Tunable Multiband Microwave Photonic Filters

A survey on photonics technologies for radar applications

Photonics is a fast and galloping technology related to both microwave and optics science. Photonics is a very vast and distinctive field in recent days. Due to the enlarged difficulty of the electronics component for large bandwidth, we had to rely on the delightful photonics system. Photonics-based system came to us as a blessing in science research in this era. Software-defined photonics-based radar must be the near forthcoming next-generation necessities. This paper has a detailed study of photonics radar and how its components work. A comparative study has been presented with the traditional electronics microwave radar systems and photonics radar systems. The slow evolution of optics system and how the application has been pushed to radar, microwave and antenna systems have been described here. In this survey repost starting from the historical storyline and basics of photonics radar, the concept of radar based on photonics system and its need, then the digitized PhoDIR system invention, radio frequency signal generation and modulation, beamforming over antenna array and signal transportation, we have discussed the important architecture of photonics radar, phase control process, sampling process, transceiver modules till the radar parameter measurements and various applications of photonics radar including quantum radar. Photonics radar seemed to be a very intense and bright research study area; many practical problems and its wonderful solution have been described here. In this paper, the advancement and progression of photonics-based radar communication system accomplishments of the last decades has been shown and also discussions about future study and development of photonics radar have been presented.

Adaptive photonic RF spectral shaper

The radio frequency spectral shaper is an essential component in emerging multi-service mobile communications, multiband satellite and radar systems, and future 5G/6G radio frequency systems for equalizing spectral unevenness, removing out-of-band noise and interference, and manipulating multi-band signal simultaneously. While it is easy to achieve simple spectral functions using either conventional microwave photonic filters or the optical spectrum to microwave spectra mapping techniques, it is challenging to enable complex spectral shaping functions over tens of GHz bandwidth as well as to achieve point-by-point shaping capability to fulfill the needs in dynamic wireless communications. In this paper, we proposed and demonstrated a novel spectral shaping system, which utilizes a two-section algorithm to automatically decompose the target RF response into a series of Gaussian functions and to reconstruct the desired RF response by microwave photonic techniques. The devised spectral shaping system is capable of manipulating the spectral function in various bands (S, C, and X) simultaneously with step resolution of as fine as tens of MHz. The resolution limitation in optical spectral processing is mitigated using the discrete convolution technique. Over 10 dynamic and independently adjustable spectral control points are experimentally achieved based on the proposed spectral shaper.

Discretely programmable microwave photonic filter based on temporal Talbot effects

We propose and experimentally demonstrate a reconfigurable microwave photonic filter based on temporal Talbot effects. The microwave signal is first uniformly sampled by a train of optical pulses through electro-optic intensity modulation. The sampled optical pulses are then directed to a Talbot-based optical signal processor, consisting of an electro-optic temporal phase modulator and a chromatic dispersion line. The Talbot-based microwave photonic filter (TMPF) exploits the inherent properties of the Talbot self-imaging effect for mitigating pulse-to-pulse intensity fluctuations of optical pulses to transmit some fluctuation frequencies and mitigate or entirely block other microwave spectral components. The output microwave signal is finally reconstructed from the processed optical pulses and the resultant RF response is measured by a network analyzer. The TMPF exhibits an RF response with periodic, symmetric-profile passbands whose center frequency and free spectral range (FSR) are defined by the sampling rate and the dispersion value. The filter passbands can be reconfigured electrically, in discrete steps, by adjusting the modulation function of the phase modulator, i.e., without the need for manual adjustment of the optical components. This enables the capability of selection of specific passbands among the primary passbands. The phase modulation function is provided using an arbitrary waveform generator, with the potential for fast tuning of the filter's spectral response. The bandwidth of the filter passband can also be easily customized by adjusting the sampling pulse's temporal width using an optical bandpass filter. Examples of filter performance in various passband configurations are also presented in the time domain to further validate the operation of the filter.

Microwave photonic multiband filter with independently tunable passband spectral properties

Multiband RF filters with independently controllable passbands are an essential component in dynamic multiband RF communications. Unfortunately, even a fixed multiband RF filter without the capability to adjust the passband properties individually is very difficult to achieve using either RF electronics or microwave photonic technologies. In microwave photonic approaches, the critical limitation is the close relationship between passbands-the tuning of one passband leads to a change in another, hindering the ability to independently control each passband. In this Letter, a programmable microwave photonic multiband filter with full control of amplitude, frequency, bandwidth, group delay slope, and the spectral shape of each passband has been experimentally demonstrated. A multiband filter design algorithm has also been developed that considers each RF passband as an individual, then uses inverse Fourier transform and filter design rule to determine the corresponding optical parameters and combines a series of shaped cosine functions to achieve the desired RF properties.