Glossary

Acquisition is the initial process of detecting the presence of satellite signals and determining their approximate code phase and Doppler frequency.

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The first step in a digital RF system is to convert analog  RF signals into digital form using ADCs. This process allows for precise  sampling and quantization of the RF signal, preserving its information in a  digital format.

An analog  front-end is a circuit system that prepares analog signals from sensors for  digital processing. It typically involves amplification, filtering, and other  signal conditioning to improve signal quality and precision before the signal  is converted to a digital format by an Analog-to-Digital Converter (ADC).

A set of data that provides a broad overview  of the orbits of all satellites in a constellation, allowing a receiver to  quickly find and identify satellites. The Almanac is less precise than the  ephemeris data.

A family of  computer architectures that are all based on a reduced set of instructions.  The abbreviation is a trademark of the ARM holding, who hold the intellectual  property and license them out to other companies.

One of the 6 main GNSS constallations, owned  by China. It's also a translation of big dipper, a reference to the  constellation of Ursa Major.

For GNSS systems, the bit phase refers tothe specific state (0 or 1) of a data  bit within the navigation message, which is modulated onto the carrier  signal.Accurate bit phase detection is crucial for a GNSS receiver to decode the navigation data, which is essential for calculating position, velocity, and time.

The list of all components needed for  assembly of product or a module.

A less precise  mode of GPS used for civilian positioning. A more precise mode called P-mode  exists for military navigation.

A full search in frequency and phase of the entire search space. A complete search isn't always needed, once a peak has bean found it is possible to exit early.

The set of satellites that make up a particular system. GPS, GLONASS, Galileo, BeiDou, NAViC, and QZSS are all  considered independent constellations.

Providing a rough position fix using inaccurate time information. This can happen when tracking sufficiently weak GNSS signals.

• dBHz is a unit used to express the spectral power density or power spectral density (PSD) of a signal per unit bandwidth (Hertz).
• It is commonly used in the context of noise power spectral density (NPSD) or signal-to-noise ratio (SNR) calculations.
• dBHz expresses the power level of a signal per Hertz of bandwidth.
• It is often used in RF and communication systems to characterize the noise floor or noise density in a particular bandwidth.

• dBm is a unit used to measure power levels relative to 1 milliwatt (mW).
• It is commonly used to express the power level of signals in various telecommunication systems, such as radio frequency (RF) signals, optical signals, or electrical signals.

• dBV is a unit of voltage level expressed in decibels relative to 1 volt (V).
• While less common than dBm, dBV can be used to describe the voltage level of the signal in a GNSS system. This is more relevant when dealing with the signal in terms of voltage levels within the receiver circuitry.

Digital RF refers to the application of digital techniques in RF systems, where traditional analog radio signals are processed and manipulated using digital signal processing (DSP) techniques. In digital RF systems, analog RF signals are converted into digital form early in the signal chain, enabling various advanced processing techniques to be applied before conversion back to analog if needed.

Key aspects of Digital RF:

• Analog-to-Digital Conversion (ADC): The first step in a digital RF system is to convert analog RF signals into digital form using ADCs. This process allows for precise sampling and quantization of the RF signal, preserving its information in a digital format.
• Digital Signal Processing (DSP): Once the RF signal is digitized, it can be processed using various digital signal processing techniques. This includes filtering, modulation/demodulation, equalization, error correction, and other signal processing operations. Digital processing offers more flexibility and accuracy compared to traditional analog methods.
• Software-Defined Radio (SDR): Digital RF is often associated with software-defined radio (SDR) technology, where the functionality of RF systems is implemented primarily in software running on general-purpose digital signal processors (DSPs), field-programmable gate arrays (FPGAs), or software-defined radio platforms. SDR allows for reconfigurable and flexible radio systems that can adapt to different communication standards and requirements.

The opposite of  ADC converting a signal from its digital form to an RF signal. Normally the  last step before analog transmission.

Doppler shift refers to the change in frequency of any signal when either the transmitter, the receiver or both are moving. This is  what causes the tone of a passing ambulance to change. This phenomenon is a key observable in  GNSS, providing valuable information about the relative velocity and position of the receiver and satellite.

The set of digital signal processing techniques. This includes filtering,  modulation/demodulation, equalization, error correction, and other signal processing operations. Digital processing offers more flexibility and accuracy compared to traditional analog methods.

