The photonic terahertz integrated sensing and communication (THz-ISAC) holds immense potential for enabling ultrahigh data rates and millimeter-resolution sensing, due to its exceptionally broad bandwidth. Nevertheless, the limited radiation power of existing THz sources restricts the full utilization of their broadband advantages in single-channel ISAC systems. In this work, a photonic THz-ISAC system model utilizing the chirp spread spectrum (CSS) waveform scheme is proposed and theoretically analyzed, by considering the noise contribution of the photonic THz transceiver and the free-space propagation loss (FSPL). Based on the proposed waveform, we derive the closed form of communication error vector magnitude (EVM) and radar sensing Cramér–Rao lower bound (CRLB), as well as the performance bounds. Then, a proof-of-concept experiment operating at 285 GHz is conducted to verify the performance of the CSS waveform, achieving 12 Gbit/s transmission with a 1.5 cm range resolution. In addition, the experiment validates the performance trade-offs among chirp bandwidth, data rate, and signal power, aligning well with our theoretical bounds. Therefore, the proposed scheme provides a design guideline for CSS-based photonic THz-ISAC systems.
{"title":"Photonic Chirp Spread Spectrum THz-ISAC: Constraints and Design Considerations","authors":"Zhidong Lyu;Lu Zhang;Qiuzhuo Deng;Xing Fang;Liga Bai;Oskars Ozolins;Hongqi Zhang;Guangyi Liu;Xiaodan Pang;Xianbin Yu","doi":"10.1109/TMTT.2025.3615239","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3615239","url":null,"abstract":"The photonic terahertz integrated sensing and communication (THz-ISAC) holds immense potential for enabling ultrahigh data rates and millimeter-resolution sensing, due to its exceptionally broad bandwidth. Nevertheless, the limited radiation power of existing THz sources restricts the full utilization of their broadband advantages in single-channel ISAC systems. In this work, a photonic THz-ISAC system model utilizing the chirp spread spectrum (CSS) waveform scheme is proposed and theoretically analyzed, by considering the noise contribution of the photonic THz transceiver and the free-space propagation loss (FSPL). Based on the proposed waveform, we derive the closed form of communication error vector magnitude (EVM) and radar sensing Cramér–Rao lower bound (CRLB), as well as the performance bounds. Then, a proof-of-concept experiment operating at 285 GHz is conducted to verify the performance of the CSS waveform, achieving 12 Gbit/s transmission with a 1.5 cm range resolution. In addition, the experiment validates the performance trade-offs among chirp bandwidth, data rate, and signal power, aligning well with our theoretical bounds. Therefore, the proposed scheme provides a design guideline for CSS-based photonic THz-ISAC systems.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"920-930"},"PeriodicalIF":4.5,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1109/TMTT.2025.3619072
Fang Liu;Shi-Xin Meng;Jin Xu;Hui-Kun Yang;Lei Zhu
This article presents a design method for active vector-sum phase shifter (VSPS) using hybrid microstrip-slotline quadrature signal (I/Q) generator. The proposed I/Q generator consists of a novel power divider (PD) and 90° fixed phase shifter (PS) and 180° tunable PS cascaded at its output ports for realizing I/Q signals covering four quadrants, where the equivalent circuit of the PDs and the even-odd mode analysis procedure are given to determine the circuit parameters. An active VSPS is obtained by cascading two identical variable gain amplifiers (VGAs) at the output port of the I/Q generator to control the amplitude of the I/Q signal. In order to validate the proposed design method, the hybrid microstrip-slotline PD, I/Q generator, VGA and active VSPS proposed in this article are simulated, fabricated, and measured. From the measured results, it can be seen that the insertion loss (IL), return loss (RL) and isolation of the proposed PD in the range of 1.32–2.78 GHz (71%) are better than 0.4, 10, and 14 dB, respectively. The core circuit size is only $0.005lambda _{g}^{2}$ . Within 1.7–2.3 GHz (30%), the RL, isolation, IL, phase difference and amplitude difference of the proposed I/Q generator are better than 11.5, 18.5, and 2 dB, $pm ~8^{circ }$ and $pm ~0.6$ dB, respectively. Within 1.74–2.3 GHz (27.7%), the input RL, output RL, root mean squares (rms) phase error and rms amplitude error of the proposed active VSPS are better than 11 dB, 10.5 dB, 6.1°, and 0.99 dB, respectively. The average gain at the center frequency and the circuit size are 7 dB and $0.29lambda _{g}^{2}$ , respectively. The experimental results demonstrate the feasibility of the design method in this article for compact broadband PDs, high-performance I/Q generators, and active VSPS.
