Reference Design of nRF51822 for 1 meter range minimum

[mnhpias]

I need a reference design of nRF51822 for minimum 1 meter range . The circuit will run from CR2032 battery for at least 24 hours and will take some readings from ADC input and sends these data to another similar circuit . The receiver circuit always waits for incoming data and when ADC values will cross threshold limit then it will send data to receiver and receiver will execute corresponding commands . The sensors will run through external power supply , nRF51822 circuit will just read the data and will transmit or receive and communicate among them .

The casing of the receiver will be made of 3mm thick Acrylic Sheet and will be fully airtight , the pcb will be put inside the casing , the casing will be hollow type .

Please help me by providing a reference design which will meet these requirements , any idea , concept correction will be highly appreciated . Thanks in advance .

[Eirik Aa]

You can add the data to the advertisement package and just liesten for them. Or you can get the two devices into connected mode where battery powered sensor is in connceted mode. It can use the S110 stack, Doing just advertisement with the sensor it will run the MSU of 30uS + the ADC but in connected mode should comsume somthing between 0,3 and 4 mA. Still no problem running from the CR2032 battery. In connected mode the data can be encrypted but in advertisement everyone can listen in on the data. Depending on how you want the application to run. Power consuption of the listener till probably be around 13mA.

If you have a sample of the casing ( without any metal ) you can put it in the microwave and see if the mircowave heats up the plastic. If the plastic gets hot/warm then the casing is not siuted for this application.

[FormerMember]

A range of 1m is not a lot, and should be fairly easy to achieve. The general rules for a hardware layout are explained below:

Our reference design for the nRF51822 QFN can be found here, and for WLCSP here.

When doing the layout, the RF part of the layout should be a copy of our reference design. It means that not only the component values, but also the geometry, relative placement of the components with respect to each other, and the lengths of the transmission lines should be the same as in our reference design.

If you are planning to use a PCB antenna, I would recommend you to take a look at the whitepaper "Quarterwave printed monopole antenna for 2.4GHz", and also take a look at how the antennas are designed on our development kits. If you choose to use a chip antenna, the antenna should be placed according to its datasheet.

The antenna will also need a matching network. If using a PCB antenna, the matching network should consist of one shunt component, and if using a chip antenna, the matching network should be a pi-network, see the "Antenna tuning whitepaper", chapter 4.1 and 4.2.

The reason that matching networks are needed is the following: In RF Things work differently than in regular electronics due to the high frequencies, 2.4 GHz. If the system (chip and antenna) is not matched, there will be reflections in the transmission line, resulting in loss. The chip and antenna can be matched using a 50 Ohms reference point; matching the chip to 50 Ohm and the antenna to 50 Ohm. Which components that are needed to match the chip and the antenna to 50 Ohm depends on the initial impedances. Our reference design shows how to match the chip to 50 Ohm, using either discrete components or a balun. The antenna matching network, either a shunt component or a pi-netowork, will be used to match the antenna to 50 Ohm. The value(s) of the components in the antenna matching network will have to be found during tuning, because the impedance of the antenna depends on its close environment.

A more detailed guide can be found in the blog post "General PCB design guidelines for nRF51".