A Low Phase Noise Broadband Ring Oscillator
Through the two-stage delay module structure and the design of latch and transmission gate units, the contradiction between the frequency range and VCO gain in the Ring-VCO design is solved, and a low-phase noise broadband ring oscillator is realized, which improves the complexity of PLLs Diffusion performance and loop stability.
Patent Information
- Application Number
- CN201810919559.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2018-08-14
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2038-08-14
AI Technical Summary
The existing Ring-VCO designs are difficult to meet the needs of large frequency range, low phase noise and low power consumption at the same time. There is a contradiction between the frequency range and VCO gain, resulting in an increase in loop filter area and deterioration of PLL stray performance.
Adopting a two-stage delay module structure, the latch unit provides additional delay, and the oscillating signal conversion rate is increased through the positive feedback formed by the latch unit. The transmission gate unit adjusts the frequency and is located outside the power supply and ground paths, adopts switching capacitor arrays and transmissions. The gate unit can adjust the frequency with variable resistance, and use low-threshold devices to improve fine-tuning gain linearity.
A low-phase noise broadband ring oscillator with large output frequency range, low phase noise and low power consumption is realized, which improves the stray performance and loop stability of the PLL, reduces the VCO tuning gain, and enhances the resistance to power supply fluctuations. Interference.
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Figure CN110830007B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor integrated circuits, and in particular to a low phase noise broadband ring oscillator. Background Art
[0002] With the development of the integrated circuit industry, phase locked loops (PLLs) are widely used in the design of clocks and frequency synthesizers. The application of clock modules includes providing high-performance clocks to high-performance analog to digital converters (ADCs) and baseband output stage interface circuits. These applications require the clock phase locked loop to have a low jitter and wide frequency range output. Generally speaking, the design of PLLs is divided into two typical categories. One is the PLL using an inductor capacitor voltage controlled oscillator (LC-VCO), which has the advantages of good noise performance and low power consumption, but the disadvantages are large area and small tuning range; the other is the PLL using a ring voltage controlled oscillator (Ring-VCO), which has the advantages of large tuning range, small area, good process portability, and is not easily affected by electromagnetic coupling, but the disadvantages are poor noise performance and relatively high power consumption. The design and research of the PLL based on Ring-VCO has attracted the attention of engineers due to its advantages such as small area.
[0003] In order to improve the output phase noise performance of the Ring-VCO-based PLL, it is necessary to solve the most basic contradiction between the small bandwidth requirements of the charge pump, divider, quantization noise, etc. and the large bandwidth requirements of the Ring-VCO. Some mainstream methods use downsampling structures or injection-locked loops to optimize the noise in the band so that the loop can use a large bandwidth to suppress the phase noise of the Ring-VCO, solve the bandwidth contradiction described above, and enable the Ring-VCO-based PLL to obtain the same phase noise performance as the LC-VCO PLL. However, the use of downsampling loops will introduce problems such as limited capture range, so it is still practical to design a Ring-VCO-type PLL based on the traditional PLL top-level structure.
[0004] To solve Rin g The phase noise problem of -VCO type PLL makes it particularly important to design a low phase noise Ring-VCO. The two most commonly used existing technologies are:
[0005] Prior art 1: A differential amplifier with a resistor as a load is used as a delay unit, and four delay units are connected. One delay unit in the loop is connected in the same phase, and the other delay units are connected in the opposite phase. Figure 1 As shown, positive feedback technology is used to adjust the delay time of the delay unit. When the current I1 changes, the small signal equivalent impedance of M3 and M4 will change, and the equivalent load impedance of the differential pair will also change, which will cause the delay time of the delay unit to change, thereby adjusting the frequency of the oscillator. The defects of this technology are: due to the use of a four-stage delay unit, the phase noise performance is limited, the power consumption is large, and the frequency is controlled by adjusting the resistance value of the negative resistance pair, resulting in a small tuning range. At the same time, as a differential tuning structure, a differential charge pump structure is required to control it, which limits its application in PLL.
