Agilent/Keysight 8405A

The Agilent/Keysight 8405A is a precision vector voltmeter that measures signal amplitude and phase relationships across RF and microwave frequencies. This dual-channel instrument simultaneously acquires voltage magnitude and phase data, enabling accurate characterization of complex signals and precise ratio and phase difference determinations between two channels. The 8405A supports insertion loss, group delay, gain/phase margin analysis, complex impedance measurement, amplitude modulation index detection, RF distortion analysis, and in-circuit probing - making it essential for amplifier, filter, mixer, and antenna characterization.

Technical Specifications

Frequency Coverage: 1 MHz to 1 GHz across 21 overlapping octave bands with automatic tuning. Amplitude Measurement:

• Voltmeter ranges: 100 µV to 1 V RMS full scale in 10 dB steps


• Gain/loss measurement capability exceeding 90 dB Phase Measurement:


• 360° zero-center meter display


• End-scale ranges: ±180°, ±60°, ±18°, ±6°


• Resolution: 0.1° at any phase angle


• Accuracy: ±1.5° (equal voltage on channels A and B)


• Meter offset: ±180° in 10° steps Voltage Ratio Accuracy:


• 1–200 MHz: 0.2 dB (−60 to 0 dB), 0.5 dB (−70 dB and +10 dB)


• 200–1000 MHz: 0.2 dB (−60 to −10 dB), 0.5 dB (−70 and 0 dB), 1.5 dB (+10 dB) Input Specifications:


• Maximum AC input: 2 V peak; DC: ±50 V


• Input impedance (nominal): 0.1 MΩ shunted by 2.5 pF


• AC coupled


• Channel isolation: >100 dB (1–300 MHz), >80 dB (300–1000 MHz)


• Bandwidth: 1 kHz

Key Features

• Dual-channel simultaneous voltage acquisition


• Optional impedance matching via HP 11576A 10:1 dividers or HP 10216A isolators


• In-circuit measurement capability


• Modulation index and distortion analysis

Typical Applications

• Amplifier gain and phase margin characterization


• Bandpass filter insertion loss and group delay


• Mixer complex impedance measurement


• Antenna impedance and pattern analysis


• RF and microwave circuit validation

Compatibility & Integration Standard accessories include two HP 11576A dividers, two HP 10216A isolators, two HP 10218A BNC adapters, and ground clips for in-circuit probing.