Re: [time-nuts] question for expert time guys
On Mon, Feb 4, 2013 at 9:17 PM, Hal Murray hmur...@megapathdsl.net wrote: Can you re-transmit on a nearby frequency without blasting the receiver off the air? No not if it is in the same band, filters are never that good. I thought the OP had several bands available. So if this all needs to happen at one RF frequency the transmitter needs to act like a radar and send out modulated pulses. The oscilator that does the modulation (sawtooth?) needs to run continuously. so that the phase of the returned signal can be compared.If you don't know the range you need a conservative pulse repetition frequency (PRF in Radar speak) then once you find the range you can use a faster one to collect better data if you need to. The fester PRF transmits on average more energy so you get better data The advantage is that all the smarts is in just one place, all the other units are simply a mirror with gain or bent pipe. The next level of sophistication is to scan the antenna and note the azimuth position when the signal is maximum. Then you have both range and diction. No need to triangulate. Radars sound expensive but go to any small boat marina and you see that even small boats have them. The newels units integate with GPS and the boats auto pilot and still prices at retail level are under $2K for entry level systems. All that said, why not simply use GPS? Your mobile unit can have a GPS receiver and transmit is location. This works ten times better and cost a lot less. The cell phone industry gave up on triangulation when GPS because cheap and easy -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Think OP has the Choice of 3 bands Sent from my iPhone On Feb 5, 2013, at 12:32 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Mon, Feb 4, 2013 at 9:17 PM, Hal Murray hmur...@megapathdsl.net wrote: Can you re-transmit on a nearby frequency without blasting the receiver off the air? No not if it is in the same band, filters are never that good. I thought the OP had several bands available. So if this all needs to happen at one RF frequency the transmitter needs to act like a radar and send out modulated pulses. The oscilator that does the modulation (sawtooth?) needs to run continuously. so that the phase of the returned signal can be compared.If you don't know the range you need a conservative pulse repetition frequency (PRF in Radar speak) then once you find the range you can use a faster one to collect better data if you need to. The fester PRF transmits on average more energy so you get better data The advantage is that all the smarts is in just one place, all the other units are simply a mirror with gain or bent pipe. The next level of sophistication is to scan the antenna and note the azimuth position when the signal is maximum. Then you have both range and diction. No need to triangulate. Radars sound expensive but go to any small boat marina and you see that even small boats have them. The newels units integate with GPS and the boats auto pilot and still prices at retail level are under $2K for entry level systems. All that said, why not simply use GPS? Your mobile unit can have a GPS receiver and transmit is location. This works ten times better and cost a lot less. The cell phone industry gave up on triangulation when GPS because cheap and easy -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
About this subject, are you concerned with multipath? The signal from two of the basestations might arrive over a line-of-sight path whereas for the third basestation the signal might bounce around before arriving... JP - To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. -- Integrity is a binary state - either you have it or you don’t. - John Doerr ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Yes, we would need to address that as best we can. I thought of using two different frequencies to combat that to provide additional data. There is also the aspect that the mobile device is not expected to move too fast so if we see a big change we look at it with suspicion. Most likely one distance would be way off from the other two. The accuracy of 3 feet over 150 or 200 feet too should also allow for some error. But I'm not the expert here. Rick On Mon, Feb 4, 2013 at 11:35 AM, James Peroulas ja...@peroulas.com wrote: About this subject, are you concerned with multipath? The signal from two of the basestations might arrive over a line-of-sight path whereas for the third basestation the signal might bounce around before arriving... JP - To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. -- Integrity is a binary state - either you have it or you don’t. - John Doerr ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
