A photoelectric fusion superheterodyne terahertz channel monitoring system

Abstract

The present invention proposes an optoelectronic fusion superheterodyne terahertz channel monitoring system, which belongs to the field of millimeter wave / terahertz information technology. The system includes a terahertz receiving unit, an optical radio frequency unit, a tuned optical local oscillator unit, an optoelectronic down-conversion unit, and a filtering and processing unit. The system uses a frequency sweeping laser as a tuned optical local oscillator unit to output a tuned optical local oscillator signal, which is optically mixed with a terahertz signal or an intermediate frequency signal loaded into the optical frequency domain and down-converted to the baseband for processing. The present invention makes full use of the large bandwidth characteristics of optoelectronic frequency conversion devices, overcomes the electronic bottleneck of signal processing in the traditional electrical frequency domain, and directly realizes ultra-wideband terahertz signal monitoring on a single-channel monitoring machine; it also uses a bandpass optical filter to conveniently monitor the optical radio frequency signal in sections, and realizes multi-channel optoelectronic fusion superheterodyne terahertz channel monitoring, which not only greatly improves the test rate, but also can effectively expand the frequency test coverage.

Description

Technical Field

[0001] The invention belongs to the field of millimeter wave / terahertz information technology, and in particular relates to an optoelectronic fusion superheterodyne terahertz channel monitoring system. Background Art

[0002] The terahertz channel monitor is a key device for monitoring and identifying channel environment signals in frequency-adaptive terahertz communication, radar and other systems. It is crucial for electromagnetic environment monitoring, adaptive frequency allocation, anti-interference and anti-interception in the terahertz frequency band. High frequency band and ultra-wideband are one of the main characteristics of the terahertz system. In recent years, as the working frequency band continues to develop towards higher frequency bands, the working bandwidth of the system has also continued to increase. Higher requirements are put forward for the receiving bandwidth, receiving sensitivity, and spectrum resolution of the channel monitor. The channel monitor based on superheterodyne reception uses a tunable local oscillator to heterodyne down-convert the signal to be tested to the intermediate frequency or baseband frequency band, and then performs digital-to-analog conversion to obtain information such as the frequency, bandwidth, phase, and signal modulation system of the signal to be tested. The superheterodyne channel monitor has a large receiving dynamic range and high receiving sensitivity. It has advantages in high-frequency and weak signal reception, and the output signal has high selectivity and good frequency characteristics, and is easy to adjust. In order to suppress strong interference and make it have good selectivity, pre-selected RF filters and intermediate frequency filters are generally installed in the superheterodyne channel monitor. However, the traditional pure electronic superheterodyne channel monitoring machine based on electric filters is limited by the bandwidth and power roll-off of the tunable local oscillator source and the electric filter in the high frequency band. When receiving high-frequency broadband signals, it often needs multi-stage frequency conversion and requires a large number of filters, mixers and local oscillator signals. It has problems such as large size and power consumption, poor electromagnetic compatibility, and it is difficult to meet the needs of ultra-wide bandwidth spectrum monitoring in the terahertz frequency band.

[0003] The optoelectronic fusion channel monitoring technology modulates the RF signal onto light, and then performs filtering, channelization, mixing and other processing in the optical domain, and then converts it back to an electrical signal of appropriate bandwidth through optoelectronic conversion to match the processing capabilities of the electronic devices in the subsequent digital processing module. Using photonic methods to process RF signals in the optical domain can make full use of the large bandwidth characteristics of optoelectronic frequency conversion devices such as electro-optical modulators and optoelectronic mixers, overcome the electronic bottleneck of signal processing in the traditional electrical domain, improve the sampling and control speed of signals, optimize and improve the performance of the channel monitoring machine in terms of processing bandwidth, dynamic range, frequency response flatness and anti-electromagnetic interference ability, and reduce the volume and weight of the system and reduce the system cost. At present, optoelectronic fusion channel monitoring technology has been widely studied and applied in the field of microwave photons. It can not only measure the instantaneous frequency of microwave signals, but also monitor many parameters such as bandwidth, signal modulation system, frequency shift, direction, etc. However, in the terahertz frequency band with higher frequencies and larger working bandwidths, there is still a lack of optoelectronic fusion terahertz channel monitoring machine solutions. Summary of the invention

[0004] In view of the defects of the prior art, the present invention proposes an optoelectronic fusion superheterodyne terahertz channel monitoring system, aiming to provide a technical solution that can be used for high-frequency band and ultra-wideband terahertz channel monitoring.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A photoelectric fusion superheterodyne terahertz channel monitoring system comprises a terahertz receiving unit, an optical radio frequency unit, a tuned optical local oscillator unit, a photoelectric down-conversion unit and a filtering and processing unit.

