LMH2120_15 Datasheet, PDF (23/34 Pages) Texas Instruments – LMH2120 6 GHz Linear RMS Power Detector with 40 dB Dynamic Range

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P_INT = RF_IN at V_OUT is 0 dBV (1V)
P_INT
1
LMH2120
SNWS021C – JULY 2010 – REVISED FEBRUARY 2013
0.1 Detector
response
K_SLOPE
Ideal LIN function
0.01
-50 -40 -30 -20 -10 0 10
RF INPUT POWER (dBm)
Figure 60. Ideal Linear Response
To determine the linear conformance error two steps are required:
1. Determine the best fitted line at 25°C.
2. Determine the difference between the actual data and the best fitted line.
The best fit can be determined by standard routines. A careful selection of the fit range is important. The fit range
should be within the normal range of operation of the device. Outcome of the fit is K_SLOPE and P_INT.
Subsequently, the difference between the actual data and the best fitted line is determined. The linear
conformance is specified as an input referred error. The output referred error is therefore divided by the K_SLOPE to
obtain the input referred error. The linear conformance error is calculated by the following equation:
( ) ^VOUT (T) ^{- K}SLOPE 25°C ^PIN ^{- P}INT 25°C
E_LC(T) =
K_{SLOPE 25°C}
(13)
where V_{OUT (T)} is the measured output voltage at a power level at P_IN at a specific temperature. K_{SLOPE 25°C}
(dB/dB) and P_{INT 25°C} (dBm) are the parameters of the best fitted line of the 25°C transfer.
Figure 61 shows that both the error with respect to the ideal LIN response as well as the error due to
temperature variation are included in this error metric. This is because the measured data for all temperatures is
compared to the fitted line at 25°C. The measurement result of a typical LMH2120 in Figure 61 shows a dynamic
range of 35 dB for E_LC= ±1dB.
3
2
1
85°C
25°C
0
-1
-40°C
-2
-3
-50 -40 -30 -20 -10 0 10
RF INPUT POWER (dBm)
Figure 61. E_LC vs. RF input Power at 1900 MHz
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