WO2016155278A1

WO2016155278A1 - Circuit and equipment for quickly locking microwave frequency source

Info

Publication number: WO2016155278A1
Application number: PCT/CN2015/091515
Authority: WO
Inventors: 王崔州; 吴洋; 杨晓东; 吴成林
Original assignee: 成都西蒙电子技术有限公司
Priority date: 2015-04-01
Filing date: 2015-10-09
Publication date: 2016-10-06
Also published as: CN104702276A; CN104702276B

Abstract

A circuit and equipment for quickly locking a microwave frequency source, comprising a sampling phase detector (PD), a loop filter (LF), a preset circuit module, a frequency divider (1/N) and a voltage-controlled oscillator (VCO), wherein the sampling phase detector (PD) is connected to one end of the loop filter (LF); the other end of the loop filter (LF) is connected to the preset circuit module; the other end of the preset circuit module is connected to the voltage-controlled oscillator (VCO); and the voltage-controlled oscillator (VCO) is connected to the sampling phase detector (PD) through the frequency divider (1/N). A change condition from a locking voltage V01 with an original F1 frequency to a tuning voltage V02 with a target frequency F2 is adjusted through preset adjustment; VT in a circuit in the process always keeps constant, such that the charging time of a capacitor is zero, the frequency hopping time is reduced, and a frequency hopping overhead brought by the charging time of the capacitor of the loop filter (LF) in the present scheme is directly solved.

Description

Quick locking microwave frequency source circuit and device

Technical field

The present invention relates to the field of communications, and in particular, to a circuit and device for quickly locking a microwave frequency source.

Background technique

With the development of electronic equipment, electronic systems have placed increasing demands on frequency sources. The microwave phase-locked frequency source technology for obtaining high-quality microwave frequency integrated generators through phase-locking technology has also been greatly developed.

The phase-locked loop (PLL) is shown in Figure 1: including a phase detector (PD), a loop filter (LF), a voltage controlled oscillator (VCO), and a phase detector (PD) that references the input signal (XTAL). The phase is compared with the phase of the voltage controlled oscillator (VCO) signal, and the phase error of the two input signals is converted by the phase detector (PD) into an error voltage, which is filtered by the loop filter and used as a voltage controlled oscillator. (VCO) control voltage, the control voltage changes the output frequency of the voltage controlled oscillator (VCO). When the closed loop system is stabilized, the output frequency of the voltage controlled oscillator (VCO) reaches the required frequency, and the output frequency and reference frequency are completed. Locked. When the output frequency is higher than the reference frequency, it is generally necessary to increase the frequency divider (N) in the feedback branch so that the two signals input to the PD are substantially equal in frequency. Similarly, a reference divider (R) can be used for the reference signal to obtain a smaller phase-detection frequency.

Among all the specifications of the microwave frequency synthesizer, phase noise and frequency hopping time are two core indicators. Among them, the frequency hopping time refers to the conversion time required for the frequency synthesizer to change from one output frequency to another. Generally speaking, the shorter the frequency hopping time, the better the performance of the microwave frequency device; the microwave frequency device with short frequency modulation time has a very large application space in the fields of radar, frequency hopping communication, electronic countermeasures, etc., and the frequency modulation time of the microwave frequency device Shortening is the direction that the skilled person in the field has been working hard to study.

There are many factors affecting the frequency hopping time. The current frequency hopping architecture with the fastest hopping time is direct frequency synthesis (DDS), but direct frequency synthesis (DDS) also has its own shortcomings, such as: complex architecture, large size, high spurs, etc. These shortcomings limit their widespread use in the field of frequency sources. In the frequency synthesizer with phase-locked loop architecture, due to its simple structure, small size, low cost, good phase noise and spurs, it is still the most widely used frequency synthesizer architecture.

In the phase-locked loop architecture, it is difficult to accurately express the frequency hopping time.

Among them, LT is the frequency hopping time, Fc is the loop bandwidth, Ft is the frequency tolerance, which is the difference frequency with the target frequency. Within the frequency range that everyone agrees, the frequency source is determined to be locked. Fj is the hopping frequency, that is, if jumping from F1 to the target frequency F2, then Fj=F2-F1.

