The Three Core RF Measurement Instruments
| Instrument | Measures | Output | When To Use |
|---|---|---|---|
| Vector Network Analyzer (VNA) | S-parameters (magnitude + phase) | .s2p Touchstone file | Filter, amplifier, cable, antenna characterization |
| Spectrum Analyzer (SA) | Signal power vs frequency | Amplitude vs freq sweep | Harmonic measurement, spurious, occupied BW, EVM |
| Power Meter + Sensor | Average RF power (absolute) | dBm or mW | Calibrated absolute power, efficiency measurement |
VNA – S-Parameter Measurement
VNA measures: magnitude and phase of S11, S21, S12, S22 Frequency range: 100 kHz to 110+ GHz (high-end) Key advantages: - Phase information → group delay, impedance, matching design - Both reflection AND transmission in one sweep - Calibration removes systematic errors - Results saved as Touchstone .s2p for RF View analysis Typical VNA output files: .s1p, .s2p, .s4p → All readable by RF View for full analysis on Android
Spectrum Analyzer – Frequency Domain Amplitude
Spectrum analyzer measures: |V(f)|² (power spectral density)
No phase information → cannot compute S-parameters
Used for: spurious emissions, harmonic levels, occupied bandwidth,
signal quality (EVM via VSA software), phase noise
Key parameters: RBW (resolution BW), VBW (video BW), sweep time
Cannot replace VNA for S-parameter characterization
Combined Measurement Workflows
For complete RF amplifier characterization:
- VNA: small-signal S-parameters (gain, match, isolation, stability)
- Signal generator + power meter: P1dB measurement (power sweep)
- Two-tone generator + SA: IIP3 measurement
- VNA with noise figure option (or NFM): noise figure measurement
- All S-parameter data → load into RF View for matching design and comparison
RF View for VNA Data: After any VNA measurement, export .s2p file and load into RF View for complete S-parameter analysis — Smith chart, matching, simulation, Monte Carlo — on Android. Free on Google Play.