transmit and receive tuning question 1

[mageta]

hi, i am building a transmitter and receiver using solenoids. there are two frequencies i am using, 2 mhz and 400 khz. the receiver has a photo-mosfet to select between two tuning circuits.

the receiver is parallel tuned to minimize energy loss in the tank circuit, which is ac coupled via passive high pass filter than to impedance buffer.

the transmitter is series tuned to maximaze current through put into the transmit solenoid. this way the series resistance should have no effect other than current limiting and controlling power output.

the question is whether this is a typical way to get maximum transmit power and maximum receive power? is there a better way to transmit and receive using solenoids as antennas?

 

[MacGyverS2000]

I have to ask... why would you use such an inefficient antenna design such as a solenoid?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[mageta]

because i cannot use any other. antenna type is not optional. that is what i have to work with.

 

[IRstuff]

Is this for school?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[mageta]

no. do you guys have any opinions on the way the tuning is being done???

 

[zappedagain]

I believe you are going to need to provide a bit more detail to get any useful answers. Are the frequencies stated your carrier frequencies or your data rates?

Posting a schematic of your circuit will be helpful.

Z

 

[mageta]

carrier frequencies, but they are pure sine waves. the transmitter is about 3 feet away. the desired receive power would be from 100mvpp to 1vpp when transmitting with about 50ma on transmit coil with similar characteristics of receive coils.

please have a look at the receiver side of things. thanks.

 

[IRstuff]

" power would be from 100mvpp to 1vpp "

You measure power in volts? If this is not schoolwork, you need to explain your project.

At this point in history, there's virtually no commercially practical reason to not use Bluetooth or Zigbee, both of which can span 3 ft, or even 30ft, distances with trivial ease, with substantially lower power, and do not require any tuning whatsoever, in additional to being already configured to send and receive a plethora of messages and protocols. You can buy USB Bluetooth transceivers for less than 1/20th the amount of engineering NRE consumed in this thread.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[VEBill]

Not to mention that the frequencies mentioned (2 MHz and 400 kHz) are unlikely to be in accordance with applicable regulations.

 

[mageta]

for the second time. nothing to do with school work! obviouslly it is a requirement of the desing to use the frequencids and antenna types (again not nagotiable). i am here because i don't have much of rf background. so if you don't know the answers or don't wish to help, don't bother.

thanks alot.

 

[MacGyverS2000]

We need to understand the application before we can offer appropriate advice... this is true for practically everything. I'm trying to understand why a solenoid coil would be used for anything other than as an electromagnet. The efficiency of such an antenna setup is pathetic, at best, and as mentioned by VE, you're not even close to Part 15 rules, so you have some serious FCC issues to worry about. Your use of volts as a transmit/receive power measurement tells us this is a complete hack, not a product design, and we're all going to wonder about wasting time on a design that doesn't make sense form the very beginning.

You can pony up some details and get useful advice, or you can toss a breadcrumb over the wall once in a while and get a breadcrumb back... your call.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Higgler]

You guys aren't very nice to a rookie. He said he's new to RF.

As an antenna engineer, most antennas are electrically large. For RFiD's they're so small you can communicate better with a transformer, such as your requirment, and maybe similar to an AM Radio antenna.

Here's a link that might help on RFiD antenna systems;

http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf

They use voltage primarily when discussing power transfer and they use coils for antennas. Hope you get it to work (google other RFiD info) and I hope this forum is nicer to the next rookie we encounter. After all, it takes the same amount of time to type kind words.

 

[mageta]

yes, the am radio analogy is dead on. and yes it is all about maximum power transfer with resonate circuits.