It can be seen from the above formula that if the value of the hopping time is to be reduced when the Ft is kept constant, it is necessary to minimize the hopping frequency and maximize the loop bandwidth. Therefore, people have used many methods in these two aspects to try to solve the frequency hopping time of the phase-locked frequency source. In terms of increasing the loop bandwidth, variable loop bandwidth is used to balance the frequency hopping time and the post-locking phase noise index. In terms of reducing the frequency hopping frequency, a preset voltage is used to preset the target frequency of the voltage controlled oscillator (VCO), so that the output frequency approaches the final locking frequency, so that the phase locked loop is in the fast capture band, and the locking time is reduced. .

The existing technical solution mainly uses a voltage controlled oscillator (VCO) to assist the tuning circuit, and the main working principle thereof can be as shown in FIG. 2 . The main working principle is to calculate the approximate tuning voltage by using the known target frequency information combined with the characteristics of the voltage controlled oscillator (VCO). The voltage controlled oscillator (VCO) is used to add the voltage to the voltage controlled oscillator (VCO). The tuning section allows the voltage controlled oscillator (VCO) to be quickly preset to the vicinity of the target frequency, and then switches the circuit to the phase-locked loop circuit to reduce the frequency hopping frequency difference. , reduce the frequency hopping time.

The shortcoming of the above scheme is mainly that when the phase locked loop is locked, the tuning voltage VT of the voltage controlled oscillator (VCO) corresponds to the frequency required for the voltage controlled oscillator (VCO); that is, when the phase locked frequency source needs to jump from F1 To F2, the tuning voltage VT1 corresponding to F1 also changes to the tuning voltage VT2 corresponding to F2; in the prior art, the skip frequency is reduced by the external preset voltage, but the process of tuning the voltage from VT1 to VT2 also takes a certain time. . The reason is that the phase changer drives the tuning voltage change by charging and discharging the capacitor in the loop filter by the phase detector charge pump current. The charge and discharge time of this capacitor (about the order of uS) is in the existing scheme. It is unavoidable and also accounts for the main part of the hopping time.

Summary of the invention

The object of the present invention is to overcome the above-mentioned deficiencies in the prior art, and to provide a fast locking microwave frequency source circuit and device. The preset circuit module is set in a loop filter and voltage control based on the prior art. Between the oscillators, to solve the charging time overhead caused by the tuning voltage VT change in the existing preset scheme, the frequency hopping locking time of the phase-locked frequency synthesizer is further reduced.

In order to achieve the above object, the present invention provides the following technical solution: a fast locking microwave frequency source circuit, comprising: a sampling phase detector, a loop filter, a preset circuit module, a frequency divider, and a voltage controlled oscillator; The sampling phase detector is connected to one end of the loop filter, and the other end of the loop filter is connected to the preset circuit module, and the other end of the preset circuit module and the voltage controlled oscillation The voltage controlled oscillator is connected to the sampling phase detector through a frequency divider.

In operation, the sampling phase detector compares phase information of a signal emitted by the reference source REF with phase information of the voltage controlled oscillator signal, and converts phase errors of the two signals into an error voltage, the error voltage Filtered by the loop filter and input into the preset circuit module, the preset circuit module adjusts the input voltage accordingly, and serves as a control voltage of the voltage controlled oscillator, and the voltage controlled oscillator changes its output according to the control voltage. Frequency, the output frequency of the voltage controlled oscillator when the closed loop system is stable The rate is the desired frequency and the output frequency is locked to the reference frequency. Compared with the prior art, the present invention places a preset circuit into the loop, and adjusts the preset condition to adjust the variation condition of the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2; VT, that is, the charge pump voltage is always kept constant, so that the charging time of the capacitor is zero, which directly solves the frequency hopping overhead caused by the charging time in the existing scheme and reduces the frequency hopping time.

