CN112448766B - Multi-octave microwave transmission device and multi-octave microwave transmission method - Google Patents
Multi-octave microwave transmission device and multi-octave microwave transmission method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
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Abstract
The invention provides a multi-octave microwave transmission device, which comprises: an optical source for generating and outputting an optical carrier; a signal modulation unit for receiving the optical carrier and the microwave signal to be transmitted, and for being in a predetermined modulation state under the condition of being applied with a predetermined bias voltage, and for modulating the microwave signal to be transmitted onto the optical carrier under the predetermined modulation state to form a modulated optical signal; a photodetector for converting the modulated optical signal into an electrical signal; and in the preset modulation state, the signal modulation unit can inhibit distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state with a preset spurious-free dynamic range. The invention also provides a multi-octave microwave transmission method.
Description
Technical Field
The invention belongs to the technical field of signal transmission, and particularly relates to a multi-octave microwave transmission device and a multi-octave microwave transmission method.
Background
The multi-octave microwave transmission link is an important microwave transmission means. Because of the large spurious-free dynamic range (SFDR), the broadband microwave signal can be transmitted in a high linearity in a multi-octave state, and the broadband microwave signal can be widely applied to antenna remote systems, cable television systems, wireless communication systems and military radar systems. For example, in a communication system, transmission of microwave signals using multiple octave links means a larger transmission capacity; in radar systems, multi-octave microwave transmission may enable higher resolution.
In a multi-octave microwave transmission link, as the bandwidth of an input signal increases, in addition to a third-order distortion term dominated by third-order intermodulation distortion (IMD 3), a second-order distortion term dominated by second-order intermodulation distortion (IMD 2) and second-harmonic distortion (SHD) exists in the working bandwidth of the signal, and the second-order distortion term is difficult to filter by a filter; in addition, IMD2 and SHD deteriorate the SFDR of the system more sharply than IMD3, and when the microwave transmission link is operated in a transmission state of multiple octaves, the SFDR of the system is lowered although the operation bandwidth of the link can be increased. Thus, how to simultaneously inhibit IMD2, SHD, and IMD3 to increase SFDR becomes a challenge for multi-octave microwave transmission links.
The microwave photon technology can complete the transmission of microwave signals in the optical domain, has the advantages of electromagnetic interference resistance, large bandwidth, low loss, compatibility with optical communication technology and the like, and has been widely used for transmitting microwave signals to realize a microwave photon transmission link. In the microwave photon transmission link, multi-octave microwave signal transmission can be realized as well, and a plurality of related technologies have been proposed. However, in these techniques, a balance detector is often used to counteract IMD2 and SHD; or some signal processing in the electrical domain using a broadband radio frequency device, such as a radio frequency hybrid bridge, a radio frequency attenuator, etc. This not only increases the cost and structural complexity of the system, limits the bandwidth of the system, but also makes the ability of the link to reject IMD2 and SHD vary with the frequency of the input signal due to the frequency dependent nature of these devices, failing to implement a multi-octave microwave photon transmission link of larger SFDR.
Disclosure of Invention
In order to solve the problems of the prior art, the invention provides a multi-octave microwave transmission device and a multi-octave microwave transmission method, which have simplified device structures.
According to an aspect of an embodiment of the present invention, there is provided a multi-octave microwave transmission apparatus including: an optical source for generating and outputting an optical carrier; a signal modulation unit for receiving the optical carrier and the microwave signal to be transmitted, and for being in a predetermined modulation state under the condition of being applied with a predetermined bias voltage, and for modulating the microwave signal to be transmitted onto the optical carrier under the predetermined modulation state to form a modulated optical signal; a photodetector for converting the modulated optical signal into an electrical signal; and in the preset modulation state, the signal modulation unit can inhibit distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state with a preset spurious-free dynamic range.
In the multi-octave microwave transmission device provided in an aspect of the embodiment of the present invention, the signal modulation unit is a dual parallel mach-zehnder modulator, and the dual parallel mach-zehnder modulator includes an upper mach-zehnder modulator, a lower mach-zehnder modulator, a phase modulator, and an optical signal combiner; the uplink Mach-Zehnder modulator is used for receiving the optical carrier and the microwave signal to be transmitted, and modulating the microwave signal to be transmitted onto the optical carrier under the condition of being applied with a first bias voltage so as to form a first optical signal; the downlink Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of being applied with a second bias voltage so as to transmit the optical carrier; the phase modulator is used for receiving the optical carrier output by the downlink Mach-Zehnder modulator and adjusting the phase of the optical carrier output by the downlink Mach-Zehnder modulator under the condition that a third bias voltage is applied to the optical carrier to form a second optical signal; the optical signal combiner is configured to combine the first optical signal and the second optical signal into a Cheng Diaozhi optical signal.
