Projects:2020s1-1231 Radar Waveform Design - Revision history

A1706958 at 06:34, 21 October 2020

2020-10-21T06:34:51Z

A1706958 at 06:32, 21 October 2020

2020-10-21T06:32:56Z

A1706958 at 06:29, 21 October 2020

2020-10-21T06:29:08Z

A1706958 at 06:02, 21 October 2020

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A1706958 at 05:57, 21 October 2020

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A1706958 at 05:49, 21 October 2020

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A1706958 at 05:40, 21 October 2020

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A1706958 at 05:39, 21 October 2020

2020-10-21T05:39:49Z

A1706958 at 05:36, 21 October 2020

2020-10-21T05:36:22Z

A1706958 at 05:34, 21 October 2020

2020-10-21T05:34:49Z

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 Radar waveforms are generally classified under two classes: continuous wave (CW) and pulsed. The transmitter transmits a signal continuously with the CW waveform, usually without interruption, the whole time the radar transmitter is operating. The receiver also operates continuously. On the other hand, the pulsed waveform transmitter emits a sequence of pulses of finite duration, separated by the times in which the transmitter is "off." Since the transmitter is off, the receiver is on for detection of the target signals. For CW radars, it takes the bistatic configuration as the transmitter and receiver must be kept on constantly. In a CW radar, the round-trip time of the transmitted EM wave and hence the target range can be determined by alternating the composition of the wave (e.g.changing the frequency of the wave over time). This technique of FM effectively places a timing mark on the EM wave, thus allowing for the determination of the target range.
-Pulsed radars would usually take on the monostatic configuration as the transmitter and receiver are not utilized together and are kept isolated from each other. The radar transmits EM waves over a short period or pulse width, typically between 0.1 and 10 microseconds (𝜇𝑠), but sometimes as few as a few nanoseconds (10−9𝑛𝑠) and as long as a millisecond. As discussed previously the duplexer will provide the transition to radar to switch from transmitter to receiver, to allow the antenna to listen to echoes. The total time of transmitting (pulse width) and listening to the echoes is the completion of one pulsed radar cycle, also known as PRI.
+Pulsed radars would usually take on the monostatic configuration as the transmitter and receiver are not utilized together and are kept isolated from each other. The radar transmits EM waves over a short period or pulse width, typically between 0.1 and 10 microseconds (𝜇𝑠), but sometimes as few as a few nanoseconds (10−9𝑛𝑠) and as long as a millisecond. As discussed previously the duplexer will provide the transition to radar to switch from transmitter to receiver, to allow the antenna to listen to echoes. The total time of transmitting (pulse width) and listening to the echoes is the completion of one pulsed radar cycle, also known as PRI.<ref>"Linear Frequency Modulated Pulse Waveforms- MATLAB & Simulink", Mathworks.com, 2020. [Online]. Available: https://www.mathworks.com/help/phased/ug/linear-frequency-modulated-pulse-waveforms.html</ref>
 == Motivation ==

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 {| class="wikitable"
 |-
-! Results!! Description
+! Discription!! Results
 |-
 | By increasing the number of chips, the degree of freedom increases. Therefore, the suppression performance increases.||
@@ Line 88: / Line 88: @@
 {| class="wikitable"
 |-
-! Results!! Description
+! Description!! Results
 |-
 | Creating a mismatched filter of the same length, it can be shown that in order to suppress the sidelobes ( 15dB), there is significant loss in the main peak.||[[File: Matched and Mismatch filter same length.jpg|thumb]]

@@ Line 47: / Line 47: @@
 where,
 * 𝑅 is the slant range: the actual distance to the target and the radar
-* 𝑐 is the speed of light ≈3×108𝑚/𝑠
+* 𝑐 is the speed of light <math>\approx 3\times 10^{8}m/s</math>
 * 𝑡 is the total time taken for the EM wave to travel to the target and back to the radar
 |}
+Pulsed radars would usually take on the monostatic configuration as the transmitter and receiver are not utilized together and are kept isolated from each other. The radar transmits EM waves over a short period or pulse width, typically between 0.1 and 10 microseconds (𝜇𝑠), but sometimes as few as a few nanoseconds (10−9𝑛𝑠) and as long as a millisecond. As discussed previously the duplexer will provide the transition to radar to switch from transmitter to receiver, to allow the antenna to listen to echoes. The total time of transmitting (pulse width) and listening to the echoes is the completion of one pulsed radar cycle, also known as PRI.
 == Motivation ==

