A high-quality broadband microwave signal generation method based on double injection locking

Abstract

The invention relates to a high-quality broadband microwave signal generation method based on double injection locking, and relates to the technical field of microwave photon signal generation. The method comprises the following steps: performing signal intensity modulation on light output by a laser at an intensity modulator; dividing the signal modulated by the intensity modulator into two branch signals via a first optical coupler, and transmitting the signals in two loops respectively; transmitting the signals output from the two loops to a second electric coupler via a first electric coupler, and then dividing the signals into two signals again; the second electric coupler transmits one signal to an electric spectrum analyzer and a digital storage oscilloscope for analysis, and the second electric coupler inputs another signal into a radio frequency port of the intensity modulator to close an optoelectronic oscillator loop, thereby generating an ultra-wideband linear frequency modulation signal with low phase noise performance, and externally injecting a broadband linear frequency modulation signal to improve the phase noise performance of the linear frequency modulation signal near the carrier frequency and far from the carrier frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave photon signal generation, and in particular to a high-quality broadband microwave signal generation method based on double injection locking. Background Art

[0002] Optoelectronic oscillators (OEOs) are widely used in radar, sensing, signal processing and communication systems because they can generate microwave signals with high frequency, low phase noise, high spectrum purity and high stability. Among many characteristics, the phase noise of the signal is an extremely important performance indicator to measure the performance of an OEO system. Injection locking technology has attracted widespread attention in significantly improving the phase noise performance. Injection locking is mainly achieved by injecting a microwave signal into the loop to phase-lock the oscillation loop, reducing the phase interference of the oscillation signal during transmission, so that the oscillation loop can easily maintain the phase-locked state. Injection locking technology is divided into self-injection, mutual injection and external injection locking. Self-injection locking technology locks the oscillation loop of the OEO system by coupling a part of the signal from the oscillation loop to the injection loop. It uses the long delay characteristics and phase matching of the injection loop to achieve self-injection locking, which is used to improve the phase noise performance of the signal at far carrier frequencies; mutual injection locking is the mutual injection locking of two oscillating OEO loops. Since the frequency of the mutual injection signal is always the same as the oscillation signal, the two oscillation loops are mutually phase-locked, reducing the phase interference of the oscillation signal and maintaining the phase-locked state of the oscillation loop. External injection locking mainly uses an ultra-stable crystal oscillator RF signal source to inject into the OEO system, lock the oscillation mode of the loop, and improve the phase noise near the carrier frequency.

[0003] Chinese Patent Publication No.: CN102082610B discloses a self-injection locking light source, including: a polarization beam splitter, and a first self-injection locking laser and a second self-injection locking laser coupled to the polarization beam splitter; the polarization beam splitter is used to polarization couple the polarized light provided by the first and second self-injection locking lasers, and polarization split the received reflected light and provide it to the first and second self-injection locking lasers respectively; wherein the polarization directions of the first self-injection locking laser and the second self-injection locking laser are respectively aligned with the two polarization directions of the polarization beam splitter. The embodiment of the present invention also provides a method and system for self-injection locking of a light source, as well as a wavelength division multiplexing passive optical network system; it can be seen that the self-injection locking light source is only two self-injection locks, and the near-carrier and far-carrier performance improvement rate of the signal phase noise is not high. Summary of the invention

[0004] To this end, the present invention provides a high-quality broadband microwave signal generation method based on dual injection locking, so as to overcome the problem that the self-injection locking light source in the prior art is only two self-injection locks, and the near-carrier and far-carrier performance improvement rate of the signal phase noise is not high.

[0005] To achieve the above object, the present invention provides a high-quality broadband microwave signal generation method based on double injection locking, comprising:

[0006] Step S1, modulating the signal intensity of the light output by the laser at the intensity modulator;

[0007] Step S2, dividing the signal modulated by the intensity modulator into two branch signals through a first optical coupler, and transmitting them in two loops respectively;

[0008] Step S3, transmitting the signals output from the two loops to the second electric coupler via the first electric coupler and then dividing them into two signals again;

[0009] Step S4: the second electrical coupler transmits one signal to the electrical spectrum analyzer and the digital storage oscilloscope for analysis, and the second electrical coupler inputs another signal into the RF port of the intensity modulator to close the optoelectronic oscillator loop.

