Binary Phase-coded Microwave Research Articles

Photonic Generation of Dual-Band Dual-Format Phase-Coded Microwave Signals

We propose and demonstrate a photonic scheme to generate dual-band dual-format phase-coded microwave signals based on a commercial dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM), which consists of two sub-DDMZMs with orthogonal polarization states. Two microwave signals with different frequencies are fed to the sub-DDMZMs, separately. The power of microwave signals is optimized to well suppress the optical carrier at the corresponding arms to avoid the optical interference between two arms of the sub-DDMZMs. The key novelty of our scheme is that two different kinds of phase-modulated microwave signals can be generated simultaneously. One is a binary phase-coded microwave signal in pulse mode, the other is an arbitrary phase-modulated signal in continuous wave mode. The proposed scheme is theoretically analyzed and experimentally verified.

Photonic Generation of a Windowed Phase-Coded Microwave Waveform With Suppressed Spectrum Sidelobes

An approach to photonic generation of a windowed binary phase-coded microwave waveform with suppressed spectrum sidelobes is proposed and demonstrated. An optical double sideband plus carrier signal with the carrier and the two sidebands being orthogonally polarized is generated by a dual-polarization quadrature phase shift keying (DP-QPSK) modulator, with the generated signal sent to a phase modulator (PM) where phase coding is performed. The PM can support phase modulation in two orthogonal polarization directions. The phase-modulated signals are projected to one polarization direction and detected at a photodetector (PD). Switching the polarity of the coding signal, a π phase shift is introduced. Since the amplitude of the generated signal is dependent on the amplitude of the input coding signal, a windowing function is applied to the generated waveform by using a windowed input phase coding signal, to suppress the sidelobes in the spectrum of the generated microwave waveform. The key features of the proposed waveform generator include all-optical generation without the need of electronic components and optical filters, thus ensuring a wide operating frequency range. The proposed phase-coded microwave waveform generator also has the ability to switch between the fundamental and harmonic carrier frequency by controlling the modulator bias voltages. Experimental results show that, using a windowed 64-bit Gaussian pseudo-random binary sequence coding signal, a phase-coded microwave waveform is generated with the sidelobes of the spectrum largely suppressed by 20 dB and a pulse compression ratio as large as 133. Generation of binary phase-coded microwave waveforms at the 2nd harmonic carrier frequencies is also demonstrated experimentally.

Phase-coded microwave signal generation with a built-in optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator.

A scheme for binary phase-coded microwave signal generation is proposed and experimentally demonstrated with a dual-parallel Mach-Zehnder modulator (DPMZM). The carrier of the generated phase-coded signal is provided by the built-in dual-loop optoelectronic oscillator (OEO) based on the DPMZM. The principle of this signal generator and the oscillating condition of the OEO is theoretically described in detail. It is found that phase-coded signals can be produced by setting the three working points and the modulation depth of the DPMZM. In the proving experiment, a 10-GHz oscillating signal with a side mode suppression ratio of 49 dB is generated. The phase noise of this carrier wave is measured to be -80dBc/Hz at 10 kHz offset with a 100-m and 1-km optical fiber used in the two oscillation loops. When 1-Gbit/s and 2-Gbit/s coding signals are, respectively, applied to the DPMZM, two 10-GHz self-oscillating phase-coded signals are eventually produced, and the π phase shift in the signals is successfully confirmed with the phase information extracted from the phase-coded signals.

Photonic Generation of Phase-Coded Microwave Signals Based on Fourier Domain Mode Locking

We report a novel photonic scheme to generate binary phase-coded microwave signals by using two cascaded phase modulators (PMs) based on a Fourier domain mode-locked (FDML) optoelectronic oscillator (OEO). The first PM is driven by a series of electrical coding signals to modulate the phase of the optical carrier. The second PM is a construction of the FDML OEO, which realizes phase-modulation to intensity-modulation conversion together with a phase-shifted fiber Bragg grating. Phase-coded microwave signals can be generated when the period of the electrical coding signal matches with the round-trip time of the OEO. A π phase shift of the phase-coded microwave signals can be achieved by properly adjusting the level of the electrical coding signal. The key point of our work is that phase-coded microwave signals can be generated directly from the FDML OEO cavity. Besides, the proposed system has great reconfigurability in terms of center frequency and bit rate. Our scheme is theoretically analyzed and experimentally verified. Phase-coded microwave signals with a bit rate of 420 Mb/s and center frequency of 9.3 GHz, as well as with a bit rate of 2 Gb/s and center frequency of 12.7 GHz are successfully generated in the experiment.

