JP3016253B2 - Network analyzer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to network analyzers, and more particularly to an improved method for measuring and displaying screen characteristic parameters of filters, such as bandpass filters, using the same. And means.

[Technical background of the invention and its problems]

When designing and evaluating a filter such as a band-pass filter, characteristic parameters such as a pass band width, a center frequency, and a Q (quality factor) are used as basic items thereof.

In a conventional network analyzer, these characteristic parameters are measured by a user executing a width function provided in the analyzer with a single key operation or command, and the result is displayed on a display. Will be displayed.

Hereinafter, the window function will be described with reference to FIG.

A device under test (DUT) such as a band-pass filter is frequency-swept within a predetermined frequency range, for example, with a predetermined step frequency width by a measurement signal from a network analyzer. After the output of the device under test corresponding to each frequency is converted to a digital signal, it is sequentially stored as gain measurement data or the like in a memory provided inside the analyzer. The measurement data stored in the memory is used by the display control device to draw a trace as shown in FIG. 3 on a display screen. This screen shows the transmission characteristics of the device under test when the horizontal axis represents frequency and the vertical axis represents gain.

When obtaining the above-mentioned characteristic parameters from this trace, first, the marker 1 is arranged at the maximum gain point on the trace by executing the marker / maximum function. Next, the widow function is executed, and as shown in FIG. 3, three markers, that is, a predetermined amount, for example, 3 dB (which can be set by a user and is called a widows value (width value)) are dropped from the maximum point. Markers 3 and 4 indicating the point that has been set, and Marker 2 indicating the frequency intermediate point between marker 3 and marker 4 are arranged along the trace. At this time, characteristic parameters such as the pass band width, center frequency, and Q of the device under measurement are calculated from the frequency information held by these markers, and displayed on a part of the screen, for example, at the upper right of the screen. The arrangement of these markers and the calculation of the characteristic parameters are performed by searching the aforementioned memory.

However, in the case of a band-pass filter or the like having a relatively large ripple in the pass band, a desired characteristic parameter may not be able to be measured by executing the Wids function once. In this case, conventionally, as shown in FIG. 4, first, the marker 1 is arranged at the maximum point on the trace displayed on the screen using the marker / maximum function, and then the Wids function is executed. For example, markers 3 and 4 are placed at the left and right points that are close to 3 dB lower than this and that are closest to marker 1,
Further, the frequency intermediate point marker 2 between the marker 3 and the marker 4 is arranged (solid line marker in the figure). After that, the activate marker key is pressed to activate the marker 3 (Δ of the marker mark becomes ▽, indicating that the marker can be moved by operating the step key or the like).
To, running target left (target left) function, 3 dB in the marker 3 on the immediately left side (target value is referred to as a (target value)) is moved to the drop point L _1. The target left function running desired number, placing the marker 3 on the leftmost target value point L _4. Similarly, by running the target light (target. Right) function desired number, placing the marker 4 to the target value point R ₄ in its rightmost. At this time, a desired characteristic parameter value is displayed on a part of the screen. The arrangement of these markers is performed by searching the memory as described above. The execution of each function is performed by one key operation or command input.

In this way, the desired characteristic parameter values of the band-pass filter having a relatively large ripple in the pass band are displayed on the screen, but these operations are very troublesome and time-consuming. .

[Object of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and means for easily and quickly measuring and displaying a characteristic parameter of a filter having a relatively large ripple in a band.

[Summary of the Invention]

According to one embodiment of the present invention, a search out function capable of simultaneously executing the above-described target left function and target right function and the number of times the search out function has been executed are stored. A new counter is added to keep it. First, the marker / maximum function and the widows function are sequentially executed to arrange the four markers as described above, and then the search-out function is repeatedly executed to identify the two markers at the predetermined target value points. It is arranged on the left and right sides. At this time, the number of repetitions of the search-out function is stored in a counter provided in the apparatus. Thereafter, for each sweep, the search-out function is automatically executed the number of times stored in the counter after executing the marker / maximum function, and a desired characteristic parameter value is displayed on the screen. The data in the counter is reset when the widow function is turned off.

(Example of the invention)

Desired characteristic parameters such as a pass band width, a center frequency, and Q are obtained as follows.

First, four markers (solid line markers) are arranged as shown in FIG. 4 by sequentially executing the conventional marker / maximum function and widows function. The markers 1 and 2 indicate the maximum point and the center frequency, respectively, and the markers 3 and 4 indicate a point that has dropped by a predetermined amount from the maximum point, in this case, a point that has dropped 3 dB, that is, a Wids value point. This drop amount can be freely set by the user.

Next, the search-out function is repeatedly executed to place the markers 3 and 4 on the leftmost and rightmost sides, respectively. The search-out function is newly provided to simultaneously execute the conventional target left function and target right function. When the search-out function is executed, the marker 3 and the marker 4 are simultaneously moved to the target value (3 dB, which is equal to the Wids value) immediately on the left and right sides thereof. When the search-out function is executed several times to move the markers 3 and 4 to the respective ends,
If either marker reaches the end first, that marker does not move any further outward, only the other marker moves. When the other marker reaches its end,
The execution of the search-out function is stopped. At this time, the counter 11 provided inside the network analyzer shown in FIG. The number of times is stored.
In the example of FIG. 4, 4 is stored in the counter 11. Further, the marker 2 is arranged at a frequency intermediate point between the marker 3 and the marker 4.

The markers 3 and 4 need not always be arranged at both ends,
In this case, a value smaller than 4 is stored in the counter 11.

The execution of each of the above functions is performed by one key operation or command input.

Thereafter, every time a sweep is performed on the screen, the search-out function is automatically executed by the number of times indicated by the data stored in the counter after executing the marker / maximum function, as shown in the flowchart of FIG. The desired characteristic parameter value is displayed on the display. The data in the counter is reset when the widow function is turned off.

In order to arrange the markers 3 and 4 at both ends, instead of providing the counter 11, it is possible to search the memory 13 storing the measurement data for each sweep and find the outermost point having a predetermined target value. good.

Although the above description has been made with reference to bandpass filters, the present invention can be similarly applied to other bandpass filters, bandpass filters, high-pass filters, and the like.

〔The invention's effect〕

As described above, by using the present invention, the characteristic parameters of a filter having a relatively large ripple in a band can be easily and quickly set without repeating a troublesome and time-consuming series of operations. You can ask.

[Brief description of the drawings]

FIG. 1 is a schematic functional block diagram showing one embodiment of the present invention. FIG. 2 is a partial flowchart showing an embodiment of the present invention. FIG. 3 is a diagram for explaining a conventional widows function. FIG. 4 is a diagram for explaining a search-out function according to the present invention. 11: counter, 12: CPU 13: memory, 14: display controller 15: display

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 27/28 G01R 23/16 G01R 13/30

Claims (1)

(57) [Claims] A memory for storing data, a display device,
A control device for displaying a trace in rectangular coordinates on the display device using the data stored in the memory, and a key input device connected to the control device; Means for initially arranging markers at two predetermined points on the trace having the same value V in two axial directions; and placing the markers on the trace in opposite directions along a first axis of the coordinates. Means for executing, by one manual key operation, a search-out function for simultaneously moving to the next point having V;
A counter that counts the number of times the out function has been performed and stores a count value when one of the markers has finally reached the last point on the trace having the value V; Means for automatically executing the search-out function a number of times based on the count value stored in the counter, and relocating the two markers to positions on the trace. .