Wei-Chang Li

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This paper presents a multi-band multi-standard receiver architecture for wireless applications, such as 802.11 a/b/g WLAN, and 802.16a WMAN. The targeted frequency bands include licensed bands - 2.3 GHz, 2.5/spl sim/2.7 GHz, and 3.5/spl sim/3.7 GHz, and un-licensed bands - ISM 2.4 GHz and U-NII 5 GHz. The main advantages of the proposed receiver are using(More)
The resonance and nonlinear dynamical properties of micromechanical structures have been harnessed to demonstrate an impacting micromechanical switch with substantially higher switching speed, better reliability (even under hot switching), and lower actuation voltage, all by substantial factors, over conventional RF MEMS switches. The particular resoswitch(More)
The use of hollow support stems to reduce energy loss to the substrate while supporting all-polysilicon UHF micromechanical disk resonators has enabled quality factors as high as 56,061 at 329 MHz and 93,231 at 178 MHz - values now in the same range as previous disk resonators employing multiple materials with more complex fabrication processes. With a(More)
The vector components of acceleration sensitivity &#x0393; for a closed-loop oscillator referenced to a wine-glass disk array-composite resonator employing tiny (&#x223C;92nm) electrode-to-resonator capacitive transducer gaps were measured along axes perpendicular and parallel to the substrate to be &#x0393;<inf>vertical</inf>&#x223C;13.6ppb/g and(More)
Substantial improvements in the far-from-carrier phase noise of oscillators referenced to stand-alone (as opposed to arrayed) capacitively transduced microme-chanical disk resonators have been attained via the use of atomic layer deposition (ALD) to tune the electrode-to-resonator capacitive gaps. Specifically, ALD of about 30nm of hafnia (HfO<inf>2</inf>)(More)
This paper proposes a multi-band low noise amplifier design for WMAN and WLAN applications. The target frequency bands include licensed bands of 2.3 GHz, 2.5 ~ 2.7 GHz and 3.5 ~3.7 GHz, and un-licensed bands of ISM 2.4 GHz and U-NII 5 GHz. The LNA adopts a band selection technique that uses a multi-tap inductor with complementary switch capacitor array. The(More)
A statistical comparison between the resonance frequency variations of stand-alone micromechanical disk resonators and mechanically-coupled array composites of them reveals that mechanically-coupled arraying of on-chip micromechanical resonators can very effectively enhance the manufacturing repeatability of resonance frequencies. In particular, twenty(More)
Quality factors as high as 362,768 have been measured for 61-MHz polysilicon wine-glass disk micromechanical resonators operated at cryogenic temperatures down to 5K. The measured results not only represent a &#x007E;2.5&#x00D7; increase in Q over the room temperature value, equivalent to a nearly 10-dB improvement in phase noise; but also provide some(More)
A micromechanical displacement amplifier comprising two asymmetric resonator array composites coupled by a quarter-wavelength beam has been demonstrated that permits specification of gain factor by mere (digital) selection of an appropriate ratio of the number of resonators in an input array to that in an output array. Like the method of [1], this(More)