Low-Cost AWGs Use PC For Display And Control

May 12, 2010
If you don't mind plugging a USB cable into a PC, then LeCroy's ArbStudio arbitrary waveform generators could save you a chunk of change without sacrificing performance compared with traditional bench-top AWGs.

ArbStudio AWG

LogicStudio logic analyzer

If you’re as comfortable with your PC as you are with bench instruments, then LeCroy has an arbitrary waveform generator (AWG) family that’s right up your alley. The ArbStudio line of instruments is the company’s entry into the low-cost arena, and LeCroy has chosen a non-traditional path to hold down cost. Instead of producing the ArbStudio instruments (Fig. 1) as full-out bench instruments with a display and front panel, LeCroy has implemented these systems with USB connection to a PC, which serves as the user interface.

Obviously this arrangement translates into some tradeoffs for the user, but for the most part they are positive. The ArbStudio series includes pairs of two- and four-channel models that range in price from $2490 to $4990. The banner specifications include a maximum sample rate of 1 Gsample/s, analog bandwidth of 125 MHz, 16-bit resolution, and 2 Mpoints of memory/channel. The D versions include a digital pattern generator with 18 or 36 channels.

Using the PC for display and interface functions enabled LeCroy to build more performance into these instruments at a price point that’s similar to standalone instruments. Their high sampling rate and resolution stand out, combining to provide very precise on-screen waveforms. The long memory of 2 Mpoints/channel enables the creation of large waveforms and long waveform sequences. The high bandwidth of 125 MHz covers a broad range of applications as well.

The instruments provide both dedicated function generator and pulse-width-modulation (PWM) modes. In the full arbitrary-waveform generation mode, the ArbStudio replicates a benchtop function generator. Its software also provides a PWM control panel, giving users an easy way to create complex PWM waveforms without having to resort to building them in the generator. The PWM mode is very handy for designers working on fan or motor control systems.

While most waveform generators use either true arbitrary generation or direct-digital-synthesis (DDS) technology, the ArbStudio instruments provide both modes. Each has advantages and disadvantages depending on needs. For complex modulation, DDS mode is the better choice. For more complex waveforms without modulation, the true arbitrary mode fills the bill. Either can be used at any time in different channels.

The ArbStudio 1102D (two-channel) and 1104D (four-channel) models add 18 or 36 channels of digital pattern generation, respectively. A flexible user interface lets you draw waveforms or type in bus values that will create the corresponding waveforms.

In a related announcement, LeCroy has introduced its LogicStudio, a USB logic analyzer for the embedded-systems market. The strategy here is similar—by eschewing a traditional instrument approach with knobs, buttons, and a display, LeCroy can offer more performance at a lower price point. The $990 LogicStudio (Fig. 2) provides 16 channels, a sampling rate of 1 Gsample/s, and 100-MHz input. It also offers I2C, SPI, and UART trigger and decode. On the PC screen, users will benefit from a fast, dynamic display that offers a persistence mode to see phenomena such as jitter.

If you happen to have a LeCroy oscilloscope with the company’s WaveJet connectivity feature, you can use the LogicStudio software to import analog waveforms from the scope, enabling you to display analog, digital, and serial waveforms on one display. Effectively, this gives you the equivalent of a mixed-signal oscilloscope on your PC screen. You can control scope triggering and import waveforms on the fly. Analog waveforms are scaled and displayed with V/div readout.

LeCroy’s Web site features a full-featured demo version of the LogicStudio software for downloading and evaluation. Simulated waveforms are built in so you can give the software a workout and make measurements on those sample waveforms.

LogicStudio lets users choose from a variety of logic levels including TTL, CMOS, and custom types. The instrument has two operating modes: 1 Gsample/s, eight channels, and 40 kpoints/channel of memory, or a 500-Msample/s rate, 16-channel operation, and 20 kpoints/channel of memory.

Trigger types comprise edge, width, pattern, pattern width, I2C, SPI, and UART. There’s basic edge and level triggering for the capture of basic events, but there is also advanced logic triggering for a more complex triggering environment. You can combine edge, level, pattern, and serial data triggers with a variety of logic operators to build up very complex patterns if needed.

Users can configure and display up to four cursor pairs and use them to make simultaneous time and frequency measurements. The cursors can be snapped to wave edges for precise measurements. Up to 100 acquisitions can be saved in the instrument’s history buffer, and you can scroll through them after taking measurements to help identify problems.

Interesting and useful, the instrument’s waveform magnification provides a closer look at signal details. There’s no need to change the acquisition time window to accomplish zooming. A simple scroll of the mouse wheel is all it takes.

LeCroy Corp.


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