A novel broadband microwave photonic channelized reception method

Abstract

This invention discloses a novel broadband microwave photonic channelized reception method, relating to the fields of microwave technology and optical communication technology. As shown in Figure 1 of the specification, the method involves a continuous light source splitting into two paths via an optical coupler: one path is frequency-shifted and modulated by a broadband radio frequency signal with carrier suppression double-sideband modulation, then replicated multiple times via the optical coupler; the other path serves as a seed light source, with a local oscillator signal source of the same frequency generating an even-order local oscillator optical frequency comb and an odd-order local oscillator optical frequency comb, which are then demultiplexed; the multiple comb teeth after demultiplexing, along with the replicated optical signals, are then fed into multiple high image suppression optical domain mixing and demodulation modules, achieving channelized reception of broadband microwave signals. This invention overcomes the problems of insufficient precision and severe crosstalk in optical filters, as well as the technical difficulties in generating multi-comb lines, wide spacing, and stable coherence dual optical frequency combs in traditional dual-comb reception schemes.

Description

Technical Field

[0001] This invention relates to the fields of optical communication technology and microwave technology, and mainly to the channelized reception of broadband microwave signals using photonics technology. Background Technology

[0002] With the rapid development of communication technology, the bandwidth required for signal transmission is constantly increasing. In some fields, there is a growing demand for the ability to simultaneously process broadband radio frequency (RF) signals at frequencies of several gigahertz or even tens of gigahertz. This not only requires RF receivers to have large instantaneous bandwidth, high resolution, and a wide dynamic range, but also the ability to handle signals arriving simultaneously at multiple frequencies and in different bands. Channelized reception is one of the effective methods for achieving simultaneous reception of broadband, multi-frequency signals.

[0003] Although channelized signal reception can be achieved using digital or analog filter banks, its application is severely limited by the bandwidth constraints of analog-to-digital conversion and the electronic bottlenecks of current electronic devices, significantly restricting the broadband applications of electronic channelized receivers. Microwave photonics technology, which integrates optical and microwave technologies, offers numerous advantages such as ultra-large instantaneous bandwidth, strong resistance to electromagnetic interference, low loss, and lightweight design, effectively addressing the bandwidth and electronic bottlenecks currently encountered in microwave channelized receiver systems.

[0004] Currently reported microwave photonic channelized reception schemes mainly fall into two categories: one is a channelized reception scheme based on photonic filter banks; the other is a channelized reception scheme based on dual optical frequency combs with image suppression. The first type of scheme primarily achieves signal replication by modulating the intercepted broadband microwave signal into an optical frequency comb, followed by channel segmentation using equally spaced photonic filters. The local oscillator optical frequency comb then down-converts the different sub-channels. Its advantage is its simple structure, but its disadvantages include implementation difficulties and high precision requirements for the photonic filters. The second type of scheme also utilizes a signal optical frequency comb to replicate the broadband microwave signal. A coherent local oscillator optical frequency comb down-converts each replicated RF signal and employs an image suppression reception scheme, solving the image interference problem commonly found in superheterodyne receivers. The disadvantage is that the number of teeth on the optical frequency comb directly determines the number of sub-channels in the channelized reception system, and flatness and sideband suppression ratio directly affect the degree of signal distortion. Therefore, an optical frequency comb with a large number of teeth, wide tooth spacing, high flatness, and high sideband suppression ratio is required, but achieving such an ideal optical frequency comb is extremely difficult. Summary of the Invention

[0005] To address the problems existing in the technical background and optimize the performance of channelized receivers, this invention proposes a novel broadband microwave photonic channelized reception method.

