CN108768301A - A kind of LC voltage controlled oscillators of substrate dynamic bias - Google Patents

Abstract

The invention discloses an LC voltage-controlled oscillator with substrate dynamic bias, which includes a cross-coupling pair, a substrate dynamic bias circuit, a resonant cavity, a capacitor array and a frequency tuning module, wherein the control end of the cross-coupling pair is connected to the substrate Dynamic bias circuit connection, the output terminals of the cross-coupling pair are respectively connected in parallel with the resonant cavity, capacitor array, and frequency tuning module; the cross-coupling pair provides negative resistance to compensate for the loss of the resonant cavity; the inductance and capacitance determine the oscillation frequency, and the capacitor array selects the frequency band range , to ensure that all process corners meet the frequency band coverage requirements, the varactor is responsible for fine-tuning the oscillation frequency, and the substrate dynamic bias circuit is responsible for real-time adjustment of the substrate voltage. There are connection points at the intersections of all the connections in Figure 1. This oscillator structure automatically adjusts the substrate voltage following the oscillation waveform after stable oscillation, preventing the transistor from entering the linear region and deteriorating the phase noise, while being insensitive to the influence of environmental factors.

Description

A LC Voltage Controlled Oscillator with Substrate Dynamic Bias

technical field

The invention belongs to the technical field of voltage-controlled oscillators, in particular to an LC voltage-controlled oscillator with substrate dynamic bias.

Background technique

In the radio frequency receiving system, the phase-locked loop is responsible for providing a stable local oscillator signal for the mixer, which is the core module in the receiving chain, and the voltage-controlled oscillator is one of the key modules of the phase-locked loop, and its power consumption is in the lock The phase loop even occupies a considerable share in the entire receiving chain. Therefore, in order to realize the low power consumption of the overall receiving circuit, it is very important to optimize the power consumption design of the voltage-controlled oscillator.

From a structural point of view, when the power supply voltage is low, since the threshold voltage of the transistor cannot be reduced proportionally with the process, it is difficult to start the oscillator and the start-up time is long. In this case, it is necessary to adjust the substrate voltage to reduce The threshold voltage of the transistor reduces the start-up time. However, from the perspective of the entire voltage-controlled oscillator, reducing the threshold makes it easier for the transistor to enter the linear region, which deteriorates the overall Q value and increases the phase noise. At the same time, the PN junction is positively biased. risks of.

Contents of the invention

The purpose of the present invention is to provide an LC voltage-controlled oscillator with substrate dynamic bias, which automatically adjusts the substrate voltage following the oscillation waveform after stable oscillation, avoiding the transistor from entering the linear region, deteriorating phase noise, and affecting environmental factors at the same time Not sensitive.

In order to achieve the above object, the solution of the present invention is:

An LC voltage-controlled oscillator with substrate dynamic bias, including a cross-coupled pair, a substrate dynamic bias circuit, a resonant cavity, a capacitor array, and a frequency tuning module, wherein the control end of the cross-coupled pair is dynamically biased with the substrate The circuit is connected, and the output ends of the cross-coupling pair are respectively connected in parallel with the resonant cavity, the capacitor array, and the frequency tuning module.

The above-mentioned cross-coupled pair includes first and second NMOS transistors, wherein the sources of the first and second NMOS transistors are connected and grounded, the gate of the first NMOS transistor is connected to the drain of the second NMOS transistor, and the first NMOS transistor The drain of the first and second NMOS transistors is connected to the gate of the second NMOS transistor, and the substrates of the first and second NMOS transistors are used as the control terminals of the cross-coupled pair, and are connected to the substrate dynamic bias circuit; the drains of the first and second NMOS transistors As the output ends of the cross-coupling pair, they are respectively connected in parallel with the resonant cavity, the capacitor array, and the frequency tuning module.

