Research

8 pages, 4421 KiB

Open AccessEditor’s ChoiceCommunication

Photonic-Assisted Microwave Frequency Measurement Using High Q-Factor Microdisk with High Accuracy

by Mengyao Zhao, Wenyu Wang, Lei Shi, Chicheng Che and Jianji Dong

Photonics 2023, 10(7), 847; https://doi.org/10.3390/photonics10070847 - 21 Jul 2023

Cited by 2 | Viewed by 1045

Frequency measurement plays a crucial role in radar, communication, and various applications. The photonic-assisted frequency measurement method offers several advantages, including resistance to electromagnetic interference, broad bandwidth, and low power consumption. Notably, frequency-to-time mapping enables the measurement of various microwave signal types, such [...] Read more.

Frequency measurement plays a crucial role in radar, communication, and various applications. The photonic-assisted frequency measurement method offers several advantages, including resistance to electromagnetic interference, broad bandwidth, and low power consumption. Notably, frequency-to-time mapping enables the measurement of various microwave signal types, such as single-frequency, multiple-frequency, frequency hopping, and chirped signals. However, the accuracy of this method is currently limited due to the absence of resonant devices with high-quality factors, which are essential for achieving higher-precision measurements. In this work, a frequency measurement method based on an ultrahigh-quality-factor microdisk is proposed. By establishing a correlation between the time difference and the frequency to be measured, a reduction in measurement error to below 10 MHz within a frequency measurement range of 3 GHz is realized. Our work introduces a new approach to frequency measurement using optical devices, opening new possibilities in this field. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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11 pages, 3705 KiB

Open AccessArticle

Broadband Microwave Photonic Mixer with Flexibly Tunable Phase Shift and Supporting Dispersion-Induced Power-Fading-Free Fiber Transmission

by Mingxiu Yuan, Di Peng, Yuwen Qin, Jianping Li, Meng Xiang, Ou Xu and Songnian Fu

Photonics 2023, 10(4), 432; https://doi.org/10.3390/photonics10040432 - 11 Apr 2023

Viewed by 1204

Abstract

A broadband microwave photonic mixer with tunable phase shift and supporting dispersion-induced power-fading-free fiber transmission is proposed and demonstrated based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM). In this scheme, the intermediate-frequency (IF)/radiofrequency (RF) signal and the local oscillation (LO) signal are applied [...] Read more.

A broadband microwave photonic mixer with tunable phase shift and supporting dispersion-induced power-fading-free fiber transmission is proposed and demonstrated based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM). In this scheme, the intermediate-frequency (IF)/radiofrequency (RF) signal and the local oscillation (LO) signal are applied to the four sub-MZMs biased at their minimum transmission points via a power splitter and a 90° hybrid coupler, respectively. Through mutual beating between the IF/RF and the LO modulation sidebands in a high-speed photodetector at the remote site, high-efficiency frequency conversion is achieved. The dispersion-induced power fading over long-distance fiber transmission is eliminated through setting the biased-induced phase difference between the parent-MZMs in the two sub-DPMZMs of the DP-DPMZM to be π/2. In addition, the phase shift of the frequency-converted signal can be continuously tuned over 360° through synchronously adjusting the bias voltages of the parent-MZMs in the two sub-DPMZMs. The proposed scheme is experimentally demonstrated, where a microwave photonic mixer with a 6-dB operation bandwidth of 40 GHz and supporting dispersion-induced power-fading-free transmission over 20 km SMF is realized. Meanwhile, a continuously tunable phase shift over 360° in the frequency range of 0.1 GHz to 29.9 GHz is achieved, where the power variation during phase tuning is smaller than 4 dB. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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11 pages, 2193 KiB

Open AccessCommunication

Broadband Microwave Photonic Channelizer with 18 Channels Based on Acousto-Optic Frequency Shifter

by Bo Chen, Qunfeng Dong, Biao Cao, Weile Zhai and Yongsheng Gao

Photonics 2023, 10(2), 107; https://doi.org/10.3390/photonics10020107 - 20 Jan 2023

Viewed by 1433

Abstract

A microwave photonic channelizer can achieve instantaneous reception of ultra-wideband signals and effectively avoid electronic bottleneck; therefore, it can be perfectly applied to a wideband radar system and electronic warfare. In channelization schemes based on an optical frequency comb (OFC), the number of [...] Read more.

