A Class F voltage-controlled oscillator based on a multi-port transformer

Abstract

The present invention relates to the field of millimeter wave communication technology, and discloses a Class F voltage-controlled oscillator based on a multi-port transformer, including a cross-coupled transistor, a multi-port transformer and an adjustable capacitor array. The multi-port transformer includes three windings, and through feedback between the first winding, the second winding and the third winding, a larger overdrive voltage VGS and a faster rise time can be obtained, which reduces the conversion of the MOS tube switching process noise to the phase, thereby improving the phase noise performance of the VCO for better application in the millimeter wave oscillator; by grounding the center tap of the third winding, a shorter path from the VCO power supply to the ground is provided, which facilitates the power supply decoupling connection; at the same time, the additional inductance can also adjust the phase difference between the ISF function and the current, and the Q value of the third winding can also be appropriately reduced to increase its series resistance, so as to be used for the operation of the linear transistor and reduce the amount of high-order drain current harmonics.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a Class F voltage-controlled oscillator based on a multi-port transformer. Background Art

[0002] With the development of wireless communication technology, people have higher and higher requirements for the rate of wireless transmission, and the modulation method of communication has become more and more complex. The modulation of the RF transceiver system depends on the local frequency source, and the voltage controlled oscillator (VCO) is the key circuit of the frequency source in the communication system, which puts higher requirements on the phase noise of the voltage controlled oscillator.

[0003] It is difficult to obtain high phase noise performance at millimeter wave frequency sources. In order to improve the phase noise performance of voltage-controlled oscillators, researchers have conducted in-depth analysis of the phase noise of oscillators and proposed many new structures, including ISF theory, harmonic tuning technology, multi-core oscillators, etc. For silicon-based CMOS processes, as the process size gradually decreases, the Ft frequency of transistors becomes higher and higher, but at the same time, the noise caused by transistors will also increase greatly.

[0004] Through the ISF theory, it can be obtained that the minimum ISF function is obtained at the maximum value of the waveform, so it is necessary to obtain a waveform that is more similar to a square wave and has a large ISF function at the rise time. In order to reduce the phase noise of the VCO, the Class F oscillator based on harmonic tuning uses a transformer to simultaneously realize the high-resistance network of the first-order and third-order frequencies, so that the drain of the active MOS tube obtains a square-wave-like voltage waveform, which reduces the time for the cross-coupled tube to enter the linear region, that is, reduces the conversion of the MOS tube switching process noise to phase, thereby improving the phase noise performance of the VCO. However, in the high millimeter wave frequency band, the traditional Class-F voltage-controlled oscillator is difficult to obtain a desired ideal pseudo-square wave due to the difficulty in controlling other harmonics and their influence, resulting in the actual phase noise performance not meeting expectations and difficult to be actually applied to high-frequency millimeter wave sources. Summary of the invention

[0005] The object of the present invention is to provide a Class F voltage-controlled oscillator based on a multi-port transformer which has excellent phase noise performance and is suitable for millimeter waves in view of the deficiencies in the prior art.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A Class F voltage-controlled oscillator based on a multi-port transformer comprises a cross-coupled transistor, a multi-port transformer, and an adjustable capacitor array; the multi-port transformer comprises a first winding L1, a second winding L2, and a third winding L3, and the three windings are coupled by induction.

[0008] Furthermore, the three windings are arranged horizontally, the turns ratio of the first winding to the second winding is 1:2, and the third winding is the innermost small inductor to provide the required coupling coefficient and inductance size.

[0009] Furthermore, the cross-coupled transistor is composed of an NMOS transistor M1 and an NMOS transistor M2 to form a negative resistance.

[0010] Further, the first winding L1 is connected to the drain of the cross-coupled transistor, the second winding L2 is connected to the gate of the cross-coupled transistor, the middle tap of the first winding L1 and the second winding L2 provides power and bias voltage for the cross-coupled transistor, the center tap of the first winding L1 is connected to the power supply voltage, and the center tap of the second winding L2 is connected to the bias voltage.

[0011] Furthermore, the third winding L3 is connected to the source of the cross-coupled transistor, and feedback is formed through the first winding L1 and the second winding L2 to reduce the rise time and phase noise.

[0012] Furthermore, the adjustable capacitor array includes a primary capacitor C1 and a secondary capacitor C2, the primary capacitor C1 is connected in parallel with the first winding L1, and the secondary capacitor C2 is connected in parallel with the second winding L2, and the adjustable capacitor array and the multi-port voltage are adjusted to form impedance peaks of the fundamental wave and the third harmonic.

[0013] Furthermore, the primary capacitor is used to expand the frequency band, and the secondary capacitor is used to adjust the content of the third harmonic, maintain sufficient third harmonic components, and achieve waveform shaping.

[0014] The present invention has the following effects:

[0015] (1) The multi-port transformer includes three windings. In the conventional Class-F VCO of the dual-winding transformer, an additional winding coil is introduced to the source end of the crossover transistor. Through the feedback between the first, second and third windings, a larger overdrive voltage VGS and a faster rise time can be obtained, which reduces the conversion of the MOS tube switching process noise to the phase, thereby improving the phase noise performance of the VCO for better application in millimeter wave oscillators.

