CN210866768U - High-precision tunable low-phase-noise photo-generated microwave signal generation device - Google Patents
High-precision tunable low-phase-noise photo-generated microwave signal generation device Download PDFInfo
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Abstract
The utility model discloses a high-precision tunable low-phase noise photoproduction microwave signal generating device, which comprises a light source, a narrow-band photon filtering module, a switchable light time delay module, a microwave photon phase shifter, a light beat frequency device, a radio frequency amplifier, a coupler and a light time delay detection and control module; the narrow-band photon filtering module consists of a double parallel Mach-Zehnder modulator, a circulator and a Bragg grating; the switchable light delay module consists of a polarization splitter, a controllable light delay line and a polarization combiner. The utility model discloses utilize the method of optic fibre energy storage and the real delay of wireless light to realize that frequency tunable precision, stability, phase noise all obviously are superior to a novel photoelectric oscillation source of conventional microwave dielectric oscillator to promote performances such as radar system's clutter visibility, speed measurement precision, speed resolution, provide technical support for photoelectric oscillator's weaponry engineering application.
Description
Technical Field
The utility model relates to a microwave signal generating device technical field, concretely relates to photo-generated microwave signal generating device of high accuracy tunable low phase noise.
Background
With the increasing demand of microwave systems such as doppler radar, satellite communication and satellite navigation for low phase noise microwave signals, the performance of the existing microwave device is difficult to meet the future development demand. For example, in an onboard radar, in order to improve the detection capability of the radar, a high-purity microwave local oscillation source is needed to generate a fully coherent pulse doppler radar signal, and the phase noise of the microwave signal is required to reach-110 dBc @1kHz or even lower.
A microwave oscillator is a core component of a microwave signal generator, and a high-Q oscillator with low loss and long energy storage time is often required to generate a microwave signal with high spectral purity. While conventional oscillators basically employ a microwave energy storage element (e.g., a dielectric cavity oscillator) or an acoustic energy storage element (e.g., a quartz oscillator). Since the optimum working frequency of the dielectric cavity oscillator is 8GHz, the higher frequency to be obtained can only be generated by a frequency doubling method, and the frequency doubling can cause the phase noise performance of the generated microwave signal to be obviously reduced. Therefore, in the conventional microwave signal generation method, the dielectric oscillator is often not satisfactory under the conditions of low noise, high spectral purity or tunable performance. The quartz crystal oscillator can obtain a high quality factor (Q value), but the local oscillator output is only 10-20MHz magnitude, a high-frequency signal cannot be directly obtained, and the quartz crystal oscillator is suitable as a reference clock. Although the quartz crystal oscillator can obtain high-frequency signal output by frequency conversion such as frequency multiplication, the phase noise will be seriously deteriorated. Generally, the frequency is increased by 10 times, and the phase noise is deteriorated by 20dB, so that the microwave signal obtained by the quartz crystal oscillator through the frequency doubling method cannot be directly applied to the occasions of radio frequency local oscillators requiring low phase noise, such as radars, electronic warfare and the like. In addition, the microwave energy storage element and the acoustic energy storage element can only work in frequency bands below several GHz, the frequency quality factor product is approximately constant, and the capacity is limited. When the frequency of the signal is higher than 10GHz, the quality factors of the two types of resonators are rapidly reduced, and the deterioration of the phase noise performance is relatively serious.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve is that the frequency quality factor and the phase noise of the produced microwave signal of current microwave oscillator are difficult to satisfy the problem of future development demand, provides a high accuracy tunable low phase noise photoproduction microwave signal generating device.
In order to solve the above problems, the utility model discloses a realize through following technical scheme:
the high-precision tunable low-phase-noise photoproduction microwave signal generation device comprises a light source, a narrow-band photon filtering module, a switchable light time delay module, a microwave photon phase shifter, a light beat frequency device, a radio frequency amplifier, a coupler and a light time delay detection and control module; the narrow-band photon filtering module consists of a double parallel Mach-Zehnder modulator, a circulator and a Bragg grating; the switchable light delay module consists of a polarization splitter, a controllable light delay line and a polarization combiner.