{"title":"Design of Active Vector-Sum Phase Shifter Using Hybrid Microstrip-Slotline I/Q Generator","authors":"Fang Liu;Shi-Xin Meng;Jin Xu;Hui-Kun Yang;Lei Zhu","doi":"10.1109/TMTT.2025.3619072","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3619072","url":null,"abstract":"This article presents a design method for active vector-sum phase shifter (VSPS) using hybrid microstrip-slotline quadrature signal (I/Q) generator. The proposed I/Q generator consists of a novel power divider (PD) and 90° fixed phase shifter (PS) and 180° tunable PS cascaded at its output ports for realizing I/Q signals covering four quadrants, where the equivalent circuit of the PDs and the even-odd mode analysis procedure are given to determine the circuit parameters. An active VSPS is obtained by cascading two identical variable gain amplifiers (VGAs) at the output port of the I/Q generator to control the amplitude of the I/Q signal. In order to validate the proposed design method, the hybrid microstrip-slotline PD, I/Q generator, VGA and active VSPS proposed in this article are simulated, fabricated, and measured. From the measured results, it can be seen that the insertion loss (IL), return loss (RL) and isolation of the proposed PD in the range of 1.32–2.78 GHz (71%) are better than 0.4, 10, and 14 dB, respectively. The core circuit size is only <inline-formula> <tex-math>$0.005lambda _{g}^{2}$ </tex-math></inline-formula>. Within 1.7–2.3 GHz (30%), the RL, isolation, IL, phase difference and amplitude difference of the proposed I/Q generator are better than 11.5, 18.5, and 2 dB, <inline-formula> <tex-math>$pm ~8^{circ }$ </tex-math></inline-formula> and <inline-formula> <tex-math>$pm ~0.6$ </tex-math></inline-formula> dB, respectively. Within 1.74–2.3 GHz (27.7%), the input RL, output RL, root mean squares (rms) phase error and rms amplitude error of the proposed active VSPS are better than 11 dB, 10.5 dB, 6.1°, and 0.99 dB, respectively. The average gain at the center frequency and the circuit size are 7 dB and <inline-formula> <tex-math>$0.29lambda _{g}^{2}$ </tex-math></inline-formula>, respectively. The experimental results demonstrate the feasibility of the design method in this article for compact broadband PDs, high-performance I/Q generators, and active VSPS.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"984-994"},"PeriodicalIF":4.5,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1109/TMTT.2025.3619969
Tongtong Xie;Mengyuan Wu;Wenzhao Liu;Shiwei Liu;Hao Chen;Hongyan Fu
A phase sensitivity-enhanced demodulation system for optical fiber interferometers based on a multi passband microwave photonic (MWP) filter is proposed and experimentally demonstrated, which effectively breaks the trade-off between detection frequency and phase sensitivity, enabling the simultaneous realization of high sensitivity and low-frequency detection. In the experimental setup, an optical fiber Fabry–Pérot interferometer (FPI) served as the sensing head, and an additional optical fiber FPI was introduced as a reference. The interference between the two FPIs generated both independent passbands and cross-interference passbands of the MPF, the latter enabling frequency down-conversion. The passband associated with the sensing FPI, initially centered at 1.752 GHz, was translated to 0.537 GHz via the interference between the sensing and reference FPIs, effectively mapping the phase modulation to a lower frequency. Consequently, a 3.26-fold enhancement in the detected phase shift was achieved at 0.537 GHz. Moreover, simultaneous phase demodulation from multiple passbands (e.g., 1.752 and 2.202 GHz), down-converted to 1.032 and 0.545 GHz, respectively, was successfully realized without spectral interference, demonstrating the scalability of the scheme. This system significantly enhances the detection performance of optical fiber interferometers simply and cost-effectively, offering a novel and scalable strategy for the design of high-resolution fiber interferometric sensing systems.
