- Buyers Guide
Compact, high performance programmable digital attenuators with frequency coverage to 6 GHz, offer a USB interface and intuitive GUI control.
Complementing a line of compact Lab Brick Universal Serial Bus (USB) powered and controlled signal generators, Vaunix Technology Corp. (www.vaunix.com) has announced a family of Lab Brick Digital Attenuators with 63 dB of programmable attenuation through 6 GHz. The first two standard models are the LDA-102, with frequency coverage of 0.1 to 1000.0 MHz, and the LDA-602, with a frequency range of 6 to 6000 MHz. Both units are powered and controlled by connection to a personal computer's USB port or a powered USB hub, and provide programmable attenuation from 0 to 63 dB with simple control via the included graphical user interface (GUI) software.
The LDA-102 and LDA-602 Lab Brick Digital Attenuators are ideal for engineering and production test laboratories as well as integration into high speed automatic-test-equipment (ATE) systems. They can also be used in development of low-cost fading simulators for Multiple Input Multiple Output (MIMO) and Single Input Multiple Output (SIMO) communication systems such as WiMAX, 3G and LTE. They are based on GaAs monolithic-microwave-integrated-circuit (MMIC) attenuator technology for excellent repeatability of attenuation values. Both units provide attenuation resolution of 0.5 dB by means of programmable steps from 0.5 dB through the maximum attenuation value of 63 dB (see table). The guaranteed attenuation accuracy is ±0.3 dB plus 5 percent of a given attenuation setting.
In addition to their programmable attenuation values, the LDA-102 and LDA-602 Lab Brick Digital Attenuators do exhibit some insertion loss as a function of frequency. For the LDA-102, for example, dissipative signal losses are a maximum of 6 dB from 0.1 to 100 MHz and a maximum of 7 dB from 100 to 1000 MHz. For the higher-frequency LDA-602, the insertion loss is a maximum of 7 dB from 6 to 1000 MHz, a maximum of 8 dB from 1000 to 2000 MHz, a maximum of 9 dB from 2000 to 4000 MHz, and a maximum of 10 dB from 4000 to 6000 MHz (see plot).
Due to the nature of GaAs technology, the Lab Brick Digital Attenuators provide a maximum input level of +20 dBm. For both models, the 0.1 dB compression point occurs at an input power level of +22 dBm. The input third-order-intercept point (IP3) is achieved at +46 dBm for a 0 dB attenuation setting on both units, and at +32 dBm for all other attenuation settings.
However, the LDA-102 and LDA-602 Lab Brick Digital Attenuators both enjoy the benefit of extremely fast attenuation switching speed as a result of the GaAs technology. Both units are rated for maximum switching speed of 80 ns, measured as the time for the unit to shift from a 50-percent control level to within 90 percent of a new attenuation setting, no matter how large the step size or change in attenuation.
The LDA-102 and LDA-602 Lab Brick Digital Attenuators are designed for 50-Ohm environments and exhibit maximum input and output VSWR of 2.0:1 for a 0 dB attenuation setting. The input and output VSWR drops to 1.70:1 for an attenuation setting of 0.5 dB and to a maximum value of 1.50:1 for all other attenuation settings, resulting in repeatable and accurate attenuation performance.
The Lab Brick Digital Attenuators draw power from a USB connection and require no additional DC supply voltage. They are controlled by means of an easy-to-install, simple-to-use GUI program (Fig. 2). Once the GUI is installed on a computer, connection of a Lab Brick Digital Attenuator loads the GUI, which displays the serial number for the active unit. Multiple programmable attenuators can be run on the same personal computer simply by opening a new instance of the GUI for each added attenuator.
The Lab Brick Digital Attenuator GUI is compatible with Microsoft Windows™ standard operating systems for personal computers, including Windows 2000, Windows XP, and Windows Vista. The GUI provides selectable attenuation steps of 0.5, 1, and 10 dB, and also allows an operator to program a desired step in increments of 0.5 dB from 0.5 to 63 dB. The GUI also allows attenuation ramps to be programmed over the full range from 0 to 63 dB, or from any start value to any stop value. The dwell and idle times of these attenuation ramps can be programmed from as short as 10 ms to as long as 20,000 ms.
The LDA-102 and LDA-602 Lab Brick Digital Attenuators are housed in rugged aluminum enclosures each measuring 3.86 x 2.52 x 1.35 in. (98 x 54 x 34 mm) and weighing just 0.5 lb. (0.23 kg). They are equipped with female SMA connectors and supplied with a 6-ft.-long USB 2.0 Type A to Mini B cable for connection to a personal computer, laptop computer or USB hub. The Lab Brick Digital Attenuators are supported by a Windows programming API dll complete with an example program and a LabVIEW-compatible software driver for ease of installation into ATE systems and custom test setups. In addition to the standard Lab Brick Digital Attenuator models, custom units can be tailored to specific performance requirements.
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