The output end of the light source is connected with the light input end of the double-parallel Mach-Zehnder modulator, the light output end of the double-parallel Mach-Zehnder modulator is connected with the first port of the circulator, the Bragg grating is connected with the second port of the circulator, and the third port of the circulator is connected with the input end of the polarization splitter; the output end of the polarization splitter is connected with the input end of the controllable light delay line, the output end of the controllable light delay line is connected with the input end of the polarization combiner, and the output end of the polarization combiner is connected with the input end of the microwave photon phase shifter; the output end of the microwave photon phase shifter is connected with the input end of the optical beat frequency device, and the output end of the optical beat frequency device is connected with the input end of the radio frequency amplifier; the output end of the radio frequency amplifier is connected with the input end of the coupler, one output end of the coupler is connected with the electrical input end of one arm of the double-parallel Mach-Zehnder modulator, and the other output end of the coupler forms the microwave signal output end of the microwave signal generating device.
One input end of the optical time delay detection and control module is connected with the input end of the polarization splitter, and the other input end of the optical time delay detection and control module is connected with the output end of the polarization combiner; the coarse regulation control output end of the optical time delay detection and control module is connected with the control end of the controllable optical time delay line, and the fine regulation control output end of the optical time delay detection and control module is connected with the control end of the microwave photon phase shifter.
In the above scheme, the controllable optical delay line adopts a photonic crystal fiber as a resonant cavity.
In the above scheme, the light source is a wavelength-tunable laser.
Compared with the prior art, the utility model discloses a controllable light time delay line, microwave photon move the looks ware and light time delay detection and control module mutually support and form feedback loop, adjust fine solution OEO frequency along with the problem of external factors drift to energy storage optic fibre time delay based on the PID algorithm again. The utility model discloses frequency stability can reach 10-10(4h) The generated frequency range is 1 GHz-40 GHz, the frequency resolution reaches 1Hz, and the phase noise reaches: -135dBc/Hz (10kHz offset); -115dBc/Hz (1kHz offset); -90dBc/Hz (100Hz frequency offset); 60dBc/Hz (10Hz frequency offset).
Drawings
FIG. 1 is a schematic diagram of a high-precision tunable low-phase noise photo-generated microwave signal generating device.
Fig. 2 is a diagram of a spectrum of a DPMZM (dual parallel mach-zehnder modulator) after modulation.
Fig. 3 is a graph of single sideband filtering and frequency response.
FIG. 4 is a schematic block diagram of the PID algorithm.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following specific examples.
The utility model provides a tunable low phase noise photoproduction microwave signal generating device of high accuracy, as shown in figure 1, including light source, narrowband photon filtering module, switchable light time delay module, microwave photon looks ware, light beat frequency ware, radio frequency amplifier and coupler and light time delay detection and control module component. The light source is a wavelength-tunable laser. The narrow-band photon filtering module consists of a double parallel Mach-Zehnder modulator, a circulator and a Bragg grating. The switchable light delay module consists of a polarization splitter, a controllable light delay line and a polarization combiner.
The output end of the light source is connected with the input end of the double-parallel Mach-Zehnder modulator, the output end of the double-parallel Mach-Zehnder modulator is connected with the first port of the circulator, the Bragg grating is connected with the second port of the circulator, and the third port of the circulator is connected with the input end of the polarization splitter. The output end of the polarization splitter is connected with the input end of the controllable light delay line, the output end of the controllable light delay line is connected with the input end of the polarization combiner, and the output end of the polarization combiner is connected with the input end of the microwave photon phase shifter. The output end of the microwave photon phase shifter is connected with the input end of the optical beat frequency device, and the output end of the optical beat frequency device is connected with the input end of the radio frequency amplifier. The output end of the radio frequency amplifier is connected with the input end of the coupler, one output end of the coupler is connected to one arm of the double parallel Mach-Zehnder modulator, and the other output end of the coupler forms the microwave signal output end of the microwave signal generating device.
One input end of the optical time delay detection and control module is connected with the input end of the polarization splitter, and the other input end of the optical time delay detection and control module is connected with the output end of the polarization combiner. The coarse regulation control output end of the optical time delay detection and control module is connected with the control end of the controllable optical time delay line, and the fine regulation control output end of the optical time delay detection and control module is connected with the control end of the microwave photon phase shifter.
The utility model discloses a wavelength tunable laser, DPMZM realize OEO frequency adjustable optoelectronic oscillator system with the cooperation of narrowband photon filter, adopt light time delay to detect in addition and the cooperation of the wireless light controllable delay line of control module and VDL, utilize the PID algorithm to float the microwave signal frequency that the system produced and carry out automatically regulated to reached the produced signal of optoelectronic oscillator when keeping low phase noise characteristic, possessed the characteristics that the high accuracy is adjustable and high stability again.
