JP2014235150A - Test measurement apparatus, and image generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable one part of spectral display to be shown on an enlarged scale.SOLUTION: A test measurement apparatus 500 comprises a bitmap processor 510 that generates a first bitmap image from input test signals, a user interface 502 for specifying one part of the first bitmap image and a second bitmap processor 550 so configured as to generate a second bitmap image from the specified part of the first bitmap image. The second bitmap image is an enlarged image of the specified part of the first bitmap image, and the first and second bitmap images are so corrected as to be consistent on a time scale.

Description

  The present invention relates to a test and measurement apparatus and a method therefor, and more particularly to a test and measurement apparatus capable of frequency domain bitmap display having a zoom display function and an image generation method therefor.

  Real-time spectrum analyzers such as the RSA6100, RSA5100, and RSA3400 series available from Tektronix, Inc., Beaverton, Oregon, can trigger RF (radio frequency) signals for acquisition and analysis in real time. . These test and measurement equipment captures RF signals seamlessly (without interruption in time), so unlike traditional swept spectrum analyzers or vector analyzers, within a specific bandwidth (depending on the performance of each model) If so, there is no loss of data.

  FIG. 1 is a functional block diagram of a conventional real-time spectrum analyzer. Real-time spectrum analyzer 100 receives a radio frequency (RF) input signal and uses mixer 105, local oscillator (LO) 110 and filter 115 to down-convert the RF input signal (frequency conversion to a lower frequency). Then, an intermediate frequency (IF) signal is generated. An analog-to-digital converter (ADC) 120 digitizes the IF signal and generates a continuous stream of digital samples. The digital sample is input to the circular buffer 125 and also to the trigger detection unit 130. The trigger detector 130 processes the digital sample in real time and compares the processed sample with a trigger threshold specified by the user. When the processed digital sample violates the trigger threshold, the trigger detector 130 generates a trigger signal, which causes the acquisition memory 135 to store the digital sample held in the circular buffer 125. Here, “violate” means that the threshold is “exceeded” or “becomes smaller” than the threshold according to the parameter designated by the user. The stored digital samples are then analyzed later (post) by the post analysis processor 140, and the results are represented on the display device 145 or stored in a storage device (not shown).

  Tektronix real-time spectrum analyzers use a technique called “Digital Phosphor” or aka “DPX.RTM”. This realizes the effect of mimicking the light emission characteristics of the phosphor on the old CRT tube surface by digital processing while using a liquid crystal display or the like. A real-time spectrum analyzer capable of using DPX uses a continuous time processor 150 to process a continuous stream of digital samples from the ADC 120 in real time and display the results on the display device 145. FIG. 2 is a diagram for explaining the processing operation of the continuous-time processor shown in FIG. The continuous time processor 150 converts a continuous stream of digital samples into a spectrum 210 of thousands per second using a frequency conversion process 205 such as a fast Fourier transform (FFT), a chirp Z transform, and the like. These spectra 210 are then combined to form a data structure called a “bitmap database” 220.

  In one embodiment, each spectrum 210 is rasterized to generate a “raster spectrum” 215. A raster spectrum is composed of an array of cells arranged in successive rows and columns, each row representing a particular amplitude value and each column representing a particular frequency value. The value of each cell is either “1 (also called“ hit ”)” or “0 (drawn as a blank cell in the figure)”. At this time, “1” indicates that the input signal exists at a specific position in the frequency versus amplitude space during the measurement period of the raster spectrum, and “0” indicates that the input signal does not exist. Show. The values of the corresponding cells of the plurality of raster spectra 215 are summed together to form the bitmap database 220, and then the value of each cell in the bitmap database 220 is the total number of raster spectra 215. Since it is divided, the value of each cell indicates the value obtained by dividing the total number of hits during the measurement period by the total number of raster spectrums 215. That is, the value of each cell equivalently represents the percentage of time that the input signal occupied a particular position in the frequency versus amplitude space during the measurement period, which is expressed as “DPX density. Also called “RTM”.

  The multiple raster spectra 215 and bitmap database 220 are depicted in the figure as 10 rows and 11 columns for simplicity, but in actual embodiments, of course, the raster spectra 215 and bitmap database 220 may have hundreds of columns and rows. The bitmap database 220 is essentially a three-dimensional histogram, where the x-axis is frequency, the y-axis is amplitude, and the z-axis is density. The bitmap database 220 is displayed as an image called “bitmap” on the display device 145, and the density of each cell is represented by the gradation of the color of the pixel. Instead, the bitmap database 220 may be stored in a storage device (not shown). According to the DPX acquisition and display technology, conventional spectrum analyzers and vector signal analyzers can reveal details even for signals such as short-lived phenomena or rare events that are completely missed. For more information on DPX, see Tektronix's document "DPX.RTM. Acquisition Technology for Spectrum Analyzers Fundamentals (August 20, 2009, Document No. 37W-19638)". (Http://www.tek.com/) can be obtained by searching for Tektronix document number “37W-19638”.

