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1981 Vol. 3, No. 4
Display Method:
1981, 3(4): 201-212.
Abstract:
In this paper two equipments for Mi-Yun meter-wave aperture synthesis radiote-lescope are described. These two equipments are used for data acquisition and handling with on-line computer, NOVA-3/D.The Mi-Yun aperture synthesis system consists of an E-W array ,giving 192 simultaneous signal pairs of the form R=W cos, I=W sin per 10 sconds. Where W is the fringe amplitude and=(2d/) cos sinHA, the phase. (d-the interferometer spacing,--the wave length,--th declination and HA--the hour angle of field center.)The first equipment is the data collection system which performs the follwing function: 1 In every 10 msec generates a value,0=A sinHA, where A is thecarefully chosen constant, HA is the hour angle of the field center. 2. In the same 10 msec generatesk, where k=k0(k=3, 4,,194), accurate to 2.3.Converts each of the 192 signal pairs into parameters Wk andk; perform the fringe stopping by substracting k from eachk, giving a new signal set of the form Wk cos(k-k) and Wk sin(k-k); accumulate for 10 seconds and send the output data to the on-line computer. The function0(t)=A sinHA is generated by the digital differential analyzer (DDA) developed by one of the authors (C.K.Kwong).AM-2901 has been used for the CPU of our system. Block diagram of the whole system is shown in Fig.4. Fig.5 is the flow chart of the microprogram. The system can work either with mean time or sidereal time. The other equipment is the two-dimensional direct fourier transform (DFT) hardware based on the previous work of R.H.Frater, adapted for the data handling of the Mi-Yun system. The observation will be carried out in 12 hours, filling up 2160 equally spaced hourangles with 192 spacings each, thus 2160192 grid values in u-v plane (as defined in Fig.7(a)). Fourier transform of this u-v distribution is to be performed by the DFT hardware to give a radio sky map on a 256256 grids (Fig.7(b)). The performance can be completed in less than 6 minutes. In the construction, the principle and scheme developed by Frater has been used with some imnor modifications, such as using the hardware multiplier (MPY-12 AJ) in place of Log. Table, increasing the accuracy with interpolations, etc.Fig.8 is the block diagram of the DFT hardware. As a laboratory test, a set of signals simulating a point source located at the field center was sent to the DFT hardware. The result of the fourier transform is shown in Fig.9 they agree well with the estimation. The two equipments have been completed now and have worked normally for several months.
In this paper two equipments for Mi-Yun meter-wave aperture synthesis radiote-lescope are described. These two equipments are used for data acquisition and handling with on-line computer, NOVA-3/D.The Mi-Yun aperture synthesis system consists of an E-W array ,giving 192 simultaneous signal pairs of the form R=W cos, I=W sin per 10 sconds. Where W is the fringe amplitude and=(2d/) cos sinHA, the phase. (d-the interferometer spacing,--the wave length,--th declination and HA--the hour angle of field center.)The first equipment is the data collection system which performs the follwing function: 1 In every 10 msec generates a value,0=A sinHA, where A is thecarefully chosen constant, HA is the hour angle of the field center. 2. In the same 10 msec generatesk, where k=k0(k=3, 4,,194), accurate to 2.3.Converts each of the 192 signal pairs into parameters Wk andk; perform the fringe stopping by substracting k from eachk, giving a new signal set of the form Wk cos(k-k) and Wk sin(k-k); accumulate for 10 seconds and send the output data to the on-line computer. The function0(t)=A sinHA is generated by the digital differential analyzer (DDA) developed by one of the authors (C.K.Kwong).AM-2901 has been used for the CPU of our system. Block diagram of the whole system is shown in Fig.4. Fig.5 is the flow chart of the microprogram. The system can work either with mean time or sidereal time. The other equipment is the two-dimensional direct fourier transform (DFT) hardware based on the previous work of R.H.Frater, adapted for the data handling of the Mi-Yun system. The observation will be carried out in 12 hours, filling up 2160 equally spaced hourangles with 192 spacings each, thus 2160192 grid values in u-v plane (as defined in Fig.7(a)). Fourier transform of this u-v distribution is to be performed by the DFT hardware to give a radio sky map on a 256256 grids (Fig.7(b)). The performance can be completed in less than 6 minutes. In the construction, the principle and scheme developed by Frater has been used with some imnor modifications, such as using the hardware multiplier (MPY-12 AJ) in place of Log. Table, increasing the accuracy with interpolations, etc.Fig.8 is the block diagram of the DFT hardware. As a laboratory test, a set of signals simulating a point source located at the field center was sent to the DFT hardware. The result of the fourier transform is shown in Fig.9 they agree well with the estimation. The two equipments have been completed now and have worked normally for several months.
1981, 3(4): 213-221.
Abstract:
A high-speed high-accuracy partially-cascaded A/D converter is developed, which is used with the telescope for observing the solar magnetic field. The major techniques employed for realizing high speed and high accuracy are discussed, and some related factors are also considered.For this converter, the word length is 12bit, the resolution power is 1 mV, the relative accuracy less than 0.025%, and the rate is 100,000 sec-1 when a sampling hold circuit is cascaded in front of it.
A high-speed high-accuracy partially-cascaded A/D converter is developed, which is used with the telescope for observing the solar magnetic field. The major techniques employed for realizing high speed and high accuracy are discussed, and some related factors are also considered.For this converter, the word length is 12bit, the resolution power is 1 mV, the relative accuracy less than 0.025%, and the rate is 100,000 sec-1 when a sampling hold circuit is cascaded in front of it.
