need some basic understanding of Pulse duration Vs range

[gobiraj]

Hi All,

I want to get some useful basic understanding of following concept for location tracking of theft objects.
The transmitter is placed on the theft objects and it transmits the pulse signal after the certain period of time to be detected by the receiver.

1) SO how transmitting pulse duration effect the battery power consumption and the range of the transmitting power?

2) Any other wake up transmitter suggestion to reduce the battery power of the transmitter (need some basic concept)

3) main scope is to reduce the battery consumption for a long life , so if any has got any other idea appart from above two , please suggest me

Thanks
Raj

 

[Genovator]

I think you can use CC1101 transceiver for half duplex communication between the theft object & the tracker. The benefit is that this chip contains RSSI (Receiver Signal Strength Indicator). By reading its value, you can reduce both the transmitting power & pulse duration, say to 1dB & 5-10 sec respectively. If RSSI value is found low, you can increase the transmission power & duration as per your wish, say 10dB & 1sec. This way you can save a lot of battery life by avoiding unnecessary transmission power output.
RSSI will increase & decrease with its proximity..

 

[gobiraj]

Hi

Thanks for your reply.

I need to find the solution to reduce the transmitter power consumption which will be in maximum of 20km range. please clarify me following doubts.

1) how pulse width and duration of the transmitter effect the range and battery consumption

2) If wake up transmitter is used how we can reduce the power consumption of the transmitter in terms of range and pulse duration.

Thanks

 

[Genovator]

The pulse width & duration can be optimized for lesser power consumption. Lets take an example of CC1101 running with CR2032 battery. At 315MHz & +10dBm power output, it consumes approximately 27mA of current at 3V. Battery capacity is around 240mAh. Then,

240mAh / 27mA = 8.88h of constant run time.

So if your transmission duty cycle is 1%, that is 10ms ON time, total no. of time it will run

8.88h / 10ms
= 31968000ms / 10ms

= 31,96,800 times.

Since duration is of 1sec, total run time is around 888hrs or around 37 days.

Calculation may have mistake, but it is sure you will get a long battery life if you choose correct transmitter, battery & best optimization.
Since 20km transmission takes huge power, you have to decrease pulse width & pulse duration.

And could you elaborate what you mean by wake up transmitter concept??? How you want it should work??

 

[gobiraj]

Hi

Thanks for your brief reply.

actually wake up transmitter and receiver should be placed into the theft object. So to chase the theft object , primary detector ( which also have both transmitter and receiver) will send the detection signal to get the response from the theft object.

So by using wake_up_call signal we can allow system into sleep mode until it gets activated by detector.

So I am more concerned about the battery life of device of theft object.

Thanks
Raj

 

[Genovator]

Ya. That's a good idea... If you make the transmitter of theft object to transmit signal only when you need, you can avoid any regular & continuous duration and can save a lot of power. While transceivers are in receiving mode, they consume power in negligible amount.

In the theft object, battery duration will depend on battery & circuitry. Points of saving power are,
1. Determine the time the transmitter should be active long enough so you can reach to your theft object.
2. Use small but high capacity battery
3. Use smallest possible circuit, mostly some on-chip radios
4. Keep the transceiver of theft object always in idle mode or receiving mode, and only transmit when you send a signal.
5. Use lowest voltage possible
6. Use the on-chip facilities like 'wake-up on signal reception', 'RSSI', 'low power output depending on RSSI', etc. to save maximum power.
7. Use lower frequency

No mater if any object is stolen, you will have a window of 1 or 2 days maximum to grab the thief. Within this time, the thief will come to know there's a transmitter. But if its a car, there's nothing to worry.;-) And you can hook it up with the car battery.

 

[gobiraj]

Hi Genovator,

Thanks for your reply.

I am trying to find the transceiver with the spec as you have mentioned. But I need to go for lower power consumption with the range of 20 KM.

So how would I calculate the mAh of the device and the range from their specification details. Please suggest one transceiver and teach me what to look for calculating mAh and the range of the transceiver.

Thanks
Raj

 

[Genovator]

I don't think any single chip rf transceiver is capable of 20km of signal coverage. So you need power amplifiers to increase the output. The only single chip solution I found till now is RA07M4047M amplifier. I have never configured these ic's by myself. I always did the theory part.

To calculate the power consumption, just check it's datasheet. Match the parameters of operating voltage, current drawn at given power output & frequency with your desired condition. Select a right battery and check in google for its mAh and you can easily calculate how long it is going to work. You may also need to add a microcontroller to control these ic's properly. So consider its power consumption also. Range calculation is never possible to accurate figure because it vastly depends on obstacles between line of sight, power output, signal deviation, noise, receiver sensitivity, and lots of other factors which even I don't know properly. About the transceiver I showed above, I can only guess you need around 5 watt or more to achieve this range. This is even illegal in our country. Indian telecom norms allows only upto 1 watt of transmission in ISM bands only.