LabVIEW related filter design and improvement

In the test field, and more extensive use of correlation detection method for filtering.

Use the related filter can easily be measured from a complex signal (including a useful signal, DC bias, random noise and harmonic frequency components, etc) to isolate a particular frequency signal. In the rapid development of digital technology, the relevant filter is also often use A/D Board on signal sampling, in a computer, a digital filter. This article has designed a realization method of the associated filter, this is the relevant analysis in test technology in a typical application. Figure l shows a block diagram of a typical.

　　

The National Instruments Labview is a United States company launched a way based on the "Graphic" integrated program development environment, is currently the only internationally compiled graphical programming language.

In a PC-based measurement and control software, Labview market penetration rate second only to the C + +/C language. Labview development environment with a wide range of benefits, from flowchart type programming, it does not require prior compilation syntax checking and debugging process, using the data pointer to its rich function, numerical analysis, signal processing and device drivers, and other functions. Application for filter design Lab-view, high efficiency, easy operation and on error precision adjustment in real time. Traditional instruments use Labview software approach to implementation, short development cycle, easy to maintain and upgrade, you can design a traditional instrument are incomparable virtual instrument, the "software is the instrument" — this is the essence of virtual instrumentation technology.

Simulation of autocorrelation filter

　　

2 virtual related filter design

2.1 front panel design

In the Labview environment developed application called VI (Virtual Instrument).

The core of the Labview VI is a human-computer interaction interface — the front panel, and the equivalent source function menu diagram programs — the back panel. Front panel is the program's interface, the interface on the control and display the quantity class object. On the front panel, control of simulated the instrument input device and the data provided to VI block diagram programs, such as switches, knobs, etc; and display the quantity is the simulation of the instrument's input device and displays the diagram programs or data, for example to display the waveform window, etc. The back panel also referred to as a code window or flowchart, VI graphical source, in the flowchart on VI programming, to control and manipulate the definition on the front panel input and output functions. Flowchart include front panel not but programming must be of the object, such as functions, structure and wires, etc.

Front panel as shown in Figure 2, consists of the following components: reference signal parameters settings, pending signal parameters settings, filter results, real-time display, and the original signal waveform diagram and waveform filtering results.

You can set a reference signal amplitude and frequency, you can also set 3 sine signal amplitude and phase frequency. After the program runs successfully from the filter display real-time results of district get filter frequency and amplitude and phase at the beginning, while in the waveform display area you can also get the corresponding waveform, make the results more visually reflected.

2.2 back panel design

Rear panel as shown in Figure 3.

Back panel controls and controls on the front panel, and add a program through the links, and to introduce measures such as the various signal be programmed implementation of autocorrelation filtering functionality. At the same time, through the front panel to set various parameters, successfully run the program, achieving the required objectives. In order to achieve this function, the author also tian added incentive signal source, filter Adder and multipliers such as calculator. After running the program, the test results can be achieved from a variety of frequency components of a signal in the extract the desired feature single frequency signal, equivalent to implement a filter. Since this filter idea is defined from the start of the related function, so become associated filter.

　　

Here, the author used simulation signal generator to simulate the signal to be measured, in reality the test signal usually consists of data acquisition card collection.

Input signal to be measured as 3 sine signal superposition, need to detect 20 Hz signal. This test VI realized correlation filtering process dynamic display, use a loop structure.

3 improved filter design

The implementation of the related filter, you can further improve, make the program easier.

Improved front panel shown in Figure 4, multi-channel signal set to display in a chart, more intuitive. At the same time increases the coarse and fine adjustment knob, appear to be more accurate. Improved front panel structure design is more compact, more reasonable.

　　

Improved rear panel as shown in Figure 5.

You can see, the filter with a signal average measurement VI replaces the original filter VI. This is because the related filter, filter function is to strike the test signal of the DC component, so that you can achieve the related filter. Take advantage of related functions, you can identify and extract the confusion in the noise signal, that is, the associated filter.

　　

In the rapid development of digital technology, the related filter often use A/D Board on signal sampling at the computer, a digital filter.

In Labview for associated filtering methods, are also relevant analysis in test technology in a typical application.

4 closing

Virtual instrument for more and more people are using and accepted, since the virtual instrument system faster

Simple and convenient, you can save your hardware resources. Through virtual filter design, virtual instruments have a deeper understanding and insight for the future for further study.