Loading [MathJax]/extensions/MathZoom.js
Single-modulator Based Multi-Format Switchable Signal Generator Without Background Noise | IEEE Journals & Magazine | IEEE Xplore

Single-modulator Based Multi-Format Switchable Signal Generator Without Background Noise


Abstract:

A photonic multi-format background-free binarily modulated microwave signal generator using a single dual-polarization dual-parallel Mach–Zehnder modulator is proposed an...Show More

Abstract:

A photonic multi-format background-free binarily modulated microwave signal generator using a single dual-polarization dual-parallel Mach–Zehnder modulator is proposed and demonstrated. The proposed generator features good reconfiguration and switchability. By simply adjusting the direct current biases of the modulator, amplitude shift keying (ASK), phase shift keying (PSK) and frequency-shift keying (FSK) microwave signals can be generated. Benefiting from the complementary intensity modulation, there is no residual baseband modulated signal in the generated binarily modulated signals. The system does not involve any optical or electrical filters, which ensures good tunability of the generator. By changing the frequency of the driven microwave carrier and bit rate of the electrical coded signal, the frequency and rate of the generated multi-format signals can be adjusted accordingly. The multi-format switchable signal generator has great potential in multi-functional communication and radar systems.
Published in: Journal of Lightwave Technology ( Volume: 40, Issue: 20, 15 October 2022)
Page(s): 6693 - 6700
Date of Publication: 04 April 2022

ISSN Information:

Funding Agency:


I. Introduction

Binarily modulated microwave signals are always used in electronic warfare, radar and communication systems. Amplitude shift keying (ASK), phase shift keying (PSK) and frequency-shift keying (FSK) microwave signals are basic binarily modulated signals and can be used to synthesize high-order modulated signals to increase the system performance [1]–[4]. Limited by the electronic bottleneck, the ASK, PSK, and FSK signals generated in the electronic domain suffer from low carrier frequency and coding bit rate, which cannot cope with the increasing communication capability and millimeter-wave radar. Microwave photonics has the characteristics of high frequency, large bandwidth, anti-electromagnetic interference, and reconfiguration [5], [6]. Therefore, photonic generation of binarily modulated microwave signals has become a promising signal generation technique. For the generation of ASK signal, frequency up-conversion is a commonly used method [7]. However, it is necessary to further filter out the severe leaked local oscillator (LO) signal to decrease the interference to the receiver detection. Based on direct photonic conversion technique [8] and frequency-to-time mapping [9], the LO signal can be suppressed. Whereas, some baseband components, which are called “background noise” are involved in the generated ASK signal. The background noise may result in crosstalk with other signals. By taking use of the phase modulation and intensity modulation switching technique [10], [11], LO-free and background-free ASK signal can be generated. For the PSK signal, it can be generated by coding the relative phase of two optical signals [12], [13]. Based on the vector sum method, photonic generation of background-free PSK signal is achieved [14]. By switching the modulation state of the modulator at the positive and negative quadrature bias points of its transmission curve, PSK signal can also be successfully generated [15]. Through the combination of double-sideband modulated signal and phase modulated optical carrier, binary PSK signal is produced [16]. For the FSK signal generation, a polarization modulator (PolM) is always used to switch the orthogonal polarization state of the output optical signal. By cascading a polarization-dependent modulator which is driven by two microwave signals of different frequencies, an FSK signal can be obtained [17], [18]. Photonic generation of FSK signal can be realized via equivalently changing the bias of a dual-drive Mach-Zehnder modulator (DDMZM), driven by a coding signal and a microwave carrier, at quadrature and the minimum transmission points [19]. In order to eliminate the background noise, a unipolar ASK signal is mixed with an RF clock, and a DDMZM is driven to generate a background-free FSK signal [20]. Nevertheless, the reconfigurability of the all above schemes is insufficient, since they can only generate binarily modulated signals in one format.

References

References is not available for this document.