In the multi-octave microwave transmission device provided according to an aspect of the embodiment of the present invention, the third bias voltage of the dual parallel mach-zehnder modulator is set to a fixed value, and the signal modulation unit is placed in the predetermined modulation state by adjusting the first bias voltage and/or the second bias voltage.
In the multi-octave microwave transmission device provided according to an aspect of the embodiment of the present invention, the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1]a＝πV b1 /V π
and/or, the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2]b＝πV b2 /V π
wherein V is π For the half-wave voltage of the signal modulation unit, a represents the optical phase introduced by the first bias voltage, V b1 Representing the first bias voltage, b representing the optical phase introduced by the second bias voltage, V b2 Representing the second bias voltage.
In the multi-octave microwave transmission device provided according to an aspect of the embodiment of the present invention, the optical phase introduced by the first bias voltage and the optical phase introduced by the second bias voltage satisfy the following equation 3,
[3]cos(2a)＝cos(a)cos(b)。
according to another aspect of the embodiment of the invention, a multi-octave microwave transmission method includes: generating and outputting an optical carrier wave by using an optical source; receiving the optical carrier wave and the microwave signal to be transmitted by using a signal modulation unit; modulating the microwave signal to be transmitted onto the optical carrier wave with the signal modulation unit in a predetermined modulation state with a predetermined bias voltage applied thereto to form a modulated optical signal; converting the modulated optical signal into an electrical signal using a photodetector; and in the preset modulation state, the signal modulation unit can inhibit distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state with a preset spurious-free dynamic range.
In the multi-octave microwave transmission method provided by an aspect of the embodiment of the invention, the signal modulation unit is a dual parallel mach-zehnder modulator, and the dual parallel mach-zehnder modulator includes an upper mach-zehnder modulator, a lower mach-zehnder modulator, a phase modulator and an optical signal combiner; the uplink Mach-Zehnder modulator is used for receiving the optical carrier and the microwave signal to be transmitted, and modulating the microwave signal to be transmitted onto the optical carrier under the condition of being applied with a first bias voltage so as to form a first optical signal; the downlink Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of being applied with a second bias voltage so as to transmit the optical carrier; the phase modulator is configured to receive the optical carrier output by the downstream mach-zehnder modulator, and adjust a phase of the optical carrier output by the downstream mach-zehnder modulator when a third bias voltage is applied to the optical carrier to form a second optical signal; the optical signal combiner is configured to combine the first optical signal and the second optical signal into a Cheng Diaozhi optical signal.
In the multi-octave microwave transmission device provided according to an aspect of the embodiment of the present invention, the third bias voltage of the dual parallel mach-zehnder modulator is set to a fixed value, and the signal modulation unit is placed in the predetermined modulation state by adjusting the first bias voltage and/or the second bias voltage.
In the multi-octave microwave transmission device provided according to an aspect of the embodiment of the present invention, the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1]a＝πV b1 /V π
and/or, the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2]b＝πV b2 /V π
wherein V is π For the half-wave voltage of the signal modulation unit, a represents the optical phase introduced by the first bias voltage, V b1 Representing the first bias voltage, b representing the optical phase introduced by the second bias voltage, V b2 Representing the second bias voltage.
In the multi-octave microwave transmission device provided according to an aspect of the embodiment of the present invention, the optical phase introduced by the first bias voltage and the optical phase introduced by the second bias voltage satisfy the following equation 3,
[3]cos(2a)＝cos(a)cos(b)。
the beneficial effects are that:according to the multi-octave microwave transmission device provided by the embodiment of the invention, the multi-octave microwave signal can be transmitted with high linearity.
Further, after the multi-octave microwave transmission device is adopted to transmit the microwave signals, distortion components of the transmitted microwave signals are small, and the spurious-free dynamic range of the transmission device is large.