I think for best timing rather then use a ping Where the device gets a signal, waits then sends a reply it would be better to re-transmit the signal in real time. So the base station send some waveform like carrier that is modulated by a saw tooth wave. The remote device simply re-transmits the sawtooth wave but on a different carrier frequency. Then the base station looks at the phase difference in the transmitted vs. received saw tooth.You can get even more fancy and make the sawtooth something more complex such as random digital data and use an auto correlation filter to find the delay. but phase works if you select the signal such that there are no range ambiguities (in other words such that phase is never over 360 degrees) You can even start with a long period (none ambiguous) saw tooth then when you know the approximate range more to a shorter period. You can think of better waveforms, like FM modulation or a block of digital data. This works because (1) Each cycle of the saw tooth is the same as your ping and you can average many thousands of them and (2) There is zero turn around at the remote end. It is just a bent pipe and you don't need a computer. The bent pipe is low cost. Only one site needs to be expensive that others just analog reflectors In fact people have use corner cube reflectors for range measurement. Basically to hit the reflector with a radar. If you want low cost I can't think of anything cheaper than a few sheets of aluminum. My sugestion about was actually an active reflector or transponder. It can make the radar cheaper because less power is required. ANd you don't need to turn off the transmitter to receive. If you are limited to milliwatts, you will need the active transponder. In short, think of this as a kind a radar and it becomes a lot less complex and it can even be 100% analog with a UV meter use to display the range (or phase of received signal) On Mon, Feb 4, 2013 at 9:35 AM, James Peroulas ja...@peroulas.com wrote: About this subject, are you concerned with multipath? The signal from two of the basestations might arrive over a line-of-sight path whereas for the third basestation the signal might bounce around before arriving... JP - To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. -- Integrity is a binary state - either you have it or you don’t. - John Doerr ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
albertson.ch...@gmail.com said: I think for best timing rather then use a ping Where the device gets a signal, waits then sends a reply it would be better to re-transmit the signal in real time. So the base station send some waveform like carrier that is modulated by a saw tooth wave. The remote device simply re-transmits the sawtooth wave but on a different carrier frequency. Then the base station looks at the phase difference in the transmitted vs. received saw tooth.... The OP said cost was important and that he was a software geek rather than a RF geek. Can you re-transmit on a nearby frequency without blasting the receiver off the air? There are low cost chips that send digital (RS-232 bandwidth) signals over ISM bands. Are there similar chips that send an analog signal such that phase would be a sensible term? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
rickhar...@gmail.com said: I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. I'd like a range of 150 feet or better and accuracy of 3 feet or better. I know the time accuracy is the key to count time = feet, 1ns. How to make it inexpensive is key. how inexpensive, very ;-) I think it's going to be tough to do it at low cost. The low cost transmit/receive chip sets you can get for 915 MHz are low bandwidth. That will turn into noise on the on/off transition that you need for timing. I'd suggest getting a pair of demo boards and running some experiments. The first simple sanity check would be to wire them up to a couple of uProcs and send messages and see if they work at your required range. Play around to learn the error rate vs baud rate. -device response ASAP on different frequency Not with low cost. But you don't need to use a second frequency. My straw man would be something like this: Only one station transmits at a time. Wire up the transmit and receive lines to counter/timers. On both the transmit and recv side, grab the time on each data-level change and average them to figure out when the packet started. Look at the NTP protocol. It collects 4 time stamps. From that, you can compute the time of flight. The time at the remote server drops out. The sequence would be something like this: fixed-remote: long timing packet. (with lots of 1/0 transitions to feed data to the timer hardware) remote-fixed: long timing packet. remote- fixed: packet with 2 time stamps first from the receive side, second from the transmit side I'd put a CRC on the packets as a sanity check. Handwave time: Assume the counter/timers run at 100 MHz. That's 10 ns. So you'll have to do lots of averaging to get below 3 ns. But that's assuming the RF units work well and that the averaging works. You could build a (much) faster counter/timer in a FPGA. I'm not sure that will help. Get a pair (or 2 pairs) of units and see how well they work. I'd expect FSK to work slightly better than ASK (on/off), but I'm not enough of an RF geek to turn than into numbers. I'll say more if that will help. We should probably take it off list. One probably crazy idea... Setup a directional antenna with a motor to aim it. Scan for the best signal. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
