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ULA MUSIC Spectrum

MUSIC spatial spectrum estimator for ULA

  • Library:
  • Phased Array System Toolbox / Direction of Arrival

Description

The ULA MUSIC Spectrum block estimates the spatial spectrum of incoming narrowband signals using the MUSIC algorithm. The algorithm computes the MUSIC pseudo-spectrum of a ULA by scanning a region of broadside angles. The block optionally calculates the direction of arrival (DOA) of a specified number of signals by estimating peaks of the spectrum.

Ports

Input

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Received signal, specified as an M-by-N complex-valued matrix. The quantity M is the number of sample values (snapshots) contained in the signal and N is the number of sensor elements in the array.

The size of the first dimension of this input matrix can vary to simulate a changing signal length, such as a pulse waveform with variable pulse repetition frequency.

Data Types: double
Complex Number Support: Yes

Output

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MUSIC spatial spectrum, returned as a non-negative, real-valued column vector representing the magnitude of the estimated MUSIC spatial spectrum. Each entry corresponds to an angle specified by the Scan angles (deg) parameter.

Data Types: double

Directions of arrival of the signals, returned as a real-valued row vector. The direction of arrival angle is the broadside angle between the source direction and the array axis. Angle units are in degrees. The length of the vector is the number of signals specified by the Number of signals parameter.

Dependencies

Select the Enable DOA output parameter to enable this output port.

Data Types: double

Parameters

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Main Tab

Signal propagation speed, specified as a real-valued positive scalar. The default value of the speed of light is the value return by physconst('LightSpeed').

Specify the operating frequency of the system as a positive scalar. Units are in Hz.

Select this parameter to use forward-backward averaging to estimate the covariance matrix for sensor arrays with a conjugate symmetric array manifold structure.

Specify the amount of averaging used by spatial smoothing to estimate the covariance matrix as a nonnegative integer. Each increase in smoothing handles one extra coherent source, but reduces the effective number of elements by one. The maximum value of this parameter is N – 2, where N is the number of sensors in the ULA.

Specify the scan angles in degrees as a real-valued row vector. The angles are array broadside angles and must lie between –90° and 90°, inclusive. You must specify the angles in increasing order.

Select this parameter to output the signals directions of arrival (DOA) through the Ang output port.

Specify the expected number of signals for DOA estimation as a positive scalar integer.

Block simulation, specified as Interpreted Execution or Code Generation. If you want your block to use the MATLAB® interpreter, choose Interpreted Execution. If you want your block to run as compiled code, choose Code Generation. Compiled code requires time to compile but usually runs faster.

Interpreted execution is useful when you are developing and tuning a model. The block runs the underlying System object™ in MATLAB. You can change and execute your model quickly. When you are satisfied with your results, you can then run the block using Code Generation. Long simulations run faster than in interpreted execution. You can run repeated executions without recompiling. However, if you change any block parameters, then the block automatically recompiles before execution.

When setting this parameter, you must take into account the overall model simulation mode. The table shows how the Simulate using parameter interacts with the overall simulation mode.

When the Simulink® model is in Accelerator mode, the block mode specified using Simulate using overrides the simulation mode.

Acceleration Modes

Block SimulationSimulation Behavior
NormalAcceleratorRapid Accelerator
Interpreted ExecutionThe block executes using the MATLAB interpreter.The block executes using the MATLAB interpreter.Creates a standalone executable from the model.
Code GenerationThe block is compiled.All blocks in the model are compiled.
For more information, see Choosing a Simulation Mode (Simulink) from the Simulink documentation.

Data Types: char

Sensor Array Tab

Method to specify array, specified as Array (no subarrays) or MATLAB expression.

  • Array (no subarrays) — use the block parameters to specify the array.

  • MATLAB expression — create the array using a MATLAB expression.

MATLAB expression used to create an array, specified as a valid Phased Array System Toolbox array System object.

Example: phased.URA('Size',[5,3])

Dependencies

To enable this parameter, set Specify sensor array as to MATLAB expression.

Element Parameters

Antenna or microphone type, specified as one of the following:

  • Isotropic Antenna

  • Cosine Antenna

  • Custom Antenna

  • Omni Microphone

  • Custom Microphone

Specify the operating frequency range of the antenna or microphone element as a 1-by-2 row vector in the form [LowerBound,UpperBound]. The element has no response outside this frequency range. Frequency units are in Hz.

Dependencies

To enable this parameter, set Element type to Isotropic Antenna, Cosine Antenna, or Omni Microphone.

