, a 2.45/5.2 GHz dual-band low-power direct-conversion harmonic mixer for 802.11a/b WLAN system is introduced. By tuning the peaking frequency of third-order low-pass filter, it can choose the operation frequency either in 2.45GHz or in 5.2GHz band. Simulation result shows that in 2.45GHz operation frequency, it achieves S11 of -11dB, conversion gain of 16.7dB, noise figure of 15.5dB, and third-order input intercept point of -6dBm. In 5.2GHz operation frequency, it achieves S11 of -12dB, conversion gain of 18.9dB, noise figure of 13.5dB, and third-order input intercept point of -1dBm. With1.8V power supply and -10dBm differential LO signal, the power consumption is about 2.3mW。
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