Frequency source chip of integrated automatic frequency locking and high-linearity oscillator for optical communication

Abstract

The invention belongs to the technical field of integrated circuits, and particularly relates to a frequency source integrating automatic frequency control and a high-linearity voltage-controlled oscillator. The circuit structure of the frequency source comprises a phase frequency detector, a charge pump, a loop filter, a multiband voltage-controlled oscillator, an automatic frequency controller and a programmable fractional frequency divider. A signal of the reference frequency and a signal fed back by the programmable frequency divider are input into the phase frequency detector, and the phase frequency detector compares rising edges of the two signals and outputs a pulse signal to the charge pump; the charge pump converts an input pulse signal into a current signal and charges and discharges the loop filter; the loop filter converts the received current signal into a voltage signal and outputs the voltage signal to the voltage-controlled oscillator; the voltage-controlled oscillator adjusts the frequency of an output signal according to an input voltage signal and a control word of the automatic frequency controller, and feeds back the output signal to the phase frequency detector through the programmable fractional frequency divider to realize loop locking. A capacitor array of the voltage-controlled oscillator is composed of a varactor array and a capacitor tube array, continuous tuning of output frequency is achieved by adjusting varactors, and the automatic frequency controller changes the capacitor tube array of the voltage-controlled oscillator through control words to achieve discrete frequency tuning. Therefore, a wide output frequency range is achieved under the condition of low voltage-controlled oscillator tuning gain, phase noise is optimized at the same time, and automatic locking of frequency in bandwidth can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and particularly relates to a frequency source integrating automatic frequency control and a high-linearity voltage-controlled oscillator applied to in-vehicle Ethernet. Background Art

[0002] As a core component of modern communication systems, frequency sources are widely used in fields such as wireless communication, data transmission, and radar systems. In in-vehicle Ethernet, especially in the application of 10G in-vehicle Ethernet, the stability and accuracy of the frequency source are crucial. As the core of data transmission in in-vehicle systems, in-vehicle Ethernet has high transmission rates, large bandwidth requirements, and extremely high requirements for data transmission stability and reliability. With the continuous development of in-vehicle networks, especially in the fields of autonomous driving and intelligent connected vehicles, 10G Ethernet provides higher bandwidth and lower latency, making the performance of the frequency source have an important impact on the working stability and efficiency of the entire network system.

[0003] Traditional phase-locked loop (PLL) frequency source technologies usually achieve frequency synthesis and stability by adjusting a voltage-controlled oscillator. However, existing technologies still have certain limitations in terms of high precision, high tuning rate, and low phase noise. First of all, existing PLL frequency sources are difficult to provide sufficient high precision. Especially in high-frequency applications, their output frequencies may be affected by factors such as temperature changes and aging effects, resulting in a decrease in system accuracy and being unable to meet the strict requirements of 10G in-vehicle Ethernet for frequency stability. Secondly, traditional PLL frequency sources also have deficiencies in tuning rate and cannot quickly respond to changes in external signals or loads, resulting in a slow frequency adjustment speed of the system and affecting the real-time performance and stability of overall data transmission. In addition, due to the complex structure and limited noise suppression ability of traditional PLLs, they usually generate relatively large phase noise, further reducing the signal quality of the system and thus affecting the efficient data transmission and stability of in-vehicle Ethernet.

[0004] Therefore, in view of the technical limitations of existing PLL frequency sources in terms of accuracy, tuning rate, and phase noise, the present invention proposes a phase-locked loop circuit with automatic frequency locking. Through innovative design, this circuit achieves higher accuracy, faster tuning, and better phase noise performance, and is particularly suitable for the 10G in-vehicle Ethernet environment with high stability and high reliability requirements. Summary of the Invention

[0005] The object of the present invention is to propose a frequency source integrating automatic frequency control and a high-linearity voltage-controlled oscillator applied to in-vehicle Ethernet.

[0006] The frequency source integrating automatic frequency control and high-linearity voltage-controlled oscillator for in-vehicle Ethernet proposed by the present invention has a circuit structure including: a phase-frequency detector, a charge pump, a loop filter, a voltage-controlled oscillator, an automatic frequency controller, and a programmable fractional divider. The signal of the reference frequency and the signal fed back by the programmable divider are input to the phase-frequency detector. The phase-frequency detector compares the rising edges of the two signals and outputs a pulse signal to the charge pump; the charge pump converts the input pulse signal into a current signal to charge and discharge the loop filter; the loop filter converts the received current signal into a voltage signal and outputs it to the voltage-controlled oscillator; the voltage-controlled oscillator adjusts the frequency of the output signal according to the input voltage signal and the control word of the automatic frequency controller, and feeds it back to the phase-frequency detector through the programmable fractional divider to achieve loop locking.

