Performance Levels

High data rate – Cat-6, Cat-9, Cat-12: Found in high power, high data rate devices, Consumer mobile devices, base stations, and range extenders

Low data rate – Cat M1, NB-IoT, LTE-M: These operating categories are typically found in low power IoT or mobile devices such as smart meters, sensor nodes, and distributed machine communication

Source: u-blox

Subscriber Identification Module (SIM) Cards and Data Plans

Pre-paid and monthly plans available for cellular data:

Cellular SIM Cards and Data Plans

Antennas

Choose from stock antennas or build your own custom antenna with the Antenna Builder service from Taoglas:

Stock Cellular Antennas

Custom Antenna Builder

Transceivers, Gateways, and Routers

These devices negotiate the transfer of data and determine how data will be transferred on the network:

Cellular Gateways and Routers

Cellular Transceiver Modules and Modems

Interference

If you have ever heard static on the radio, wireless headphones suddenly sounding glitchy or the loss of data packets from a wireless sensor, then you have experienced interference.

Interference may prevent reception altogether until the interference is removed, may cause only a temporary loss of a signal, or may affect the quality or amount of data sent across the wireless channel.

Dealing with interference

There are a many different methods that can eliminate or reduce the interference from outside sources.

Shielding: RF shields and RF gaskets can ensure that the enclosures are fully protected against RFI and EMI intrusion

RF Shields – One of the most common ways to reduce incoming interference or prevent radio emissions from leaking out is RF Shielding. The purpose of an RF shield is to either block or conduct away interference signals from the components on that are the most susceptible to interference such as RF amplifiers.

RFI and EMI – Contacts, Fingerstock and Gaskets – Includes foam gaskets that can seal gaps in external enclosures.

RFI and EMI – Shielding and Absorbing Materials – Includes sheets or rolls of material to reflect or absorb interfering signals.

Directional antennas to carefully direct and limit EMI from spreading in unwanted directions

Directional Antennas – Directional antennas are another option to reduce interference from outside sources. By only allowing reception from a particular direction, they can filter out unwanted sources along the transmission path. However, these are large devices that more suitable for fixed installations with a predictable reception path.

Wireless Transceivers

Transceivers are a combination of both wireless transmitter and receiver circuits in one package or device. Examples of products that use transceivers include Cell phones, two-way radios like walkie talkies, HAM Radios, and IoT connected devices.

Form Factors of Transceivers

Integrated Circuits (ICs) – contain the necessary circuity to form and decode wireless signals. However, as they are just the IC, they require circuit board design and assembly before they can transmit. Not ideal for the first-time maker but allows for close system integration

Modules and Modems – packages that can be integrated into a wireless design. Some modules have integrated RF shielding and power management features, which can reduce the amount of additional design needed

Finished Transceiver Unit – ready to use devices and units to quickly set up a wireless network. Ready to be powered on and connected to a network, these finished units take the guess work out of wireless network deployment and are ideal for plug and play operations when connecting sensors or setting up data links

Development boards and kits – for experimentation and prototyping, they are a maker's best friend to get started in the world of RF development. With the world's most popular manufactures and suppliers in stock at DigiKey, covering every frequency, wireless band, and application DigiKey has everything you need to experiment and move your ideas from prototype to production

Antenna Integration

Integrating an antenna into your design can be an extremely difficult task and will vary across many factors of your design. We can't cover every factor, but the list below will get you started. In general, more metal (bigger antenna) means better antenna performance if it's matched properly in your design.

External Antenna

If you are designing using an external antenna, some considerations will be different from those using an embedded or internal antenna. You may need a longer cable to reach a premium transmission point. Introducing cables and connectors introduces losses into the signal chain and should be planned for so these losses won't considerably affect the performance of your design. External Antennas may have a higher gain also and that should be considered as well as it may put your design outside of the acceptable certification parameters. Location, placement and orientation of the antenna and cable type used will be key factors in the performance of an external antenna.