1981, 3(4): 222-226.
Abstract:
In the first part, the working equations of velocity tapered TWT are deduced theoretically. This paper presents a computer program for TWT with double velocity jump and describes the calculated results and comparison of them with experimental data. The comparison shows that they are rather close. Therefore this program can be used for the design and selection of the TWT with the double velocity jump.
In the first part, the working equations of velocity tapered TWT are deduced theoretically. This paper presents a computer program for TWT with double velocity jump and describes the calculated results and comparison of them with experimental data. The comparison shows that they are rather close. Therefore this program can be used for the design and selection of the TWT with the double velocity jump.
1981, 3(4): 227-236.
Abstract:
A new method that combines Monte-Carlo method with the numerical integration method used for computing electron trajectories in vacuum to calculate the electron collection efficiency of the anode (or dynode) of an electron optical system is presented. This method can simulate the whole process of electron motion in a system. Taking the microchannel plate photomultiplier as an example, the collection efficiency is calculated, the influences of the distributions of electron emitting angles and energies are studied, and the limitation and extension of this method are discussed.
A new method that combines Monte-Carlo method with the numerical integration method used for computing electron trajectories in vacuum to calculate the electron collection efficiency of the anode (or dynode) of an electron optical system is presented. This method can simulate the whole process of electron motion in a system. Taking the microchannel plate photomultiplier as an example, the collection efficiency is calculated, the influences of the distributions of electron emitting angles and energies are studied, and the limitation and extension of this method are discussed.
1981, 3(4): 237-248.
Abstract:
In this paper a model for calculation of heat transfer of the cathode assembly in vidicon has been given. Five cathode assemblies with different constructions have been calculated by computer. The calculated results prove the model is reasonable. In this paper, there are the following calculations: the temperatures at each part of the assembly; the heat radiation and conduction between different parts; the total power dissipation of the assembly and the influences of changing physical or geometrical parameters of the parts of the assembly on the totl power dissipation. Thi paper is helpfull to design a new cathode assembly.The design and experiment of the new cathode (Ba-Ni) assembly with small power dissipation is successful. The advantages of the new assembly is firm construction, easy assembling and quick heating (arriving at the operation temperature in a few seconds).
In this paper a model for calculation of heat transfer of the cathode assembly in vidicon has been given. Five cathode assemblies with different constructions have been calculated by computer. The calculated results prove the model is reasonable. In this paper, there are the following calculations: the temperatures at each part of the assembly; the heat radiation and conduction between different parts; the total power dissipation of the assembly and the influences of changing physical or geometrical parameters of the parts of the assembly on the totl power dissipation. Thi paper is helpfull to design a new cathode assembly.The design and experiment of the new cathode (Ba-Ni) assembly with small power dissipation is successful. The advantages of the new assembly is firm construction, easy assembling and quick heating (arriving at the operation temperature in a few seconds).
1981, 3(4): 249-253.
Abstract:
Starting from the view point of the coherent cyclotron radiation, we work out the phase condition of the Weibel instability gain mechanism and make a comparison with the phase condition of the cyclotron maser gain mechanism. Moreover, we propose a conceived slow wave cyclotron amplifier (SWCA) with a periodic rf structure.
Starting from the view point of the coherent cyclotron radiation, we work out the phase condition of the Weibel instability gain mechanism and make a comparison with the phase condition of the cyclotron maser gain mechanism. Moreover, we propose a conceived slow wave cyclotron amplifier (SWCA) with a periodic rf structure.
1981, 3(4): 254-258.
Abstract:
This article deals with the design of a 10,000 Chinese characters radio teletypewriter based on Zhi s Chinese characters coding method. The teletypewriter consists of a receiver and a transmitter. The former is more important, and it contains: (1) 10,000 Chinese characters geometric distribution structure; (2) 10,000 Chinese characters optional selection and typewriting method; (3) 5050-0000 code; (4) electronic calculation; (5) electronic calculation clock procedure; (6) 5050 code calculation circuit connection; (7) produce of 0000-5050 code. This teletypewriter adopts the direct character memory method, so no large scale high density memory elements are required. This teletypewriter not only can directly transmit Chinese characters but also can be connected to the national computer network to communicate with data centers. The data required can be typewritten in Chinese at the very moment as they are received.
This article deals with the design of a 10,000 Chinese characters radio teletypewriter based on Zhi s Chinese characters coding method. The teletypewriter consists of a receiver and a transmitter. The former is more important, and it contains: (1) 10,000 Chinese characters geometric distribution structure; (2) 10,000 Chinese characters optional selection and typewriting method; (3) 5050-0000 code; (4) electronic calculation; (5) electronic calculation clock procedure; (6) 5050 code calculation circuit connection; (7) produce of 0000-5050 code. This teletypewriter adopts the direct character memory method, so no large scale high density memory elements are required. This teletypewriter not only can directly transmit Chinese characters but also can be connected to the national computer network to communicate with data centers. The data required can be typewritten in Chinese at the very moment as they are received.
1981, 3(4): 259-260.
Abstract:
In this paper, A method for brazing molybdenum to molybdenus or other metals is discussed.
In this paper, A method for brazing molybdenum to molybdenus or other metals is discussed.
