Frequency synthesizer, frequency selection circuit and frequency selection method thereof
A technology of frequency synthesizer and frequency selection circuit, which is applied in the field of frequency synthesizer, can solve the problems of interfering with the DC operating point of the mixer and the decline of anti-interference ability, and achieve the effect of simple structure, low noise and high performance
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Embodiment 1
[0027] This embodiment introduces the present invention by taking the mixing of 1 / 3 of the required frequency and 2 / 3 of the required frequency as an example. The present invention combines a 1 / 3+2 / 3 filter circuit and a frequency mixing circuit to amplify useful signals and filter and suppress useless signals.
[0028] see Figure 2 to Figure 4 , the present invention discloses a frequency selection circuit of a frequency synthesizer, the frequency selection circuit includes a capacitor C1, a capacitor C2, an inductor L1, and an inductor L2; the two ends of the capacitor C1 are respectively connected to one end of the inductor L1 and the inductor L2; The two ends of the capacitor C2 are respectively connected to the other end of the inductor L1 and the inductor L2; the two ends of the capacitor C1 are respectively connected to the mixer, and the connection terminals are denoted as OUTP and OUTN; the values of the inductor and capacitor C2 are set to make the circuit resonat...
Embodiment 2
[0048] figure 1 It is a schematic structural diagram of a mixer in this embodiment, wherein the mixer uses an up-selective LC network as a load.
[0049] figure 2 is the schematic diagram of the LC network, image 3 , Figure 4 Yes figure 2 Equivalent circuit diagram of the schematic for the LC network. The two inductors adopt the structure of a transformer, which not only increases the inductance value of the inductor but also reduces the area.
[0050] exist figure 2 In the frequency selection circuit, first select the value of L and C (parallel connection of CC3 and CC1 / 2) to make it resonate at the frequency (low frequency) to be filtered, and the impedance seen at both ends of OUTP and OUTN is the equivalent of the inductance The series resistance realizes the filtering function. exist figure 2 The LC resonant circuit in the equivalent circuit of the stop band shows an inductance characteristic as the frequency becomes higher for the pass band. At this time, ...
Embodiment 3
[0053] This embodiment discloses a frequency synthesizer, which includes a frequency selection circuit and a frequency mixing circuit. The frequency selection circuit includes a capacitor C1, a capacitor C2, an inductor L1, and an inductor L2; the two ends of the capacitor C1 are respectively connected to one end of the inductor L1 and the inductor L2; the two ends of the capacitor C2 are respectively connected to the other end of the inductor L1 and the inductor L2 ; At the same time, the two ends of the capacitor C1 are respectively connected to the mixer, and the connection points are recorded as OUTP and OUTN; the values of the inductance and the capacitor C2 are set to make the circuit resonate at the frequency of the filter, and the impedance at both ends of OUTP and OUTN is the equivalent of the inductance series resistance, the frequency selection circuit is a filter circuit; the value of the capacitor C1 is set to make the circuit resonate at the frequency of the pas...
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