[0006] Prior art 2: using two feedback loops to convert a single-ended transmission gate ring oscillator into a differential ring oscillator with the ability to resist power supply fluctuations. Figure 2 As shown, MP1 and MP2 form the first feedback loop to compensate for the delay time fluctuation caused by power supply fluctuation; MN1 and MN2 form the second feedback loop, forming a mutually coupled latch to achieve differential operation and further power supply noise suppression. The disadvantages of this technology are: the tuning control device is inside the delay unit, the oscillation is easily affected by the tuning voltage Vctrl in the figure, and four-stage delay units are also required to meet the oscillation conditions, the phase noise performance is limited, and the power consumption is large.
[0007] It can be seen that in the prior art, Rin g -It is difficult for VCO design to simultaneously meet the requirements of large frequency range, low phase noise and low power consumption. Summary of the invention
[0008] In view of the problems in the prior art of Ring-VCO design, such as high power consumption, contradiction between frequency range and VCO gain, that is, the gain is large when the frequency range is large, but too large gain will increase the area of the loop filter and deteriorate the PLL spurious performance, and poor phase noise, the present invention provides a low phase noise broadband ring oscillator, which has a large output frequency range, low phase noise and low power consumption.
[0009] The present invention provides a low phase noise broadband ring oscillator, comprising a first-stage delay module and a second-stage delay module; the first-stage delay module and the second-stage delay module form a loop circuit for providing the phase shift and gain required for the low phase noise broadband ring oscillator to start oscillation;
[0010] An input terminal of the first-stage delay module is connected to an output terminal of the second-stage delay module;
[0011] Another input end of the first-stage delay module is connected to another output end of the second-stage delay module;
[0012] An output terminal of the first-stage delay module is connected to an input terminal of the second-stage delay module;
[0013] Another output terminal of the first-stage delay module is connected to another input terminal of the second-stage delay module;
[0014] The first-stage delay module includes an input-output inverter unit, a latch unit, a switch capacitor array unit, and a transmission gate unit;
[0015] The second-stage delay module includes an input-output inverter unit, a latch unit, a switch capacitor array unit, and a transmission gate unit;
[0016] The switch capacitor array unit and the switch capacitor array unit are controlled using the same digital control bit;
[0017] The transmission gate unit and the transmission gate unit share the same tuning voltage.
[0018] Preferably, the input-output inverter unit includes a first inverter and a second inverter; the latch unit includes a third inverter and a fourth inverter;
[0019] The input end of the first inverter is an input end of the first-stage delay module;
[0020] The input end of the second inverter is another input end of the first-stage delay module;
[0021] The input end of the third inverter is connected to the output end of the fourth inverter, and the connected end is connected to the output end of the first inverter and one end of the switch capacitor array unit;
[0022] The output end of the third inverter is connected to the input end of the fourth inverter, and the connected end is connected to the output end of the second inverter and the other end of the switch capacitor array unit.
[0023] Preferably, the switched capacitor array unit includes one or at least two parallel switched capacitor branches, each switched capacitor branch is provided with a switch and two capacitors with equal capacitance, and the switch is arranged between the two capacitors; the switched capacitor branch is switched on and off by a digital control bit to adjust the capacitance value output by the switched capacitor branch, which is used for coarse adjustment of the output frequency of the low phase noise broadband ring oscillator and division of the output frequency band.
[0024] Preferably, the transmission gate unit comprises a first transmission gate and a second transmission gate;
[0025] The input end of the first transmission gate is connected to one end of the switch capacitor array unit; the output end of the first transmission gate is connected to an output end of the low phase noise broadband ring oscillator;
[0026] An input end of the second transmission gate is connected to the other end of the switch capacitor array unit, and an output end of the second transmission gate is connected to the other output end of the low phase noise broadband ring oscillator.