Specify the frequencies at which to set antenna and microphone frequency responses as a 1-by-L row vector of increasing real values. The antenna or microphone element has no response outside the frequency range specified by the minimum and maximum elements of this vector. Frequency units are in Hz.

Dependencies

To enable this parameter, set Element type to Custom Antenna or Custom Microphone. Use Frequency responses (dB) to set the responses at these frequencies.

Select this checkbox to baffle the back response of the element. When backbaffled, the responses at all azimuth angles beyond ±90° from broadside are set to zero. The broadside direction is 0° azimuth angle and 0° elevation angle.

Dependencies

To enable this checkbox, set Element type to Isotropic Antenna or Omni Microphone.

Specify the exponents of the cosine pattern as a nonnegative scalar or a real-valued 1-by-2 matrix of nonnegative values. When you set Exponent of cosine pattern to a 1-by-2 vector, the first element is the exponent for the azimuth direction cosine pattern, and the second element is the exponent for the elevation direction cosine pattern. When you set this parameter to a scalar, both the azimuth direction cosine pattern and the elevation direction cosine pattern are raised to the same power.

Dependencies

To enable this parameter, set Element type to Cosine Antenna.

Frequency response of a custom antenna or custom microphone for the frequencies defined by the Operating frequency vector (Hz) parameter. The dimensions of Frequency responses (dB) must match the dimensions of the vector specified by the Operating frequency vector (Hz) parameter.

Dependencies

To enable this parameter , set Element type to Custom Antenna or Custom Microphone.

Specify the azimuth angles at which to calculate the antenna radiation pattern as a 1-by-P row vector. P must be greater than 2. Azimuth angles must lie between –180° and 180°, inclusive, and be in strictly increasing order.

Dependencies

To enable this parameter, set Element type to Custom Antenna.

Specify the elevation angles at which to compute the radiation pattern as a 1-by-Q vector. Q must be greater than 2. Angle units are in degrees. Elevation angles must lie between –90° and 90°, inclusive, and be in strictly increasing order.

Dependencies

To enable this parameter, set Element type to Custom Antenna.

Magnitude of the combined polarized antenna radiation pattern, specified as a Q-by-P matrix or a Q-by-P-by-L array. The value of Q must equal the value of Q specified by Elevation angles (deg). The value of P must equal the value of P specified by Azimuth angles (deg). The value of L must equal the value of L specified by Operating frequency vector (Hz).

Dependencies

To enable this parameter, set Element type to Custom Antenna.

Response frequencies of the custom microphone of the polar pattern, specified as a real scalar or real-valued 1-by-L vector. The response frequencies lie within the frequency range specified by the Operating frequency vector (Hz) vector.

Dependencies

To enable this parameter, set Element type is set to Custom Microphone.

Specify the polar pattern response angles, as a 1-by-P vector. The angles are measured from the central pickup axis of the microphone and must be between –180° and 180°, inclusive.

Dependencies

To enable this parameter, set Element type to Custom Microphone.

Specify the magnitude of the custom microphone element polar patterns as an L-by-P matrix. L is the number of frequencies specified in Polar pattern frequencies (Hz). P is the number of angles specified in Polar pattern angles (deg). Each row of the matrix represents the magnitude of the polar pattern measured at the corresponding frequency specified in Polar pattern frequencies (Hz) and all angles specified in Polar pattern angles (deg). Assume that the pattern is measured in the azimuth plane. In the azimuth plane, the elevation angle is 0° and the central pickup axis is 0° degrees azimuth and 0° degrees elevation. Assume also that the polar pattern is symmetric around the central axis. You can construct the microphone’s response pattern in 3-D space from the polar pattern.

Dependencies

To enable this parameter, set Element type to Custom Microphone.

Array Parameters

The number of array elements for ULA arrays, specified as an integer greater than or equal to two.

Distance between adjacent ULA elements, specified as a positive scalar. Units are in meters.

Linear axis direction of ULA, specified as y, x, or z. Then, all ULA array elements are uniformly spaced along this axis in the local array coordinate system.

Specify element tapering as a complex-valued scalar or a complex-valued 1-by-N row vector. In this vector, N represents the number of elements in the array.

Also known as element weights, tapers multiply the array element responses. Tapers modify both amplitude and phase of the response to reduce sidelobes or steer the main response axis.

If Taper is a scalar, the same weight is applied to each element. If Taper is a vector, a weight from the vector is applied to the corresponding sensor element. The number of weights must match the number of elements of the array.

Data Types: double

Introduced in R2016b

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