[0006] Traditional dual-optical-comb schemes utilize a signal optical frequency comb to replicate multiple broadband radio frequency (RF) signals, while simultaneously employing a coherent local oscillator (LOO) optical frequency comb to down-convert each replicated RF signal. Finally, a mirror-suppression receiving scheme is used for demodulation to obtain multiple channels. Compared to the traditional dual-optical-comb scheme, the scheme presented in this paper only requires the LOO optical frequency comb to directly divide the modulated signal into channels, eliminating the need for a signal optical frequency comb. Furthermore, this scheme generates odd and even LOO optical frequency combs from the same LO source, replacing the wide-spacing, multi-comb, high-flatness, and stable coherent dual-optical-frequency-comb approach, thus reducing the complexity of optical frequency comb implementation. Since the spacing between the odd and even optical frequency comb teeth is twice that of the RF LO source, the accuracy requirements for photonic filters are reduced, and the system structure is simple and easy to implement. For example, if the traditional dual-optical-comb scheme is used to generate N channels with bandwidth B... ch For a channel to function properly, a local oscillator optical frequency comb with N comb lines and a signal optical frequency comb are required, with the spacing between the comb teeth f. RF It must be large enough and satisfy f RF >2N·B ch Using this scheme, N identical bandwidths of B are generated. ch The channel only requires two local oscillator optical frequency combs, one generating N1 comb teeth and the other generating N2 comb teeth where N1 + N2 = N / 2, and the spacing between the comb teeth is 4B. ch Therefore, it can be seen that this scheme reduces the requirements for the radio frequency band in realizing wide-spacing, multi-comb optical frequency combs, and also reduces the accuracy requirements for optical filters. Since the upper and lower electro-optic modulators operate at the maximum and minimum transmission points respectively, and the comb teeth of the N1 fundamental oscillator optical frequency comb are of even order and the comb teeth of the N2 fundamental oscillator optical frequency comb are of odd order, seamless channelized reception of signals can be achieved.

[0007] The high image suppression optical domain mixing and demodulation module consists of a 90° optical mixing coupler, two balanced detectors, two subtractors, and a 90° bridge. This demodulation module employs a balanced detector structure, which suppresses common-mode spurious components, improves the signal-to-noise ratio, and ensures high system stability.

[0008] The technical solution adopted in this invention is as follows: the device includes a laser source, an optical coupler, an optical frequency shifting module, a suppressed carrier double-sideband modulation module, an electro-optic modulator, an erbium-doped fiber optic amplifier, a wavelength division multiplexer, a 90° optical hybrid coupler, a balanced photodetector, and a 90° bridge.

[0009] The light source output is first split into two paths by a first optical coupler 20 with two outputs: the upper optical carrier is input to a frequency shift module 30, and the generated frequency-shifted optical carrier serves as the input to a carrier suppression double-sideband modulation module 40, loading the intercepted broadband radio frequency signal onto the RF input of this module. The output modulation signal is amplified by a first optical amplifier 50 and then input to a multi-output third optical coupler 70; the lower optical carrier passes through a second optical coupler 601 with two outputs and is input to two parallel first electro-optic modulators 602 and second electro-optic modulators 606, respectively, and the local oscillator signal f generated by the local oscillator source 604 is... LO After passing through the first amplifier 603 and the second amplifier 605, the signals are input to the radio frequency input terminals of the first electro-optic modulator 602 and the second electro-optic modulator 606, respectively, to generate odd-order local oscillator optical frequency combs and even-order local oscillator optical frequency combs with the same comb tooth spacing.

[0010] The multiple modulation signals output from the third optical coupler 70 are input to the high image suppression optical domain mixing and demodulation module 100 along with the demultiplexed local oscillator optical frequency comb. For example, the first output of the third optical coupler 70 and the first output of the first demultiplexer 80 are simultaneously input to the high image suppression optical domain mixing and demodulation module 100. The module outputs a down-converted signal with image suppression mixing effect, which is then processed in the digital signal processing module 110.

[0011] The suppressed carrier double-sideband modulation module 40 consists of a third electro-optic modulator 401 operating in the suppressed carrier double-sideband state.

[0012] The high image suppression optical domain mixing and demodulation module 100 consists of a 90° optical mixing coupler 1001, two balanced photodetectors (balanced photodetector 1002 and balanced photodetector 1003), two subtractors (subtractor 1004 and subtractor 1005), and a 90° bridge 1006.

[0013] The 90° optical hybrid coupler 1001 consists of four optical couplers with different phases, two inputs and four outputs.

[0014] The balanced photodetector 1002 consists of two photodetectors with the same or similar performance. The output of the balanced photodetector is the result of subtracting the outputs of the two photodetectors.

[0015] The present invention includes the following steps in operation:

[0016] (1) The light carrier with wavelength λ emitted from the light source is divided into upper and lower paths by the first optical coupler 20.

[0017] (2) In the upper path, the optical carrier first passes through the frequency shift module 30 to generate the frequency-shifted optical carrier. (3) The frequency-shifted optical carrier is input to the input of the carrier suppression double-sideband modulation module 40, and the broadband radio frequency signal that needs to be channelized is loaded onto its radio frequency input.

