Electronics > RF, Microwave, Ham Radio

Simple radio solution for ultra low power low bandwidth

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kuon:
I am working on a medical sensor on which I have a cortex M SMT32 micro controller.

The micro controller is doing all the job and with it's deep sleep I can have a very low power consumption.

That being said, I need a low power, low bandwidth (1kb per minute), low range but high penetration (should be able to penetrate a medical ward wall) wireless solution.

At first, I tried an NRF54820 based bluetooth solution, but I had some issues:

- bluetooth is so damn complicated...
- the SDK and tools are very heavy, and a simple hello world program can be very hard to manage
- the 2.4Ghz band is just too crowded where I would need to deploy those devices
- penetration of the 2.4Ghz band can be problematic, even with thin walls

For this reason, I am looking for a simple transceiver, in the 826Mhz band, SIP based with a simple interface (UART can work but SIP often provides better performances which yield to less time awake and lower power).

So far I found the analog ADF7024.

It seems to be the perfect candidate, it has a 240Bytes buffer and a simple SIP interface.

Now I have two questions:

- Anybody has experience with what I am doing, is this a good solution/chip?
- I have never done antenna design (except for NFC), and I would like to use a PCB trace antenna if possible. I found many different design and vague schema, but no proper schematic with specifications. I also have no idea how to tune the RF matching network highlighted in the datasheet (below image). I have a tinyVNA which I used a few times for NFC antenna designs, but those only have a single tune capacitor, so it is very easy. I realize this is a broad question, but this forum has always been very informative.

kuon:
I made some researches about the impedance matching, and I think the easiest path is to:


- copy the schematic and layout from  EVAL-ADF7024DB2Z (eval board with 50 Ohm anteanna connector)
- use a chip antenna like W3013 from pulselarsen

In the W3013 datasheet, there is an optional "shunt" between the end of the antenna line and ground, what is its purpose and how to calculate its value?

radiolistener:

--- Quote from: kuon on January 29, 2022, 04:29:34 am ---In the W3013 datasheet, there is an optional "shunt" between the end of the antenna line and ground, what is its purpose and how to calculate its value?

--- End quote ---

this is a matching component (capacitor or inductor). It's value is selected during tuning process.

voltsandjolts:
Some options:

RF Solutions radio modules

433Mhz might give better wall penetration than higher frequencies, depending on power of course.

geggi1:
Look at some of the solutions used for RFID.

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