Agilent / Keysight 8981A Vector Modulation Analyzer

The Keysight 8981A Vector Modulation Analyzer is a specialized instrument for analyzing complex modulated signals across communications, satellite, and radar applications. It delivers high-accuracy measurement of amplitude, phase, and frequency parameters through a calibrated I/Q demodulator architecture supporting IF inputs from 50 MHz to 200 MHz. The 8981A extends the capabilities of the HP 8980A by enabling direct connection to modulator IF outputs, making it ideal for signal characterization and design optimization in modern communication systems.

– Technical Specifications

• Frequency Range: DC to 350 MHz
• I/Q Demodulator: 50 MHz to 200 MHz IF input
• Baseband I/Q Filters: Internal, 35 MHz
• Demodulation Bandwidth: Up to 70 MHz for communications signals
• I and Q Channels Bandwidth (-3 dB): 350 MHz (DC coupled)
• Measurement Accuracy: DC vector accuracy ±1% of full scale; IF input measurement accuracy < 2% of full scale
• Quadrature Error: Corrected < 0.5°; uncorrected < ±1°
• I/Q Gain Imbalance (DC to 10 kHz): Corrected < ±0.1 dB; uncorrected < 0.25 dB
• Physical: 16 × 14 × 10 inches, 25 lbs

– Key Features

• Vector modulation analysis with constellation diagram display
• Quadrature error measurement and correction
• I/Q gain imbalance measurement and correction
• DC offset measurement and correction
• Lock angle error and signal closure measurement
• Phase transient measurement (delta-phase)
• Internal demodulator error correction routines
• Vector diagram (I/Q), I/Q vs. time, and 3D display options
• HP-IB interface for remote operation and automation

– Typical Applications

Cellular communications, satellite communications, radar systems, and modulator characterization requiring precise I/Q signal analysis and demodulator error quantification.