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phased.TimeVaryingGain System object

Package: phased

Time varying gain control

Description

The TimeVaryingGain object applies a time varying gain to input signals. Time varying gain (TVG) is sometimes called automatic gain control (AGC).

To apply the time varying gain to the signal:

  1. Define and set up your time varying gain controller. See Construction.

  2. Call step to apply the time varying gain according to the properties of phased.TimeVaryingGain. 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.TimeVaryingGain creates a time varying gain control System object, H. The object applies a time varying gain to the input signal to compensate for the signal power loss due to the range.

H = phased.TimeVaryingGain(Name,Value) creates an 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

RangeLossSource

Source of range losses

Specify the source of range losses as either 'Property' or 'Input port'. When you specify RangeLossSource as 'Property', the range loss for each sample is set in the RangeLoss property. When you specify the RangeLossSource as 'Input port', the range losses are specified using an input argument to the step method.

Default: 'Property'

RangeLoss

Loss at each input sample range

Specify the loss due to range as a vector — elements correspond to the samples in the input signal. Units are in dB.

Default: 0

ReferenceLoss

Loss at reference range

Specify the loss at a given reference range as a scalar. Units are in dB.

Default: 0

Methods

cloneCreate time varying gain 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
stepApply time varying gains to input signal

Examples

Apply time varying gain to a signal to compensate for signal power loss due to range.

rngloss = 10:22; refloss = 16; % in dB
t = (1:length(rngloss))';
x = 1./db2mag(rngloss(:));
H = phased.TimeVaryingGain('RangeLoss',rngloss,...
    'ReferenceLoss',refloss);
y = step(H,x);

% Plot signals
tref = find(rngloss==refloss);
stem([t t],[abs(x) abs(y)]);
hold on;
stem(tref,x(tref),'filled','r');
xlabel('Time (s)'); ylabel('Magnitude (V)');
grid on;
legend('Before time varying gain',...
    'After time varying gain',...
    'Reference range');

References

[1] Edde, B. Radar: Principles, Technology, Applications. Englewood Cliffs, NJ: Prentice Hall, 1993.

[2] Skolnik, M. Introduction to Radar Systems, 3rd Ed. New York: McGraw-Hill, 2001.

Introduced in R2012a

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