[0007] The terahertz receiving unit is used to receive the terahertz signal to be measured, and directly load the terahertz signal to be measured or load it to the optical radio frequency unit after processing; the processing method is amplification and / or down-conversion to an intermediate frequency, and the terahertz signal to be measured is down-converted to an intermediate frequency to obtain an intermediate frequency signal.

[0008] The optical radio frequency unit is used to load the received terahertz signal or intermediate frequency signal into the optical frequency domain, obtain the optical radio frequency signal and transmit it to the optoelectronic down-conversion unit.

[0009] The tunable optical local oscillator unit includes a frequency sweeping laser, which is used to generate an optical local oscillator signal with tunable wavelength and transmit it to the optoelectronic down-conversion unit.

[0010] The optoelectronic down-conversion unit is used to optically mix the optically carried radio frequency signal with the optical local oscillator signal and down-convert it to baseband, obtain the difference frequency signal and transmit it to the filtering and processing unit.

[0011] The filtering and processing unit is used to filter the difference frequency signal to obtain a baseband signal, and then obtain information of the terahertz signal to be measured through sampling and digital processing.

[0012] Furthermore, the optical radio frequency unit includes a frequency-stabilized laser, an electro-optical modulator and at least one optical filter; wherein the frequency-stabilized laser is used to generate a carrier frequency signal and load it to the electro-optical modulator; the electro-optical modulator is used to receive the carrier frequency signal and the terahertz signal or the intermediate frequency signal, modulate and generate an optical radio frequency signal; the optical filter is used to pass-band filter the optical radio frequency signal. By using multiple band-pass optical filters and corresponding tuned optical local oscillator units and optoelectronic down-conversion units, the optical radio frequency signal can be monitored in sections, realizing a multi-channel optoelectronic fusion superheterodyne terahertz channel monitoring machine, expanding the frequency test coverage and improving the test rate.

[0013] Further, when the number of optical radio frequency signals output by the optical radio frequency unit is n, the number of the tuned optical local oscillator units and the optoelectronic down-conversion units is also n.

[0014] Furthermore, the optoelectronic down-conversion unit is an optoelectronic mixer.

[0015] Furthermore, the filtering and processing unit includes an electrical filter and an analog-to-digital converter (ADC); the electrical filter is a low-pass filter, which is used to filter the difference frequency signal to obtain a baseband signal, and input it into the analog-to-digital converter for sampling and digital processing to obtain information of the terahertz signal to be measured.

[0016] Furthermore, the optical filter is a bandpass filter.

[0017] The advantages of the present invention are as follows:

[0018] 1. The optoelectronic fusion superheterodyne terahertz channel monitoring system proposed in the present invention adopts a frequency sweeping laser to output a tuned optical local oscillator signal, does not require a tuned radio frequency local oscillator source, and does not require frequency doubling, and can be directly applied to frequency sweeping monitoring in the terahertz frequency band.

[0019] 2. The optoelectronic fusion superheterodyne terahertz channel monitoring system proposed in the present invention makes full use of the large bandwidth characteristics of optoelectronic frequency conversion devices such as electro-optical modulators and optoelectronic mixers, overcomes the electronic bottleneck of signal processing in the traditional electrical domain, and can directly realize ultra-wideband terahertz signal monitoring on a single-channel monitoring machine.

[0020] 3. The optoelectronic fusion superheterodyne terahertz channel monitoring system proposed in the present invention can also utilize a bandpass optical filter array to conveniently perform segmented monitoring of the optically carried radio frequency signal, thereby realizing a multi-channel optoelectronic fusion superheterodyne terahertz channel monitoring machine, which can not only greatly improve the test rate, but also effectively expand the frequency test coverage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of an intermediate frequency-based optoelectronic fusion superheterodyne terahertz channel monitoring machine proposed in Example 1.

