Portable Testers Provide Flexibility

Jan. 26, 2010
Compact battery-powered portable test instruments and newer USB-equipped test instruments are providing flexibility and cost savings over larger, traditional benchtop RF/microwave test instruments.

Portable RF/microwave test equipment may fall short in performance compared to their benchtop counterparts, but they provide other benefits, including adding test power in places that larger gear won't go. This survey samples available portable high-frequency test instruments and how they are being used in traditional and some novel applications.

Perhaps one of the most popular of portable RF/microwave test instruments is the spectrum analyzer. Many weigh just a few pounds, including battery, but incorporate features and performance approaching benchtop units.

The model 2658A portable spectrum analyzer from B&K Precision, for example, weighs only 1.8 kg (4 lbs.), but fits comfortably in one hand and operates for about 4 hours on a battery charge. The compact analyzer (Fig. 1) covers 50 kHz to 8 GHz and shows signal information on a color thin-film-transistor (TFT) liquid-crystal-display (LCD) screen with 640 x 480 pixel resolution. The analyzer has phase noise of -90 dBc/ Hz offset 100 kHz from the carrier and achieves a displayed average noise level (DANL) of -127 dBm. It includes a Universal Serial Bus (USB) port to transfer data to a personal computer, and has an auto tune feature that automatically tunes to the largest signal in its measurement range. Automatic measurements include adjacent-channel power (ACP), occupied bandwidth (OBW), and electric and magnetic field strength.

The N9340B handheld RF spectrum analyzer from Agilent Technologies features a 6.5-in. TFT color LCD as well as Ethernet LAN and USB interfaces. It operates from 100 kHz to 3 GHz with 10-ms sweep time and can run 4 hours on its rechargeable battery. It delivers a thirdorder intercept of +10 dBm with -144 dBm DANL when using an optional 3-GHz preamplifier. In addition, an optional 3-GHz tracking generator allows scalar-network-analyzer type measurements on coaxial cables and other transmission lines. The portable analyzer provides several one-button measurements for ease of use in the field, including channel power, ACPR, and OBW. With its recent acquisition of products and technology from Keithley Instruments, Agilent has added the latter's popular model 3500 RF power meter to its mix of portable RF/microwave test tools. The 3500 covers 10 MHz to 6 GHz with an integrated power sensor providing a power measurement range of -63 to +20 dBm. The absolute accuracy of the handheld power meter is as good as 0.21 dB. It includes an internal power reference and USB port for data transfer to a personal computer.

The model 9103 handheld spectrum analyzer from Willtek can perform scalar network analysis and spectrum analysis from 100 kHz to 7.5 GHz and resolution bandwidth (RBW) as fine as 1 kHz. It is suitable for antenna measurements and EMC pre-qualification tests and, with its optional tracking generator, it can perform cable measurements. Additional portable spectrum analyzers include the 10-kHz-to-6-GHz model FSH3-03 from Rohde & Schwarz, the 10-MHz-to-8-GHz model HF-6080 from Spectran, and the Spectrum Master series of instruments from Anritsu Co., with models covering 100 kHz to 3 GHz, 9 kHz to 7.1 GHz, 9 kHz to 13 GHz, and 9 kHz to 20 GHz.

In support of LTE measurements, Anritsu recently announced optional LTE capability for its MS272xB Spectrum Master portable spectrum analyzer, as well as for its MT8222A and MT8221B BTS Master handheld analyzers. The LTE RF measurement option allows users to accurately and quickly analyze the spectrum for interference and spectral compliance, as well as conduct OBW and ACLR tests. An LTE modulation quality measurement option allows error-vector-magnitude (EVM), frequency error, and control channel power tests to be performed on LTE infrastructure equipment.

The iHA Companion from Summitek Instruments is one of the more unique portable instruments, designed to provide passive intermodulation (PIM) testing at a cellular base transceiver station (BTS). Designed for custom frequencies, such as 870 and 894 MHz, the iHA Companion can identify major sources of PIM at a base station, offering a range of -83 to -153 dBc at 846 MHz when testing with two +33-dBm (2-W) tones. The measurement accuracy is 3 dB at -153 dBm. The handheld instrument runs for 2 hours on a rechargeable battery, measures 330 x 230 x 90 mm and weighs 5 kg. It is automatically calibrated when powered on.

Portable instrumentation used to imply test gear with a lightweight housing with a battery. But an increasing number of portable instruments are being equipped with USB ports, so that they can be easily transported, and then powered by a USB hub or a laptop computer with a USB port. These compact instruments leverage the computer's processing power for control and monitor for its display capabilities, essentially containing the RF circuitry needed to provide key measurement functions, such as power measurements or signal generation. The Lab Brick line of signal generators (Fig. 2) from Vaunix Technology Corp. includes models covering a total range of 50 to 6000 MHz in a package measuring just 124 x 80 x 40 mm. The LSG-602, for example, operates from 1500 to 6000 MHz with fixed-frequency, steppedfrequency, and single-sweep modes of operation. It provides a standard output range of +10 to -45 dBm and frequency resolution of 100 kHz. The phase noise is -75 dBc/Hz offset 10 kHz from the carrier and -95 dBc/ Hz offset 100 kHz from the carrier. Spurious content is typically -80 dBc and no greater than -70 dBc.

The model MBS-8000 is a test signal generator from EM Research, perhaps better known for its modular, embedded frequency synthesizers. The MBS-8000 (Fig. 3) spans 500 to 8000 MHz in 100-kHz steps with better than 100 ms switching speed. The miniature signal generator delivers +7 dBm output power with phase noise of -95 dBc/Hz or better offset 100 kHz from an 8-GHz carrier. It draws 230 mA current from a +5-VDC supply. It can operate from an internal or external 10-MHz reference source. It measures just 3.5 x 2.5 x 0.6 in. and is controlled by means of a 21-pin male Micro-Mini-D connector.

AnaPico AG offers several battery-powered portable signal generators, including the model APSIN3000 with frequency range of 9 kHz to 3.3 GHz, and the newer model APSIN6000, with coverage of 9 kHz to 6.4 GHz. Both units feature level uncertainty of better than 1 dB for an output range of -100 to +13 dBm. The switching time between frequencies is 1 ms while the phase noise is -130 dBc/ Hz offset 20 kHz from a 1-GHz carrier and -115 dBc/Hz offset 20 kHz from a 5-GHz carrier. The signal generators include a rechargeable battery and provide 0.001-Hz frequency resolution as well as amplitude modulation (AM), frequency modulation (FM), phase modulation, and pulse modulation.

For USB power measurements, Lady-Bug Technologies was a winner of a 2009 Top Product of the Year from Microwaves & RF for its PowerSensor+ power meters/sensors. The combination sensors and power meters measure only 1.60 x 2.25 in., yet can provide power measurements over a frequency range of 10 MHz to 26.5 GHz. They can measure the power levels of CW and pulsed signals over a dynamic range of -60 to +20 dBm, as well as time-gated pulsed and peak measurements, including measurements of pulse repetition frequency (PRF), rise and fall time, pulse width, duty cycle, and peakto- average power ratio.

Another source for USB power measurements is Mini-Circuits, with its model PWR-SEN-6G+ power sensor and associated power data analysis software. It covers a frequency range of 1 to 6000 MHz and a power measurement range of -30 to +20 dBm. The software provides support for as many as 16 sensors and is compatible with Visual Basic, C++, and LabView software from National Instruments.

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