ML7436N LSI Hardware Design Manual
FEXL7436NDG-01
18
Table 7.3
Reception matching value of each frequency bands
Frequency[MHz]
Lmatch[nH]
Cmatch[pF]
Cac[pF]
433
36
1.5
100
860
12.5
1.1
100
920
10
0.8
100
7.2.
SubGHz transmission circuit matching development procedure
This chapter explains an example of the transmission matching circuit development. The development procedure is as
following.
1.
Adjust Lch,Cp,Cs to Chapter10 application circuit.
2.
Cut the higher harmonics with T or π-type Chebyshev LPF(Cz,Lz,Cz) (
Figure 7.10
).
The cutoff frequency is approximately 1.5 times of the transmission frequency, the ripple of passband is
approximately 0.5dB, the order is approximately 3.
3.
Cut the second harmonic with the Notch filter Ln//Cn (
Figure 7.11
)
In case of the higher harmonics spurious of even number can not satisfy the standard, adjust the notch filter values
(Ln,Cn), cut the second harmonics. f0 is the transmission frequency. The notch filter values (Ln,Cn) is calculated as the
following formula.
2𝑓
0
=
1
2𝜋√𝐿
𝑛
𝐶
𝑛
Figure 7.10
π-type LPF(Cz,Lz,Cz) configuration
Figure 7.11
Second harmonics suppression with notch filter(Ln//Cn)
