commsrc.pattern

Construct pattern generator object

Description

example

h = commsrc.pattern constructs a pattern generator object, h.

The pattern generator object produces modulated data patterns. The object can be used to inject jitter into modulated signals.

h = commsrc.pattern(Name,Value) creates a combined jitter generator object with the 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

A pattern generator object includes these properties. You can edit all properties, except those explicitly noted.

PropertyDescription
TypeType of pattern generator object ('Pattern Generator'). This property is not writable.
SamplingFrequency

Sampling frequency of the input signal in hertz.

SymbolRateThe symbol rate of the input signal. This property depends upon the SamplingFequency and SamplesPerSymbol properties. This property is not writable.
SamplesPerSymbol

The number of samples representing a symbol. SamplesPerSymbol must be an integer. This property affects SymbolRate.

PulseType

The type of pulse the object generates. Pulse types available: return-to-zero ('RZ') and non-return-to-zero ('NRZ'). The initial condition for an 'NRZ' pulse is 0.

OutputLevels

Amplitude levels that correspond to the symbol indices. For an 'NRZ' pulse, specify as a 1-by-2 vector. The first element of the 1-by-2 vector corresponds to the 0th symbol (data bit value 0). The second element corresponds to the 1st symbol (data bit value 1). For an 'RZ' pulse, specify as a scalar and the value corresponds to the data bit value 1.

DutyCycle

The duty cycle of the pulse the object generates. Displays calculated duty cycle based on pulse parameters. This property is not writable.

RiseTime

Specifies 10% to 90% rise time of the pulse in seconds.

PulseDuration

Pulse duration in seconds defined by IEEE STD 181 standard. See the Return-to-Zero (RZ) Signal Conversion: Ideal Pulse to STD–181 figure in the Object Functions. Applies when PulseType is 'RZ'.

FallTime

Fall time of the pulse in seconds, specified as a percentage from 10 to 90.

DataPattern

The bit sequence the object uses, specified as 'PRBS5', 'PRBS6', …, 'PRBS15', 'PRBS23', 'PRBS31', and'User Defined'.

UserDataPattern

User-defined bit pattern consisting of a vector of ones and zeroes. Applies when DataPattern is 'User Defined'.

Jitter

Jitter characteristics, specified as a commsrc.combinedjitter object. Use this property to configure Random, Periodic and Dual Dirac Jitter.

Object Functions

A pattern generator object has five object functions, as described in this section.

generate

This object function outputs a frame worth of modulated and interpolated symbols. It has one input argument, which is the number of symbols in a frame. Its output is a column vector. You can call the object function using this syntax:

x = generate(h, N)
where h is the handle to the object, N is the number of output symbols, and x is a column vector whose length is N multiplied by h.SamplesPerSymbol.

reset

This object function resets the pattern generator to its default state. The property values do not reset unless they relate to the state of the object. This object function has no input arguments.

idealtostd181

This object function converts the ideal pulse specifications to IEEE STD-181 specifications. The ideal 0% to 100% span rise time (tr) and fall time (tf) are converted to 10% to 90% spans with a 50% pulse width duration (pw). Call the idealtostd181 object function using this syntax:

h = idealtostd181(tr,tf,pw)

The object function sets the appropriate properties. The IEEE STD-181 Return-to-Zero (RZ) signal parameters are shown in this figure.

std181toideal

The std181toideal object function converts the IEEE STD-181 pulse specifications, stored in the pattern generator, to ideal pulse specifications. The function converts the rise and fall times from 10% – 90% span to 0% – 100% span, and converts the 50% pulse duration to pulse width. Call the std181toideal object function using this syntax:

[tr tf pw] = std181toideal(h)
where h is the pattern generator object handle, tr is the ideal 0% – 100% rise time, tf is the ideal 0% – 100% fall time, and pw is the ideal pulse width. The ideal pulse non-return-to-zero (NRZ) signal parameters are shown in this figure.

