audioguru2
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oh! I thought u were referencing photo diode....the mixer not present in our circuit(laser)???? How can that RF modulated frequency be determined in the ladar?By now what I've learnt is that the rf frequency should be known.....I can't see without that how one can proceed ...... RF modulated...Frequency Modulated ..I think?
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audioguru2
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Our Laser Speedometer project has two oscillators:
1) A high radio frequency oscillator that pulses the laser at maybe 100MHz.
2) A medium radio frequency oscillator that gates the received pulses that might be doppler shifted in rate. The pulses are gated into the counter for a time period determined by the lower frequency oscillator.
1) A high radio frequency oscillator that pulses the laser at maybe 100MHz.
2) A medium radio frequency oscillator that gates the received pulses that might be doppler shifted in rate. The pulses are gated into the counter for a time period determined by the lower frequency oscillator.
The signal entering in the ramsey display schematic(low pass filter) is the doppler shift? which is, for 2.6 GHz case, 7.76Hz for each mi/hr.....So,the crkt may be designed for 7.6Hz.....
Can we FM modulate the laser beam?how? at 2.6GHz?
If we fm modulate it and after the signal is received ......we pass both the signals(transmitted and reflected) in a mixer and gets their difference, the doppler shift and if we have 2.6GHz transmitted signal ,then we only have to connect the transmitter and receiver+mixer part to the ramsey
Can we FM modulate the laser beam?how? at 2.6GHz?
If we fm modulate it and after the signal is received ......we pass both the signals(transmitted and reflected) in a mixer and gets their difference, the doppler shift and if we have 2.6GHz transmitted signal ,then we only have to connect the transmitter and receiver+mixer part to the ramsey
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audioguru2
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No. Then its max speed detection is a snail's pace. Its filter cuts noise above about 760Hz (for 100mph) or a little higher.MNA said:
Cell phones FM modulate 2.6GHz but FM and 2.6GHz are useless in a laser speedometer.
The 2nd oscillator in our project is at a lower frequency than the pulsing modulation oscillator and drives a logic gate in the counter circuit. A logic gate has an input for pulses and another input to allow or not allow it to pass the pulses. Then the counter counts and displays how many pulses passed in the time allowed by the 2nd oscillator's time period. If an object is moving toward the receiver then maybe the doppler shift causes the received pulses of light to be at a higher rate than the transmitted rate.
audioguru2
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I don't think our laser speedometer circuit has a mixer. It has a gated counter instead.
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What's the purpose of this(see labeled block)?
I m unable to find a good detail on ladars in google......Have u any? there are many about radars but none explaining the steps of ladar.....
You say that there is no mixer in our ladar......then It is not using the doppler shift????? Since the mixer will give us the doppler shift......
Are ladars absolutely different from radars?
Still I don't get how to determine the transmitted frequency in ladars.......
This seems to me giving no results :'(
View attachment 39086
I m unable to find a good detail on ladars in google......Have u any? there are many about radars but none explaining the steps of ladar.....
You say that there is no mixer in our ladar......then It is not using the doppler shift????? Since the mixer will give us the doppler shift......
Are ladars absolutely different from radars?
Still I don't get how to determine the transmitted frequency in ladars.......
This seems to me giving no results :'(
View attachment 39086
audioguru2
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I've never seen a radar or laser speedometer circuit before. I am not sure what the Photodiode Circuit does, maybe a very short pulse generator.
The same author has about the same circuit using the same ICs in another project of his and he doesn't describe it either: http://www.electronics-lab.com/projects/pc/023/index.html
The same author has about the same circuit using the same ICs in another project of his and he doesn't describe it either: http://www.electronics-lab.com/projects/pc/023/index.html
audioguru2
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Our laser speedometer circuit doesn't have a mixer because light frequency is too high for an electronic mixer circuit. Radar uses radio waves and has an electronic mixer diode.
Our laser speedometer circuit counts the frequency of the modulation of the reflected laser beam. I assume that the doppler frequency shift also occurs to the modulation frequency.
The RING pin on the jack is from the output of the mixer and it is going to the input of the lowpass filter in the amplifier circuit.
Our laser speedometer circuit counts the frequency of the modulation of the reflected laser beam. I assume that the doppler frequency shift also occurs to the modulation frequency.
