Recurrent step when making an IoT device, the antenna matching is a key activity to get the right radio performance for your device. You radio strip and antenna must be tuned to match a 50 Ohm impedance. For doing this I’m using a miniVNA Tiny Vector Network Analyzer (until a switch to my Rigol Spectrum Analyzer) as described on the previously linked post.
Currently, to tune my antennas, I’m also using the Atyune tool. This tool is free and really good to make the tuning but also to get a better understanding of what you are doing. Let’s see how to proceed.
The LoRa Radio Node is an AVR Arduino board with a RFM95 LoRa module. This all-in-one LoRa module allows to have a LoRaWan device for a reasonable price around 15€. You need to add a battery (like a LS14500 3,7V battery) on the battery holder for a 4€ extra cost to make it mobile. LiPo option are also available using the power connector. Even if the connectors are looking like grove, they are not compatible so you will have to make your own wiring to connect extensions.
This post is reviewing how to getting started with this board to fire your first LoRaWan frame over The Things Network.
GNURadio is an open-source software for making Software Defined Radio. It can be used to model a radio transmission or the process a real radio communication.
Scapy is a python tool set able to interact with GNURadio. Basically GNURadio will receive an signal from a SDR key and process it to get a digital sequence. Scapy will process this sequence and potentially generate a new sequence to be process by GNURadio to be transmitted.
There are plenty of example of GNURadio/Scappy usage to hack, simulate, learn many radio protocols like WiFi, GSM, Bluetooth… I want to play a little with Sigfox also so that’s why I started to investigate on this tool.
As this tool is a bit complicated, this post details the key element having helped me to getting started with this tool.
Sigfox just released publicly its Radio Signal Analyzer tool. This is a tool for the device & module maker to prepare the P1 certification : basically it checks the radio signal shape, power… and tell you if you are following the requirements.
The tool have to be used with the SIGFOX SDR dongle provided with the SNEK tool.
The software solution can be downloaded here : https://support.sigfox.com/downloads/sigfoxradiosignalanalyzer.iso
IoT design a usually a matter of antenna as already seen in different previous blog post. Antenna performance is the assurance of your capacity to deploy your object in larger zone and a way to save energy by reducing transmission power.
As we will see, if you get a hardware component and simply put it in a box its radio behavior will be totally different as the box is impacting the transmission.
This post will practically show you the impact of a box on a device radio quality.
I’ve got my miniVNA Tiny+ this summer and start making test with it. A VNA is a Vector Network Analyzer. Behind this dark name, this is a tool able to analyze the radio response of your circuit and ensure your circuit is tuned to the right frequency. From the data measured by this tool you can find the right adaptation circuit to match your central frequency.
The miniVNA Tiny+ is a low cost VNA solution less than 300€ covering frequencies from 1MHz to 3Ghz. These frequencies are good for most of IoT need : LPWAN around 868MHz and Bluetooth at 2,4GHz. The steps are 10Hz for a large precision. With two ports you can measure S11 – power transmitted and received over the same port – and S21 – power transmitted from port 1 and received over port 2.
The miniVNA Tiny+ is an usb solution working with a computer connected to and a software running on the computer. The software is based on Java and may support different Operating Systems.
Episode 3 & 4 of my Youtube series about LPWAN is about antennas for LPWAN and impact on object design. The episode 4 go deeper on the way to improve radio performance by tuning and adapting antennas with matching circuit.
As usual, this series of post are summarizing in English the content of my French video on youtube.
The RF 868MHz is a public bandwidth European Low Power Networks (LPWAN) as Sigfox and LoRaWan are using for communicating.
This bandwidth is regulated by different norms like ERC-REC-70-3E in Europe and have national norms in relation. In France ARCEP 2014-1263 seems to be the last one validated in the JO on the 30th of January 2015. The following video is a second episode of my VLOG on LPWan technologies. As usual, the video is in French but this post will give you a overview in english.
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