The substrate dynamic bias circuit includes the third and fourth NMOS transistors and the third and fourth capacitors, wherein the upper plate of the third capacitor is connected to the drain of the first NMOS transistor, and the gate of the third NMOS transistor and After the drain is short-circuited, it is connected to the lower plate of the third capacitor, the source of the third NMOS transistor is grounded, and the gate of the third NMOS transistor is connected to the substrate of the first NMOS transistor; the upper plate of the fourth capacitor is connected to the first NMOS transistor. The drain of the second NMOS transistor is connected, the grid and drain of the fourth NMOS transistor are short-circuited, and then connected to the lower plate of the fourth capacitor, the source of the fourth NMOS transistor is grounded, and the gate of the fourth NMOS transistor is connected to the first The substrate of the two NMOS transistors.

The resonant cavity includes a fifth capacitor, a sixth capacitor and an inductor, wherein the fifth and sixth capacitors are connected in parallel with the inductor after being connected in series, and the inductor is connected in parallel with the cross-coupling pair.

The above-mentioned frequency tuning module includes first and second capacitors, first and second resistors and first and second varactors, wherein one end of the first capacitor is used as one end of the frequency tuning module, and the other end of the first capacitor is sequentially passed through The first varactor and the second varactor are connected to one end of the second capacitor, and the other end of the second capacitor is used as the other end of the frequency tuning module, and one end and the other end of the frequency tuning module are respectively connected in parallel with the cross-coupling pair; After the first and second resistors are connected in series, one end is connected between the first capacitor and the first varactor, and the other end is connected between the second capacitor and the second varactor.

After adopting the above scheme, the present invention has the following advantages relative to the prior art:

(1) Using dynamic bias, the substrate voltage is adjusted in real time with the oscillation waveform, and the threshold voltage is reduced when the current is required. It is necessary to avoid raising the threshold voltage when the transistor enters the linear region, reducing the phase noise;

(2) At the beginning of the oscillation, the zero bias voltage is provided for the substrate through the capacitor and the MOS transistor, so as to avoid the risk of forward bias of the PN junction of the transistor.

Description of drawings

Fig. 1 is a circuit diagram of the present invention;

Fig. 2 is a graph of phase noise of voltage controlled oscillators using the present invention and not using the present invention.

Detailed ways

The technical solutions and beneficial effects of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Fig. 1, the present invention provides a kind of LC voltage-controlled oscillator of substrate dynamic bias, and this oscillator comprises cross-coupled pair, resonant cavity, capacitance array, substrate dynamic bias circuit and frequency tuning module, from function The module division is consistent with the traditional LC oscillator: the cross-coupling pair provides negative resistance to compensate for the loss of the resonant cavity; the inductance and capacitance determine the oscillation frequency, the frequency tuning module realizes small-scale precise tuning, and the capacitor array selects the frequency band range to ensure that all process angles The frequency band coverage requirements are met, and the substrate dynamic bias circuit is responsible for real-time adjustment of the substrate voltage. In Figure 1, there are connection points at the intersections of all connection lines.

The cross-coupled pair and the substrate dynamic bias circuit include: M1, M2, M3, M4 and C3, C4, wherein M1, M2, M3, and M4 are NMOS transistors, and C3 and C4 are capacitors. The gate of M1 is connected to the drain of M2; the gate of M2 is connected to the drain of M1; the upper plate of C4 is connected to the drain of M2; the gate of M4 is connected to the drain, and then connected to the lower plate of C4 It is connected to the substrate of M2, and the gate of M4 is used as a feedback terminal to control the substrate voltage of M2; the upper plate of C3 is connected to the drain of M1; the gate of M3 is connected to the drain, and then connected to the lower plate of C3 and The substrate of M1 is connected, and the gate of M3 is used as a feedback terminal to control the substrate voltage of M1.

As shown in FIG. 2 , curve A is the phase noise curve of the VCO without substrate dynamic bias, and curve B is the phase noise curve of the VCO with low power consumption substrate dynamic bias in this embodiment. It can be seen from the figure that the phase noise is reduced by 0.2dBc at 1M frequency offset after using the substrate dynamic biasing technique.