  Based on this background, the advantages and novel features of the present invention will become apparent upon reading the following detailed description together with the claims and drawings.

Japanese Patent No. 3377391 JP-A-2005-331300

  The final display width of the DPX spectrum is usually limited by the number of pixels constituting the display device. For example, a typical DPX spectrum has a width of 768 or 800 pixels, which is limited by hardware limitations, display limitations, or both. Unfortunately, when a very wide frequency span is viewed using the entire display width of about 800 pixels, there is a possibility that important signals cannot be displayed. For example, when a 2 GHz bandwidth is displayed in a 768 pixel wide DPX spectrum, a 3.48 MHz wide W-CDMA signal is only 2 pixels wide on the display. This can be said that due to the large amount of data that appears on the display, the relevant signal details have been lost in the DPX spectrum.

  Embodiments of the present invention seek to solve the aforementioned limitations by generating a second DPX spectrum that is focused on a region of interest in the first DPX spectrum in a user-controllable manner. Is. At this time, the first and second DPX spectra are displayed simultaneously.

  Accordingly, an embodiment of the present invention provides a processor that generates a bitmap image from an input test signal, a user interface for identifying a portion of the bitmap image, and a second portion from the identified portion of the bitmap image. And a second image generating unit configured to generate an image. The same input test signal (or the same data generated from the input test signal) may be used to generate the bitmap image and the second image. Furthermore, the bitmap image and the second image may be simultaneously displayed on the display device. In some embodiments, the test signal may be down-converted (frequency converted) and filtered before the second image is generated from the test signal. In many embodiments, corrections are made for temporal consistency between the bitmap image and the second image. The user can select the first part and the last part of the part of the bitmap image generated as the second image by the user interface. In a further embodiment, the user may specify a portion of the original bitmap image or the second bitmap image, and a third bitmap image may be generated for the specified portion.

  Another embodiment of the present invention includes a method for generating a bitmap image from a test signal. After generating the first bitmap image of the test signal, the user identifies a portion of the first bitmap image. Next, a second bitmap image that covers a portion of the first bitmap image is generated. In some embodiments, the second bitmap image is generated from a test signal (or data generated from an input test signal). Subsequently, in some embodiments, the first bitmap image and the second bitmap image are displayed simultaneously. In a further embodiment, a third bitmap image is generated that covers a portion of the second bitmap image or a second portion of the first bitmap image.

More specifically, concept 1 of the present invention is a test and measurement device,
A processor for generating a bitmap image from an input test signal;
A user interface for identifying a portion of the bitmap image;
A second image generator configured to generate a second image including the portion of the bitmap image.

  The concept 2 of the present invention is the test and measurement apparatus of the concept 1, wherein the input test signal is used to generate the bitmap image and the second image.

  The concept 3 of the present invention is the test and measurement apparatus of the concept 1, and further includes a display device that simultaneously displays the bitmap image and the second image.

  The concept 4 of the present invention is the test and measurement apparatus according to the concept 1, and further includes a down converter that down-converts the test signal before generating the second image.

  The concept 5 of the present invention is the test and measurement apparatus according to the concept 4 and further includes a narrow span correction filter that filters the down-converted test signal before sending it to the second image generation unit.

  The concept 6 of the present invention is the test and measurement apparatus according to the concept 1, wherein the bitmap image and the second image are corrected with respect to time consistency.

  The concept 7 of the present invention is the test and measurement apparatus according to the concept 1, wherein the user interface is configured so that the user can select the first and last portions of the bitmap image generated as the second image. It is characterized by that.

  The concept 8 of the present invention is the test and measurement apparatus according to the concept 1, wherein the user can specify the second part of the bitmap image and the second part of the bitmap image from the second part by the user interface. A third image generator configured to generate three images is further provided.

  The concept 9 of the present invention is the test and measurement apparatus according to the concept 1, wherein the user can specify a part of the second image by the user interface, and the third part from the specified part of the second image. A third image generator configured to generate an image is further included.

The concept 10 of the present invention is a method in a test and measurement apparatus,
Receiving a test signal;
Generating a first bitmap image of the test signal;
Receiving user input identifying a portion of the first bitmap image;
Generating a second bitmap image that covers the portion of the first bitmap image.

  The concept 11 of the present invention is the method of the concept 10, characterized in that the step of generating the second bitmap image includes the step of generating the second bitmap image from the test signal. .

  Concept 12 of the present invention is the method of concept 10, further comprising the step of simultaneously displaying the first and second bitmap images.

  The concept 13 of the present invention is the method of the concept 12, wherein the first bitmap image and the second bitmap image are temporally aligned before the first and second bitmap images are displayed simultaneously. And further comprising a step of causing

  Concept 14 of the present invention is the method of concept 10 further comprising the step of down-converting the test signal.

  Concept 15 of the present invention is the method of concept 14 further comprising the step of filtering the down-converted test signal.

  The concept 16 of the present invention is the method of the concept 10 characterized in that the user input specifies the beginning and end of the portion of the first bitmap image.