[0007] In the present invention, the automatic frequency controller includes an analog part of the automatic frequency controller and a digital part of the automatic frequency controller. The analog part of the automatic frequency controller receives the output signal generated by the loop filter, calculates it through an operational amplifier to generate a high and low voltage identification signal to the digital part of the automatic frequency controller. The digital part of the automatic frequency controller receives the reference frequency signal and counts, and finally outputs the corresponding capacitance array control signal and varactor array control signal.

[0008] In the present invention, the voltage-controlled oscillator contains a pair of cross-coupled transistors as negative resistance tubes, and an inductor with a center tap connected to the power supply is connected between the cross-coupled transistors; the inductor is connected in parallel with the capacitance array and the varactor array. Both the capacitance array and the varactor array are composed of capacitance tube pairs. Each capacitance tube pair consists of two common-source common-drain transistors, and the source and drain are connected and connected to the output of the frequency controller.

[0009] For the frequency source designed by the present invention, since the automatic frequency controller can automatically select an appropriate frequency range, the function of automatic frequency locking can be realized; since the voltage-controlled oscillator contains a capacitance array and a varactor array, the capacitance array realizes discrete tuning of the frequency, and the varactor array realizes continuous tuning of the frequency. Moreover, the varactor array will change the number of capacitance tube pairs connected to the resonant cavity according to the state of the capacitance array, so as to achieve a relatively stable voltage tuning gain, thereby optimizing the phase noise of the output signal and realizing precise control of the frequency. Description of the Drawings

[0010] Figure 1 It is a schematic diagram of the structure of the high-linearity frequency source integrating automatic frequency control of the present invention.

[0011] Figure 2 It is a schematic diagram of the loop filter circuit.

[0012] Figure 3 It is a schematic diagram of the structure of the automatic frequency controller.

[0013] Figure 4 It is a flowchart of the working process of the automatic frequency controller.

[0014] Figure 5 It is a circuit schematic diagram of the voltage-controlled oscillator and its capacitor array.

[0015] Figure 6 It is a circuit schematic diagram of the varactor diode array of the voltage-controlled oscillator. Specific embodiments

[0016] The present invention will be described in more detail below with reference to the accompanying drawings. In the various drawings, like elements are denoted by like reference numerals. For the sake of clarity, the various parts in the drawings are not drawn to scale. In addition, some well-known parts may not be shown in the figures.

[0017] Many specific details of the present invention are described below, such as the structure, materials, dimensions, processing techniques and technologies of the devices, in order to understand the present invention more clearly. However, as those skilled in the art can understand, the present invention can be implemented without these specific details.

[0018] Figure 1 It shows a schematic diagram of the structure of a high-linearity frequency source integrating automatic frequency control of the present invention.

[0019] As Figure 1 shown, the frequency source 100 integrating automatic frequency control and high-linearity voltage-controlled oscillator in the present invention includes: a frequency discriminator and phase detector 101, a charge pump 102, a loop filter 103, a voltage-controlled oscillator 104, an automatic frequency controller 105, and a programmable fractional divider 106. The initial reference frequency signal F_REF and the signal F_DIV fed back by the programmable fractional divider are used as the input signals of the frequency discriminator and phase detector 101. The output signals Qa and Qb of the frequency discriminator and phase detector 101 are coupled to the input of the charge pump 102. The output Io of the charge pump 102 is coupled to the input of the loop filter 103, and the output Vt of the loop filter is coupled to the input of the voltage-controlled oscillator 104. The initial reference frequency signal F_REF and the output Vc of the loop filter 103 are coupled to the input of the automatic frequency controller 105. The automatic frequency controller 105 outputs a signal to the voltage-controlled oscillator 104. The voltage-controlled oscillator 104 outputs a signal F_OUT with a frequency different from the input reference frequency as the output of the system and inputs it to the programmable fractional divider 106. The programmable fractional divider 106 feeds back its output to the frequency discriminator and phase detector 101.

[0020] Figure 2 It shows a circuit schematic diagram of the loop filter of the present invention.

