AK2401 Datasheet, PDF (33/103 Pages) Asahi Kasei Microsystems – Direct Conversion Transceiver

[AK2401]
An equivalent circuit is needed at the input of the MIXER (Figure 19). The DEMIN pin must be connected
to the ground via L2 choke inductor to settle the DC voltage. C5 and L3 are matching elements for
impedance conversion.
C5
23. DEMIN
L3
L2
Figure 19. Equivalent Circuit for MIXER Input Block
13.5.2. Analog Filter Frequency Characteristics
Analog block frequency characteristics are shown in Figure 20. The low-pass filter of the analog block is
composed by a PGA (programmable gain amplifier) and an AAF (anti-aliasing filter). The cutoff frequency
(Fc) of the PGA can be switched byRXLPF_FC bit <Address 0x14>. FC = 45 kHz when RXLPF_FC bit =
“0”, and Fc = 90 kHz when RXLPF_FC bit = “1”. The cutoff frequency (Fc) of the AAF is Fc = 100 kHz.
RXLPF_FC bit should be set according to digital channel filter settings. Refer to “13.8.2. Digital Filter
Frequency Characteristics” for details.
20
0
RXLPF_FC bit="0"
-20
RXLPF_FC bit="1"
-40
-60
-80
-100
-120
-140
1000
10k
100k
1M
10M
Frequency [Hz]
Figure 20. Analog Filter Frequency Characteristics (Maximum PGA Gain Setting)
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