# Power Meter

Measure power and the CCDF of the power of voltage signal in Simulink

• Library:
• DSP System Toolbox / Statistics

## Description

The Power Meter block computes the power measurements of a voltage signal. When you select the Compute CCDF parameter, the block also calculates the complementary cumulative distribution function (CCDF) of the power of a voltage signal. The CCDF measurements that the block outputs are relative power and probability (in percentage). The power measurements include average power, peak power, and peak-to-average power ratio.

For more details on how the block computes the power measurements and the CCDF measurements, see Algorithms.

## Ports

### Input

expand all

Specify the input signal in volts as a vector or a matrix. If `x` is a matrix, the block treats each column as an independent channel and computes the power measurement along each channel.

When the Allow arbitrary frame length for fixed-size input signals parameter appears and is not selected, and you input a fixed-size signal, the frame length must be a multiple of the hop size (window length − overlap length). In all other cases, the input frame length can be arbitrary.

The block accepts variable-size inputs (frame length changes during simulation). When you input a variable-size signal, the frame length of the signal can be arbitrary.

Data Types: `single` | `double`
Complex Number Support: Yes

Specify the boolean reset signal as a scalar. If the input on the Rst port is `true`, the block clears the internal histograms and statistics before processing the current input. If the input on the Rst port is `false`, the block computes the measurements from the start of the simulation or from the last reset.

#### Dependencies

To enable this port, select the Compute CCDF and Reset port parameters.

Data Types: `Boolean`

### Output

expand all

Average power of the voltage signal from the start of the simulation or from the last reset, returned as a scalar, vector, or a matrix. The block computes the average power along each channel in the units specified in the Output power units parameter. For details on how the block computes the average power, see Average Power.

If you clear the Compute CCDF parameter, the block computes the moving average power using the Sliding Window Method.

See this table for details on the output signal dimensions.

Input SignalInput DimensionsOutput Dimensions When Allow arbitrary frame length for fixed-size input signals AppearsOutput Dimensions When Allow arbitrary frame length for fixed-size input signals Does Not Appear
Fixed-size signalP-by-M, where M is a multiple of the hop size (window length − overlap length)

(P/hop size)-by-M

P-by-M

Fixed-size signalP-by-M, where M is not a multiple of the hop size (window length − overlap length)

`ceil`(P/hop size)-by-M when you select Allow arbitrary frame length for fixed-size input signals

If you do not select Allow arbitrary frame length for fixed-size input signals, the block errors.

P-by-M

Variable-size signalP-by-M `ceil`(P/hop size)-by-M

P-by-M

When the output has an upper bound size of `ceil`(P/hop size)-by-M, during simulation, the size of the first dimension varies within this bound, while the size of the second dimension remains constant.

If you select the Compute CCDF parameter, the block computes the stationary average power of the entire signal along each channel. In this case, the size of the output is 1-by-M, where M is the number of channels (columns) in the input signal.

#### Dependencies

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

Data Types: `single` | `double`

Peak power of the voltage signal from the start of the simulation or from the last reset, returned as a scalar, vector, or a matrix. The block computes the peak power along each channel in the units specified in the Output power units parameter. For details on how the block computes the peak power, see Peak Power.

If you clear the Compute CCDF parameter, the block computes the moving peak power using the Sliding Window Method.

See this table for details on the output signal dimensions.

Input SignalInput DimensionsOutput Dimensions When Allow arbitrary frame length for fixed-size input signals AppearsOutput Dimensions When Allow arbitrary frame length for fixed-size input signals Does Not Appear
Fixed-size signalP-by-M, where M is a multiple of the hop size (window length − overlap length)

(P/hop size)-by-M

P-by-M

Fixed-size signalP-by-M, where M is not a multiple of the hop size (window length − overlap length)

`ceil`(P/hop size)-by-M when you select Allow arbitrary frame length for fixed-size input signals

If you do not select Allow arbitrary frame length for fixed-size input signals, the block errors.

P-by-M

Variable-size signalP-by-M `ceil`(P/hop size)-by-M

P-by-M

When the output has an upper bound size of `ceil`(P/hop size)-by-M, during simulation, the size of the first dimension varies within this bound, while the size of the second dimension remains constant.

