外文翻译-数字频率计的设计.doc

外文资料原文 The Development of Frequency Meter The frequency meter is mainly composed of four parts: the time base (T) counting circuit, input circuit, display circuit and control circuit.In the process of a measuring cycle,the periodic signal to be measured in the input circuit after amplification, plastic, differential operation form a specific period of narrow pulse, an input to the main gate. The main door of another input too base circuit to produce the gate circuit. During the gate opening the main door of a particular period of narrow pulse can through the main door, to counter to count, counter display circuit is used to display the measured signal frequency values, internal control circuit is used to complete a variety of functions between the switch and implement measurement setup. The application range of the frequency meter: in the traditional electronic measuring instrument, the oscilloscope in the low measurement precision of frequency measurement, error is bigger. Spectrometer can accurate measurement and display of the measured signal frequency spectrum, but the measurement speed is slow, cannot real-time fast tracking to the change of the measured signal frequency. It is because of frequency meter can fast accurate to catch the change of the measured signal frequency, therefore, frequency meter has very extensive application scope. Electronic counter is a basic measurement instruments, so far has a history of more than 30 years. Early, designers goal is mainly to expand measuring range, plus improve the measurement accuracy, stability, etc., these are people measure the technological level of electronic calculators, decided to electronic counter the main basis of the price. At present the basic technique perfected, mature. Application of modern technology can be easily expanded electronic counter measure frequency limit to microwave frequencies. With the development of science and technology, the user also puts forward new requirements for electronic counter. For low-grade products requires the use of convenient operation, wide range (enough), high reliability, low price. For the upscale product, insist on a high resolution, high accuracy, high stability, high measuring speed; , besides the functions of general counter usually also have the function of data processing and statistical analysis, time-domain analysis function, etc., or contains other functions such as voltage measurement. Some of these requirements have been implemented or partial implementation, but to truly achieve these goals, for the manufacturers, have a lot of work to do, rather than on the surface seems to be the end of the development.containing unknown frequency component, frequency fixed or change or superposition of interference, pure, and so on. In order to correctly measure the different types of signals, must learn to test signal characteristics and performance of frequency measurement instruments. Microwave counter usually use the type spectrum analyzer of frequency division or mixing circuit, it also contains multiple time benchmark, synthesizer, intermediate frequency amplifier and so on. While counting all the microwave counter is used to complete the task, but manufacturers have their own a set of complex counter design, make different models of performance and the price will be different, so you need to choose carefully according to its additional features or price.The sensitivity and accuracy requirements To measure microwave frequency, frequency meter must have enough sensitivity in the measurement frequency point, because some instruments of actual performance must be better than the description to the index, so that when measuring the critical signals might have more flexibility. For example, microwave counter instruction given in 20 GHZ sensitivity for 25 DBM, so completely can be successfully used to measure the frequency point - 30 DBM signal. And, of course, if the rated highest frequency counter for 18 GHZ, so due to counter circuit can not work in more than 18 GHZ, you cant even use it on 20 GHZ 0 DBM signal measurement. Therefore, if you want to do precise measurement, a need to ensure that the frequency of the measured signal and amplitude in the range of indicators of a measuring instrument. Manual test performance index is given on "accuracy" and "resolution" of a measuring instrument. Accuracy indicators show that instrument readings near the extent of the actual signal frequency; Index shows how small changes in frequency and resolution may be displayed on the instrument. If need to have the 1 hz resolution, 15 GHZ instrument must show at least 11 digits. High resolution can quickly detect smaller drift value and unstable, but the reading is not fully represent the accuracy of the instrument.The accuracy of the measuring instrument of choice The frequency of the instrument measurement accuracy depends on the time base. Most of the instru。