{"title":"Sensitivity-Enhanced Optical Fiber Interferometric Phase Demodulation Based on Multipassband Microwave Photonic Filter With Frequency Down-Conversion","authors":"Tongtong Xie;Mengyuan Wu;Wenzhao Liu;Shiwei Liu;Hao Chen;Hongyan Fu","doi":"10.1109/TMTT.2025.3619969","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3619969","url":null,"abstract":"A phase sensitivity-enhanced demodulation system for optical fiber interferometers based on a multi passband microwave photonic (MWP) filter is proposed and experimentally demonstrated, which effectively breaks the trade-off between detection frequency and phase sensitivity, enabling the simultaneous realization of high sensitivity and low-frequency detection. In the experimental setup, an optical fiber Fabry–Pérot interferometer (FPI) served as the sensing head, and an additional optical fiber FPI was introduced as a reference. The interference between the two FPIs generated both independent passbands and cross-interference passbands of the MPF, the latter enabling frequency down-conversion. The passband associated with the sensing FPI, initially centered at 1.752 GHz, was translated to 0.537 GHz via the interference between the sensing and reference FPIs, effectively mapping the phase modulation to a lower frequency. Consequently, a 3.26-fold enhancement in the detected phase shift was achieved at 0.537 GHz. Moreover, simultaneous phase demodulation from multiple passbands (e.g., 1.752 and 2.202 GHz), down-converted to 1.032 and 0.545 GHz, respectively, was successfully realized without spectral interference, demonstrating the scalability of the scheme. This system significantly enhances the detection performance of optical fiber interferometers simply and cost-effectively, offering a novel and scalable strategy for the design of high-resolution fiber interferometric sensing systems.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"950-959"},"PeriodicalIF":4.5,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1109/TMTT.2025.3618964
Kai Xu;Xiaoyang Liu;Ziheng Zhang;Mengfan Cheng;Qi Yang;Ming Tang;Deming Liu;Lei Deng
The integration of wideband electronic attack (EA) and electronic protection (EP) is a growing concern in electronic countermeasures (ECMs) as wireless technology advances. However, electronic hardware in conventional ECMs already approaches its bandwidth ceiling, making the solutions for high-performance, scalable, and reconfigurable optical signal processing extremely imperative, such as photonic RF memory (PRFM). This work demonstrates a phase–amplitude evolution mechanism in PRFM, where phase evolution enables radar range deception and amplitude evolution serves to scramble and diffuse the optical quantum noise for enhanced communication security. Founded on this, a novel microwave photonic front-end using orthogonal polarizations was developed and experimentally executed. In EA tasks, a 12-GHz optical frequency comb (OFC) signal was cyclically stored for $1000~mu $ s with high fidelity, creating 400 range false targets. Thanks to the Doppler frequency replication based on coherent OFC technology, the number of range–velocity compound 2-D false targets increased to 4400 ($400times 11$ ). In EP tasks, a 4-Gbaud QPSK signal was initially encrypted into a $2^{16}$ -QAM/quantum noise stream cipher (QNSC) signal and underwent 200 security adjustments in the loop at an 8% error vector magnitude (EVM) penalty, resulting in a nearly fourfold privacy improvement. Tuning of the number of circulations can compatibly reconstruct the jamming and security levels. Furthermore, an SNR monitoring probe was involved in the case of radar intrusion into communications, prompting communication tasks to adaptively respond to the threats. Therefore, our scheme pioneers the first integration of signal storage, 2-D radar jamming, private communication, security reconfiguration, and adaptive risk response in a wideband microwave photonic front-end, strongly addressing the reinforcement need of future ECMs.
