EngeeDSP.gpsWaveformGenerator

GPS signal generator (traditional L1 and L2, upgraded L1C, L2C and L5).

Library	`EngeeDSP`
Block	GPS Waveform Generator

Description

An object EngeeDSP.gpsWaveformGenerator creates a Global Positioning System (GPS) signal generator that supports the following GPS signals:

Traditional L1 and L2 — used when for the property SignalType value specified "legacy".
Upgraded L1C — used when for the property SignalType value specified "l1c".
Upgraded L2C — used when for the property SignalType value specified "l2c".
Upgraded L5 — used when for the property SignalType value specified "l5".

To create a GPS signal generator object, follow these steps:

Create an object EngeeDSP.gpsWaveformGenerator and set its properties.
Call the object with arguments as if it were a function.

To learn more about how to work with system objects, see Engee System Objects.

Syntax

Creation

gpsWaveObj = gpsWaveformGenerator() — creates a system object EngeeDSP.gpsWaveformGenerator with default properties.
gpsWaveObj = gpsWaveformGenerator("Name",value) — creates a system object EngeeDSP.gpsWaveformGenerator with the specified property "Name", set to the specified value Value. You can specify additional arguments as a name-value pair in any order ("Name1", Value1,…,"NameN", ValueN).

Using

waveform = gpsWaveObj(navdata) — Generates a GPS signal in the time domain.
```
waveform = gpsWaveObj(navdata)
```
waveform = gpsWaveObj(LNAV, CNAV) — Generates a GPS signal in the time domain.
```
waveform = gpsWaveObj(LNAV, CNAV)
```

Arguments

Input arguments

navdata — navigation data

+ the binary matrix

Details

Navigation data set as a binary matrix — the number of columns must be equal to the length of the property PRNID, since each column corresponds to PRNID. The number of rows represents the number of bits of navigation data.

Dependencies

To use this argument, set the property to SignalType value "legacy", "l1c" or "l5".

Типы данных

AbstractMatrix{Integer}

LNAV — bits of the traditional navigation message

+ the binary matrix

Details

Bits of a traditional navigation message, specified as a binary matrix.

If for the property SignalType value set "l2c" if one input argument is given, then gpsWaveObj assigns the same value to LNAV and CNAV.

Dependencies

To use this argument, set the property to SignalType value "l2c".

Типы данных

AbstractMatrix{Integer}

CNAV — civil navigation message bits

+ the binary matrix

Details

The bits of the civil navigation message are set as a binary matrix, of the same dimension as LNAV

If for the property SignalType value set "l2c" if one input argument is given, then gpsWaveObj assigns the same value to LNAV and CNAV.

Dependencies

To use this argument, set the property to SignalType value "l2c".

Типы данных

AbstractMatrix{Integer}

Output arguments

waveform — generated GPS signal

+ the matrix

Details

Each column represents a signal corresponding to the value of the property PRNID.

The number of lines is equal to the product BitDuration × SampleRate × numBits, where numBits is the number of input bits and is equal to size(navdata,1).

The sampling frequency of the signal corresponds to the value specified in the property SampleRate.

Типы данных

AbstractArray{Real}, AbstractArray{ComplexF64}

Features

# SignalType — the type of baseband signal generated

+ "legacy" (by default) | "l1c" | "l2c" | "l5"

Details

The type of baseband signal generated, set as:

"legacy" — Use this value to generate a traditional L1 or L2 signal.
"l1c" — use this value to generate an upgraded L1 signal.
"l2c" — Use this value to generate an upgraded L2 signal.
"l5" — Use this value to generate an upgraded L5 signal.

# PRNID is the index of the pseudorandom satellite code

+ 1 (by default) | an integer in the range [1, 210] | a vector of integers in the range [1, 210]

Details

The satellite Pseudorandom code Index (PRN) of the satellite, set as:

An integer in the range [1, 210] — Use this value to enter the PRN index for an individual satellite.
A vector of integers in the range [1, 210] — Use this value to enter PRN indexes for multiple satellites.

If for the property SignalType value set "l2c", then the PRN indexes should be in the range [1, 63] or [159, 210].

# IsL2CInPhaseQuadrature — enabling quadrature sealing for L2C and L2P

+ true or 1 (by default) | false or 0

Details

A property for enabling phase quadrature for L2C and L2P, set as a numeric or logical value:

true — use this option to set the precision code (P-code) for the in-phase branch (I-branch), as well as the civil code of medium duration (CM) and the civil long code (CL) for the quadrature branch (Q-branch);
false — use this option to install all the codes in the I-branch.

Dependencies

To use this property, set the property to SignalType value "l2c".

# EnablePCode — P-code indicator

+ true or 1 (default) | false or 0

Details

The P-code indicator, set as a numeric or logical value.

In cases where the P-code is not needed, set this property to false to increase the execution speed.

If the value is set to false, The P-code in the I-branch is set to 0.

Dependencies

To use this property, set the property to SignalType value "legacy" or "l2c".

