We report a photonic-assisted method for measuring the frequencies of a multi-tone microwave with high accuracy based on pulse identification. The unknown microwave signal and a linearly chirped signal are modulated to an optical carrier using a dual-polarization Mach–Zehnder modulator. Carrier-suppressed single-sideband modulation avoids the generation of undesired frequency components after photodetection. An electrical bandpass filter with a narrow bandwidth selects the beat signal between the unknown signal and the linearly chirped optical tone. A pulse, generated by the beat signal, can be observed using an oscilloscope (OSC). By identifying the beating pulse position, we can accurately determine the frequency of the unknown signal. The single-tone and multi-tone microwave signal ranges of 6–16 GHz and 26–36 GHz are successfully measured, respectively. The measurement errors for single-tone and multi-tone signals are both less than ±1 MHz.
We report a photonic-assisted method for measuring the frequencies of a multi-tone microwave with high accuracy based on pulse identification. The unknown microwave signal and a linearly chirped signal are modulated to an optical carrier using a dual-polarization Mach–Zehnder modulator. Carrier-suppressed single-sideband modulation avoids the generation of undesired frequency components after photodetection. An electrical bandpass filter with a narrow bandwidth selects the beat signal between the unknown signal and the linearly chirped optical tone. A pulse, generated by the beat signal, can be observed using an oscilloscope (OSC). By identifying the beating pulse position, we can accurately determine the frequency of the unknown signal. The single-tone and multi-tone microwave signal ranges of 6–16 GHz and 26–36 GHz are successfully measured, respectively. The measurement errors for single-tone and multi-tone signals are both less than ±1 MHz.
A novel photonic approach to simultaneously implement frequency measurement and signal separation is proposed and experimentally demonstrated for pulsed and continuous-wave (CW) microwave signals. In this approach, a light wave is externally modulated with carrier suppressed by a pulsed or CW microwave signal to be measured, and then sent to two optical complementary filters to perform frequency-to-amplitude mapping. The outputs of the two filters are detected by low-speed photodetectors, low-frequency alternating currency (AC) electronic component and direct current (DC) one being generated. The carrier frequency of the pulsed microwave signal can be estimated by monitoring the power of the AC component, while the frequency of the CW microwave signal is discriminated from the power of the DC component, with the frequency measurement and the signal separation simultaneously realized. In proof-of-concept experiments, within the frequency range from 5 to 20 GHz, measurement errors less than ±0.1, ±0.11 , or ±0.13 GHz are achieved for a pulsed signal with pulse repetition frequency of 0.25, 0.5, or 1 MHz, whereas the errors less than ±0.08 GHz are derived for a CW signal.
A filterless microwave photonic-assisted frequency measurement scheme for instant broadband RF signal measurement is proposed and analyzed. The scheme employs single-channel mapping to save signal processing time. The channelized receiver is divided into upper and lower branches, generating a non-flat optical frequency comb and achieving single-sideband modulation, respectively. Through image-rejection mixing, the powers of the beating frequencies and the optical frequency comb lines are combined to determine the signal range, and the signal frequency can be accurately calculated. Simulations demonstrate that this scheme can measure multi-frequency and linearly frequency-modulated signals within the range of 0-40 GHz. The system has been experimentally validated with a measurement error of less than 25 MHz.
Abstract A high-accuracy photonics-assisted frequency measurement with rough-accurate compensation based on Mach-Zehnder interfering and power cancellation is proposed. A polarization division multiplexing dual-parallel Mach–Zehnder modulator (PDM-DPMZM) is employed to mix the unknown RF signal and sweep signal to optical field. The rough measurement is firstly performed by the interference of a Mach-Zehnder interferometer (MZI) to realize fast frequency estimation. Then, based on the rough measurement result, the accurate measurement based on power cancellation is implemented in a much narrower range, which greatly improves the efficiency of frequency measurement. The simulation results show that the amplitude comparison function (ACF) established by interference can achieve a measurement error of less than 0.3 GHz over 0.5 ~39 GHz. Moreover, thanks to the rough-accurate compensation, the accuracy can be further improved to 4 MHz. Additionally, the multiple frequency identification with a resolution of 10 MHz can also be achieved based on this system.
A cross-referenced and deadband-free method with photonic harmonic down-conversion is proposed for microwave frequency measurement based on cascaded-four-wave-mixing (CFWM) in semiconductor optical amplifiers. The proposed method enables ultra-wide and accurate frequency measurement with low-frequency spectrum detection, and at the same time achieves deadband-free and multi-tone frequency measurement by cross-referenced frequency discrimination. For a proof of concept, microwave signal measurement is experimentally demonstrated up to the 40 GHz frequency range with an 0.2-MHz measurement error. The frequency measurement features ease of configuration by only changing the low-frequency electrical local oscillators of the CFWM-based photonic harmonic down-converter.
A novel frequency measurement is proposed based on frequency-to-carrier phase-shifted mapping and finite extinction ratio. Due to the frequency dependence of the dispersion phase shift, carrier phase-shifted double-sideband modulation and dispersive effect are combined for effective mapping. Additionally, the finite extinction ratio is introduced to mitigate the influence of unideal parameters on measurement error. To achieve this, a dual-parallel Mach-Zehnder modulator and a dispersion compensating fibre are combined, and a power minimization problem is formulated to establish a mapping table. Theoretical analysis and simulation results show the frequency measurement range over 30 GHz with errors below 180 MHz. Furthermore, the measurement error is reduced below 40 MHz after considering the finite extinction ratio.
Abstract Driven by the growing demands in wireless communication, remote sensing and emerging 6G networks, research on microwave signal measurement techniques has attached intensive attention. Unlike conventional electronic‐based approaches, photonics chip‐based microwave signal measurement systems offer significant advantages, including broad operation bandwidth, reduced weight, and enhanced resistance to unwanted electromagnetic interference. Despite notable progress in integrated microwave photonic measurement systems, the majority remains constrained by bandwidth below 30 GHz, primarily due to the limitation of modulators. Furthermore, most previous studies focus on the measurement of one single parameter, typically the frequency, limiting their applications in more complex, real‐world situations. Here, an on‐chip photonic microwave multi‐parameter measurement system is presented on the thin‐film lithium niobate (TFLN) platform. The system enables measurement of microwave frequency, phase, and amplitude, offering an ultra‐high bandwidth (up to 60 GHz) with low root‐mean‐squared errors: 450 MHz for frequency, 3.43° for phase, and 1.64% for amplitude. Additionally, the system is validated by the time‐domain reconstruction of unknown sinusoidal microwave signals based on measurement results. This demonstration further broadens the scope of integrated TFLN photonic devices for microwave signal measurement, providing a viable solution to the bandwidth limitations of existing microwave networks and addressing the increasing demands of future information‐driven technologies.