Photonic Scheme for the Generation of Background-Free Phase-Coded Microwave Pulses and Dual-Chirp Microwave Waveforms

We propose a photonic scheme to generate binary phase-coded microwave pulses and dual-chirp microwave waveforms without baseband-modulated signals (background noise) based on a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM) which contains x-DDMZM and y-DDMZM at two different polarization states. A radio frequency (RF) signal from a microwave source is transferred into two differential RF signals and employed into one arm of x-DDMZM and one arm of y-DDMZM, while a baseband signal from an arbitrary waveform generator is divided by an electronic coupler and then driven into the two other arms of DP-DDMZM. By adjusting the phase differences between the x-DDMZM and the y-DDMZM, binary phase-coded pulses and dual-chirp signals without baseband-modulated signals are generated. The proposed scheme can eliminate the interference caused by baseband-modulated signals, and satisfy different radar applications for different frequency bands. Experimental results show that phase-coded signals at 15 GHz with the bit rates of 1 Gb/s and 2 Gb/s and dual-chirp signals at 10 GHz and 15 GHz with the time durations of 0.5 μs are successfully generated. The reported scheme is well analyzed in theory and verified by experiment.

Reconfigurable photonic binary phase-coded microwave signal generator with fundamental/subharmonic carrier frequency.

A reconfigurable photonic binary phase-coded microwave signal generator with fundamental/subharmonic carrier frequency is proposed and experimentally investigated based on a dual-electrode dual parallel Mach-Zehnder modulator (DE-DPMZM). The local oscillator (LO) signal and coding signal are intensity modulated and phase modulated, respectively, on the two arms of the DE-DPMZM. The bias voltage of the intensity modulator is set to the quadrature or maximum working points to produce fundamental or subharmonic frequency, respectively. By precisely adjusting the amplitude of the LO signal and the bias voltage of the parent modulator, the light carriers of both arms of the DE-DPMZM can be eliminated. After detection, binary phase-coded microwave signal with frequency equal to or twice the frequency of the LO signal can be generated. The proposed system has a simple structure, high reconfigurability, and good frequency tunability due to its avoidance of using optical filters. In the experiment, phase-coded microwave waveforms at 6 GHz and 11 GHz are generated by using 6 GHz and 11 GHz LO signals or 3 GHz and 5.5 GHz LO signals, respectively. Meanwhile, the performance is evaluated in terms of phase recovery accuracy and pulse compression capability. The experimental results show that the proposed generator has high peak-to-sidelobe ratio, which has practical significance for radar detection of weak targets.

Photonics Generation of Pulsed Arbitrary-Phase-Coded Microwave Signals Based on the Conversion Between Intensity Modulation and Phase Modulation

This article proposes a pulsed arbitrary-phase-coded microwave signals (APCMSs) photonics generation system. The key to this scheme is to achieve the single-sideband modulated (SSBM) optical signal with the conversion capability between intensity modulation and phase modulation by utilizing dual-parallel Mach–Zehnder modulator (DPMZM) and optical bandpass filter (OBPF). Through heterodyne detection of the SSBM optical signal, pulsed APCMSs can be generated. Unlike previous continuous-wave (CW) APCMSs and pulsed binary phase-coded microwave signals (PCMSs) photonics generation schemes, our scheme provides a pulsed APCMSs generation scheme. The scheme realizes the generation of APCMSs without CW background signals, and the scheme is not only suitable for binary phase codes but also suitable for arbitrary phase codes. The useless CW background signals are effectively suppressed without cascading an intensity modulator for gating operation and the coded phases are linear with the input pre-encoding signals amplitudes, leading to great improvement of practical application values. A theory analysis, a system simulation, and a proof-of-concept experiment are provided. Simulation demonstrates the generations of 2-Gbps 14-GHz and 1-Gbps 16-GHz pulsed APCMSs. The generations of 2-Gbps 14-GHz and 1-Gbps 16-GHz pulsed PCMSs with a 13-bit binary Barker-code and a 16-bit quaternary Frank-code are verified in experiment.

