Spectrum Analyzer Comparison: Keysight, Tektronix, Rigol

This article compares spectrum analyzers from three major manufacturers: Keysight, Tektronix, and Rigol. While oscilloscopes are great for time-domain signal measurement, they don’t provide the frequency insight needed for many RF applications. That’s where spectrum analyzers come in.

Oscilloscopes represent signals in the time domain. To view signal characteristics in the frequency domain, a Fourier Transform is applied. This transform reveals the energy content of a waveform at different frequency points. Unlike an oscilloscope, which plots amplitude versus time, a spectrum analyzer plots power versus frequency.

Spectrum analyzers are indispensable for various tests and measurements, including:

• Frequency vs. Power analysis
• Modulation analysis
• Distortion measurements (harmonics, spurious signals, TOI - Third Order Intercept)
• Phase Noise measurement (dBc/Hz)
• EVM (Error Vector Magnitude) measurement
• IQ Imbalance analysis

Modern spectrum analyzers leverage DSP (Digital Signal Processing) and advanced signal processing algorithms. This enables the analysis of complex modulated signals commonly found in WLAN, WiMAX, LTE, and Zigbee devices.

Below, we’ll compare specific models from each manufacturer: Keysight (N9322C), Tektronix (RSA3408A), and Rigol (DSA875).

Keysight Spectrum Analyzer - N9322C

• Frequency Range: 9 kHz to 7 GHz
• Maximum Bandwidth: 1 MHz
• Phase Noise: -90 dBc/Hz @ 1 GHz and 10 kHz offset
• Amplitude Accuracy: +/- 0.6 dB
• TOI: +15 dBm at 1 GHz
• Third Order Dynamic Range (Max.): 83 dB at 1 GHz
• Attenuator Range and Step Size: 50 dB, 1 dB steps
• DANL (Displayed Average Noise Level): -152 dBm at 1 GHz
• Interfaces: USB and LAN
• Applications: Spectral Mask, Spectrogram, Field Strength, etc.

Tektronix Spectrum Analyzer - RSA3408A

• Frequency Range: DC to 8 GHz
• Real-Time Bandwidth: 36 MHz
• Phase Noise: -110 dBc/Hz @ 1 GHz center frequency and 10 kHz offset
• Amplitude Accuracy: +/- 0.5 dB (RF @ 100 MHz, power level: -20 dBm)
• P1dB (1 dB Compression Point): +2 dBm at 2 GHz
• Attenuator Range: 0 to 55 dB, step size: 5 dB
• Software Applications: Supports analyzer applications for WLAN (802.11a/b/g) and 3G standard-based technologies.
• Acquisition Memory: 16.4 MSamples or 65.6 MSamples options available
• Applications: RF and baseband signal analysis and measurements
• Interface: LAN port

Rigol Spectrum Analyzer - DSA875

• Frequency Range: 9 kHz to 7.5 GHz
• DANL: -161 dBm at 1.5 GHz
• Phase Noise: -98 dBc/Hz at 10 kHz
• Amplitude Uncertainty: Less than 0.8 dB
• Bandwidth: N/A (Consult datasheet)
• Minimum Measurable Signal: -135 dBm
• Interfaces: USB, LAN, GPIB
• Applications: RF and baseband measurements such as Adjacent Channel Power (ACP), Power Spectral Density (PSD), Occupied Bandwidth (OBW), Emission Bandwidth (EBW), Carrier-to-Noise (C/N) ratio, Harmonic Distortion, TOI point, etc.