Function Generators: Your Ultimate Buying Guide

A function generator is a tool that generates different electrical waveforms over a wide range of frequencies and is the most common type of signal generator. It's a fundamental piece of equipment for anyone involved in electronics or electrical engineering. 

With it, you can simulate various conditions for circuits, making it invaluable for design, testing, troubleshooting, and education. The right function generator can make your work more efficient and reliable, helping to keep projects on track.

Function generators are vital tools for electrical engineering, offering a variety of options tailored to different needs and applications. 

The main types available in the market include analog, digital, arbitrary waveform generators (AWGs), and software-based function generators. Each type has unique strengths and limitations, making them suitable for various applications.

Choosing the Right Function Generator

• Analog function generators: These are best suited for straightforward tasks where basic waveforms like sine, square, and triangular waves are sufficient. They're ideal for educational purposes and basic circuit troubleshooting.

• Digital function generators: These offer more precision and a wider variety of waveforms, making them suitable for more complex projects that require detailed signal simulation.

• Arbitrary waveform generators: (AWG) are the top choice for applications requiring the utmost flexibility and precision. They can generate any waveform, modeled after real-world signals, which is essential for research and development in cutting-edge technologies.

• Software-based function generators: These provide a good balance between flexibility and cost. They are suitable for environments where customizability and upgradability are key, such as in educational settings or startups.

When selecting a function generator, consider the specific requirements of your application, including the complexity of the tests, the precision needed, and your budget. Here's a comparison table to help you understand the differences between each type of function generator:

When choosing a function generator, it’s important to understand the key specifications and performance parameters. These details not only determine the device's capability but also ensure it meets the specific needs of your projects. 
Let's consider some of these critical parameters to understand their importance and impact on a function generator's performance.

• Wave frequency: Refers to the number of cycles a waveform completes in one second, measured in Hertz (Hz). It dictates the speed of the signal generated by the function generator.
• Range: Indicates the spectrum of frequencies a function generator can produce, from the lowest to the highest frequency. This range is essential for ensuring the function generator can cover the necessary frequencies for various applications.
• Resolution: This is the smallest increment of frequency that the generator can handle. Higher resolution means you can make finer adjustments to the frequency, which is critical for applications requiring precise signal tuning.
• Precision: This relates to how accurately the function generator can produce the set frequency. It's a measure of the device's ability to generate signals that closely match the specified settings without significant error.

Real-World Applications and Impacts

An engineer might use a function generator to simulate different audio signals when designing a new audio amplifier. Here, the range of the function generator needs to cover the full spectrum of human hearing (roughly 20 Hz to 20 kHz) to test the amplifier properly. The resolution is important when the engineer wants to precisely pinpoint the frequency at which the amplifier might introduce distortion or lose efficiency.

Frequency stability is a measure of how consistently a function generator maintains the set frequency over time. This stability is vital for applications requiring precise and consistent signal generation, such as in communications testing, where even minor frequency drifts can lead to significant errors in data interpretation.
Phase lock capability refers to a function generator's ability to synchronize its output phase with an external signal or another generator. This capability is crucial when working with multiple signals that must be coherently aligned, such as in phased array systems, complex modulation testing, or when simulating multi-channel scenarios.

Importance in Applications

In a radar system test, frequency stability ensures that the simulated signals remain consistent, allowing accurate measurement of the system's sensitivity and response over time.
With phase lock capability, engineers can synchronize multiple function generators to simulate complex environments or signals, such as coordinating the signals in a multi-antenna communication system to test beam-forming algorithms.
Choosing a function generator with robust frequency stability and phase lock capability is essential for ensuring the precision and reliability of your work, especially in advanced and high-precision applications.

Modulation is the process of varying a waveform to encode information. In function generators, modulation capability allows the user to simulate real-world signals more accurately by applying amplitude, frequency, phase modulation, or more complex modulation types. 
This feature is crucial for testing communication systems, electronic components, and control systems where the signal's behavior under various modulation schemes is of interest.
Sample rate refers to the frequency at which the function generator samples the digital representation of the waveform. A higher sample rate means that the waveform is represented with more data points, leading to greater fidelity and accuracy in the generated signal. 
This is especially important when creating complex or high-frequency waveforms, as it ensures the waveform's nuances are accurately reproduced.

Scenarios Requiring High Modulation Capability and Sample Rates

Communication systems testing: High modulation capabilities are essential for simulating the various modulation schemes used in wireless communication, such as QAM or PSK, to test receiver sensitivity and error rates.
High-fidelity audio equipment testing: High sample rates are crucial when testing audio components to ensure the generated signal accurately represents audio frequencies without aliasing or distortion.

Bandwidth, in the context of a function generator, refers to the range of frequencies it can accurately generate. Higher bandwidth allows the generator to produce a wider range of frequencies, from very low to very high, allowing it to test devices across a broad spectrum of applications.
Record length is the total duration of the waveform that can be stored and generated by the function generator. A longer record length allows for the generation of more complex or longer-lasting waveforms, which is crucial when simulating signals that change over time or when a precise simulation of real-world signals is required.

Impact on Waveform Production

• Broadband RF component testing: High bandwidth is necessary to test components in broadband RF systems, ensuring they operate correctly across their entire frequency range.
• Long-duration signal simulation: Long record lengths are essential for simulating signals that vary over time, such as the output of a varying sensor in environmental testing or long communication signals in network testing.