[0010] Furthermore, in the step S2, the signal is divided into two branches by the first optical coupler and transmitted respectively via a first delay line and a second delay line.

[0011] Furthermore, in the step S2, the signal of the oscillation loop of the first delay line is matched with the delay of the injection loop through the optical adjustable delay line after the optical power of the branch is adjusted by the optical attenuator.

[0012] Furthermore, in the step S2, the oscillation loop signal is converted into a microwave signal through the first photodetector after passing through the optically adjustable delay line.

[0013] Furthermore, in the step S2, the signal injected into the loop of the second delay line is converted into a microwave signal through the second photodetector after the optical power of the branch is adjusted by the optical attenuator.

[0014] Furthermore, in step S3, the microwave signal transmitted to the second electric coupler via the first electric coupler is amplified by an electric amplifier, filtered by a bandpass filter, and then divided into two signals by the second electric coupler.

[0015] Furthermore, in the step S2, the signal injected into the loop is attenuated by the second optical attenuator until it remains smaller than an oscillation threshold.

[0016] Compared with the prior art, the beneficial effect of the present invention lies in that the present invention mainly utilizes the self-injection locking and external injection locking technologies at the same time, and greatly improves the near-carrier frequency and far-carrier frequency performance of the signal phase noise at the same time, and on the basis of this structure, generates an ultra-wideband linear frequency modulation (LFM) signal with low phase noise performance, that is, on the basis of the self-injection locking operation, a broadband linear frequency modulation signal is externally injected, and the OEO characteristics are utilized to improve the phase noise performance of the linear frequency modulation signal near the carrier frequency and far from the carrier frequency, and a low-phase noise linear frequency modulation waveform with arbitrary center frequency and bandwidth can be generated, and the linear frequency modulation waveform with a large time-bandwidth product has broader application prospects in technical fields such as radar detection and communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of the high-quality broadband microwave signal generation method based on double injection locking according to the present invention;

[0018] Figure 2 It is a schematic structural diagram of the high-quality broadband microwave signal generation system based on double injection locking described in the present invention. DETAILED DESCRIPTION

[0019] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0021] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0022] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] See also Figure 1 As shown, it is a flow chart of the high-quality broadband microwave signal generation method based on double injection locking according to the present invention.

[0024] The high-quality broadband microwave signal generation system based on double injection locking described in the embodiment of the present invention includes:

[0025] Step S1, modulating the signal intensity of the light output by the laser at the intensity modulator;

[0026] Step S2, dividing the signal modulated by the intensity modulator into two branch signals through a first optical coupler, and transmitting them in two loops respectively;

[0027] Step S3, transmitting the signals output from the two loops to the second electric coupler via the first electric coupler and then dividing them into two signals again;

[0028] Step S4: the second electrical coupler transmits one signal to the electrical spectrum analyzer and the digital storage oscilloscope for analysis, and the second electrical coupler inputs another signal into the RF port of the intensity modulator to close the optoelectronic oscillator loop.

[0029] In the high-quality broadband microwave signal generating system based on double injection locking described in the embodiment of the present invention, in the step S2, the signal is divided into two branches by the first optical coupler and transmitted respectively via the first delay line and the second delay line.

[0030] In the high-quality broadband microwave signal generating system based on double injection locking described in the embodiment of the present invention, in the step S2, the signal of the oscillation loop through the first delay line adjusts the optical power of the branch through the optical attenuator, and then matches the delay of the injection loop through the optical adjustable delay line.

[0031] In the high-quality broadband microwave signal generating system based on double injection locking described in the embodiment of the present invention, in the step S2, the oscillation loop signal is converted into a microwave signal through the first photodetector after passing through the optical adjustable delay line.

[0032] In the high-quality broadband microwave signal generating system based on double injection locking described in the embodiment of the present invention, in the step S2, the signal of the injection loop through the second delay line is converted into a microwave signal through the second photodetector after the optical power of the branch is adjusted by the optical attenuator.

