Low Error and Broadband Microwave Frequency Measurement Using a Silicon Mach–Zehnder Interferometer Coupled Ring Array

Machine-Learning-Assisted Instantaneous Frequency Measurement Method Based on Thin-Film Lithium Niobate on an Insulator Phase Modulator for Radar Detection

“…In summary, this paper proposes a simple reconfigurable IFM system based on a low-voltage LNOI phase modulator for radar detection, which demonstrates high sensitivity, integrated miniaturization, and an adjustable measurement range and high measurement accuracy with the help of stacked integrated learning models compared with the high-performance discrete microwave photonic systems and the on-chip structures that have been reported. For instance, the IFM systems proposed in [ 11 , 27 ] are both capable of achieving reconfigurable measurement ranges and accuracies. However, the structure in [ 27 ] is based on a Sagnac loop, making it difficult to achieve on-chip integration, while the on-chip MZ interferometric structure [ 11 ] relies on the precise control of the thermal electrodes and is sensitive to the ambient temperature.…”

“…For instance, the IFM systems proposed in [ 11 , 27 ] are both capable of achieving reconfigurable measurement ranges and accuracies. However, the structure in [ 27 ] is based on a Sagnac loop, making it difficult to achieve on-chip integration, while the on-chip MZ interferometric structure [ 11 ] relies on the precise control of the thermal electrodes and is sensitive to the ambient temperature. The proposed work uses LNOI material, as well as exhibiting a suitable sensitivity and tunable measurement range accuracy, with no need to control the work point to adapt it to the needs of various application scenarios ( Table 1 ).…”

“…It has demonstrated extraordinary capabilities compared to traditional electronic measurement systems [ 4 , 5 ] in the areas of signal detection and early warning reception [ 6 , 7 , 8 ]. Over the past decade, new architectures for photonic-assisted instantaneous IFM systems have been proposed [ 9 , 10 , 11 ] and several common measurement theories have evolved, such as frequency–time mapping [ 12 , 13 ], frequency–space mapping [ 14 , 15 , 16 ], and frequency–power mapping [ 17 ]. In a different way, the core idea of these methods is to reflect unknown frequency information using physical quantities that a system can measure directly or indirectly.…”

“…However, the use of a Sagnac loop hinders the evolution of the system towards integration. To achieve a tunable measuring range and to improve system integration, a Mach–Zehnder interferometer (MZI) coupled ring array and a two-step measurement method [ 11 ] were introduced by Li Liu to establish a large bandwidth and high-precision frequency measurement. Thanks to the ultra-high peak rejection of the microwave photonic filter (MPF) response and flexibly tunable range, the system exhibits a measurement bandwidth of 40 GHz and a measurement accuracy of 9 MHz.…”