Agilent / Keysight 85650A Quasi peak adapter

The Agilent/Keysight 85650A Quasi-Peak Adapter is a specialized accessory that adds quasi-peak (QP) detection capabilities to compatible spectrum analyzers for electromagnetic interference (EMI) testing and regulatory compliance. This adapter enables accurate measurement of pulsed and broadband signals across multiple frequency bands, conforming to CISPR Publication 16 and FCC regulations. It has both manual and automatic QP detection modes with resolution bandwidths optimized for each frequency range, plus a bypass mode for standard analyzer operation.

Technical Specifications

• 200 Hz (0.01–0.15 MHz band)


• 9 kHz (0.15–30 MHz band)


• 120 kHz (30–1000 MHz band) Detector Time Constants


• Charge time constants: 45 ms (0.01–0.15 MHz), 1 ms (0.15–30 MHz), 1 ms (30–1000 MHz)


• Discharge time constants: 500 ms (0.01–0.15 MHz), 160 ms (0.15–30 MHz), 550 ms (30–1000 MHz) Quasi-Peak Response to CISPR Pulse across 1 kHz to 150 kHz PRF, with measurements ranging from 28.5 ± 3.5 dBµV (isolated pulse, 30–1000 MHz band) to 68.0 ± 2.5 dBµV (100 kHz PRF, 30–1000 MHz band). Response varies with pulse repetition frequency, frequency band, and signal characteristics.

Key Features

• Frequency coverage from 0.01 MHz to 1000 MHz


• CISPR-compliant bandpass filter response


• Compliance with MIL-STD 461A methods CE03 and RE02


• Compliance with VDE 0871 Level B and CISPR Publication 11


• Bypass mode for standard spectrum analyzer operation

Typical Applications

• Radiated and conducted EMI measurements


• Pulsed signal characterization


• Regulatory compliance testing (FCC, CISPR)


• Broadband interference assessment

Compatibility & Integration The 85650A interfaces with specified Agilent/Keysight spectrum analyzers to augment their detection capabilities without requiring replacement of the host instrument.