[0027] Preferably, the first transmission gate includes a first PMOS transistor and a first NMOS transistor;
[0028] The source of the first PMOS tube is connected to the source of the first NMOS tube;
[0029] The drain of the first PMOS tube is connected to the drain of the first NMOS tube;
[0030] The gate of the first PMOS tube is provided with a port connected to a first ground voltage;
[0031] The gate of the first NMOS tube is provided with a port connected to a first tuning voltage;
[0032] The second transmission gate includes a second PMOS tube and a second NMOS tube;
[0033] The source of the second PMOS tube is connected to the source of the second NMOS tube;
[0034] The drain of the second PMOS tube is connected to the drain of the second NMOS tube;
[0035] The gate of the second PMOS tube is provided with a port connected to a second ground voltage;
[0036] The gate of the second NMOS tube is provided with a port connected to a second tuning voltage.
[0037] Preferably, the first ground voltage connected to the port is equal to the second ground voltage connected to the port;
[0038] The first tuning voltage connected to the port is equal to the second tuning voltage connected to the port.
[0039] Preferably, the first PMOS transistor, the second PMOS transistor, the first NMOS transistor and the second NMOS transistor are low threshold devices, which are used to improve the fine-tuning gain linearity of the low phase noise broadband ring oscillator.
[0040] Preferably, the frequency of the low phase noise broadband ring oscillator is changed by adjusting the gate voltages of the first NMOS tube and the second NMOS tube to change the resistance values of the first NMOS tube and the second NMOS tube.
[0041] Preferably, the circuit structures of the first-stage delay module and the second-stage delay module are completely the same.
[0042] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:
[0043] The present invention mainly aims at the problems of large power consumption, contradiction between frequency range and VCO gain, that is, the gain is large when the frequency range is large, but too large gain will increase the area of the loop filter and deteriorate the PLL spurious performance, and poor phase noise in the existing widely used Ring-VCO, and proposes a low phase noise broadband ring oscillator: the additional delay provided by the latch unit itself is used to enable the two-stage delay module to maintain oscillation, saving power consumption; the positive feedback formed by the latch unit is used to improve the conversion rate of the oscillation signal at the edge; because the frequency adjustment of the transmission gate unit is located outside the path of the power supply and the ground, the use of such a tuning method can increase the anti-interference of the circuit to power supply fluctuations; at the same time, the present invention adopts a method of adjusting the frequency by a switch capacitor array unit and a transmission gate unit variable resistor to achieve coarse and fine frequency adjustment of the low phase noise broadband ring oscillator in view of the contradiction between the Ring-VCO tuning range and the tuning gain, which will be beneficial to the suppression of PLL output spurious; in addition, the use of a low threshold device in the design of the transmission gate improves the fine gain linearity of the Ring-VCO. BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.
[0045] Figure 1 It is a circuit schematic diagram of a delay unit in the prior art;
[0046] Figure 2 It is a circuit schematic diagram of a differential ring oscillator in the second prior art;
[0047] Figure 3 A structural block diagram of a low phase noise broadband ring oscillator provided by an embodiment of the present invention;
[0048] Figure 4A circuit schematic diagram of a first-stage delay module in a low phase noise broadband ring oscillator provided by an embodiment of the present invention;
[0049] Figure 5 A circuit schematic diagram of a second-stage delay module in a low phase noise broadband ring oscillator provided by an embodiment of the present invention. DETAILED DESCRIPTION
[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0051] The embodiment of the present invention provides a low phase noise broadband ring oscillator, such as Figure 3 As shown, the low phase noise broadband ring oscillator includes a first-stage delay module 1 and a second-stage delay module 2; the first-stage delay module 1 and the second-stage delay module 2 form a loop for providing the phase shift and gain required for the low phase noise broadband ring oscillator to start oscillation;
[0052] An input terminal IN1_P of the first-stage delay module 1 is connected to an output terminal OUT2_N of the second-stage delay module 2;
[0053] Another input terminal IN1_N of the first-stage delay module 1 is connected to another output terminal OUT2_P of the second-stage delay module 2;
[0054] An output terminal OUT1_P of the first-stage delay module 1 is connected to an input terminal IN2_P of the second-stage delay module 2;
[0055] Another output terminal OUT1_N of the first-stage delay module 1 is connected to another input terminal IN2_N of the second-stage delay module 2 .