Furthermore, the multi-octave microwave transmission device according to the embodiment of the invention adopts an all-optical structure, and after the first bias voltage and the second bias voltage of the signal modulation unit are optimized, the parameters of the transmission device are not required to be readjusted, so that the multi-octave transmission of the microwave signal with high linearity can be performed on the whole working bandwidth.
Drawings
The above and other aspects, features and advantages of embodiments of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which:
fig. 1 is a schematic diagram of a multi-octave microwave transmission device in accordance with an embodiment of the present invention;
FIG. 2 is a graph showing the relationship of a and b when the second order distortion component is eliminated;
FIG. 3 is a graph showing a versus spurious free dynamic range;
FIG. 4 is a graph of a frequency spectrum of the multi-octave microwave transmission unit of FIG. 1 when performing a double tone test;
FIG. 5 is a graph showing the results of the distortion components of the multi-octave microwave transmission unit shown in FIG. 1 when performing a double tone test;
FIG. 6 is a graph of the spurious free dynamic range of the multi-octave microwave transmission device of FIG. 1 when performing a double tone test on microwave signals of different frequency bands;
fig. 7 is a flow chart of a multi-octave microwave transmission method according to an embodiment of the present invention.
Detailed Description
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application so that others skilled in the art will be able to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.
As used herein, the term "comprising" and variations thereof mean open-ended terms, meaning "including, but not limited to. The terms "based on", "in accordance with" and the like mean "based at least in part on", "in part in accordance with". The terms "one embodiment" and "an embodiment" mean "at least one embodiment. The term "another embodiment" means "at least one other embodiment". The terms "first," "second," and the like, may refer to different or the same object. Other definitions, whether explicit or implicit, may be included below. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout this specification.
In order to solve the problems set forth in the background art, the invention aims to provide a multi-octave microwave photon transmission link with an all-optical structure based on a double parallel Mach-Zehnder modulator, which is simple in structure and only consists of a laser, the double parallel Mach-Zehnder modulator and a photoelectric detector, and the link can effectively inhibit IMD3, IMD2 and SHD, so that when the link works within a multi-octave bandwidth, larger SFDR can still be realized. The advantage of this link is that it is simple in construction and is an all-optical structure, the ability to reject IMD3, IMD2 and SHD does not change with changes in the frequency of the input signal, and therefore a large SFDR can be achieved within a very large bandwidth. The purpose of the present invention will be described in detail with reference to examples.
Fig. 1 is a schematic diagram of a multi-octave microwave transmission device in accordance with an embodiment of the present invention.
Referring to fig. 1, a multi-octave microwave transmission apparatus (or multi-octave microwave photon transmission link) according to an embodiment of the present invention includes a light source 11, a signal modulation unit 12, and a photodetector 13.
Specifically, the light source 11 is used to generate and output an optical carrier. In one example, the light source 11 may be, for example, a laser light source that generates a single-wavelength continuous laser light as an optical carrier. It will be appreciated that in this case the optical carrier is linearly polarized light.
The signal modulation unit 12 is for receiving the optical carrier from the optical source 11 and for receiving a microwave signal to be transmitted from a microwave signal source (not shown) to be transmitted. The signal modulation unit 12 is configured to be in a predetermined modulation state with a predetermined bias voltage applied thereto, and configured to modulate the microwave signal to be transmitted onto the optical carrier in the predetermined modulation state to form a modulated optical signal. In one example, when signal modulation unit 12 is in the predetermined modulation state, signal modulation unit 12 is capable of suppressing distortion components within the multi-octave microwave transmission device, thereby operating the multi-octave microwave transmission device in a state of a predetermined spurious-free dynamic range.
In one example, signal modulation unit 12 may be, for example, a dual parallel Mach-Zehnder modulator. The dual parallel mach-zehnder modulator includes an upper mach-zehnder modulator 121, a lower mach-zehnder modulator 122, and a phase modulator 123. In this case, the upper mach-zehnder modulator 121 of the dual parallel mach-zehnder modulator is configured to receive an optical carrier from the optical source 11 and to receive a microwave signal to be transmitted from a microwave signal source (not shown) to be transmitted. While the downstream mach-zehnder modulator 122 of the dual parallel mach-zehnder modulator is only used to receive the optical carrier from the optical source 11. In this case, the upper mach-zehnder modulator 121 modulates the microwave signal to be transmitted onto an optical carrier with the first bias voltage applied thereto, thereby forming a first optical signal. At this time, the downstream mach-zehnder modulator 122 operates at the maximum transmission point with the second bias voltage applied thereto, so as to improve the utilization of the optical carrier energy. Further, the optical carrier passing through the downstream mach-zehnder modulator 122 passes through the phase modulator 123 to form a second optical signal. Here, the phase modulator 123 may adjust the phase of the optical carrier passing through the downstream mach-zehnder modulator 122, thereby adjusting the phase difference of the first optical signal and the second optical signal.
