The Keysight (formerly HP/Agilent) 11975A is a leveled microwave amplifier designed specifically as a Local Oscillator (LO) driver for harmonic mixers, such as the Keysight 11970/74 series. It operates over a 2 to 8 GHz frequency range with adjustable output power.
Key Specifications (HP 11975A)
Frequency Range: 2 GHz to 8 GHz.
Output Power: Adjustable from +6 dBm to +16 dBm.
Signal Gain: 9 dB to 15 dB (varies by frequency).
Bias Output: Adjustable bias current for harmonic mixers (maximum $\pm$11 mA at +3 volts).
Automatic Level Control (ALC): Built-in, switchable on/off, with an "unleveled" indicator.
Absolute Power Accuracy: $\pm$2.0 dB (typical $\pm$1.5 dB).
Frequency Response: $\pm$1.0 dB (typical $\pm$0.5 dB).
SWR: 1.7:1 (ALC on), typical 2.5:1 (ALC off).
Connectors: SMA female (Standard), Option 001 provides Type N female.
Weight: Approximately 7.2 lbs (3.3 kg)
Features
LO Driver: Optimized to drive 11970/74 series harmonic mixers to maximum performance.
Protection: Includes a maximum-level-limiting circuit to prevent damage from accidental overload.
Monitoring: Output level is monitored by a broadband, rms-calibrated, peak-responding voltmeter.
Impedance: 50 ohms nominal
The HP 11975A is often used in spectrum analyzer applications to extend the frequency range up to 60 GHz and beyond when combined with harmonic mixers.