An ephemeris ia a table or data file giving the calculated positions of a celestial object at regular intervals throughout a period. Ephemerides are critical for GNSS operations as they provide precise information about satellite positions and timing, enabling accurate positioning and navigation for a wide range of applications:

• Satellite Positioning: GNSS systems work by determining the receiver's position on Earth using signals transmitted from satellites. To accurately calculate the position, the receiver needs to know the precise positions of the satellites at a given time. Ephemerides provide this information.
• Signal Timing: GNSS signals travel at the speed of light, so precise timing is crucial for accurate positioning. Ephemerides not only provide the satellite positions but also include information about the satellite's internal clock corrections. This ensures that receivers can accurately calculate signal travel times and, consequently, their own positions.
• Navigation Accuracy: GNSS receivers use complex algorithms to compute their positions based on signals received from multiple satellites. Accurate ephemerides are essential inputs for these calculations. Errors in ephemerides can lead to inaccuracies in positioning, affecting various applications such as navigation, surveying, and timing.
• Dynamic Nature of Satellites: Satellites in GNSS constellations are constantly in motion due to Earth's gravitational forces and other factors. Therefore, ephemerides need to be regularly updated to reflect these changes accurately. GNSS users rely on up-to-date ephemerides to ensure the accuracy of their position calculations.

In GNSS (Global Navigation Satellite System) receivers, the terms "early," "late," and "prompt"refer to the correlation of the received signal with locally generated replica signals. These are key components in the signal processing that enables accurate positioning and timing.

The European SBAS for Galileo. See SBAS.

An overview of the most asked questions and their answers.

A technique used in navigation systems, particularly those relying on Global Navigation Satellite Systems (GNSS) like GPS, to ensure the integrity of the positioning data.

A  type of integrated  circuit that can be configured by a customer or designer after manufacturing, allowing for customization of the hardware to meet specific needs. This  reconfigurability makes them versatile for various applications.

• GNSS is a generic term that encompasses multiple satellite navigation systems developed by various countries and organizations.
• Examples of GNSS include GPS (USA), GLONASS (Russia), Galileo (European Union), BeiDou (China), and NavIC (India).
• GNSS receivers are capable of receiving signals from multiple satellite constellations, which can improve accuracy, availability, and reliability of positioning data, especially in challenging environments where signals from one system may be obstructed or weak.
• GNSS receivers can use signals from any compatible satellite constellation to determine position, velocity, and time.

• GPS is a specific satellite navigation system developed and maintained by the United States government.
• It was the first fully operational global navigation satellite system.
• GPS satellites transmit signals in L-band frequencies, which are received by GPS receivers to determine the receiver's location, velocity, and time.
• Originally developed for military purposes, GPS is now widely used in civilian applications like navigation, surveying, mapping, and timing.

The Indian SBAS for NAVIC. See SBAS

The time difference between the time scales used by GPS and Galileo. This offset needs to be  accounted for when using signals from both systems to calculate a precise position

A Russian acronym for Gobal Navigation Satellite System, a Russian owned constellation.

The set of programmable pins on a microcontroller or other  integrated circuits that can be configured as either input or output for  digital signals, allowing interaction with other components.

The process  where a GNSS receiver switches from using a coarse acquisition code to a more  precise code for more refined positioning calculations.

A two-wire serial communication protocol primarily used for  short-distance communication between electronic devices, particularly on  printed circuit boards. It's a simple, synchronous, and half-duplex protocol,  meaning it uses a clock signal and can only transmit in one direction at a  time.

The Internet of  Things refers to the network of physical objects or "things"  embedded with sensors, software, and other technologies that enable them to  connect and exchange data with other devices and systems over the internet.

See NAViC

K-band frequencies are used in a variety of applications, including radar systems (such as police radar, automatic door openers, and automotive radar), satellite communication systems (for high-data-rate communication links), and some types of microwave ovens.

• K-band radar systems are often employed in speed enforcement, collision avoidance systems, and short-range imaging applications due to their relatively high frequency, which allows for finer resolution and greater precision compared to lower frequency bands.
• Frequency Range: K-band typically refers to the frequency range of approximately 18 to 27 gigahertz (GHz), or 18,000 to 27,000 megahertz (MHz).