In one example, the dual parallel mach-zehnder modulator may further include an optical signal combiner (not shown) for combining the first optical signal and the second optical signal into one optical signal as an output of the signal modulation unit 12, i.e., modulating the optical signal.
The photodetector 14 is used to convert the modulated optical signal into an electrical signal. In one example, the photodetector 14 may be, for example, a 50GHz bandwidth photodetector.
As described above, the multi-octave microwave transmission device provided by the embodiment of the invention can complete the transmission of microwave signals, and has a simple structure.
Further, the multi-octave microwave transmission device provided by the embodiment of the invention works in a state with a large spurious-free dynamic range so as to realize the transmission of microwave signals.
Next, a detailed description will be given of how the multi-octave microwave transmission device according to the embodiment of the present invention operates in a state of a large spurious-free dynamic range to accomplish transmission of a microwave signal.
In one example, if the multi-octave microwave transmission device according to an embodiment of the present invention is to be operated in a state of a large spurious-free dynamic range, it is required to implement the large third-order spurious-free dynamic range SFDR3 and the large second-order spurious-free dynamic range SFDR2 simultaneously according to the multi-octave microwave transmission device of the embodiment of the present invention. The third-order spurious-free dynamic range SFDR3 is determined by the third-order intermodulation distortion component IMD3 of the multi-octave microwave transmission device, and the second-order spurious-free dynamic range SFDR2 is determined by both the second-order intermodulation distortion component IMD2 and the second-harmonic distortion component SHD of the multi-octave microwave transmission device.
In one example, the frequency of the microwave signal to be transmitted is ω 1 And omega 2 . In this case, the microwave signal to be transmitted may be, for example, V RF sin(w 1 t)+V RF sin(w 2 t), namely the microwave signals to be transmitted comprise two microwave signals with equal voltage amplitude and different frequencies.
When the microwave signal to be transmitted drives only the upper mach-zehnder modulator 121 and the second bias voltage of the lower mach-zehnder modulator 122 is set to the maximum output point, the output optical field (i.e., modulated optical signal) E of the signal modulation unit 12 DPMZM Can be expressed as the following formula 1.
Wherein E is in For the light field intensity, ω, of the optical carrier wave output by the light source 11 c Angular frequency, t, of the optical carrier wave output by the light source 11 ff For insertion loss, beta, of signal modulation unit 12 RF ＝πV RF /V π For the modulation factor, V, of the signal modulation unit 12 RF V is the voltage amplitude of the microwave signal to be transmitted π A=pi V, which is the half-wave voltage of the signal modulation unit 12 b1 /V π Is an upper path Mach-Zehnder modulator 121 with a first bias voltage V b1 The incoming optical phase, b=pi V b2 /V π Is a downstream Mach-Zehnder modulator 122 with a second bias voltage V b2 Introduced optical phase, c=pi V b3 /V π Is a main Mach-Zehnder modulator (not shown) composed of an upper Mach-Zehnder modulator 121 and a lower Mach-Zehnder modulator 122, and is composed of a third bias voltage V input from a phase modulator 123 b3 The phase of the light introduced.
Expanding equation 1 with Bessel function to obtain output light field E DPMZM The respective frequency components in the optical domain can be expressed specifically as the following expression 2.
Wherein J is n (β RF ) Coefficients that are expanded for the bessel function.
When the modulated optical signal (i.e., the modulated optical signal) reaches the photodetector 13 after being transmitted, beat frequency is performed, and thus each frequency component in the electrical domain is obtained. Wherein the frequency is omega 1 And omega 2 The magnitude of the current of the useful signal, i.e., the microwave signal to be transmitted in the multi-octave microwave transmission device, can be represented by the following equation 3.
Wherein,is the responsivity of the photodetector 13. Further, the frequency is 2ω 1 -ω 2 And 2ω 2 -ω 1 The component of (2) is third-order intermodulation distortion component IMD3, the amplitude I of the current thereof IMD3 Can be represented by the following expression 4.