[0056] It is common sense that an oscillator is a circuit that does not require external signal excitation and can convert direct current power into a periodic alternating current output signal. The oscillator needs to meet certain starting conditions, called the Barkhausen criterion, that is, when the phase shift of the loop gain is 360°, the amplitude of the loop gain must be no less than 1, and the feedback system can generate oscillations. In this embodiment, in order to achieve a stable oscillation output, the low phase noise broadband ring oscillator is composed of two delay modules with the same circuit structure to form a loop, and the loop transfer function only satisfies the Barkhausen criterion at one frequency point to achieve its frequency selection characteristics. The first delay module 1 and the second delay module 2 both provide the phase shift and gain required for starting, so that the feedback loop composed of the two delay modules can meet the Barkhausen criterion and achieve normal oscillator function.
[0057] See also Figure 4 , shows a circuit schematic diagram of a first-stage delay module in a low phase noise broadband ring oscillator provided by an embodiment of the present invention. Figure 4 As shown, the first-stage delay module 1 includes an input-output inverter unit 11, a latch unit 12, a switch capacitor array unit 13 and a transmission gate unit 14; the input-output inverter unit 11 is used to introduce a delay on the signal path; the additional delay provided by the latch unit 12 itself is used to enable the two-stage delay module to maintain oscillation, saving power consumption; the positive feedback formed by the latch unit 12 is used to increase the conversion rate of the oscillation signal at the edge; since the frequency adjustment of the transmission gate unit 14 is located outside the path of the power supply and the ground, such a tuning method can increase the circuit's anti-interference ability to power supply fluctuations; the method of adjusting the frequency by the switch capacitor array unit 13 and the transmission gate unit 14 variable resistor is used to achieve coarse and fine frequency adjustment of the low phase noise broadband ring oscillator.
[0058] Specifically, Figure 4 As shown, the input-output inverter unit 11 includes a first inverter X1 and a second inverter X2; the latch unit 12 includes a third inverter X3 and a fourth inverter X4; the input end of the first inverter X1 is connected to an input end IN1_P of the first-stage delay module 1; the input end of the second inverter X2 is connected to another input end IN1_N of the first-stage delay module 1; the input end of the third inverter X3 and the output end of the fourth inverter X4 are connected, and the connecting end is connected to the output end of the first inverter X1 and one end of the switch capacitor array unit 13; the output end of the third inverter X3 and the input end of the fourth inverter X4 are connected, and the connecting end is connected to the output end of the second inverter X2 and the other end of the switch capacitor array unit 13.
[0059] In this embodiment, if Figure 4The first-stage delay module 1 shown is a complementary input and complementary output structure, which can maximize the conversion rate of the oscillation signal at the edge. Among them, X1 and X2 introduce a certain delay in the signal path; the latch unit 12 composed of X3 and X4 forms a positive feedback between the output terminal OUT1_P and the output terminal OUT1_N when a state transition occurs, thereby accelerating the state transition rate.
[0060] The mean square value Γ of the ISF (Impulse Sensitivity Function) of the ring oscillator rms It can be expressed by formula (1):
[0061]
[0062] Where A = f rise / f fall , f rise and f fall are the maximum slopes of the rising and falling edges of the oscillation signal, respectively, and represent the ratio of the maximum slopes of the rising and falling edges of the oscillation signal. It can be seen from formula (1) that increasing the state conversion rate of the ring oscillator at the rising and falling edges can reduce the mean square value of ISF Γ rms , that is, reducing the phase noise performance of the low phase noise broadband ring oscillator. Under the selected process, the state conversion rate is mainly determined by the characteristic frequency of the transistor provided by the process. When the characteristic size of the transistor is reduced and the characteristic frequency is increased, the conversion rate of the ring oscillator can be further improved, and the phase noise performance can also be further improved.