[0033] In the high-quality broadband microwave signal generating system based on double injection locking described in the embodiment of the present invention, in the step S3, the microwave signal transmitted to the second electric coupler via the first electric coupler is amplified by the electric amplifier, filtered by the bandpass filter, and then divided into two signals by the second electric coupler.

[0034] In the high-quality broadband microwave signal generating system based on double injection locking described in the embodiment of the present invention, in the step S2, the signal of the injection loop is attenuated by the second optical attenuator to remain less than an oscillation threshold.

[0035] See also Figure 2 As shown, it is a structural schematic diagram of the high-quality broadband microwave signal generating system based on double injection locking according to the present invention.

[0036] Specifically, the light output by the laser is intensity modulated at the intensity modulator, and is divided into two branch signals through an optical coupler at the output end of the intensity modulator, and transmitted in two loops respectively, wherein optical attenuators are introduced in both loops to adjust the optical power of the loop, and an optically adjustable delay line is also introduced into the oscillation loop 1 to match the delay of the injection loop, and the two branch signals are converted into microwave signals through a photodetector. Then, they are amplified by an electrical amplifier and filtered through a bandpass filter, and then divided into two signals through an electrical coupler, one of which is transmitted to an electrical spectrum analyzer (ESA) and a digital storage oscilloscope (OSC) for analysis, and the other is coupled with the output signal from an external RF signal source and input into the RF port of the intensity modulator to close the OEO loop.

[0037] In order to achieve self-injection locking, the optical attenuator is adjusted in the injection loop to keep the loop power below the oscillation threshold, ensuring that the signal of the loop does not oscillate, while the oscillation loop is in a free oscillation state. The phase matching of the injection loop is achieved by adjusting the optical adjustable delay line to achieve the self-injection locking effect. The external injection locking is achieved by coupling a linear frequency modulation signal whose center frequency and bandwidth match the loop bandpass filter and whose period matches the loop delay to the RF port of the intensity modulator to achieve external injection locking. By adjusting the bandwidth and center frequency of the filter used, a linear frequency modulation signal with an arbitrary center frequency and a large time-bandwidth product of ultra-wideband can be generated to meet the needs of different fields such as radar and communication detection.

[0038] The present invention is not only applicable to generating a linear frequency modulation waveform with a large time-bandwidth product and low phase noise of arbitrary center frequency and bandwidth based on injection locking technology, but also applicable to generating a single-frequency microwave signal with low phase noise and high side mode suppression ratio based on an optoelectronic oscillator.

[0039] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-quality broadband microwave signal generation method based on double injection locking, characterized in that: include: Step S1, modulating the signal intensity of the light output by the laser at the intensity modulator; Step S2, dividing the signal modulated by the intensity modulator into two branch signals through a first optical coupler, and transmitting them in two loops respectively; In the step S2, the first optical coupler is used to divide the signal into two branches, and the two branches are respectively transmitted through the first delay line and the second delay line; In the step S2, the signal of the oscillation loop of the first delay line is matched with the delay of the injection loop through the optical adjustable delay line after adjusting the optical power of the branch through the first optical attenuator; In the step S2, the oscillation loop signal is converted into a microwave signal through the first photodetector after passing through the optically adjustable delay line; In the step S2, the signal injected into the loop of the second delay line is converted into a microwave signal through the second photodetector after the optical power of the branch is adjusted by the second optical attenuator; In the step S2, the signal injected into the loop is attenuated by the second optical attenuator until it remains less than an oscillation threshold; Step S3, transmitting the signals output from the two loops to the second electric coupler via the first electric coupler and then dividing them into two signals again; In the step S3, the microwave signal transmitted to the second electric coupler via the first electric coupler is amplified by an electric amplifier, filtered by a bandpass filter, and then divided into two signals by the second electric coupler; Step S4: the second electrical coupler transmits one signal to the electrical spectrum analyzer and the digital storage oscilloscope for analysis, and the second electrical coupler inputs another signal into the RF port of the intensity modulator to close the optoelectronic oscillator loop.

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