4. optimized high pass filter – GW Instek GRF-3300 Series Student Manual User Manual
Page 17
16 Microstrip Line Filters
3
325
2.0
2.2
2.4
2.6
2.8
3.0
-25
-20
-15
-10
-5
0
Coupled Line BPF
Insertion Loss (dB)
Frequency (GHz)
before fine tune
after fine tune
Figure 16-8
Fine-tuned values were used for actual measurements.
16-4. Optimized High Pass Filter
There are several ways to design a high pass filter in microstrip form. In this
section, we will introduce an easy way to fabricate a high pass filter, which can also be
considered as a wideband band pass filter.
16-4-1. Design Example
We will design a high pass filter with 0.1dB ripple and 1.5GHz cut off frequency.
The input and output impedance are both 50
:. The PCB material is FR4 with dielectric
constant of 4.2 and thickness of 1.2 mm.
16-4-2. Solution
First, we assume that the pass band is from 1.5GHz to 4.7GHz.
q
o
u
¸¸¹
·
¨¨©
§
35
1
7
.
4
c
c
c
f
GHz
-
-
S
Referring to Table 16-2, we choose
c
-
=
q
35 and N = 4, then y1, y12, y2 and y23
become as follows:
x
y1=0.4467
x
y12=1.03622