| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩博士班 === 95 === The paper mainly presents the design of mixer for UWB radio frequency synthesizer application. Base on new frequency plan, we propose a RF frequencysynthesizer for ultra-wide band multiband OFDM (UWB MB-OFDM System) applications. We mainly focus on load in our mixer design. In order to degrade the powerconsumption effectively, LC-tank structure is implemented instead of resistor. Due to UWB MB-OFDM system covers relative large frequency ranges, the mixer must be designed to be able to operate at 3.1 to 10.6 GHz frequency range. For unity inductance, the peak impedance appears at 6.5 GHz which could degrade the output impedance dramatically at high/low frequency bands. From above reasons, we use switchable inductors to realize wideband load. We combine a MOSFET transistor with the differential inductor as switch, which its peak impedance is 5 GHz and 8 GHz receptively. It is effective to improve the output impedance at high/low frequency bands.
In this article, we apply a newly switchable differential inductor. Compare to traditional switch inductor structures, the proposed structure can release
over 50% chip area and cost of chip can also be saved. For our design methods, we simulate the characteristics of this switchable inductor by ADS Momentum and choose the adapt one for our circuit inductance. In order to describe the switchable inductors’ behaviors, a simple equivalent circuit model is presented and this model accurate over 10 GHz. The complete circuit is simulated which shows that quadrature mixer can operate in 3.1 to 10.6 GHz. This
quadrature mixer and differential integration uses TSMC 0.18um 1P6M standard RF CMOS process.
For the measurement of the above-mentioned quadrature mixer design, due to quadrature signal source is hard to obtain, therefore another important point of this design is integration of oscillators and mixer. By using the signal generated by oscillators apply to mixer, we consider the operation features of mixer at 10 GHz for our design. To verify this proposed mixer can operate at 10 GHz. The two oscillators operate at 3,168/4,224 and 6,072/7,128 MHz for UWB system application which mixer receives the signal to up-convert the frequency to 10.296 GHz.
The main creativity of this paper is as following: We use the switchable inductor to implement the switchable inductive loads. Thus, the mixer is able to operate at 3.1 to 10.6 GHz frequency range for new UWB radio frequency synthesizer application. Moreover, by using our proposed switchable inductor, the mixer not only can operate in UWB system, but also low area consumption and chip cost over 50%.
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