CN112448766A - 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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Abstract
The invention provides a multi-octave microwave transmission device, which comprises: a light source for generating and outputting a light carrier; the signal modulation unit is used for receiving the optical carrier and the microwave signal to be transmitted, is in a preset modulation state under the condition that a preset bias voltage is applied, and is used for modulating the microwave signal to be transmitted onto the optical carrier under the preset modulation state so as to form a modulated optical signal; a photodetector for converting the modulated optical signal into an electrical signal; wherein, in the predetermined modulation state, the signal modulation unit can suppress distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state of a predetermined 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. Due to the large Spurious Free Dynamic Range (SFDR), the broadband microwave signal can be transmitted in a high linearity under the state of multiple octaves, 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, the use of a multi-octave link for the transmission of microwave signals means a larger transmission capacity; in radar systems, multiple octave microwave transmission can achieve higher resolution.
In the 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 (IMD3), a second-order distortion term dominated by second-order intermodulation distortion (IMD2) and second-order harmonic distortion (SHD) also exist in the working bandwidth of the signal, and the second-order distortion term is difficult to filter by a filter; furthermore, IMD2 and SHD may degrade the system's SFDR more dramatically than IMD3, and when the microwave transmission link is operating in a multi-octave transmission regime, although the operating bandwidth of the link can be increased, the system's SFDR may be reduced. Therefore, how to suppress IMD2, SHD, and IMD3 simultaneously to increase SFDR becomes a difficult point to overcome for a multi-octave microwave transmission link.
The microwave photon technology can complete the transmission of microwave signals in an optical domain, has the advantages of electromagnetic interference resistance, large bandwidth, low loss, compatibility with the optical communication technology and the like, is widely used for transmitting microwave signals and realizes a microwave photon transmission link. In the microwave photonic transmission link, multi-octave microwave signal transmission can be realized, and a plurality of related technologies are proposed at present. However, in these techniques, a balanced detector is often used to counteract IMD2 and SHD; or use wideband rf devices to perform some signal processing in the electrical domain, such as rf hybrid bridges, rf attenuators, etc. This not only increases the cost and structural complexity of the system, limits the bandwidth of the system, but also due to the frequency-dependent nature of these devices, the ability of the link to suppress IMD2 and SHD varies with the frequency of the input signal, and thus a larger SFDR multi-octave microwave photonic transmission link cannot be realized.
Disclosure of Invention
In order to solve the above-mentioned problems of the prior art, the present invention provides a multi-octave microwave transmission apparatus and a multi-octave microwave transmission method in which the apparatus structure is simplified.
According to an aspect of an embodiment of the present invention, there is provided a multi-octave microwave transmission apparatus including: a light source for generating and outputting a light carrier; the signal modulation unit is used for receiving the optical carrier and the microwave signal to be transmitted, is in a preset modulation state under the condition that a preset bias voltage is applied, and is used for modulating the microwave signal to be transmitted onto the optical carrier under the preset modulation state so as to form a modulated optical signal; a photodetector for converting the modulated optical signal into an electrical signal; wherein, in the predetermined modulation state, the signal modulation unit can suppress distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state of a predetermined spurious-free dynamic range.
In the multi-octave microwave transmission device provided according to an aspect of the embodiments of the present invention, the signal modulation unit is a dual parallel mach-zehnder modulator including an upper mach-zehnder modulator, a lower mach-zehnder modulator, a phase modulator, and an optical signal combiner; the upper path 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 that a first bias voltage is applied to the optical carrier so as to form a first optical signal; the down-path Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of applying a second bias voltage so as to transmit the optical carrier; the phase modulator is used for receiving the optical carrier output by the lower Mach-Zehnder modulator and adjusting the phase of the optical carrier output by the lower 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 modulated optical signal.
In the multi-octave microwave transmission device provided according to an aspect of the embodiments 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 brought into the predetermined modulation state by adjusting the first bias voltage and/or the second bias voltage.