If you select the Compute CCDF parameter, the block computes the stationary peak power of the entire signal along each channel. In this case, the size of the output is 1-by-M, where M is the number of channels (columns) in the input signal.

#### Dependencies

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

Data Types: `single` | `double`

Ratio of the peak power to the average power (PAPR) of the voltage signal, returned as a scalar, vector, or a matrix. The block computes the peak-to-average power ratio along each channel. For details on how the block computes this measurement, see Peak-to-Average Power Ratio.

If you clear the Compute CCDF parameter, the block computes the moving peak-to-average power ratio using the Sliding Window Method.

See this table for details on the output signal dimensions.

Input SignalInput DimensionsOutput Dimensions When Allow arbitrary frame length for fixed-size input signals AppearsOutput Dimensions When Allow arbitrary frame length for fixed-size input signals Does Not Appear
Fixed-size signalP-by-M, where M is a multiple of the hop size (window length − overlap length)

(P/hop size)-by-M

P-by-M

Fixed-size signalP-by-M, where M is not a multiple of the hop size (window length − overlap length)

`ceil`(P/hop size)-by-M when you select Allow arbitrary frame length for fixed-size input signals

If you do not select Allow arbitrary frame length for fixed-size input signals, the block errors.

P-by-M

Variable-size signalP-by-M `ceil`(P/hop size)-by-M

P-by-M

When the output has an upper bound size of `ceil`(P/hop size)-by-M, during simulation, the size of the first dimension varies within this bound, while the size of the second dimension remains constant.

If you select the Compute CCDF parameter, the block computes the stationary peak-to-average power ratio of the entire signal along each channel. In this case, the size of the output is 1-by-M, where M is the number of channels (columns) in the input signal.

PAPR should be less that 100 dB to obtain accurate CCDF measurements. If PAPR is above 100 dB, the block shows only the highest 100 dB power levels.

#### Dependencies

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

Data Types: `single` | `double`

Relative power (dB above average power), returned as an N-by-M matrix, where:

• M is the number of channels (columns) in the input signal.

• When you set CCDF output to ```Relative power (dB above average power)```, N equals the length of the column vector that you specify in the Specify probability (%) for relative power output parameter.

• When you set CCDF output to ```Relative power and probability (whole CCDF curve)```, N equals `ceil`(Power range (dB)/Power resolution (dB)) + 1.

Relative power is the power in dB by which the instantaneous signal power is above the average signal power with a probability of Prob, expressed as a percentage. For details on how the block computes relative power, see Relative Power.

#### Dependencies

To enable this port, select the Compute CCDF parameter and then set the CCDF output parameter to ```Relative power (dB above average power)``` or ```Relative power and probability (whole CCDF curve)```.

Data Types: `single` | `double`

Probability in percentage, returned as an N-by-M matrix, where:

• M is the number of channels (columns) in the input signal.

• When you set CCDF output to ```Probability (%)```, N equals the length of the column vector that you specify in the Specify relative power (dB) for probability output parameter.

• When you set CCDF output to ```Relative power and probability (whole CCDF curve)```, N equals `ceil`(Power range (dB)/Power resolution (dB)) + 1.

Prob(i)/100 is the probability that the instantaneous signal power of the jth channel is above its average signal power by RelPwr(i,j) in dB.

#### Dependencies

To enable this port, select the Compute CCDF parameter and then set the CCDF output parameter to ```Probability (%)``` or ```Relative power and probability (whole CCDF curve)```.

Data Types: `single` | `double`

## Parameters

expand 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.

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

Tunable: Yes

Data Types: `single` | `double`

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

• `dBm`

• `dBW`

• `Watts`

Select the Compute CCDF parameter to enable the block to compute the CCDF of the power of voltage signals. CCDF measurements include the relative power and the probability (in percentage). Relative power is the amount of power in dB by which the instantaneous signal power is above the average signal power. Probability in percentage refers to the probability that the instantaneous signal power is above the average signal power by the relative power in dB.