[0021] As Figure 2As shown, the loop filter 103 in the present invention includes resistors R1, R3 and capacitors C1, C2, C3. Among them, the input node Io is simultaneously connected to the first ends of the resistor R1, the capacitor C2 and the resistor R3; the second end of the resistor R1 is connected to the first end of the capacitor C1, the second end of the capacitor C1 is grounded to GND, and the connection point serves as the output node Vc; the second end of the capacitor C2 is directly grounded to GND; the second end of the resistor R3 is connected to the first end of the capacitor C3, the second end of the capacitor C3 is grounded to GND, and the connection point serves as the output node Vt.

[0022] Figure 3 The structural schematic diagram of the automatic frequency controller of the present invention is shown.

[0023] As Figure 3 shown, the automatic frequency controller 105 in the present invention includes an automatic frequency controller analog part 200 and an automatic frequency controller digital part 201. Among them, the automatic frequency controller analog part 200 includes two operational amplifiers OP1 and OP2. The input signal Vc is connected to the non-inverting input ports of the operational amplifier OP1 and the operational amplifier OP2. The high voltage threshold V H is connected to the inverting input port of the operational amplifier OP1, and the low voltage threshold V L is connected to the inverting input port of the operational amplifier OP2. The operational amplifier OP1 outputs a high voltage identification signal V_HIGH_SIG to the automatic frequency controller digital part 201, and the operational amplifier OP1 outputs a low voltage identification signal V_LOW_SIG to the automatic frequency controller digital part 201. The initial reference frequency signal F_REF is connected to the automatic frequency controller digital part 201, and the automatic frequency controller digital part 201 outputs a control signal CTRL of an M-bit <m:1>and an N-bit control signal BAND <n:1>。

[0024] Figure 4 Shows the working flow block diagram of the automatic frequency controller of the present invention.

[0025] As Figure 4 shown, the working process of the automatic frequency controller in the present invention can be divided into two stages: input judgment and counting comparison. The process starts with module initialization, setting the initial value BAND = N / 2. Subsequently, it is judged according to the input signal status: when LOW = 1 and HIGH = 0, BAND is increased by 1; when LOW = 0 and HIGH = 1, BAND is decreased by 1; when LOW = 0 and HIGH = 0, BAND remains unchanged. After each adjustment of BAND, a counting operation is performed, and it is judged whether the count value is greater than the preset threshold. If the count value is less than the threshold, it returns to the input signal status judgment and repeats the adjustment process; if the count value is greater than the threshold, the process ends.

[0026] Figure 5 Shows the circuit schematic diagram of the voltage-controlled oscillator and its capacitor array of the present invention.

[0027] As Figure 5 shown, the voltage-controlled oscillator 104 in the present invention includes an inductor L, a capacitor array 301, a varactor diode array 302, a cross-coupled pair composed of M1 and M2, and a resistor R. Two transistors M1 and M2 form a cross-coupled pair of NMOS transistors. The gate of M1 is connected to the drain of M2, and the gate of M2 is connected to the drain of M1. The sources of M1 and M2 are connected together and connected to the tail resistor R. The drains of M1 and M2 are respectively connected to the output signals Vop and Von and are connected through an inductor. The voltage VDD is applied to the center tap of the inductor L. The capacitor array 301 is composed of capacitor tube pairs numbered from 1 to N. Each capacitor tube pair includes two NMOS transistors. The gates of the two NMOS transistors are respectively connected to the output signals Vop and Von. The sources and drains of the two NMOS transistors are connected together and connected to the output control signal BAND of the corresponding numbered automatic frequency controller 105. The varactor diode array 302 inputs are connected to the output Vt of the loop filter 103 and the output control signal CTRL of the automatic frequency controller 105, and the output of the varactor diode array 302 is connected to Vop and Von.

[0028] Figure 6 Shows the circuit schematic diagram of the varactor diode array of the voltage-controlled oscillator of the present invention.

[0029] As Figure 6 As shown, the varactor array 302 of the voltage-controlled oscillator of the present invention includes a fixed tuning array 303 and an adjustable tuning array 304. The fixed tuning array 303 is composed of capacitor tube pairs numbered from 1 to X. Each capacitor tube pair includes two NMOS transistors M5 and M6. The gates of the two NMOS transistors are respectively connected to the output signals Vop and Von. The sources and drains of the two NMOS transistors are connected and connected to the output Vt of the loop filter 103. The adjustable tuning array 304 is composed of adjustable tuning units numbered from 1 to Y. Each unit includes two NMOS transistors M7 and M8. The gates of the two NMOS transistors are respectively connected to the output signals Vop and Von. The sources and drains of the two NMOS transistors are connected and connected to two switches EN and ENB. The other side of the switch EN is connected to the output Vt of the loop filter 103. The other side of the switch ENB is connected to the power supply VDD. The two switches are differential complementary switches, and their control signals are connected through an inverter. The control signal CTRL of the automatic frequency controller 105 <m:1>After passing through the LOGIC logic operation unit, it is connected to the switch control signal of the corresponding tunable array 304.