{"title":"An Electronic Attack-Protection Integrated Front-End Enabled by Reconfigurable Photonic RF Memory","authors":"Kai Xu;Xiaoyang Liu;Ziheng Zhang;Mengfan Cheng;Qi Yang;Ming Tang;Deming Liu;Lei Deng","doi":"10.1109/TMTT.2025.3618964","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3618964","url":null,"abstract":"The integration of wideband electronic attack (EA) and electronic protection (EP) is a growing concern in electronic countermeasures (ECMs) as wireless technology advances. However, electronic hardware in conventional ECMs already approaches its bandwidth ceiling, making the solutions for high-performance, scalable, and reconfigurable optical signal processing extremely imperative, such as photonic RF memory (PRFM). This work demonstrates a phase–amplitude evolution mechanism in PRFM, where phase evolution enables radar range deception and amplitude evolution serves to scramble and diffuse the optical quantum noise for enhanced communication security. Founded on this, a novel microwave photonic front-end using orthogonal polarizations was developed and experimentally executed. In EA tasks, a 12-GHz optical frequency comb (OFC) signal was cyclically stored for <inline-formula> <tex-math>$1000~mu $ </tex-math></inline-formula>s with high fidelity, creating 400 range false targets. Thanks to the Doppler frequency replication based on coherent OFC technology, the number of range–velocity compound 2-D false targets increased to 4400 (<inline-formula> <tex-math>$400times 11$ </tex-math></inline-formula>). In EP tasks, a 4-Gbaud QPSK signal was initially encrypted into a <inline-formula> <tex-math>$2^{16}$ </tex-math></inline-formula>-QAM/quantum noise stream cipher (QNSC) signal and underwent 200 security adjustments in the loop at an 8% error vector magnitude (EVM) penalty, resulting in a nearly fourfold privacy improvement. Tuning of the number of circulations can compatibly reconstruct the jamming and security levels. Furthermore, an SNR monitoring probe was involved in the case of radar intrusion into communications, prompting communication tasks to adaptively respond to the threats. Therefore, our scheme pioneers the first integration of signal storage, 2-D radar jamming, private communication, security reconfiguration, and adaptive risk response in a wideband microwave photonic front-end, strongly addressing the reinforcement need of future ECMs.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"939-949"},"PeriodicalIF":4.5,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work proposes the use of machine learning-based techniques for enhanced testability and performance calibration of an industrial 79-GHz power amplifier (PA) designed for an automotive radar system. The proposed techniques are based on a set of built-in test structures including nonintrusive process monitors based on digital ring oscillators and a built-in reflectometer. The indirect signatures provided by these test structures allow us to do the following: 1) identify defective instances of the PA under test; 2) evaluate the quality of the output matching adaptation; and 3) calibrate the performance of the PA to compensate for process variations. Defect detection is based on a defect filtering algorithm that employs outlier identification techniques; mismatch evaluation employs a machine learning regressor; and, finally, the proposed performance calibration is based on a one-shot statistical calibration that predicts the optimum configuration of the PA. The proposed techniques are experimentally demonstrated on a set of 32 fabricated chips designed in 28 nm CMOS technology.
{"title":"Machine Learning-Based Defect Detection, Output Matching Assessment, and Performance Recentering of a 79-GHz Four-Way CMOS Power Amplifier","authors":"Oumayma Belkhadra;Florent Cilici;Sebastien Crampon;Jérémie Arbouet;Loïc Vincent;Gilles Montoriol;Salvador Mir;Emmanuel Pistono;Sylvain Bourdel;Manuel J. Barragan","doi":"10.1109/TMTT.2025.3619021","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3619021","url":null,"abstract":"This work proposes the use of machine learning-based techniques for enhanced testability and performance calibration of an industrial 79-GHz power amplifier (PA) designed for an automotive radar system. The proposed techniques are based on a set of built-in test structures including nonintrusive process monitors based on digital ring oscillators and a built-in reflectometer. The indirect signatures provided by these test structures allow us to do the following: 1) identify defective instances of the PA under test; 2) evaluate the quality of the output matching adaptation; and 3) calibrate the performance of the PA to compensate for process variations. Defect detection is based on a defect filtering algorithm that employs outlier identification techniques; mismatch evaluation employs a machine learning regressor; and, finally, the proposed performance calibration is based on a one-shot statistical calibration that predicts the optimum configuration of the PA. The proposed techniques are experimentally demonstrated on a set of 32 fabricated chips designed in 28 nm CMOS technology.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"1005-1022"},"PeriodicalIF":4.5,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Device-free radar sensing (DFRS) finds various applications due to the prevalence of sensors and touchless interaction. Existing deep learning-based DFRS methods require substantial labeled data to train a model. However, since labeling the process time-consuming and labor-intensive and increasing concerns about data privacy, it is necessary to develop a DFRS method without accessing the radar source data. To this end, we propose a novel cross-modal DFRS (CM-DFRS) method that uses existing pretrained models on open-source image datasets instead of training a model with source data to effectively recognize gestures obtained via radar signals. During the feature learning phase, to improve the information features and alleviate overfitting, we devise an information enhancement module (IEM) and introduce transductive learning to learn the query set from radar Doppler images. During inference, our model combines information maximization (IM) and distance-based perception strategy (DPS), making it possible to seamlessly transfer knowledge from natural image datasets to radar Doppler image datasets. We conducted a comprehensive evaluation of the CM-DFRS model and showed that our approach not only outperforms existing methods in terms of accuracy and robustness but also eliminates the need for extensive training data collection.
