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Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 4 — Feb. 24, 2014
  • pp: 3918–3923
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RF photonic front-end integrating with local oscillator loop

H. Yu, M. Chen, H. Gao, S. Yang, H. Chen, and S. Xie  »View Author Affiliations


Optics Express, Vol. 22, Issue 4, pp. 3918-3923 (2014)
http://dx.doi.org/10.1364/OE.22.003918


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Abstract

Broadband Radio frequency (RF) photonic front-ends are one of the vital applications of the microwave photonics. A tunable and broadband RF photonic front-end integrating with the optoelectronic oscillator (OEO) based local oscillator has been proposed and experimentally demonstrated, in which only one phase modulator (PM) is employed thanks to the characteristic of the PM. The silicon-on-insulator based narrow-bandwidth band-pass filter is introduced for signal processing. The application condition of the proposed RF photonic front-end has been discussed and the performance of the front-end has also been measured. The SFDR at a frequency of about 7.02 GHz is measured to be 88.6 dB-Hz2/3.

© 2014 Optical Society of America

1. Introduction

Microwave photonics has attracted a lot of research interest in the past decades for the applications in antenna remote, phased array and so on, owing to the inherently large processing bandwidth, low loss, attractive size and immunity to electro-magnetic interference [1

1. J. Capmany and D. Novak, “Microwave photonics combines two worlds,” Nat. Photonics 1(6), 319–330 (2007). [CrossRef]

,2

2. J. Yao, “Microwave photonics,” J. Lightwave Technol. 27(3), 314–335 (2009). [CrossRef]

]. RF photonic front-ends as one of the key applications of microwave photonics have been extensively investigated [3

3. R. C. J. Hsu, A. Ayazi, B. Houshmand, and B. Jalali, “All-dielectric photonic-assisted radio front-end technology,” Nat. Photonics 1(9), 535–538 (2007). [CrossRef]

8

8. T. R. Clark and R. Waterhouse, “Photonics for RF Front Ends,” IEEE Microw. Mag. 12(3), 87–95 (2011). [CrossRef]

]. Typical microwave systems incorporate mixing process at the modulator, RF oscillator, signal processor and down-converter in the RF photonic front-ends area [8

8. T. R. Clark and R. Waterhouse, “Photonics for RF Front Ends,” IEEE Microw. Mag. 12(3), 87–95 (2011). [CrossRef]

] as shown in Fig. 1.
Fig. 1 Notional diagram of simplex radar system consisting of a Digital-to-Analog Converter (DAC), Analog-to-Digital Converter (ADC), transmitter and the proposed RF photonic front-end. The proposed RF photonic front-end contains the mixing process with a feedback loop to generate the LO, a signal processor and the photo-detector (PD) based down-converter.
The photonic-assisted technology accompanying the large dynamic range, fast-tunability (~μs) and broadband features can be highlighted [9

9. S. A. Pappert and B. Krantz, “RF photonics for radar front-ends,” in Proc. IEEE Radar Conf., Boston, MA, 965–970 (2007).

] relative to the electro-method [10

10. X. Guan and A. Hajimiri, “A 24-GHz CMOS Front-End,” IEEE J. Solid-State Circuits 39(2), 368–373 (2004). [CrossRef]

,11

11. R. T. Logan Jr and E. Gertel, “Millimeter-wave photonic downconvertors: Theory and demonstrations,” Proc. SPIE 2560, 58–69 (1995). [CrossRef]

] which would be limited by the generation and re-radiation of the local oscillator (LO) and the reduced dynamic range due to multi stages down-conversion. For most of the RF photonic front-ends reported, the photonic tunable down-conversion is realized by the tunable LOs [9

9. S. A. Pappert and B. Krantz, “RF photonics for radar front-ends,” in Proc. IEEE Radar Conf., Boston, MA, 965–970 (2007).

