Photonic-assisted Microwave Frequency Research Articles

Photonic-assisted wideband microwave frequency measurement based on optical heterodyne detection

A photonic-assisted microwave frequency measurement (MFM) method based on optical heterodyne detection is proposed and experimentally demonstrated. In the proposed MFM system, a linearly chirped optical waveform (LCOW) from a three-electrode distributed Bragg reflector laser diode (DBR-LD) and a multi-wavelength signal from a Mach-Zehnder modulator (MZM), where the signal under test (SUT) is modulated on an optical carrier from a distributed feedback laser diode (DFB-LD), are heterodyne detected by the photodetector (PD). A bandpass filter then filters the detected signal, and the envelope is detected by an oscilloscope. Then, frequency-to-time mapping is realized, and the signal frequency is measured. Thanks to the fast tuning rate and large tuning range of the DBR-LD, the proposed MFM system has a high measurement speed and a broad instantaneous measurement bandwidth. In the experimental demonstration, a measurement error below 39.1 MHz is achieved at an instantaneous bandwidth of 20 GHz and a measurement speed of 1.12 GHz/µs. The MFM of a frequency-hopping signal is also experimentally demonstrated. The successful demonstration of the MFM system with a simple structure provides a new optical solution for realizing broadband and fast microwave frequency measurements.

High-resolution photonic-assisted microwave frequency identification based on an ultrahigh-Q hybrid optical filter

Photonic-assisted microwave frequency identification has been extensively studied in civil and defense applications due to its distinct features including wide frequency coverage, large instantaneous bandwidth, high frequency resolution, and immunity to electromagnetic interference. In this paper, we propose and experimentally demonstrate an approach for high-resolution frequency identification of wideband microwave signals by linearly mapping the microwave frequencies to the time delays of the optical pulses. In the proposed system, an ultrahigh-Q hybrid optical filter is a key component, which consists of a fiber ring resonator (FRR) and a silicon photonic racetrack micro-ring resonator (MRR). The FRR has an ultra-narrow bandwidth of 7.6 MHz and a small free spectral range (FSR) of 292.5 MHz, while the MRR has a bandwidth of 167.5 MHz and a large FSR of 73.8 GHz. By precisely matching the resonance wavelengths of the FRR and the MRR, a hybrid optical filter with an ultrahigh Q-factor and a large FSR is realized, which is much preferred to realizing a high resolution and a wide measurement range for microwave frequency identification. An experiment is performed and different types of microwave signals are identified. A frequency measurement range as broad as 33 GHz from 2 to 35 GHz, a frequency resolution as high as 15 MHz and a measurement accuracy as high as 5.6 MHz are experimentally demonstrated. The proposed frequency identification system holds great advantages including high frequency resolution, high measurement accuracy, and wide frequency coverage, which can find extensive applications in next-generation electronic warfare and cognitive radio systems.

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

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.

Photonic-Assisted Microwave Frequency Measurement With Adjustable Channel Bandwidth Based on Spectrum-Controlled Brillouin Phase Shift

A photonics-based channel bandwidth tunable microwave frequency measurement (MFM) is analyzed and verified, which is implemented based on the principle of the frequency-to-phase-slope mapping (FTPSM) in stimulated Brillouin scattering (SBS). The spectrum-controlled Brillouin phase shift curve is created by using an optical frequency comb (OFC) pump instead of a single pump. As a result, the Brillouin phase shift response is superimposed to further realize a flexible and adjustable measurement bandwidth. Meanwhile, thanks to the relationship between the OFC pump and the unknown signal, the frequency measurement can be achieved by the property of monotonous frequency-to-phase-slope mapping. A proof-of-concept experiment is performed to verify the feasibility of the approach. By changing the number of OFC lines, the channel bandwidths of 500, 700, or 900 MHz are demonstrated, with a measurement error lower than 35 MHz. We believe that this FTPSM-based MFM system is a promising solution for radio frequency (RF) channelized receiver.

Microwave frequency measurement with high accuracy and wide bandwidth based on whispering-gallery mode barcode.

We propose and experimentally demonstrate a novel method for photonic-assisted microwave frequency measurement based on whispering-gallery mode (WGM) barcode, which is a dense spectrum generated by a micro-resonator that supports a large number of optical modes. The measurement relies on the relation between the microwave frequency and its unique barcode. The proposed system has the advantages of wide bandwidth, high accuracy, and multiple-frequency measurement capability. Microwave frequency measurement from 1 to 20 GHz is experimentally demonstrated with a measurement error of 40 kHz. For multi-tone signals, the frequency resolution is demonstrated to be less than 20 MHz. A dynamic multi-tone microwave signal consists of a 16-20 GHz linear frequency-modulated (LFM) signal, and a 10 GHz signal is measured to show the capability of multiple-frequency measurement. The system stability is also evaluated, and a self-reference method is proposed to maintain a long-term high-accuracy measurement.

