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Microwave photonic filters have been regarded as an alternative to traditional radio‐frequency filters because of their wide bandwidth and large tunability. Integrated microwave photonic filters can integrate all necessary components into a single chip and are highly demanded for future radio‐frequency applications. Here, a highly integrated frequency‐tunable microwave photonic bandpass filter based on a silicon platform is proposed and demonstrated. The integrated filter consists of a phase modulator, four cascaded microring resonators and a photodetector. The frequency‐tunable range of the integrated filter is from 6.1 to 35.9 GHz, and the reconfigurable bandwidth is from 0.22 to 0.54 GHz. A large spurious free dynamic range of 102.1 dB Hz2/3 is obtained. This highly integrated approach holds great promise for miniaturised, flexible, and high‐performance microwave signal processing in modern radar and communication systems. [ABSTRACT FROM AUTHOR]

Microwave photonic filter (MPF) is one of the key fundamental subsystems in microwave photonics, and it shows great potentiality in numbers of applications such as optoelectronic oscillator, microwave frequency measurement, and so forth. A narrowband bandpass MPF is highly desirable with its high selectivity in microwave photonic applications. However, a resonator with a high quality factor (>106) is very difficult to fabricate on the mature silicon photonics platform without optimization, thus restraining the applications of the MPF. In this paper, we propose and experimentally demonstrate a tunable sub-gigahertz bandwidth MPF based on an ultrahigh quality factor silicon microring resonator. Most performance aspects of the MPF are well-balanced. A full width at half-maximum bandwidth of 170 MHz is achieved thanks to the ultrahigh total quality factor as 1.14 × 106 of the microring resonator, and the average waveguide loss and the intrinsic Q factor of the microring resonator are calculated as 0.25 dB/cm and 2.67 × 106, respectively. The corresponding rejection ratio of the bandpass filter is 26.5 dB. Besides, the central frequency of the filter could be continuously tuned from 2.0 to 18.4 GHz with a microheater fabricated upon the microring, and a 16.4 GHz tuning range is achieved with the maximum power consumption of 14.4 mW. The device area is ∼0.05 mm2. [ABSTRACT FROM AUTHOR]

We propose and demonstrate an approach to generating large time-bandwidth product (TBWP) frequency-hopping (FH) microwave waveforms by using an ultra-high-quality factor (Q) silicon microring resonator (MRR) with thermal tuning. An ultra-high-Q MRR (Q ∼ 106) is used to filter out an expected frequency component from an optical frequency comb. Heterodyne beating between the filtered frequency and another seed frequency light detected by a photodetector will generate an FH microwave waveform. In addition, the FH microwave signal can be flexibly and independently tuned in terms of the central frequency, bandwidth, frequency order, and time sequence length, just altering the driving voltage on the MRR. The proof-of-concept experiments show that the TBWP of the stepped linear, stepped arbitrary, and Costas sequence microwave signal can be over 4.5 × 107. Our paper offers an integrated FH microwave generation approach to support the optics communications and the next-generation photonic radar systems. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate an on-chip pulse shaper for 125-GHz microwave waveform generation. The pulse shaper is implemented based on a silicon-on-insulator (SOI) platform that has a structure with eight-tap finite impulse response (FIR) and there is an amplitude modulator on each tap. By controlling the thermal heaters on the amplitude modulators, we obtain several signals centered at 125 GHz with typical envelopes, such as square envelope, triangular envelope, sawtooth envelope, Gaussian envelope, etc. Our scheme has some significant advantages, such as the central frequency of the generated microwave waveforms is larger than 100 GHz, and it has wide bandwidth when changing the time delay of the adjacent taps and compactness, capability for integration with electronics and small power consumption are also its merits. [ABSTRACT FROM PUBLISHER]

A tunable single passband microwave photonic filter (MPF) of overcoming fiber dispersion induced amplitude fading of the microwave passband is proposed and demonstrated. The passband amplitude of the MPF can be kept invariant for different central frequencies. The scheme is realized based on a dual-drive Mach–Zehnder modulator (DDMZM) and a broadband optical source sliced by a delay interferometer. The DDMZM is single-electrode driven and the microwave signal is modulated onto the optical carrier with simultaneous phase and intensity modulation formats. The ratio of the two modulation formats can be controlled by adjusting the bias of DDMZM to compensate the dispersion-induced amplitude fading at any passband of the MPF. In the experiment, the proposed MPF can be tuned between 0 and 30 GHz and the rejection ratio exceeds 30 dB. [ABSTRACT FROM PUBLISHER]