In the multiple octave microwave transmission device provided according to an aspect of the embodiments of the present invention, the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1]a＝πVb1/Vπ
and/or the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2]b＝πVb2/Vπ
wherein, VπFor a half-wave voltage of the signal modulation unit, a denotes an optical phase introduced by the first bias voltage, Vb1Representing said first bias voltage, b representing the optical phase introduced by said second bias voltage, Vb2Representing the second bias voltage.
In the multiple octave microwave transmission device provided according to an aspect of the embodiments 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 embodiments of the present invention, a multi-octave microwave transmission method includes: generating and outputting a light carrier wave by using a light source; receiving the optical carrier and the microwave signal to be transmitted by using a signal modulation unit; modulating the microwave signal to be transmitted onto the optical carrier with the signal modulation unit in a predetermined modulation state under the condition that a predetermined bias voltage is applied to form a modulated optical signal; converting the modulated optical signal into an electrical signal using a photodetector; wherein, in the predetermined modulation state, the signal modulation unit can suppress distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state of a predetermined spurious-free dynamic range.
In the multi-octave microwave transmission method provided according to an aspect of the embodiments of the present invention, the signal modulation unit is a dual parallel mach-zehnder modulator including an upper mach-zehnder modulator, a lower mach-zehnder modulator, a phase modulator, and an optical signal combiner; the upper path 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 that a first bias voltage is applied to the optical carrier so as to form a first optical signal; the down-path Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of applying a second bias voltage so as to transmit the optical carrier; the phase modulator is used for receiving the optical carrier output by the down-path Mach-Zehnder modulator and adjusting the phase of the optical carrier output by the down-path 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 modulated optical signal.
In the multi-octave microwave transmission device provided according to an aspect of the embodiments 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 brought into the predetermined modulation state by adjusting the first bias voltage and/or the second bias voltage.
In the multiple octave microwave transmission device provided according to an aspect of the embodiments of the present invention, the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1]a＝πVb1/Vπ
and/or the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2]b＝πVb2/Vπ
wherein, VπFor a half-wave voltage of the signal modulation unit, a denotes an optical phase introduced by the first bias voltage, Vb1Representing said first bias voltage, b representing the optical phase introduced by said second bias voltage, Vb2Representing the second bias voltage.
In the multiple octave microwave transmission device provided according to an aspect of the embodiments 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)。
has the advantages that:the multi-octave microwave transmission device can transmit multi-octave microwave signals with high linearity.
Further, after the multi-octave microwave transmission device according to the embodiment of the invention is adopted to transmit the microwave signal, the distortion component of the transmitted microwave signal is 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 multi-octave transmission with high linearity can be performed on the microwave signal of the whole working bandwidth without readjusting the parameters of the transmission device.
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The above and other aspects, features and advantages of embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic diagram of a multi-octave microwave transmission device according to 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 removed;
FIG. 3 is a graph showing a relationship between a and spurious-free dynamic range;
FIG. 4 is a spectrum diagram of the multi-octave microwave transmission device of FIG. 1 undergoing a dual tone test;
FIG. 5 is a graph showing the results of distortion components in the DTMF test performed by the multi-octave microwave transmission apparatus of FIG. 1;
FIG. 6 is a graph showing the results of spurious-free dynamic ranges of the multi-octave microwave transmission apparatus of FIG. 1 when dual-tone testing is performed on microwave signals of different frequency bands;
fig. 7 is a flow chart of a method of multi-octave microwave transmission according to an embodiment of the 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 to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.
As used herein, the term "include" and its variants mean open-ended terms in the sense of "including, but not limited to. The terms "based on," based on, "and the like mean" based at least in part on, "" based at least in part on. 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. The definition of a term is consistent throughout the specification unless the context clearly dictates otherwise.
