Description
1. Detailed Parameter Table
| Parameter Name | Parameter Value |
| Product Model | PXI-5691 |
| Manufacturer | National Instruments (NI) |
| Product Category | RF Downconverter Module |
| Frequency Range | 9 kHz to 6.6 GHz |
| Input Power Range | -130 dBm to +10 dBm |
| Noise Figure | 8 dB typical (2 GHz, 50 Ω) |
| Conversion Gain | 30 dB typical |
| IF Output Frequency | 200 MHz (fixed) |
| IF Output Level | 0 dBm ±2 dB |
| LO Source | Internal (0.5 to 6.6 GHz) or external (10 MHz reference) |
| Spurious Response | -60 dBc typical (at 1 GHz, -30 dBm input) |
| PXI Bus Interface | 32-bit/33 MHz PXI bus |
| Weight | 0.8 kg |
| Operating Temperature Range | 0 °C to 55 °C |
| Storage Temperature Range | -40 °C to 70 °C |
NI PXI-5691
2. Product Introduction
The NI PXI-5691 is a high-performance RF downconverter module designed for integration into PXI-based test and measurement systems. As a key component of NI’s RF test portfolio, it enables precise conversion of high-frequency RF signals to a fixed intermediate frequency (IF) for detailed analysis.
Ideal for applications requiring accurate signal conditioning across a broad frequency spectrum, the NI PXI-5691 covers 9 kHz to 6.6 GHz, making it suitable for diverse RF testing scenarios from low-frequency communications to high-frequency radar systems. By converting RF signals to a 200 MHz IF, it works seamlessly with NI digitizers and vector signal analyzers to provide comprehensive signal analysis capabilities. In RF test systems, the NI PXI-5691 acts as a critical front-end component, extending the measurement range of baseband instruments and enabling precise characterization of RF devices under test.
3. Core Advantages and Technical Highlights
Broad Frequency Coverage: With a frequency range spanning 9 kHz to 6.6 GHz, the NI PXI-5691 handles everything from VLF communications to UHF radar signals. This versatility eliminates the need for multiple specialized downconverters, reducing system complexity and cost in multi-band test setups.
Exceptional Signal Integrity: The module’s 8 dB typical noise figure and -60 dBc spurious response ensure clean signal conversion, preserving subtle signal characteristics critical for accurate modulation analysis and distortion measurements. This performance is particularly valuable in aerospace and defense applications where signal fidelity directly impacts test validity.
Flexible LO Options: Supporting both internal (0.5 to 6.6 GHz) and external 10 MHz reference sources, the NI PXI-5691 offers flexible synchronization capabilities. This allows integration into both standalone test setups and large-scale, multi-instrument systems requiring precise timing alignment.
Seamless PXI Integration: Designed for 32-bit/33 MHz PXI bus operation, the NI PXI-5691 integrates smoothly with other PXI modules, enabling compact, high-performance test systems. Its standardized form factor simplifies system scaling, allowing users to add multiple downconverters for parallel testing or extended frequency coverage.
4. Typical Application Scenarios
Wireless Communications Testing: In mobile device testing, the NI PXI-5691 converts cellular signals (GSM, LTE, 5G NR) from 700 MHz to 6 GHz to 200 MHz IF for detailed modulation analysis. This enables manufacturers to verify transmitter performance, including error vector magnitude (EVM) and spectral emissions, ensuring compliance with wireless standards.
Aerospace and Defense Radar Systems: For radar system testing, the NI PXI-5691 handles pulsed RF signals up to 6.6 GHz, converting them for analysis of pulse width, repetition rate, and modulation characteristics. Its wide dynamic range (-130 dBm to +10 dBm) allows capture of both weak return signals and strong transmit signals without damage.
Spectrum Monitoring: In electromagnetic spectrum monitoring applications, the NI PXI-5691 scans across its full frequency range to detect and analyze unknown signals. Its broad coverage and low noise figure make it suitable for identifying interference sources in communication networks and ensuring regulatory compliance.
RF Component Characterization: When testing amplifiers, mixers, and filters, the NI PXI-5691 provides controlled downconversion of test signals, enabling precise measurement of gain, insertion loss, and frequency response across the component’s operating range.
NI PXI-5691
5. Related Model Recommendations
PXI-5661: A 6.6 GHz vector signal analyzer that pairs perfectly with the NI PXI-5691 to create a complete RF analysis system, providing demodulation and signal analysis capabilities.
PXI-5412: An arbitrary waveform generator that, when used with the NI PXI-5691, forms a closed-loop test system for transmitter testing, generating stimulus signals and analyzing the resulting output.
PXI-6602: A timing and synchronization module that provides precise clock signals to the NI PXI-5691 in multi-module systems, ensuring phase-coherent measurements across multiple channels.
PXI-1042: A 18-slot PXI chassis that houses the NI PXI-5691 along with other test modules, providing a compact, integrated platform for RF test systems.
PXIe-5162: A high-speed digitizer that processes the 200 MHz IF output from the NI PXI-5691, converting analog signals to digital data for software-based analysis.
NI LabVIEW RF Toolkit: Software that extends LabVIEW’s capabilities for programming and controlling the NI PXI-5691, offering pre-built functions for common RF measurement tasks.
6. Installation, Commissioning and Maintenance Instructions
Installation Preparation: Before installing the NI PXI-5691, power off the PXI chassis and ensure proper grounding to prevent electrostatic discharge. Verify the chassis has an available 32-bit PXI slot and that the system power supply can accommodate the module’s requirements. Use anti-static handling procedures and align the module carefully with the slot guides to avoid connector damage during insertion.
Commissioning Steps: After installation, power on the chassis and launch NI Measurement & Automation Explorer (MAX) to confirm the NI PXI-5691 is recognized. Install the latest NI-RFSA driver suite and calibrate the module using NI’s calibration software to ensure measurement accuracy. Connect RF inputs using 50 Ω coaxial cables and verify signal conversion by inputting a known RF signal and checking the 200 MHz IF output with a spectrum analyzer.
Maintenance Suggestions: Periodically inspect RF connectors for damage or contamination, cleaning with approved RF connector cleaner as needed. Perform annual calibration to maintain measurement accuracy, especially in critical applications. Monitor operating temperatures to ensure they remain within the 0°C to 55°C range. If signal degradation is observed, check for loose connections or cable damage before suspecting module issues. Store the NI PXI-5691 in a dry environment within the specified storage temperature range when not in use.
7. Service and Guarantee Commitment
NI provides a comprehensive service and warranty package for the NI PXI-5691, including a standard 3-year warranty covering defects in materials and workmanship. During the warranty period, NI will repair or replace defective modules at no charge.
NI’s global technical support network offers expert assistance for installation, configuration, and troubleshooting, ensuring customers can maximize the performance of their NI PXI-5691. The company provides regular driver updates to enhance compatibility with new software releases and measurement capabilities. For calibration needs beyond the initial setup, NI offers ISO 17025-accredited calibration services to maintain measurement traceability. This commitment to quality and support ensures the NI PXI-5691 delivers reliable performance throughout its operational lifecycle in critical test environments.
