Laden with advanced functionalities, signal generators now offer benchmark performances

Today’s advanced signal generators come with excellent RF and baseband performance. With features like wideband vector modulation, these devices offer built-in baseband waveform generation with deep memory capabilities to ensure maximum versatility

By Richa Chakravarty

Monday, November 24, 2014: With the increasing complexity of many radio communication systems—from cellular phones and WiFi networks to the whole new era of 3G and LTE networks—the use of signal generators and analysers in the development and testing of products has also increased. The advanced and highend signal generators enable engineers to generate the test waveforms they require. These signal generators have evolved to address the need to generate far more complicated waveforms. To meet the needs of radio or wireless and cellular systems (that range from W-CDMA/UMTS to Wi-Fi IEEE 802.11, WiMAX-IEEE 802.16, LTE and many others), these generators utilise very complicated waveforms that use digital modulation.

Today, manufacturers offer the widest selection of baseband, RF and microwave signal generators (signal source) with frequency extensions up to 500GHz. These signal generators range from those that offer basic to advanced functionality, each delivering a good performance in its class to address users’ signal source requirements in the design and manufacturing stages.

Latest trends

Integrated test solutions: The latest trend in the market is the integrated solutions being offered by major players. The signal generators today not only perform signal quality analysis of all wireless technologies from 2G to 4G, supporting LTE-multimedia test and LTE-advanced with carrier aggregation and MIMO 4x capabilities, but are also capable of analysing RF signals on fibre feed lines. The JD720C series offered by JDSU covers physical layer testing for cell phone tower sites with coaxial or fibre feed lines, including reflection tests as well as fibre inspection and RF/optical power meters. According to Eduardo Inzunza, RF test lead, JDSU, “The JD780B series is the first integrated field solutions to analyse LTE-multimedia, LTE-advanced and RF signals over fibre links. Thus, they minimise tower climbs, reducing maintenance costs and time, while being future proof solutions. These are ideal solutions for installers of cell phone tower sites. They eliminate the need to carry multiple test instruments.”

Fully synthetic test solutions: Automated test equipment and maintenance costs are often much greater than the initial investment in hardware. Understanding this constraint for users, players today are focusing on reducing the total cost of test equipment. Aeroflex, a part of the UK-based Cobham group of companies, has recently introduced the 7700, an integrated microwave test solution. The 7700 offers a complete test environment for automated production and integrated testing of RF components and modules, covering a frequency range of 1MHz to 26.5GHz with a modulation bandwidth of 90MHz. It offers a complete synthetic solution, combining a vector signal generator, spectrum analyser, vector network analyser, power meter, frequency counter, noise figure meter and phase noise analyser. “Unlike traditional instruments, the 7700 is a synthetic solution that provides tight coupling of signal generation, measurements and device under test (DUT) control. This removes the additional software overhead and measurement processing necessary to make independent calls to several instruments and the DUT when executing a test,” informs Stephen Hire, general manager, Aeroflex Asia–India.

Support for a wide range of applications: Today’s designs are often complex, demanding a variety of stimulus signals during tests. With standard waveforms, arbitrary waveform capability and signal impairment options, most signal generators support a wide range of application needs with one instrument. Generating a range of signals requires investment in a high end signal generator. Manufacturers today ensure that one device can handle and meet the diverse requirements of the users so that signals are accurately produced.

Tektronix’ arbitrary waveform generator family provides leading edge performance with sample rates up to 50GS/s or lower sample rate solutions on up to four channels. RFXpress and SignalXpress software packages simplify the creation of these complex signals, reducing the time taken to generate real world signals. “The AFG2021 arbitrary/function generator can create simple and complex signals. But perhaps its most impressive feature is its entry level price,” says Naresh Narasimhan, country marketing manager, Tektronix India.

Supporting multi-signal applications: Today’s advanced signal generators offer great versatility. Most of them come with excellent RF and baseband performance. With features like wideband vector modulation, these devices offer built-in baseband waveform generation with deep memory capabilities to ensure maximum versatility. They support all key mobile communications and wireless LAN standards, and also offer the exceptional performance required for emerging and proprietary wireless communications technologies. Dual RF and dual waveform options are also available, which enable a single generator to produce more than one independent modulated output signal. Anritsu’s MG3710A makes it easy to implement complex test scenarios that normally require multiple synchronised signal generators. “For multi-signal applications, the MG3710A eliminates the cost of extra signal generators, simplifies equipment setup and calibration, streamlines system operations and speeds up measurement times,” shares Madhukar Tripathi, senior manager, marketing and channel sales, Anritsu India Pvt Ltd.