Internal Antenna

Internal or embedded antennas are often chosen due to size limitations, this often means the performance of the antenna is not as great as their external counterparts and the design is critical to getting the most out of the embedded antenna. Size and placement should be the first considerations for an internal antenna as these will determine which antennas may be used. If your device will be inside a metal box, an internal antenna likely won't work at all. If the antenna will be placed on a PCB you will need to determine what amount of ground or component clearance will be needed for the antenna chosen, some antennas may be designed to sit on top of a ground plane, and some will require a certain amount of ground clearance to operate effectively.

Antenna Terminology

• Gain – measures how effectively the antenna transmits power in a specific direction. This gets referred to as peak gain, average gain or both on antenna datasheets.
• Antenna Efficiency – ratio of the power radiated versus the power fed to the antenna terminal. Higher efficiencies indicate better performing antenna at a given frequency.
• Voltage Standing Wave Ratio (VSWR) – Measures how effectively power is transmitted from the source through a transmission into the antenna (load). VSWR is measured as a ratio of input power to output power, a measure of less than 2:1 is considered a good match, the higher the VSWR the greater the mismatch.
• Antenna Impedance – Measures the opposition of current when a voltage is implied. This is the value that must be matched to the source impedance to transmit power efficiently through the antenna. Most radio equipment is built for an impedance of 50 ohms.

Popular Antenna Types

Ceramic Patch – Support wider frequency bands, often used with GPS

Chip – Small footprint, soldered directly to PCB

Whip – A traditional antenna design that has been used for FM Radio, but can be applied broadly

Flat Patch – Commonly used in portable wireless devices

Micro Strip Calculator

The IPC-2141 Trace Impedance Calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. A field solver may be required for final circuit analysis.

dBm To Watt Converter

The dBm To Watt converter tool converts power measurements between units of decibel-milliwatts (dBmW) and watts (W).

RF Connectors and Cable Assemblies

A Radio Frequency Connector (commonly called a RF Connector) is an electrical connector designed to work with electrical signals in the radio frequency range, typically between the range of 20kHz (thousands of cycles per second) to multiple gigahertz (billions of cycles per second).

A key feature of the RF connector is the layer of RF shielding and insulation in the connector body to maintain continuity of shielding that coaxial cabling offers.

A collection of RF connectors, drawn to scale Source

Common RF Connectors

SMA (SubMiniature version A) – has a frequency range usually up to 12 GHz but SMA connector variants allow up to 18 GHz and higher. These small high frequency applications typically find SMA connectors in consumer grade microwave applications, the most famous of which is the RP-SMA connector found on Wi-Fi router antennas.

Type N - named after its inventor Paul Neill of Bell Labs, is a Threaded RF connector made for joining coaxial cables. Working frequency range up to 11 GHz make this weatherproof and durable connector perfect for low microwave RF applications where outdoor use and simple installation make it popular nearly 80 years after introduction. A key usage point is the 50 ohm and 75 ohm version of the N Type connector are not cross compatible and may cause damage to each other if mated.

BNC - is a miniature RF connector with a quick connect twist. Originally made for military radio equipment in the 1940's the BNC connector has become a popular connector for RF test equipment and consumer electronics such as video. Typically working frequency is up to 4 GHz, but up to 11 GHZ is possible with signal degradation.

TNC - short for Threaded Neill-Concelman, is a threaded version of the BNC connector. The threading locking option allows for a more secure and stable connection between the two mating sides of the connection allowing for operation up to 11 GHz. The miniature size and weatherproof connection has made TNC popular in radar and aerospace applications.

Micro Coaxial Connectors (MCX) – have the same inner contact and insulator dimensions as the SMB connector but are 30% smaller. MCX is standardized in European CECC 22220. They use a snap-on interface and usually have 50 Ω impedance. They offer broadband capability from DC to 6 GHz.