and even a more crazy idea: use a phasing array for the directional antenna. On Fri, Feb 1, 2013 at 10:45 AM, Hal Murray hmur...@megapathdsl.net wrote: rickhar...@gmail.com said: I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. I'd like a range of 150 feet or better and accuracy of 3 feet or better. I know the time accuracy is the key to count time = feet, 1ns. How to make it inexpensive is key. how inexpensive, very ;-) I think it's going to be tough to do it at low cost. The low cost transmit/receive chip sets you can get for 915 MHz are low bandwidth. That will turn into noise on the on/off transition that you need for timing. I'd suggest getting a pair of demo boards and running some experiments. The first simple sanity check would be to wire them up to a couple of uProcs and send messages and see if they work at your required range. Play around to learn the error rate vs baud rate. -device response ASAP on different frequency Not with low cost. But you don't need to use a second frequency. My straw man would be something like this: Only one station transmits at a time. Wire up the transmit and receive lines to counter/timers. On both the transmit and recv side, grab the time on each data-level change and average them to figure out when the packet started. Look at the NTP protocol. It collects 4 time stamps. From that, you can compute the time of flight. The time at the remote server drops out. The sequence would be something like this: fixed-remote: long timing packet. (with lots of 1/0 transitions to feed data to the timer hardware) remote-fixed: long timing packet. remote- fixed: packet with 2 time stamps first from the receive side, second from the transmit side I'd put a CRC on the packets as a sanity check. Handwave time: Assume the counter/timers run at 100 MHz. That's 10 ns. So you'll have to do lots of averaging to get below 3 ns. But that's assuming the RF units work well and that the averaging works. You could build a (much) faster counter/timer in a FPGA. I'm not sure that will help. Get a pair (or 2 pairs) of units and see how well they work. I'd expect FSK to work slightly better than ASK (on/off), but I'm not enough of an RF geek to turn than into numbers. I'll say more if that will help. We should probably take it off list. One probably crazy idea... Setup a directional antenna with a motor to aim it. Scan for the best signal. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Also the fixed stations can not have OCXO? On Fri, Feb 1, 2013 at 5:37 AM, Rick Harold rickhar...@gmail.com wrote: To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Hi Rick, You would do better putting a small GPS receiver in the mobile and transmit with a 2.4 GHz Blue tooth transmitter. The GPS devices can be gotten very small (your thumb would just about cover it up). They are also very light and draw very little power. That would save you two transmitting and receiving stations. Clearly the software would be infinitely easier as you would not need to deal with all the timing issues. GPS would provide the position information and its time count for each report, if that mattered. Some representative GPS receivers can be research at the following location: https://www.sparkfun.com/categories/4 They also have various transmitter devices for blue tooth, WIFI and Zigbee. You can view these under the following category: https://www.sparkfun.com/categories/16 This is only one place that provides such things for hobbyist. There are others, as well as, going direct to the manufacturers for such OEM products. I do not know if you are aware of it, but and finale product that transmits over the air may need FCC certification. Other sections might apply in certain circumstances. BillWB6BNQ Rick Harold wrote: To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Hi Rick, You would do better putting a small GPS receiver in the mobile and transmit with a 2.4 GHz Blue tooth transmitter. The GPS devices can be gotten very small (your thumb would just about cover it up). They are also very light and draw very little power. That would save you two transmitting and receiving stations. Clearly the software would be infinitely easier as you would not need to deal with all the timing