Anritsu MA24106A, 0701012 manual High Crest Factor Signals peak to average ratio, Multitone Signals

Using the Power Sensor Measurement Considerations

High Crest Factor Signals (peak to average ratio)

High crest factor signals, such as CDMA/WCDMA, may have crest factors as high as 10 dB. To ensure the most accurate power measurement, the statistically-low peak signals should not exceed +30 dBm.

For example, if a signal has an expected crest factor of 10 dB, then the highest average power measured should not exceed +20 dBm. A sensor’s linearity graph of a WCDMA (TestModel_5_8HSPDSCH) signal with 10 dB crest factor is shown below:

			2GHz WCDMA Linearity
			TestModel_5_8HSPDSCH
					0.7
					0.6
					0.5
					0.4
					0.3
(dB)					0.2
					0.1
Variance					0.0
	-40	-30	-20	-10	-0.1 0	10	20
					-0.2
					-0.3
					-0.4
					-0.5
					-0.6
					-0.7
				Input Power (dBm)

Figure 3-20.Sensor Linearity Graph

Multitone Signals

The MA24106A is a True-RMS sensor that can measure very wide bandwidth modulation without much restriction. The only limitation is the frequency flatness of the sensor. Because the sensor’s sensitivity is not identical for all frequencies and when measuring multi-tone signals, the frequency entered into the sensor’s application should be the average frequency of all significant tones. The MA24106A has an error of 0.01 dB for every 100 MHz bandwidth at frequencies below 3 GHz, and an error of 0.03 dB for every 100 MHz bandwidth at frequencies above 3 GHz.

For example, a dual tone signal of 2.0 GHz and 2.2 GHz may have an additional measurement error of 0.02 dB (0.01 dB ⋅ 2) when the application frequency is set to 2.1 GHz.

Noise and Averaging

When there is a need to achieve a required reading resolution, particularly at low power levels, averaging is often needed to reduce noise and steady the displayed power reading. Use the noise vs. resolution table in the sensor manual (Using the Power SensorMaking MeasurementsOptimizing the Readings) to determine the number of averages that will typically be required for a given resolution. Alternatively, determine the number of averages through calculation by using the noise specifications and the fact that noise will be proportional to the square root of N, where N is the number of averages.

MA24106A UG 3-15