{"title":"Cross-Modal Device-Free Radar Sensing With Information Maximization Enhancement and Few-Shot Learning","authors":"Chao Fang;Yong Wang;Mu Zhou;Bingcai Chen;Jiacheng Wang;Bao Peng","doi":"10.1109/TMTT.2025.3620482","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3620482","url":null,"abstract":"Device-free radar sensing (DFRS) finds various applications due to the prevalence of sensors and touchless interaction. Existing deep learning-based DFRS methods require substantial labeled data to train a model. However, since labeling the process time-consuming and labor-intensive and increasing concerns about data privacy, it is necessary to develop a DFRS method without accessing the radar source data. To this end, we propose a novel cross-modal DFRS (CM-DFRS) method that uses existing pretrained models on open-source image datasets instead of training a model with source data to effectively recognize gestures obtained via radar signals. During the feature learning phase, to improve the information features and alleviate overfitting, we devise an information enhancement module (IEM) and introduce transductive learning to learn the query set from radar Doppler images. During inference, our model combines information maximization (IM) and distance-based perception strategy (DPS), making it possible to seamlessly transfer knowledge from natural image datasets to radar Doppler image datasets. We conducted a comprehensive evaluation of the CM-DFRS model and showed that our approach not only outperforms existing methods in terms of accuracy and robustness but also eliminates the need for extensive training data collection.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"1023-1036"},"PeriodicalIF":4.5,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-15DOI: 10.1109/TMTT.2025.3617506
Robert C. Crew;Eugene N. Ivanov;Graeme Flower;Michael E. Tobar;Maxim Goryachev
We report a novel X-band loop oscillator, whose resonator is formed from two optimally tuned commercial yttrium iron garnet (YIG) filters. We call this a $Lambda $ -resonator, owing to the characteristic $Lambda $ -shape of its amplitude transfer function (ATF). At offset frequencies greater than 70 Hz, oscillator phase noise is limited by the contribution from the amplifier, as described by Leeson’s model. The effective Q-factor of the $Lambda $ -resonator (2.6 × 103) is determined by the slope of its phase transfer function on resonance, which is directly proportional to the group delay of the filters. With off-the-shelf components, we achieve single-sideband (SSB) phase noise of −151 dBc/Hz at 1 MHz offset for an oscillation frequency of 9.2 GHz. This work points to the potential for improvements with custom built filters optimized for high group delay. The high selectivity of the $Lambda $ -resonator (made of two seventh-order YIG-filters) allowed a strong suppression of both phase and amplitude fluctuations of the transmitted signal at Fourier frequencies outside the resonator’s bandwidth. We also investigated relevant oscillator noise sources, including power-to-frequency conversion as a function of Fourier frequency, and use a novel, highly sensitive technique to characterize the noise.
{"title":"Microwave Oscillator Based on Two Optimally Tuned YIG Filters","authors":"Robert C. Crew;Eugene N. Ivanov;Graeme Flower;Michael E. Tobar;Maxim Goryachev","doi":"10.1109/TMTT.2025.3617506","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3617506","url":null,"abstract":"We report a novel X-band loop oscillator, whose resonator is formed from two optimally tuned commercial yttrium iron garnet (YIG) filters. We call this a <inline-formula> <tex-math>$Lambda $ </tex-math></inline-formula>-resonator, owing to the characteristic <inline-formula> <tex-math>$Lambda $ </tex-math></inline-formula>-shape of its amplitude transfer function (ATF). At offset frequencies greater than 70 Hz, oscillator phase noise is limited by the contribution from the amplifier, as described by Leeson’s model. The effective Q-factor of the <inline-formula> <tex-math>$Lambda $ </tex-math></inline-formula>-resonator (2.6 × 10<sup>3</sup>) is determined by the slope of its phase transfer function on resonance, which is directly proportional to the group delay of the filters. With off-the-shelf components, we achieve single-sideband (SSB) phase noise of −151 dBc/Hz at 1 MHz offset for an oscillation frequency of 9.2 GHz. This work points to the potential for improvements with custom built filters optimized for high group delay. The high selectivity of the <inline-formula> <tex-math>$Lambda $ </tex-math></inline-formula>-resonator (made of two seventh-order YIG-filters) allowed a strong suppression of both phase and amplitude fluctuations of the transmitted signal at Fourier frequencies outside the resonator’s bandwidth. We also investigated relevant oscillator noise sources, including power-to-frequency conversion as a function of Fourier frequency, and use a novel, highly sensitive technique to characterize the noise.