issues. GPS would provide the position information and its time count for each report, if that mattered. Some representative GPS receivers can be research at the following location: https://www.sparkfun.com/categories/4 They also have various transmitter devices for blue tooth, WIFI and Zigbee. You can view these under the following category: https://www.sparkfun.com/categories/16 This is only one place that provides such things for hobbyist. There are others, as well as, going direct to the manufacturers for such OEM products. I do not know if you are aware of it, but and finale product that transmits over the air may need FCC certification. Other sections might apply in certain circumstances. BillWB6BNQ Rick Harold wrote: To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Can the base stations be interconnected via cable? In that case, wouldn't it suffice to have the mobile device send an unmodulated carrier of low enough frequency, and compare the phase between the receiving base stations, taking the (known) cable delays into account? Cheers Stefan Rick Harold wrote: To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
On 1/31/13 8:37 PM, Rick Harold wrote: To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. Don't do pinging and time of flight. Do phase measurements. At 900 MHz the wavelength is 33cm. Essentially rather than trying to ping, you're measuring the positions of multiple zero crossings averaged over some amount of time. Can your base stations be interconnected so they can share a common reference signal? What position accuracy do you need? How big an area? Can you initialize at a known position and then track, or do you need to come up cold? There's a lot of clever schemes that use multiple frequencies from a common source to disambiguate phase: e.g. if I measure phase at 908 MHz and phase at 928 MHz, I can effectively also measure phase as if I were radiating at 20 MHz, so that gives me coarse position (out of 15m wavelength) and fine position (out of 33cm wavelength) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
Just to make sure I understand the 'ground rules', the three base stations define a plane, unless they are on the same line. Is the mobile device also in this plane? How far apart are the base stations relative to the location of the mobile device? Or, better, is the mobile device 'inside' this triangle or 'outside'? How precisely can you know the location of the base stations without violating the 'inexpensive' rule? Can the base stations 'ping' each other? Seems to me that an accuracy to 3 feet is going to be a problem without precise time measurement unless you can use some 'known' reference (like the precise location of the base stations) and the ability to use that 'known' to 'calibrate' each measurement, thus minimizing the errors from 'drift', etc., in the available, 'inexpensive', time references. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rick Harold Sent: Thursday, January 31, 2013 10:37 PM To: time-nuts@febo.com Subject: [time-nuts] question for expert time guys To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys
On 2/1/2013 3:45 AM, Hal Murray wrote: rickhar...@gmail.com said: I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. I'd like a range of 150 feet or better and accuracy of 3 feet or better. Doing this on radio will be tough. You are likely to need on the order of 10 or 20 MHz of ranging bandwidth to get the accuracy you want. This is also overkill in the extreme. For this range an line of sight I'd do it acoustically. Get some piezoceramic transducers and do it at 40 KHz or so. Transducers are ~$6 in single quantities. http://www.mouser.com/ds/2/209/KT-400482-193462.pdf Time of flight is about 13.5 inches per *milli* second, so your microprocessor will have time to do it's nails after processing ranging data. You should also get good accuracy and resolution. In general you shouldn't need to if you are using active transmitters at both ends, but if you are worried about multipath reflection use a PN code and use the first correlation peak. Rich -- mailto:o...@ozindfw.net Oz, N1OZ POB 93167 Southlake, TX 76092 (Near DFW Airport) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] question for expert time guys (Hal Murray)