In order to solve the problems brought forward by the background art, the invention aims to provide a multi-octave microwave photon transmission link based on an all-optical structure of a double-parallel Mach-Zehnder modulator, the link is simple in structure and only comprises a laser, the double-parallel Mach-Zehnder modulator and a photoelectric detector, the link can effectively inhibit IMD3, IMD2 and SHD, and the link can still realize large SFDR when working in a multi-octave bandwidth. The advantage of this link is that it is simple in construction and is an all-optical structure, and the ability to suppress IMD3, IMD2, and SHD does not change with changes in the frequency of the input signal, thus enabling large SFDR over a very large bandwidth. The objects of the present invention will be described in detail below with reference to examples.
Fig. 1 is a schematic diagram of a multi-octave microwave transmission device according to an embodiment of the present invention.
Referring to fig. 1, the multi-octave microwave transmission apparatus (or multi-octave microwave photonic transmission link) according to the 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 a light 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 the optical carrier. It will be appreciated that in this case the optical carrier is linearly polarised.
The signal modulation unit 12 is configured to receive the optical carrier from the light source 11, and is configured to receive 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 when a predetermined bias voltage is applied thereto, and is 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 the signal modulation unit 12 is in the predetermined modulation state, the signal modulation unit 12 can suppress distortion components 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, the signal modulation unit 12 may be, for example, a dual parallel mach-zehnder modulator. The double 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 used for receiving an 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. While the drop mach-zehnder modulator 122 of the dual parallel mach-zehnder modulator is used only to receive optical carriers 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 down-path mach-zehnder modulator 122 operates at the maximum transmission point with the second bias voltage applied thereto, to improve the utilization rate of the optical carrier energy. Further, the optical carrier passing through the downstream mach-zehnder modulator 122 passes through the phase modulator 123, and then forms a second optical signal. Here, the phase modulator 123 may adjust the phase of the optical carrier passing through the drop mach-zehnder modulator 122, thereby adjusting the phase difference between the first optical signal and the second optical signal.
In an example, the dual-parallel mach-zehnder modulator may further include an optical signal combiner (not shown), where the optical signal combiner is configured to combine the first optical signal and the second optical signal into one optical signal as an output optical signal of the signal modulation unit 12, that is, a modulated 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, according to the embodiment of the present invention, the multi-octave microwave transmission apparatus is provided, which can complete transmission of a microwave signal and has a simple structure.
Further, the multi-octave microwave transmission device provided by the embodiment of the invention works in a state of large spurious-free dynamic range to realize the transmission of the microwave signal.
Next, how the multi-octave microwave transmission apparatus according to the embodiment of the present invention operates in a state of a large spurious-free dynamic range will be described in detail.
In one example, if a 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 require the multi-octave microwave transmission device according to an embodiment of the present invention to simultaneously realize a large third-order spurious-free dynamic range SFDR3 and a large second-order spurious-free dynamic range SFDR 2. 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-order harmonic distortion component SHD of the multi-octave microwave transmission device.
In one example, the frequency of the microwave signal to be transmitted is ω1And ω2. In this case, the microwave signal to be transmitted may be, for example, VRFsin(w1t)+VRFsin(w2t), 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 pointThe output optical field (i.e., modulated optical signal) E of the signal modulation unit 12DPMZMCan be expressed as the following equation 1.
Wherein E isinLight field intensity, omega, of an optical carrier wave output by the light source 11cAngular frequency, t, of an optical carrier wave output by the light source 11ffIs the insertion loss, beta, of the signal modulation unit 12RF＝πVRF/VπIs a modulation factor, V, of the signal modulation unit 12RFIs the voltage amplitude, V, of the microwave signal to be transmittedπFor half-wave voltage of the signal modulation unit 12, a ═ pi Vb1/VπThe upstream Mach-Zehnder modulator 121 is biased by a first bias voltage Vb1Introduced optical phase, b ═ pi Vb2/VπThe down-path Mach-Zehnder modulator 122 is biased by a second bias voltage Vb2Introduced optical phase, c ═ π Vb3/VπA main Mach-Zehnder modulator (not shown) composed of an up-path Mach-Zehnder modulator 121 and a down-path Mach-Zehnder modulator 122 is controlled by a third bias voltage V inputted from a phase modulator 123b3The introduced optical phase.
