cc1101 range is very low

Could you run a test where the EM is controlled by SmartRF Studio? If this test shows expected RSSI values you have to look at your software.

Hello,

I ran a test using smartRF studio and here's my observations. I don't have a cc1101 development kit that works with SmartRF, but I have a cc430. So my test set up is.

Reciever : cc430 development kit with smartRF

Transmitter : my cc1101 device with my software

Settings : I got 4.8kbps, 903MHz sensitivity optimized settings for cc1101. Put that values to cc1101 device and imported that configs to cc430 as well. PKTLEN is 20

1. I comfortably receive packets until -90dBm. But the range is about 40-50 m.

2. After -90dBm almost all the packets are shown as CRC error/ Length violation.

3. There was only one packet which was received as a good packet with (-102dBm) out of about 30 transmitted packets.

4. The farther I move from the receiver I noticed that the least RSSI was -103dBm

I'm still wondering why my range is so tightly limited.

Thanking you,

Thilina

- Does your sender output the power you program it to?

- What type of antenna are you using? Have you tuned it to 50ohm?

- Does your receiver operate on the same frequency you are sending on? Here I'm refering to measured values.

How have you measured range?

Hello TER,

1. My sender is MSP430 + CC1101 evaluation module. I set the PATABLE registry according to the datasheet. For this test I have set the patable to the maximum value (0xC0) which according to the datasheet gives the maximum power.

2. I'm using CC1101 evm (http://www.ti.com/graphics/tool/CC1101EMK868-915.jpg)  with the default antenna that comes with the kit. So the antenna is matched to 50ohm.

3. Yes my receiver (cc430 development kit connected to smartRF ) has the same configurations as the transmitter and hence both should be working in the same frequency.

4. I'm sorry I don't have any RF measuring device to prove you the facts but I have done the configurations using TI's smartRF package.

5. The way I measure range :

I program my transmitter to transmit a packet (about 20 bytes) every one second and I keep on moving away from the receiver. When I'm close by I get the RSSI levels around -30dBm from smartrf and almost all the packets are captured. But when I'm about 40-50 m away from the receiver smartRF loses most of the packets. At least the captured packets at that range are crc error and RSSI is around -90dBm. So after about 40 - 50 m , my receiver (cc430 + smartRF ) doesn't capture any valid packets.

Do you see any issue with the above steps that I've done wrong?

Thank you,

Thilina

Please, is there someone who has obtained very long range (hundreds of meters) with CC1101? What kind of antenna you have used ? Is this range obtainable if I use recommended antenna designs proposed by TI?

With the standard kit antenna (W5017 from Pulse) supplied with the CC1101 EMs, settings of 0dBm output power, 250kbps, 1.3m above GND; a range of 250m has been achieved.

Regards, Richard.

Hello Richard,

Is this pure line of sight range without any obstacles in the middle of the path?

Yes, this was a pure LOS range test. Very difficult to determine indoor range since the indoor attenuators vary from a couple of dBs to many 10s of dBs.

Hi, Thilina

Do you have any updated measurement on the range of this module? Did you put the modules quite near the ground plane, say less than 0.5 meter?

The ground reflection has quite big effect on the RF performance. The short range you got might be due to your placing the modules quite near the ground. 

Please tell me if you have found out the problem. Thank you.

this is interesting. we did a range test this morning and we get 250m @ 10dbm output power.  our target range is 500m. once we get this 250m @ 0dbm, we will be able to meet the customer requirements.

given we have an spectrum analyzer only, what are the procedures or any tips on how we can optimize our design?

thanks

dirt road84483: Without knowing anything about your design it is a bit difficut to come up with spesific advice.

- The test itself: What sort of environment did you do the test in? Is it possible that you have some reflections or other things that makes it less than ideal line of sight. Did you have the sender and receiver above the ground on something that does not imfluence RF?

- Since you have a spectrum I believe that you have checked that the output power conducted is what you expect. Do you know how efficient the antenna is? If the efficiency is low you have lower output power than you assume and the range will be lower.

- Sensitivity: If you have a signal generator that is able to send preamble it is possible to get an idea of the sensitivity.

    Earlier this afternoon , I had the same confusing with that. I got only few , probably less than 3m. 
    Of course I am newbie and my first day of doing this. after few hours google I found I should have my firmwave ( cc1110 ) updated with the config which made by SmartRF studio given instead the one which the seller gave me.
    Now I could have my AP to ED with a distance about 50M from inside house to outside ( crossing about two wall ) . I will have a test for more about range tomorrow outside, maybe in a football yard or someplace like that.
    I just wonder had you just made a choosen as I ? because as I supposed , It should be easy to used .

TER said:

dirt road84483: Without knowing anything about your design it is a bit difficut to come up with spesific advice.

- The test itself: What sort of environment did you do the test in? Is it possible that you have some reflections or other things that makes it less than ideal line of sight. Did you have the sender and receiver above the ground on something that does not imfluence RF?

- Since you have a spectrum I believe that you have checked that the output power conducted is what you expect. Do you know how efficient the antenna is? If the efficiency is low you have lower output power than you assume and the range will be lower.

- Sensitivity: If you have a signal generator that is able to send preamble it is possible to get an idea of the sensitivity.

Manually holding the board could de-tune the antenna some. If you look at http://www.ti.com/lit/an/swra338/swra338.pdf the report say that the efficiency is 25%. In the equation you have to adjust the Transmit output power accordingly to the real output power from the antenna. The range will also be affected by in which angle the antenna is placed in.

If a trace is about 1/10 of a wavelength or shorter it will not act as a transmission line and hence the width of the trace is of less importance. But you need Z132 and Z133 in your design since this tune the antenna to 50ohm. If you don't have these components in your design the antenna will have fairly poor performance. 

TER

thanks so much for the valuable reply. We will reflect on this and make the necessary changes on our design

Hi TER,

thank you so much. we were able meet our 425m range and were able to exceed it by a large margin! thanks so much.