As a preferred, the preset circuit module includes a digital to analog converter and a resistor. An input end of the digital-to-analog conversion module is connected to the loop filter, an output end of the digital-to-analog conversion module is connected to a resistor; and the other end of the resistor is connected to the voltage-controlled oscillator; To the partial pressure and protection, the system's work is more stable.

Further, by adjusting the data of the digital-to-analog conversion module, the variation condition of the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2 is adjusted; and the frequency hopping is adjusted and controlled by the digital-to-analog converter. Corresponding to the control voltage, it has the advantages of short response time and simple control method.

further. The digital-to-analog converter is a parallel-port digital-to-analog converter, and the parallel digital-to-analog converter has a fast transmission speed, which is beneficial to shorten the frequency hopping time; and the parallel control port of the digital-to-analog converter: D11~D15 is used to determine the The voltage value of the output voltage V0 of the preset circuit module.

If the tuning voltage at the F1 frequency is V01 when the phase-locked frequency synthesizer is locked, the linear relationship between VT and V01 is due to the role of the digital-to-analog converter:

V01=A*VT

Here, A is a control coefficient of the digital-to-analog converter, and is determined by the setting data D11 to D15 of the digital-to-analog converter, and the value of A is an arbitrary number between 0 and 1.

When it is necessary to jump the frequency source from F1 to F2, the tuning voltage of the VCO corresponding to the F2 frequency is V02. At this time, due to the role of the digital-to-analog converter, VT and V02 still have a linear relationship:

V02=B*VT

Here, B is a control coefficient of the digital-to-analog converter, and its value is an arbitrary number between 0 and 1, and is determined by the setting data D11 to D15 of the digital-to-analog converter.

Therefore, it can be obtained that, to keep VT constant, then

B=(A*V02)/V01

Thus, it is only necessary to set the new digital-to-analog converter setting values D11 to D15 so that B satisfies the relationship of the equation B=(A*V02)/V01, and the charge pump voltage VT can be kept constant.

Further, the setting values of the digital-to-analog converter control ports D11-D15 are passed through the control module, and the processing chip (for example, the control chip such as an FPGA or an MCU) in the control module calculates the value of B according to the frequency of the jump required. And converted into a binary code, send this code through the parallel port to control the output value of the digital-to-analog converter to achieve the setting of the digital-to-analog converter.

Preferably, the preset circuit module is: a switch resistor network module; and the different voltage presets of the V0 tuning voltage are completed by the switch resistor network in the case that the Vin voltage is not changed; the output through the switch resistor network The voltage adjustment capability is used to adjust the variation condition of the tuning voltage V02 of the original F1 frequency lock voltage V01 to the target frequency F2.

Further, the present invention provides a fast-locking microwave frequency source device, which includes the above-mentioned fast-locking microwave frequency source circuit, which has a shorter frequency modulation time and superior performance than the microwave frequency source device in the prior art.

Compared with the prior art, the present invention provides a fast locking microwave frequency source circuit and device, wherein the fast locking microwave frequency source circuit includes: a sampling phase detector, a loop filter, and a pre- a circuit module, a frequency divider, and a voltage controlled oscillator; wherein the sampling phase detector is connected to one end of the loop filter, and the other end of the loop filter is connected to the preset circuit module The other end of the preset circuit module is connected to the voltage controlled oscillator, and the voltage controlled oscillator is connected to the sampling phase detector through a frequency divider. Compared to the auxiliary tuning circuit used in the prior art, the preset will be preset The circuit is placed in the loop, and the variation condition of the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2 is adjusted by adjusting the preset; in this process, the VT in the circuit, that is, the charge pump voltage is always kept constant, thereby The capacitor charging time of the loop filter is zero, and since there is no charge pump charging time, a small locking time can be maintained regardless of the frequency hopping frequency change. The frequency hopping overhead caused by the charging time in the existing solution is directly solved, and the frequency hopping time is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS:

1 is a prior art phase locked loop circuit structure.

2 is a schematic structural view of a microwave frequency source circuit in the prior art of the present invention.

