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The applications for antennas are limitless and expanding quickly, thanks primarily to the availability and diversity of Internet of Things (IoT) devices. The difficulty of building cellular goods continues to expand, with the number of frequencies the antenna must cover increasing rapidly from the initial GSM/GPRS technology to the newest 4G/LTE and, indeed, the upcoming debut of 5G, with the latter needing about 7 frequencies. The orientation and placement of an antenna within a device enclosure affect not only its performance but also has the potential to negatively impact the surrounding electronics and worst case, the mobile operator.
Half-wave antennas were first employed in mobile phones and modules in the form of a simple wire or PCB track. Most RF front ends now employ MIMO (Multi-In Multi-Out) technology, which allows the antenna to have multifunctional tuning to give a larger variety of frequencies.
1980s Cell Phone
GSM Module Antenna
The position and orientation of the antenna might seem insignificant to some since it is often considered late in the design process, and many systems may default to whatever is readily accessible. They may choose a standard 2G or 3G antenna, which may work in many situations; but performance is likely to suffer as a result.
When working in congested environments with a plethora of other cellular devices, a tuned antenna set in proper alignment will always maximise functionality.
This is especially true when operating at a longer distance from the signal source (remote locations) or in densely populated areas with metal and/or reinforced concrete structures (cities).
Cellular signals differ in terms of transmission technique and wave propagation over the air.
A device antenna should ideally be 'circular polarised,' however, most polar diagrams will have some gain in one direction (try rotating your cell phone when you have a weak signal). Checking the antenna orientation to the typical signal source can yield optimal performance; this is especially useful in stationary distant applications that connect to the nearest fixed base station.
A Yagi (multi-element directional) antenna may be useful for some extremely distant applications. Cell towers differ depending on the type and date of construction; modern LTE towers contain an X-shaped antenna that allows them to broadcast between vertical and horizontal polarisation.
Similarly aligning your antenna can improve performance.
The device containing the cellular transceiver is normally designed to be put inside an enclosure. An external antenna would be ideal for the greatest signal, but aesthetics and user needs surrounding size and mobility usually exclude this possibility; users don't want to carry a mobile phone with an external antenna as they did in the 1980s.
The kind of enclosure and the antenna's relative position to the source of transmission must be taken into account. The wires or PCB tracks connecting the output to the antenna will suffer from loss; the closer to the source, the better. You will have control over this if you create your own transceiver; if you use a standard module, you will connect through a coaxial-style socket or soldered junction.
A typical PCB MIMO antenna for a cellular module that supports 3G/4G and WiFi.
Alternatively, if the module is built to be soldered to the PCB, the antenna may be designed within the tracks of the mounting PCB. In this situation, more attention to antenna matching and an understanding of design characteristics are necessary. This will also have an influence on certification final testing.
Once an antenna has been selected, one of the most important considerations is where it will be placed within the enclosure; one of the most important factors to consider is the decrease of spurious emissions from the device. If end certification has to be achieved, screening around oscillators, high-speed processors, and displays will be required.
Much attention has been paid to the dangers of mobile phone radiation to users. However, testing remains inconclusive, despite the fact that minimising mobile phone radiation is plainly desirable and may be accomplished by making an enclosure out of metal or plastic-coated metal. Enclosing an antenna in this manner functions as a faraday cage, inhibiting electromagnetic fluxes. To attain the best results, all designs must make certain concessions.
The great majority of designs include a natural opening inside the metal casing on the left for the display, which can provide a convenient place for the antenna; alternatively, the antenna might be put on the back surface if the metallization is removed.
Modern modules and mobile phones have increasingly complex MIMO antennas, which must be optimised for the several frequency bands already in use. Careful alignment is required while producing and positioning the antenna to provide the optimum fit in both mobile and stationary applications. Furthermore, the design of the enclosure to maximise radiation from the antenna while minimising spurious undesired signals from diverse sources complicates the design and location.
To accomplish a quick time to market, the ideal strategy is to follow an antenna manufacturer's recommendations. Software modelling and test house analysis are critical to the final design since they allow for fine-tuning. Siretta is ideally positioned to support your next design, with a wide range of antennas available, ranging from embedded PCB designs to high-gain directional pole-mounted Yagi types.
The mounting design will be the beginning point in choosing, whether it is a simple stick in place, directly connected, embedded, magnetic, bolt-on or pole/wall mounted. After that, just select the communication technology that best matches your application. (2G/3G/4G, WiFi/Zigbee/Bluetooth, ISM Band/NB IoT/LoRa/SigFox, GPS or of course, a combination of 2 or 3 types) Siretta has developed their own selector tool to assist Antenna Selector Tool or contact our knowledgeable team of professional development and application engineers that provide full end-to-end solutions with a strong emphasis on high-level system architecture.
Look out too for Siretta’s New Style Antenna Datasheets which include:
- VSWR, Return Loss & Radiation Efficiency charts
- Spectral response and performance tables
- Gain Plots in 2D and 3D
Siretta also provides customised consumer solutions through their design services.