[0022] Figure 2 This is a schematic diagram of the structure of a photoelectric fusion superheterodyne terahertz channel monitoring device for terahertz direct up-conversion in the optical frequency domain proposed in Example 2.

[0023] Figure 3 This is a schematic diagram of the structure of a multi-channel optoelectronic fusion superheterodyne terahertz channel monitoring machine proposed in Example 3. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0025] Example 1

[0026] A schematic diagram of the structure of an optoelectronic fusion superheterodyne terahertz channel monitoring machine based on intermediate frequency, such as Figure 1 Its basic structure and working process are as follows:

[0027] The terahertz receiving unit is composed of an antenna, a power amplifier, a terahertz local oscillator and a terahertz electric mixer. THz After receiving and amplifying, the local oscillator signal f generated by the terahertz local oscillator source LO The intermediate frequency signal f is down-converted by the terahertz mixer THz -f LO ; The intermediate frequency signal f THz -f LO It is loaded onto the electro-optic modulator of the optical radio frequency unit through the radio frequency cable.

[0028] The optical radio frequency unit includes a frequency-stabilized laser, an electro-optical modulator, and an optical filter; the carrier frequency signal f 0 and the intermediate frequency signal f THz -f LO The optical radio frequency signal f is modulated by the electro-optic modulator 0 +f THz -f LO , and then the light-carrying RF signal is filtered out through a bandpass optical filter and transmitted to the optoelectronic mixer.

[0029] Optical radio frequency signal f 0 +f THz -f LO The tuned optical local oscillator signal f L After the optical fiber is combined, it is input into the optoelectronic mixer for mixing to obtain the difference frequency signal f L -f 0 -f THz +f LO And input to the low-pass electric filter of the filtering and processing unit.

[0030] When the difference frequency signal is within the range of the low-pass filter, the output baseband signal f B The ADC is used for analog-to-digital conversion to obtain the frequency f of the terahertz signal to be measured. THz =f L -f 0 +f LO -f B , phase, bandwidth, signal modulation system, frequency shift, direction.

[0031] The advantage of this embodiment is that the bandwidth of the electro-optic modulator is not required to reach the terahertz frequency band, and the terahertz channel monitoring requirement can be met as long as the instantaneous modulation bandwidth range of communication or radar is covered.

[0032] Example 2

[0033] A terahertz direct up-conversion optical frequency domain optoelectronic fusion superheterodyne terahertz channel monitoring device, such as Figure 2 As shown, its basic composition and working process are as follows:

[0034] The terahertz receiving unit is composed of an antenna and a power amplifier. THz After receiving and amplifying, it is directly loaded onto the electro-optic modulator.

[0035] The carrier frequency signal f output by the stabilized laser 0 and the terahertz signal f THz The optical radio frequency signal f is modulated by the electro-optic modulator 0 +f THz , and then the light-carrying RF signal is filtered out through a bandpass optical filter and transmitted to the optoelectronic mixer.

[0036] Optical radio frequency signal f 0 +f THz The tuned optical local oscillator signal f L After the optical fiber is combined, it is input into the optoelectronic mixer for mixing to obtain the difference frequency signal f L -f 0 -f THz And input to the low-pass electric filter of the filtering and processing unit.

[0037] When the difference frequency signal is within the range of the low-pass filter, the output baseband signal f B The ADC is used for analog-to-digital conversion to obtain the frequency f of the terahertz signal to be measured. THz =f L -f 0 -f B、 , phase, bandwidth, signal modulation system, frequency shift, direction.

[0038] The advantage of this embodiment is that it does not require a terahertz local oscillator and a terahertz electric mixer, and can directly cover ultra-wideband signal monitoring from DC to terahertz frequency bands.

[0039] Example 3

[0040] A multi-channel optoelectronic fusion superheterodyne terahertz channel monitoring machine, such as Figure 3 As shown, its basic composition and working process are as follows:

[0041] The terahertz receiving unit is composed of an antenna, and the terahertz signal to be measured f THz After receiving, it is directly loaded onto the electro-optical modulator.