The expression of the third-order intermodulation distortion component IMD3 of these two frequencies is identical.
Furthermore, the frequency is 2ω 1 And 2ω 2 The component of (2) is a second harmonic distortion component SHD, the amplitude I of the current SHD Can be represented by the following equation 5. The second harmonic distortion component SHD of these two frequencies is identical in expression.
In addition, the frequency is omega 1 +ω 2 And omega 2 -ω 1 The component of (2) is a second intermodulation distortion component IMD2, the amplitude of the current of whichAnd->Can be represented by the following formulas 6 and 7, respectively.
In order for the multi-octave microwave transmission device to operate in a large spurious-free dynamic range to accomplish transmission of microwave signals, each distortion component in equations 4 through 7 must be as small as possible. As can be seen from equations 4 to 7, each distortion component has three variables, a, b and c, and thus, by optimizing these three variables, each distortion component can be made as small as possible, so that the multi-octave microwave transmission device can operate in a state of large spurious-free dynamic range. Hereinafter, how to optimize the three variables a, b, and c will be described in detail.
Acquisition of inhibition IMD3, SHD, IMD2 (ω) 1 +ω 2 ) And IMD2 (omega) 2 -ω 1 ) The conditions of (2) are as follows:
the conditions for inhibiting IMD3 are represented by the following formulas 8-1 and 8-2:
the conditions for inhibiting SHD are represented by the following formulas 9-1 and 9-2:
cos(2a)＝-cos(a)cos(b)cos(c) (9-2)
the conditions for inhibiting IMD2 (ω1+ω2) are represented by the following formulas 10-1 and 10-2:
cos(2a)＝-cos(a)cos(b)cos(c) (10-2)
the conditions for inhibiting IMD2 (ω2- ω1) are represented by the following formulas 11-1 and 11-2:
cos(2a)＝-cos(a)cos(b)cos(c) (11-2)
equations 8-1 through 11-2 all use small signal approximations, namely: j (J) 0 (β RF )＝1，J 1 (β RF )＝-J -1 (β RF )＝β RF 2 and J 2 (β RF )＝β RF 2 /8. First, the second order distortion component is optimizedThe true component is composed of a second harmonic distortion component SHD, a second-order intermodulation distortion component IMD2 (omega) 1 +ω 2 ) And second-order intermodulation distortion component IMD2 (ω) 2 -ω 1 ) These three components are decided together and correspond to equations 9-1 to 11-2, respectively. As is clear from the formulas 9-1 to 11-2, the conditions to be satisfied to eliminate these three components are the same, as shown in the following formula 12.
cos(2a)＝-cos(a)cos(b)cos(c) [12]
In one example, to make the calculation simple and reduce the operational complexity in practice, the third bias voltage V of the main mach-zehnder modulator (not shown) consisting of the upper path mach-zehnder modulator 121 and the lower path mach-zehnder modulator 122 will be b3 Setting to a fixed value, e.g. to let V b3 =vpi. In this case c=180°, so that only the first bias voltage V needs to be controlled b1 And a second bias voltage V b2 Namely, the control of a and b is sufficient. Of course, in other embodiments, the third bias voltage V b3 Other values may be taken and the corresponding c may be other values. In this case, the expression 12 is simplified to the following expression 13.
cos(2a)＝cos(a)cos(b) [13]
By the simulation calculation, the relationship of a and b when the second-order distortion component is eliminated can be derived. Fig. 2 is a graph showing the relationship of a and b when the second-order distortion component is eliminated. Referring to fig. 2, a ranges from 0 ° to 60 °. Further, with continued reference to fig. 2, a and b are in positive correlation. That is, a third bias voltage V at the main Mach-Zehnder modulator (not shown) b3 When c is set to a fixed value, a and b are in positive correlation when the second order distortion component is eliminated, and a ranges from 0 ° to 60 °.
Next, a third-order distortion component is optimized, which is determined by the third-order intermodulation distortion component IMD3, and this distortion component corresponds to equation 8-1 and equation 8-2. Furthermore, since the spurious-free dynamic range is also related to the amplitude of the transmitted signal, which is represented by equation 3, after the relation of a and b is obtained according to equations 9-1 to 11-2 above, the relation of a and b is incorporated into equations 3 to 7, and the relation of a and spurious-free dynamic range (third-order spurious-free dynamic range SFDR3 and second-order spurious-free dynamic range SFDR 2) can be obtained. Fig. 3 is a graph showing a versus spurious free dynamic range.
