The Near Field Electromagnetic Ranging System

[Harros]

Hi, I was amazed with NFER technology when I was trying to get some idea of the location position system to be implemented in my project. But I dont know how to get the project of building this system started. Is there anybody here learned about this system? Hopefully you guys can provide me some of the details of this system and the practical circuit implementation of this system... Thank you!!!

 

[Super_voip]

try Wikki, are you trying to use fixed transmitters for the loacation. As I don't have any idea what your project is, there is wifi location software around and this may be more practical.

 

[Harros]

Hi Super_voip:

Yes, I am planning to build a fixed transmitter for the positioning purpose. After searching on the net for days, I have had some ideas of the functional blocks of the NFR system.

The system build is almost similar to the common RF communication system: Where the system consists of a transmitter and a receiver. The transmitter transmit the unmodulated sin wave to be received by the receiver. Its ok for me to build the transmitter, but its quite hard for me to build a receiver as I am not a RF guy ^^. The receiver shall consist of a pre-select filter, RF amplifier, IF filter, and eventually the phase detector (used to determine the relative phase difference of the E-field wave and H-field wave by determining the difference of zero-crossing time for both the wave). Any suggestions on the RF chip that i can use for the RF amplifier, IF filter, and zero-crossing time detection? Thank you!!!

P/S: All recommendations from any other members are appreciated!!!

 

[k7elp60]

What is the transmit frequency?

 

[Harros]

I am thinking of making the transmitter to transmit at 1 MHz. Is it possible to make a transmitting antenna for such a low frequency?

 

[Nigel Goodwin]

I am thinking of making the transmitter to transmit at 1 MHz. Is it possible to make a transmitting antenna for such a low frequency?

Yes, how do you think MW radio transmitters work?.

 

[quixotron]

I'm not sure I follow mate.

Are you trying to measure the near field radiaton pattern of your antenna/source device? Does this concern EMC or antenna issues?

Some more info would be nice. I have done some work with target locating and tracking for a senior deisgn project-is this similar?

 

[k7elp60]

I am thinking of making the transmitter to transmit at 1 MHz. Is it possible to make a transmitting antenna for such a low frequency?

Thats just about the middle of US AM broadcast band. Receivers shouldn't be a problem. A 1/4 wave antenna would be physically about 250 feet long, but there are ways to make a physically shorter antenna resonate.
Many standard broadcast receivers in USA us ferrite core loop antenna's that are only several inches long.

 

[Harros]

Yes, how do you think MW radio transmitters work?.

The transmitter is just to transmit a simple sine wave (No modulation) at 1 MHz for a distance of around 100 Meter (maximally). Is it possible to build such a transmitter circuit?

 

[Harros]

I'm not sure I follow mate.

Are you trying to measure the near field radiaton pattern of your antenna/source device? Does this concern EMC or antenna issues?

Some more info would be nice. I have done some work with target locating and tracking for a senior deisgn project-is this similar?

By the way, I am going to measure the phase difference of the E-field and H-field wave received by the receiver by detecting the zero-crossing time difference of both of the E-field wave and H-field wave. The antenna would be issue because of its size... Do you have any suggestions of the type of the antenna that i should use for the transmitter? In fact, I want to make the transmitter to be portable... Thank you.

P/S: For the frequency of 1 MHz, the system shall be able to measure the distance within 15 Meter to 130 Meter with the error of 30 Centimeter or fewer (Depends on the type of zero-crossing time detector used), so, I think the antenna gain will be another concern... Am I right?

P/S: There are some documentations regarding this distance measuring technology that you can look into for detailed information:
**broken link removed**
**broken link removed**

 

[Harros]

Thats just about the middle of US AM broadcast band. Receivers shouldn't be a problem. A 1/4 wave antenna would be physically about 250 feet long, but there are ways to make a physically shorter antenna resonate.
Many standard broadcast receivers in USA us ferrite core loop antenna's that are only several inches long.

How about the transmitter antenna?

 

[Nigel Goodwin]

How about the transmitter antenna?

Huge great piece of wire as high as possible!.

But you could use a ferrite rod for it's small size.

 

[Harros]

Huge great piece of wire as high as possible!.

But you could use a ferrite rod for it's small size.

Do you mean the multi-turn loop antenna with the ferrite rod? Is there a formula for the number of turn of the loop antenna that i should refer to?

 

[Nigel Goodwin]

Do you mean the multi-turn loop antenna with the ferrite rod? Is there a formula for the number of turn of the loop antenna that i should refer to?

Yes, but I couldn't tell you what it is - nick one out of an old radio, it will have a suitable coil already.

 

[k7elp60]

Yes, but I couldn't tell you what it is - nick one out of an old radio, it will have a suitable coil already.

I was going to suggest that. With you power level of about 100mW it shouldn't be a problem. With a ferrite core too much current in the loop can cause the core to saturate, but as I stated the power level shouldn't be a problem.

 

[Harros]

Is there any one here having the circuit for fast sine wave generator? There is problem with mine one, the output drags.....

 

[Super_voip]

options

for the antenna have a look at cross field antennas or CFA, the osc needs to be reasonably stable so maybe a crystal and something like a MAR6(showing my age)

 

[Harros]

for the antenna have a look at cross field antennas or CFA, the osc needs to be reasonably stable so maybe a crystal and something like a MAR6(showing my age)

Wow, the CFA is so big in size... Is there any antenna in around 30 or 40 cm sized?