A microwave photonic channelizer can achieve instantaneous reception of ultra-wideband signals and effectively avoid electronic bottleneck; therefore, it can be perfectly applied to a wideband radar system and electronic warfare. In channelization schemes based on an optical frequency comb (OFC), the number of comb lines usually depends on that of the sub-channels. In order to improve the utilization rate of the comb lines of OFC, we propose a scheme to shift the frequency of OFC by using an acousto-optic frequency shifter (AOFS), which can obtain three times the number of sub-channels of the comb lines of an OFC. In order to simplify the experiment, only a three-line OFC is used in the experiment. A three-line local oscillator (LO) OFC is frequency-shifted up and down by two AOFSs, and nine optical LO signals with different frequencies are obtained, thereby realizing the simultaneous reception of eighteen sub-channels. The proposed scheme enjoys a large number of sub-channels and minimal channel crosstalk. Experimental results demonstrate that a 9-GHz bandwidth RF signal covering 10–19 GHz is divided into 18 sub-channels with a sub-bandwidth of 500 MHz. The image rejection ratio of the sub-channels is about 23 dB, and the spurious-free dynamic range (SFDR) of the receiver can reach 98 dB·Hz^2/3. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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13 pages, 4215 KiB

Open AccessArticle

Image-Rejected Multi-Band Frequency Down-Conversion Based on Photonic Sampling

by Liuzhu Xu, Di Peng, Yuwen Qin, Jianping Li, Meng Xiang, Ou Xu and Songnian Fu

Photonics 2023, 10(1), 35; https://doi.org/10.3390/photonics10010035 - 29 Dec 2022

Viewed by 1470

Abstract

An image-rejected multi-band frequency down-conversion scheme is proposed and experimentally demonstrated based on photonic sampling. The multi-band radio-frequency (RF) signals to be processed are copied into two replicas in quadrature, which are then sampled by an ultra-short optical pulse train via a polarization-multiplexed [...] Read more.

An image-rejected multi-band frequency down-conversion scheme is proposed and experimentally demonstrated based on photonic sampling. The multi-band radio-frequency (RF) signals to be processed are copied into two replicas in quadrature, which are then sampled by an ultra-short optical pulse train via a polarization-multiplexed modulator. After polarization demultiplexing and detection using a pair of low-speed photodetectors, the multi-band RF signals are simultaneously down-converted to the intermediate frequency (IF) band. The image components can be suppressed by quadrature coupling the two generated IF signals via an electrical 90° hybrid coupler (HC). In the experiment, multi-band RF signals in the frequency range of 6 GHz to 39 GHz are down-converted to the IF band below 4 GHz using a local oscillator (LO) signal at 8 GHz to generate the ultra-short optical pulse train. Image rejection is achieved in the digital domain using digital signal processing to compensate for the amplitude and phase mismatch between the two IF signals and to implement quadrature coupling. In addition, through using an electrical phase shifter, an electrical attenuator, and an electrical 90° HC to achieve quadrature coupling of the two IF signals, image-rejected multi-band frequency down-conversion is also verified in the analog domain. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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11 pages, 8408 KiB

Open AccessCommunication

A Microwave Photonics True-Time-Delay System Using Carrier Compensation Technique Based on Wavelength Division Multiplexing

by Yiru Zhao, Chaoquan Wang, Zeping Zhao, Weijie Zhang and Jianguo Liu

Photonics 2023, 10(1), 34; https://doi.org/10.3390/photonics10010034 - 28 Dec 2022

Viewed by 1270

Abstract

A novel microwave photonic true-time-delay (TTD) system using carrier compensation technology is proposed and experimentally demonstrated. Wavelength division multiplexing combines ten lasers into a single beam. We separate one channel from the laser as a compensating carrier, and the compensation carrier is combined [...] Read more.

A novel microwave photonic true-time-delay (TTD) system using carrier compensation technology is proposed and experimentally demonstrated. Wavelength division multiplexing combines ten lasers into a single beam. We separate one channel from the laser as a compensating carrier, and the compensation carrier is combined with the time-delayed optical signals to be detected. Meanwhile, sideband signals are amplified effectively thanks to carrier-suppressed double-sideband (CS-DSB) modulation. Therefore, the power of both the central optical carriers and sidebands is guaranteed, which produces a better beat frequency result than the TTD system without carrier compensation. The simulation results confirm that the signal amplitude has an order of magnitude improvement due to the compensation. With employing the delay fibers based on multiple-fiber Bragg gratings (MFBGs), the experimental delay and response time reach 90.160 μs and 160.80 ns. The proposed technique can find applications in time-delay beamforming of phased array antennas (PAAs). Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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9 pages, 3780 KiB

Open AccessCommunication

Broadband and Remote Electromagnetic Spectrum Sensing Based on Photonic Electric Field Sensor Chip

by Zhao Liu, Wenhao Du, Lan Zhao, Lijun Luo, Le Qiu, Lingjie Zhang, Bao Sun, Shangjian Zhang and Yong Liu

Photonics 2022, 9(12), 918; https://doi.org/10.3390/photonics9120918 - 29 Nov 2022

Viewed by 1287

Abstract

Electromagnetic spectrum sensing is quite important for communication safety in commercial wireless communication, as well as for the equipment paralysis of rivals and self-protection in modern warfare. Specifically, a passive electric field sensor featured with broadband, remote sensing capabilities and small size is [...] Read more.