Use the property values for IEEE STD-181 specifications.

computedcd

The computedcd object function computes the duty cycle distortion, DCD, of the pulse defined by the pattern generator object h.

DCD represents the ratio of the pulse on duration to the pulse off duration. For an NRZ pulse, on duration is the duration the pulse spends above the symbol boundary level. Off duration is the duration the pulse spends below zero. Call the computedcd object function using this syntax:

dcd = computedcd(h)

The software calculates DCD given tR, tF, Tsym. This formula assumes that the symbol boundary level is zero.

Th = (Ah-Al) * tRAl + (Ah-Al) * tFAl + PW+

Tl = (Ah-Al) *tRAl + (Ah-Al) *tFAl + PW-

DCD = ThTl

Where Th is the duration of the high signal, Tl is the duration of the low signal, and DCD represents the ratio of the duration of the high signal to the low signal.

Examples

collapse all

Create a commsrc.pattern object. Display the default object property values.

h = commsrc.pattern;
disp(h)
                 Type: 'Pattern Generator'
    SamplingFrequency: 10000
     SamplesPerSymbol: 100
           SymbolRate: 100
            PulseType: 'NRZ'
         OutputLevels: [-1 1]
             RiseTime: 0
             FallTime: 0
          DataPattern: 'PRBS7'
               Jitter: [1x1 commsrc.combinedjitter]

Generate a binary non-return-to-zero (NRZ) signal utilizing the pattern generator object. View the NRZ signal with and without jitter applied to the signal.

Initialize system parameters.

Fs = 10000;            % Sample rate
Rs = 50;               % Symbol rate (Sps)
sps = Fs/Rs;           % Number of samples per symbol
Trise = 1/(5*Rs);      % Rise time of the NRZ signal
Tfall = 1/(5*Rs);      % Fall time of the NRZ signal
frameLen = 100;        % Number of symbols in a frame
spt = 200;               % Number of samples per trace on eye diagram

Create a pattern generator object with no jitter component assigned.

src = commsrc.pattern('SamplingFrequency', Fs, ...
                      'SamplesPerSymbol', sps, ...
                      'RiseTime', Trise, ...
                      'FallTime', Tfall)
src = 
                 Type: 'Pattern Generator'
    SamplingFrequency: 10000
     SamplesPerSymbol: 200
           SymbolRate: 50
            PulseType: 'NRZ'
         OutputLevels: [-1 1]
             RiseTime: 0.0040
             FallTime: 0.0040
          DataPattern: 'PRBS7'
               Jitter: [1x1 commsrc.combinedjitter]

src.Jitter
ans = 
                 Type: 'Combined Jitter Generator'
    SamplingFrequency: 10000
         RandomJitter: 'off'
       PeriodicJitter: 'off'
          DiracJitter: 'off'

Generate an NRZ signal and view the eye diagram of the signal.

message = generate(src,frameLen);
eyediagram(message,spt)

Add inter-symbol-interference (ISI) to an NRZ signal. ISI is modeled by two equal amplitude Dirac functions. Create a combined jitter object with Dirac jitter and assign it to the pattern generator object.

jitterSrc = commsrc.combinedjitter('DiracJitter','on', ...
    'DiracDelta',0.05/Rs*[-1 1]);
src.Jitter = jitterSrc
src = 
                 Type: 'Pattern Generator'
    SamplingFrequency: 10000
     SamplesPerSymbol: 200
           SymbolRate: 50
            PulseType: 'NRZ'
         OutputLevels: [-1 1]
             RiseTime: 0.0040
             FallTime: 0.0040
          DataPattern: 'PRBS7'
               Jitter: [1x1 commsrc.combinedjitter]

Generate an NRZ signal that has jitter added to it and view the eye diagram of the signal.

reset(src);
message = generate(src, frameLen);
eyediagram(message,spt)

References

[1] IEEE Standard for Transitions, Pulses, and Related Waveforms, STD-181-2011. Piscataway, NJ. 6 September 2011.

Introduced in R2008b