Advantest U3751 9kHz to 8GHz Spectrum Analyzer

The Advantest U3751 is a portable spectrum analyzer engineered for signal analysis across production, field maintenance, and service environments. Operating from 9 kHz to 8 GHz, it delivers processing speeds twice that of previous models, reducing test time and cost per measurement. The instrument achieves overall amplitude accuracy of ±0.8 dB (10 MHz to 3.1 GHz) and ±1.0 dB (3.1 GHz to 8 GHz) through a digital IF section and advanced circuit design.

A built-in standard preamplifier covering 10 MHz to 8 GHz provides typical noise performance of −135 dBm at 5 GHz, enabling detection of weak signals. The frequency counter resolves signals from 1 Hz to 1 kHz under specified conditions, while residual FM stability remains below 60 Hz p-p / 100 ms in zero-span mode. Resolution bandwidth spans 300 Hz to 3 MHz with ±12% accuracy; video bandwidth ranges 10 Hz to 3 MHz.

The input attenuator offers 0 to 50 dB in 10 dB steps. Amplitude range extends from noise floor to +30 dBm with reference level setting from −140 to +40 dBm. Five detector types

Normal, Posi, Nega, Sample, and RMS - support accurate power measurement of broadband modulation and CW signals.

Measurement capabilities include PASS/FAIL judgment via limit lines, harmonics analysis for radio device testing, and channel configuration using calculation and table methods. Frequency span accuracy maintains ±1% of span setting. The frequency reference exhibits aging of 2 × 10⁻⁶ / year and temperature stability of 2.5 × 10⁻⁶ (0 to 50°C).

USB 1.1, LAN, and GPIB interfaces enable remote operation and data transfer.

Technical Specifications

• Frequency Range: 9 kHz to 8 GHz (Band 0: 9 kHz to 3.1 GHz; Band 1: 3.0 GHz to 8 GHz)


• Preamplifier: Built-in standard, 10 MHz to 8 GHz; Noise −135 dBm @ 5 GHz (Pre-Amp ON)


• Amplitude Accuracy: ±0.8 dB (10 MHz to 3.1 GHz); ±1.0 dB (3.1 GHz to 8 GHz)


• Amplitude Range: Noise level to +30 dBm


• Reference Level Setting: −140 to +40 dBm


• Input Attenuator: 0 to 50 dB (10 dB steps)


• Resolution Bandwidth: 300 Hz to 3 MHz (±12% accuracy)


• Video Bandwidth: 10 Hz to 3 MHz


• Frequency Span: 0, 10 kHz to Full (±1% accuracy)


• Residual FM (zero span): < 60 Hz p-p / 100 ms


• Frequency Counter Resolution: 1 Hz to 1 kHz (RBW −50 dBm)


• Frequency Reference Aging: 2 × 10⁻⁶ / year


• Temperature Stability: 2.5 × 10⁻⁶ (0 to 50°C)


• Detectors: Normal, Posi, Nega, Sample, RMS

Key Features

• Processing speed 2× faster than previous generation models


• PASS/FAIL judgment via limit line configuration


• Harmonics measurement capability for radio device analysis


• Channel setting function supporting calculation and table methods


• Display range options: 100/50/20/10/5 dB linear


• Scale units: dBm, dBmV, dBµV, dBµVemf, dBpW, W, V


• High repeatability in power measurement via digital interface

Typical Applications

• Production line signal verification and testing


• Field maintenance and troubleshooting


• Harmonics and spectral content analysis


• Communication channel characterization


• Weak signal detection and measurement

Compatibility & Integration

• USB 1.1, LAN, and GPIB connectivity


• Remote operation and automated data transfer


• Portable form factor for on-site deployment