]. The LOs can be settled by several types, such as one more modulator and a microwave source to generate the LO [12

12. A. Agarwal, T. Banwell, and T. K. Woodward, “Optically filtered microwave photonic links for RF signal processing applications,” J. Lightwave Technol. 29(16), 2394–2401 (2011). [CrossRef]

] or directly introduce another tunable laser [13

13. B. M. Haas and T. E. Murphy, “Linearized downconverting microwave photonic link using dual-wavelength phase modulation and optical filtering,” IEEE Photon. J. 3(1), 1–12 (2011). [CrossRef]

] to serve as the LO for mixing. The optoelectronic oscillator (OEO) with a large frequency range and ultralow phase noise can be employed as the LO for mixing in the front-end to achieve a large processing range and fast tunability, which can convert the energy from continuous wave light to the microwave even millimeter wave signals [14

14. L. Maleki, “Sources: The optoelectronic oscillator,” Nat. Photonics 5(12), 728–730 (2011). [CrossRef]

,15

15. X. Xie, C. Zhang, T. Sun, P. Guo, X. Zhu, L. Zhu, W. Hu, and Z. Chen, “Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter,” Opt. Lett. 38(5), 655–657 (2013). [CrossRef] [PubMed]

]. However, to avoid the impact on the oscillation of the OEO, some methods have been proposed, such as utilizing the polarization splitter to divide the RF signal and the LO at different polarization [16

16. D. Zhu, S. Pan, S. Cai, and D. Ben, “High-Performance Photonic Microwave Downconverter Based on a Frequency-Doubling Optoelectronic Oscillator,” J. Lightwave Technol. 30(18), 3036–3042 (2012). [CrossRef]

] or employing some more modulators to up-convert the RF signal to unique wavelength band and filtering out the RF input signal with a wavelength filter in the OEO loop [17

17. W. Shieh, S. X. Yao, G. Lutes, and L. Maleki, “Microwave signal mixing by using a fiber-based optoelectronic oscillator for wavelength division multiplexed systems,” in Opt. Fiber Commun. Conf. Tech. Dig., 358–359 (1997). [CrossRef]

].

In this paper, a large processing range photonic front-end is proposed and experimentally demonstrated. A feedback loop is introduced to the proposed RF photonic front-end to generate the LO for mixing as the LO loop in Fig. 1 shown. The characteristic of the phase modulator (PM) has been made full use of in the proposed RF photonic front-end to integrate the LO to the up-conversion system with the same PM. Moreover, an SOI-based narrow bandwidth band-pass filter is applied to the front-end for signal processing. The processing range of the proposed RF photonic front-end can cover X- to Ka-band thanks to the large frequency range of the OEO based LO and the processing ability of the SOI-based signal processor. The spurious free dynamic range (SFDR) of the front-end is measured to be 88.6 dB-Hz2/3 at a frequency of about 7.02 GHz. The application condition of this front-end has also been discussed. This proposed RF photonic front-end would be a potential design for the monolithic chip integration of the front-ends.

2. Principle

The schematic diagram of the proposed RF photonic front-end integrating with the OEO based LO is shown in Fig. 2(a).
Fig. 2 (a) Schematic diagram of the simple photonic front-end integrating with the OEO based LO for mixing and signal processor, (b) three rounds of the OEO loop. The alternative between the dashed and the solid arrow line of IF means the generation of new components and the old is vanished.
The RF signal received by the broadband antenna is up-converted to optical-domain by a PM and processed by the tunable band-pass filter (TBPF2) and then mixed and down-converted to get the RF output signal which can be applied for post-processing as the blue-dashed frame shown in Fig. 2(a). There are two TBPFs in the whole RF photonic front-end: the broad bandwidth one (TBPF1) is applied for the LO loop and the narrow bandwidth one (TBPF2) is served as the signal processor for photonic-based microwave signal processing. These two TBPFs in this front-end could be controlled by the control signal given by the Post-Processing module. The same PM is utilized to construct the OEO based LO as the LO loop circuit contains a PM, TBPF1, photo-detector (PD1) and power amplifier (PA) [15

15. X. Xie, C. Zhang, T. Sun, P. Guo, X. Zhu, L. Zhu, W. Hu, and Z. Chen, “Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter,” Opt. Lett. 38(5), 655–657 (2013). [CrossRef] [PubMed]

]. The principle of the proposed RF photonic front-end integrating with the OEO based LO with only one modulator will be explained below by Fig. 2(b).

