| The mobile communication market has grown rapidly over the past two decades. This growth has increased the demand for the improvement of radio frequency (RF) circuit performance. Complete transceiver solutions that integrate low-noise amplifiers (LNA), mixers, voltage-controlled oscillators (VCO), and transmit modulators already exist. However, more stringent requirements on phase noise, gain, and spurious emission are necessary for cellular communications systems, such as GSM, DCS, and PCS, in order to increase available communication channels and lower power-consumption levels. Current status and paper reviews of oscillators and mixers are discussed in chapter 2. Since harmonic balance technique is widely used for analyzing high frequency circuits such as power amplifier, frequency multiplier, mixer, and oscillator, it is presented in detail in chapter 3. Oscillators are critical building blocks in all communication transceivers. Hence, characteristics of oscillator are also important in order to achieve good performance. The ability to achieve good phase noise performance is very important in most wireless design because introducing even small noise into an oscillator can cause dramatic changes in its frequency spectrum and timing properties. Thus, phase noise is a topic of theoretical and practical interest in oscillator circuits.{09}A comparative study of four different oscillator's phase noise models, Hajimiri-Lee, frequency sensitivity, small-signal mixing, and Kouznetsov-Meyer, is performed using Agilent Advanced Design System (ADS) and MathCAD. A Colpitts oscillator is used as an example in the study. Phase-locked loop (PLL) is used in many building blocks of modern transceiver including frequency synthesizer, frequency modulation, and FM-detectors. Good phase noise performance is important in a PLL because higher phase noise can degrade the system performance by reducing the signal to noise ratio, increasing adjacent channel power, and reducing adjacent channel rejection. Since noise performance is affected by loop dynamics, the calculation loop dynamic is first discussed. Three types of PLL are analyzed using MathCAD, ADS, and PSPICE. Magnitude and phase response plots are compared, and loop parameters are calculated. ADS's and PSPICE's results show approximately 2% difference in comparison to MathCAD's results. Since the type-II third-order PLL is the most common type of synthesizer at microwave frequencies, it is used as example in the study of phase noise of PLL. Since most of noise parameters are empirical, Druncker noise model is used in a comparative study of phase noise of PLL. MathCAD, ADS, and PSPICE programs are used in the calculation of noise. ADS software is proved to be the best model because of its simplicity and accuracy. |
