| 1. |
- Fu, Hongyan, et al.
(författare)
-
Tunable all-optical microwave notch filter with a negative tap based on a semiconductor optical amplifier and a dispersive medium
- 2009
-
Ingår i: Optics and Laser Technology. - : Elsevier BV. - 0030-3992 .- 1879-2545. ; 41:3, s. 213-216
-
Tidskriftsartikel (refereegranskat)abstract
- A tunable all-optical microwave notch filter with a negative tap based on a semiconductor optical amplifier and a dispersive medium is demonstrated. A negative tap is realized through the cross gain modulation in the semiconductor optical amplifier. The free spectrum range of the notch filter can be tuned by tuning the wavelength of one of the two laser sources. The influence of the amplitude mismatch of the two lasers on the performance of the filter is analyzed. The present notch filter is easy to implement and cost-effective.
|
|
| 2. |
- Ye, Chenhui, et al.
(författare)
-
All-Optical Approach to Microwave Frequency Measurement With Large Spectral Range and High Accuracy
- 2012
-
Ingår i: IEEE Photonics Technology Letters. - : IEEE. - 1041-1135 .- 1941-0174. ; 24:7, s. 614-616
-
Tidskriftsartikel (refereegranskat)abstract
- An all-optical approach for microwave frequency (MWF) measurement with a low-speed oscilloscope is proposed and experimentally demonstrated. In this scheme, an optical filter with a single and ultranarrow passband, together with a tunable laser and a low-speed photodiode is utilized to calculate the MWF by measuring the time delay between the sweeping optical carrier and its upper/lower sideband passing through the filter. Single-frequency and multifrequency measurements are experimentally demonstrated. The measurement recognition, accuracy, and resolution are below 0.1, 0.09, and 0.2 GHz, respectively. This proposed scheme can be easily upgraded to higher frequencies using a modulator with higher bandwidth proportional to the desired measurement range.
|
|
| 3. |
- Ye, Chenhui, et al.
(författare)
-
An All-Optical Transformer From Differential NRZ Data to Ultra-Wideband Pulse Stream
- 2011
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 23:9, s. 579-581
-
Tidskriftsartikel (refereegranskat)abstract
- We propose and experimentally demonstrate a compact and cost-effective scheme based on a fiber Sagnac structure to realize real time conversion from differential nonreturn-to-zero (NRZ) data to ultra-wideband (UWB) pulse stream. The proposed conversion system for the UWB signal generation consists of a single-wavelength laser, a phase modulator, several polarization controllers, and optical couplers. Due to the optical interference between the two phase-modulated light waves with slight phase difference in the Sagnac loop, two sharp optical pulses with opposite polarities are obtained. With proper time delay, a UWB monocycle pulse stream is generated from the original differential NRZ data. Our proposed method gives a reliable, easy, and low-cost transformer from differential NRZ signal to UWB pulse stream, and no high-speed arbitrary waveform generator (AWG) is required in this all-optical transformer.
|
|
| 4. |
- Zhang, Shuai, et al.
(författare)
-
MIMO reference antennas for OTA applications
- 2013
-
Ingår i: 2013 7th European Conference on Antennas and Propagation, EuCAP 2013. - New York : IEEE. - 9788890701832 ; , s. 2556-2557, s. 2243-2244
-
Konferensbidrag (refereegranskat)abstract
- In this paper, MIMO reference antennas with different correlation coefficients are proposed for Over-The-Air (OTA) applications. The correlation can be simply controlled through a slot etched on a dual-feed PIFA with the similar total efficiency. Three kinds of situations are investigated with the proposed method: high correlation (HC), mid correlation (MC), and low correlation (LC). In order to verify the introduced idea, the measurements of correlations and efficiencies are carried out in a reverberation chamber. The simulation and measurement agree well with each other.
|
|
| 5. |
- Zhang, Shuai, et al.
(författare)
-
MIMO Reference Antennas with Controllable Correlations and Total Efficiencies
- 2014
-
Ingår i: Progress In Electromagnetics Research. - 1070-4698 .- 1559-8985. ; 145, s. 115-121
-
Tidskriftsartikel (refereegranskat)abstract
- MIMO reference antennas are proposed for over the air (OTA) measurement applications. The reference antennas could get rid of feeding cable interference and control envelope correlation coefficients (ECC) continuously by only changing the length of an etched slot on a dual-feed PIFA. If only the ECC is investigated, the MIMO reference antenna is optimized to have a small variation of total efficiency from 70% to 50% when the ECC increases from 0.1 to 0.88. The prototypes are fabricated and measured in a scattered field chamber (SFC). Measurements agree well with the simulations. If the MIMO performance is studied, the MIMO reference antenna is proposed to own a large variation of total efficiencies from 90% to 47% while the ECC increases from 0 to 0.98. The bandwidth of the proposed reference antennas depend on the size of the antennas. This method is valid for all the frequencies.
|
|
| 6. |
- Zhu, Kun, et al.
(författare)
-
A Simple and Tunable Single-Bandpass Microwave Photonic Filter of Adjustable Shape
- 2008
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 20:21-24, s. 1917-1919
-
Tidskriftsartikel (refereegranskat)abstract
- A simple and tunable single-hand pass microwave photonic filter of adjustable shape is proposed and experimentally demonstrated. The filter is based on multiple sources (spectrum-sliced by a Mach-Zehnder interferometer) and two cascaded incoherent optical structures, namely, a dispersion medium of 50-km single-mode fiber and a fiber ring delay line. In the experimental range from 1.0 to 3.8 GHz, a discretely tunable single-hand pass filter with a high Q-factor or a flat-top response is achieved by carefully matching the transfer functions of the two individual optical structures.
|
|
| 7. |
- Zhu, Kun, et al.
(författare)
-
All-optical coherence-free microwave filter with switchable passbands based on phase and intensity hybrid modulation
- 2011
-
Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 284:1, s. 140-143
-
Tidskriftsartikel (refereegranskat)abstract
- A simple all-optical coherence-free microwave notch filter is proposed and experimentally demonstrated. The filter with switchable passbands is based on a single-wavelength optical source and phase-intensity hybrid modulation scheme. The DC bias voltage applied to the Mach-Zehnder intensity modulator can be adjusted to switch signs of the tap coefficients, which affect the baseband response. Both lowpass and bandpass filtering responses are observed in the experiment and agree well with the simulated results.
|
|