Photonic-Assisted Microwave Frequency and Phase Shifter for Deception Jamming

A new microwave photonic signal processing structure that has the ability to realise frequency and phase shifting operation is presented. The proposed structure uses Serrodyne phase modulation in a dual-polarisation binary phase shift keying (DP-BPSK) dual-drive Mach Zehnder modulator to shift the frequency of an input microwave signal. This has the advantage over the conventional frequency mixers that the unwanted frequency components adjacent to the frequency translated microwave signal can be largely suppressed. It is suitable for use in deception jamming in electronic countermeasures systems. The phase shifting operation is realised by controlling the bias voltages of the DP-BPSK modulator. The dual-function microwave photonic signal processor has a simple structure and a wide bandwidth. The structure enables commercial modulator bias controllers to be used to provide long-term stable performance. Experimental results are presented that demonstrate a wide operating frequency range of 3 to 16 GHz, an over 35 dB suppression on the spurious signals and 0° to 360° phase shift on the frequency translated microwave signal. Using bias controllers to maintain a large spurious suppression ratio of around 35 dB is also demonstrated.

Photonic-assisted microwave frequency measurement towards cognitive radio

Cognitive radio frequency (RF) systems can be seen through an OODA (observe, orient, decide and act) loop, and electronic warfare (EW) can be used in some of these stages, namely the observe and the act. Instantaneous microwave frequency measurement (IFM) systems can contribute to cognitive RF technology taking the real world to the data world. In an OODA loop, IFM can be arranged as in the observe stage. Here we have proposed an IFM device that allows the adjustment of the directional couplers coupling coefficients, optical fiber lengths, modulation index and modulation formats, which makes the system tunable. The analytical model result shows good agreement with the simulation, achieving frequency differences of 130 MHz and 210 MHz for the lowest and the highest amplitude comparison function values, respectively.

Photonic-Assisted Regenerative Microwave Frequency Divider With a Tunable Division Factor

A photonic-assisted microwave frequency divider that is able to perform frequency division with a tunable division factor is presented. It is realized based on the regenerative approach in which frequency mixing and filtering operations are implemented using a dual-parallel Mach–Zehnder modulator (DPMZM) and an optical filter in an optoelectronic oscillator loop. The frequency division factor can be tuned by controlling the optical filter passband, the round-trip gain, and the time delay of the optoelectronic oscillator loop. The proposed approach is analyzed theoretically and verified experimentally. The phase conditions to achieve frequency division for a given division factor are analyzed. Experimental results demonstrate, for the first time, a photonic-assisted regenerative microwave frequency divider with a tunable frequency division factor of 2 to 6. One key application of a microwave frequency divider is to improve the phase noise performance of a microwave signal. In our experiment, the phase noise is reduced by 16.2 dB when a microwave signal is frequency divided by 6 times.

Wideband adaptive microwave frequency identification using an integrated silicon photonic scanning filter

Photonic-assisted microwave frequency identification with distinct features, including wide frequency coverage and fast tunability, has been conceived as a key technique for applications such as cognitive radio and dynamic spectrum access. The implementations based on compact integrated photonic chips have exhibited distinct advantages in footprint miniaturization, light weight, and low power consumption, in stark contrast with discrete optical-fiber-based realization. However, reported chip-based instantaneous frequency measurements can only operate at a single-tone input, which stringently limits their practical applications that require wideband identification capability in modern RF and microwave applications. In this article, we demonstrate, for the first time, a wideband, adaptive microwave frequency identification solution based on a silicon photonic integrated chip, enabling the identification of different types of microwave signals from 1 to 30 GHz, including single-frequency, multiple-frequency, chirped-frequency, and frequency-hopping microwave signals, and even their combinations. The key component is a high Q-factor scanning filter based on a silicon microring resonator, which is used to implement frequency-to-time mapping. This demonstration opens the door to a monolithic silicon platform that makes possible a wideband, adaptive, and high-speed signal identification subsystem with a high resolution and a low size, weight, and power (SWaP) for mobile and avionic applications.

Photonic microwave frequency measurement with a tunable range based on a dual-polarization modulator.

This paper presents a novel photonic-assisted microwave frequency measurement scheme based on an integrated dual-polarization Mach-Zehnder modulator (DPol-MZM). The DPol-MZM is used to obtain a polarization multiplexing signal modulated by the microwave signal with the frequency to be identified. The obtained signal is split into two channels after propagating along a single mode fiber. The two divided parts are used to establish an amplitude comparison function (ACF) which provides frequency-power mapping. The proposed scheme is experimentally verified. The frequency responses of the two branches are nearly complementary; thus, a relatively steep ACF is obtained. A frequency measurement range from 2 to 28 GHz with an error of ±0.2 GHz is achieved. Moreover, the measurement range can be tuned by simply adjusting the polarization state of one channel. The proposed system is simple, and the measurement range can be easily adjusted.