Micro-Minature Coaxial connectors (MMCX) - like MCX but smaller. MMCX connectors conform to the European CECC 22000 specification. MMCX is a micro-miniature connector with a lock-snap mechanism (quick disconnect) allowing for 360 degrees of rotation and usually has a 50 Ω impedance. It offers broadband capability from DC to 6 GHz.

 

For an RF Connector how can I tell if it's regular polarity or reverse polarity? View Answer

First determine the gender of the connector:

• Male connectors have threads facing inward to the connector center
• Female connector has threads facing outward

Simply put: The male connector fits on the outside of the female connector when mated.

Second check the central contact.

In the simplest case the central contact of a pair of mating RF connectors will be one pin and one receptacle socket on either side of the interconnect.

• In standard polarity connectors, the center connector will have the pin contact, and the female side of the connector will have the receptacle socket
• Reverse-polarity connectors will have the opposite contact of a standard connector

An RP male connector will have inward facing threads and a female socket for a central contact.

And RP female connector will have outward facing threads and a male pin for a central contact.

For more on connectors and genders, visit the Interconnect Applications & Technologies page.

RF Coaxial Cable Assemblies

The most common cabling used in RF design is coaxial cable.

A common U.FL RF connector attached to a coaxial cable

RF Front End

The Radio Frequency Front End, also called the RF Front End is the circuit elements and components between the receiving antenna and mixer stage for a radio receiver. This stage of the radio receiver takes the incoming radio signal, filters unwanted external signal noise, amplifies the target signal and converts the radio frequency to lower frequency that the rest of the radio receiver circuits can work with.

Front End Chips

Front end solutions often contain several components from the "Front end components" section below in a single IC (integrated circuit).

Modern RF circuits typically have front end circuit components integrated into a single chip package, like this one

Front End Components

The RF front end components can have many different stages but typically has 4 large groups of components:

A Band-pass RF Filter that receives the incoming radio signal from the receiving Antenna. This filter's role is to pass the desired signal along the processing chain and reduce out-of-band signals from overpowering later processing stages.

An RF amplifier, commonly called a Low Noise Amplifier which is used to amplify weak signals without adding extra noise.

A local oscillator, which generates a stable radio frequency signal. The Local Oscillator can either be a fixed frequency or tunable, but the stability and accuracy is very important as this signal is used in the mixer stage before further processing.

A mixer stage which mixes the received and filtered radio signal from the Band-Pass filter and the signal from the local oscillator. The resulting output from the mixer is a combination of both these signals, which can make signal processing, filtering and extraction easier.

Low noise amplifiers, also called LNA are RF circuit devices which amplifies a low power signal without adding unwanted noise or interference. LNAs are designed to minimize the amount of interference added to the amplified signal.

Power Amplifiers, also called PA are a type of amplification circuit that takes low power RF signals and amplifies them into high power signals for transmission from antenna.

RF Switches are devices that can switch RF signals between signal chains. Like common electrical switches, RF switches can come in many different configurations able to switch between different paths.

RF Passives

Attenuator

An attenuator is a RF circuit component which reduces the amplitude (or strength) of a signal passing through it.

An attenuator is a RF circuit component which reduces the amplitude (or strength) of a signal passing through it. Attenuators are the opposite of an amplifier, instead of increasing a signal power, they reduce it. While it may seem counterintuitive, there are reason for reducing signal power. These reasons include: matching signal levels in the processing chain, extending dynamic range, impedance matching, and signal calibration. Unlike RF filters that typically reduce signal strength for a frequency range, attenuators work over the whole frequency spectrum range.

Balun

This balun component has had the top cover removed and you can see the two transformer loops one floating, the other grounded.

Baluns (short for balanced to unbalanced load converters) is an RF circuit component that allows balanced or unbalanced circuits to connect without disturbing the impedance of either circuit and converts a differential signal to a single-ended signal or vice versa. A Balun can be modeled as a simple two winding transformer with the unbalanced side grounded and the other side of the transformer floating.