[0042] The carrier frequency signal f output by the stabilized laser 0 and the terahertz signal f THz The optical radio frequency signal f is modulated by the electro-optic modulator 0 +f THz , and then divided into n channels to enter optical filters with different bandpass ranges to monitor the optically carried RF signal in sections; among them, the first channel monitors DC~f 0 +f 1 The terahertz signal in the range, the second channel monitors f 0 +f 1 ~f 0 +f 2 The terahertz signal in the range, ..., the nth channel monitoring f 0 +f n-1 ~f 0 +f n The terahertz signal in the range. The optical radio frequency signal f filtered by the bandpass optical filter of each channel 0 +f THz The tuned optical local oscillator signal f output by the corresponding channel swept laser Ln After the optical fiber is combined, it is input into the optoelectronic mixer for mixing to obtain the difference frequency signal f of the two in each channel. Ln -f 0 -f THz And input to the low-pass electric filter of the filtering and processing unit.

[0043] When the difference frequency signal is within the range of the low-pass filter, the output baseband signal f B The ADC is used for analog-to-digital conversion to obtain the frequency f of the terahertz signal to be measured. THz =f L -f 0 -f B , phase, bandwidth, signal modulation system, frequency shift, direction.

[0044] The advantage of this embodiment is that the multi-channel segmented test can not only greatly improve the rate, but also effectively expand the frequency test coverage.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An optoelectronic fusion superheterodyne terahertz channel monitoring system, It is characterized in that It includes a terahertz receiving unit, an optical radio frequency unit, a tuned optical local oscillator unit, an optoelectronic down-conversion unit, and a filtering and processing unit; The terahertz receiving unit is used to receive the terahertz signal to be measured, and directly load the terahertz signal to be measured or load it to the optical radio frequency unit after processing; the processing method is amplification and / or down-conversion to an intermediate frequency, and the terahertz signal to be measured is down-converted to an intermediate frequency to obtain an intermediate frequency signal; The optical radio frequency unit is used to load the received terahertz signal or intermediate frequency signal into the optical frequency domain to obtain the optical radio frequency signal and transmit it to the optoelectronic down-conversion unit; The tunable optical local oscillator unit includes a frequency-sweeping laser, which is used to generate an optical local oscillator signal with tunable wavelength and transmit it to the optoelectronic down-conversion unit; The optoelectronic down-conversion unit is used to optically mix the optically carried radio frequency signal with the optical local oscillator signal and down-convert it to baseband, obtain the difference frequency signal and transmit it to the filtering and processing unit; The filtering and processing unit is used to filter the difference frequency signal to obtain a baseband signal, and then obtain information of the terahertz signal to be measured through sampling and digital processing.

2. The optoelectronic fusion superheterodyne terahertz channel monitoring system according to claim 1, It is characterized in that The optical radio frequency unit includes a frequency-stabilized laser, an electro-optical modulator and at least one optical filter; wherein the frequency-stabilized laser is used to generate a carrier frequency signal and load it to the electro-optical modulator; the electro-optical modulator is used to receive the carrier frequency signal and the terahertz signal or the intermediate frequency signal, and modulate to generate an optical radio frequency signal; the optical filter is used to pass-band filter the optical radio frequency signal.

3. The optoelectronic fusion superheterodyne terahertz channel monitoring system according to claim 2, It is characterized in that When the number of optical radio frequency signals output by the optical radio frequency unit is n, the number of the tunable optical local oscillator units and the optoelectronic down-conversion units is n.

4. The optoelectronic fusion superheterodyne terahertz channel monitoring system according to claim 2 or 3, It is characterized in that The optoelectronic down-conversion unit is an optoelectronic mixer.

5. The optoelectronic fusion superheterodyne terahertz channel monitoring system according to claim 4, It is characterized in that The filtering and processing unit includes an electric filter and an analog-to-digital converter; the electric filter is a low-pass filter, which is used to filter the difference frequency signal to obtain a baseband signal, and input it into the analog-to-digital converter for sampling and digital processing to obtain information of the terahertz signal to be measured.

6. The optoelectronic fusion superheterodyne terahertz channel monitoring system according to claim 4, It is characterized in that The optical filter is a bandpass filter.

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