Archive | Feedback

Dual-Processor RF Power Meters Are Altogether Smart

The manufacturer says . . .

ChipCenter's Alex Mendelsohn says . . .

Introducing the RF Peak Power Meter for Production Testing of Wideband Modulation Formats The 4530 Series has the capability of having two independent channels that allow a variety of measurements to be made, including peak power, average power, peak-to-average power ratio, dynamic range, minimum power, CW power, and RF voltage. In addition, the power meter provides channel math functions that allow an engineer to display the sum/ratio or difference between channels, or between a single channel and a reference measurement. Boonton Electronics has designed the 4530 Series with statistical analysis features such as histograms and cumulative distribution functions (CDFs) so it can conduct fast analysis of complex signals, including CDMA and HDTV. The peak power meter can also perform time-domain power measurements on GSM, TDMA, and radar signals, as well as Universal Mobile Telephone (UMT) and other mixed-mode signals. The 4530 Series has an effective sampling rate up to 50 Msamples/s for repetitive signals. The single-shot sampling rate is 2.5 Msamples/s, yielding a single-shot bandwidth of 700 kHz. It can trigger on signals with a maximum pulse repetition rate of 500 kHz. A wide range of Boonton Electronics CW sensors (diode and thermocouple), peak power, and voltage probes can be used with the 4530 Series. Boonton Electronics' innovative sensor adapter allows the power meter to read the type of sensor connected automatically and switch to the appropriate operating mode. The sensor adapter is a self-contained EEPROM that stores calibration factors of the sensors, eliminating the need to manually enter calibration factors when changing sensors. When any of the peak-power sensors are used in conjunction with the 4530 Series' triggering capabilities, the power meter can conduct power analysis as a function of time, similar to how an oscilloscope displays voltage as a function of time. Triggering can be internal or external, or continuous sampling statistical power analysis can be used for nonuniform, digitally modulated carriers. The 4530 Series is equipped with both GPIB and RS-232C ports, making it well-suited for remote and ATE applications. Depending on the measurement mode, the power meter can sustain a rate of up to 500 two-channel readings/second simultaneously over the GPIB. Two video output ports are provided for viewing the RF envelope on an external oscilloscope, while a programmable DC recorder output port is also available to interface with chart recorders or external controllers. Features 4531—Single Channel 4532—Dual Channel Frequency Range: 10 kHz to 110 GHz Dynamic Range: Peak Power > 60 dB, CW Power -90 dB Synchronous/Asynchronous Triggering Statistical measurements (CDF/PDF) Modulation bandwidth to 20 MHz GPIB—SCPI/RS-232 commands