Photonic-assisted microwave frequency measurement system based on a silicon ORR

A photonic-assisted instantaneous microwave frequency measurement (IFM) system is demonstrated with add-drop optical ring resonators (ORRs) on silicon-on-insulator (SOI) platform. By launching a double-sideband suppressed carrier modulated optical signal into the ring, a monotonous amplitude comparison function (ACF) irrespective of the amplitudes of both optical and RF signals is established to translate the RF frequency to the power ratio between the through and drop ports of the ring. Two experiments have been set up with two rings which have different Q values. Two 25µm radius ORRs with Q values of 3974 and 25833 are used to offer different measurement ranges and accuracies. In the experiments the ORR with low Q value has a large measurement range of 0.5–35GHz, and the other one with high Q value exhibits a high accuracy of 0.1GHz in the frequency range of 0.1–5GHz.

Photonic-assisted microwave frequency multiplier based on nonlinear polarization rotation

A photonic-assisted microwave frequency multiplier (MFM) based on the Kerr shutter is proposed and demonstrated. In this MFM, the nonlinear polarization rotation in the high nonlinear optical fiber is used for the first time to implement the light-controlled optical-carrier-suppressed modulation. The frequency-doubled microwave signal with the frequency up to 144GHz is generated. The results of the experiment are in accordance with the theoretical prediction.

Ultrahigh-Resolution Photonic-Assisted Microwave Frequency Identification Based on Temporal Channelization

Real-time ultrahigh-resolution microwave frequency identification is paramount for widespread applications, such as communications, radar, and electronic warfare. Photonics-assisted microwave frequency identification can be achieved using an optical channelizer. While this technique enables simultaneous measurement of multiple frequencies, it has poor measurement resolution due to the large channel spacing, which is usually greater than 1 GHz. Here, we introduce a new channelizer-based microwave frequency measurement technique that offers nearly 500 times higher spectral resolution. This method employs largely dispersed broadband optical pulses to encode the time-domain characteristics of the modulating signal to the optical spectral domain. An optical channelizer is employed to slice the spectrum, which is equivalent to performing temporal sampling of the time-domain waveform. The unknown microwave signal is then reconstructed and its spectral distribution is analyzed by a digital processor. To evaluate the proposed technique, frequency measurements of a single-tone, a multiple-tone, and a frequency-hopping microwave signal are demonstrated. A measurement resolution as high as 55 MHz is achieved using an optical channelizer with a channel spacing of 25 GHz.

Photonic-assisted microwave frequency multiplication with a tunable multiplication factor

Photonic-assisted microwave frequency multiplication with a tunable multiplication factor (MF) based on an optical comb generator and an embedded single-passband microwave photonic filter (MPF) is proposed and demonstrated. The optical comb is generated using two cascaded modulators which are driven by a microwave reference signal. By applying the optical comb to a photodetector, a fundamental frequency corresponding to the comb spacing and its harmonics is generated. Thanks to the embedded single-passband MPF, only one harmonic is selected by the single-passband MPF. Thus, a single-frequency frequency-multiplied microwave signal is generated. In the proposed system, the embedded single-passband MPF is formed by using a sliced broadband optical source and a section of dispersion-compensating fiber (DCF). By tuning the central frequency of the passband at a frequency corresponding to that of a specific harmonic, a microwave signal at that specific frequency is generated. The proposed system is experimentally demonstrated. A frequency-multiplied microwave signal with an MF from 1 to 5 is generated. The phase noise and frequency tunability of the generated microwave signal are also investigated.

A Simple Photonic-Assisted Microwave Frequency Measurement System Based on MZI With Tunable Measurement Range and High Resolution

A simple and practical photonic approach for microwave instantaneous frequency measurement has been proposed and experimentally demonstrated. The unknown microwave signal with its frequency to be measured is carrier-suppressed modulated on the lightwave by a Mach-Zehnder modulator biased at the minimum point. And thanks to the inherent complementary transmission responses of the Mach-Zehnder interferometer (MZI), the fixed relationship between the amplitude comparison function and microwave frequency to be measured is established. By monitoring and processing the optical powers of the two output ports of the MZI, the frequency of the microwave signal could be easily estimated. The proposed scheme is experimentally verified and has many advantages, such as simple structure, low cost, fast response, practical prospect, tunable measurement range, and high resolution.

Photonic-assisted microwave frequency measurement with higher resolution and tunable range

A photonic-assisted approach to microwave frequency measurement is proposed based on frequency-to-power mapping with the help of the so-called amplitude comparison function. The key component is a dual-output Mach-Zehnder modulator (MZM) working at chirped modulation. The proposed scheme is characterized as having simplicity, higher resolution, and tunable measurement range. Owing to experimental constraint, an equivalent experiment has been carried out using a common single-output MZM at different bias points to prove the concept.