These measurements provide a qualitative way to view the power distribution between the amplitude values of an input signal over time. The CCDF curves (plot of probability in percentage against relative power in dB) are useful indicators of the dynamic range of a signal.

When you select Compute CCDF:

• The block uses all the input samples from the start of the simulation or from a reset signal on the Rst port to compute the statistics. The power measurements are stationary.

• You can specify variable-size input signals.

When you clear Compute CCDF,

• The block does not calculate the CCDF measurements and computes the power measurements using the Sliding Window Method.

• The block accepts input signals of arbitrary frame length only when you select the Allow arbitrary frame length for fixed-size input signals parameter.

Specify the window length over which the block computes the measurement as a positive integer.

#### Dependencies

To enable this parameter, clear the Compute CCDF check box. When you select Compute CCDF, Window length becomes `Inf`.

Data Types: `single` | `double`

Specify the overlap length between sliding windows as a nonnegative integer. The value of overlap length varies in the range [0, Window length − 1].

#### Dependencies

To enable this parameter, clear the Compute CCDF check box. When you select Compute CCDF, Overlap length becomes `0`.

Data Types: `single` | `double`

Specify whether fixed-size input signals (whose size does not change during simulation) can have an arbitrary frame length, where the frame length does not have to be multiple of the hop size. Hop size is defined as Window lengthOverlap length. The block uses this parameter setting only for fixed-size input signals and ignores this parameter if the input has a variable-size.

When the input signal is a variable-size signal, the signal can have arbitrary frame length, that is, the frame length does not have to be a multiple of the hop size.

For fixed-size input signals, if you:

• Select the Allow arbitrary frame length for fixed-size input signals parameter, the frame length of the signal does not have to be a multiple of the hop size. If the input is not a multiple of the hop size, then the output is generally a variable-size signal. Therefore, to support arbitrary input size, the block must also support variable-size operations, which you can enable by selecting the Allow arbitrary frame length for fixed-size input signals parameter.

• Clear the Allow arbitrary frame length for fixed-size input signals parameter, the input frame length must be a multiple of the hop size.

#### Dependencies

To enable this parameter, clear the Compute CCDF parameter.

Specify the x-axis range of the CCDF curves as a positive scalar in dB. The CCDF curves end at the maximum relative power, namely, the PAPR of the signal, and start at PAPR − Power range (dB). In the CCDF capability of the Power Meter block, relative power is the power in dB by which the instantaneous signal power is above the average signal power.

#### Dependencies

To enable this parameter, select the Compute CCDF check box.

Data Types: `single` | `double`

Specify the x-axis resolution of the CCDF curves as a positive scalar in dB.

#### Dependencies

To enable this parameter, select the Compute CCDF check box.

Data Types: `single` | `double`

Specify the block to output:

• RelPwr –– Relative power (dB above average power). This is the amount of power in dB by which the instantaneous signal power is above the average power.

• Prob –– Probability in percentage. This is the probability that the instantaneous signal power is above the average signal power by the value of the relative power in dB.

• Both the RelPwr and the Prob.

#### Dependencies

To enable this parameter, select the Compute CCDF check box.

Specify the probability (in percentage) for the relative power output as a column vector. The length of this vector determines the number of rows in the relative power output at the RelPwr port.

#### Dependencies

To enable this parameter, select the Compute CCDF check box and set the CCDF output parameter to ```Relative power (dB above average power)```.

This also enables the RelPwr output port.

Data Types: `single` | `double`

Specify the relative power (in dB) for the probability output as a column vector. The length of this vector determines the number of rows in the probability output at the Prob port.

#### Dependencies

To enable this parameter, select the Compute CCDF check box and set the CCDF output parameter to ```Probability (%)```.

This also enables the Prob output port.

Data Types: `single` | `double`

Select this parameter to enable the input port Rst that accepts a boolean signal. If the value at the Rst port is `true`, then the block clears the internal histograms and statistics before processing the current input.

#### Dependencies

To enable this parameter, select the Compute CCDF check box.

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`.

## Block Characteristics

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

expand all

## Version History

Introduced in R2021a

expand all