A mathematical  algorithm that uses a series of noisy measurements over time to estimate the  state of a dynamic system,with the goal of minimizing the mean squared error  of the estimates so as to provide the best possible results.

The "L-band" refers to a range of radio frequencies within the electromagnetic spectrum. This range encompasses wavelengths longer than those used for microwave frequencies but shorter than those used for shortwave radio frequencies.

• In the context of satellite communication and navigation systems, the L-band is utilized for transmitting signals from satellites to ground-based receivers. These signals carry information such as timing, positioning, and navigation data, which are decoded by the receivers to determine the user's location, velocity, and time.
• Frequency Range: L-band typically refers to the frequency range of approximately 1 to 2 gigahertz (GHz), or 1,000 to 2,000 megahertz (MHz).

L-band frequencies are part of the electromagnetic spectrum, typically ranging from 1 to 2 gigahertz (GHz). In satellite navigation systems like GPS and GNSS, L-band frequencies are used to transmit signals from satellites to receivers on Earth. There are several L-band frequencies used for satellite navigation purposes:

• GPS (Global Positioning System): GPS satellites transmit signals on two L-band frequencies: L1 (~1575.42 MHz) and L2 (~1227.60 MHz). In addition, there is a third frequency, L5 (~1176.45 MHz), which is used for civilian purposes in modernized GPS systems.
• GLONASS (Global Navigation Satellite System): GLONASS satellites transmit signals on two primary L-band frequencies: GLONASS L1 (~1602.0 MHz) and GLONASS L2 (~1246.0 MHz).
• Galileo: Galileo satellites transmit signals on three L-band frequencies: E1 (~1575.42 MHz), E5a (~1176.45 MHz), and E5b (~1207.14 MHz).
• BeiDou (BDS): BeiDou satellites transmit signals on two L-band frequencies: B1 (~1561.098 MHz) and B2 (~1207.14 MHz).
• NavIC (Navigation with Indian Constellation): NavIC, developed by the Indian Space Research Organisation (ISRO), transmits signals on two L-band frequencies: L5 (~1176.45 MHz) and S-band (~2492.028 MHz), which is close to L-band.

A type of voltage regulator designed to operate with a very  small voltage difference between its input and output. The voltage difference  is called the dropout.

A type of  electronic amplifier designed to amplify weak radio frequency (RF) signals  while minimizing the addition of noise to the signal.

A technology used in electronics to transmit high-speed  digital signals over short distances like in displays or automotive electronics.

The Japanese SBAS for QZSS. See SBAS

milliWatt

Navigation with  Indian Constellation

A form of memory that retains the stored data even when unpowered.

An original design manufacturer is a company that designs and manufactures products, often based on a client's general specifications, and then sells them under the client's brand name. Essentially, the ODM provides both the design and  the manufacturing service.

Similar to an ODM, but only provides the manufacturing service and no design services. Products are still sold under the client's brand name.

A feature of the Galileo satellite navigation system designed to authenticate the navigation data sent to users, ensuring it originates from genuine Galileo satellites and hasn't been tampered with. This helps protect against spoofing attacks, where malicious actors transmit fake satellite signals to mislead receivers.

A fundamental component in electronic devices, acting as the foundation for mounting and connecting electronic components. PCBs provide both physical support and electrical connections for these components.

A method used in satelitte navigation that calculates very precise positions, with errors  as small as a few centimeters under good conditions.

A specific type of code used in satellite navigation  systems. Each GNSS satellite transmits a unique PRN code, which allows a  receiver to identify the satellite and measure the distance to it. A PRN code is a sequence of seemingly random binary digits (0s and 1s) that is used  to modulate the GNSS signal. While it appears random, it's actually generated  by a deterministic algorithm, meaning it can be precisely reproduced by both  the satellite and the receiver.

In GNSS (Global  Navigation Satellite System) positioning, a pseudorange is an approximate  distance measurement between a satellite and a receiver, calculated by multiplying the time it takes for a signal to travel from the satellite to the receiver by the speed of light. It's called "pseudo" because it's not a true, error-free range, as it's affected by various factors like atmospheric delays and receiver clock errors.