The output light field E can be obtained by expanding the formula 1 by a Bessel functionDPMZMEach frequency component in the optical domain may be specifically expressed as the following equation 2.
Wherein, Jn(βRF) Coefficients that are the expansion of the bezier function.
When the modulated optical signal (i.e., the modulated optical signal) reaches the photodetector 13 after being transmitted, and beat frequency is performed, each frequency component in the electrical domain is obtained. Wherein the frequency is omega1And ω2Is a useful signal, i.e. the microwave signal to be transmitted in a multioctave microwave transmission device, the current of which isCan be represented by the following equation 3.
Wherein the content of the first and second substances,
is the responsivity of the photodetector 13. Further, the frequency is 2 ω1-ω2And 2 omega2-ω1The component of (A) is the third-order intermodulation distortion component IMD3, the amplitude of which current is IIMD3Can be represented by the following equation 4.
It should be noted that the expressions of the third-order intermodulation distortion component IMD3 of the two frequencies are consistent.
Further, the frequency is 2 ω1And 2 omega2The component of (a) is a second harmonic distortion component SHD, the amplitude I of which currentSHDCan be represented by the following equation 5. It should be noted that the expressions of the second harmonic distortion components SHD of the two frequencies are identical.
In addition, the frequency is ω1+ω2And ω2-ω1The component of (a) is a second-order intermodulation distortion component IMD2, the amplitude of which current
And
which may be represented by equation 6 and equation 7 below, respectively.
In order to enable the multi-octave microwave transmission device to operate in a state of a large spurious-free dynamic range to complete transmission of microwave signals, distortion components in equations 4 to 7 must be as small as possible. As can be seen from equations 4 to 7, each distortion component contains three variables, namely a, b and c, and thus, by optimizing the 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 a large spurious-free dynamic range. Hereinafter, a detailed description will be given of how to optimize the three variables a, b, and c.
Acquisition suppression IMD3, SHD, IMD2(ω)1+ω2) And IMD2(ω)2-ω1) The conditions of (1) are as follows:
the conditions for inhibiting IMD3 are represented by the following equation 8-1 and equation 8-2:
the conditions for suppressing SHD are represented by the following equations 9-1 and 9-2:
cos(2a)＝-cos(a)cos(b)cos(c) (9-2)
the condition for suppressing IMD2(ω 1+ ω 2) is represented by the following equation 10-1 and equation 10-2:
cos(2a)＝-cos(a)cos(b)cos(c) (10-2)
the conditions for suppressing IMD2(ω 2- ω 1) are represented by the following equation 11-1 and equation 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. the design is a square0(βRF)＝1，J1(βRF)＝-J-1(βRF)＝βRF/2 and J2(βRF)＝βRF 2/8. First, the second-order distortion component is optimized, and the second-order distortion component is composed of the second harmonic distortion component SHD and the second-order intermodulation distortion component IMD2 (omega)1+ω2) And a second-order intermodulation distortion component IMD2(ω)2-ω1) These three components are determined in common, and these three distortion components correspond to equations 9-1 to 11-2, respectively. As can be seen from equations 9-1 through 11-2, the conditions to be satisfied for eliminating these three components are the same, as shown in equation 12 below.
cos(2a)＝-cos(a)cos(b)cos(c) [12]
In one example, to make the calculation simple and reduce the complexity of the operation in practice, the third bias voltage V of the main mach-zehnder modulator (not shown) composed of the up-path mach-zehnder modulator 121 and the down-path mach-zehnder modulator 122 is set to be lower than the third bias voltage Vb3Set to a fixed value, e.g. Vb3V pi. In this case, c is 180 °, so that only the first bias voltage V needs to be controlledb1And a second bias voltage Vb2Namely, control a and b. Of course, in other embodiments, the third bias voltage Vb3Other values may be taken and the corresponding c may be other values. In this case, equation 12 is simplified to equation 13 below.
