RF Test Equipment Series: Noise Sources/Noise Generators
RF designers and engineers spend a significant amount of design and effort dealing with noise in RF systems. So, it surprises some that there is a whole branch of RF test equipment that’s sole purpose is to generate noise. Noise sources are a key piece of test equipment, as well as being integral parts of some types of test equipment or precision communication and radar systems. Often noise sources are integrated into precision RF systems to aid with built-in testing (BIT), fault isolation testing (FIT), and for calibration.
Moreover, noise sources can be used to test receiver gain, bandwidth, phase tracking, noise figure, dynamic range, etc. Noise sources can also be used to calibrate the gain and phase of IQ modulation circuits as well as with multichannel receivers. Another use is the randomization of quantization errors in high-speed analog-to-digital converters (ADCs). These use cases are predicated on a Noise Sources ability to generate broadband noise that is precisely at the same power levels across the entire frequency range of operation (a.k.a. White Noise). Other noise types of interest include Gaussian Noise and Pink Noise, and the specific flavor of noise depends on the application.
Noise sources are much like other Noise sources come in a variety of forms, such as compact DC powered and calibrated sources to sophisticated bench mount Noise Generators with external interfacing and software control. Some noise sources are integrated into RF/Microwave assemblies, as part of multi-function rack-mount systems, or as part of a communication or radar system. Noise sources designed as test equipment are typically either compact inline devices with external power or bench-top equipment with the applicable interconnect for the frequency range of operation.
As is often the case with test and measurement equipment, Noise sources are often interconnected to the DUT and test system with high precision coaxial cables with minimal insertion loss and frequency over a broad range of frequencies. In some cases, adapters and other types of precision interconnect is also needed to pair between a noise sources and test system or DUT.
Key Noise Source and Noise Generator Performance Parameters
• Temperature Stability
• Voltage Stability
• Power Output
• Output Power Flatness
• Return Loss
• Frequency Range (bandwidth)
• Regulator technology
• Input Power
• Operating Temperature Range
• Temperature Coefficient
• Calibration Frequency Steps
• Voltage Coefficient
Useful Noise Sources Accessories and Equipment
• Pasternack Phase Stable (VNA) Coaxial Cables
• Pasternack Cable Generic Test Cable Assemblies
• Pasternack Skew Matched Pair Coaxial Cable
• Pasternack Precision Coaxial Adapters
• Pasternack In-series and Between-series Adapters
• Pasternack RF Coaxial Probe