HP 5968-6772E free download

File name 5968-6772E.pdf

Agilent 4352S VCO/PLL Signal Test System Optimizing VCO/PLL Evaluations and PLL Synthesizer Designs Application Note Introduction PLL Frequency Synthesizer Frequency Divider Loop Filter Today's mobile communication systems demand 1/M Phase VCO RF higher communication quality, higher data rates, Comparator higher frequency operation, and more channels per X'tal unit bandwidth. As much of this equipment is Programmable portable, low power consumption and small size are Frequency divider also required. All of these constraints combine to 1/N Prescaler make the whole design including component selection and evaluation quite challenging. One portion of this PLL IC design that is very critical with regard to all of the requirements mentioned above is the synthesized Set N data oscillator. Typical synthesized oscillators combine a Voltage Controlled Oscillator (VCO) with a Phase- Fig. 1: Basic Block Diagram of PLL Frequency Synthesizer Locked Loop IC (PLL), frequency reference (e.g. Crystal / TCXO) and a loop filter. The VCO is used to generate the RF output frequency. The PLL (which is of the "analog type"; i.e. different from a pure digital Design or Purchase VCO PLL) is used to stabilize and control the frequency. The loop filter design must integrate all of the compo- nents to establish, among other things, a tradeoff between noise and transient response (Figure 1). Evaluate VCO This Application Note will describe the evaluation of the PLL and VCO and relate those evaluations to infor- mation that will allow the circuit designer to optimize Design Loop Filter the whole oscillator design including the loop filter. Evaluate PLL Synthesizer Fig. 2: PLL Frequency Synthesizer Design Flow 1 VCO Characteristic Parameters The absolute level of oscillation power depends prima-