The RING pin on the jack is from the output of the mixer and it is going to the input of the lowpass filter in the amplifier circuit.
yeah,Acc to my knowledge,doppler shift occurs to the modulation frequency......But how is it useful......Just leave the crkt at electronics-lab and tell me that how he counting of the received signal with doppler shift can be useful?How can it be converted to speed?Just ideas not referencing the ladar crkt if it is wrong.....audioguru said:
yes,that's what I was saying about the ring pin:-
The signal entering in the ramsey display schematic(low pass filter) is the doppler shift? which is, for 2.6 GHz case, 7.76Hz for each mi/hr.....So,the crkt may be designed for 7.76Hz(or it's multiples to masure the speed like this 7.76*10=77.6 which means 10 Miles/hr)?????.....
audioguru2
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Our Laser Speedometer project doesn't have an accurate quartz crystal nor a calibration pot so I guess it works by majic!
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How do radar guns work?
Radar guns utilize the "Doppler principle" to determine speed.
They transmit radio waves at microwave frequencies, and when these waves strike a moving object, they are reflected back to the radar gun at a slightly different frequency. The gun then "mixes" the reflected signal with the transmitted signal, and ends up with a frequency that represents the difference between the two. Since the difference in frequency is generally a number of hertz or kilohertz, it is in the audible range, hence the term "Doppler tone". The speed of the moving object can be derived by performing a calculation using the frequency of this Doppler tone and the original transmit frequency.
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How do laser guns work?
"Laser guns do not use the Doppler principle" like radar guns do. Instead, they use "time difference of arrival". The laser gun sends out a pulse, and calculates the "time of flight" for the pulse to be reflected back to the laser gun. Since the speed of light is a known value, the distance between the laser gun and it's target can be calculated by the time of flight. The laser gun takes multiple distance measurements, and by comparing the different distance measurements over time, it can determine the speed of the target.
What are FMCW and AMCW trying to do here
http://www.swedetrack.com/obstact.htm#4
?
How do radar guns work?
Radar guns utilize the "Doppler principle" to determine speed.
They transmit radio waves at microwave frequencies, and when these waves strike a moving object, they are reflected back to the radar gun at a slightly different frequency. The gun then "mixes" the reflected signal with the transmitted signal, and ends up with a frequency that represents the difference between the two. Since the difference in frequency is generally a number of hertz or kilohertz, it is in the audible range, hence the term "Doppler tone". The speed of the moving object can be derived by performing a calculation using the frequency of this Doppler tone and the original transmit frequency.
--------------------------------------------------------------------------------
How do laser guns work?
"Laser guns do not use the Doppler principle" like radar guns do. Instead, they use "time difference of arrival". The laser gun sends out a pulse, and calculates the "time of flight" for the pulse to be reflected back to the laser gun. Since the speed of light is a known value, the distance between the laser gun and it's target can be calculated by the time of flight. The laser gun takes multiple distance measurements, and by comparing the different distance measurements over time, it can determine the speed of the target.
What are FMCW and AMCW trying to do here
http://www.swedetrack.com/obstact.htm#4
?
hazanohazizul
- May 22, 2006
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i think it not work by magic. Ok, this radar works with the doppler effect. It converts variation of frequency into frequency and it measures this frequency to display the speed. The variation of the frequency of the modulation is created by the impact of vehicle against the wave. More the speed of the vehicle is high, more the variation of the frequency will be high. At the speed of the light, the rythm of variation of frequency is the same as the modulated frequency. You can determine the output frequency if you know the modulated frequency value and speed of the car.audioguru said:
the 74as series can be replaced with the 74hc but from what i know the 74hc is a CMOS type, is there 74hc in TTL type?
i want to ask something? what is the major different between TTL and CMOS IC, the different that we can see from the IC... exactly like it shape or marking?
I hope you can help me...
hazanohazizul
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the 74as series can be replaced with the 74hc but from what i know the 74hc is a CMOS type, is there 74hc in TTL type?
i want to ask something? what is the major different between TTL and CMOS IC, the different that we can see from the IC... exactly like it shape or marking?
I hope you can help me...
???
i want to ask something? what is the major different between TTL and CMOS IC, the different that we can see from the IC... exactly like it shape or marking?
I hope you can help me...
???
audioguru2
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The AS and HC ICs are in the same case.hazanohazizul said:
The AS is much faster and operates at a much higher frequency than the HC.
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