The utility model discloses its rationale is: continuous light output by the wavelength-tunable laser is subjected to phase modulation by the DPMZM, so that optical signals with equal amplitude and opposite phases are formed on two sides of an optical carrier, the optical signals subjected to the phase modulation are subjected to single-sideband photonic filtering through the Bragg grating, so that modulation from the phase to the intensity is completed, the optical signals enter the optical beat frequency device through the high-precision phase shifter after being subjected to switchable optical time delay transmission, the optical beat frequency device converts the optical signals into electric signals and then the electric signals are fed back to an electric input end of the DPMZM modulator through electric amplification to complete one cycle. Therefore, only the microwave resonance mode within the band-pass range of the filter can obtain effective oscillation, and after multiple cycles, the signal becomes exponentially larger, thereby achieving the purpose of generating microwave light. This structure enables self-sustained oscillation at a specific frequency determined by the length of the fiber, the laser wavelength and the bandpass characteristics of the filter. When the system is subjected to frequency drift caused by external factors, the optical delay detection and control module can detect the optical fiber delay variation and then is matched with the microwave photon phase shifter to form feedback. And the optical time delay of the system is adjusted by adopting a PID algorithm, so that the capability of automatically stabilizing the frequency is realized.
The utility model discloses a mixed technological means of photoelectricity, key breakthrough optoelectronic oscillator's single mode operation technique, restrain phase noise technique based on polarization state control, frequency adjustable microwave photon filter technique, key technologies such as microwave photon phase shift technique, a photoelectric oscillator who has high Q value, low phase noise, easy tune is proposed, satisfy satellite communication system to local oscillator performance's requirement, promote radar system's clutter visibility, the precision tests the speed, performance such as speed resolution, provide technical support for photoelectric oscillator's weaponry engineering application.
The wavelength tunable light source, the DPMZM and the optical trap filter (including the Bragg grating and the circulator) form a single-sideband microwave photonic filter with tunable frequency. The wavelength tunable light source outputs light to a DPMZM (double parallel Mach-Zehnder modulator) for phase modulation, and sidebands with the same amplitude and opposite phases are generated on both sides of the carrier wave on the spectrum. However, such optical signal is unable direct production microwave signal, for this reason, the utility model discloses the optical signal that has passed the phase modulation passes through sideband of optical trap filter filtering again, has just so broken the balance that exists the range the same, the opposite side band of phase place at the carrier wave both sides to realized the modulation of phase place to intensity, the frequency that its produced is exactly the difference frequency of narrowband photon filter's central frequency point and light carrier, thereby keep the unchangeable wavelength that only changes the light source of central frequency point of optical trap filter, different wavelength just can correspond and produce different frequencies.
When the wavelength-tunable light source inputs an optical carrier into the DPMZM, for the upper arm of the DPMZM, no electric signal is loaded, and only the direct-current voltage DC is loaded1By regulating DC1To adjust the optical power of the optical carrier modulated by MZM 1. For the lower arm of the DPMZM, we load the DC voltage DC2To MZM2 and loads the RF signal onto MZM 2. By regulating DC2Is such that MZM2 operates in the carrier-suppressed double sideband mode, i.e., the DSB-CS mode. The optical carrier wave modulated by MZM2 enters a DC loaded direct current voltage3The phase shifter PS. The effect of adding the phase shifter PS here is to produce a phase shift θ between the two sidebands of the electrical signal-added carrier suppressed dual-sideband optical signal modulated by MZM23The phase difference of (1). By regulating DC3The voltage value of (a) is such that a phase difference theta is generated between the two sidebands3And finally, coupling the signals of the two arms together to obtain a signal finally modulated by the DPMZM. If the phase shift θ is caused by PS3Pi/2, the output signal of the DPMZM can be equivalent to the output signal of the phase modulator, but its optical carrier power is also phase modulated.
Let the optical carrier electric field expression be:
wherein E is0、ωcRespectively, optical carrier amplitude and phase. The RF signal loaded onto MZM2 is expressed as:
Ein(t)＝Vecos(ωet) (2)
wherein, VeBeing the amplitude, omega, of the electrical signaleIs the frequency of the electrical signal.