FIG. 3 is a schematic structural diagram of a fast locking microwave frequency source circuit module according to the present invention.

4 is a schematic structural view of a circuit for quickly locking a microwave frequency source according to the present invention.

FIG. 5 is a schematic diagram of a frequency hopping time test of a fast locked microwave frequency source according to the present invention.

FIG. 6 is a schematic structural diagram of a preset circuit of a switched resistor network.

detailed description

The present invention will be further described in detail below in conjunction with the test examples and specific embodiments. However, the scope of the above-mentioned subject matter of the present invention should not be construed as being limited to the following embodiments, and the technology implemented based on the present invention is within the scope of the present invention.

The invention provides a fast locking microwave frequency source circuit and device, and further reduces the charging time overhead caused by the tuning voltage VT change in the existing preset scheme on the basis of the prior art, thereby further reducing the phase-locked frequency comprehensive source Frequency hop lock time.

In order to achieve the above object, the present invention provides the following technical solution: as shown in FIG. 3, a fast-locking microwave frequency source circuit includes: a sampling phase detector PD, a loop filter LF, and a preset circuit. a module, a frequency divider 1/N, and a voltage controlled oscillator VCO; wherein the sampling phase detector PD is connected to one end of the loop filter LF, and the other end of the loop filter LF and the preset The circuit module is connected, and the other end of the preset circuit module is connected to the voltage controlled oscillator VCO, and the voltage controlled oscillator VCO is connected to the sampling phase detector PD through a frequency divider 1/N.

In operation, the sampling phase detector compares phase information of a signal emitted by the reference source REF with phase information of the voltage controlled oscillator signal, and converts phase errors of the two signals into an error voltage, the error voltage Filtered by the loop filter and input into the preset circuit module, the preset circuit module adjusts the input voltage accordingly, and serves as a control voltage of the voltage controlled oscillator, and the voltage controlled oscillator changes its output according to the control voltage. Frequency, when the closed-loop system is stabilized, the output frequency of the voltage-controlled oscillator reaches the required frequency, and the output frequency is locked with the reference frequency. In the present invention, compared with the prior art, the preset circuit is placed in the loop, and the variation condition of the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2 is adjusted by adjusting the preset; The VT, that is, the charge pump voltage is always kept constant, so that the charging time of the capacitor is zero, which directly solves the frequency hopping overhead caused by the charging time in the existing scheme and reduces the frequency hopping time.

Preferably, as shown in FIG. 4, the preset circuit module includes a digital to analog converter and a resistor. An input end of the digital-to-analog conversion module is connected to the loop filter, and an output end of the digital-to-analog conversion module is connected to a resistor; and the other end of the resistor is connected to the voltage-controlled oscillator.

Further, by changing the data of the digital-to-analog conversion module, the variation condition of the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2 is adjusted.

further. The digital-to-analog converter is a parallel-port digital-to-analog converter, and the voltage value of the output voltage V0 of the preset circuit module is determined by setting parallel control ports of the digital-to-analog converter: D11 to D15.

V01=A*VT

Here, A is an arbitrary number between 0 and 1, and is determined by the setting data D11 to D15 of the digital-to-analog converter.

V02=B*VT

Here, B is an arbitrary number between 0 and 1, and is determined by the setting data D11 to D15 of the digital-to-analog converter.

Therefore, it can be obtained that, to keep VT constant, then

B=(A*V02)/V01

Further, the digital-to-analog converter controls the setting values of the ports D11-D15, and is implemented by a control module (such as an MCU). After the test, the frequency hopping time realized by the circuit device of the present invention is as shown in FIG. 5: the frequency hopping time is reduced to 1.17 uS, which is the optimal frequency hopping time of the current phase-locked loop architecture frequency source.

Preferably, the preset circuit module is: a switch resistor network module; and different voltage presets of the V0 tuning voltage are completed by the switch resistor network in the case that the VT voltage is not changed; and the output voltage of the switch resistor network is adjusted. The ability to adjust the change condition of the tuning voltage V02 of the original F1 frequency lock voltage V01 to the target frequency F2.

