Abstract
This paper presents a new scheme of a cost-effective tunable millimeter-wave (MMW) frequency synthesizer based on an ultra-wideband electro-optic frequency comb. The architecture for the quasi-tunable millimeter-wave frequency synthesizer mainly consists of a compact ultra-wide flat electro-optic frequency comb and a multi-tone frequency generator, which only includes a quantum dot mode-locked laser, a LiNbO3 dual-driving Mach–Zehnder modulator (DD-MZM) and Uni-traveling-carrier photodiode (UTC-PD). MMW signals generated with a quasi-tunable frequency are experimentally demonstrated. The difference in power is obtained for the different frequencies. The linewidth of the quasi-tunable frequency signals is less than 273 Hz. In addition, the single side band (SSB) phase noise of the 25, 37.5, 50 and 75 GHz is measured as −115, −106, −102 and −95 dBc/Hz at an offset of 1 kHz, respectively. The proposed frequency synthesizer has ultra-low phase noise, quasi-tunable frequency and simple structure. The research results of the frequency synthesizer are applied for 5G+ transmission with radio wave working at K-band and V-band. The flexible, compact and robust MMW frequency synthesizer is suitable for the future of ultra-high capacity 5G+ communication.
Highlights
Accepted: 11 November 2021The increased bandwidth demand for high capacity and ultra-low latency services of fifth generation mobile networks (5G) has promoted the exploration of high-capacity radio-over-fiber (ROF) system to accommodate a wide range of novel applications with diverse requirements, which will be prospective for 5G/5G+ wireless access [1], internet of things, disaster emergency communication and military applications
The performance of the tunable MMW frequency synthesizer is researched by using high performance test instruments, such as complex optical spectrum analyzer (OSA), tunable RF filter, a 110 GHz Uni-traveling-carrier photodiode (UTC-PD) and an electrical spectrum analyzer (ESA)
A tailored optical frequency comb (OFC) with frequency spacing of 25 GHz is generated from the dual-driving Mach–Zehnder modulator (DD-MZM) driven by a sinusoidal RF signal
Summary
The increased bandwidth demand for high capacity and ultra-low latency services of fifth generation mobile networks (5G) has promoted the exploration of high-capacity radio-over-fiber (ROF) system to accommodate a wide range of novel applications with diverse requirements, which will be prospective for 5G/5G+ wireless access [1], internet of things, disaster emergency communication and military applications. ROF possesses wide bandwidths provided by the millimeter-wave (MMW) frequency resource [2] and integrates the advantages of wireless and optical systems. ROF systems are generally centralized radio access networks for 5G using the wavelength-division multiplexing (WDM) technique to offer ultra-wideband wireless delivery with low interference by combining data transmitted on different wavelengths based on many individual lasers, which are not intrinsically phase-locked. Benefiting from the superiority of stable frequency spacing and wideband phase coherence of the optical comb lines and optical frequency comb (OFC) has emerged as a potential substitute for hundreds of individual lasers in WDM systems [4], due to the reduced energy consumption
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