ANT Forum

Dear All,

I have a setup with two sensorcore modules and an AP 281M4IB (Revision D) module working as a receiver in continuous scan mode. The sensores transmit at 2 Hz, the system is setup at 2.500 GHz. While the sensors are setup with 0 dBm tx channel power, the receiver is setup with the default rx power (-20 dBm).

While everything works fine at home (with WLan) for sufficient distances of about 10 m (with solid walls), in the lab where the system should be installed I don't get a reliable connection.

I do receive data when I put the receiver very close to the sensor (~30 cm) but the connection will be dropped at larger distances or when I put my hand in the line of sight. All in all I need app. 5 m transmission range with one light wall in the way.

In some places where I can not put the receiver (room passage) I can receive data but the connection eventually gets dropped after some minutes and will not recover even moving the receiver back closer to the sensors. Starting/stopping the sensors at home, however, causes no problem, the data will be received when the sensors are back up.

I could make sure the AVR keeps working as it keeps incrementing a wall clock. Also, I find the same behaviour using another AP281 connected to a PC using the development kit USB stick and AntwareII.

I do not get any error messages from ANT.

I know the lab is heavily RF poluted due to some badly shielded xenon arc lamps which will e.g. eventually flash some other sensors eeprom while lying in the drawer. I also have WLan and DECT in that space, also air conditioners, several PCs and neon-lamps.

The modules are put in regular ABS cases. The receiver is made of an AVR (@5V), and the AP281M4 is connected via a 74HC4050 level shifter, and is powered with 3.6 V using a voltage regulator. I use a 2-layer pcb, the rx/tx lines are app. 6 cm long.


Any ideas how to improve the rx behaviour of the receiver? Any experiences e.g. pimping the AP281 with a better antenna? Any modules with better antenna out there?

My strategy by now is to put everything into a metal case and use an external antenna for the ant module, if necessary with an amplifier.

As I have no experience (and not even measurement tools for that purpose) making my own module antenna is not an option. I will need a proven design or better a ready made module.

Best Regards,

Peter      

It appears there are significant interference on the same frequency in your lab; which caused the communication link degradation. I would suggest you to change the RF frequency, as ANT has 78 RF channels from 2403~2480, you can test them one-by-one and could find one channel substantially improve performance.

The TX power in receiver side is too low; you need set it to 0dBm.

The AP2 module is optimized antenna design which will maintain the best RF performance; if you need add external antenna instead, you have to make sure the 50ohm impedance matching with the ANT radio.
Caution should be taken, if there is heavy interference environment, increasing the gain of the antenna, may cause notable degradation. To add an amplifier can improve the performance, but it may violate FCC request.      

Hi kebinw,

thanks for the reply. I will check some other frequencies and also set tx power to 0dB.

I will come back with results

Best Regards,

Peter