kiewirevo, you may want to rethink your project.. RF triangulation is probably one of the most complex subjects from both a digital and analog perspective that you can tinker around with. It generally takes equipment costing multiple tens of thousands of dollars to do what you're wanting to do, unless you can more specifically narrow the frequencies you're interested in, the distances you're interested in, and specify the accuracy with real numbers there's no way to respond properly to your post.
It might be easier to start with your original suggestion, which is to receive signals from wireless routers and such kinds of devices. The reason for this is that it is easier to make an antenna with narrow directivity at higher frequencies. However, this is still a very challenging project.
One way to build the receiver is to use an evaluation board for a Logarithmic Detector IC. These ICs are made by companies like Analog Devices and Linear Technology. An evaluation board is better than starting with the bare IC because it is too difficult for the beginner to get the IC to work on his own. Many log detectors are broadband, so for receiving signals from specific devices you would have to put a band pass filter between the antenna and the log detector, a filter that is chosen for the devices you want to receive. For example, most WiFi devices operate in the 2.4 GHz band, so a band pass filter at 2.4 GHz would be appropriate for these. Cell phones operate in several bands including 1750 to 2000 Mhz, 825 to 960 Mhz for examples. Filters are available for all these bands.
It is possible to buy band pass filters in the form of a small circuit board with a surface mount filter soldered on the board and two RF connectors.
In order to build an antenna with a narrow beamwidth, such as you imagine, you will probably have to make something special. To start with, there are many antenna designs described on the web for 2.4 GHz Can antennas and this would be a good starting point.
You are not making a radar. It uses reflected radio energy. You are trying to make a radio transmitter direction finder.
The lousy old LM324 quad opamp has trouble with frequencies above only 2kHz (2000 Hz). Most other opamps work well up to 100kHz.
Maybe if you amplitude-modulate the carrier with a low audio frequency then an LM324 opamp can detect the strength of the detected audio signal.
But your carrier frequency is so low that a directional antenna must be huge!
Have you seen a TV antenna up close? It is directional. It is pretty big. Its lowest frequency is (was) 55MHz in North America.
Detect things? Do you want to transmit (emit) a radio signal then receive its reflection from something nearby? But many things do not reflect a radio signal. The receiver must be turned off during transmit then it must turn on extremely quickly because radio travels at the speed of light. The time taken by the reflection is the distance. But the time is very close to zero.
There are many other problems you have not thought about (a screen showing location and distance of objects?).
Maybe you want to make a spectrum analyser? Look at it in Google.i just want to "recieve" signals.... just pointers on how i can make an reciever circuit or bandpass filters.
....id like to know how i can make a good bandpass filter and what components are recomended to make it and what do i need to make a antenna and what kind of things do i have to use.
Maybe you want to make a spectrum analyser? Look at it in Google.
A spectrum analyser shows on a display many radio frequencies that it receives. It can use a directional antenna or an antenna that picks up signals all around. It is a very complicated circuit. It does not show direction nor distance. Like all radios it has many bandpass filters. It will show the radio frequency used by an old cell phone (new cell phones use many frequencies at the same time), a wireless mouse or a wireless router.
Here is a photo of the display of a spectrum analyser showing many radio frequencies with decreasing amplitudes and the same frequency spacing.
Maybe you want to make a spectrum analyser? Look at it in Google.
A spectrum analyser shows on a display many radio frequencies that it receives. It can use a directional antenna or an antenna that picks up signals all around. It is a very complicated circuit. It does not show direction nor distance. Like all radios it has many bandpass filters. It will show the radio frequency used by an old cell phone (new cell phones use many frequencies at the same time), a wireless mouse or a wireless router.
Here is a photo of the display of a spectrum analyser showing many radio frequencies with decreasing amplitudes and the same frequency spacing.
You can measure distance using an SA if you know what the transmitted power is at what range and how much the signal deteriorates on it's way to the analyser. This would be impracticle for short distance measuerments becuase the the detector would have to be extremely sensitive to changes in frequency or amplitude. For a much longer range it can be done, but it won't be easy.
If memory serves, the eirlier forms of radar used a form of spectrum analysing to approximate a distance to the target but weren't able to get a target size. Speed and altitude were calculated by measuring the changes in signal levels as the target moved.
You are confusing "frequency" with "detected signal strength".hmm well i dont want distance nor height i just want to pick up the signal in 1 direction so i can map it in a graphic interface... i think that if i make a circuit that converts frecuency to dc current i can give it a "kind of proximity sense" to it... like when the circuit returns me 5V ill make the dot appear very close to the center of the map and when it returns 1v ill make it appear a little farther. get my point?.
also the measuring i want isnt changes its just a determinate set of frecuencies like 780MHZ to 820MHZ and so on...
It is Spectrum Analyser. I showed its display and I said to look at it in Google.i dont know what an "SA"
You are confusing "frequency" with "detected signal strength".
You are also confusing "transmitted power" with "detected signal strength".
It is Spectrum Analyser. I showed its display and I said to look at it in Google.
i just want to pick up the signal in 1 direction so i can map it in a graphic interface... i think that if i make a circuit that converts frecuency to dc current i can give it a "kind of proximity sense" to it... like when the circuit returns me 5V ill make the dot appear very close to the center of the map and when it returns 1v ill make it appear a little farther. get my point?.
Yes we understand what you want to do, but you have to understand that it doesnt work that way.
A given signal strength and therefore output voltage level from the receiver detector cannot be directly related to the distance of the transmitter from you. Why you ask? ...
say you got a 2Volt output from the receiver ....it could be a weak signal very close or a strong signal a long way away... you would have absolutely no way on knowing which it was. So what you plotted on the screen would be meaningless.
the complexities of what you are trying to achieve would appear to be far in advanced of your apparent knowledge of even basic radio receivers and how they work.
cheers
Dave
VK2TDN
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