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"73 12","pages":"10897-10903"},"PeriodicalIF":4.5,"publicationDate":"2025-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145778171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A photonic-aided wide-band high-precision spectrum analysis system is proposed and demonstrated. The polarization multiplexing is employed to perform concurrent operation of fast frequency-to-time mapping (FTTM)-based frequency measurement (FM) and neural network-assisted signal analysis. Dual-band FTTM is implemented via chirp multiplexing and matched filtering, which enables simultaneous FM covering two 6-GHz bands. A two-step filtering architecture is designed to mitigate the impact of laser frequency drift and achieve a measurement accuracy of ±2.6 MHz with 30 kHz spectral resolution. By utilizing a YOLOv8-based network, high-precision multiparameter estimation to the signal under test (SUT) is realized with a frequency error under 0.9 MHz, a bandwidth error under 2.8 MHz, a time-center error under $1~mu $ s, a duration error under $2.1~mu $ s, and a modulation recognition error rate under 0.025. The proposed system combines the advantages of photonic and electrical technologies, which holds great promise for applications in intelligent RF systems for cognitive radio and spectrum management.
{"title":"Photonic-Aided Wide-Band High Precision Spectrum Analysis System Based on Polarization Multiplexing","authors":"Yixiao Zhou;Xuan Li;Xikang Wang;Ruiqiong Wang;Guodong Wang;Qin Tian;Jialin Ma;Yongjun Li;Zihang Zhu;Shanghong Zhao","doi":"10.1109/TMTT.2025.3615200","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3615200","url":null,"abstract":"A photonic-aided wide-band high-precision spectrum analysis system is proposed and demonstrated. The polarization multiplexing is employed to perform concurrent operation of fast frequency-to-time mapping (FTTM)-based frequency measurement (FM) and neural network-assisted signal analysis. Dual-band FTTM is implemented via chirp multiplexing and matched filtering, which enables simultaneous FM covering two 6-GHz bands. A two-step filtering architecture is designed to mitigate the impact of laser frequency drift and achieve a measurement accuracy of ±2.6 MHz with 30 kHz spectral resolution. By utilizing a YOLOv8-based network, high-precision multiparameter estimation to the signal under test (SUT) is realized with a frequency error under 0.9 MHz, a bandwidth error under 2.8 MHz, a time-center error under <inline-formula> <tex-math>$1~mu $ </tex-math></inline-formula>s, a duration error under <inline-formula> <tex-math>$2.1~mu $ </tex-math></inline-formula>s, and a modulation recognition error rate under 0.025. The proposed system combines the advantages of photonic and electrical technologies, which holds great promise for applications in intelligent RF systems for cognitive radio and spectrum management.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"905-919"},"PeriodicalIF":4.5,"publicationDate":"2025-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article proposes a multibeam-assisted active cross-polarization (X-Pol) suppression technique that leverages auxiliary beams to effectively mitigate X-Pol leakages, thereby supporting polarization-division multiplexing (PDM). Amplitude and phase relationships for optimal cancellation are established, and performance limitations under practical residual array-level errors are quantified through theoretical analysis. To validate the technique, a compact Ka-band 64-element receive (RX) phased array with four fully connected beams is designed and fabricated using an 18-layer printed circuit board (PCB). It integrates 16 eight-channel four-beam beamformers (BFs), a dual-polarized (DP) slot-fed patch antenna array, and four sets of high-isolation 16:1 Wilkinson combining networks. The phased array demonstrates four independently steerable beams with 41.8-dB interbeam isolation at 29.5 GHz. It achieves scanning coverage up to ±50° in both planes with reconfiguration capability between circular [left-handed circular polarization (LHCP)/right-handed circular polarization (RHCP)] and linear (H/V) polarization (Pol) states. The measured gain-to-noise-temperature ratio (G/T) exceeds $mathbf {-7}$ dB/K across all scan angles at 29.5 GHz. Measurement results show that the proposed technique effectively enhances steerable X-Pol discrimination from $mathbf {sim }20$ to $mathbf {gt }40$ dB at the target frequency within a wide bandwidth across the scanning range and significantly improves the error vector magnitude (EVM) under strong interference. To the authors’ best knowledge, this work presents the first Ka-band phased array supporting four concurrent beams with Pol reconfigurability, advancing high-capacity concurrent co-site communication systems with robust interference resilience.
