RFSpectrum Analyzer vs. Network Analyzer: Key Differences
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Spectrum analyzers excel at analyzing signal strength and frequency, while network analyzers provide comprehensive testing of RF networks using S-parameter measurements. Both use tuned receivers operating over similar frequency ranges. The primary difference lies in their measurement applications.
This page will outline the key differences between spectrum analyzers and network analyzers.
Figure 1: Spectrum analyzer using super-heterodyne architecture. (Refer to Spectrum Analyzer basics for more details.)
- A network analyzer measures reflection coefficients, transmission coefficients, insertion loss, return loss, S-parameters, and more, primarily testing components, devices, and sub-modules.
- A spectrum analyzer measures carrier power levels, harmonics, spurious signals, sidebands, phase noise, and more.
- Network analyzers are designed to measure phase-related characteristics, like group delay, which isn’t possible with a spectrum analyzer.
- Spectrum Analyzers helps discover unwanted signals and network analyzer helps measure known signals.
Figure 2: Network analyzer internal modules. (Refer to Network Analyzer basics and types for more details.)
- A spectrum analyzer is essentially a receiver displaying the signal fed to its RF input port from any RF transmitting device via cable or antenna. Modern real-time spectrum analyzers can even decode and display complex broadband RF signals from wireless devices like WLAN, WiMAX, GSM, Zigbee, and LTE. This requires additional baseband circuitry. Spectrum analyzers do not have an incorporated source.
- Network analyzers consist of a source and multiple receivers and measure broadband frequency signals using techniques like power and frequency sweeps.
- Spectrum analyzers generally have wider IF bandwidths compared to most network analyzers. However, network analyzers offer higher measurement accuracy due to vector error correction.
- With a spectrum analyzer, placing a marker on the display is easy, but interpreting the results can be challenging. Conversely, with a network analyzer, placing a marker might be harder, but interpreting the results is usually straightforward.
Spectrum Analyzer vs. Network Analyzer: A Feature Comparison
The following table provides a comparison between spectrum and network analyzers based on various features:
| Feature | Spectrum analyzer | Network analyzer |
|---|---|---|
| Primary Function | Measures the magnitude of signals over a frequency range | Measures both the amplitude and phase of signals (S-parameters) in a network |
| Purpose | Frequency domain analysis (spectrum of signals) | Analyzes the characteristics of RF networks (scattering parameters) |
| Type of Signals | Analyzes a single input signal (passive measurement) | Analyzes the relationship between input and output signals (active measurement) |
| Key Measurements | Power spectral density, frequency, noise, harmonics | S-parameters (S11, S21, etc.), reflection coefficient, return loss |
| Ports | Typically single input port for signal measurement | Usually has two or more ports for input and output network connections |
| Frequency Range | Broad frequency range, typically from kHz to GHz | Specific to the design, also in kHz to GHz range but used for network elements |
| Applications | Signal strength, modulation analysis, EMC testing | Device characterization (antennas, filters, amplifiers, etc.) |
| Complexity | Relatively simpler to operate | More complex due to phase and impedance measurement |
| Display | Frequency vs. amplitude (power or voltage) | Plots amplitude and phase (Smith chart, polar plot, etc.) |
| Example Instruments | Keysight N9320B, R&S FSV | Keysight PNA-X, R&S ZNB Network Analyzer |
Conclusion
Understanding the difference between spectrum and network analyzers is crucial for RF and microwave engineering. A spectrum analyzer focuses on the magnitude of signals across frequencies, ideal for signal strength and interference analysis. In contrast, a network analyzer measures both amplitude and phase, making it essential for evaluating RF components’ transmission and reflection properties.
