Does ground reflection have huge effect on CC2530??

Thanks TA.

That explains my observation. So if ground reflection has that much effect on the radio performance, what do you think I should do to get 100 meter range?

In my application, the transceivers will be placed at 20-30cm off the ground which is a must. I could see two options: 1. use CC2591 power amplifier, 2. choose other solutions at 800-900MHz. Which do you think will much guarantee  the performance?

TA, the ground reflection is basically the multipath effect issue? I made some simple estimation and I think for zigbee Baseband 250kbps(2M chip rate), there should not be significant ISI issue. so multipath should not be a big problem.

please correct me if I am wrong.

Rui

Rui, 

The fades are actually bigger and can in most case attenuate an entire Zigbee channel. Some time ago we published a paper on this topic including some real life measurements. You might find this interesting.

http://low-powerwireless.com/blog/designarticles/frequency-hopping-diversity-improves-low-power-wireless-system-performance/

Regards,
/TA 

TA, Thanks, I will take a look at your post.

please see my calculation, 2M bps in chiprate , so the symbol period is 1/2M = 0.5us. for a serious ISI, the coherence time should be larger than 0.5us. which means the difference of arrival signal should be 0.5*10^(-6)*3*10^(8) = 150m. dose ground reflection casue so large difference?

Also I don't quiet understand why sub 1G can solve multipath issue. it is only carrier frequncy change, not base bandwidth change(or sub 1G has less 250bps rate or less than 2M chip rate?).

Thanks

Rui 

Hi, TA

Is there any Sub1GHz solution which gives at least 100kbps data rate while having a good range in my situation, I mean the near ground placement?

What about using CC2591 together with CC2530, which gives 18dBm TX power extra?? I have started with CC2530 for a long time, so I prefer to make some usage of it. 

At least 100kbps data rate, 100 meters range are my primary requirements. 

Thank you for your information

Jinkang,

If your target is 100meters, a CC2530+CC2591 combo should work just fine. I believe it should be fine, but please make sure that you allowed to transmit at those power levels in the countries you are targeting. 

Regards,

/TA 

Hi Jinkang

if you just require 100m and 100kbps, that should be fine. Also increasing TX power by CC2591 should not solving any multi path problem. Maybe your problem is not at multi path side, but rather in tx range side. in this case, sub 1G is better.

Rui 

Hi, TA and Rui

It has been a late followup. Thank you for your recommendations. 

When I did the calculation according to the article on ranging measurement from TI (http://www.ti.com/lit/an/swra169a/swra169a.pdf), the fading was like 40dB for lawn area. Do you think it reasonable?? Do you think the RF signal would be coupled to the ground when the transceiver is placed near the ground?

Anyway, now I am going for sub-1GHz solutions, hopefully they would work. Usually those transceivers have been built for different frequency bands, such as 433, 868 and 915 MHz. But we know that for different bands there should be different lengths for a proper antenna. I am wondering what TI recommends for the solutions on antenna design if we want to have the same setup on hardware for different countries? I mean, when we sell our products in different countries, we want to make no (or the least) change on the hardware.

Thank you!

Jinkang, 

The answers depends more on regions where you want to operate than physics. They are all good choices, but for operation in the US the 915MHz band is obvious choice. 868MHz or 433 in Europe.

Regards,
/TA 

TA,

This I understood. But how about antenna? The antenna design should aim for different central frequencies when designing the PCBs for different regions. if I want to keep the same PCB in different regions to reduce the cost, does it mean I cannot use PCB antenna in my design?