The switching resistor network is shown in Figure 6. R = 50KΩ is generally selected. Rl is the equivalent input impedance of the VCO, which is on the order of MΩ.

The output voltage V0 of the switch resistor network is:

Where D indicates the state of each switch. If the switch is connected to VT, D=1, if the switch is connected to ground, D=0. Through the on/off control of different switches, the circuit can achieve voltage stepping:

Voltage regulation.

The preset voltage of the control voltage of the voltage controlled oscillator through the switch resistor network is: the controller module calculates the control voltage V02 of the voltage controlled oscillator corresponding to the target frequency; the controller module controls the switch resistor network to make it The output voltage is V02, so that different voltage presets of the V0 tuning voltage are completed without changing the VT voltage.

In summary, the present invention provides a fast locking microwave frequency source circuit and device, which solves the existing preset scheme by setting a preset circuit module between a loop filter and a voltage controlled oscillator on the basis of the prior art. The frequency-hopping lock time of the phase-locked frequency synthesizer is further reduced due to the charging time overhead caused by the change of the tuning voltage VT. The fast-locking microwave frequency source circuit includes: a sampling phase detector, a loop filter, a preset circuit module, a frequency divider, and a voltage controlled oscillator; wherein the sampling phase detector and the loop filter One end of the loop filter is connected to the preset circuit module, the other end of the preset circuit module is connected to the voltage controlled oscillator, and the voltage controlled oscillator passes through a frequency divider. Connected to the sampling phase detector. Compared with the auxiliary tuning circuit used in the prior art, the preset circuit is placed in the loop, and the variation condition of the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2 is adjusted by adjusting the preset; During the process, the VT in the circuit, that is, the charge pump voltage is always kept constant, so that the charging time of the capacitor is zero. Since there is no charge pump charging time, regardless of the frequency of the frequency hopping frequency, a small locking time can be maintained. The test test uses the circuit device of the present invention to reduce the frequency hopping time to 1.17uS, which is the optimal frequency hopping time of the current phase-locked loop architecture frequency source.

Claims

A fast locking microwave frequency source circuit is characterized in that a preset circuit module is located between a loop filter and a voltage controlled oscillator.
The fast-locking microwave frequency source circuit according to claim 1, wherein the loop filter filters the error voltage and inputs the preset circuit module, and the preset circuit module adjusts the input voltage accordingly. Thereafter, as the control voltage of the voltage controlled oscillator, the voltage controlled oscillator changes its output frequency according to the control voltage. When the closed loop system is stabilized, the output frequency of the voltage controlled oscillator reaches the required frequency, and the output frequency is completed. Lock with reference frequency.
The fast-locking microwave frequency source circuit according to claim 1 or 2, wherein the preset circuit module comprises a digital-to-analog converter and a resistor, and an input end of the digital-to-analog conversion module is connected to the loop filter The output of the digital-to-analog conversion module is coupled to a resistor; the other end of the resistor is coupled to the voltage controlled oscillator.
The fast-locking microwave frequency source circuit according to claim 3, wherein the tuning voltage V02 of the original F1 frequency locking voltage V01 to the target frequency F2 is adjusted by presetting the data of the digital-to-analog conversion module. Changing conditions.
A fast-locking microwave frequency source circuit according to claim 4, wherein said digital-to-analog converter is a parallel-port digital-to-analog converter, and said pre-determination is performed by setting parallel control port data of said digital-to-analog converter Set the voltage value of the output voltage V0 of the circuit module.
The fast-locking microwave frequency source circuit of claim 5, wherein the preset of the digital-to-analog converter control ports D11-D15 is implemented by a control module.
The fast lock microwave frequency source circuit of claim 6 wherein said control module comprises an FPGA or MCU processing chip.
The fast-locking microwave frequency source circuit according to claim 1 or 2, wherein the preset circuit module is a switched resistor network.
A fast-locking microwave frequency source device, comprising: the fast-locking microwave frequency source circuit according to any one of claims 1 to 7.