(b)
Fig. 5. (a) 0dB crossover fabricated by compact two 3-dB BLC with
dimension using RT5880LZ substrate (b) The proposed design 0dB crossover
under test.
Design configuration butler matrix
The proposed design of the 4 × 4 BM was conducted using a computer
simulation technology
(CST)
microwave studio. The BM implementation was created using combined 3dB
BLC of Triangular slot and T-shape, two crossover structures, and
45o phase shifter at the operate frequency of 3.5 GHz.
The proposed design BM fabricated on a single layer of RT588LZ
substrate. The final fabrication of the proposed BM design, which had
the overall area of 87.5mm × 75mm, is as shown in Fig. 6.
The BM provided four outputs with equal amplitude and phase difference
of -45o, 135o,
45o, and -135o, respectively. As a
result, each input port, specifically as port 1, port 2, port 3, and
port 4 were designated as port 5, port 6, port 7, and port 8, was able
to produce four beams in various directions, as illustrated in Fig. 6.
This configuration was of a 4 × 4 BM. Table 3 shows the phase shift that
would be generated on each output based on the excited of the input
ports, and all other ports were terminated at 50Ω loads. There were four
cases. When input port 1 is excited the phase difference between the
output ports
-45o.
The output 135° phase difference when input port 2 is excited. The phase
difference between the output ports in the third case will be
-135o when input port 3 is excited. The last port
phase difference of the output port is 45° when input port 4 is excited.
The proposed BM was validated in accordance with design criteria
provided in Table 1.
Table
3. The phase difference between the outputs ports of the Butler matrix
feed.