A novel and simple microwave photonic filter (MPF) is proposed and experimentally demonstrated. The MPF can be switched between low-pass and high-pass frequency responses. The MPF is realized by using an electro-optic phase modulator (EOPM) and two cascaded tunable optical bandpass filters (TOBFs). One TOBF (TOBF1) is used to change the modulation format of the phase modulated signal and, consequently, switch the MPF between low-pass and high-pass frequency responses. The other TOBF (TOBF2) is used to adjust the cutoff frequencies of the low-pass and the high-pass frequency responses. In the experiment, a switchable MPF from 0 to 40 GHz is demonstrated. By changing the center wavelength of TOBF2, the cutoff frequencies of the low-pass and the high-pass frequencies are continuously changed from 2.9 to 20.1 GHz and from 15.4 to 31.2 GHz, respectively. [ABSTRACT FROM PUBLISHER]

A novel photonic approach to generating a phase-coded microwave signal with a precise \pi phase shift is proposed and demonstrated. The approach is realized based on a quadrature phase shift keying (QPSK) modulator. In the QPSK modulator, one Mach–Zehnder modulator (MZM) is biased at its minimal transmission point to achieve carrier suppressed modulation, and the other paralleled MZM is biased to achieve binary-phase shift keying modulation. When the CSM signal and the BPSK signal are combined at the output port of the QPSK modulator, a phase-coded microwave signal with a precise \pi phase shift is generated. Both simulation and experiment are carried out to verify our scheme. The scheme exhibits flexible reconfigurability of encoding different bit pattern chips, large bandwidth of phase-encoding, and broadband frequency tunability. In the experiment, phase-coded microwave signals at 5 and 10 GHz with a precise \pi phase shift are successfully generated. [ABSTRACT FROM PUBLISHER]

We theoretically and experimentally investigate a microwave photonic filter with an electrooptic phase modulator and an array waveguide grating, which acts as a detuned two-channel wavelength division de-multiplexer. In the experiment, a microwave notch filter with a Q N factor of 236 and a rejection ratio of 31 dB is obtained by introducing microwave subtraction directly in optical domain. The parameter Q N factor is defined to measure the rejection selectivity of a microwave notch filter and corresponding to the Q factor in a microwave bandpass filter. A microwave bandpass filter with a Q factor of 245 and a rejection ratio of 38 dB is also obtained. The relationship between the Q factor of the microwave bandpass filter and the Q N factor of the microwave notch filter is measured. The variations of Q and Q N versus the detuning of the tunable optical bandpass filter (TOBF), which is incorporated in the recirculating delay line loop, is also measured and discussed. Simulation results about the influences of the wavelength division de-multiplexer and TOBF on the microwave frequency response are also presented and analyzed. [ABSTRACT FROM PUBLISHER]

A tunable microwave photonic filter with complex coefficients is presented. The complex coefficient is generated using an all-optical radio-frequency (RF) phase shifter, which contains an optical differentiator to realize phase modulation to intensity modulation conversion. The phase of the RF signal can be tuned continuously by simply controlling the optical power through changing variable optical attenuators. A two-tap tunable filter with one complex coefficient is experimentally demonstrated and a continuous tuning range of a half free spectral range is realized without changing the shape of the frequency response. [ABSTRACT FROM PUBLISHER]

Abstract: A novel technique to implement a microwave photonic filter structure with multiple taps and arbitrary frequency response is presented. The proposed filter is based on Four-Wave Mixing (FWM) and Cross-Gain Modulation (XGM) in a semiconductor optical amplifier (SOA). Two-tap notch filter and three-tap bandpass filter with arbitrary bipolar tap generation, high rejection ratio, and widely tunability are successfully demonstrated in the experiment. Extensions to this concept by adding new probe light to provide more taps and improve the bandwidth to high frequency regime are also discussed. [Copyright &y& Elsevier]