A continuous wave (CW) laser is used as the optical carrier and modulated by the combination of a RF input signal and the OEO based LO with the frequency of separately fs and fLO, and the modulated signal is filtered by TBPF1. The center of the filter is set subtly to keep all the first order of the modulated RF input signal in the filter band with a bandwidth of about Bw and only either the −1 or + 1 order of the LO modulated signal would exist after the filter with a frequency relationship of fs<Bw/2, fs < fLO and fLOBw/2 as shown in Fig. 2(b). The filtered signal is separated to two parts by a 1:1 coupler and one way is for high-resolution photonic signal processing and the other way is sent back to the LO loop and detected by PD1. After PD1, there are mainly two frequency components would exist as shown in Fig. 2(b): the new generated intermediate frequency (IF) signal with a frequency of (fLO-fs) and the LO as presented in Round1. The RF input signal is nearly vanished after PD1 as the beat-frequency signal between the ± 1 order of the RF input phase-modulated signal and the optical carrier have the same frequency and amplitude but a π phase difference. If the beat frequency (fLO-fs) signal would exist all along from now and be amplified by the PA, there would be a badly impact on the LO, but fortunately, after the modulation and PD1 during Round2, the beat frequency (fLO-fs) signal would be vanished as the same reason of the RF input signal as shown in Round2 and also the Round3. The characteristic of the PM has been made full use of in this RF photonic front-end to eliminate the impact of the RF input signal and the beat frequency (fLO-fs) signal on the OEO based LO. So, only one modulator is required in the proposed OEO-based RF photonic front-end for both the up-converting process and OEO loop, without the impact on the oscillation of the OEO.

Then a stable LO is achieved for mixing. The mixing signal of the LO and RF input signal is processed by the narrow bandwidth band-pass filter (TBPF2) and down-converted to electric-domain by the PD2 to achieve the RF output signal. The direct-current (DC)-block and low-pass filter are introduced to remove the DC-component and high-frequency component such as the LO and RF signal. The frequency of the LO can be tuned to achieve a large frequency range which is determined by the bandwidth tunability of TBPF1 and limited by the response bandwidth of the PM and PD1 [15

15. X. Xie, C. Zhang, T. Sun, P. Guo, X. Zhu, L. Zhu, W. Hu, and Z. Chen, “Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter,” Opt. Lett. 38(5), 655–657 (2013). [CrossRef] [PubMed]

].

3. Experimental setup and results

In the experiment, a CW with 1550.024 nm wavelength, 1 kHz line-width and 23.2 mW optical power is sent into the PM with a modulated bandwidth and half-wave voltage of separately 40 GHz and 7V and modulated by the combination of the two-tone signal and the OEO based LO. A wave-shaper (Finisar 1000s) with a tunable bandwidth is utilized as the TBPF1 and the PD1 with a bandwidth of 10 GHz is applied to detecting and down-converting the signal. Two-stage PAs are used to make the gain of the OEO based LO loop larger than 1 to obtain and keep the LO.