Simulating real world situations: The advanced signal generators are creating real situations in the labs too. The versatile configuration and the modular structure helps in supporting the complex application. With excellent signal quality for high accuracy in spectral and modulation measurement, all important fading scenarios are available as presets.

Rohde and Schwarz’s SMW200A vector signal generator is used particularly in aerospace, defence and wireless communication applications. It provides optional integrated fading section for channel emulation with up to 160 MHz bandwidth, providing as many as 16 ‘logical’ faders. It supports complex applications such as dual-carrier HSPA, LTE carrier aggregation and multi-user LTE too. “The SMW200A supports all important communication standards, i.e., LTE-A, HSPA, 802.11 ac, etc. It has a scalable platform along with an SCPI macro recorder/code generator. Also for wireless infrastructure supplies of LTE advanced, it supports 802.1 AC technologies, informs Nasser Jariwala, head, businness development, Rohde & Schwarz India Pvt Ltd.

Wide analysis and real time bandwidths: This is an important parameter as it defines the maximum bandwidth that the signal analyser can analyse in one go. Analysis bandwidth is an important parameter for applications requiring to demodulate signals for detailed vector signal analysis. Keysight Technologies’ N9040B UXA signal analyser boasts of one of the widest analysis capabilities and has real time bandwidth of up to 510 MHz, whereas most players in the industry offer just 160 or 165 MHz for real time. “Keysight has a lab—the High Frequency Technology Centre—and a fabrication facility which enables the development of proprietary and high end ASICs, DACs, ADCs and MMICs that are required for the next generation of test and measurement products. Our new products have these high end and innovative technologies embedded in them, which make them leaders in the industry,” informs Asish Jain, applications engineer, Keysight Technologies India Pvt Ltd.

‘Generate and play’ concept: Digital signal generators incorporate a wide bandwidth IQ modulation, which supports the latest digital communications. Most of the signal generators support applications for proprietary modulation systems or satellite data. Aeroflex’s S-Series of RF signal generators have set standards for low phase noise, fast frequencies and level settling times. These meet the requirements of demanding receiver tests as high quality local oscillators and substitute other general purpose applications. The S Series includes an embedded version of Aeroflex’s waveform creation software, IQCreator. Waveforms can therefore be created within the instrument and the press of a single button instantly plays the waveform from the settings in IQCreator. This allows waveforms to be created and modified ‘on the fly’. This signal generator can also be used to simulate real world situations.

How to choose a signal generator

While buying a signal generator, customers should consider the parameters that are required. There are a variety of channels available, and the buyer should decide how many are needed. Bandwidth needs should also be identified. Triggering capabilities, memory, display capabilities and sample rates also need to be considered when buying a signal generator. “While most of the buyers will check their requirements before opting for a generator, engineers on the go should ensure that the signal generator to be used in the field offers portable solutions and is capable of interfacing with cloud services for asset and data management from a centralised location,” advises Eduardo Inzunza.

Frequency range and analysis bandwidth: These are important parameters and solely depend on the application’s requirements. Analysis bandwidth defines the maximum bandwidth that the signal analyser/generator can analyse in one go. It is an important parameter for applications requiring to demodulate signals for detailed vector signal analysis.

Swept/FFT/real time modes: These are three different modes in which a signal analyser/generator can work. “Some analysers support one or two modes and there are signal analysers which support all three modes in one single unit. Each of these modes have their own advantages and it is important to know about the capabilities of these modes.

Spectral purity: These parameters describe the spectral purity of a signal analyser. Phase noise and harmonics become extremely important while characterising transmitters and oscillators.

Output power level: A signal generator is used for multiple applications, like, LO source, golden transmitter for receiver testing, amplifier testing, etc. Based on the test application and its requirements, a signal generator should be able to provide the desired output power level. For example, for testing the sensitivity of receivers, it is imperative to have a signal generator with a tunable power range and providing very low output power (~<-100 dBm).

Measurement applications: The new generation of signal analysers/generators are application based and they have measurement capabilities suited for individual applications, like phase noise measurement, noise figure measurement, EMI receiver measurement, cellular measurement (GSM, CDMA, HSPA, LTE etc.), wireless standards measurement (802.11 a/b/g/n/ac) etc.

Future upgradability: In order to optimise the cost of ownership, modern signal analysers/generators are upgradable in many ways. “Keysight’s signal analysers have an upgradable CPU to keep up with the ever increasing demands of fast processing and reduction in measurement speeds. Modern signal analysers are applications-based, and to ensure upgradability, most of the measurement applications are license upgradable,” informs Asish Jain.

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