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Spectrum analyzer's working principle and 0 replies,832 views

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Using a spectrum analyzer, what is the spectrum analyzer in the frequency domain analysis of signal icon tester. Graphically display the distribution of signal amplitude at the frequency that the frequency of X-axis, Y axis represents signal amplitude. Second, the principle: narrow band pass filter with the signal gating. Three main functions: display of the signal spectrum, amplitude and frequency. Can panoramic display, you can also select the bandwidth test. Fourth, measurement mechanisms: 1, the measured signal and the instrument baseline frequency, reference level for comparison. The essence of as many level measurement test, such as the carrier level, A / V, frequency response, C / N, CSO, CTB, HM, CM, and average power and other digital channels. 2, waveform analysis: The 107 options and the corresponding analysis software for the television line waveform analysis to test video index. Such as DG, **, CLDI, modulation depth, frequency and so on. Five steps: (a) hard keys, soft keys and rotary knob: This is the basic operation of the instrument means. 1, three large hard keys and a large knob: Big Knob features three large hard-key settings. Click the frequency of hard keys, the knob can fine-tune the instrument displays the center frequency; click Scan width hardware key, the knob can adjust the width of the frequency scanning equipment; click rate of the hard keys, the knob can adjust the signal amplitude. Turn the knob, the center frequency, sweep width (start, end frequency), and amplitude of the dB number displayed on the screen simultaneously. 2, soft key: the right of the screen, arranged in a vertical row of unmarked buttons, its function changes with the project, the right side of the screen corresponding to the key at the show what it is, what is key. 3, the other hard keys: Instrument status (INSTRUMNT STATE) control area has ten hard keys: RESET cleared, CANFIG configuration, CAL calibration, AUX CTRL auxiliary control, COPY print, MODE mode, SAVE storage, RECALL call, MEAS / USER Measurement / user-defined, SGL SWP signal scanning. Cursor (MARKER) District has four hard keys: MKR cursor, MKR cursor, RKR FCTN cursor function, PEAK SEARCH peak search. Control (CONTRL) area has six hard keys: SWEEP scans, BW the bandwidth, TRIG trigger, AUTO COVPLE automatic coupling, TRACE trace, DISPLAY display. Numeric keypad in a BKSP back, numeric keypad is a vertical row of the right recognized four ENTER key, but also the unit key. The three large knob above the window key hard key is: ON Open, NEXT next screen, ZOOM Zoom. With a large knob below the arrow keys of the two with the big knob to use as a STEP increase, down. (B) of the input and output interface: in the bottom panel along a row. TV IN indicators measuring the video signal input port; VOL INTEN is outside the control of a knob, adjust the built-in speaker volume and screen brightness; CAL OUT signal output self-test; 300Mhz 29dBmv standard signal output apparatus; PROBE PWR instrument probe power; IN 751M1.8G total input test signals. (C) Test Preparation: 1, restrictive protection: provides a maximum input RF level and cause permanent damage to the highest voltage: DC 25V, peak to peak AC 100V. 2 Preheat: testing must wait until the OVER COLD disappear. 3, since the school: for three months, or before an important measure to be from the school. 4, the system measurement configurations: configuration is to measure some parameters before input into the measurement, eliminating the need for each measurement parameter input once. Content: test items, the signal input (frequency or channel), display units, standard, noise measurement bandwidth and the sampling points, measuring CTB, CSO frequency point, the test line gating and so on. Configuration steps: Press the MODE button CABLE TV ANALYZER softkey Setup softkey, enter the set state. Configuration tuning details for the tune config: including frequency, channel, format, level units. Analyzer input input configuration: whether to raise pre-amplifier. Beats setup set the beat frequency, measured CTB, CSO of frequency (frequency offset CTB FRQ offset, CSO FRQ offset). GATING YES NO test whether the strobe line. C / N setup CNR settings: frequency (frequency offset C / N FRQ offset), bandwidth. (D) to read the results: 1, level of reading: The main use of reference level REF. Screen graphics apparatus of the most top horizontal line is the reference level line. The line indicates the level for the reference level, its value and units appear in the upper left corner of the screen. The value of the reference level can be changed: Press AMPLITUDE hard key, rotate the large knob can change the digital time displayed. Graphics in decibels per division dB / DIV upper left corner of the screen. 2, the frequency reads: graphics in the center frequency, start frequency, end frequency of three vertical bars, each representing the frequency of the number displayed in the bottom of the screen. Center frequency by the large rotary knob Frequency adjustment of the hard keys; starting and ending frequency of the hard keys from the Span large rotary knob to adjust (the actual is to change the scan width). 3, the cursor use: press the MKR button, the screen flashing cursor appears on the curve. Cursor level and frequency upper left corner of the screen. Free to move the cursor to move to what position to show where the frequency and level. 4, print, store 5, video test six tests commonly used in the test spectrum and channel test (Cable TV analysis): Press the MODE hard key, two soft keys displayed on the screen: Cable TV spectrum testing and analysis, press the corresponding softkey to into their own testing program. 1, spectrum test: three hard keys can be realized with the general analysis of a large knob. 2, the channel test: according to Cable TV ANALIZER disk soft key, then Road Test softkey screen, showing the test menu (a total of four pages), by channel selection CHINAL SELECT soft key, use the numeric keypad to enter the wish to identify the measured channel frequency ( analog TV channels for the image carrier frequency, the digital channel for the channel center frequency), you can test the channel. Menu as follows: LISTEN ON / OFF sound on / off EM DEV FM modulation depth VIEW INGRESS image crosstalk CARRIER LVL FRQ carrier level / frequency CARRIER / NOISE CNR CROSS MOD HUM hum modulation modulation crosstalk CSO / CTBDEPTH MOD modulation Depth SYSTEM FRQ RSP system frequency response IN CHNL FRQ RSP channel frequency response within the DIE GAIN DIF PHAZ differential gain, differential phase delay difference between light and color CLDI DIGITAL CH POEWER digital channel power FM RADIO seven FM radio, a few questions: 1, the measured C / N, CSO: The instrument provides two methods: Shutdown does not shut down modulation and modulation. Do not turn off modulation, the modulation in the measured signal channel to insert static test line to start the strobe function of the instrument, you can not interrupt the normal broadcast. CSO measured in Setup is set to be pre-beat location. Instrument in the set to look for beat frequency. 2, measured HUM, CM must turn off the modulation (to do with the carrier.) 3, the measured CTB must turn off the carrier. As CTB product concentrated in the near carrier frequency. Off after the carrier frequency, CTB, CSO product can see on the screen. What is the difference between CTB or CSO, to use their relationship with the input level to judge. 4, the following test items still need to test the presence of reverse-way into the line: do not turn off modulation measured C / N, CSO; measured CTB;
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