Referring to fig. 3, a suitable value of the spurious free dynamic range SFDR is selected (e.g., at least 100dB, i.e., SFDR2 and SFDR3 are each at least 100 dB), a corresponding a is obtained from the selected value of the spurious free dynamic range SFDR, and the obtained a is then taken into equation 13 to obtain b. The obtained a and b can enable the multi-octave microwave transmission device to work in a large spurious-free dynamic range state to finish the transmission of microwave signals.
Fig. 4 is a spectrum diagram of the multi-octave microwave transmission device shown in fig. 1 when performing a double-tone test.
Referring to fig. 4, there is shown a spectrogram of a double single tone test of a microwave signal having a frequency of 5.5GHz and a frequency of 6GHz by a multi-octave microwave transmission device according to an embodiment of the present invention, the optical power input to the photodetector is 7.1dBm, and the noise floor of the multi-octave microwave transmission device is-160.2 dBm/Hz.
Fig. 5 is a graph showing the results of distortion components of the multi-octave microwave transmission unit shown in fig. 1 when performing a double tone test.
Referring to fig. 5, a illustrates a graph showing the results of SFDR3 limited by IMD3 when dual tone testing is performed on microwave signals having frequencies of 10GHz and 10.0005GHz by a multi-octave microwave transmission device in accordance with an embodiment of the present invention; b illustrates a graph of the results of SFDR2 limited by SHD when a multi-octave microwave transmission device performs a double tone test on microwave signals having frequencies of 10GHz and 10.0005GHz, in accordance with an embodiment of the present invention; figure c illustrates a multi-octave microwave transmission device according to an embodiment of the present invention as used by IMD2 (ω) when performing a double tone test on microwave signals having frequencies of 10GHz and 10.0005GHz 1 +ω 2 ) The result graph of the limited SFDR2, d illustrates the performance of a double single tone test by IMD2 (omega 2 -ω 1 ) By a means ofResults plot of limited SFDR2.
Fig. 6 is a graph showing the result of spurious-free dynamic range of the multi-octave microwave transmission device shown in fig. 1 when performing a double-tone test on microwave signals in different frequency bands.
It should be noted that, after a, b, and c are fixed, fig. 6 shows a measurement result diagram obtained by measuring microwave signals in different frequency bands without readjusting other parameters in the device according to an embodiment of the present invention. Referring to fig. 6, the multi-octave microwave transmission device according to the embodiment of the invention can realize microwave signal transmission with larger spurious-free dynamic range for microwave signals in the working bandwidth without readjusting parameters in the device. This is mainly due to the fact that the multi-octave microwave transmission device according to the embodiment of the invention is constructed in an all-optical structure and does not contain radio frequency devices. Other transmission devices in the prior art all contain radio frequency devices, and the radio frequency devices have frequency-related characteristics, so that when the frequency is changed, parameters of the transmission device need to be readjusted to ensure that the transmission device is in a better working state. Further, in fig. 6, microwave signal transmission in the range of 4GHz-12GHz is shown, and the condition that the maximum frequency is greater than the minimum frequency by two times is satisfied, which proves that the multi-octave microwave transmission device according to the embodiment of the present invention can operate in a multi-octave state.
In summary, the multi-octave microwave transmission device according to the embodiments of the present invention can perform high-linearity transmission on multi-octave microwave signals. Further, after the multi-octave microwave transmission device is adopted to transmit the microwave signals, distortion components of the transmitted microwave signals are small, and the spurious-free dynamic range of the transmission device is large. Furthermore, the multi-octave microwave transmission device according to the embodiment of the invention adopts an all-optical structure, and after the first bias voltage and the second bias voltage of the signal modulation unit are optimized, the parameters of the transmission device are not required to be readjusted, so that the multi-octave transmission of the microwave signal with high linearity can be performed on the whole working bandwidth.
Next, a multi-octave microwave transmission method according to an embodiment of the present invention will be described in detail. Fig. 7 is a flow chart of a multi-octave microwave transmission method according to an embodiment of the present invention.
In one example, in the description of the multi-octave microwave transmission method according to an embodiment of the present invention, microwaves may be transmitted using the multi-octave microwave transmission apparatus shown in fig. 1 as an example.
