>>> 3010 POWER METER OPTION <<<

  The 3010 Power Meter Option makes possible a measurement of the 3010 front panel RF Input power.  By connecting a DVM to the back panel BNC connector, RF input power levels in the -21 to 0 dBm range for frequencies from 50 to 500 MHz are displayed.  The rear panel BNC output calibration is 0.2 dBm per volt.  To  remove the scaling factor from the BNC output, multiply the DVM display value by 5.   For example, a -12 dBm RF input power level produces a -2.4 VDC level at the rear panel BNC connector so to convert to dBm multiplying by 5 yields  -12 dBm.  The plot of Figure 1 shows typical accuracy at 100 MHz and Figure 2 shows typical accuracy at -12 dBm RF input for frequencies from 100 to 1000 MHz.

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Figure 1, Typical Accuracy @ 100 MHz

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Figure 2, Typical Accuracy @ -12 dBm Input

  To understand how a power measurement is accomplished with the 3010 Power Meter Option, a review of the 3010 Automatic Level Control (ALC) function is necessary.  The function of the ALC (Figure 3) is to keep the power level at the input of the ECL Prescaler IC at a preset level determined by a RF detector, DC comparator, and PIN diode driver over a wide range of input power levels.  The Bridged Tee Attenuator of Figure 4 is placed ahead of the RF amplifier to keep it from being driven into gain compression.  By controlling the current through each PIN diode of the Bridged Tee Attenuator in a predetermined method, the attenuation is changed while maintaining the input and out match at 50 ohms.

Figure 3, 3010 Automatic Level Control Circuit Diagram

   When the input power level to the 3010 RF Input is increased, the change in level is detected by D4 of Figure 4, and the result is processed by U1 and U2 (Figure 3) so that an error voltage is generated that forces the PIN diode driver circuit to decreases the current through PIN diode A and at the same time increasing current through PIN diode B to increase attenuation keeping the input amplitude of the ECL Prescaler IC of Figure 4 at the required level.

 

Figure 4, 3010 RF and Logic Circuit Diagram

  Refer to Figure 5 for the following explanation.  The DC voltage across a PIN diode is a logarithmic function of the DC current through the diode so the voltage across PIN diode B follows a logarithmic increase as attenuation is increased.  To remove the DC offset of PIN diode B and provide temperature compensation, the voltage across PIN diode R which is included on the RF/ Logic board for temperature compensation is reduced by approximately 1/2 by R3 and connected to the non-inverting input of U1A.  R1, R2, R3, and U1A form a Differential Amplifier that supplies the required input to an Inverting Amplifier formed by R4, R7, and U1B that provides the 0.2 dB/volt slope.  R5 and R6 are used for calibration.  A power measurement is the 3010 threshold sensitivity plus the amount of power removed by the Bridged Tee Attenuator.

Figure 5, 3010 Power Meter Option Circuit Diagram

 

This item is the 3010 Power Meter Option only.  The 3010 Prescaler can be ordered separately by clicking on the 3010 Prescaler Page hyperlink shown below.  For online ordering, a US ship to address is required.

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3010 Prescaler Page

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