PRBS Signal Generator
Formation of a pseudo-random binary sequence.
Description
Block PRBS Signal Generator generates a pseudorandom binary sequence for the task of frequency analysis. This test signal allows you to reduce the time of the experiment to obtain the frequency response of the system under study (control object) compared to a set of sinusoidal signals as a test signal with comparable results of the experiment. The block provides automatic generation of values of the main parameters based on the set frequencies to accelerate the process of setting up the experiment. The pseudo-random binary sequence is excellent for obtaining the frequency response of communication and power electronics devices.
Ports
Input
#
start/stop
—
start/stop signal
`scalar
Details
The signal to start and stop the experiment. When the signal changes:
-
from a negative value or
0to a positive value, the experiment is started. -
from positive value to
0or negative value, the experiment is stopped.
When the experiment is not started, the unit does not generate a test signal.
The experiment should continue long enough to obtain quality frequency responses at all specified frequencies. Recommended experiment duration:
where
-
- sampling period of the generated signal, determined by the parameters Sample time (Ts);
-
- order of the generated signal determined by the parameters Signal order;
-
- number of periods of the generated signal defined by the parameters Auto-generated number of periods.
During the experiment, exclude the influence of disturbing influences on the system under study (control object), as they can lead to distortion of the output signal and reduce the quality of the frequency response.
| Data types |
|
| Complex numbers support |
No |
Output
#
prbs
—
test signal
scalar
Details
A pseudorandom binary sequence.
| Data types |
|
| Complex numbers support |
No |
Parameters
Block Settings
# Sample time (Ts) — sampling period
Details
The sampling period of the generated signals.
The highest frequency at which a frequency response can be obtained is limited by the minimum allowable sampling frequency of the signal (rad/s). As a rule, specify a sampling period of five times the minimum allowable sampling frequency:
where
-
- is the highest frequency in the frequency set defined by the Frequencies parameters, rad/s.
-
- is the highest frequency in the frequency set, Hz.
The sampling period should be small enough to correctly determine the frequency response at the maximum desired frequency. But it should not be too small, so that the cost of computing resources does not increase.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
Excitation Signal Settings
# Frequencies — frequency set
Details
A set of desired frequencies at which it is required to obtain the frequency response of the system (control object) under study. The unit generates a test signal of each frequency from the specified set. The highest frequency at which it is possible to obtain a frequency response is limited by the minimum allowable sampling frequency of the signal (rad/s), where is the sampling period determined by the parameters Sample time (Ts).
The range of frequencies affects the duration of the experiment. The lowest frequency of the set determines the minimum signal order that can cover a given frequency. Decreasing the smallest frequency increases the required signal order and therefore increases the duration of the experiment. Increasing the number of frequencies in the set does not increase the duration of the experiment.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
#
Units —
frequency unit
rad/s | Hz
Details
A unit of frequency measurement.
| Values |
|
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
# Amplitudes — signal amplitudes
Details
Amplitude (amplitudes) of generated signals. To specify the same amplitude of signals for all frequencies, specify one value (scalar) in the field. If you know that the frequency response varies significantly with frequency, then specify the amplitudes of signals as a set (vector) for each desired frequency. For example, you might specify a smaller amplitude near the resonant frequency and a larger amplitude at a frequency greater than the frequency response decay frequency. The number of amplitudes must be equal to the number of frequencies in the set defined by the parameters Frequencies.
The amplitudes must:
-
large enough to eliminate the effects of any dead zones and at the same time obtain a frequency response at frequencies above the noise level.
-
small enough so that the system under study (control object) remains in the linear region near the operating point.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
Signal Generation Settings
# Number of periods — number of periods
Details
The number of periods of a pseudo-random binary sequence. A positive number greater than zero.
Dependencies
To use this parameter, select the checkbox Auto-generated number of periods.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
# Signal order — signal order
Details
The order of the generated signal. A positive number greater than zero.
The maximum signal length is , where is the signal order. The signal order should be large enough to obtain a good quality frequency response. In order not to make the experiment last too long, it is worth limiting yourself to 24 orders.
Dependencies
To use this parameters, tick the checkbox. Auto-generated signal order.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
# Auto-generated number of periods — automatic selection of the number of periods
Details
This function automatically determines the number of periods based on the specified frequency set and sampling period. This function can be useful when you run multiple experiments with different frequency sets or sampling periods.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |
# Auto-generated signal order — automatic signal order selection
Details
This function automatically determines the signal order based on the specified frequency set and sampling period. This function can be useful if you run multiple experiments with different frequency sets or sampling periods.
| Default value |
|
| Program usage name |
|
| Tunable |
No |
| Evaluatable |
Yes |