Varactor control circuit low in amplitude-frequency modulation efficiency and implementing method of varactor control circuit
A technology of control circuit and implementation method, which is applied in the direction of electrical components, power oscillators, etc., can solve the problems of reducing DCO jitter performance, and achieve the effect of simple structure and low jitter
Active Publication Date: 2014-12-17
CHANGSHA JINGJIA MICROELECTRONICS
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Therefore, the varactor control voltage V G_DS Periodic changes will occur as the DCO output waveform changes, resulting in periodic changes in the equivalent capacitance of the varactor, that is, a modulation effect from amplitude to frequency occurs, phase noise is introduced, and the jitter of the DCO is reduced performance
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[0023] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.
[0024] see figure 2 , figure 2 It is a schematic diagram of the varactor control circuit of the present invention. It includes a first NMOS transistor (M1), a first PMOS transistor (M2), a second PMOS transistor (M3), a third PMOS transistor (M4), a first fixed capacitance capacitor (C1), a first varactor ( VAR_MOS), wherein the gate of the first NMOS transistor (M1) is connected to the bias voltage (Vbias), the drain is connected to the drain of the first PMOS transistor (M2), the source and the substrate are connected to the power ground (GND), and the first The gate of the PMOS transistor (M2) is connected to the drain of the third PMOS transistor (M4), the drain and the gate are short-circuited, the source is connected to the drain of the second PMOS transistor (M3), the substrate is connected to the power supply (VDD), The s...
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The invention discloses a varactor control circuit low in amplitude-frequency modulation efficiency and an implementing method of the varactor control circuit. The varactor control circuit comprises a numerical-control direct-current voltage generating circuit, a fixed-capacitance capacitor and a varactor, and is characterized in that the varactor VAR_MOS operates in two capacitance stability areas by controlling digital input signals D, and the maximum capacitance and the minimum capacitance are realized; according to alternating current change characteristics that the fixed-capacitance capacitor C1 is coupled with a node OUT, alternating current characteristics of two ends of the varactor VAR_MOS are offset, direct-current voltage difference is kept constant, and equivalent capacitance cannot change as change of voltage of the node OUT. By adopting four MOS tubes, one fixed-capacitance capacitor and one varactor, the varactor control circuit has the advantages of low amplitude-frequency modulation efficiency, low implementation difficulty and shaking and the like.
Description
technical field [0001] The invention mainly relates to the field of frequency synthesizer design, in particular to a varactor control circuit structure for realizing gate array capacitance. Background technique [0002] With the development of wireless communication technology, the operating frequency of radio frequency chips continues to increase, and the frequency range continues to expand. Because the frequency synthesizer has the advantages of wide output frequency range, short locking time and good anti-interference, it has been widely used in the field of wireless communication. As a key module of the frequency synthesizer, the DCO mainly provides a high-frequency oscillation signal source for the frequency synthesizer. According to different control signals, DCO can generate high-frequency signals with a wide frequency range, and this key feature is mainly realized based on the capacitance of the numerically controlled gate array. [0003] For the varactor control c...
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Inventor 郭斌
Owner CHANGSHA JINGJIA MICROELECTRONICS