USB Commands Fast Power Meter/Sensors

Jan. 26, 2009
These low-cost USB instruments combine a power meter and sensor in a compact housing for accurate, wide-dynamic-range power measurements through 26.5 GHz.

Power measurements once required tracking down the right sensor for connection to a benchtop power meter. LadyBug Technologies LLC has simplified matters not only by integrating the sensor with the meter, but by adding a Universal Serial Bus (USB) interface that allows a laptop or a personal computer (PC) to serve as the control center. The firm's growing line of power meter/sensor instruments currently provides pulsed and CW power measurements across a dynamic range of -60 to +20 dBm and a frequency range of 10 MHz to 26.5 GHz.

Founded by former engineers from Agilent Technologies (itself formerly part of Hewlett-Packard Co.), Richard Hawkins and Jon Sigler, Lady- Bug Technologies LLC is built upon a practical approach to high-frequency measurements. The firm's first series of instrumentsall combination power meter/sensor modelsleverage the intelligence readily available in a PC or laptop computer via the USB interface. The computer runs the control software and stores measurement results, while the power meter/sensor contains the measurement hardware required to capture power levels at RF and microwave frequencies. These PowerSensor+ integrated power meter/sensors perform temperature-corrected measurements for high accuracy over time, operating without need of "zeroing" or regular calibration before use (a one-year cal cycle is recommended by LadyBug).

The power meter/sensors cover a variety of frequency ranges, starting at 10 MHz and reaching 8, 12.5, 18, and 26.5 GHz. They provide measurement dynamic ranges as wide as 80 dB (-60 to +20 dBm). At just 1.6 x 2.25 in. (40 x 57 mm) not including the length of the connector, they are a fraction the size of competing power-measurement solutions. Although small in size, they do not skimp on performance, with fast measurement speed of 2000 settled measurements/s and recorder outputs that permit data capture. The instruments are available with a choice of connector: Type N, SMA, or TNC (except on the SMA-only 26.5-GHz unit).

Many of the PowerSensor+ integrated power meter/sensors measure the power levels of both pulsed and continuous-wave (CW) signals, allowing for pulse profiling and duty-cycle measurements along with capturing peak power levels. For example, models LB478A and LB479A operate over a frequency range of 10 MHz to 8 GHz with the capability for pulsed and CW power measurements. Model LB478A features a power measurement range of -35 to +20 dBm while model LB479A covers the widest measurement dynamic range currently offered by LadyBug Technologies: -60 to +20 dBm. Both models restrict total measurement errors to 1.95 percent or less and both offer outstanding impedance match with a device under test (DUT), with typical return loss of 27 dB (VSWR of 1.09:1).

The instruments can perform CW and average-power measurements as well as time-gated pulsed- and peakpower measurements, including measurements of pulse repetition frequency (PRF), rise and fall time, pulse width, duty cycle, and peak-to-average power ratio. With measurement speed of 2000 settled readings/s, both instruments can provide scalar-network-analyzer (SNA) type measurement of amplitude as a function of frequency. The power meter/sensors feature a video bandwidth of 10 MHz and effective sampling rate of 48 MSamples/s (the same rate used for all of the company's power meter/sensors). Models LB478A and LB479A are available with optional RF and TTL triggering, via an SMB male connector. In addition, the instruments provide recorder outputs of 0 to 1 V for data logging via a SMB connector.

Additional PowerSensor+ integrated power meter/sensors include the models LB579A for CW and pulsed power measurements from 10 MHz to 18 GHz, LB559A for CW power measurements from 10 MHz to 12.5 GHz, and LB589A for CW power measurements from 10 MHz to 26.5 GHz. Model LB579A (Fig. 1) covers a measurement dynamic range of -55 to +20 dBm and is useful for measuring the peak and average power levels of narrowband and wideband modulated signals, including CDMA, WCDMA, OFDM, QAM, GSM, TDMA, QPSK, FSK, AM, and FM signals. Available with Type N, SMA, or TNC connectors. Total measurement error, which is a combination of impedance mismatch, cal factor, noise, linearity, and temperature uncertainties, is 1.95 percent.

Model LB559A has a measurement dynamic range of -55 to +20 dBm and shares the accuracy of the other models, with 1.95 percent typical total error. It is also available with Type N, SMA, or TNC connectors, with better than 1.20:1 VSWR for SMA and Type N connectors and better than 1.35:1 VSWR for TNC connectors.

The highest-frequency power meter/sensor is model LB589A, operates from 10 MHz to 26.5 GHz with a CW power measurement range of -55 to +20 dBm. Available only with SMA connectors, this instrument exhibits low VSWR of 1.20:1 through 10 GHz and 1.29:1 through 26.5 GHz.

All of the PowerSensor+ power meter/sensors are easy to use, connecting to a laptop computer or PC's USB port (Fig. 2). They are supplied with software drivers to simplify integration into ATE systems based on LabView, C, and Visual Basic. LadyBug Technologies LLC, 3345 Industrial Dr., Suite 10, Santa Rosa, CA 95403; (866) 789-7111, (707) 546-1050, FAX: (707) 237-6724, Internet:

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