Hello Hal - I spent a lot of my RF engineering career in related areas, including radar, EW, and spread spectrum timing systems. Since the distance is short and the cost is an issue you may wish to consider an analog system solution. Specifically your master station transmits a RF signal that is FM modulated with a high frequency tone. The remote unit is a transponder. It receives the tone and re-transmits back on another frequency. Almost no parts required. At the master station the phases of the outgoing and returning tones are compared. The distance is directly proportional to the phase shift between the outgoing and incoming tones. For instance if the tone is 10 MHz the 360 degrees of phase is 100 nS which is about 100 ft round trip. The phase may be measured either analog and A/D converted or digitally and in either case is then easily converted to range by your processor. By adjusting the tone frequency you can set the full scale range. To increase resolution higher frequency tones may be used. To overcome ambiguity when the range goes beyond 360 degrees of phase, add a lower frequency tone to resolve the ambiguity. This scheme has been used in surveying instruments (the Teleurometer) and even an ill fated German bombing system in WWI. The latter proved delightfully easy to jam since the Brits had a spare TV transmitter in the correct band. Look up something like tone ranging. -john c roos k6iql -Original Message- From: time-nuts-request time-nuts-requ...@febo.com To: time-nuts time-nuts@febo.com Sent: Fri, Feb 1, 2013 4:24 am Subject: time-nuts Digest, Vol 103, Issue 2 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Loran again (Stan, W1LE) 2. question for expert time guys (Rick Harold) 3. Re: Low noise power supplies? (gary) 4. Re: Low noise power supplies? (John Miles) 5. Re: question for expert time guys (Hal Murray) 6. Re: question for expert time guys (Azelio Boriani) -- Message: 1 Date: Fri, 01 Feb 2013 00:30:40 -0500 From: Stan, W1LE stanw...@verizon.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Loran again Message-ID: 510b5300.8000...@verizon.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Fired up the SRS FS700 and auto found the GRI 89700 microsecond stations in Dana Il (master) and Seneca NY, (slave) both with equal signal strength of 63 db. Other slaves were not to be found. Noise margin of 32 dB and Rx gain of 72dB. So the Rx is all locked up. Tomorrow I will have more data comparing the 10 MHz from the T'Bolt. Right now they are comparing to within 10EE10. Stan, W1LE Cape Cod On 1/31/2013 10:44 PM, Stan, W1LE wrote: What GRI should we be listening for ? Stan, W1LECape Cod FN41sr On 1/31/2013 9:56 PM, paul swed wrote: Rich indeed its on the air. Warming up the FS700 to see if it will lock. Have a pattern ram thats getting flakey and takes about 30 minutes to warm up along with the oven. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Message: 2 Date: Thu, 31 Jan 2013 22:37:00 -0600 From: Rick Harold rickhar...@gmail.com To: time-nuts@febo.com Subject: [time-nuts] question for expert time guys Message-ID: CAODR2TDuMSpOr8JYvjMm-QRnRhM8sxYGkY=vrn6yttk5t3t...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3
Re: [time-nuts] question for expert time guys (Hal Murray)
Hi To complete the thought: Three base stations on three different transmit frequencies over a 50 MHz range. Mobile has a local oscillator at say 200 MHz. Filter the incoming frequency range, stuff it into a mixer, filter the output. What's transmitted back gets processed at the base station. Yes you would have to be running at a high enough frequency to keep everything in an appropriate band. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of johncr...@aol.com Sent: Friday, February 01, 2013 12:16 PM To: time-nuts@febo.com Subject: Re: [time-nuts] question for expert time guys (Hal Murray) Hello Hal - I spent a lot of my RF engineering career in related areas, including radar, EW, and spread spectrum timing systems. Since the distance is short and the cost is an issue you may wish to consider an analog system solution. Specifically your master station transmits a RF signal that is FM modulated with a high frequency tone. The remote unit is a transponder. It receives the tone and re-transmits back on another frequency. Almost no parts required. At the master station the phases of the outgoing and returning tones are compared. The distance is directly proportional to the phase shift between the outgoing and incoming tones. For instance if the tone is 10 MHz the 360 degrees of phase is 100 nS which is about 100 ft round trip. The phase may be measured either analog and A/D converted or digitally and in either case is then easily converted to range by your processor. By adjusting the tone frequency you can set the full scale range. To increase resolution higher frequency tones may be used. To overcome ambiguity when the range goes beyond 360 degrees of phase, add a lower frequency tone to resolve the ambiguity. This scheme has been used in surveying instruments (the Teleurometer) and even an ill fated German bombing system in WWI. The latter proved delightfully easy to jam since the Brits had a spare TV transmitter in the correct band. Look up something like tone ranging. -john c roos k6iql ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] question for expert time guys
To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