@@ Line 34: / Line 34: @@
 {| class="wikitable"
 |-
-| <math>Q_{t}=\frac{P_{t}}{4\piR^{2}}</math>||
+| <math>Q_{t}=\frac{P_{t}}{4 \pi R^{2}}</math>||
-[[File:The effect of number of chips to the suppression level.png|thumb]]
+where,
 |}

@@ Line 34: / Line 34: @@
 {| class="wikitable"
 |-
-| <math>Q_t = \frac{P_t}{4&piR^2}</math>||
+| <math>Q_{t}=\frac{P_{t}}{4\piR^{2}}</math>||
 [[File:The effect of number of chips to the suppression level.png|thumb]]
 |}

@@ Line 30: / Line 30: @@
 As discussed before that when a receiver antenna receives a reflected signal there can be a presence of clutter. However the interference does not only arise from clutter, it could come in the form of internal or external noise; unintentional external EM waves created by man-made sources, also known as electromagnetic interference; and intentional jamming from electronic countermeasures (ECM) system. These interferences could be in the form of noise or false targets. Thus, the processor needs to identify the target in the presence of noise, clutter or jamming.
-Previously, it was stated that due to the scattering effect, the reflected signal is diffused indicating that the received power will be weaker than the transmit power. However, in addition to that one of the major feature of the radar that can affect the intensity of the signal is the distance between the radar and the target. Assume that an isotropic antenna is emitting EM waves, the intensity of the propagating wave is calculated by the power emitted per unit area of the wave. Knowing that the radar acts as an isotropic antenna, it can be shown that the transmitted power density decreases by <math>\frac{1}{R^{2}}</math>
+Previously, it was stated that due to the scattering effect, the reflected signal is diffused indicating that the received power will be weaker than the transmit power. However, in addition to that one of the major feature of the radar that can affect the intensity of the signal is the distance between the radar and the target. Assume that an isotropic antenna is emitting EM waves, the intensity of the propagating wave is calculated by the power emitted per unit area of the wave. Knowing that the radar acts as an isotropic antenna, it can be shown that the transmitted power density decreases by <math>\frac{1}{R^{2}}</math>:
@@ Line 74: / Line 81: @@
 |-
 | With the previous conditions and allowing a loss in the main peak, it can be shown that it can suppress the sidelobes even greater ( 25dB) compared when there is no loss in the main peak.||  [[File:Matched and Mismatch filter different length loss 0.3.jpg|thumb|]]
 |}

@@ Line 71: / Line 71: @@
 | Creating a mismatched filter of the same length, it can be shown that in order to suppress the sidelobes ( 15dB), there is significant loss in the main peak.||[[File: Matched and Mismatch filter same length.jpg|thumb]]
 |-
-|  By shifting the suppression zone away from the mainlobe, the suppression performance increases as the initial energy of the range bins further from the mainlobe is lower.
+| Increasing the length of the mismatch filter three times the original length. There is significant improvement in the suppression of the sidelobes (20dB) and there is negligible loss in the main peak.|| [[File:Matched and Mismatch filter different length.jpg|thumb]]
 |-
-| By increasing the suppression width, the number of range bins where the energy could escape to decreases, causing the suppression performance to decrease.
+| With the previous conditions and allowing a loss in the main peak, it can be shown that it can suppress the sidelobes even greater ( 25dB) compared when there is no loss in the main peak.||  [[File:Matched and Mismatch filter different length loss 0.3.jpg|thumb|]]
 |-
 |  The effect of having multiple suppression zones does not affect the performance. ||