# HasDataWithPCode — the ability to transfer data using a P-code

+ true or 1 (by default) | false or 0

Details

The ability to transmit data using a P-code, specified as a numeric or logical value. If the value is set to true, then the data is transmitted along with the P-code.

Dependencies

To use this property, set the property to SignalType value "legacy" or "l2c", and for the [Argument property:EnablePCode] value true.

# HasDataWithCACode — the ability to transfer data with a coarse capture code (C/A code)

+ true or 1 (default) | false or 0

Details

The ability to transmit data with a coarse capture code (C/A code), set as a numeric or logical value. If the value is set to true, then the data is transmitted along with the C/A code.

Dependencies

To use this property, set the property to SignalType value "legacy".

# InitialTime — the starting time for one week, from

+ 0 (by default) | a real scalar in the range [1, 604800]

Details

The initial time for one week in seconds, set as a real scalar in the range [0, 604800].

Dependencies

To use this property, set the property to SignalType value "legacy", and for the [Argument property:EnablePCode] value false.

# SampleRate is the sampling frequency of the signal, Hz

+ 10.23e6 (by default) | the scalar is greater than 1e6

Details

The sampling frequency of the signal in Hz, set as a scalar, is greater than 1e6. This property determines the sampling frequency of the signal.

# BitDuration — duration of input bits

+ "0.01" | "0.02"

Details

This property is read-only. The duration of the input bits, represented as one of these values:

"0.01" — if the property SignalType has a value "l1c" or "l5".
"0.02" — if the property SignalType has a value "legacy" or "l2c".

# ChipRate — processing speed of the slowest code in the signal

+ "1.023e6" | "511.5e3" | "10.23e6"

Details

This property is read-only. The processing speed of the slowest code in the signal, represented as one of these values:

"1.023e6" — if the property SignalType has a value "legacy" or "l1c".
"511.5e3" — if the property SignalType has a value "l2c".
"10.23e6" — if the property SignalType has a value "l5".

Methods

Common to all system objects

`step!`	Run the system object operation algorithm
`release!`	Allow changing the value of a system object property
`reset!`	Resetting the internal states of a system object

Examples

Generating a traditional GPS signal

Details

We will generate random fragments of navigation data.

using EngeeDSP, EngeeSatellites

navdata = rand(0:1, 2, 1)

Creating an object EngeeDSP.gpsWaveformGenerator and set its properties.

gpswaveobj = gpsWaveformGenerator()
gpswaveobj.EnablePCode = true
gpswaveobj.SampleRate = 4*10.23e6

Let’s generate a traditional GPS signal and plot its spectrum.

waveform = gpswaveobj(navdata)
txscope = spectrumAnalyzer(SampleRate=gpswaveobj.SampleRate)
txscope(waveform)

gpswaveformgenerator 1

GPS L1C signal generation

Details

Let’s set the PRN indexes and generate random bits of navigation data.

prn = [4 70]
numsat = length(prn)
numbits = 100
msg = rand(0:1, numbits, numsat)

Creating an object EngeeDSP.gpsWaveformGenerator and set its properties.

fs = 25e6
gpswaveobj = gpsWaveformGenerator(
    "SignalType","l1c",
    "PRNID",prn,
    "SampleRate",fs
)

Let’s generate the GPS L1C signal and plot its spectrum.

waveform = gpswaveobj(msg)
txscope = spectrumAnalyzer(SampleRate=fs)
txscope(waveform)

gpswaveformgenerator 2

GPS L2C signal generation

Details

We will generate an L2C GPS signal with random LNAV and CNAV data for four GPS satellites.

Let’s set the PRN indexes and generate random LNAV and CNAV data.

prn = [7 11 20 28]
numsat = length(prn)
numbits = 10
lnavdata = rand(0:1, numbits, numsat)
cnavdata = rand(0:1, numbits, numsat)

Creating an object EngeeDSP.gpsWaveformGenerator and set its properties.

gpswaveobj = gpsWaveformGenerator()
gpswaveobj.SignalType = "l2c"
gpswaveobj.PRNID = prn
gpswaveobj.SampleRate = 15e6
gpswaveobj.EnablePCode = true

Let’s generate a GPS L2C signal and plot its spectrum.

waveform = gpswaveobj([lnavdata, cnavdata])
txscope = spectrumAnalyzer()
txscope(waveform)

gpswaveformgenerator 3

GPS L5 signal generation

Details

Let’s set the PRN indexes and generate random navigation data.

prn = [185, 189]
numsat = length(prn)
numbits = 40
msg = rand(0:1, numbits, numsat)

Creating an object EngeeDSP.gpsWaveformGenerator and set its properties.

fs = 25e6
gpswaveobj = gpsWaveformGenerator(
    "SignalType", "l5",
    "PRNID", prn,
    "InitialTime", 42123,
    "SampleRate", fs
)

Let’s generate a GPS L2C signal and plot its spectrum.

waveform = gpswaveobj(msg)
txscope = spectrumAnalyzer(SampleRate=fs)
txscope(waveform)

gpswaveformgenerator 4