AN199
Rev0.7 | 6
/8
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1.2
Configuring RF Parameters of TX
Followings need to be configured for TX.
FREQ_VCO_BANK <2:0>
FREQ_DIVX_CODE <2:0>
FREQ_TX_N <7:0>
FREQ_TX_K <19:0>
FREQ_PALDO_SEL
Among them, FREQ_VCO_BANK<2:0> and FREQ_DIVX_CODE <2:0> are obtained in the same way as in RX, that is, TX and
RX share DIVX CODE and VCO BANK. If the target frequency bands are not the same, when each time TX or RX is configured,
recalculation and writing to these two registers is needed.
Then calculate the frequency of the LO (local oscillator), which is different from the LO frequency of RX. In the formula below,
FREQ_RF is the target RF frequency in MHz. FREQ_LO is the calculated local oscillator frequency in Hz.
FREQ_LO = FREQ_RF x 10^6
Then calculate the value of the frequency word N.K, which is the same as the N.K value calculation formula for RX:
N.K = FREQ_LO x DIVIDER / 26 MHz
At last, check the table below to get the value of FREQ_PALDO_SEL:
TX Frequency
FREQ_PALDO_SEL
< 500 MHz
0
>= 500 MHz
1
For example, if the target RF frequency for TX to be configured is 433.92 MHz, according to the above calculation, it can obtain
the followings.
.
is 001, and DIVIDER is 4.
433920000.
66.75692308.
TX_N <7:0> is 66 and the corresponding binary is 01000010
FREQ_TX_K <19:0> is 793691 and the corresponding binary is
11000001110001011011.
FREQ_PALDO_SEL is 0.
