Power meters are as essential to testing microwave circuits and subsystems as digital multimeters (DMMs) and voltmeters are to troubleshooting printed circuit boards (PCBs) at any frequency. The new 4240 series of power meters (and their associated power sensors) from Boonton, a Wireless Telecom Group Company, bring a great deal of measurement power and flexibility to a high-frequency engineer's current choices in high-performance microwave power meters: the 4240 series includes single-channel and dualchannel models which, depending upon the connected sensor, can make power measurements from -70 to +44 dBm at continuous-wave (CW) frequencies from 10 kHz to 100 GHz.

The 4240 series of CW power meters (see figure) are the successors of the firm's 4230 series of power meters, designed to be fully backward compatible with all Boonton CW diode and thermocouple sensors developed for those older models. The two current instrument models in the 4240 series are the single-channel model 4241 power meter and the dual-channel model 4242 power meter. Although the total measurement range of each instrument is -70 to +44 dBm, the dynamic range of any test setup with either the 4241 or 4242 is dependent upon the sensor. For example, the company's diode sensors include model 51071A, with a power measurement range of -70 to +20 dBm (90-dB dynamic range) at frequencies from 10 MHz to 26.5 GHz and model 51072A, with a power measurement range of -70 to +20 dBm (90-dB dynamic range) at frequencies from 30 MHz to 40 GHz. The firm's thermocouple sensors include the model 51100, with a power measurement range of -30 to +20 dBm from 10 MHz to 18 GHz, and model 51200, with a power measurement range of 0 to +37 dBm from 10 MHz to 18 GHz.

The power meters automatically load frequency-response data stored in the memory of the firm's sensors when they are connected. In addition, older sensors can be upgraded with a data adaptor in order to take advantage of this automatic calibration feature in the meters. The power meters show results on an easy-to-read liquid-crystaldisplay (LCD) screen and also include standard General Purpose Interface Bus (GPIB) and RS-232 ports for connection to external computers and automatic-test-equipment (ATE) systems for display and processing of measurement results. Integration of either power meter into an ATE system is routine by means of simple software control via Standard Commands for Programmable Instruments (SCPI) language or a LabVIEW driver from National Instruments. (The 4240 meters are capable of emulating Agilent HP437 and HP438 and Boonton 4220A and 4230A meters.)

The 4240 series power meters perform power readings at better than 200 measurements per second, in support of high-speed ATE systems. They have a built-in 50-MHz step power calibrator with known power levels from -60 to +20 dBm, for checking and calibrating the accuracy of a instrument/sensor combination, and can display measurement results in logarithmic or linear units by means of five-digit resolution or bar graphs on the LCD screen. Wireless Telecom Group, Inc. (Boonton), 25 Eastmans Road, Parsippany, NJ 07054; (973) 386-9696, FAX: (973) 386-9191, Internet: www.boonton.com.