Photonic generation of binary and quaternary phased-coded microwave pulses with tunable frequency multiplication factor

ABSTRACT A photonic approach to generate binary and quaternary phase-coded microwave pulses with tunable frequency multiplication factor (FMF) is proposed and demonstrated. By adjusting the input electrical signals, the scheme can generate pulsed radar waveforms with tunable FMF and reconfigurable phase coding pattern. In the scheme, two pairs of orthogonally polarized ±2nd-order or ±4th-order sidebands are separated into two single sideband signals through an optical sideband separation module. One of the sidebands is then modulated by the coding signal through a dual-drive Mach-Zehnder modulator. By detecting the recombined two sidebands, binary or quaternary phase-coded microwave pulses with FMF of 4 or 8 can be generated. In the simulation experiments, binary and quaternary phase-coded microwave pulses at 20 and 40 GHz are generated. The phase information of the pulses is consistent with the initial coding sequence. Furthermore, the generated phase-coded microwave pulses show great compression capability.

A background-free phase-coded microwave pulse generator by optoelectronic oscillation

We propose and demonstrate a photonic scheme to generate background-free binary phase-coded microwave pulses based on optoelectronic oscillation (OEO). The significant merit of our pulse generator is that an external microwave source which is always essential in previous works is no more required. The binary phase-coded microwave pulse is directly generated by truncating an OEO signal into pulses. Moreover, only a single modulator is used in our system which performs two important functions. One is the construction of OEO loop, the other is the phase-coding of microwave pulses. Since only the phase of optical signal is modulated, the phase-coded microwave pulses are free from baseband frequency components. The proposed scheme is theoretically analyzed and experimentally verified.

All-optical generation of binary phase-coded microwave pulses without baseband components based on a dual-parallel Mach-Zehnder modulator.

In this paper, we propose an all-optical system for the generation of binary phase-coded microwave pulses without baseband components. The scheme is based on a dual-parallel Mach-Zehnder modulator (DPMZM). By properly applying the coding signals and the microwave signals to the precisely biased DPMZM, accurate π phase shift binary phase-coded microwave pulses without baseband components can be generated. The proposed system has an extremely simple and stable all-optical structure, leading to a large frequency tuning range and a high signal quality. The operation of the system is very easy. The generation of the 2-Gbit/s 14-GHz and 4-Gbit/s 16-GHz binary phase-coded microwave pulses under different coding signal amplitudes and microwave carrier powers are experimental verified. The results show that the proposed binary phase-coded microwave pulses generation system has high quality and performance.

Photonic generation of background-free binary phase-coded microwave pulses.

We report a photonic scheme to generate background-free frequency-doubled binary phase-coded microwave pulses. The key component is a dual-polarization dual-parallel Mach-Zehnder modulator that is used to realize phase modulation and carrier-suppressed double second-order sideband modulation at two orthogonal polarization states, respectively. The π phase jump of the frequency-doubled phase-coded microwave pulse is dependent on the polarity of the coding signal rather than its amplitude. Besides, the generated microwave pulses are free from the baseband-modulated signals, because the optical power launched to a photodetector (PD) keeps constant all the time. Since no electrical or optical filters are involved, the photonic generator can ensure a broad operation bandwidth and wide tunability. Our scheme is theoretically analyzed and experimentally verified. The 4Gb/s at 16GHz and 7Gb/s at 28GHz background-free frequency-doubled phase-coded microwave pulses have been successfully generated.