The optical field output from the DPMZM can be represented as:
to enable MZM2 to reject the optical carrier, θ needs to be made2Pi/2. And when theta3At pi/2, the RF signal loaded onto MZM2 is expressed as:
the spectrum diagram of the DPMZM modulated optical signal on both sides of the optical carrier is shown in FIG. 2, where ω iscIs a carrier wave, ωc-ωe、ωc+ωeRespectively-1 +1 order sidebands, as can be seen in fig. 2: two sidebands with the same amplitude and opposite phases are formed in the carrier wave by phase modulation, and an RF signal cannot be directly detected when the phase modulation signal is directly input into the PD at this time according to the photoelectric detection principle. In order to obtain the information of the RF signal loaded on the optical carrier, we need to process the phase modulation signal so that the PD directly detects the microwave signal information, which is equivalent to a single bandpass filtering. This allows the phase modulated signal to be detectedThis process is called IM-PM, i.e. phase to intensity conversion.
The utility model discloses a super narrow optics trapped wave filtering comes a sideband of filtering phase modulation signal to break amplitude balance, realize single band-pass filtering. As shown in fig. 3. When the optical carrier passes through the filter, a first-order sideband is correspondingly considered, so that the relation that the phases are opposite and the amplitudes are the same is broken, and the spectrum generates corresponding frequency after passing through the photoelectric detector. The relative positions of the wavelength and the optical trap filter are adjusted to obtain different frequencies, so that the phase-to-intensity conversion is realized, and finally, the microwave photon single-sideband filter with the adjustable central frequency is realized. Frequency tunability is achieved for our optoelectronic oscillator. But due to device considerations, the wavelength of the light source is currently tuned in steps of 1pm, approximately equal to 125 MHz. The adjustable range can reach 0-2 nm.
The short term stability of the opto-electronic oscillator is typically expressed in terms of the degree of drift of the signal frequency over time from the center frequency and the allen equation. This can be described by the following equation:
where k is the frequency stability of the opto-electronic oscillator over time, f0Is the center frequency, f, of the optoelectronic oscillator1Is the frequency value farthest from the center frequency within a certain time, and Δ f is the maximum value of the frequency change within a certain time.
The stability of optoelectronic oscillator is mainly by the stability decision of oscillator optical fiber ring time delay, the utility model discloses controllable light delay line uses the temperature insensitive photonic crystal optic fibre as the resonant cavity. The temperature sensitivity of the photonic crystal fiber is reduced by one third compared with the common fiber, and the stability of the generated microwave signal is improved by at least three times.
Due to the change of the environmental temperature and the environmental vibration, the time delay amount of the optical signal transmission in the optical fiber ring of the switchable optical time delay module can drift, so that the frequency drift generated by the photoelectric oscillator is caused. In order to improve the system stability on the basis of obtaining adjustable frequency, the utility model discloses a controllable light delay line and microwave photon move the looks ware combination and realize that the microwave photon moves the phase, wherein realize the optical path time delay coarse adjustment of whole device with the control of controllable light delay line, move the optical path time delay fine tuning that realizes whole device with the microwave photon phase to realize the fine stable regulation of frequency of whole microwave signal generating device.
The optical time delay detection and control module detects the optical fiber loop time delay amount of the current switchable optical time delay module, calculates the phase to be moved according to the detected time delay amount, and then adjusts the optical path of the controllable optical time delay line and the microwave photon phase shifter by controlling the high-precision stepping motor, so that the optical time delay of the system is changed in the optical domain, and finally, the generated microwave signal is stable and the resolution is high and precision is adjustable.
The oscillation frequency of the ring cavity can be known from the mechanism of the photoelectric oscillator:
f＝k/τ (6)
where k is 0, 1, 2, 3, τ is determined by the least common multiple of the two-ring cavity, and the oscillation frequency after passing through the phase shifter due to Δ τ is expressed as:
f＝k/(τ+Δτ) (7)
the frequency resolution Δ f can be expressed as:
Δf＝k[Δτ/τ(τ+Δτ)](8)
at present, the adjustment precision of the wireless optical controllable delay line can reach 15fs, so the minimum delta tau can be 15fs, and tau is us magnitude, so the frequency resolution is very high, for example, if a ring cavity is used for using 1km optical fiber, the frequency resolution delta f can reach 0.6 Hz.
The frequency of the microwave generated by the system is determined by the optical time delay of the system, when the frequency of the microwave needs to be set, only the length of a controllable optical time delay line needs to be set, the controllable optical time delay line consists of an optical switch and photonic crystal fibers with different lengths, and different optical time delay is generated by switching different optical switches, so that different microwave frequencies are generated.
