AN199
Rev 0.8 | Page 3/8
frequency range of the VCO. The calculation is as follows.
首先根据希望配置的 RX 频率所属的目标频段，查表得到 FREQ_VCO_BANK<2:0>和
FREQ_DIVX_CODE<2:0>的值（两者都需要写入寄存器），和 分频系数 DIVIDER 的值（用于后续计算 N.K 值）：
First, check the table to get the value of FREQ_VCO_BANK<2:0> and FREQ_DIVX_CODE<2:0> (both
need to be written to the registers) and DIVIDER (frequency dividing factor, used to calculate N and K)
according to the target frequency band in which the configured frequency is located.
Table 3. Correspondence between PLL analysis parameters and target frequencies.
然后计算出 LO（本振）的频率。在下面的公式中，FREQ_RF 是目标射频频率，单位是 MHz。FREQ_LO
是计算出的本振频率，单位是 Hz。
Then calculate the frequency of the LO (local oscillator). 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 + 26 MHz/92
Then calculate the value of the frequency word N.K.
N.K = FREQ_LO x DIVIDER / 26 MHz
Obtain the integer part of N.K and convert it to binary, which is the value of FREQ_RX_N <7:0>. The fractional
part is multiplied by 2^20 and rounded off, which is the value of the register FREQ_RX_K <19:0>.
The last step is to get the value of AFC_OVF_TH <7:0>. This register is not in the frequency area. As which is
an important parameter of the receiver AFC algorithm, it is calculated based on the parameters of receivers
such as RX RF frequency, data rate, deviation, and crystal PPM. RFPDK will complete this calculation and
display it on the UI screen as follows.
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