It can be seen from the above that the innovation of this embodiment is mainly reflected in the design of the substrate dynamic bias circuit. The substrate voltage of the traditional LC oscillator is a fixed potential. Although the start-up time of the oscillator is reduced, it also makes it easier for the transistor to enter the linear region and deteriorates the phase noise. The present invention proposes a substrate dynamic bias circuit, which can adjust the substrate voltage of the cross-coupled pair in real time with the oscillation waveform, and bias the substrate at zero voltage at DC, avoiding the risk of forward bias of the PN junction of the transistor. After stable oscillation, when the gate voltage of a transistor of the cross-coupled pair is at the maximum value and its drain voltage is the minimum value, the substrate voltage is negative, and the substrate voltage is increased to prevent the transistor from entering the linear region and deteriorating Q value. Compared with the traditional substrate bias technology, the invention improves the Q value of the circuit and reduces the phase noise under the same power consumption.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (5)

1. a kind of LC voltage controlled oscillators of substrate dynamic bias, it is characterised in that：Including cross-coupled pair, substrate dynamic bias electricity Road, resonant cavity, capacitor array and frequency tuning module, wherein the control terminal of cross-coupled pair connects with substrate dynamic bias circuit Connect, the output end of cross-coupled pair respectively with resonant cavity, capacitor array, frequency tuning wired in parallel.

2. a kind of LC voltage controlled oscillators of substrate dynamic bias as described in claim 1, it is characterised in that：The cross-couplings To including the first, second NMOS tube, wherein the source electrode of the first, second NMOS tube is connected and is grounded, the grid of the first NMOS tube with The drain electrode of second NMOS tube connects, and the drain electrode of the first NMOS tube is connect with the grid of the second NMOS tube, the first, second NMOS tube Control terminal of the substrate as cross-coupled pair, connect with substrate dynamic bias circuit；The drain electrode of first, second NMOS tube is as friendship Fork coupling pair output end, respectively with resonant cavity, capacitor array, frequency tuning wired in parallel.

3. a kind of LC voltage controlled oscillators of substrate dynamic bias as claimed in claim 2, it is characterised in that：The substrate dynamic Biasing circuit includes third, the 4th NMOS tube and third, the 4th capacitance, wherein the top crown of third capacitance and the first NMOS tube Drain electrode connection, after the grid of third NMOS tube and drain electrode short circuit, reconnect the bottom crown of third capacitance, the source of third NMOS tube Pole is grounded, and the grid of third NMOS tube connects the substrate of the first NMOS tube；The leakage of the top crown and the second NMOS tube of 4th capacitance Pole connects, and after the grid and drain electrode short circuit of the 4th NMOS tube, reconnects the bottom crown of the 4th capacitance, the source electrode of the 4th NMOS tube connects Ground, the grid of the 4th NMOS tube connect the substrate of the second NMOS tube.

4. a kind of LC voltage controlled oscillators of substrate dynamic bias as described in claim 1, it is characterised in that：The resonant cavity packet Include the 5th capacitance, the 6th capacitance and inductance, wherein the five, the 6th capacitances series connection after, then with inductance in parallel, and inductance with intersect Coupling is to being in parallel.

5. a kind of LC voltage controlled oscillators of substrate dynamic bias as described in claim 1, it is characterised in that：The frequency tuning Module includes the first, second capacitance, the first, second resistance and the first, second varactor, wherein one end conduct of the first capacitance The other end of one end of frequency tuning module, the first capacitance connects the second capacitance through the first varactor, the second varactor successively One end, the other end of the other end of the second capacitance as frequency tuning module, one end of the frequency tuning module and the other end It is in parallel respectively with cross-coupled pair；After the series connection of first, second resistance, one end is connected between the first capacitance, the first varactor, The other end is connected between the second capacitance, the second varactor.