[0016] (2) The center tap of the third winding is grounded to provide a shorter path from the VCO power supply to the ground, which facilitates the power supply decoupling connection. At the same time, the additional inductance can also adjust the phase difference between the voltage and current ISF functions, further reducing the phase noise.

[0017] (3) At the same time, the Q value of the third winding can be appropriately reduced to increase its parasitic series resistance, thereby enhancing the negative feedback of the circuit and improving the linearity of the circuit, thereby reducing unnecessary harmonic currents. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a Class-F voltage-controlled oscillator circuit in an embodiment of the present invention;

[0019] Figure 2 A structural diagram of a multi-port transformer of a Class-F voltage-controlled oscillator in an embodiment of the present invention;

[0020] Figure 3 The gate, source and drain voltage waveforms of the Class-F voltage-controlled oscillator cross-coupled transistor in an embodiment of the present invention;

[0021] Figure 4 is the phase noise spectrum of the Class-F voltage-controlled oscillator in an embodiment of the present invention;

[0022] Figure 5 The Class-F voltage controlled oscillator in the embodiment of the present invention outputs a tuning curve. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] like Figure 1 As shown in FIG. 1 , a schematic diagram of a circuit structure of a Class F voltage-controlled oscillator based on a multi-port transformer of the present invention is shown. A Class F voltage-controlled oscillator based on a multi-port transformer includes a cross-coupled transistor, a multi-port transformer, and an adjustable capacitor array; Figure 2 As shown, the multi-port transformer includes a first winding L1, a second winding L2 and a third winding L3. The three windings are horizontally arranged. The turns ratio of the first winding L1 and the second winding L2 is 1:2. The third winding L3 is the innermost small inductor to provide the required coupling coefficient and inductance size.

[0025] In this embodiment, the cross-coupled transistor is composed of NMOS tube M1 and NMOS tube M2, which are used to form negative resistance to start the oscillator and maintain oscillation. The multi-port transformer includes a first winding L1, a second winding L2 and a third winding L3. The two adjustable capacitor arrays include a primary capacitor C1 and a secondary capacitor C2.

[0026] In this embodiment, the first winding L1 is connected to the drain ports of the NMOS tubes M1 and M2, the second winding L2 is connected to the gates of the NMOS tubes M1 and M2, and the third winding L3 is connected to the gate of the cross-coupled transistor. Feedback is formed through the first winding L1 and the second winding L2 to reduce the rise time and reduce the phase noise.

[0027] In this embodiment, the center tap of the first winding L1 is connected to the power supply VDD, and the center tap of the second winding L2 is connected to the bias voltage; the first winding L1 and the second winding L2 are connected to the primary capacitor C1 and the secondary capacitor C2 respectively, and the adjustable capacitor array and the multi-port array are adjusted to form the impedance peaks of the fundamental wave and the third harmonic. The primary capacitor C1 is used to expand the frequency band, and the secondary capacitor C2 is used to adjust the content of the third harmonic to maintain sufficient third harmonic components.

[0028] like Figure 3 As shown, it is the voltage waveform diagram at both ends of the gate and drain of the cross-coupled transistor. Figure 4 and Figure 5 The curve of the phase noise and frequency modulation range of the whole frequency band output is shown in the simulation results. The phase noise of the frequency multiplier circuit is better than 110dBc / Hz@1MHz when the operating frequency is 25-28GHz, and it is optimized by about 4dB compared with the traditional VCO at 100KHz, which significantly reduces the flicker noise deflection angular frequency and optimizes the 1 / f 3 Phase noise in the area.

[0029] The above description is only a preferred implementation manner of the present invention, but the protection scope of the present invention is not limited thereto, and any modification and replacement based on the technical solution and inventive concept provided by the present invention should be included in the protection scope of the present invention.

Claims

1. A Class F voltage-controlled oscillator with a multi-port transformer, characterized in that: It includes a cross-coupled transistor, a multi-port transformer, and an adjustable capacitor array; the multi-port transformer includes a first winding L1, a second winding L2, and a third winding L3, and the three windings are coupled by induction; The first winding L1 is connected to the drain of the cross-coupling transistor, the second winding L2 is connected to the gate of the cross-coupling transistor, and a tap between the first winding L1 and the second winding L2 provides a common mode level and a bias voltage for the cross-coupling transistor; The third winding L3 is connected to the source of the cross-coupled transistor, and forms feedback through the first winding L1 and the second winding L2 to reduce the rise time and phase noise.

2. The Class F voltage-controlled oscillator of a multi-port transformer according to claim 1, characterized in that: The three windings are arranged horizontally, the turns ratio of the first winding L1 and the second winding L2 is 1:2, and the third winding is the innermost small inductor.

3. The Class F voltage-controlled oscillator of a multi-port transformer according to claim 1, characterized in that: The cross-coupled transistor is composed of an NMOS transistor M1 and an NMOS transistor M2.

4. The Class F voltage-controlled oscillator of a multi-port transformer according to claim 1, characterized in that: The adjustable capacitor array includes a primary capacitor C1 and a secondary capacitor C2. The primary capacitor C1 is connected in parallel with the first winding L1, and the secondary capacitor C2 is connected in parallel with the second winding L2.

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