Power Meter

Measure power of voltage signal

• Library:

• DSP System Toolbox / Statistics

• 

Description

The Power Meter block computes the power measurements of a voltage signal. The power measurements include average power, peak power, and peak-to-average power ratio. The block uses the sliding window method to compute these measurements. For more details, see Algorithms.

Ports

Input

Port_1 — Input signal

vector | matrix

Specify the input signal in volts as a vector or a matrix. If x is a matrix, each column is treated as an independent channel. The power measurement is computed along each channel using the Sliding Window Method.

Data Types: single | double
Complex Number Support: Yes

Output

Avg — Average power

vector | matrix

Average power of the voltage signal, returned as a vector or a matrix, and measured in the units determined by the Power units parameter. For details on how the block computes the average power, see Average Power.

Dependencies

To enable this port, set Measurement to Average power or All.

Data Types: single | double

Peak — Peak power

vector | matrix

Peak power of the voltage signal, returned as a vector or a matrix, and measured in the units determined by the Power units parameter. For details on how the block computes the peak power, see Peak Power.

Dependencies

To enable this port, set Measurement to Peak power or All.

Data Types: single | double

PAPR — Peak-to-average power ratio

vector | matrix

Peak-to-average power ratio of the voltage signal, returned as a vector or a matrix. For details on how the block computes the peak-to-average power ratio, see Peak-to-Average Power Ratio.

Dependencies

To enable this port, set Measurement to Peak-to-average power ratio or All.

Data Types: single | double

Parameters

Measurement — Desired power measurement

Average power (default) | Peak power | Peak-to-average power ratio | All

Specify the desired power measurement as one of the following:

• Average power (default)

• Peak power

• Peak-to-average power ratio

• All

For details on how the block computes these measurements, see Algorithms.

Window length — Window length

256 (default) | positive integer

Specify the window length over which the measurement is computed as a positive integer.

Reference load (ohms) — Reference load in ohms

1 (default) | positive scalar in ohms

Specify the reference load that the power meter uses to compute power values as a real, positive scalar in ovohms.

Tunable: Yes

Output power units — Units of measured power values

dBm (default) | dBW | Watts

Specify the units of the measured power values as one of the following:

• dBm

• dBW

• Watts

Simulate using — Type of simulation to run

Code generation (default) | Interpreted execution

Specify the type of simulation to run as one of the following:

• Code generation –– Simulate model using generated C code. The first time you run a simulation, Simulink^® generates C code for the block. The C code is reused for subsequent simulations, as long as the model does not change. This option requires additional startup time but provides faster simulation speed than Interpreted execution.

• Interpreted execution –– Simulate model using the MATLAB^®  interpreter. This option shortens startup time but has slower simulation speed than Code generation.

Model Examples

Compute Power Measurements of Voltage Signal in Simulink

Compute average power, peak power, and peak-to-average power ratio of voltage signal.

Open Script

Block Characteristics

Data Types	double | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	yes
Zero-Crossing Detection	no

Algorithms

Sliding Window Method

In the sliding window method, the power measurement is computed over a finite duration of the signal. The window length defines the length of the data over which the algorithm computes the power value. The window moves as the new data comes in. The output for each input sample is the measurement done over the current sample and the Len – 1 previous samples. Len is the length of the sliding window in samples. To compute the first Len – 1 outputs, when the window does not have enough data yet, the algorithm fills the window with zeros. As an example, to compute the average power when the second input sample comes in, the algorithm fills the window with Len – 2 zeros. The input signal x is then the two data samples followed by Len – 2 zeros.

For a more detailed example, see Sliding Window Method.

If the window is large, the power computed is closer to the stationary power of the data. For data that does not change rapidly, use a long window to get a smoother measurement. For data that changes fast, use a smaller window.

Average Power

The average power of the voltage signal is computed using the Sliding Window Method and is given by the following equations:

$$AvgPowe{r}_{dBm}=10{\log }_{10}\left(\mathrm{movAvg}\left({\left|x\right|}^2\right)/R\right)+30$$

$$AvgPowe{r}_{dBW}=10{\log }_{10}\left(\mathrm{movAvg}\left({\left|x\right|}^2\right)/R\right)$$

$$AvgPowe{r}_{Watts}=\mathrm{movAvg}\left({\left|x\right|}^2\right)/R$$

where,

• x is the input voltage signal.

• R is the reference load (in ohms) that is used to compute the power value.

• movAvg computes the moving average using the sliding window method. The powermeter object in MATLAB uses the dsp.MovingAverage object and the Power Meter block in Simulink uses the Moving Average block.

Peak Power

The peak power of the voltage signal is computed using the Sliding Window Method and is given by the following equations:

$$PeakPowe{r}_{dBm}=10{\log }_{10}\left(\mathrm{movMax}\left({\left|x\right|}^2\right)/R\right)+30$$

$$PeakPowe{r}_{dBW}=10{\log }_{10}\left(\mathrm{movMax}\left({\left|x\right|}^2\right)/R\right)$$

$$PeakPowe{r}_{Watts}=\mathrm{movMax}\left({\left|x\right|}^2\right)/R$$

where,

• x is the input voltage signal.

• R is the reference load (in ohms) that is used to compute the power value.

• movMax computes the moving maximum using the sliding window method. The powermeter object in MATLAB uses the dsp.MovingMaximum object and the Power Meter block in Simulink uses the Moving Maximum block.

Peak-to-Average Power Ratio

The peak-to-average power ratio of the voltage signal is computed using the Sliding Window Method and is given by the following equations:

$$pkAvgPw{r}_{dBm}=10{\log }_{10}\left(\mathrm{movMax}\left({\left|x\right|}^2\right)/\mathrm{movAvg}\left({\left|x\right|}^2\right)\right)$$

$$pkAvgPw{r}_{dBW}=10{\log }_{10}\left(\mathrm{movMax}\left({\left|x\right|}^2\right)/\mathrm{movAvg}\left({\left|x\right|}^2\right)\right)$$

$$pkAvgPw{r}_{Watts}=\mathrm{movMax}\left({\left|x\right|}^2\right)/\mathrm{movAvg}\left({\left|x\right|}^2\right)$$

where,

• x is the input voltage signal.

• movAvg computes the moving average using the sliding window method. The powermeter object in MATLAB uses the dsp.MovingAverage object and the Power Meter block in Simulink uses the Moving Average block.

• movMax computes the moving maximum using the sliding window method. The powermeter object in MATLAB uses the dsp.MovingMaximum object and the Power Meter block in Simulink uses the Moving Maximum block.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2021a