A Ka-band microwave photonic imaging radar demonstrator with 10.02 GHz-bandwidth is proposed and experimentally demonstrated. Continuous linear frequency waveform is optically generated in the transmitter and processed in the receiver. The range resolution of the demonstrator is tested to be 1.68 cm. Out-field tests while demonstrator works at inverse synthetic aperture radar (ISAR) and synthetic aperture radar (SAR) mode are carried out to image different targets.
The pseudo-color method which maps the sampled data to intuitive perception colors is a kind of powerful visualization way. And the all-around system of pseudo-color visualization, which includes the primary principle, model and HDL (Hardware Description Language) implementation for the thermal images, is expatiated on in the paper.
The thermal images whose signal is modulated as video reflect the temperature distribution of measured object, so they have the speciality of mass and real-time. The solution to the intractable problem is as follows: First, the reasonable system, i.e. the combining of global pseudo-color visualization and local special area accurate measure, must be adopted. Then, the HDL pseudo-color algorithms in SoC (System on Chip) carry out the system to ensure the real-time. Finally, the key HDL algorithms for direct gray levels connection coding, proportional gray levels map coding and enhanced gray levels map coding are presented, and its simulation results are shown. The pseudo-color visualization of thermal images implemented by HDL in the paper has effective application in the aspect of electric power equipment test and medical health diagnosis.
The infrared video image pseudo-color processing system, emphasizing on the algorithm and its implementation for measured object’s 2D temperature distribution using pseudo-color technology, is introduced in the paper. The data of measured object’s thermal image is the objective presentation of its surface temperature distribution, but the color has a close relationship with people’s subjective cognition. The so-called pseudo-color technology cross the bridge between subjectivity and objectivity, and represents the measured object’s temperature distribution in reason and at first hand. The algorithm of pseudo-color is based on the distance of IHS space. Thereby the definition of pseudo-color visual resolution is put forward. Both the software (which realize the map from the sample data to the color space) and the hardware (which carry out the conversion from the color space to palette by HDL) co-operate. Therefore the two levels map which is logic map and physical map respectively is presented. The system has been used abroad in failure diagnose of electric power devices, fire protection for lifesaving and even SARS detection in CHINA lately.
The magneto-optic current and electro-optic voltage sensing technologies were combined into a single phase unit which provides a new solution for combined current and voltage sensing and relaying applications. It senses voltage and current by making utilities of Pockels electro-optic effect of a BGO(Bi4Ge3O12) crystal and Faraday magneto-optic effect of a close-loop flint. The 220 kV high voltage is directly applied on the BGO crystal without capacitive dividers. This design permits true optical voltage measurement to be performed for the highest possible accuracy and stability. In the current sensor, a light beam circles around the current carrying conductor. The effect of the location movement of the conductor and external magnetic field are reduced. It has superior advantages of compact size, light- weight and better performance compared with conventional current and voltage transformers. Composite bushing consisting of a fiberglass tube support and silicone rubber that is filled with SF6 gas is employed for HV insulation. Connections between the Combined Optical Transformers in the substation and the metering and protecting unit in the control house are via optical fiber cable. The fundamental principal, system design and test result of this new 220 kV Combined Optical Transformer will be introduced in this paper.
This paper presents a new optical transformer which can measure high voltage and large current simultaneously. The measurement of voltage is based on the Pockels effect. A novel structure is posed to realize an optical voltage sensor which has better stability. The measured high voltage is directly applied on the optical voltage sensor without using any capacitive voltage divider. The measurement of current is based on the Faraday effect. A bulk glass closed- loop structure for optical current sensor is used. The optical voltage sensor is in the middle of the HV polymeric insulator which is full of SF6 gas, and the otpical current as immunity of electromagnetic interference, no saturation, no oil inside, wide band range, excellent transient characteristics and light weight etc. The principles, structures and testing results of the combined optical voltage and current transformer are described in this article.
Interferometric fiber optic gyroscope (IFOG) has been analyzed with autocontrol theory in this paper. An open-loop IFOG system is not able to restrain the bias drift, but a closed-loop IFOG system can do it very well using negative feedback in order to suppress zero drift. The result of our theoretic analysis and computer simulation indicate that the bias drift of a closed-loop system is smaller than an open- loop one.