The tunability of the LO with 3 different frequencies is measured by tuning the bandwidth of the TBPF1 as shown in Fig. 3(a).
Fig. 3 (a) The electric spectrum of the OEO-based LO (b) the phase noise of the LO at frequency of 5.5 GHz, 6.128 GHz and 7.227 GHz.
The smallest bandwidth (Bwmin) of TBPF1 and the bandwidth of the PD are all 10 GHz, so in this experiment limited by the device, the LO frequency can be not lower than Bwmin/2 = 5 GHz and larger than 10 GHz. A single mode fiber with a length of about 200 meters is introduced to the LO loop to obtain the delay and lower the phase noise of the LO. The phase noise picture is shown in Fig. 3(b) and the phase noise (measured by the Agilent E5052B) at an offset of 10 kHz relative to the center frequency of the oscillation of the OEO are all below −102.5 dBc/Hz.

Fig. 5 The operation frequency range of the RF input signal at different input power in the proposed RF photonic front-end.
For application in reality, the separation between the received RF signal and the LO can’t be too small and the input power of the RF signal is also limited. Figure 5 shows the application condition on the separation △f between the RF signal and the LO, and the input RF power. As can be seen from Fig. 5, there is a step response of the LO output power relative to the separation at different input RF power. At a certain input RF power, the LO output power is not changed as the separation is decreased, until the critical point, the LO output is vanished. As the RF input power increases, the critical point of the separation would be enlarged as show in the Fig. 5. So there should be a tradeoff between the RF input power and the separation. But fortunately, the separation can be tuned by tuning the frequency of the LO and the RF input power received by the antenna is not so large. The influence of the low energy signal received by the antenna on the LO can be negligible.

4. Conclusion

In this paper, a simple broadband and tunable RF photonic front-end integrating an OEO-based LO has been proposed and experimentally demonstrated, with only one PM for both the up-converting of the RF input signal and also the LO loop. SOI-based narrow bandwidth filter with a bandwidth of about 1.536 GHz is utilized for signal processing in this front-end. The dynamic range of the proposed RF photonic front-end at frequency of about 7.02 GHz is measured to be 88.6 dB-Hz2/3 and the processing range of the proposed photonic front-end can cover from X- to Ka-band which is only decided by the processing ability of the signal processor and the frequency range of the LO. The application condition of the front-end has also been discussed, that there would be a tradeoff between the input power of the RF signal and the separation between the RF signal and LO. The proposed simple design of the RF photonic front-end integrating with the LO loop would be a potential setup for monolithic integration of the front-end.

Acknowledgments

This work was partially supported by National Program on Key Basic Research Project (973) under Contract 2012CB315703, NSFC under Contract 61120106001, 61271134, 61090391 and the Program for New Century Excellent Talents in University (NCET-10-0520).

References and links

1.

J. Capmany and D. Novak, “Microwave photonics combines two worlds,” Nat. Photonics 1(6), 319–330 (2007). [CrossRef]

2.

J. Yao, “Microwave photonics,” J. Lightwave Technol. 27(3), 314–335 (2009). [CrossRef]

3.

R. C. J. Hsu, A. Ayazi, B. Houshmand, and B. Jalali, “All-dielectric photonic-assisted radio front-end technology,” Nat. Photonics 1(9), 535–538 (2007). [CrossRef]

4.

R. B. Waterhouse and D. Novak, “Integrated Antenna/Electro-Optic Modulator for RF Photonic Front-Ends,” Proceedings of 2011 International Microwave Symposium, Baltimore, MD, June 2011. [CrossRef]

5.

J. Chou, J. A. Conway, G. A. Sefler, G. C. Valley, and B. Jalali, “Photonic bandwidth compression front end for digital oscilloscopes,” J. Lightwave Technol. 27(22), 5073–5077 (2009). [CrossRef]

6.

V. S. Ilchenko, A. A. Savchenkov, J. Byrd, A. B. Matsko, D. Seidel, and L. Maleki, “Photonic Front-end for Millimeter Wave Applications,” Proc. of 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 1–2, November 2008.

7.

A. B. Matsko, V. S. Ilchenko, P. Koonath, J. Byrd, A. A. Savchenkov, D. Seidel, and L. Maleki, “RF photonic receiver front-end based on crystalline whispering gallery mode resonators,” Proc. of 2009 IEEE Radar Conference, 1–6, May 2009. [CrossRef]

8.

