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phased.WidebandCollector System object

Package: phased

Wideband signal collector

Description

The WidebandCollector object implements a wideband signal collector.

To compute the collected signal at the sensor(s):

  1. Define and set up your wideband signal collector using the syntax defined in Construction below.

  2. Call step to collect the signal according to the properties of phased.WidebandCollector. The behavior of step is specific to each object in the toolbox.

    Note:   Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Construction

H = phased.WidebandCollector creates a wideband signal collector System object, H. The object collects incident wideband signals from given directions using a sensor array or a single element.

H = phased.WidebandCollector(Name,Value) creates a wideband signal collector object, H, with each specified property Name set to the specified Value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

Properties

Sensor

Sensor element or sensor array

Sensor element or sensor array specified as a System object in the Phased Array System Toolbox™. A sensor array can contain subarrays.

Antenna Toolbox™ antenna

Default: phased.ULA with default property values

PropagationSpeed

Signal propagation speed

Specify the propagation speed of the signal, in meters per second, as a positive scalar.

Default: Speed of light

SampleRate

Sample rate

Specify the sample rate, in hertz, as a positive scalar. The default value corresponds to 1 MHz.

Default: 1e6

ModulatedInput

Assume modulated input

Set this property to true to indicate the input signal is demodulated at a carrier frequency.

Default: true

CarrierFrequency

Carrier frequency

Specify the carrier frequency (in hertz) as a positive scalar. The default value of this property corresponds to 1 GHz. This property applies when the ModulatedInput property is true.

Default: 1e9

WeightsInputPort

Enable weights input

To specify weights, set this property to true and use the corresponding input argument when you invoke step. If you do not want to specify weights, set this property to false.

Default: false

EnablePolarization

Enable polarization

Set this property to true to simulate the collection of polarized waves. Set this property to false to ignore polarization. This property applies when the sensor specified in the Sensor property is capable of simulating polarization.

Default: false

NumSubbands

Number of subbands

Number of processing subbands, specified as a positive integer.

Default: 64

Wavefront

Type of incoming wavefront

Specify the type of incoming wavefront as one of 'Plane', or 'Unspecified':

  • If you set the Wavefront property to 'Plane', the input signals are multiple plane waves impinging on the entire array. Each plane wave is received by all collecting elements. If the Sensor property is an array that contains subarrays, the Wavefront property must be 'Plane'.

  • If you set the Wavefront property to 'Unspecified', the input signals are individual waves impinging on individual sensors.

Default: 'Plane'

Methods

cloneCreate wideband collector object with same property values
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
isLockedLocked status for input attributes and nontunable properties
releaseAllow property value and input characteristics changes
stepCollect signals

Definitions

Subband Frequency Processing

Subband processing decomposes a wideband signal into multiple subbands and applies narrowband processing to the signal in each subband. The signals for all subbands are summed to form the output signal.

When using wideband frequency System objects, you specify the number of subbands, Nb, in which to decompose the wideband signal. The NumSubbands property specifies the number of subbands. Subband center frequencies and widths are automatically computed from the total bandwidth and number of subbands. The total frequency band is centered on the carrier frequency, fc, specified by the OperatingFrequency property. The overall bandwidth is given by the sample rate, fs, specified by the SampleRate property. Frequency subband widths are Δf = fs/NB. The center frequencies of the subbands are

fm={fcfs2+(m1)Δf,   NB evenfc(N1)fs2N+(m1)Δf,   NB odd,m=1,,NB

Subbands are ordered by frequency. Frequencies above the carrier appear first, followed by frequencies below the carrier. This order is consistent with the ordering of the discrete Fourier transform.

The phased.WidebandCollector System object uses the narrowband phased approximation of the time delays across receiving elements in the far field for each subband.

Examples

expand all

Use the wideband collector to construct the signal impinging upon a single isotropic antenna from 10 degrees azimuth and 30 degrees elevation.

sIso = phased.IsotropicAntennaElement;
sColl = phased.WidebandCollector('Sensor',sIso);
x = [1;1;1];
incidentAngle = [10;30];
y = step(sColl,x,incidentAngle);
disp(y)
   1.0000 + 0.0000i
   1.0000 + 0.0000i
   1.0000 + 0.0000i

Use the wideband collector to construct the signal impinging upon a 5-element ULA of isotropic antennas from 10 degrees azimuth and 30 degrees elevation.

sULA = phased.ULA('NumElements',5);
sColl = phased.WidebandCollector('Sensor',sULA);
x = [1;1;1];
incidentAngle = [10;30];
y = step(sColl,x,incidentAngle);
disp(y)
  Columns 1 through 4

  -0.9997 + 0.0102i  -0.0051 - 0.9999i   1.0000 + 0.0000i  -0.0051 + 1.0001i
  -0.9999 + 0.0102i  -0.0051 - 1.0000i   1.0000 + 0.0000i  -0.0051 + 1.0000i
  -1.0002 + 0.0102i  -0.0051 - 1.0001i   1.0000 - 0.0000i  -0.0051 + 0.9999i

  Column 5

  -1.0002 - 0.0102i
  -0.9999 - 0.0102i
  -0.9997 - 0.0102i

Collect three signals incoming into a 3-element array of isotropic antenna elements. Each antenna collects a separate input signal from a separate direction.

sULA = phased.ULA('NumElements',3);
sColl = phased.WidebandCollector('Sensor',sULA,...
    'Wavefront','Unspecified');
rng default
x = rand(10,3);
incidentAngles = [10 20 45; 0 5 2];
y = step(sColl,x,incidentAngles)
y =

   0.8147 + 0.0000i   0.1576 + 0.0000i   0.6557 + 0.0000i
   0.9058 + 0.0000i   0.9706 + 0.0000i   0.0357 + 0.0000i
   0.1270 + 0.0000i   0.9572 + 0.0000i   0.8491 + 0.0000i
   0.9134 + 0.0000i   0.4854 + 0.0000i   0.9340 + 0.0000i
   0.6324 + 0.0000i   0.8003 + 0.0000i   0.6787 + 0.0000i
   0.0975 + 0.0000i   0.1419 + 0.0000i   0.7577 + 0.0000i
   0.2785 + 0.0000i   0.4218 + 0.0000i   0.7431 + 0.0000i
   0.5469 + 0.0000i   0.9157 + 0.0000i   0.3922 + 0.0000i
   0.9575 + 0.0000i   0.7922 + 0.0000i   0.6555 + 0.0000i
   0.9649 + 0.0000i   0.9595 + 0.0000i   0.1712 + 0.0000i

Algorithms

If the Wavefront property value is 'Plane', phased.WidebandCollector does the following for each plane wave signal:

  1. Decomposes the signal into multiple subbands.

  2. Uses the phase approximation of the time delays across collecting elements in the far field for each subband.

  3. Regroups the collected signals in all the subbands to form the output signal.

If the Wavefront property value is 'Unspecified', phased.Wideband Collector collects each channel independently.

For further details, see [1].

References

[1] Van Trees, H. Optimum Array Processing. New York: Wiley-Interscience, 2002.

Introduced in R2012a

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