HP / Agilent 85021C Microwave Directional Bridge 10MHz to 18GHz

The HP/Agilent 85021C is a microwave directional bridge that measures reflection coefficients from 10 MHz to 18 GHz. Designed for use with scalar network analyzers such as the HP 8756A and 8755C, this instrument delivers the directivity and source match required for accurate reflection and transmission measurements in component characterization, antenna testing, and network analysis applications.

Technical Specifications

• Frequency Range: 10 MHz to 18 GHz


• Nominal Impedance: 50 ohms


• Test Port Connector: Type-N Female


• RF Input Connector: Type-N Female


• Directivity: 36 dB (10 MHz to 12.4 GHz); 34 dB (12.4 to 18 GHz)


• Maximum Input Power: +23 dBm


• Detector Flatness: ±3 dB, −1 dB typical (with leveled RF)


• Minimum Input Power: +7 dBm at 18 GHz (40 dB return loss measurement)


• Detector Type: Single zero-biased Schottky diode


• Dimensions: 15 mm (H) × 110 mm (W) × 96 mm (D)


• Weight: 0.5 kg net; 2.3 kg shipping

Key Features

• High directivity across the full operating band ensures accurate reflection coefficient determination


• Excellent source match minimizes measurement uncertainty in demanding environments


• Compact form factor accommodates integration into test systems with space constraints


• Type-N Female connectors on both input and test ports provide standard microwave connectivity


• Single Schottky diode detector architecture simplifies circuit design while maintaining performance

Typical Applications

• Reflection and return loss measurements


• Component characterization and qualification


• Antenna tuning and performance validation


• Scalar network analysis


• Transmission measurements (with external detector)

Compatibility & Integration The 85021C integrates with HP scalar network analyzers (8756A, 8755C), RF signal sources (HP 8350B Sweep Oscillator, 8340A Synthesized Sweeper), and external detectors (HP 11664A for DC to 18 GHz; 11664B for DC to 26.5 GHz).