Photonic generation of binary phase-coded microwave waveforms and phase-coded pulses with ultrawide frequency tunable range

A scheme that can produce a continuous wave (CW) phase-coded signal and phase-coded pulses is proposed. The proposed scheme is based on a dual-polarization Mach–Zehnder modulator (DPol-MZM), a polarization modulator (PolM) and a balanced photodetector (BPD) without the help of an electrical phase shifter or an electrical power divider. In DPol-MZM, a carrier-suppressed double sideband (CS-DSB) signal and an optical carrier are, respectively, produced in the upper and lower arms, which are in two orthogonal polarization states. The output is then sent to a PolM. The polarization multiplexed CS-DSB and optical carrier are phase modulated by driving the RF port of the PolM with a coding signal. After beating between the modulated CS-DSB and optical carrier in a BPD, a stable CW phase-coded signal or phase-coded pulses can be obtained. The proposed scheme is experimentally verified. Phase-coded microwave waveforms at 6 and 11 GHz are generated and phase-coded pulses at 11 GHz are also produced.

Phase-coded microwave signals generation using a dual parallel construction including two phase modulators

A photonic approach to realizing binary phase-coded microwave signal generation using a dual parallel construction including two phase modulators (PMs) was proposed and demonstrated. A beam CW is split into two beams light wave with equal power in the dual parallel construction, one beam is modulated in a PM driven by a radio frequency (RF) microwave signal in the upper arm, and the other beam is modulated by another PM driven by a binary coding electrical pulse sequence in the under arm, then the two phase-modulated beams combine and interfere. When the interference light field is send to a high-speed photodetector (PD) for beating, 2 Gbit/s binary phase-coded 10 GHz and 2.5 Gbit/s phase-coded 20 GHz microwave waveform with a π phase shift was respectively achieved, and corresponding pulse compression ratio is 20 and 16.5, respectively. The obtained phase-coded microwave signals exhibit a good pulse compression performance, which can find potential applications in modern radar systems and wireless communications.

Multi-format signal generation using a frequency-tunable optoelectronic oscillator.

A novel photonic approach for multi-format signal generation based on a frequency-tunable optoelectronic oscillator (OEO) is proposed using a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator. The upper dual-parallel Mach-Zehnder modulator (DP-MZM) integrated in the DP-QPSK modulator is properly biased to serve as an equivalent phase modulator, which functions in conjunction with a phase-shifted fiber Bragg grating (PS-FBG) in the OEO loop as a high-Q microwave photonic band-pass filter. The lower DP-MZM in the DP-QPSK modulator injected by the oscillation signal functions as a frequency multiplier, a phase-coded microwave signal generator or an optical frequency comb generator, respectively, with different signal injection methods. An experiment is performed. When the lower DP-MZM serves as a frequency multiplier, tunable frequency-doubled and quadrupled microwave signals up to 40 GHz are generated without using an optical notch filter; and if it functions as a phase-coded microwave signal generator, fundamental and frequency-doubled binary phase-coded microwave signals are generated with a tunable frequency. Furthermore, tunable five-line optical frequency combs are also generated using the compact system without an external RF source. The performance of the generated signals is also investigated.

A Frequency-Tunable Binary Phase-Coded Microwave Signal Generator With a Tunable Frequency Multiplication Factor

A novel frequency-tunable binary phase-coded microwave signal generator with a tunable frequency multiplication factor is proposed. The key component of the proposed system is a dual-polarization quadrature phase-shift-keying (DP-QPSK) modulator, which is driven by the microwave reference signal and the coding signal. By properly controlling the bias points of the DP-QPSK modulator and the amplitudes of the microwave reference signal and the coding signal, a fundamental, frequency-doubled, frequency-tripled or frequency-quadrupled binary phase-coded microwave signal can be generated when two orthogonally polarized optical signals at the output of the DP-QPSK modulator are combined and then detected in a photodetector. The proposed system is experimentally evaluated. A binary phase-coded microwave signal is generated at the fundamental, doubled, tripled, or quadrupled frequency. The frequency tunability and the pulse compression performance of the generated phase-coded microwave signals are also experimentally studied.

