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Does the radar range depend upon the frequency of the signal transmitted?
Wiki User
∙ 12y ago
The difference in range by frequency of a radar, is minimal.
Radar range is more limited by the curvature of the earth. Different frequencies are of more use in discrimination of the returned signal.
3cm wavelength is popular on ships, as a good all round use. It can get blinded by rain and limited by fog. 10cm is also used and can see through heavy rain, the discrimination is poor however and objects close together can merge into one.
Wiki User
∙ 12y ago
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Why is reflection of signal useful?
Reflection of a transmitted signal is the basic premise of radar and sonar.
What are the parts of a Doppler Radar?
Same as the "regular" radar, except that the receiver is a bit different. In regular radar, the receiver looks for the returning signal on the frequency the transmitted pulse was sent out. Yes, it sees" Doppler shifted signals, but with decreasing sensitivity. And it does little with them but combine them with the signal on the frequency of the transmitted pulse. With Doppler radar, the receiver looks for a "band" or group of frequencies around the frequency at which the transmitted pulse was sent out. These "nearby" frequencies represent returns from materials or substances that are moving relative to the transmitter (toward or away from it). And the receiver works with a microprocessor based "analyzer" to paint a picture based on those returning signals that are near the frequency of the transmitted signal and not right on it. Basically, radar has a transmitter, the waveguide to the antenna, the antenna itself, and the receiver. The receiver is plumbed into the same waveguide the transmitter is connected to, but there is a junction (like a "T") where the transmitter and receiver are connected that is capable of directing the transmitted signal out along the waveguide and keeping it from going into the receiver, and then allowing the returned signal to get to the receiver without being "lost" by going back into the transmitter. There is a control system and a display system associated with the equipment as well. Just as one might expect.
How does the frequency of a car's returning radar signal chang if the car moves away from the you radar source?
It's frequency reduces as the car gets further away.
What type of radar is able to take advantage of vary small changes in the frequency of the returned signal to give a more detailed radar image?
Doppler radar is sensitive to the changes in frequency of the returned signal caused by the movement of the "target" off which that signal is being reflected. Storm cells are moving concentrations of extremely humid air, and they reflect radar signals fairly well. By using a computer to analyze the small changes in the frequency of the returned signal (compared to the frequency of the transmitted signal - which we know), we can, by looking at this Doppler shift, paint a picture of the storm cell activity. A link is provided to the Wikipedia article on Doppler radar. You can get more detailed information there. The above is correct but is worth noting the following too: Doppler RADAR will be able to detect Doppler shift, but the fidelity to which they detectable or are know to is a function of the Pulse Repetition Ration (PRF) and the number of sample collected. So it depend what frequency you are looking and the fidelity you are looking for. Also note that Doppler is a function of the Carrier Frequency not the pulse modulation, and it should be noted that that some carrier frequencies are more susceptible to water and air molecule resonate then others. Finally the choice of wavelength and polarisation are fundamental to match what your are looking to see.
A police radar detects a vehicle's average speed by recording how far a vehicle travels during a short period time Explain this in further detail?
The question is defective. The description given is not at all the method by which a police traffic radar measures the speed of a target vehicle. The radar unit measures the instantaneous speed of the target by measuring the difference between the frequency of the transmitted signal and the frequency of the echo-return from the target. The frequency of the return signal is Doppler-shifted in proportion to the radial component of the target's speed with respect to the radar unit. The period of time required for the measurement is essentially zero.
What does the Doppler radar measure?
A narrow microwave signal is directed at the moving vehicle at a known frequency, due to its motion the reflected signal will arrive back at the radar at a different frequency, an algorithm in the radar processor converts this difference to give the vehicles speed. Presumably the angle between the cop and the speeder will have to be taken into account as well.
What does radar measures?
It measures the time it takes for a radio signal of a particular frequency to travel to a target and back. It also measures the strength of the signal when it returns. Based on the travel time of the signal, the radar can measure the distance of the target. Once the radar receives the 2nd signal, it can calculate the velocity of the target. The strength of the signal can be used to determine the size of the target.
How is frequency difference and time difference measured in FMCW radar?
Frequency modulated continuous-wave (FM-CW) radar is usually used with a couple of different antennas. One is for the transmitted signal, and another one (or more) is (are) used for the reception of any returns. We usually think of radar as a pulse of electromagnetic energy that is transmitted out, and then a receiver looks for any returning (reflected) signal. In FM-CW radar, the transmitter is "always on" and a continuous signal is being sent. Additionally, the frequency of the transmitted signal is varied (or "swept") above and below a center frequency which the local oscillator runs on and maintains. The new units are largely microprocessor controlled pieces of equipment. They take the now-FM-modulated signal and broadcast it continuously (per the name - CW, which is continuous wave), and the returns are picked up by a receiver. The frequency of the return signal is compared to the instantaneous frequency of the transmitter, and the frequency difference can be looked at by a processor which can derive a time difference between the two signals (based on the differential frequency). This derived time difference will be proportional to the distance to the target that returned the signal. Another bit of processing on the signal returned from that target will produce a rate of change of distance, which can be converted to speed. As the power of the processors that we task with these objectives in mind has increased so dramatically, the processor can plot a course and speed with all appropriate vectors we wish to visualize when it puts up its findings on some kind of display - and in color! Particulars become technical very quickly, but the overview is accurate. A link to the Wikipedia article on FMCW is supplied, but at this writing, the article is still a stub that will supply little more than is here already.
How does the frequency of a cars returning radar signal change if the car moves away from the radar source?
The frequency of the radar signal does not change. Be it a cop getting you speed, or a modern car with Brake assist (they use a radar signal to assist keeping a safe distance) it's all timing, how long from the radar source to return to source. If a police car is still, and you are moving away, the increase in return of signal time tells the computer in the officer's car your speed. Even if you are going toward each other, the computer knows the speed of the officer's car and again, signal return time factored in with speed of cop car the computer can give an instant, real-time speed.
What is a radar gun?
A radar gun or speed gun is a device used to measure the speed of different objects. It might by a traffic officer to clock a vehicle's speed. Or perhaps a TV network is using it to clock a baseball pitcher's fast ball. The applications vary, but the unit works by applying the Doppler effect to discover how fast something is going. Basically, the unit sends out a signal and looks at the return signal. It compares the frequency of the returned signal to the transmitted one, and the difference can be "converted" into a speed.
What is the wavelength of a 27.75 109 Hz radar signal?
The wavelength of any frequency can be found using the fact that w*f = c, where w is the wavelength, f is the frequency, and c is the speed of light.
What is Continuous wave radar?
CW radar sets transmit a high-frequency signal continuously. The echo signal is received and processed permanently. One has to resolve two problems with this principle: prevent a direct connection of the transmitted energy into the receiver (feedback connection), assign the received echoes to a time system to be able to do run time measurements. A direct connection of the transmitted energy into the receiver can be prevented by: spatial separation of the transmitting antenna and the receiving antenna, e.g. the aim is illuminated by a strong transmitter and the receiver is located in the missile flying direction towards the aim; frequency dependent separation by the Doppler-frequency during the measurement of speeds. A run time measurement isn't necessary for speed gauges, the actual range of the delinquent car doesn't have a consequence. If you need range information, then the time measurement can be realized by a frequency modulation or phase keying of the transmitted power. A CW-radar transmitting a unmodulated power can measure the speed only by using the Doppler- effect. It cannot measure a range and it cannot differ between two reflecting objects.
