Hello,
sorry for the lot of text
I am thinking about a solution for locating people (me) in my house. The house will be newly built, i. e. provisioning for cabling etc. is easy.
I am open to any suggestions.
Basically I just want to know if someone is in a particular room of the house. The persons would also agree to carry around a small piece of electronics. Identifying them and having an accuracy of <1m would be fine.
My concept so far:
After googling I found that time-of-flight measurements appeal most to me. I would not have to synchronize clocks or anything.
Imagine I distribute small senders (for no better name) in every room. They are all connected to PC hardware.
Looking at a sender. This one sends out a short code (4-8bit) at some arbitrary carrier frequency (433MHz maybe). a Receiver (small object carried around) receives the signal and if the code matches its own it answers with a single pulse.
The sender counts the time-of-flight from sending the first/or last bit to the answer pulse.
Because of the short distances and the speed of the wave I have to count really fast like at GHz rate (1ns =0,3m). This seems to be the main challenge.
I am no electronics engineer but only a physicist so I dont know about parasitic capacities and such. Therefore sorry for wrong nomenclature. This is why I am asking about the feasibility of the approach.
My solution for a GHz single shot counter:
There are very fast comparators with a transition delay time of 700ps. I cascade 4 of them and feed back the Not Q output of the last with the first input over an and-gate. The other input is my start trigger. When it goes high, I logical high is propagated along the cascade when it reaches the end the Not Q will pull the input of the first comparator down and send a logical low through the cascade. If the trigger signal pulls the and-gate low the counter will reset the cascade to 0 (cascading).
The output of each comparator is put to an input of a 4bit D-Flipflop. At the stop trigger it will latch the state of the four outputs. This should produce an oddly coded 3bit counter with a takt rate of 1.428 GHz.
Additionally, the Q output of the last comparator goes into an 8bit synchronous counter. Its takt rate would be 1.428GHz / 8=178.5MHz.
How about that?
Now if I send out a datagram I trigger the start with it. Then I watch the answer signal intensity and if it goes ove a threshold I latch the cascade and stop the second stage counter.
I know there will be a lot of overhead time in comparision to the time-of-flight time. But this should be roughly constant.
If it works I get in the best case a distance measurement with a resolution of 10cm with range depending on how many counters I put in.
Do you think it could work? What other problem do arise?
Thank you for your processing time
MrSingingClub
sorry for the lot of text
I am thinking about a solution for locating people (me) in my house. The house will be newly built, i. e. provisioning for cabling etc. is easy.
I am open to any suggestions.
Basically I just want to know if someone is in a particular room of the house. The persons would also agree to carry around a small piece of electronics. Identifying them and having an accuracy of <1m would be fine.
My concept so far:
After googling I found that time-of-flight measurements appeal most to me. I would not have to synchronize clocks or anything.
Imagine I distribute small senders (for no better name) in every room. They are all connected to PC hardware.
Looking at a sender. This one sends out a short code (4-8bit) at some arbitrary carrier frequency (433MHz maybe). a Receiver (small object carried around) receives the signal and if the code matches its own it answers with a single pulse.
The sender counts the time-of-flight from sending the first/or last bit to the answer pulse.
Because of the short distances and the speed of the wave I have to count really fast like at GHz rate (1ns =0,3m). This seems to be the main challenge.
I am no electronics engineer but only a physicist so I dont know about parasitic capacities and such. Therefore sorry for wrong nomenclature. This is why I am asking about the feasibility of the approach.
My solution for a GHz single shot counter:
There are very fast comparators with a transition delay time of 700ps. I cascade 4 of them and feed back the Not Q output of the last with the first input over an and-gate. The other input is my start trigger. When it goes high, I logical high is propagated along the cascade when it reaches the end the Not Q will pull the input of the first comparator down and send a logical low through the cascade. If the trigger signal pulls the and-gate low the counter will reset the cascade to 0 (cascading).
The output of each comparator is put to an input of a 4bit D-Flipflop. At the stop trigger it will latch the state of the four outputs. This should produce an oddly coded 3bit counter with a takt rate of 1.428 GHz.
Additionally, the Q output of the last comparator goes into an 8bit synchronous counter. Its takt rate would be 1.428GHz / 8=178.5MHz.
How about that?
Now if I send out a datagram I trigger the start with it. Then I watch the answer signal intensity and if it goes ove a threshold I latch the cascade and stop the second stage counter.
I know there will be a lot of overhead time in comparision to the time-of-flight time. But this should be roughly constant.
If it works I get in the best case a distance measurement with a resolution of 10cm with range depending on how many counters I put in.
Do you think it could work? What other problem do arise?
Thank you for your processing time
MrSingingClub
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