Photonic Generation of Binary and Quaternary Phase-Coded Microwave Waveforms With Frequency Quadrupling

A photonic approach to generate a phase-coded microwave waveform with frequency quadrupling is proposed and experimentally demonstrated in this paper. The system consists of a dual-parallel Mach-Zehnder modulator (DPMZM), a phase modulator (PM), a fiber Bragg grating (FBG), an optical coupler, and a photodetector. An optical carrier is modulated by a local oscillator (LO) in the DPMZM, and pure ±second-order sidebands are generated. Then, the two sidebands are separated by the FBG, and one of them is modulated by the coding signal through the PM. Both binary and quaternary phase-coded microwave signals with frequency quadrupling of the LO signal can be generated after detecting the recombined two sidebands. The proposed scheme is verified by experiments; phase-coded microwave waveforms at 24 and 12 GHz are generated by applying 6- and 3-GHz LO signals to the DPMZM, respectively. The pulse compression ratios of the generated waveforms are in good agreement with theoretical value.

Photonic generation of arbitrarily phase-modulated microwave signals based on a single DDMZM

We propose and demonstrate a compact and cost-effective photonic approach to generate arbitrarily phase-modulated microwave signals using a conventional dual-drive Mach-Zehnder modulator (DDMZM). One arm (arm1) of the DDMZM is driven by a sinusoidal microwave signal whose power is optimized to suppress the optical carrier, while the other arm (arm2) of the DDMZM is driven by a coding signal. In this way, the phase-modulated optical carrier from the arm2 and the sidebands from the arm1 are combined together at the output of the DDMZM. Binary phase-coded microwave pulses which are free from the baseband frequency components can be generated when the coding signal is a three-level signal. In this case, the precise π phase shift of the microwave signal is independent of the amplitude of the coding signal. Moreover, arbitrarily phase-modulated microwave signals can be generated when an optical bandpass filter is attached after the DDMZM to achieve optical single-sideband modulation. The proposed approach is theoretically analyzed and experimentally verified. The binary phase-coded microwave pulses, quaternary phase-coded microwave signal, and linearly frequency-chirped microwave signal are experimentally generated. The simulated and the experimental results agree very well with each other.

All-optical generation of binary phase-coded microwave signal based on cross-polarization modulation in a highly nonlinear fiber

We report a novel all-optical approach to generate a binary phase-coded microwave signal based on a cross-polarization modulation effect in a highly nonlinear fiber. The carrier frequency of the binary phase-coded microwave signal is widely tunable. Moreover, the precise π phase shift of the microwave signal is independent of the optical power of the control beam. The proposed approach is theoretically analyzed and experimentally verified. For a proof-of-concept demonstration, the binary phase-coded microwave signals with a carrier frequency of 20GHz at a coding rate of 5 Gb/s and with a carrier frequency of 30GHz at a coding rate of 7.5 Gb/s are experimentally generated. The pulse compression capability of the system is also evaluated. The measured and simulated results fit well with each other.

Photonic Generation of Frequency Tunable Binary Phase-Coded Microwave Waveforms

A novel photonic approach to generating a precisely π phase-shifted binary phase-coded microwave waveform with ultra-wide frequency tunable range is proposed and experimentally demonstrated. In the proposed system, a polarization modulator (PolM) functions in conjunction with a polarization controller (PC) and an optical polarizer (Pol) as an equivalent Mach-Zehnder modulator (MZM) with the bias point switchable by applying a binary-coding signal to the PolM. To generate a phase-coded microwave signal at a specific microwave frequency, the binary-coding signal is combined with a microwave signal at that frequency and applied to the PolM. By switching between the two quadrature transmission points or the maximum and the minimum transmission points, a phase-coded microwave waveform at the fundamental or doubled frequency is generated. The proposed technique is experimentally evaluated. A phase-coded microwave waveform at the fundamental and doubled frequency is generated. The tunability of the approach is also experimentally demonstrated.

Single Phase Modulator for Binary Phase-Coded Microwave Signals Generation

We report a new approach to photonic generation of binary phase-coded microwave signals based on the asymmetric phase modulation indexes of a phase modulator in the TE and TM polarization states. The proposed system is extremely simplified compared with any other techniques reported in the previous literature since we only use one phase modulator. The microwave carrier frequency is widely tunable, and the π phase shift of the microwave signal is independent of the amplitude of the electrical driving signal. The proposed technique is theoretically analyzed and experimentally verified at carrier frequencies of 10 and 25 GHz, respectively.