Function generators are moving towards a higher bandwidth and dynamic range

Players are focusing on developing devices with high capabilities, yet at a lower cost

By Richa Chakravarty

Tuesday, March 11, 2014: Function generators, variously known as signal generators, arbitrary waveform generators (AWGs) or digital pattern generators, are devices that produce simple repetitive waveforms. They are used to generate different types of electrical waveforms over a wide range of frequencies. Generally used in designing, testing, troubleshooting and repairing electronics, function generators can typically provide frequencies up to 20 MHz. Despite the fact that function generators cover both audio and RF frequencies, they are usually not suitable for applications that need low distortion or stable frequency signals.

Function generators like AWGs, radio frequency (RF) and microwave signal generators, vector signal generators, etc, serve different purposes and applications like defence, aerospace and telecommunications. Globally, the wireless telecom industry has greatly influenced the growth and expansion of the function generators industry in recent years. Manufacturers are currently focusing on developing devices with high capabilities and are making them available to customers at a cost.

What’s new in the market

The emergence of digital modulation technology and wireless technologies like wireless interoperability for microwave access (WiMAX), wideband code division multiple access (WCDMA), global system for mobile communication (GSM) and 3G wireless are driving the growth of AWGs, RF and microwave function generators. On the technological front, these generators are moving towards a higher bandwidth and dynamic range.

High speed DACs: The technical trends driving the industry in the arbitrary segment are the high speed digital-to-analogue converters (DACs) providing up to 16-bit resolution at sample rates in excess of 1 GSa/s. AWGs that are used for high-end design and test applications allow users to specify a source waveform in a variety of ways. These devices provide the foundation for an AWG with the bandwidth and dynamic range to address modern radio and communication applications. Agilent’s M8190A is a high performance, high bandwidth AWG. With Agilent’s proprietary DAC technology, the product has a 14-bit DAC and a sampling rate of 8 GSa/s or a 12-bit DAC at a sampling rate of 12 GSa/s. “The M8190A is a compact box available with an advanced telecommunication architecture extension for instrumentation (AXIe) platform, which makes it scalable. It offers the best spurious dynamic range currently available in the market with a resolution of 14 bits,” says Mahesh Subramanyam, applications engineer, electronic measurement group, Agilent Technologies India Pvt Ltd.

Modular designs to serve specific purposes: Keeping pace with the evolving technology, players are offering modular designs, providing options required for a specific application. Any configuration is possible with these modular designs. Rohde & Schwarz’s SMW200A function vector generator can be configured from a classic single path vector function generator to a multi-channel MIMO receiver tester. The generator can be equipped with a maximum of two internal baseband modules and four fading simulator modules. It is also possible to install a second 3 GHz or 6 GHz RF path. “The capabilities of R&S’ SMW200A surpass those of two conventional generators combined. When the instrument is fully equipped, the baseband section provides up to eight independent signal sources and up to 16 logical faders. This makes the SMW200A ideal for MIMO and other complex applications encountered in LTE Advanced, HSPA (dual carrier) and multi-standard radio,” shares Vinay Balusa, assistant manager, business development, Rohde & Schwarz India Pvt Ltd. The SMW200A offers exceptional compactness and uses the latest FPGA technology so that up to four of the powerful fading modules can be installed. These modules can simultaneously emulate as many as 16 fading channels. The maximum fading bandwidth is 160 Mhz.

One device for multiple purposes: For various multi-function receivers, such as mobile phones and car navigation systems, it is necessary to evaluate interference from other built-in systems. In this case, since the frequency bands are different, it is better to have a product line that can be selected freely. Anritsu’s MG3710A vector function generator offers dual RF and dual waveform options that enable a single MG3710A to give an output of up to four independently modulated signals. It offers a high-function, function generator with excellent RF and baseband performance. “The MG3710A features wideband vector modulation and offers built-in baseband waveform generation with deep memory to ensure maximum versatility. It supports key mobile communications and wireless LAN standards, and it also has the exceptional performance required for emerging and proprietary wireless communications technologies,” informs Madhukar Tripathi, regional manager, Anritsu Pte Ltd, India.

High performance and signal fidelity: Along with a modular structure, manufacturers are currently focusing on expanding the bandwidth and frequency range of function generators. Lecroy has recently expanded its popular WaveStation series of function/arbitrary waveform generators to include three new models with a bandwidth of up to 160 MHz and a 500 MS/s sample rate—over three times more bandwidth and four times more sample rate than the existing models. Informs Prabhanjana Rao, regional sales manager, India, SE Asia and ANZ, Lecroy India, “WaveStation 3000 models are available with bandwidths of 80 MHz, 120 MHz and 160 MHz, each with a 500 MS/s sampling rate, a 14-bit resolution and 16 kpts memory per channel. All WaveStation products come with two channels as standard. They also have an extensive waveform library, and various connectivity and synchronisation capabilities. In addition, the high sample rate and high resolution with low jitter and low harmonic distortion ensure the superior precision of the generated waveform.”

Compact sized devices: Function generators are not only getting compact in size, offering better aesthetics and improved portability but are loaded with state-of-the-art features. GW Instek’s USB compatible RF function generator with the frequency range from 35 MHz to 4400 MHz is a pocket-sized function generator. It can be powered with and operated through USB interface with PC, smartphone or a tablet. Available in five models to meet users’ requirements, the USG-series provides continuous wave (CW) signal outputs without any signal modulation function. “The USG series has several operational modes including fixed frequency, frequency sweep, frequency hopping and power sweep. The USG series RF function generator, with the frequency bandwidth limitation, provides lower harmonic output performance,” says Sumit Sharma, marketing manager, Good Will Instrument Co Ltd.

Taking a purchase decision

Before buying a function or signal generator, it is important to know the application it is required for — whether the generator is being used for a low, medium or high-end device. It is equally important to know the maximum frequency that needs to be generated, the bandwidth required, sampling rate of the generator, maximum and minimum power levels used for testing, etc.

“Along with the basic requirements, it is equally important for the user to know the software platforms that the instrument supports, along with the purity with which the signal needs to be generated. Also, the playback time that is required needs to be checked, which, in turn, will decide the memory requirements of the generator,” suggests Mahesh Subramanyam.

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