{"title":"Multibeam-Assisted Cross-Polarization Suppression With Ka-Band 64-Element Four-Beam Reconfigurable Phased Array Implementation","authors":"Zixian Ma;Xinhong Xie;Nayu Li;Bing Lan;Haotian Chen;Xiaokang Qi;Chunyi Song;Zhiwei Xu","doi":"10.1109/TMTT.2025.3612979","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3612979","url":null,"abstract":"This article proposes a multibeam-assisted active cross-polarization (X-Pol) suppression technique that leverages auxiliary beams to effectively mitigate X-Pol leakages, thereby supporting polarization-division multiplexing (PDM). Amplitude and phase relationships for optimal cancellation are established, and performance limitations under practical residual array-level errors are quantified through theoretical analysis. To validate the technique, a compact Ka-band 64-element receive (RX) phased array with four fully connected beams is designed and fabricated using an 18-layer printed circuit board (PCB). It integrates 16 eight-channel four-beam beamformers (BFs), a dual-polarized (DP) slot-fed patch antenna array, and four sets of high-isolation 16:1 Wilkinson combining networks. The phased array demonstrates four independently steerable beams with 41.8-dB interbeam isolation at 29.5 GHz. It achieves scanning coverage up to ±50° in both planes with reconfiguration capability between circular [left-handed circular polarization (LHCP)/right-handed circular polarization (RHCP)] and linear (H/V) polarization (Pol) states. The measured gain-to-noise-temperature ratio (G/T) exceeds <inline-formula> <tex-math>$mathbf {-7}$ </tex-math></inline-formula> dB/K across all scan angles at 29.5 GHz. Measurement results show that the proposed technique effectively enhances steerable X-Pol discrimination from <inline-formula> <tex-math>$mathbf {sim }20$ </tex-math></inline-formula> to <inline-formula> <tex-math>$mathbf {gt }40$ </tex-math></inline-formula> dB at the target frequency within a wide bandwidth across the scanning range and significantly improves the error vector magnitude (EVM) under strong interference. To the authors’ best knowledge, this work presents the first Ka-band phased array supporting four concurrent beams with Pol reconfigurability, advancing high-capacity concurrent co-site communication systems with robust interference resilience.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"73 12","pages":"10814-10826"},"PeriodicalIF":4.5,"publicationDate":"2025-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145778120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-09DOI: 10.1109/TMTT.2025.3615455
Nerea Otegi;Juan-Mari Collantes
The above article presents an interesting method for extracting noise parameters using highly reflective loads, such as those available in a vector network analyzer (VNA) calibration kit. While the approach addresses a well-known singularity issue, the above article does not explicitly acknowledge that this issue had already been resolved in earlier classical formulations—some of which are, in fact, cited in the article itself. Combined with the absence of other relevant References, this may give the reader the impression that the technique is entirely novel. This comment aims to clarify the context of the contribution and highlight earlier developments with similar approaches. It does not question the validity of the results but suggests that better acknowledgment of previous work would help readers more accurately assess the scope and originality of the article.
{"title":"Comments on “Measuring Noise Parameters Using an Open, Short, Load, and λ/8-Length Cable as Source Impedances”","authors":"Nerea Otegi;Juan-Mari Collantes","doi":"10.1109/TMTT.2025.3615455","DOIUrl":"https://doi.org/10.1109/TMTT.2025.3615455","url":null,"abstract":"The above article presents an interesting method for extracting noise parameters using highly reflective loads, such as those available in a vector network analyzer (VNA) calibration kit. While the approach addresses a well-known singularity issue, the above article does not explicitly acknowledge that this issue had already been resolved in earlier classical formulations—some of which are, in fact, cited in the article itself. Combined with the absence of other relevant References, this may give the reader the impression that the technique is entirely novel. This comment aims to clarify the context of the contribution and highlight earlier developments with similar approaches. It does not question the validity of the results but suggests that better acknowledgment of previous work would help readers more accurately assess the scope and originality of the article.","PeriodicalId":13272,"journal":{"name":"IEEE Transactions on Microwave Theory and Techniques","volume":"74 1","pages":"1167-1168"},"PeriodicalIF":4.5,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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