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1、 _ June 2006 Product Version 6.1 SpectreRF Workshop VCO Design Using SpectreRF MMSIM61 June 2006 VCO Design Using SpectreRF _ June 2006 Product Version 6.1 2 Contents Voltage Controlled Oscillator Design Measurements 3 Purpose 3 Audience. 3 Overview. 3 Introduction to VCOs 3 The Design Example: oscH
2、artley. 4 Example Measurements Using SpectreRF 5 Lab1: Output Frequency, Output Power, Phase Noise and Jitter . 6 Measurement (Pnoise with shooting or Flexible Balance engine) 6 Lab2: Frequency Pushing (Swept PSS) 31 Lab3: Tuning Sensitivity and Linearity (Swept PSS). 36 Lab4: Power Dissipation (PSS
3、) . 43 Lab5: Frequency Pulling (Swept PSS) 48 Conclusion 62 Reference 62 VCO Design Using SpectreRF _ June 2006 Product Version 6.1 3 VCO Design Using SpectreRF The procedures described in this workshop are deliberately broad and generic. Your specific design might require procedures that are slight
4、ly different from the ones described in this application note. Purpose This workshop presents how to use SpectreRF in the Analog Design Environment to measure parameters which are important in design verification of voltage controlled oscillators, or VCO. New features of MMSIM6.0USR2 are included. A
5、udience Users of SpectreRF in the Analog Design Environment. Overview This application note provides the user with a basic set of common measurements for VCO. Introduction to VCOs Oscillators generate a reference signal at a particular frequency. In voltage controlled oscillators, or VCOs, the frequ
6、ency of the output varies in proportion to some control signal. Oscillators are generally used in RF circuits to generate the local oscillator, or LO, signal for mixers. VCOs are used in both receivers and transmitters. The noise performance of a mixer is strongly affected by noise on the LO signal.
7、 The LO signal is always passed through a limiter, which is generally built into the mixer, to make the mixer less sensitive to small variations in the amplitude of the LO signal. Oscillators, except for reference oscillators, are embedded in phase-locked loops to control PLLs frequency and reduce t
8、heir phase noise. Reference oscillators are generally fixed- frequency crystal oscillators, and as such have well controlled frequency and noise. However, oscillators still produce enough variation in the phase of their output to affect the performance of the transceiver. Thus, it is important to mi
9、nimize the phase noise produced by the oscillator. VCO Design Using SpectreRF _ June 2006 Product Version 6.1 4 The Design Example: oscHartley The VCO measurements described in this workshop are calculated using SpectreRF in the Analog Design Environment. The design investigated is the Hartley oscil
10、lator shown below: The oscHartley VCO uses the basic Hartley topology and is tunable between 720 MHz and 1.1 GHz. The oscillation frequency (Fo) is determined by the resonant circuit made up of inductors (L0, L1) and the C1 capacitor. In this particular VCO, the values of L1 and L2 are fixed whereas
11、 the value of C1 is variable. In this example, the resonant circuits capacitor C1 serves as a varactor diode. As a result, the varactor diodes junction capacitance, var C, is a function of the applied voltage as shown in the following equation. VCO Design Using SpectreRF _ June 2006 Product Version
12、6.1 5 + = V C C j 1 0 var Where V = applied junction voltage (V) 0j C = junction capacitance (F) for V = 0 V f = barrier potential (V) = junction gradient coefficient The varactor diode for this VCO has the following values 0j C=8 pF f = 0.75 V = 0.4 Because var C is inversely proportional to V, and
13、 Fo is inversely proportional to var C, the oscillation frequency is proportional to V. In other words, as you increase V, var C decreases and Fo increases. Example Measurements Using SpectreRF To achieve optimal circuit performance, you should measure and evaluate several VCO characteristics or par
14、ameters under varying conditions. As an example, one fundamental measurement is the plot of VCO output frequency versus tuning voltage. An extension of this parameter is tuning sensitivity (expressed in Hz/V), which is the differential of the output frequency versus tuning voltage curve. The slope change as a function of frequency is a critical design parameter. In practice, both of these parameters should be evaluated under diffe
