AK2400 Datasheet, PDF (44/52 Pages) Asahi Kasei Microsystems – High integrated receiver for PMR-LMR

L11, C11, L12 and C12 are calculated as below. fout is IF output frequency.
1
  ^{C11  C12 } 2π * f_IF * R_L1  R_L2 * R_O
[AK2400]
  _{L11  L12 }
R_L1  R_L2 * R_O
2π * f_IF
For example, in the case of IF Output = 50MHz, Output Load Resistor (Rload) = 2.2k in 50 interface,
L11, C11, L12 and C12 are calculated as below.
C₁₁

C₁₂

1
2π *50*10^6*
2.2 *10^3* 50

9.6p F
2.2 *10^3* 50
L₁₁  L₁₂  _{2π *50*10^6}  1056nH
L13 and C13 should be large enough not to affect the impedance at IF output frequency. In some
cases the impedance matching can be optimized by L13 and C13.
For example, in the case of IF Output = 50MHz, Output Load Resistor (Rload) = 2.2k in 50 interface,
it is recommended to choose 2200nH and 1000pF as L13 and C13. If any correction is needed, it can
be adjusted by reducing the value of L13 and C13.
These calculated values are approximation. In some cases, some correction is needed due to the
effect of parasitic capacitance of external parts or/and PCBs. The impedance matching network
components should be decided through enough evaluation on AK2400.
Typical evaluation board component values in 50 interface are shown as below.
IF Output Frequency [MHz]
29.25
46.35
50.85
58.05
RL1/RL2 [k]
1.1
1.1
1.1
1.1
L11/L12 [nH]
1800
1000
1000
1000
C11/C12 [pF]
15
10
9.1
8.2
L13 [nH]
2200
2200
2200
2200
C13 [pF]
270
220
82
39
The phase and amplitude balance is achieved at IF Output frequency by using impedance matching
network with LC. The port-to-port leakage is improved with the phase and amplitude balance is
achieved at RF, LO, and IF frequency with wide band balun.
014008989-E-01
44
2015/4