[0030] In this article, the term "including", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a series of elements (such as processes, methods, articles or devices) included not only include those elements, but also other elements not explicitly listed. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements outside the included element.

[0031] In the present invention, the embodiments do not elaborate on all details, nor limit the invention to the specific embodiments described. According to the above description, many changes can be made. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and its modifications based on the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A frequency source integrating an automatic frequency control and a high-linearity voltage-controlled oscillator, characterized in that The circuit structure includes: a phase frequency detector, a charge pump, a loop filter, a voltage controlled oscillator, an automatic frequency controller, and a programmable fractional divider. The signal of the reference frequency and the signal fed back by the programmable divider are input to the phase frequency detector. The phase frequency detector compares the rising edges of the two signals and outputs a pulse signal to the charge pump; the charge pump converts the input pulse signal into a current signal to charge and discharge the loop filter; the loop filter converts the received current signal into a voltage signal and outputs it to the voltage controlled oscillator; the voltage controlled oscillator adjusts the frequency of the output signal according to the input voltage signal and the control word of the automatic frequency controller, and feeds it back to the phase frequency detector through the programmable fractional divider to achieve loop locking.

2. The frequency source integrating an automatic frequency control and a high-linearity voltage-controlled oscillator according to claim 1, characterized in that, The automatic frequency controller includes an analog part of the automatic frequency controller and a digital part of the automatic frequency controller. The analog part of the automatic frequency controller receives the output signal generated by the loop filter, calculates through an operational amplifier to generate a high and low voltage identification signal to the digital part of the automatic frequency controller. The digital part of the automatic frequency controller receives the reference frequency signal and counts, and finally outputs the corresponding capacitor array control signal and varactor array control signal.

3. The frequency source integrating an automatic frequency control and a high-linearity voltage-controlled oscillator according to claim 2, wherein The voltage controlled oscillator contains a pair of cross-coupled transistors as negative resistance transistors, and an inductor with a center tap connected to the power supply is used between the cross-coupled transistors; the inductor is connected in parallel with the capacitor array and the varactor array. The capacitor array and the varactor array are both composed of capacitor tube pairs. Each capacitor tube pair consists of two common source and common drain transistors, and the source and drain are connected and connected to the output of the frequency controller.

4. The frequency source integrating an automatic frequency control and a high-linearity voltage-controlled oscillator according to claim 3, characterized in that The capacitor array is composed of capacitor tube pairs numbered from 1 to N. Each capacitor tube pair includes two NMOS transistors. The gates of the two NMOS transistors are respectively connected to the output signals Vop and Von. The sources and drains of the two NMOS transistors are connected and connected to the output control signal BAND of the corresponding numbered automatic frequency controller. The varactor array of the voltage-controlled oscillator consists of a fixed tuning array and an adjustable tuning array. The input of the varactor array is connected to the output Vt of the loop filter and the output control signal CTRL of the automatic frequency controller, and the output of the varactor array is connected to Vop and Von. The fixed tuning array consists of capacitor pairs numbered from 1 to X. Each capacitor pair includes two NMOS transistors M5 and M6. The gates of the two NMOS transistors are respectively connected to the output signals Vop and Von. The sources and drains of the two NMOS transistors are connected and connected to the output Vt of the loop filter. The adjustable tuning array consists of adjustable tuning units numbered from 1 to Y. Each unit includes two NMOS transistors M7 and M8. The gates of the two NMOS transistors are respectively connected to the output signals Vop and Von. The sources and drains of the two NMOS transistors are connected and connected to two switches EN and ENB. The other side of the switch EN is connected to the output Vt of the loop filter, and the other side of the switch ENB is connected to the power supply VDD. The two switches are differential complementary switches, and their control signals are connected through an inverter. The control signal CTRL of the automatic frequency controller <m:1>After passing through the LOGIC logic operation unit, it is connected to the switch control signal of the corresponding adjustable tuning array.< / m:1>

Images