Welcome to this training module introducing the RF Power meter V3500A. Here we study how to operate the device for different measurements.
The palm-sized power meter from Agilent Technologies delivers high quality RF power measurements for installation and maintenance or for R&D lab environments. The V3500A Handheld RF Power Meter is a compact, handheld instrument that makes accurate RF power measurements in both field and manufacturing applications. With an absolute accuracy as good as ±0.21dB, a wide frequency range of 10MHz to 6GHz, and a measurement range of -63dBm to +20dBm, the V3500A is suitable for a wide variety of RF measurement applications.
The device accepts signals from 10 MHz to 6GHz with power ranging from -63dBm to +20 dBm.
It has 4-digits with backlight feature, USB 2.0 interface with mini-B USB connector and Type-N male RF connector. The interface is USB 2.0 compliant but with an interface speed of 12 Mbps.
Power is defined as the amount of energy flow per unit of time, and the basic unit of power is the watt (W). One watt equals one joule per second. The watt is a basic unit in that other electrical units are derived from. For example, a volt is defined as one watt per ampere. Absolute power is expressed in terms of dB relative to some power level. For example, power relative to 1 mW is stated in dBm. For a purely resistive load the power factor is one and instantaneous power is simply the product of voltage and current. For an AC signal we see that power is time dependent. Fundamentally, power is defined as the energy transfer per unit time averaged over many periods of the lowest frequency involved.
Here we see how the RF amplitude is measured.
At DC, the voltage drop across a device and current through the device are measured directly, At frequencies below approximately 100 kHz, power measurements are not distinctly different and are still usually found from voltage or current. Though the measurement of voltage and current is still practical for frequencies in the tens and hundreds of MHz range, the direct measurement of power is more accurate and easier. As a result, voltage and current are usually the calculated parameters at these frequencies As the frequency approaches 1 GHz, direct power measurements become prevalent in most applications because voltage and current measurements become impractical. For these reasons, at radio and microwave frequencies, power is more easily measured, easier to understand, and more useful than voltage or current as a fundamental quantity
Average, pulse, and peak envelope power measurements are all different types of measurements that will provide different information about a signal. Average power provides average power delivered over several cycles and typically is implied when talking about &quot;power&quot;. Pulse power is used in situations where complete characterization of the modulated envelope itself is needed. Finally, peak envelope power should be used to obtain more accurate measurements when the pulse becomes non-rectangular and peak power equations would no longer be accurate. Each type of measurement will be discussed.
This slide gives details about user interface function details. The VM3500A device has a built in backlight display, The power connector provides a connection for the optional external power supply, The V3500A can also be powered by two AA batteries, The power meter has a USB 2.0 interface with a USB type Mini-B port, The V3500A can be remotely programmed over this USB interface.
The Agilent V3500A RF Handheld power meter provides accurate average power measurement as well as average pulse power measurement. Here is a demonstration of measuring power given step wise. This will require an E44380 ESG vector signal generator and a V3500A handheld to perform this measurement.
Here are step wise procedures to set up the V3500A.
Pulse power is determined by measuring the average power of the pulse and then dividing the measurement results by the pulse-cycle value to obtain the pulse power reading. The measurement result is a mathematical representation of the pulse power rather than the actual measurement with the assumption of constant peak power. The duty-cycle technique provides the lowest-cost solution, with average power meters and sensors being less expensive than peak and average power meters and sensors.
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V3500A Handheld RF Power Meter
V3500A Handheld RF Power Meter <ul><li>Source: Agilent Technologies </li></ul>
Introduction <ul><li>Purpose </li></ul><ul><ul><li>To Introduce V3500A Handheld RF Power Meter </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Key Features and Specification of RF Meter </li></ul></ul><ul><ul><li>user Interface diagram of RF Meter </li></ul></ul><ul><ul><li>Demonstration of Measuring Average power </li></ul></ul><ul><ul><li>ordering Information and Accessories </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>14 pages </li></ul></ul>
Key Features of V3500A <ul><li>Broad 10MHz to 6GHz frequency range enables use in a wide variety of applications </li></ul><ul><li>Wide dynamic range of -63dBm to +20dBm </li></ul><ul><li>Integrated power sensor eliminates the need to carry a separate power sensor </li></ul><ul><li>Internal power reference enable self calibration </li></ul><ul><li>Absolute accuracy as good as ±0.21dB </li></ul><ul><li>Powered from batteries, AC-DC converter module or a computer via USB interface </li></ul><ul><li>Compensate for cable losses with the Relative Offset function that can add an offset to the display ranging between –99.99 dB and +99.99 dB </li></ul>
Units and Definitions <ul><li>Unit of power is the watt (W): 1W = 1 joule/sec </li></ul><ul><li>The watt is a basic unit: 1 volt is defined as 1 W/ampere </li></ul><ul><li>Relative power measurements are expressed in dB: P(dB) = 10 log(P/Pref) </li></ul><ul><li>Absolute power measurements are expressed in dBm: P(dBm) = 10 log(P/1 mW) </li></ul>Amplitude t P I V DC component of power AC component of power
Measuring RF Amplitude <ul><li>For lower frequencies, pk-pk volts can be measured directly across a load R. </li></ul><ul><li>Depends how fast your ’scope is. </li></ul><ul><li>The amplitude is half the pk-pk value </li></ul><ul><li>The RMS voltage is amplitude x 0.707 </li></ul><ul><li>Calculate power: P = ((V*V) / R) </li></ul><ul><li>Transmitters must be operated in continuous CW mode or with an SSB tone </li></ul>
Power Measurements at Different Frequencies <ul><li>DC </li></ul><ul><li>Low Frequency </li></ul><ul><li>High Frequency </li></ul>V Inc V R Z S Z O R L V R L V R L - + ± Z S Z S I I
Types of Power Measurements CW RF signal Pulsed RF signal Gaussian pulse signal Average Power Pulse Power Peak Envelope Power
Measuring Pulse Power using Duty cycle Measuring pulse power using duty cycle Pulse power calculation
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