RF module

The term RF module can be applied to many different types, shapes and sizes of small electronic sub assembly circuit board. It can also be applied to modules across a huge variation of functionality and capability. RF modules typically incorporate a printed circuit board, transmit or receive circuit, antenna, and serial interface for communication to the host processor. Most standard, well known types are covered here: • transmitter module • receiver module • transceiver module • system on a chip module. Transmitter modules An RF transmitter module is a small PCB sub-assembly capable of transmitting a radio wave and modulating that wave to carry data. Transmitter modules are usually implemented alongside a microcontroller which will provide data to the module which can be transmitted. RF transmitters are usually subject to regulatory requirements which dictate the maximum allowable transmitter power output, harmonics, and band edge requirements. Receiver modules An RF receiver module receives the modulated RF signal, and demodulates it. There are two types of RF receiver modules: superheterodyne receivers and superregenerative receivers. Superregenerative modules are usually low cost and low power designs using a series of amplifiers to extract modulated data from a carrier wave. Superregenerative modules are generally imprecise as their frequency of operation varies considerably with temperature and power supply voltage. Superheterodyne receivers have a performance advantage over superregenerative; they offer increased accuracy and stability over a large voltage and temperature range. This stability comes from a fixed crystal design which in the past tended to mean a comparatively more expensive product. However, advances in receiver chip design now mean that currently there is little price difference between superheterodyne and superregenerative receiver modules. Transceiver modules An RF transceiver module incorporates both a transmitter and receiver. The circuit is typically designed for half-duplex operation, although full-duplex modules are available, typically at a higher cost due to the added complexity. System on a chip (SoC) module An SoC module is the same as a transceiver module, but it is often made with an onboard microcontroller. The microcontroller is typically used to handle radio data encapsulation (packetisation) or managing a protocol such as an IEEE 802.15.4 compliant module. This type of module is typically used for designs that require additional processing for compliance with a protocol when the designer does not wish to incorporate this processing into the host microcontroller. == Host microcontroller interface ==

RF modules typically communicate with an embedded system, such as a microcontroller or a microprocessor. The communication protocols include UART, used in Digi International's X-Bee modules, Serial Peripheral Interface Bus used in Anaren's AIR modules and Universal Serial Bus used in Roving Networks' modules. Although the module may use a standardized protocol for wireless communication, the commands sent over the microcontroller interface are typically not standardized as each vendor has its own proprietary communications format. The speed of the microcontroller interface depends on the speed of the underlying RF protocol used: higher speed RF protocols such as Wi-Fi require a high-speed serial interface such as USB whereas protocols with a slower data rate such as Bluetooth Low Energy may use a UART interface. == RF signal modulation ==

There are several types of digital signal modulation methods commonly used in RF transmitter and receiver modules: • ASK • OOK • FSK • Direct-sequence spread spectrum • Frequency-hopping spread spectrum == Main factors affecting RF module performance ==

As with any other RF device, the performance of an RF module will depend on a number of factors. For example, by increasing the transmitter power, a larger communication distance will be achieved. However, this will also result in a higher electrical power drain on the transmitter device, which will cause shorter operating life for battery powered devices. Also, using a higher transmit power will make the system more prone to interference with other RF devices, and may in fact possibly cause the device to become illegal depending on the jurisdiction. Correspondingly, increasing the receiver sensitivity will also increase the effective communication range, but will also potentially cause malfunction due to interference from other RF devices. The performance of the overall system may be improved by using matched antennas at each end of the communication link, such as those described earlier. Finally, the labeled remote distance of any particular system is normally measured in an open-air line of sight configuration without any interference, but often there will be obstacles such as walls, floors, or dense construction to absorb the radio wave signals, so the effective operational distance will in most practical instances be less than specified. == Module physical connection ==

A variety of methods are used to attach an RF module to a printed circuit board, either with through-hole technology or surface-mount technology. Through-hole technology allows the module to be inserted or removed without soldering. Surface-mount technology allows the module to be attached to the PCB without an additional assembly step. Surface-mount connections used in RF modules include land grid array (LGA) and castellated pads. The LGA package allows for small module sizes as the pads are all beneath the module but connections must be X-rayed to verify connectivity. Castellated Holes enable optical inspection of the connection but will make the module footprint physically larger to accommodate the pads. == Wireless protocols used in RF modules ==

RF modules, especially SoC modules, are frequently used to communicate according to a pre-defined wireless standard, including: • Zigbee • Bluetooth Low Energy • Wi-Fi • IEEE 802.15.4 • Z-Wave However, RF modules also frequently communicate using proprietary protocols, such as those used in garage door openers. == Typical applications ==

• Vehicle monitoring • Remote control • Telemetry • Small-range wireless network • Wireless meter reading • Access control systems • Wireless home security systems • Area paging • Industrial data acquisition system • Radio tags reading • RF contactless smart cards • Wireless data terminals • Wireless fire protection systems • Biological signal acquisition • Hydrological and meteorological monitoring • Robot remote control • Wireless data transmissions • Digital video/audio transmission • Digital home automation, such as remote light/switch • Industrial remote control, telemetry and remote sensing • Alarm systems and wireless transmission for various types of low-rate digital signal • Remote control for various types of household appliances and electronics projects • Many other applications field related to RF wireless controlling • Mobile web server for elderly people monitoring == RF module certification in case of final product integration ==

Final regulatory product compliance based on an integrated, compliant RF module (as most IoT devices these day's) is a common misunderstanding. A module compliant to the essential requirements of the countries regulation (FCC, CE, ICES, ANATEL etc.) does hardly ever cover the final product. However, this does not mean that full compliance testing is required when integrating a compliant RF module. Integrating a compliant module has a lot of advantages. The RF module is essential in this day’s consumer product but also only a part of the final product. Radio modules have evolved during the years. Onboard voltage regulators, integrated antenna generally try to ensure that the radio phenomena stay the same no matter of their host. You can refer to most RF spectrum measurements on a modular level for compliance when testing and certifying your product at an ISO 17025 accredited EMC, RF laboratory. At the end it is the final product that needs to comply with the regulations. Aspects as health, safety, Radiated susceptibility can not be covered on a modular level. == External links ==