tailieunhanh - Giai đoạn mảng anten P4

Many aircraft radars are now equipped with flat plane slot arrays instead of dish antennas, where the outline is approximately circular. These are usually fixed narrow-beam antennas with controlled sidelobes. Pattern synthesis typically usesthe product of two linear syntheses;one along the slot “sticks,” and a second across the sticks. These are often designed as Taylor ii patterns, as described in Chapter 3. Since the sticks near the edge are shorter, with fewer slots, than those at the center, the overall pattern will deviate somewhat from the product of the two orthogonal patterns. | Phased Array Antennas. Robert C. Hansen Copyright 1998 by John Wiley Sons Inc. ISBNs 0-471-53076-X Hardback 0-471-22421-9 Electronic CHAPTER FOUR Planar and Circular Array Pattern Synthesis CIRCULAR PLANAR ARRAYS Flat Plane Slot Arrays Many aircraft radars are now equipped with flat plane slot arrays instead of dish antennas where the outline is approximately circular. These are usually fixed narrow-beam antennas with controlled sidelobes. Pattern synthesis typically uses the product of two linear syntheses one along the slot sticks and a second across the sticks. These are often designed as Taylor n patterns as described in Chapter 3. Since the sticks near the edge are shorter with fewer slots than those at the center the overall pattern will deviate somewhat from the product of the two orthogonal patterns. In particular some adjustments may be necessary to produce the desired sidelobe envelopes in the principal planes. As these arrays are often divided into quadrants for azimuth and elevation monopulse a compromise may be advisable between the sum pattern sidelobes and the difference pattern sidelobes and slope see Chapter 3. An example of the design using the zero adjustment methods described in Chapter 3 of a planar array of inclined slots providing a cosecant type pattern with a Taylor n pattern in the cross plane is given by Erlinger and Orlow 1984 . Design of the array elements to include mutual coupling is more complex in that the entire array must be encompassed in the synthesis process. That synthesis is described in Chapter 6 and it can be extended to the flat plane array by using double sums for mutual coupling to include all slots. The iterative technique again converges rapidly. A typical flat plane slot array is shown in Fig. . See also Figs. and . Use of principal plane canonical patterns simplifies the synthesis process but lower sidelobes can be obtained through synthesis of a rotationally symmetric pattern as discussed in .