The core output of a Global Navigation Satellite System  receiver. It's the process where the receiver calculates its location, speed,  and precise time based on signals received from GNSS satellites. This information is crucial for various applications, from navigation in cars to  tracking movements in scientific research.

A type of surface-mount semiconductor package, characterized by its flat, leadless design with conductive pads on the bottom surface instead of protruding leads. QFNs are used to connect integrated circuits to printed circuit  boards.

QZSS is a satellite-based augmentation system (SBAS) developed by the Japanese government to provide precise positioning services  over Japan and the surrounding region. QZSS is designed to complement and enhance the existing global navigation satellite systems (GNSS) such as GPS.

Radio Frequency

A technique that enhances the accuracy of a GNSS system by including real-time corrections from nearby reference stations with a known  position. This offers fast convergence and centimeter-level accuracy.

Satellite bands refer to the frequency ranges within the electromagnetic spectrum that are allocated for satellite communication, navigation, remote sensing, and other satellite-based applications. There are several satellite bands commonly used for these purposes, including:

• L-band: typically range from approximately 1 to 2 gigahertz (GHz), L-band frequencies are commonly used in satellite communication and navigation systems like GPS, GLONASS, Galileo, and others.
• S-band: typically range from 2 to 4 gigahertz (GHz). They are used in various satellite communication systems, weather monitoring satellites, and radar applications.
• C-band: typically range from 4 to 8 gigahertz (GHz), C-band frequencies are extensively used for satellite communication, including television broadcasting, maritime and aeronautical communication, and fixed satellite services.
• X-band: typically range from 8 to 12 gigahertz (GHz). They are commonly used in satellite communication for high-data-rate links, military applications, radar systems (such as weather radar and ground-based surveillance radar), and remote sensing.
• Ku-band: typically range from 12 to 18 gigahertz (GHz), Ku-band is widely used in satellite communication for direct broadcast satellite television, VSAT (very small aperture terminal) networks, broadband internet access, and maritime and aeronautical communication.
• Ka-band: typically range from 26.5 to 40 gigahertz (GHz). They are increasingly utilized for high-throughput satellite communication systems, broadband internet services, and certain types of radar applications.
• V-band: typically range from 40 to 75 gigahertz (GHz). They are being explored for satellite communication systems due to their potential for high-data-rate links, especially for terrestrial backhaul and inter-satellite communication.

QZSS aims to improve the availability, accuracy, and reliability of positioning information in Japan and the Asia-Oceania region.

A technology where the functionality of RF systems is implemented primarily in software running on general-purpose digital signal processors, field-programmable gate arrays, or software-defined radio  platforms. SDR allows for reconfigurable and flexible radio systems that can  adapt to different communication standards and requirements. Also see Digital RF

A synchronous serial communication interface often used in embedded systems to connect microcontrollers with peripheral devices. It's known for its simplicity and speed making it a prime choice for short-distance communications.

A form of computer memory that retains data as long as it is powered, but does not need to be constantly refreshed to maintain it's data.

A type of modulation that transmits information more efficiently than traditional amplitude modulation

It is the serial number given to each navigation satellite and each satellite constellation is assigned a non-overlapping  numbers. For example, for the GPS satellites, as of November 2020, SVN from 1  to 77 have been issued. Some of these SVNs are operational and others are  decommissioned due to the satellite having reached its lifespan. SVN are used  by the entities managing the satellite constellations, while users of GNSS  receivers use PRN numbers to identify navigation satellites.

A specific temperature stabilised crystal providing much better frequency stability over temperature variations compared to normal crystals.

A specific sequence of bits within the navigation message broadcast by GNSS satellites. The telemetry word is crucial for receiver synchronization, specifically marking the beginning of each subframe within the navigation message.

The continuous process of a receiver monitoring and synchronizing with signals from multiple satellites to determine its position and other relevant data.

A hardware communication protocol that enables serial data transmission between devices. It is "asynchronous" because it  doesn't rely on a shared clock signal to synchronize the data transmission. Instead, it uses predefined baud rates and start/stop bits to manage data flow.

The SBAS for GPS. See SBAS

A type of semiconductor packaging where the integrated circuit is packaged directly on the wafer, resulting in a package that is roughly the same size as the die itself.

An informal abbreviation used to specifically refer to a quartz crystal oscillator.