Voltage controlled oscillator

Abstract

The invention relates to a voltage controlled oscillator, which comprises four transistors, an integrated on-chip inductor and two symmetric variable capacitors, wherein, two transistors realize negative resistance through cross coupling, thereby providing energy to oscillate an LC circuit comprising the inductor and the variable capacitors; by changing the capacitance of the variable capacitors, different output frequencies of the oscillator are obtained. The invention also comprises two resistors with the same value and two capacitors with the same value; a grid terminal of one of the rest transistors is connected with a terminal of a resistor and a terminal of a capacitor at the same time, which jointly form an active inductor; a grid terminal of the last transistor is connected with a terminal of a resistor and a terminal of a capacitor at the same time, thus jointly forming another active inductor; the two active inductors provide bias current for the voltage controlled oscillator. The invention enlarges the tuning range of the voltage controlled oscillator and reduces the phase noise.

Description

technical field [0001] The invention relates to radio transmission technology, in particular to a voltage-controlled oscillator in a wireless transceiver system. Background technique [0002] With the rapid development of integrated circuit technology, it is possible to highly integrate the wireless transceiver system. An integrated voltage controlled oscillator (vco) and frequency synthesizer is a very important and critical part of a wireless transceiver system. Currently popular wireless communication standards, such as Wireless Local Area Network (WLAN), GSM (Globle System for Mobile Communication), WiMax (Worldwide Interoperability for Microwave Access, Microwave Access Global Interoperability), etc., all require voltage-controlled oscillators to have wide tuning range and low phase noise. [0003] The wide tuning range refers to that within a certain range of control voltage variation, the output frequency of the voltage-controlled oscillator is based on a certain ce...

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Problems solved by technology

[0008] However, using figure 2 The voltage-controlled oscillator with the structure shown has several disadvantages: 1) Transistors M1, M2, M3, and M4 have certain parasitic capacitances, which will be a big problem for high-frequency voltage-controlled oscillators

On the one hand, the available tuning range of the voltage-controlled oscillator is reduced, and on the other hand, the highest frequency available to the voltage-controlled oscillator is reduced; 2) The flicker noise (1 / f noise) existing in transistors M1, M2, M3 and M4 will degrades the phase noise performance of the overall VCO

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