T. R. Clark and R. Waterhouse, “Photonics for RF Front Ends,” IEEE Microw. Mag. 12(3), 87–95 (2011). [CrossRef]

9.

S. A. Pappert and B. Krantz, “RF photonics for radar front-ends,” in Proc. IEEE Radar Conf., Boston, MA, 965–970 (2007).

10.

X. Guan and A. Hajimiri, “A 24-GHz CMOS Front-End,” IEEE J. Solid-State Circuits 39(2), 368–373 (2004). [CrossRef]

11.

R. T. Logan Jr and E. Gertel, “Millimeter-wave photonic downconvertors: Theory and demonstrations,” Proc. SPIE 2560, 58–69 (1995). [CrossRef]

12.

A. Agarwal, T. Banwell, and T. K. Woodward, “Optically filtered microwave photonic links for RF signal processing applications,” J. Lightwave Technol. 29(16), 2394–2401 (2011). [CrossRef]

13.

B. M. Haas and T. E. Murphy, “Linearized downconverting microwave photonic link using dual-wavelength phase modulation and optical filtering,” IEEE Photon. J. 3(1), 1–12 (2011). [CrossRef]

14.

L. Maleki, “Sources: The optoelectronic oscillator,” Nat. Photonics 5(12), 728–730 (2011). [CrossRef]

15.

X. Xie, C. Zhang, T. Sun, P. Guo, X. Zhu, L. Zhu, W. Hu, and Z. Chen, “Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter,” Opt. Lett. 38(5), 655–657 (2013). [CrossRef] [PubMed]

16.

D. Zhu, S. Pan, S. Cai, and D. Ben, “High-Performance Photonic Microwave Downconverter Based on a Frequency-Doubling Optoelectronic Oscillator,” J. Lightwave Technol. 30(18), 3036–3042 (2012). [CrossRef]

17.

W. Shieh, S. X. Yao, G. Lutes, and L. Maleki, “Microwave signal mixing by using a fiber-based optoelectronic oscillator for wavelength division multiplexed systems,” in Opt. Fiber Commun. Conf. Tech. Dig., 358–359 (1997). [CrossRef]

18.

H. Yu, M. Chen, P. Li, S. Yang, H. Chen, and S. Xie, “Silicon-on-insulator narrow-passband filter based on cascaded MZIs incorporating enhanced FSR for downconverting analog photonic links,” Opt. Express 21(6), 6749–6755 (2013). [CrossRef] [PubMed]

19.

X. Zhang, B. Lee, C. Y. Lin, A. X. Wang, A. Hosseini, and R. T. Chen, “Highly Linear Broadband Optical Modulator Based on Electro-Optic Polymer,” IEEE Photon. J. 4(6), 2214–2228 (2012). [CrossRef]

OCIS Codes
(070.1170) Fourier optics and signal processing : Analog optical signal processing
(230.3120) Optical devices : Integrated optics devices
(060.5625) Fiber optics and optical communications : Radio frequency photonics

ToC Category:
Integrated Optics

History
Original Manuscript: November 21, 2013
Revised Manuscript: January 28, 2014
Manuscript Accepted: February 7, 2014
Published: February 12, 2014

Citation
H. Yu, M. Chen, H. Gao, S. Yang, H. Chen, and S. Xie, "RF photonic front-end integrating with local oscillator loop," Opt. Express 22, 3918-3923 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-4-3918