The 4530 Series of RF power meters makes it abundantly clear that Boonton understands both bench-level development and production-line engineering needs, as well as the diversity of the so-called wireless revolution. With the ability to be used in both lab testing as well as high-speed production applications, these dual-processor IEEE-488-compatible instruments, with their internal calibrator sources, can measure power from a low of 10 kHz all the way out to 40 GHz (for CW signals), or peak power from 50 MHz to 40 GHz. Also contributing to their factory-floor utility, these meters can store as many as four pre-configured front-panel setups. What's more, in IEEE-488 systems, they can measure at greater than 200 two-channel measurements/second (less bus master overhead) speeds, or make 500 single-channel measurements/second. The company's offering of the single-channel Model 4531 or the dual-channel Model 4532 is a wise move that's in step with today's tight-fisted engineering budgets, too. Again, the folks at Boonton understand the needs of the engineers they cater to. Sensible Sensors Boonton's 4530 Series meters are compatible with all of its existing RF wattage and voltage sensors, too. These sensors include coaxial dual-diode types and thermal sensors that work at 40 GHz. When using any of these, calibration and set-up data are automatically downloaded from the sensor when it's plugged into a 4350 Series box. That makes for a straightforward configuration process. The table reflects a sampling of peak power sensors that are currently available from Boonton. Not shown are the company's numerous CW sensors as well as RF voltage probes. click for full-size table A useful feature is the 4530 Series' ability to make CW power measurements without interruption. This attribute sidesteps the nonlinearity errors sometimes introduced by instruments that force you to make module, sensor, or range changes. Boonton's thermal and peak-power sensors never need range switching, and the company's CW diode sensors work with only two overlapping ranges. Multiple Processors As presented in my headline, these instruments are equipped with both a DSP and a dedicated I/O processor. This dual-processor architecture contributes to no speed trade-offs between RF data-acquisition tasks and the system's IEEE-488 handshaking. The floating-point DSP processes the power samples from the sensors, performs the measurements, time-stamps them, and then calculates for linearity correction and gain. The DSP also provides the appropriate filtering. These functions occur in less than a microsecond. Measurements are then passed to the 32-bit I/O processor for presentation on the unit's large LCD, as well as for transmission over either the RS-232 serial port or the IEEE-488 interface. The LCD can show text for the measurements for one or both channels. That's supplemented by a graphical chart-recorder-like display of average power. Indeed, the unit's LCD is quite oscilloscope-like. In its pulse mode (it can be used to analyze TDMA burst transmissions, for example), time-base and extensive triggering capabilities let you view and measure pulse waveforms or bursts. Common pulse-power and timing measurements can also be set up and performed automatically by the instrument, or can be defined to run manually. Two cursors can measure instantaneous power at time offsets relative to a trigger, or they can be used to define a time interval over which average and peak power measurements are made. This screen shot shows the cursors positioned over the active portion of a single GSM time slot to permit measurement of the average power and crest factor during an interval. The unit's LCD graphics and controls also let you pan and zoom, as well as present data in a variety of formats, showing cumulative distributions as well as histograms, for example. Trace averaging accommodates from one to 4,096 samples/data point. As mentioned in the press release, a 4530 can make two independent channel measurements of peak power, average power, minimum power, CW power, and peak-to-average ratio. It can also measure dynamic range and RF voltage. The system can operate in either continuous or triggered sampling modes to measure the true average power of modulated waveforms, while providing information about the instantaneous peak power as well as the crest factor. The instrument also has a Hold feature that stores minimum and maximum average power readings. This feature is great for viewing trends. In its peak tracking mode, the 4530 permits short-term crest-factor measurements to be made on real signals without the need to manually reset a held peak every time a signal level changes. Number Crunching A 4530 Series power meter can also calculate statistically. This feature is useful for analyzing non-periodic signals, such as CDMA spread-spectrum types. CDMA cell-phone signals are somewhat noise-like, with brief peaks that vary in magnitude. Measuring the average power of a spread-spectrum signal doesn't necessarily provide much insight as to how an RF deck's power amplifier stage is dealing with peaks. Nor do crest-factor displays. They only provide a measurement of the highest peak, and because that occurs once, it's of little value in predicting error rates. To get around this problem, Boonton's technique is to build a large population of power samples and then analyze the statistical probability of occurrence of each power level. Dubbed a Cumulative Distribution Function, or CDF, the 4530 plots the probability that power will be at or below a specified level. By examining the areas close to 100 percent probability, it's possible to see how often the highest peaks occur, so that you can see amplifier compression under actual operating conditions, for example. In that way, you may be able to predict an amplifier's effect on error rate. The screen shot here depicts statistical data that permit a close examination of the probability of very infrequent peaks that approach the absolute peak power. In terms of programming, 4530s use the industry-standard SCPI command syntax (Standard Commands for Programmable Instruments) over IEEE-488.1 (GPIB) or RS-232 interfaces. The boxes are also equipped with video output jacks that can feed detected logarithmic RF envelopes to outboard oscilloscopes for simultaneous observation. With the ability to measure the CW or peak power of a wide variety of RF signals spanning everything from VLF signals to cell-phone RF, or even TV carriers, Boonton's 4530 Series meters should fill the bill, whether you're working with CDMA, W-CDMA, CDMA2000, TDMA, GSM, GSM-EDGE, UMTS, or GPRS communications. Significantly, these instruments can be cost-effectively upgraded to accommodate those inevitable spread-spectrum modulation schemes of the future. That's a sure way to protect your investment.

Home | Column | Product of the Week | Editorial | Application Note

		Click here to get your listing up.