cos(2a)＝cos(a)cos(b) [13]
Through simulation calculation, the relationship of a and b when the second-order distortion component is eliminated can be obtained. Fig. 2 is a graph showing the relationship of a and b when the second order distortion component is removed. Referring to fig. 2, a ranges from 0 ° to 60 °. Further, with continued reference to FIG. 2, a and b are in a positive correlation. That is, the third bias voltage V at the main Mach-Zehnder modulator (not shown)b3Is set to a fixed value, i.e., c is set to a fixed value, a and b are in a positive correlation when the second-order distortion component is eliminated, and a ranges from 0 ° to 60 °.
Second, a third order distortion component is optimized, which is determined by the third order intermodulation distortion component IMD3, and this distortion component corresponds to equations 8-1 and 8-2. In addition, since the spurious-free dynamic range is also related to the amplitude of the transmitted signal, which is represented by equation 3, the relationship of a and b is incorporated into equations 3 to 7 after the relationship of a and b is obtained according to equations 9-1 to 11-2 above, and the relationship of a and spurious-free dynamic range (third order spurious-free dynamic range SFDR3 and second order spurious-free dynamic range SFDR2) can be obtained. FIG. 3 is a graph showing a relationship between a and the spurious-free dynamic range.
Referring to fig. 3, a suitable value of the spurious-free dynamic range SFDR is selected (for example, at least 100dB, that is, at least 100dB for both SFDR2 and SFDR 3), a corresponding a is obtained according to the selected value of the spurious-free dynamic range SFDR, and then the obtained a is substituted into equation 13 to obtain b. The obtained a and b can enable the multi-octave microwave transmission device to work in a state of large spurious-free dynamic range to complete the transmission of the microwave signal.
Fig. 4 is a spectrum diagram of the multi-octave microwave transmission device shown in fig. 1 when a dual tone test is performed.
Referring to fig. 4, a spectrum diagram of a double-tone test of a multi-octave microwave transmission device according to an embodiment of the present invention on microwave signals having frequencies of 5.5GHz and 6GHz is shown, where 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 in the double tone test performed by the multi-octave microwave transmission apparatus shown in fig. 1.
Referring to fig. 5, a is a graph illustrating the results of SFDR3 limited by IMD3 when a dual tone test is performed on microwave signals having frequencies of 10GHz and 10.0005GHz by the multi-octave microwave transmission device according to an embodiment of the present invention; b is a graph showing the results of SFDR2 limited by SHD when a dual tone test is performed on microwave signals having frequencies of 10GHz and 10.0005GHz by the multi-octave microwave transmission device according to an embodiment of the present invention; c is a diagram illustrating a test performed by an IMD2 (omega) using a multi-octave microwave transmission apparatus according to an embodiment of the present invention to perform a two-tone test on microwave signals having frequencies of 10GHz and 10.0005GHz1+ω2) FIG. d is a graph showing the results of limiting SFDR2, illustrating the results of a dual tone test performed by IMD2(ω) on microwave signals having frequencies of 10GHz and 10.0005GHz by a multi-octave microwave transmission device according to an embodiment of the present invention2-ω1) Results plot of the restricted SFDR 2.
Fig. 6 is a graph showing the results of spurious-free dynamic ranges of the multi-octave microwave transmission apparatus of fig. 1 when a two-tone test is performed on microwave signals of different frequency bands.
It should be noted that fig. 6 is a graph showing measurement results obtained by measuring microwave signals of different frequency bands after a, b and c are fixed without readjusting other parameters in the device according to the embodiment of the present invention. Referring to fig. 6, the multi-octave microwave transmission apparatus according to the embodiment of the present invention can achieve microwave signal transmission with a large spurious-free dynamic range for microwave signals within an operating bandwidth without readjusting parameters in the apparatus. This is mainly because the multi-octave microwave transmission device according to the embodiment of the present invention is configured as an all-optical structure and does not include a radio frequency device. Other transmission devices of the prior art include rf devices having frequency-dependent 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 twice the minimum frequency is satisfied, demonstrating that the multi-octave microwave transmission apparatus according to the embodiment of the present invention can operate in a multi-octave state.