[0018] (4) The output modulation signal is amplified by the first optical amplifier 50 and then input to the third optical coupler 70.

[0019] (5) In the lower path, the optical carrier is divided into an upper branch and a lower branch by the second optical coupler 601. The upper branch optical carrier passes through the first electro-optic modulator 602, and the local oscillator signal f LO After amplification, the signal is fed into the radio frequency input terminal of the first electro-optic modulator 602. The first electro-optic modulator 602 operates at the maximum transmission point, generating an even-order local oscillator optical frequency comb, which then enters the first dewavelength division multiplexer 80 after passing through the second optical amplifier 607.

[0020] (6) In the lower branch, the optical carrier passes through the second electro-optic modulator 606, and the local oscillator signal f LO After being amplified, the signal is fed into the radio frequency input terminal of the second electro-optic modulator 606. The second electro-optic modulator 606 operates at the minimum transmission point, generating an odd-order local oscillator optical frequency comb, which then enters the second dewavelength division multiplexer 90 after passing through the third optical amplifier 608.

[0021] (7) The multi-channel modulation signal generated by the third optical coupler 70 and the corresponding local oscillator optical frequency comb demultiplexed by the first demultiplexer 80 and the second demultiplexer 90 are input into the 90° optical hybrid coupler 1001 to generate four optical signals.

[0022] (8) The generated optical signal is input into the first balanced photodetector 1002 and the second balanced photodetector 1003, and outputs I and Q signals respectively.

[0023] (9) Input the I and Q signals into the 90° bridge 1006.

[0024] This invention proposes a novel broadband microwave photonic channelization reception method that eliminates the need for using a signal optical frequency comb to replicate the broadband radio frequency signal requiring channelization. This avoids the generation of wide-spaced, multi-comb, coherently stable dual optical frequency combs, thus reducing system complexity. The frequency spacing between the comb teeth is 4B. ch This also reduces the requirement for high-precision photonic filters. Furthermore, since the local oscillator optical frequency combs of the upper and lower paths operate at the maximum and minimum transmission points respectively, a gapless channelized system can be achieved. Attached Figure Description

[0025] Figure 1 .Structural diagram of a novel broadband microwave photonic channelized receiver method.

[0026] Figure 2 Schematic diagram of suppressing carrier double-sideband modulation.

[0027] Figure 3 Taking 14-channel channelized reception as an example, the spectrum diagrams of channels A, B, C, D, E, and F are shown. Detailed Implementation

[0028] The implementation of the present invention will be described in detail below with reference to the accompanying drawings: This example is implemented under the premise of the technical solution of the present invention, and provides detailed implementation methods and specific operation procedures, but the protection scope of the present invention is not limited to the following embodiments.

[0029] like Figure 1 As shown, the device includes a laser source, an optical coupler, a frequency shifting module, a carrier-suppressed double-sideband modulation module, an electro-optic modulator, an amplifier, a wavelength division multiplexer, a 90° optical hybrid coupler, a balanced photodetector, and a 90° bridge.

[0030] This example includes the following steps:

[0031] (1) The light source generates a continuous light wave with a working wavelength of 1550nm and a power of 0dBm. After passing through the first optical coupler 20, the light wave is first split into two paths; the center frequency of the continuous light wave is f. c .

[0032] (2) In the upper path, the optical carrier passes through a frequency shift of f. s The frequency shift module 30 inputs the frequency-shifted optical carrier to the carrier suppression double-sideband modulation module 40, where f s =17.5GHz. It should be noted that this module is composed of a third electro-optic modulator 401 operating in carrier-suppressed double-sideband. The broadband microwave signal that needs to be channelized is added to the radio frequency input terminal of the third electro-optic modulator 401. The resulting modulated signal is amplified by the first optical amplifier 50 and then input into the third optical coupler 70 with multi-port output.

[0033] (3) In the lower path, the optical carrier is divided into upper and lower branches by the second optical coupler 601. The upper branch optical carrier is input to the first electro-optic modulator 602 operating at the maximum transmission point. The local oscillator signal source 604 outputs a 5GHz sine signal, which is loaded onto its radio frequency input terminal by the first electrical amplifier 603. The modulation index m = 3.02 is selected to generate four local oscillator optical frequency combs with a frequency interval of 10GHz.

