Fine Tuning the Load Resistors at a Single Frequency

11 FINE TUNING THE LOAD RESISTORS AT A SINGLE FREQUENCY 

In the last section we demonstrated how resistive loading of one or more columns located at the edges of the finite array could lead to a significant reduction of the surface waves. We considered the entire frequency range of interest, but our choice of a resistive profile was based on a combination of intuition and experience. 

In this section we shall demonstrate a more systematic and also more precise approach. In general, it is performed only at a single frequency. However, experience has shown that the performance at the rest of the frequency band will in general be superior as well. 

More specifically we show in Fig. 4.19a the column currents for an array comprised of 25 columns at / = 7.8 GHz. The angle of incidence is 45° as shown in the insert below in the figure. There are no resistive loads at all, and this case therefore serves as our baseline. Next we show in Fig. 4.19b the same array but where the three outer columns are loaded with 200, 100, and 50 ohms. 

SURFACE WAVES ON PASSIVE SURFACES OF FINITE EXTENT 

---