| Summary: | 博士 === 國立臺灣科技大學 === 電子工程系 === 95 === The key building blocks in the frequency synthesizer are the voltage controlled oscillator (VCO) and the high frequency divider circuit. Most importantly, low phase-noise is required to avoid corrupting the mixer-converted signal by close interfering tones for VCO circuit. The output of the VCO is divided down by the frequency divider which requires operating at high frequencies, wide operating range and lower power consumption.
First, this thesis describes two differential VCOs with tapped inductors. Both of two VCOs operate at a 4 GHz band with good phase noise lower than -120 dBc/Hz at 1MHz offset frequency. Also, a wide tuning range ring oscillator is presented. This circuit has a wide tuning range up to 70%, but its phase noise is worse than the LC-tank oscillator due to its inherent characteristic.
Then the injection locking technique is applied in high speed, low power frequency dividers, namely injection locked frequency dividers (ILFDs). Based on this technique, three ILFDs are presented for wide locking range application. The LC-tank oscillator ILFD can operate at 0.75 V supply voltage with a locking range from 3.14 GHz to 4.63 GHz while 0 dBm incident power is applied. The two ring oscillator based ILFDs which use switched capacitor load and variable inductor load respectively can provide a very wide locking range. The former has a locking range from 1.95 GHz to 5.5 GHz and the latter is from 1.15 GHz to 7.4GHz.
Finally, a novel quadrature VCO (QVCO) is proposed. By using transformer feedback technique, it can achieve lower phase noise performance about -124 dBc/Hz at 2.4GHz band with 135 MHz tuning range while 0.7 V supply voltage is applied.
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