In electronic signal generation, noise and jitter are critical factors that can significantly affect signal integrity and the accuracy of test results. 

• Noise: Refers to any unwanted variation or interference in the signal. It can be caused by a variety of sources, including electrical interference from other devices, thermal fluctuations, or inherent imperfections in the function generator itself. Noise can distort the signal, making it difficult to accurately measure the response of the device under test or to simulate real-world signals accurately.
• Jitter: A specific type of temporal noise that affects the timing of the signal. It refers to the variability in the time position of the signal's edges, leading to uncertainty in the signal's phase and frequency. Jitter is particularly problematic in digital communications and any application where the precise timing of signal transitions is critical.

Effects on Signal Integrity

• Noise can reduce the clarity and accuracy of the signal, leading to errors in measurement and potentially masking the effects you're trying to observe or simulate.
• Jitter can cause bit errors in digital communications, disrupt synchronization between signals, and degrade the performance of systems that rely on precise timing.

Specifications to Minimize Issues

Users should look for function generators with:

1. Low phase noise: This indicates the generator produces a stable frequency with minimal short-term variations, crucial for applications requiring high-frequency stability.
2. Low jitter specifications: A function generator with low jitter is essential for digital signal applications, ensuring that timing errors are minimized.
3. High signal-to-noise ratio (SNR): A high SNR means that the signal is much stronger than the background noise, ensuring clearer, more accurate output.

Understanding the power requirements and connectivity options of a function generator is crucial for ensuring it fits seamlessly into your work environment, whether that's in a laboratory, in the field, or as a portable solution.

Power Requirements

• Laboratory applications: Typically rely on standard AC power sources. Ensure the function generator matches your lab's power supply in terms of voltage and frequency.
• Field applications: May require function generators with battery options or those that can operate on a wider range of power sources.
• Portable applications: Look for devices with low power consumption, battery operation capabilities, and lightweight design for ease of transportation.

Connectivity Options

• USB: Universal and easy to use, ideal for direct connection to a PC for data logging or control with custom software.
• Ethernet: Suitable for integration into networks, allowing remote control over LAN, which is beneficial for automated test systems or environments where the generator is part of a larger setup.
• GPIB (General Purpose Interface Bus): Though older, GPIB is still widely used in laboratory environments for connecting and controlling multiple devices in a test setup.

Relevance for Integration
USB and ethernet connections are essential for modern test environments where integration with computer-controlled setups is common. They offer flexibility in controlling the function generator from software, enabling automated testing and data collection.
GPIB remains relevant for setups that rely on this traditional standard, especially in labs with existing GPIB-controlled equipment, ensuring compatibility and ease of integration.

Channels in a function generator allow you to output multiple waveforms simultaneously, significantly expanding the device's capabilities. Each channel can operate independently, enabling the generation of complex signal scenarios, such as simulating multiple sensors or communication signals at once.

Available Options

• Single channel: Basic option, suitable for straightforward applications where only one waveform is needed at a time.
• Dual channel: Allows for two independent waveforms to be generated, useful for comparative testing or simulating two-part signals.
• Multiple channels (four or more): Ideal for advanced applications requiring the simulation of several signals or complex multi-channel communication systems.

Function generators vary widely in price, influenced by their capabilities, precision, brand, and additional features. Prices can range from a few hundred dollars for basic models to several thousand for high-end, feature-rich options.

Factors Affecting Cost

• Precision and range: Higher precision and wider frequency ranges typically increase the price.
• Number of channels: More channels add to the cost due to increased versatility.
• Connectivity and interface options: Advanced connectivity (Ethernet, USB, GPIB) and user-friendly interfaces (touchscreen) can raise the price.

Tips for Balancing Budget and Features

• Assess core needs: Focus on function generators that meet the essential requirements of your projects to avoid paying for unnecessary features.
• Consider future projects: Investing a bit more in a function generator with advanced capabilities can save money in the long run if it means avoiding the need to upgrade sooner.
• Look for deals on bundled software: Some function generators come with software packages that can add value.
• Explore used or refurbished equipment: Purchasing from reputable sources like the Keysight Used Equipment Store can significantly reduce costs while still providing quality and reliability. These options often come with limited warranties, offering a balance between cost savings and peace of mind.

"All of the equipment I sell is Premium Used. I don’t like to call it just “used”, because it’s so much more than used equipment." – Keysight Account Manager

Thinking back to that opening scenario about projects dragging on past deadlines because of unreliable equipment, it's clear why getting this decision right matters so much. Armed with the knowledge from this guide, you're ready to choose a function generator that won't let you down, ensuring your next project is on track for success, without the stress and strain of before. 

Choosing the right function generator directly influences the efficiency and success of your projects. We've gone through everything you need to think about, from the nuts and bolts of wave frequency and modulation, to ease-of-use features, power demands, and how it'll fit with the rest of your gear. We've also looked at why the number of channels matters, how to weigh up cost against features, and the importance of picking a brand you can trust.

Engineer your success with a Keysight function generator that's as ambitious and forward-thinking as you are. The right choice will elevate your projects, streamline your workflow, and allow you to tackle challenges with confidence, precision, and efficiency.