Electromagnetic spectrum sensing is quite important for communication safety in commercial wireless communication, as well as for the equipment paralysis of rivals and self-protection in modern warfare. Specifically, a passive electric field sensor featured with broadband, remote sensing capabilities and small size is urgently needed to realize spectrum sensing. Here, we demonstrate a photonic electric field sensor operating in the frequency range of 10 MHz to 26.5 GHz. Based on the electric field sensor, distortion-free sensing of on–off keying signals centered at 3 GHz is achieved under a bit rate up to 40 Mb/s. In addition, remote electromagnetic spectrum sensing is also demonstrated up to 70 km, where the signal-to-noise ratio is measured to be larger than 20 dB. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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11 pages, 3265 KiB

Open AccessArticle

Broadband Signal Digitization Based on Low-Speed Non-Uniform Photonic Sampling

by Weiqiang Lyu, Zhengkai Li, Lingjie Zhang, Huan Tian, Zhenwei Fu, Zhiyao Zhang, Bao Sun, Yali Zhang, Shangjian Zhang, Heping Li and Yong Liu

Photonics 2022, 9(11), 831; https://doi.org/10.3390/photonics9110831 - 05 Nov 2022

Cited by 2 | Viewed by 1527

Abstract

A new non-uniform photonic sampling (NPS) strategy and its special signal reconstruction algorithm are proposed to achieve digital acquisition of broadband periodic signals at a low sampling rate. Compared with the existing schemes, the NPS strategy can largely reduce the sampling number to [...] Read more.

A new non-uniform photonic sampling (NPS) strategy and its special signal reconstruction algorithm are proposed to achieve digital acquisition of broadband periodic signals at a low sampling rate. Compared with the existing schemes, the NPS strategy can largely reduce the sampling number to acquire identical signal information as that obtained by using its equivalent high-speed uniform photonic sampling, which is beneficial for reducing the sampling time and the data volume of the NPS-based analog-to-digital converter (ADC). In addition, the calculation time of the proposed algorithm is millions of times lower than that of the digital alias-free signal processing (DASP) algorithm used before, which benefits from the fast Fourier transform calculation of a one-dimensional data array instead of a two-dimensional data array calculation in the DASP algorithm. A simulation is performed to validate the feasibility of the proposed scheme. In the simulation, a single-channel NPS-based ADC with an average sampling rate of 1 GSa/s is demonstrated by using the proposed NPS strategy and signal reconstruction algorithm. The results indicate the reconstructed signal information for a single-tone microwave signal at 9.9 GHz and a linear frequency modulation signal in the frequency range of 1 GHz to 9 GHz are identical to those obtained by using its equivalent high-speed uniform photonic sampling-based ADC with a sampling rate of 20 GSa/s. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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9 pages, 2634 KiB

Open AccessCommunication

Tunable Microwave Pulse Generation Based on an Actively Mode-Locked Optoelectronic Oscillator

by Jin Zhang, Depei Zhang, Maolong Zhang, Daikun Zheng, Anle Wang, Xiaotong Liu, Lei Hu, Xiaoniu Peng and Yalan Wang

Photonics 2022, 9(10), 772; https://doi.org/10.3390/photonics9100772 - 17 Oct 2022

Cited by 2 | Viewed by 1571

Abstract

A tunable microwave-pulse-generation scheme is proposed and demonstrated by employing an actively mode-locked optoelectronic oscillator (OEO) based on a microwave photonic filter (MPF). The MPF mainly consists of a phase-shifted fiber Bragg grating (PS-FBG) and a phase modulator. The microwave pulse trains with [...] Read more.

A tunable microwave-pulse-generation scheme is proposed and demonstrated by employing an actively mode-locked optoelectronic oscillator (OEO) based on a microwave photonic filter (MPF). The MPF mainly consists of a phase-shifted fiber Bragg grating (PS-FBG) and a phase modulator. The microwave pulse trains with variable repetition rates are achieved by injecting an external signal, of which the frequencies are equal to an integer multiple of the free spectrum range (FSR) of the OEO. The multi-mode oscillation mechanism is discussed in detail theoretically and experimentally. A microwave pulse train with a central frequency of 9.25 GHz and repetition rate of 1.68 MHz is demonstrated by setting the injecting signal frequency to be the same with the FSR of the OEO. A tunable center frequency of the microwave pulses from 5.47 GHz to 18.91 GHz can be easily generated by tuning the laser frequency benefit from adopting the MPF. Furthermore, the microwave pulses with different pulse periods of 297.62 ns, 198.69 ns, and 148.81 ns are also realized by harmonic mode-locking. The proposed tunable microwave-pulse-generation method has potential applications in the pulse Doppler radar and communications. Full article

(This article belongs to the Special Issue Microwave Photonic Techniques)

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