The optical time delay detection and control module measures the current time delay amount in an optical signal injection, following and feedback mode, the optical signal emitted by the optical time delay detection and control module and the optical signal of the system are transmitted in the same optical path in an optical wavelength division multiplexing mode, so that the following detection of the time delay is achieved, when the optical path of the system is influenced by external factors such as external temperature, stress and the like to generate no time delay amount, the optical time delay detection and control module controls a controllable optical time delay line and a microwave photon phase shifter through a proportion-integration-differential feedback mode through a PID algorithm to adjust the time delay amount, and the time delay amount is kept consistent with an initial set value. In addition, if the time delay precision of the controllable optical delay line does not meet the requirement, the controllable optical delay line and the microwave photon phase shifter can be controlled to adjust through the optical delay detection and control module. The schematic block diagram of the PID algorithm is shown in fig. 4, and the control formula is:
wherein upsilon (t) is a control quantity.
The utility model discloses use and detect the stability that adds the mode guarantee optical fiber ring time delay of compensation, because light time delay detection and control module are real-time detection, cause the time delay drift because of the factor of environment when the optical fiber ring, can automatic control light controllable time delay line and microwave photon move the looks ware through automatic control PID algorithm and carry out corresponding regulation to the microwave signal that makes the production remains stable when can meticulous regulation. Furthermore, the utility model discloses the method that utilizes optic fibre energy storage and wireless light true delay realizes that frequency tunable precision, stability, phase noise all obviously are superior to a novel photoelectric oscillation source of conventional microwave dielectric oscillator to promote performances such as radar system's clutter visibility, speed measurement precision, speed resolution, provide technical support for photoelectric oscillator's weaponry engineering application.
It should be noted that, although the above-mentioned embodiments of the present invention are illustrative, the present invention is not limited thereto, and therefore, the present invention is not limited to the above-mentioned embodiments. Other embodiments, which can be made by those skilled in the art in light of the teachings of the present invention, are considered to be within the scope of the present invention without departing from the principles thereof.
Claims (3)
1. The high-precision tunable low-phase-noise photoproduction microwave signal generation device is characterized by comprising a light source, a narrow-band photon filtering module, a switchable light time delay module, a microwave photon phase shifter, a light beat frequency device, a radio frequency amplifier, a coupler and a light time delay detection and control module; the narrow-band photon filtering module consists of a double parallel Mach-Zehnder modulator, a circulator and a Bragg grating; the switchable light delay module consists of a polarization splitter, a controllable light delay line and a polarization combiner;
the output end of the light source is connected with the light input end of the double-parallel Mach-Zehnder modulator, the light output end of the double-parallel Mach-Zehnder modulator is connected with the first port of the circulator, the Bragg grating is connected with the second port of the circulator, and the third port of the circulator is connected with the input end of the polarization splitter; the output end of the polarization splitter is connected with the input end of the controllable light delay line, the output end of the controllable light delay line is connected with the input end of the polarization combiner, and the output end of the polarization combiner is connected with the input end of the microwave photon phase shifter; the output end of the microwave photon phase shifter is connected with the input end of the optical beat frequency device, and the output end of the optical beat frequency device is connected with the input end of the radio frequency amplifier; the output end of the radio frequency amplifier is connected with the input end of the coupler, one output end of the coupler is connected with the electrical input end of one arm of the double-parallel Mach-Zehnder modulator, and the other output end of the coupler forms the microwave signal output end of the microwave signal generating device;
one input end of the optical time delay detection and control module is connected with the input end of the polarization splitter, and the other input end of the optical time delay detection and control module is connected with the output end of the polarization combiner; the coarse regulation control output end of the optical time delay detection and control module is connected with the control end of the controllable optical time delay line, and the fine regulation control output end of the optical time delay detection and control module is connected with the control end of the microwave photon phase shifter.
2. The high-precision tunable low-phase-noise photo-generated microwave signal generation device as claimed in claim 1, wherein the controllable optical delay line uses a photonic crystal fiber as a resonant cavity.
3. The high accuracy tunable low phase noise photo-generated microwave signal generating device as claimed in claim 1, wherein the light source is a wavelength tunable laser.
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| CN110943362A (en) * | 2019-12-23 | 2020-03-31 | 中国电子科技集团公司第三十四研究所 | High-precision tunable low-phase-noise photo-generated microwave signal generation device and method |
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| CN110943362B (en) * | 2019-12-23 | 2024-08-20 | 中国电子科技集团公司第三十四研究所 | High-precision tunable low-phase-noise photo-generated microwave signal generating device and method |
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