Power of Impedance Analyzer, Comparison to Network Analyzer

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Keysight’s impedance analyzers are the only instruments on the market that can provide unparalleled accuracy for component evaluation from mΩ to MΩ and from 20 Hz to 3 GHz frequency range. Uncover real characteristics of high-quality components. This application note describes why real-characteristics evaluation is essential and how to achieve real-characteristics measurements using impedance analyzer.

Table of contents

  • Introduction 
  • Necessity of Real-Characteristics Evaluation 
  • Characteristics of Components 
  • Characteristics of Circuits/Components on PCB 
  • Characteristics of Materials 
  • Characteristics On-Wafer 
  • Impedance Measurement Capabilities of Measuring Real- Characteristics 
  • Impedance Measurement Instruments 
  • Keysight’s Impedance Analyzers Specifications 
  • Comparison of Measurement Capabilities 
    • High impedance measurements 
    • Low impedance measurement 
    • Low D measurement 
    • High Q mearurement 
    • Measurement stability 
  • Conclusion

Necessity of Real-Characteristics Evaluation

The real characteristics in this document mean characteristics of electrical devices, materials, and components under actual conditions such as frequency, signal level, DC bias, and temperature. Characteristics should be known reliably and accurately. Although the components meet the manufacturer's specifications, they exhibit different characteristics when they are integrated into a circuit. The problems are sometimes due to the fact that the test conditions of the standard specifications offered by the manufacturer do not correspond to the actual operating conditions under which the part is used. In addition, characteristics that are not covered in the specifications often influence the performance of the circuit and may be unknowingly relied upon for proper operation. In most cases, due to the inflexibility of the measurement system, the conditions under which components are tested and selected are different from the conditions when the components are in operation.

To design a high-quality circuit, the characteristics of its components and printed circuit boards (PCBs) under actual operating conditions must be known. That is, the characteristics of components and PCBs depend on the conditions (frequency, signal level, temperature, etc.) under which they are used or measured. For manufacturers of electronic devices or components, it is necessary to evaluate the materials or components used in their products under actual operating conditions.

Characteristics of Components

Generally, the performance of an electronic circuit depends on the key components used. It is important to select proper components for meeting the circuit performance. For instance, in a voltage-controlled oscillator (VCO) circuit design when using an inductance-capacitance (LC) oscillating circuit system, the Q value of the inductor used influences the phase noise performance of the oscillation. If Q value is decreased (degraded), the noise level of the oscillation output will increase (phase noise will increase).

Since Q value of an inductor changes with frequency, it is necessary to measure the characteristic in actual oscillating frequency.

A mechanical resonator (crystal resonator, ceramic resonator, SAW resonator, etc.) is also used for a VCO circuit. Since the oscillating frequency and the frequency variable range are dependent on the resonator used, the actual property evaluation of the resonator is necessary.

Required measurement performance

  • Accurate Q measurement for inductor
  • Wide impedance range for resonators (up to several MΩ)

Characteristics of Circuits/Components on PCB

While the characterization of components under actual operating conditions is essential for circuit design, it is also critical in R&D and QA to characterize the circuit itself operating over a wide frequency range.

When designing an electronic circuit, basic circuit blocks, such as an amplifier or filter circuit, are designed first, and then the whole circuit is assembled. In order to shorten the development cycle time, the characteristics of each circuit block can be evaluated before the circuit is assembled. Evaluation of the input and output impedance of each circuit block, or component, is very important since the impedance between these basic circuit blocks should be well understood and matched. The characteristics of pattern inductance and stray capacitance between patterns of PCB under actual operating conditions must be known.

Required measurement performance

  • Easy to contact various components/circuit blocks mounted on a printed circuit and accurate measurements over a wide impedance range
  • Wide impedance range due to very small pattern inductance and stray capacitance (1 Ω to 1 MΩ)


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