[0063] Therefore, when the latch unit 12 composed of X3 and X4 undergoes a state transition, a positive feedback is formed between the output terminal OUT1_P and the output terminal OUT1_N, thereby accelerating the state transition rate and improving the phase noise performance.
[0064] In addition, since the latch unit 12 introduces additional delay time, a two-stage delay module can maintain stable oscillation, and reducing the number of delay unit stages can also improve phase noise performance.
[0065] Specifically, Figure 4As shown, the switch capacitor array unit 13 includes one or at least two parallel capacitor branches, each switch capacitor branch is provided with a switch Ki (i=1, 2, 3, 4...n, n is a positive integer greater than 1) and two capacitors Ci (i=1, 2, 3, 4...n, n is a positive integer greater than 1) with equal capacitance, and the switch Ki is arranged between the two capacitors. For example, a switch K1 and two capacitors C1 with equal capacitance are arranged on the first switch capacitor branch, and the structures of other switch current source branches are the same or similar to those of the first switch current source branch, which will not be described one by one here. Multiple parallel switch capacitor branches are disconnected and controlled by digital control bits to adjust the capacitance value of the switch capacitor, which is used for coarse adjustment of the output frequency of the low phase noise broadband ring oscillator, and the wide frequency band to be output by the low phase noise broadband ring oscillator is divided into multiple frequency bands for output.
[0066] Specifically, Figure 4 As shown, the transmission gate unit 14 includes a first transmission gate 141 and a second transmission gate 142; the circuit structures of the first transmission gate 141 and the second transmission gate 142 are exactly the same; the input end of the first transmission gate 141 is connected to one end of the capacitor array unit 13; the output end of the first transmission gate 141 is connected to an output end OUT1_N of the low phase noise broadband ring oscillator; the input end of the second transmission gate 142 is connected to the other end of the switch capacitor array unit 13, and the output end of the second transmission gate 142 is connected to another output end OUT1_P of the low phase noise broadband ring oscillator.
[0067] The first transmission gate 141 includes a first PMOS tube PM1 and a first NMOS tube NM1; the source of the first PMOS tube PM1 is connected to the source of the first NMOS tube NM1; the drain of the first PMOS tube PM1 is connected to the drain of the first NMOS tube NM1; the gate of the first PMOS tube PM1 is provided with a port Port1_VSS connected to the first ground voltage VSS1; the gate of the first NMOS tube NM1 is provided with a port Port1_Vtune connected to the first tuning voltage Vtune1.
[0068] The second transmission gate 142 includes a second PMOS tube PM2 and a second NMOS tube NM2; the source of the second PMOS tube PM2 is connected to the source of the second NMOS tube NM2; the drain of the second PMOS tube PM2 is connected to the drain of the second NMOS tube NM2; the gate of the second PMOS tube PM2 is provided with a port Port2_VSS connected to the second ground voltage VSS2; the gate of the second NMOS tube NM2 is provided with a port Port2_Vtune connected to the second tuning voltage Vtune2.
[0069] The first ground voltage VSS1 connected to the port Port1_VSS is equal to the first ground voltage VSS2 connected to the port Port2_VSS; the second tuning voltage Vtune1 connected to the port Port1_Vtune is equal to the second tuning voltage Vtune2 connected to the port Port2_Vtune.
[0070] In this embodiment, the first PMOS tube PM1, the second PMOS tube PM2, the first NMOS tube NM1 and the second NMOS tube NM2 are low threshold devices, which are used to improve the fine-tuning gain linearity of the low phase noise broadband ring oscillator. Compared with traditional MOS devices, low threshold devices reduce the doping concentration of the substrate on the layout, and the threshold voltage of the MOS tube refers to the minimum gate voltage when strong inversion is formed. It is stipulated that when the surface electron concentration is equal to the equilibrium multi-carrier concentration in the body, a strong inversion layer is formed on the semiconductor surface, so when the doping concentration of the substrate decreases, the threshold voltage of the MOS decreases accordingly. Thereby, the tuning gain change in the MOS resistance tuning process is reduced, and the gain linearity is optimized.
