80M ～ 120MHz frequency band PLL frequency synthesizer. Figure 27-1 shows the 80 ～ 120MHz frequency synthesizer (PLL Frequency Synthesizer) using PLL IC TC9122 (Toshiba). The oscillation frequency is changed by 400kHz per step. The frequency division ratio is 8 to 3999, which can be set by BCD code. It is a very useful IC, as shown in Figure 27-2. VCO is the 2SK192LC oscillating circuit introduced earlier. The varactor diode uses 1SV50. The oscillating signal is taken out by the tank and then output after a first-stage buffer stage.
The oscillating output of 100MHz is 10kHz after two frequency divisions such as TC9122 and μPB552C (Nippon Electric), and then the 10kHz of the reference oscillator TC5082 is compared for phase comparison, and then the comparison output signal is taken out from the third terminal of the TC5081 of the phase comparator and returned A filter (Loop Filter) converts its signal to a VCO circuit to form a PLL circuit. The maximum input frequency of the TC9122 is 15MHz, and the maximum input frequency of the prescaler (μB55252C) is 150MHz. Oscillation frequency f (KHZ)
The formula is as follows: f = k‧m‧n
m represents the frequency division ratio of TC9122, n represents the frequency division ratio of μPB552C, and k represents the comparison frequency (KHz)
For example, n = 40, if you want a frequency of f = 100MHz, then set m = 250.
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