signal_interface Class Reference

Signal description class. More...

Public Member Functions
function	signal_interface (in signal, in param)
	Class constructor. More...
function	fun1 (in obj, in fun)
	Apply a function to each signal component separately. More...
function	params (in obj)
	Returns signal parameters in a struct. More...
function	L (in obj)
	Retrieve the length of the signal.
function	N (in obj)
	Retrieve the number of signal components.
function	mtimes (in obj, in M)
	Jones matrix multiplication (overloads * operator)
function	Nss (in obj)
	Retrieve the number of samples per symbol.
function	Ts (in obj)
	Retrieve the sample period.
function	Tb (in obj)
	Retrieve the symbol period.
function	setPtot (in obj)
	Set total power from power per column.
function	end (in obj, in k, in n)
	Overload of indexing end statement. More...
function	subsref (in obj, in s)
	Overload indexing access for read the field. More...
function	get (in obj)
	Retrieve the signal.
function	getRaw (in obj)
	Retrieve raw waveform. Use with caution.
function	getScaled (in obj)
	Retrieve the signal with appropriate power scaling. More...
function	getNormalized (in obj)
	Retrieve the signal normalized to unity power. More...
function	normalize (in obj)
	Normalize stored signal to unity mean power. More...
function	plus (in obj1, in obj2)
	Add two signals (coherently)
function	truncate (in obj, in L)
	Truncate signal length.
function	combine (in varargin)
	Combine multiple signals. More...
function	disp (in obj)
	Overload display function.
function	set (in obj, in varargin)
	Set properties for the current object. More...

Protected Attributes
Property	Fc
	Carrier frequency (Hz)
Property	Fs
	Sampling rate (S/sec)
Property	Rs
	Symbol rate (Baud)
Property	P
	Total signal power (pwr object)
Property	PCol
	Signal power per column (array of pwr objects)
Property	E
	Complex baseband LxN (L = length, N = number of components)

Static Private Member Functions
static function	enforceLhs (in n, in minimum)

Detailed Description

Signal description class.

signal_interface contains main signal attributes: waveform, carrier frequency, sampling rate, symbol rate, and power. Only objects of type signal_interface can be passed between units.

The waveform can contain multiple components/columns - the idea being that a polarization multiplexed signal, e.g. could have 2 components/columns, one for each state of polarization. For multimode fiber, the definition would be analogous, there would just be more columns.

A number of operations are overwritten for signal_interface objects so that they can be treated like arrays containing waveforms (e.g. sig1+sig2 produces a result that makes sense). See methods for details.

Conventions

• A signal_interface with Rs = 1 is analog
• A signal_interface with Fs = 1 is logical
• A signal_interface with Fc = 0 is electrical or logical

Power scaling Note that both the waveform and the object's power property contain information about the waveform's amplitude. Generally, when these conflict, the information in the power property takes precedence.

Power can be specified either as a per-column/mode quantity or for the whole signal. When these conflict, the per-column specification takes precedence.

On construction, if power is not specified, it is calculated automatically from the waveform for each column separately. If total power but not per-column power is specified, the splitting fraction is calculated numerically from the waveform.

See also

pwr, getPColFromNumeric_v1

Example

s1= rand(10,1);
sigparams.Fs = 10e9;
sigparams.Fc = 0;
sigparams.Rs = 1e9;
sigparams.P = pwr(20, 3);
signal1 = signal_interface(s1,sigparams)

will create a signal with random values, sampling rate 10G, no carrier frequency, symbol rate (nominal) 1G, and 3dBm power and 20 dB SNR (nominal). See also run_TestSignalInterface.m, run_TestSignalInterfaceAdvanced.m

Author

Robert Borkowski

Version

2

Definition at line 58 of file signal_interface.m.

Constructor & Destructor Documentation

function signal_interface::signal_interface	(	in	signal,
		in	param
	)

Class constructor.

Constructs an object of type signal_interface. Example:

signal1 = signal_interface(s1,param)

s1 is the waveform. Each column corresponds to a signal component - i.e. a polarization multiplexed signal would be an Lx2 array param is the signal parameters. For Fc, Fs, and Rs, there is a direct mapping to signal properties. Power can be specified either as total signal power or power per column (this will take precedence if both are specified). In case power is not specified, a warning will be displayed, and the total signal power will be calculated from the waveform.

Member Function Documentation

function signal_interface::combine

(

in

varargin

)

Combine multiple signals.

Like concatenation, but for signal_interface objects. All signal parameters must match (Rs, Fs, etc.) to avoid an error.

Example:

sig_big = combine(si1, si2, si3, si4);

See also

Combiner_v1::combine

function signal_interface::end	(	in	obj,
		in	k,
		in	n
	)

Overload of indexing end statement.

Parameters

k	Current dimension index
n	Total number of dimensions

function signal_interface::fun1	(	in	obj,
		in	fun
	)

Apply a function to each signal component separately.

This allows the user to avoid for loops and/or repmat if the same operation is being performed on all modes independently.

It should run faster than an implementation based on for loops/repmat, occupy fewer lines of code, and take less memory. It also automatically tracks changes in power, which can be useful for, e.g. filtering operations.

Examples

% apply a frequency shift
t = genTimeAxisSig(input);
frequency = 100e6;

shiftedSignal = fun1(signal, @(x)x.*exp(1i*2*pi*frequency*t));

Or for more complicated functions where top-down programming is required:

function out = traverse(obj, in)

out = fun1(in, @(x)obj.complicatedMethod(x));

end

function Eout = complicatedMethod(obj, Ein)

%Here we put some code that acts on column vectors:
Eout = Ein.*conj(Ein);
Eout = filter(Eout, obj.B, obj.A);
%etc

end

See also Matlab's bsxfun and arrayfun for examples

function signal_interface::getNormalized

(

in

obj

)

Retrieve the signal normalized to unity power.

Normalize then return signal

function signal_interface::getScaled

(

in

obj

)

Retrieve the signal with appropriate power scaling.

Retrieve the signal with appropriate power scaling. Scaling is applied based on the per-column signal power

function signal_interface::normalize

(

in

obj

)

Normalize stored signal to unity mean power.

Normalize the stored signal to unity power. Normalization is based on the total signal power (same scaling is applied to all signal components) Since we mostly use this for DSP, stored power is changed to track new value so that get returns desired, normalized field.

function signal_interface::params

(

in

obj

)

Returns signal parameters in a struct.

This allows easily use and manipulate the parameters to construct a signal_interface derived from the existing one.

Return values

p	Structure containing the signal necessary parameters

function signal_interface::set	(	in	obj,
		in	varargin
	)

Set properties for the current object.

Examples:

signal = set(signal, ones(100, 1);
signal.set(ones(100, 1);
signal = set(signal, 'P', pwr(50, 1));
signal = set(signal, 'E', ones(100, 1), 'P', pwr(50, 1), 'Rs', 50e9);

The first two lines are equivalent, and just show the different main syntax that can be used. They will set the signal to 100 1's without changing other properties. The next two lines are examples of how to change multiple properties at once.

Note on power specfication: If both P and PCol are set, values in PCol take precedence.

Return values

obj	signal_interface with changed properties

function signal_interface::subsref	(	in	obj,
		in	s
	)

Overload indexing access for read the field.

Allows to access the internal field with the the standard MATLAB indexing system.

Example

s1= rand(10,2);
signal1 = signal_interface(s1,struct('Fs',10e9,'Fc',0,'Rs',1e9,'P',pwr(20,3)))
signal1(1:10,1)

If sig is a signal_interface you can access the field as sig(:,1)

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The documentation for this class was generated from the following file:

• base/signal_interface.m