[0034] (4) In the lower path, the optical carrier of the lower branch after passing through the second optical coupler 601 is input to the second electro-optic modulator 606 operating at the minimum transmission point. The local oscillator signal source 604 outputs a 5GHz sine signal, which is loaded onto its radio frequency input terminal by the second electrical amplifier 605. The modulation index m = 1.82 is selected to generate a three-root optical frequency comb with a frequency interval of 10GHz.

[0035] (5) For example: the first output port of the third optical coupler 70 corresponds to the first output port of the first dewavelength division multiplexer 80. The copied modulation signal and the corresponding local oscillator optical frequency comb are input into the 90° optical hybrid coupler 1001 to obtain four output signals.

[0036] (6) Subsequently, the four output signals are input to the first balanced photodetector 1002 and the second balanced photodetector 1003, and four signals are output. The first and second output signals are subtracted to obtain the intermediate frequency signal I. The third and fourth output signals are subtracted to obtain the intermediate frequency signal Q.

[0037] (7) Input the I and Q signals into the 90° bridge 1006, output two down-conversion signals, and input the down-conversion signals into the digital signal processing module 110.

[0038] (8) Therefore, this example can realize 14 channels, with the upper branch generating 4 optical frequency combs with a frequency spacing of 10 GHz and the lower branch generating 3 optical frequency combs with a frequency spacing of 10 GHz. The detection bandwidth of the balanced detector is 2.5 GHz, so it can realize 14 channels in the range of 0-2.5 GHz, 2.5-5 GHz, ... 32.5-35 GHz.

[0039] In summary, the above-described implementation schemes are merely embodiments of the present invention. It should be noted that, without departing from the essence of the method and core device of the present invention, several modifications and refinements can be made in actual implementation and should also be included within the protection scope of the present invention.

Claims

1. A novel broadband microwave photonic channelized reception method, characterized in that, The steps include the following: Step 1: Use the first optical coupler (20) to split the output of the laser source (10) into two identical optical carriers; Step 2: One optical carrier enters the carrier suppression double-sideband module (40) through the optical frequency shifting module (30). The carrier suppression double-sideband module (40) is composed of a third electro-optic modulator (401). The frequency-shifted optical carrier is modulated by the intercepted broadband radio frequency signal through the third electro-optic modulator (401). The generated modulated signal enters the third optical coupler (70) with multi-port output through the first optical amplifier (50). Step 3: Another optical carrier enters two parallel electro-optic modulators (602 and 606) via the second optical coupler (601), and their bias voltages are controlled to generate even-order local oscillator optical frequency combs and odd-order local oscillator optical frequency combs, which are then amplified and input into the first dewavelength division multiplexer (80) and the second dewavelength division multiplexer (90), respectively. Step 4: Input the multi-channel modulation signal output from the third optical coupler (70) and the demultiplexed local oscillator optical frequency comb into the corresponding high image suppression optical domain mixing and demodulation module (100).

2. The novel broadband microwave photonic channelized reception method according to claim 1, characterized in that, The third electro-optic modulator (401) in step 2 must operate in carrier-suppressed double-sideband mode.

3. The novel broadband microwave photonic channelized reception method according to claim 1, characterized in that, The even-order local oscillator optical frequency combs (0, ±2, ±4…) in step 3 are generated by the first electro-optic modulator (602) operating at the maximum transmission point; the odd-order local oscillator optical frequency combs (±1, ±3…) in step 3 are generated by the second electro-optic modulator (606) operating at the minimum transmission point, thereby realizing gapless division of the signal spectrum. With the modulation index and RF input power, local oscillator optical frequency combs with adjustable comb spacing and good flatness can be generated as needed.

4. A novel broadband microwave photonic channelized reception method according to claim 1, characterized in that, The high image suppression optical domain mixing and demodulation module (100) in step 4 consists of a 90° optical mixing coupler (1001), a first balanced photodetector (1002), a second balanced photodetector (1003), a first subtractor (1004), a second subtractor (1005), and a 90° bridge (1006). After the demultiplexed local oscillator optical frequency comb and the modulated optical signal pass through the 90° optical mixing coupler (1001), the first balanced photodetector (1002), and the second balanced photodetector (1003), they output I and Q signals respectively. Finally, after passing through the 90° bridge (1006), a down-conversion signal with image suppression effect can be obtained.

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