In summary, the multi-octave microwave transmission apparatus according to the embodiment of the invention can perform high-linearity transmission on multi-octave microwave signals. Further, after the multi-octave microwave transmission device according to the embodiment of the invention is adopted to transmit the microwave signal, the distortion component of the transmitted microwave signal is 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 multi-octave transmission with high linearity can be performed on the microwave signal of the whole working bandwidth without readjusting the parameters of the transmission device.
Next, a description will be given in detail of a multi-octave microwave transmission method according to an embodiment of the present invention. Fig. 7 is a flow chart of a method of multi-octave microwave transmission according to an embodiment of the invention.
In one example, in the description of the multi-octave microwave transmission method according to the embodiment of the present invention, microwaves may be transmitted using the multi-octave microwave transmission apparatus shown in fig. 1 as an example.
Therefore, referring to fig. 1 and 7 together, in step S710, the light source 11 of the multi-octave microwave transmission device shown in fig. 1 generates and outputs a light carrier.
In step S720, the optical carrier is received from the light source 11 and the microwave signal to be transmitted is received from the microwave signal source (not shown) by using the signal modulation unit 12 of the multi-octave microwave transmission apparatus shown in fig. 1.
In step S730, the microwave signal to be transmitted is modulated onto an optical carrier by the signal modulation unit 12 in a predetermined modulation state with a predetermined bias voltage applied thereto, thereby forming a modulated optical signal.
As described above, in the predetermined modulation state, the signal modulation unit 12 can suppress a distortion component in the multi-octave microwave transmission apparatus, so that the multi-octave microwave transmission apparatus operates in a state of a predetermined spurious-free dynamic range. In one example, the signal modulation unit 12 may be, for example, a dual parallel mach-zehnder modulator. The double 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 the first bias voltage applied thereto by the upper mach-zehnder modulator 121, thereby forming a first optical signal. At this time, the down-path mach-zehnder modulator 122 operates at the maximum transmission point with the second bias voltage applied thereto, to improve the utilization rate 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, and then forms a second optical signal. Here, the phase modulator 123 may adjust the phase of the optical carrier passing through the drop mach-zehnder modulator 122, thereby adjusting the phase difference between the first optical signal and the second optical signal.
In an example, the dual-parallel mach-zehnder modulator may further include an optical signal combiner (not shown), where the optical signal combiner is configured to combine the first optical signal and the second optical signal into one optical signal as an output optical signal of the signal modulation unit 12, that is, a modulated optical signal.
In step S740, the modulated optical signal is converted into an electrical signal using the photodetector 13 of the multi-octave microwave transmission device shown in fig. 1.
As described above, according to the multiple octave microwave transmission method provided by the embodiment of the present invention, it is possible to complete transmission of a microwave signal, and the structure of a transmission apparatus implementing the transmission method is simple.
Further, according to the multiple octave microwave transmission method provided by the embodiment of the invention, the first bias voltage and the second bias voltage can be utilized to suppress distortion components in the multiple octave microwave transmission device, so that the multiple octave microwave transmission device implementing the transmission method can work in a state of a large spurious-free dynamic range.
In addition, please refer to the above description for explaining how to complete the transmission of the microwave signal in the state of the large spurious-free dynamic range in the multi-octave microwave transmission method according to the embodiment of the present invention, which is not described herein again.
The foregoing description has described certain embodiments of this invention. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may 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 may also be possible or may be advantageous.
Not all steps and elements in the above flows and system structure diagrams are necessary, and some steps or elements may be omitted according to actual needs. The execution order of the steps is not fixed, and can be determined as required. 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 a plurality of physical entities, or some units may be implemented by some components in a plurality of 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.
