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Foto: Universität Paderborn

Meysam Bahmanian


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Locking of microwave oscillators on the interharmonics of mode-locked laser signals

M. Bahmanian, C. Kress, C. Scheytt, Optics Express (2022), 14

In this paper, the theory of phase-locking of a microwave oscillator on the interharmonics, i.e. non-integer harmonics, of the repetition rate of the optical pulse train of a mode-locked laser (MLL) is developed. A balanced optical microwave phase detector (BOMPD) is implemented using a balanced Mach-Zehnder modulator and is employed to discriminate the phase difference between the envelope of the optical pulses and the microwave oscillator. It is shown mathematically that the inherent nonlinear properties of BOMPD with respect to the microwave excitation amplitude can be used for interharmonic locking. The characteristic functions of the phase detector for interharmonic locking are derived analytically and are compared with the measurement results. An opto-electronic phase-locked loop (OEPLL) is demonstrated whose output frequency locks on interharmonics of the MLL repetition rate when an appropriate modulator bias and sufficient RF amplitude are applied. Thus, for the first time theory and experiment of reliable locking on interharmonics of the repetition rate of a MLL are presented.

A Low Phase Noise 77 GHz Frequency Synthesizer for Long Range Radar

S. Kruse, M. Bahmanian, S. Fard, M. Meinecke, H.G. Kurz, C. Scheytt, in: European Radar Conference (EuRAD), 2022


Analysis of the effects of jitter, relative intensity noise, and nonlinearity on a photonic digital-to-analog converter based on optical Nyquist pulse synthesis

C. Kress, M. Bahmanian, T. Schwabe, J.C. Scheytt, Opt. Express (2021), 29(15), pp. 23671–23681

An analysis of an optical Nyquist pulse synthesizer using Mach-Zehnder modulators is presented. The analysis allows to predict the upper limit of the effective number of bits of this type of photonic digital-to-analog converter. The analytical solution has been verified by means of electro-optic simulations. With this analysis the limiting factor for certain scenarios: relative intensity noise, distortions by driving the Mach-Zehnder modulator, or the signal generator phase noise can quickly be identified.


Ultra-Low Phase Noise Frequency Synthesis for THz Communications Using Optoelectronic PLLs

C. Scheytt, D. Wrana, M. Bahmanian, I. Kallfass, in: 2020 Third International Workshop on Mobile Terahertz Systems (IWMTS), 2020

Recently it has been demonstrated that an optoelectronic phase-locked loop (OEPLL) using a mode-locked laser as a reference oscillator achieves significantly lower phase noise than conventional electronic frequency synthesizers. In this paper a concept for an OEPLL-based frequency synthesizer is presented and it is investigated how it can be used as a local oscillator (LO) for THz transceivers in order to improve the signal quality in THz wireless communications. The concept of the OEPLL is presented and it's measured phase noise is compared to the phase noise of a laboratory-grade electronic frequency synthesizer. The measured phase noise spectra of both synthesizers at 10 GHz are then used to model LO phase noise at 320 GHz. Based on models of generic zero-IF transmit and receive frontends, THz signals with different modulation formats and Baud rates are simulated at system level using the modeled LO phase noise for the two LO approaches. Finally, the results are compared.

Wide-Band Frequency Synthesizer with Ultra-Low Phase Noise Using an Optical Clock Source

M. Bahmanian, S. Farkhondehkhouy Fard, B. Koppelmann, C. Scheytt, in: 2020 IEEE/MTT-S International Microwave Symposium (IMS), IEEE, 2020

This paper presents an ultra-wideband and ultra-low noise frequency synthesizer using a mode-locked laser as its reference. The frequency synthesizer can lock in the frequency range from 2 GHz to 20 GHz on any harmonic of a mode-locked laser optical pulse train. The integrated rms-jitter (1 kHz-100 MHz) of the synthesizer is less than 5 fs in the frequency range from 4 GHz to 20 GHz with a typical value of 4 fs and a minimum of 3 fs. This is the first reported wideband phase locked loop achieving sub-10 fs rms-jitter for offset frequencies larger than 1 kHz.


Octave-Band Microwave Frequency Synthesizer Using Mode-Locked Laser as a Reference

M. Bahmanian, J. Tiedau, C. Silberhorn, C. Scheytt, in: 2019 International Topical Meeting on Microwave Photonics (MWP), 2019, pp. 1-4

An octave-band voltage-controlled oscillator is phase-locked on the envelope of the pulse train from a mode-locked laser. The locking scheme employs a balanced Mach-Zehnder modulator with two photodiodes as a phase detector. The phase.locked loop has a loop bandwidth of approximately 1MHz and an in-band phase noise of approximately -135dBc/Hz at all frequencies. The integrated jitter from 1kHz to 100MHz is 21fs, 18.3fs and 13.8fs at 5.016GHz, 7.6GHz and 10.032GHz carrier frequencies, respectively. To the authors' knowledge, this is the best jitter performance reported for a PLL with MZM-based phase detection and the first reported PLL of this type featuring an octave-band frequency range.

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