Accordingly, referring to fig. 1 and 7 together, in step S710, an optical carrier is generated and outputted by the optical source 11 of the multi-octave microwave transmission device shown in fig. 1.
In step S720, the optical carrier is received from the optical source 11 and the microwave signal to be transmitted is received from the microwave signal source (not shown) to be transmitted by using the signal modulation unit 12 of the multi-octave microwave transmission device shown in fig. 1.
In step S730, the microwave signal to be transmitted is modulated onto an optical carrier with the signal modulation unit 12 in a predetermined modulation state with a predetermined bias voltage applied thereto, thereby forming a modulated optical signal.
Wherein, as described above, in the predetermined modulation state, the signal modulation unit 12 can suppress the distortion component in the multi-octave microwave transmission device, thereby operating the multi-octave microwave transmission device in a state of a predetermined spurious-free dynamic range. In one example, signal modulation unit 12 may be, for example, a dual parallel Mach-Zehnder modulator. The dual parallel mach-zehnder modulator includes an upper mach-zehnder modulator 121, a lower mach-zehnder modulator 122, and a phase modulator 123.
Specifically, the microwave signal to be transmitted is modulated onto an optical carrier with a first bias voltage applied thereto by using an upstream mach-zehnder modulator 121, thereby forming a first optical signal. At this time, the downstream mach-zehnder modulator 122 operates at the maximum transmission point with the second bias voltage applied thereto, so as to improve the utilization of the optical carrier energy. That is, at this time, the signal modulation unit 12 is in a predetermined modulation state. Further, the optical carrier passing through the downstream mach-zehnder modulator 122 passes through the phase modulator 123 to form a second optical signal. Here, the phase modulator 123 may adjust the phase of the optical carrier passing through the downstream mach-zehnder modulator 122, thereby adjusting the phase difference of the first optical signal and the second optical signal.
In one example, the dual parallel mach-zehnder modulator may further include an optical signal combiner (not shown) for combining the first optical signal and the second optical signal into one optical signal as an output of the signal modulation unit 12, i.e., modulating the optical signal.
In step S740, the modulated optical signal is converted into an electrical signal by using the photodetector 13 of the multi-octave microwave transmission device shown in fig. 1.
As described above, according to the multi-octave microwave transmission method provided by the embodiment of the present invention, transmission of a microwave signal can be completed, and a transmission device implementing the transmission method has a simple structure.
Further, according to the multi-octave microwave transmission method provided by the embodiment of the invention, the distortion component in the multi-octave microwave transmission device can be restrained by utilizing the first bias voltage and the second bias voltage, so that the multi-octave microwave transmission device implementing the transmission method can work in a state of large spurious-free dynamic range.
In addition, the description of how the transmission of the microwave signal is completed in the state of large spurious-free dynamic range in the multi-octave microwave transmission method according to the embodiment of the present invention is referred to the above description, and is not repeated here.
The foregoing describes specific embodiments of the present invention. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.
Not all steps or units in the above-mentioned flowcharts and system configuration diagrams are necessary, and some steps or units may be omitted according to actual needs. The order of execution of the steps is not fixed and may be determined as desired. The apparatus structures described in the above embodiments may be physical structures or logical structures, that is, some units may be implemented by the same physical entity, or some units may be implemented by multiple physical entities, or may be implemented jointly by some components in multiple independent devices.
The terms "exemplary," "example," and the like, as used throughout this specification, mean "serving as an example, instance, or illustration," and do not mean "preferred" or "advantageous" over other embodiments. The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.
The alternative implementation of the embodiment of the present invention has been described in detail above with reference to the accompanying drawings, but the embodiment of the present invention is not limited to the specific details of the foregoing implementation, and various simple modifications may be made to the technical solutions of the embodiment of the present invention within the scope of the technical concept of the embodiment of the present invention, and these simple modifications all fall within the protection scope of the embodiment of the present invention.
