Opto-Electronic Oscillators for Micro- and Millimeter Wave Signal Generation

Mehmet Alp Ilgaz,Bostjan Batagelj

doi:10.3390/electronics10070857

Abstract

High-frequency signal oscillators are devices needed for a variety of scientific disciplines. One of their fundamental requirements is low phase noise in the micro- and millimeter wave ranges. The opto-electronic oscillator (OEO) is a good candidate for this, as it is capable of generating a signal with very low phase noise in the micro- and millimeter wave ranges. The OEO consists of an optical resonator with electrical feedback components. The optical components form a delay line, which has the advantage that the phase noise is independent of the oscillator’s frequency. Furthermore, by using a long delay line, the phase noise characteristics of the oscillator are improved. This makes it possible to widen the range of possible OEO applications. In this paper we have reviewed the state of the art for OEOs and micro- and millimeter wave signal generation as well as new developments for OEOs and the use of OEOs in a variety of applications. In addition, a possible implementation of a centralized OEO signal distribution as a local oscillator for a 5G radio access network (RAN) is demonstrated.

Highlights

High-precision signal oscillators are needed in a variety of fields such as satellite communications, optical communications, radar applications, radio-over-fiber communications, etc. [1]
Phase-locked loops (PLLs) are alternative solutions that are widely used in practice to improve the long-term stability of the opto-electronic oscillator (OEO) signal
The simple, single-loop OEO cannot meet the requirements of the centralized OEO for 5G radio access network (RAN)

Summary

Introduction

High-precision signal oscillators are needed in a variety of fields such as satellite communications, optical communications, radar applications, radio-over-fiber communications, etc. [1]. For a millimeterwave OEO, a high-quality opto-electronic filter was proposed, e.g., a Q-factor of 30,000 at a central frequency of 29.99 GHz [73] This resulted in an 83 dB SMSR and a −113 dBc/Hz SSB phase noise at a 10 kHz offset. The cascaded filter configuration was implemented with a single passband filter having an opto-electronic filter With this approach, an SMSR of 125 dB and an SSB phase noise of −103 dBc/Hz for a 10 kHz offset at the 17.33 GHz carrier were achieved. Phase-locked loops (PLLs) are alternative solutions that are widely used in practice to improve the long-term stability of the OEO signal. A classic solution such as temperature stabilization has good phase noise performance and short-term stability

Wideband Tunable Frequency Generation

Optical Signal Distribution for the 5G Radio Access Network

Conclusions