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References

  1. J. Capmany, D. Novak, “Microwave photonics combines two worlds,” Nat. Photonics 1(6), 319–330 (2007). [CrossRef]
  2. J. Yao, “Microwave photonics,” J. Lightwave Technol. 27(3), 314–335 (2009). [CrossRef]
  3. R. C. J. Hsu, A. Ayazi, B. Houshmand, B. Jalali, “All-dielectric photonic-assisted radio front-end technology,” Nat. Photonics 1(9), 535–538 (2007). [CrossRef]
  4. R. B. Waterhouse, D. Novak, “Integrated Antenna/Electro-Optic Modulator for RF Photonic Front-Ends,” Proceedings of 2011 International Microwave Symposium, Baltimore, MD, June 2011. [CrossRef]
  5. J. Chou, J. A. Conway, G. A. Sefler, G. C. Valley, B. Jalali, “Photonic bandwidth compression front end for digital oscilloscopes,” J. Lightwave Technol. 27(22), 5073–5077 (2009). [CrossRef]
  6. V. S. Ilchenko, A. A. Savchenkov, J. Byrd, A. B. Matsko, D. Seidel, and L. Maleki, “Photonic Front-end for Millimeter Wave Applications,” Proc. of 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 1–2, November 2008.
  7. A. B. Matsko, V. S. Ilchenko, P. Koonath, J. Byrd, A. A. Savchenkov, D. Seidel, L. Maleki, “RF photonic receiver front-end based on crystalline whispering gallery mode resonators,” Proc. of 2009 IEEE Radar Conference, 1–6, May 2009. [CrossRef]
  8. T. R. Clark, R. Waterhouse, “Photonics for RF Front Ends,” IEEE Microw. Mag. 12(3), 87–95 (2011). [CrossRef]
  9. S. A. Pappert, B. Krantz, “RF photonics for radar front-ends,” in Proc. IEEE Radar Conf., Boston, MA, 965–970 (2007).
  10. X. Guan, A. Hajimiri, “A 24-GHz CMOS Front-End,” IEEE J. Solid-State Circuits 39(2), 368–373 (2004). [CrossRef]
  11. R. T. Logan, E. Gertel, “Millimeter-wave photonic downconvertors: Theory and demonstrations,” Proc. SPIE 2560, 58–69 (1995). [CrossRef]
  12. A. Agarwal, T. Banwell, T. K. Woodward, “Optically filtered microwave photonic links for RF signal processing applications,” J. Lightwave Technol. 29(16), 2394–2401 (2011). [CrossRef]
  13. B. M. Haas, T. E. Murphy, “Linearized downconverting microwave photonic link using dual-wavelength phase modulation and optical filtering,” IEEE Photon. J. 3(1), 1–12 (2011). [CrossRef]
  14. L. Maleki, “Sources: The optoelectronic oscillator,” Nat. Photonics 5(12), 728–730 (2011). [CrossRef]
  15. X. Xie, C. Zhang, T. Sun, P. Guo, X. Zhu, L. Zhu, W. Hu, Z. Chen, “Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter,” Opt. Lett. 38(5), 655–657 (2013). [CrossRef] [PubMed]
  16. D. Zhu, S. Pan, S. Cai, D. Ben, “High-Performance Photonic Microwave Downconverter Based on a Frequency-Doubling Optoelectronic Oscillator,” J. Lightwave Technol. 30(18), 3036–3042 (2012). [CrossRef]
  17. W. Shieh, S. X. Yao, G. Lutes, L. Maleki, “Microwave signal mixing by using a fiber-based optoelectronic oscillator for wavelength division multiplexed systems,” in Opt. Fiber Commun. Conf. Tech. Dig., 358–359 (1997). [CrossRef]
  18. H. Yu, M. Chen, P. Li, S. Yang, H. Chen, S. Xie, “Silicon-on-insulator narrow-passband filter based on cascaded MZIs incorporating enhanced FSR for downconverting analog photonic links,” Opt. Express 21(6), 6749–6755 (2013). [CrossRef] [PubMed]
  19. X. Zhang, B. Lee, C. Y. Lin, A. X. Wang, A. Hosseini, R. T. Chen, “Highly Linear Broadband Optical Modulator Based on Electro-Optic Polymer,” IEEE Photon. J. 4(6), 2214–2228 (2012). [CrossRef]

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