stanleymyc

hi to all:
i am doing my final year project

its regarding RF signal transmission on object speed detection:

first, we generate RF frequency from a transmitter.
n then we try to move a object within the area-affected of RF frequency

then a receiver will receive the changing frequency cause by object and
receive by reciever.

a pic microcontoller will do the comparison b4 and after the changing frequency. by using doppler theorem we can know the speedof the object

however, now my problem is the RF signal frequency generated is only up to hundreds megahertz, which is ezily affected by outside noise and unused signal. how can i prevent the noise from receiving by my receiver?

my supervisor proposed generatesn the frequency hertz up to gigahertz
but he say this is imposible since we cannot afford good machine. is thr any other way?i am thinking to amplify the generated RF signal frequency?
is this posible?if yes whr can i find the circuit? or if thr any way to filter the outside noise?

vaineo

I don't know if it helps, but i think with a frequency in the gigahertz you need to use a waveguide. was just looking at this site and it has a chart giving the frequency range and the inner dimensions you would need. http://www.microwaves101.com/encyclopedia/waveguide.cfm

TillEulenspiegel

Must You use RF for the ranger? Why not laser ? If you must use RF a good trick is to modulate the signal, in fact that works for IR.sound , laser and RF freqs to boot.Another good schema ( prolly to much work for your design ) is spread spectrum. Aka freq hopping.