Alternative embodiments of the present invention are described in detail with reference to the drawings, however, the embodiments of the present invention are not limited to the specific details in the above embodiments, and within the technical idea of the embodiments of the present invention, many simple modifications may be made to the technical solution of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments 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 description 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 (10)
1. A multi-octave microwave transmission device, comprising:
a light source for generating and outputting a light carrier;
the signal modulation unit is used for receiving the optical carrier and the microwave signal to be transmitted, is in a preset modulation state under the condition that a preset bias voltage is applied, and is used for modulating the microwave signal to be transmitted onto the optical carrier under the preset modulation state so as to form a modulated optical signal;
a photodetector for converting the modulated optical signal into an electrical signal;
wherein, in the predetermined modulation state, the signal modulation unit can suppress distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state of a predetermined spurious-free dynamic range.
2. The multi-octave microwave transmission device of claim 1, wherein the signal modulation unit is a dual parallel mach-zehnder modulator, the dual parallel mach-zehnder modulator comprising: an upper path Mach-Zehnder modulator, a lower path Mach-Zehnder modulator, a phase modulator and an optical signal beam combiner;
the upper path 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 that a first bias voltage is applied to the optical carrier so as to form a first optical signal;
the down-path Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of applying a second bias voltage so as to transmit the optical carrier;
the phase modulator is used for receiving the optical carrier output by the lower Mach-Zehnder modulator and adjusting the phase of the optical carrier output by the lower 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 modulated optical signal.
3. The multi-octave microwave transmission device according to claim 2, 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.
4. The multi-octave microwave transmission device of claim 2 or 3, wherein the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1] a＝πVb1/Vπ
and/or the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2] b＝πVb2/Vπ
wherein, VπFor a half-wave voltage of the signal modulation unit, a represents the voltage introduced by the first bias voltageOptical phase of (V)b1Representing said first bias voltage, b representing the optical phase introduced by said second bias voltage, Vb2Representing the second bias voltage.
5. The multi-octave microwave transmission device of claim 4, wherein 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)。
6. a multi-octave microwave transmission method is characterized by comprising the following steps:
generating and outputting a light carrier wave by using a light source;
receiving the optical carrier and the microwave signal to be transmitted by using a signal modulation unit;
modulating the microwave signal to be transmitted onto the optical carrier with the signal modulation unit in a predetermined modulation state under the condition that a predetermined bias voltage is applied to form a modulated optical signal;
converting the modulated optical signal into an electrical signal using a photodetector;
wherein, in the predetermined modulation state, the signal modulation unit can suppress distortion components in the multi-octave microwave transmission device, so that the multi-octave microwave transmission device works in a state of a predetermined spurious-free dynamic range.
7. The method of claim 6, wherein the step of transmitting the multi-octave microwave signal comprises,
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 beam combiner;
the upper path 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 that a first bias voltage is applied to the optical carrier so as to form a first optical signal;
the down-path Mach-Zehnder modulator is used for receiving the optical carrier and working at a maximum transmission point under the condition of applying a second bias voltage so as to transmit the optical carrier;
the phase modulator is used for receiving the optical carrier output by the down-path Mach-Zehnder modulator and adjusting the phase of the optical carrier output by the down-path 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 modulated optical signal.
8. The multi-octave microwave transmission method according to claim 7, 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.
9. The method of claim 7 or 8, wherein the optical phase introduced by the first bias voltage satisfies the following equation 1,
[1] a＝πVb1/Vπ
and/or the optical phase introduced by the second bias voltage satisfies the following equation 2,
[2] b＝πVb2/Vπ
wherein, VπFor a half-wave voltage of the signal modulation unit, a denotes an optical phase introduced by the first bias voltage, Vb1Representing said first bias voltage, b representing the optical phase introduced by said second bias voltage, Vb2Representing the second bias voltage.
10. The method of claim 9, wherein 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)。
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