HP / Agilent 44478A Dual 1×4 RF Multiplexer Module (1.3GHz, 50 Ohm)

The HP/Agilent 44478A is a dual 1×4 RF multiplexer module delivering bi-directional signal routing from DC to 1.3 GHz with 50 Ohm characteristic impedance. Each of the two independent multiplexers switches one input to four possible outputs, making it ideal for automated test systems requiring flexible signal distribution across multiple measurement paths. The module employs a tree-structure relay design that achieves channel isolation greater than 55 dB at 1 GHz while maintaining insertion loss below 1.9 dB at 1.3 GHz. Switching speed is fast—rise time under 300 psec with signal delay under 3 nsec—enabling high-frequency pulse and RF signal applications without significant timing degradation.

– Technical Specifications

• Frequency Range: DC to 1.3 GHz
• Characteristic Impedance: 50 Ohm
• Maximum Switching Voltage: 42 V DC + AC peak
• Maximum Switching Current: 1 A DC or AC RMS
• Maximum Power per Channel: 24 W, 24 VA, or 44 dBm
• Maximum Power per Resistive Termination: 0.25 W or 0.25 VA
• Insertion Loss: Less than 1.9 dB at 1.3 GHz
• Channel Isolation: Greater than 55 dB at 1 GHz
• Closed Channel Resistance: Less than 1 Ohm
• Thermal Offset: Less than 6 µV (typical 2 µV)
• Rise Time: Less than 300 psec
• Signal Delay: Less than 3 nsec
• Insulation Resistance: Greater than 10¹⁰ Ohm at 25°C, 40% RH
• Center-to-Center Capacitance: Less than 0.006 pF
• Center-to-Shield Capacitance: Less than 60 pF

– Key Features

• Dual independent 1×4 multiplexer configuration
• Tree-structure relay topology for high isolation and low VSWR
• Female BNC connectors on module edge
• Male SMB connectors for 50 Ohm or 75 Ohm resistive termination networks
• Off-channel termination capability to maintain DUT circuit integrity
• Momentary center-to-shield shorting during relay transitions

– Typical Applications

• Automated RF test and measurement systems
• Multi-channel signal distribution and routing
• High-frequency pulse signal switching
• Broadband test signal multiplexing

– Compatibility & Integration

The 44478A integrates directly into Agilent 3499A/B/C and HP 3488A Switch/Control Systems for coordinated multi-module test configurations.