[0071] The gate voltage of the first NMOS tube NM1 and the second NMOS tube NM2 is adjusted to change the resistance value of the first NMOS tube NM1 and the second NMOS tube NM2, thereby changing the frequency of the low phase noise broadband ring oscillator. The frequency adjustment method of the variable resistance of the transmission gate unit 14 and the switch capacitor array unit 13 is adopted to achieve fine adjustment and coarse adjustment of the frequency of the low phase noise broadband ring oscillator.
[0072] See also Figure 5 , shows a circuit schematic diagram of a second-stage delay module in a low phase noise broadband ring oscillator with low phase noise bandwidth provided by an embodiment of the present invention. The circuit structure of the second-stage delay module 2 is exactly the same as that of the first-stage delay module.
[0073] In this embodiment, the switched capacitor array unit 13 and the switched capacitor array unit 23 are controlled by the same digital control bit; the transmission gate unit 14 and the transmission gate unit 24 share the same tuning voltage.
[0074] The present invention aims at the problems of large power consumption, contradiction between frequency range and VCO gain, i.e., large gain when frequency range is large, but too large gain will increase the area of loop filter and deteriorate PLL spurious performance, poor phase noise, etc. of the existing Ring-VCO, and proposes a low phase noise broadband ring oscillator: the additional delay provided by the latch unit itself is used to enable the two-stage delay module to maintain oscillation, saving power consumption; the positive feedback formed by the latch unit is used to improve the conversion rate of the oscillation signal at the edge; since the frequency adjustment of the transmission gate unit is located outside the path of the power supply and the ground, such a tuning method can increase the circuit's anti-interference ability to power supply fluctuations. At the same time, the present invention aims at the contradiction between the tuning range and tuning gain of the Ring-VCO, adopts the method of adjusting the frequency by the switch capacitor array unit and the transmission gate unit variable resistor, and realizes the fine and coarse adjustment and coarse and fine adjustment of the frequency of the low phase noise broadband ring oscillator, which will be conducive to reducing the VCO tuning gain, and then reducing the PLL output reference spurious; in addition, the use of low threshold devices in the design of the transmission gate improves the fine adjustment gain linearity of the Ring-VCO. Finally, a broadband, low phase noise Ring-VCO is realized with low tuning gain and high tuning linearity, which will be beneficial to the phase noise and spurious performance as well as the loop stability of the PLL based on the Ring-VCO.
[0075] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.
[0076] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.
Claims
1. A low phase noise broadband ring oscillator, characterized in that: The low phase noise broadband ring oscillator comprises a first-stage delay module (1) and a second-stage delay module (2); the first-stage delay module (1) and the second-stage delay module (2) form a loop circuit, which is used to provide the phase shift and gain required for the low phase noise broadband ring oscillator to start oscillation; An input end (IN1_P) of the first-stage delay module (1) is connected to an output end (OUT2_N) of the second-stage delay module (2); Another input end (IN1_N) of the first-stage delay module (1) is connected to another output end (OUT2_P) of the second-stage delay module (2); An output end (OUT1_P) of the first-stage delay module (1) is connected to an input end (IN2_P) of the second-stage delay module (2); Another output end (OUT1_N) of the first-stage delay module (1) is connected to another input end (IN2_N) of the second-stage delay module (2); The first-stage delay module (1) comprises a first input-output inverter unit (11), a first latch unit (12), a first switch capacitor array unit (13) and a first transmission gate unit (14); The second-stage delay module (2) comprises a second input-output inverter unit (21), a second latch unit (22), a second switch capacitor array unit (23) and a second transmission gate unit (24); The first switch capacitor array unit (13) and the second switch capacitor array unit (23) are controlled using the same digital control bit; The first transmission gate unit (14) and the second transmission gate unit (24) share the same tuning voltage; The first input-output inverter unit (11) comprises a first inverter (X1) and a second inverter (X2); The first latch unit (12) includes a third inverter (X3) and a fourth inverter (X4); An input end of the first inverter (X1) is an input end (IN1_P) of the first-stage delay module (1); The input end of the second inverter (X2) is another input end (IN1_N) of the first-stage delay module (1); The input end of the third inverter (X3) and the output end of the fourth inverter (X4) are connected to each other, and the connected end is connected to the output end of the first inverter (X1) and one end of the first switch capacitor array unit (13); The output end of the third inverter (X3) and the input end of the fourth inverter (X4) are connected to each other, and the connected end is connected to the output end of the second inverter (X2) and the other end of the first switch capacitor array unit (13); The first switch capacitor array unit (13) comprises one or at least two switch capacitor branches connected in parallel, each switch capacitor branch is provided with a switch and two capacitors with equal capacitance, and the switch is provided between the two capacitors; the switch capacitor branch is switched on and off by a digital control bit to adjust the capacitance value output by the switch capacitor branch, so as to roughly adjust the output frequency of the low phase noise broadband ring oscillator and divide the output frequency band; The first transmission gate unit (14) comprises a first transmission gate (141) and a second transmission gate (142); The input end of the first transmission gate (141) is connected to one end of the first switch capacitor array unit (13); the output end of the first transmission gate (141) is connected to an output end (OUT1_N) of the low phase noise broadband ring oscillator; An input end of the second transmission gate (142) is connected to the other end of the first switch capacitor array unit (13), and an output end of the second transmission gate (142) is connected to another output end (OUT1_P) of the low phase noise broadband ring oscillator; The circuit structures of the first-stage delay module (1) and the second-stage delay module (2) are completely the same.
2. The low phase noise broadband ring oscillator according to claim 1, characterized in that: The first transmission gate (141) comprises a first PMOS transistor (PM1) and a first NMOS transistor (NM1); The source of the first PMOS transistor (PM1) is connected to the source of the first NMOS transistor (NM1); The drain of the first PMOS tube (PM1) is connected to the drain of the first NMOS tube (NM1); The gate of the first PMOS tube (PM1) is provided with a port (Port1_VSS) connected to a first ground voltage (VSS1); The gate of the first NMOS tube (NM1) is provided with a port (Port1_Vtune) connected to the first tuning voltage (Vtune1); The second transmission gate (142) includes a second PMOS transistor (PM2) and a second NMOS transistor (NM2); The source of the second PMOS transistor (PM2) is connected to the source of the second NMOS transistor (NM2); The drain of the second PMOS tube (PM2) is connected to the drain of the second NMOS tube (NM2); The gate of the second PMOS tube (PM2) is provided with a port (Port2_VSS) connected to a second ground voltage (VSS2); The gate of the second NMOS transistor (NM2) is provided with a port (Port2_Vtune) connected to the second tuning voltage (Vtune2).
3. The low phase noise broadband ring oscillator according to claim 2, characterized in that: The first ground voltage (VSS1) connected to the port (Port1_VSS) and the second ground voltage (VSS2) connected to the port (Port2_VSS) are equal; The first tuning voltage (Vtune1) connected to the port (Port1_Vtune) and the second tuning voltage (Vtune2) connected to the port (Port2_Vtune) are equal.
4. The low phase noise broadband ring oscillator according to claim 2, characterized in that: The first PMOS tube (PM1), the second PMOS tube (PM2), the first NMOS tube (NM1) and the second NMOS tube (NM2) are low threshold devices, which are used to improve the fine-tuning gain linearity of the low phase noise broadband ring oscillator.
5. The low phase noise broadband ring oscillator according to claim 2, characterized in that: The gate voltages of the first NMOS tube (NM1) and the second NMOS tube (NM2) are adjusted to change the resistance values of the first NMOS tube (NM1) and the second NMOS tube (NM2), thereby changing the frequency of the low phase noise broadband ring oscillator.