Agilent/Keysight 11666A

The Agilent/Keysight 11666A is a reflectometer bridge engineered for reflection coefficient measurements across microwave frequencies. Operating as a resistive Wheatstone Bridge extended to microwave bands, it integrates two Schottky diode detectors to sample incident and reflected signals, enabling ratio-based measurements when connected to a network analyzer. The bridge architecture - with three arms terminated at 50 ohms - produces a voltage across the measurement port directly proportional to the device-under-test reflection coefficient.

This design provides effective external leveling, isolating the measurement port from source and bridge input mismatches.

Technical Specifications

• Frequency Range: 40 MHz to 18 GHz


• Impedance: 50 ohm


• Input SWR: 1.92


• Maximum Input Power: +15 dBm


• Output SWR: 1.25 (40 MHz to 8 GHz); 1.27 (8 to 12 GHz); 1.32 (12 to 18 GHz)


• Insertion Loss: 6 dB nominal (input to either output)


• Equivalent Directivity: 30 dB (40–100 MHz), 38 dB (0.1–1 GHz), 36 dB (1–2 GHz), 33 dB (2–4 GHz), 29 dB (4–8 GHz), 27 dB (8–12 GHz), 26 dB (12–18 GHz)


• Frequency Tracking (incident and test port, including 1.1 dB from 11664A Detector): <3.2 dB


• Connectors: Type N-Female (input/output); APC-7 optional


• Cable Length: 1219 mm


• Dimensions: 69.9 mm H × 69.9 mm W × 46.4 mm D


• Weight: 0.7 kg (net); 2.26 kg (shipping)

Key Features

• Dual Schottky diode detector configuration captures incident and reflected signals


• Frequency-dependent directivity optimized across full 40 MHz to 18 GHz range


• Compact form factor with attached 48-inch cable


• Output SWR controlled to 1.32 maximum across entire operating band

Typical Applications

• Device reflection measurements and return loss characterization


• Simultaneous insertion and return loss ratio measurements (with external 11664A Detector)


• Impedance and reflection coefficient determination on network analyzers

Compatibility & Integration The 11666A integrates with the Agilent/Keysight 8755C Network Analyzer. External connection of the 11664A Detector enables simultaneous dual-measurement capability.