Dave Barton Q&A

Dave Barton Image David K. Barton is a holder of the IEEE’s Centennial Medal, Millennium Medal, and Dennis J. Picard Medal, and is widely regarded throughout the world as a leading authority on radar technology. Now's your chance to ask Dave your own Radar question.....

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Question: Dear Dr. Barton, In your Book titled "Modern Radar System Analysis", Chapter 6 (Section 6.4) you discuss the correction due to atmospheric refraction. Figure 6.4.4 shows Range Bias Error vs Range. My question is, does this curve represent a one-way or two-way correction? Other figures such as the Attenuation Loss, specifically mention that it is a two-way correction, but not the one for the range correction due to atmospheric refraction.

Answer:

The bias error Dr in the plot is the excess in measured range over the true range, where the measured range is calculated from the two-way time delay td of the echo using

Hence the true range is obtained by subtracting the error Dr from the value calculated from the delay along the two-way path.
Note: This response applies also to Figure 6.27 in Radar System Analysis and Modeling.

Question: In Modern Radar System Analysis Software, Version 3.0, I am having difficulty in calculating detection range and plotting range-height-angle diagrams for a 3-D array in which an array antenna is mechanically rotating through 360 degrees in azimuth. The program will not accept an array that scans such a sector. How is this types of radar analyzed?

Answer:

I’m sorry for this problem. There are two solutions, until I can issue a modification that will correct the software. In either method, the calculation and coverage plot must be carried out separately for each elevation beam position in the 3-D coverage.

Method 1: The radar can be modeled as having a reflector antenna that scans mechanically through 360° at the appropriate rate.
In the Radar Model:
Section 1.2.1, Antenna Type: enter MA=0, reflector or lens
Beam Scan Method: enter MSM=0, mechanical scan
Section 1.2.3.3, Tx Efficiency and Gain Parameters: enter values that will match the actual Tx array gain.
Section 1.2.4.3, Rx Efficiency and Gain Parameters: if not copied from the Tx parameters, enter values that will match the actual Rx array gain.
Section 1.2.5, Scan Pattern Parameters: Elevation scan sector center: enter the elevation q¢eb of the beam to be analyzed
Scan period: enter a value of ts that matches to in the table of Section 1.2.5.2 to the actual dwell time of the 3-D beam.

Method 2: The radar can be modeled as a n electronically scanned array that scans a small sector near broadside in a period ts that matches to to the actual value, and that avoids significant off-broadside loss in gain. Thus, if the actual 3-D radar scans 360° in ts = 12s, it may be modeled as scanning ±15° in ts = 1s.

Either method should give the correct result.

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