KW45 CS RF multipath issue

[key1]

UG10107 Antennas for channel sounding applications document.There is a sentence in this document. The sentence is"When measuring time delays in between packets and phase shifts in-between tones, distances, and positions can be estimated accurately. When the signal propagates in multiple paths, the multipath effect can be considered by using at least two antennas receiving signals from different directions.” in page 2.  

1.Why do dual antennas solve multipath issues?

2.What is the main difference between a dual antenna and a single antenna?

3.Is this multipath mainly solved algorithmically?

[Christine_Li]

Hi, @key1 

Thanks for creating case to us and hope you are doing well.

I will check it internally and share with you once have any updates.

Best regards,

Christine.

[key1]

hello Christine 

Thanks!

Please also reply as soon as possible to help solve this problem.

[Christine_Li]

Hi， @key1 

1.Why do dual antennas solve multipath issues?

[Christine]:==>Not dual antennas, multi antennas is suggested. As the sentence you quoted, it mentioned: "at least two antennas".

To determine the distance, a single antenna is sufficient to measure the signal strength.

The direction estimate requires an array of antennas to measure time delays, phase shifts between the elements. The direction of arrival can be determined from those delays, phase shifts.

2.What is the main difference between a dual antenna and a single antenna?

[Christine]:==>Please see the answer in question 1.

3.Is this multipath mainly solved algorithmically?

[Christine]:==> Not only algorithmically, but also the properties of the Radio-Frequency (RF) circuitry and antennas are essential.

Best regards,

Christine.

[key1]

hello @Christine_Li 

Thanks for your reply!

Please explain it to me.Why does direction estimation require an antenna array to measure time delay and phase shift?

Best Regards

[Christine_Li · Accepted solution]

Hi， @key1 

We face diffractions, reflections, mutual interferences, and other electromagnetic phenomena in a complicated environment. As a result, received power varies with direction and time. To suppress these phenomena, two perpendicularly located antennas can be used to receive waves from different directions. 

Best regards，

Christine.

[key1]

Hi@Christine_Li 

Does this mutual perpendicularity refer to polarization? 

The two antennas are not working at the same time. How do two antennas that are perpendicular to each other receive waves from different directions?

[Christine_Li]

Hi, @key1 

You are right. 

If linearly polarized antennas, for example, if monopoles are used, the transmitter antenna and the receiver antenna must be oriented in parallel because the field intensity is oriented in the antenna axis. Otherwise, the polarization mismatch has to be taken into account. The received power is related to the field intensity projection to the antenna axis. If perpendicular, a minimum power is received.

So previous comment is in theory for understanding different directions antennas can receive different direction's wave. But in the actual using case, need to do some experiments and simulations to put antennas better.

For example,  the current generation of KW45 boards is equipped with Planar Inverted-F Antennas
(PIFA). 

Best regards,

Christine.