HMC714LP5 Datasheet, PDF (39/40 Pages) Hittite Microwave Corporation – DUAL RMS POWER DETECTOR 0.1 - 3.9 GHz

v05.0309
HMC714LP5 / 714LP5E
DUAL RMS POWER DETECTOR
0.1 - 3.9 GHz
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System Calibration
Due to part-to-part variations in log-slope and log-intercept, a system-level calibration is recommended to satisfy
absolute accuracy requirements. When performing this calibration, choose at least two test points: near the top-end
and bottom-end of the measurement range. It is best to measure the calibration points in the regions (of frequency and
amplitude) where accuracy is most important. Derive the log-slope and log-intercept, and store them in non-volatile
memory. Calibrate iPAR scaling by measuring the peak-to-average ratio of a known signal.
For example if the following two calibration points were measured at 2.35 GHz:
With Vrms = 2.34V at Pin= -7dBm,
Now performing a power measurement:
and Vrms=1.84V at Pin= -16dBm
Slope Calibration Constant = SCC
SCC = (-16+7)/(1.84-2.34) = 18 dB/V
Vrms measures 2.13V
[Measured Pin] = [Measured Vrms]*SCC + ICC
[Measured Pin] = 2.13*18.0 – 49.12 = -10.78dBm
Intercept Calibration Constant = ICC
An error of only 0.22dB
ICC = Pin – SCC*Vrms = -7 – 18.0 * 2.34 = -49.12dBm
Factory system calibration measurements should be made using an input signal representative of the application. If
the power detector will operate over a wide range of frequencies, choose a central frequency for calibration.
Layout Considerations
• Mount RF input coupling capacitors close to the IN+ and IN- pins.
• Solder the heat slug on the package underside to a grounded island which can draw heat away from the die
with low thermal impedance. The grounded island should be at RF ground potential.
• Connect power detector ground to the RF ground plane, and mount the supply decoupling capacitors close
to the supply pins.
Defi nitions:
• Log-slope: slope of PIN –> V_RMS transfer characteristic. In units of mV/dB
• Log-intercept: x-axis intercept of P_IN –> V_RMS transfer characteristic. In units of dBm.
• RMS Output Error: The difference between the measured P_IN and actual P_IN using a line of best fit.
[measured_P_IN] = [measured_V_RMS] / [best-fit-slope] + [best-fit-intercept], dBm
• Input Dynamic Range: the range of average input power for which there is a corresponding RMS output
voltage with “RMS Output Error” falling within a specific error tolerance.
• Crest Factor: Peak power to average power ratio for time-varying signals.
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20 Alpha Road, Chelmsford, MA 01824 Phone: [phone] Fax: [phone]
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