The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. A multi-octave microwave transmission device, comprising:
an optical source for generating and outputting an optical carrier;
a signal modulation unit for receiving the optical carrier and the microwave signal to be transmitted, and for being in a predetermined modulation state under the condition of being applied with a predetermined bias voltage, and for modulating the microwave signal to be transmitted onto the optical carrier under the predetermined modulation state to form a modulated optical signal;
a photodetector for converting the modulated optical signal into an electrical signal;
the signal modulation unit can inhibit distortion components in the multi-octave microwave transmission device in the preset modulation state, so that the multi-octave microwave transmission device works in a state with a preset spurious-free dynamic range;
wherein the signal modulation unit is a dual parallel mach-zehnder modulator, the dual parallel mach-zehnder modulator comprising: an upstream Mach-Zehnder modulator, a downstream Mach-Zehnder modulator, a phase modulator, and an optical signal combiner; the uplink Mach-Zehnder modulator is used for receiving the optical carrier and the microwave signal to be transmitted, and modulating the microwave signal to be transmitted onto the optical carrier under the condition of being applied with a first bias voltage so as to form a first optical signal; the downlink Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of being applied with a second bias voltage so as to transmit the optical carrier; the phase modulator is used for receiving the optical carrier output by the downlink Mach-Zehnder modulator and adjusting the phase of the optical carrier output by the downlink Mach-Zehnder modulator under the condition that a third bias voltage is applied to the optical carrier to form a second optical signal; the optical signal combiner is configured to combine the first optical signal and the second optical signal into a Cheng Diaozhi optical signal;
wherein the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1]a＝πV b1 /V π
the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2]b＝πV b2 /V π
the optical phase introduced by the first bias voltage and the optical phase introduced by the second bias voltage satisfy the following equation 3,
[3]cos(2a)＝cos(a)cos(b)；
wherein V is π For the half-wave voltage of the signal modulation unit, a represents the optical phase introduced by the first bias voltage, V b1 Representing the first bias voltage, b representing the optical phase introduced by the second bias voltage, V b2 Representing the second bias voltage.
2. The multi-octave microwave transmission unit according to claim 1, wherein a third bias voltage of the dual parallel mach-zehnder modulator is set to a fixed value, and the signal modulation unit is placed in the predetermined modulation state by adjusting the first bias voltage and/or the second bias voltage.
3. A multi-octave microwave transmission method, comprising:
generating and outputting an optical carrier wave by utilizing a light source of the multi-octave microwave transmission device;
receiving the optical carrier and the microwave signal to be transmitted by using a signal modulation unit of the multi-octave microwave transmission device;
modulating the microwave signal to be transmitted onto the optical carrier wave with the signal modulation unit in a predetermined modulation state with a predetermined bias voltage applied thereto to form a modulated optical signal;
converting the modulated optical signal into an electrical signal by using a photodetector of the multi-octave microwave transmission device;
the signal modulation unit can inhibit distortion components in the multi-octave microwave transmission device in the preset modulation state, so that the multi-octave microwave transmission device works in a state with a preset spurious-free dynamic range;
the signal modulation unit is a double parallel Mach-Zehnder modulator, and the double parallel Mach-Zehnder modulator comprises an upper path Mach-Zehnder modulator, a lower path Mach-Zehnder modulator, a phase modulator and an optical signal combiner; the uplink Mach-Zehnder modulator is used for receiving the optical carrier and the microwave signal to be transmitted, and modulating the microwave signal to be transmitted onto the optical carrier under the condition of being applied with a first bias voltage so as to form a first optical signal; the downlink Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of being applied with a second bias voltage so as to transmit the optical carrier; the phase modulator is used for receiving the optical carrier wave output by the downlink Mach-Zehnder modulator and adjusting the phase of the optical carrier wave output by the downlink Mach-Zehnder modulator to form a second optical signal; the optical signal combiner is configured to combine the first optical signal and the second optical signal into a Cheng Diaozhi optical signal;
wherein the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1]a＝πV b1 /V π
the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2]b＝πV b2 /V π
the optical phase introduced by the first bias voltage and the optical phase introduced by the second bias voltage satisfy the following equation 3,
[3]cos(2a)＝cos(a)cos(b)；
wherein V is π For the half-wave voltage of the signal modulation unit, a represents the optical phase introduced by the first bias voltage, V b1 Representing the first bias voltage, b representing the optical phase introduced by the second bias voltage, V b2 Representing the second bias voltage.
4. A multi-octave microwave transmission method according to claim 3, wherein a third bias voltage of the dual parallel mach-zehnder modulator is set to a fixed value, and the signal modulation unit is brought into the predetermined modulation state by adjusting the first bias voltage and/or the second bias voltage.
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