Concept 17 of the present invention is the method of concept 10 above,
Receiving user input identifying a second portion of the first bitmap image;
Generating a third bitmap image covering the second part.

Concept 18 of the present invention is the method of Concept 10 above,
Receiving user input identifying a portion of the second bitmap image;
Generating a third bitmap image that covers the portion of the second bitmap image.

  The objects, advantages and other novel features of the present invention will become apparent from the following detailed description when read in conjunction with the appended claims and drawings.

FIG. 1 is a functional block diagram of a conventional real-time spectrum analyzer. FIG. 2 is a diagram for explaining the processing operation of the continuous-time processor shown in FIG. FIG. 3 is a screen shot of a conventional DPX spectrum. FIG. 4 is a diagram illustrating a relationship between elements including the first and second DPX spectra according to the embodiment of the present invention. FIG. 5 is a functional block diagram of a spectrum analyzer including a second DPX processor according to an embodiment of the present invention. FIG. 6 is a flowchart of an example method according to an embodiment of the invention. FIG. 7 is a diagram showing the relationship between the elements of the embodiment of the present invention including two second spectra generated from the first spectrum. FIG. 8 is a diagram showing a relationship between elements of another embodiment of the present invention including two second spectra generated from the first spectrum. FIG. 9 is a diagram showing the relationship between the elements of the embodiment of the present invention including the first, second, and third spectra.

  FIG. 3 is an example of a conventional DPX spectrum 312 screen generated by the system described above. The illustrated DPX spectrum 312 is displayed on the display device 310, and the display device may be a general device for a test and measurement device, such as a liquid crystal display device (LCD). The display device 310 may be incorporated in the test and measurement device or may be an independent external display device.

  As described above, FIG. 3 is drawn in gray scale, but the DPX spectrum 312 displays data obtained by sampling the signal under test on the display device 310 with color pixels. The width of the DPX spectrum shown on the display is fundamental due to display hardware limitations, typically due to limitations caused by the processor that generates the bitmap image, such as the bitmap database 220 of FIG. Limited. For example, the DPX spectrum 312 of FIG. 3 has a width of about 800 pixels.

  Due to the limited number of pixels in the width of the DPX spectrum, a large amount of information must be transmitted in each pixel width of the DPX spectrum, but this information is lost or cannot be recognized on the display device 310. It may be. This is especially true when the signal under test is a broadband signal. For example, if the test signal represented by the real-time DPX spectrum is 2 GHz and the width of the DPX spectrum is 768 pixels, the 3.48 MHz-wide CDMA signal portion in 2 GHz is displayed with only 2 pixels. This would not be wide enough as a screen area on the DPX spectrum for the user to view important data. In other words, the DPX spectrum is so compressed that it will be difficult to distinguish (discriminately recognize) important signals from other display data.

  FIG. 4 is a diagram illustrating a relationship of components including the first DPX spectrum 412 and the second DPX spectrum 432 according to the embodiment of the present invention. In this example, the first DPX spectrum 412 is the same as the DPX spectrum 312 in FIG. A portion 420 of the first DPX spectrum 412 displayed on the display device 410 is a spectrum region that the user has selected to know in more detail. Accordingly, when the zoom mode is activated, a second DPX spectrum 432 is generated and shown on the display device 430, which shows details of a portion 420 of the first DPX spectrum 412. Importantly, in some embodiments, the second DPX spectrum 432 is not simply an extension of the portion 420 of the first DPX spectrum, and, as will be described, the second DPX spectrum 432 is converted to the original test by a separate DPX processor. That is, it is newly generated from the signal data. Thereby, the user can effectively obtain detailed information from the test and measurement apparatus.

  In some embodiments, the width of the portion 420 of the first DPX spectrum can be adjusted by a user operation such as stretching the edge of the window or other general display operations. In other embodiments, the user selects the portion to examine in detail in the DPX spectrum by selecting the center point as well as the window width of portion 420.

  FIG. 5 is a functional block diagram of a spectrum analyzer including a second DPX processor 550 according to an embodiment of the present invention. The test and measurement apparatus 500 according to an embodiment of the present invention includes a processor such as a full span DPX bitmap processor 510 that generates a bitmap image from an input test signal. The DPX bitmap image generated from the processor 510 includes the full bandwidth of the test signal. The full span DPX bitmap image is displayed in the main display window 520. The display window 520 may be displayed on a display device, and this display device may be incorporated in the test measurement device or may be provided independently outside the test measurement device.

  The user controls the user interface 502 to specify a portion in the bitmap image for which detailed information is desired. This user interface allows the user to select specific portions in the full span DPX bitmap image displayed in the second window or on the second display device as described above.

  A second image generator, such as second DPX bitmap processor 550, generates a second image during zoom display window 560, which is the original bit generated by full span processor 510. Contains the identified part of the map image. A system such as that shown in FIG. 5 uses the same basic data (the test generated from the test signal) to generate both the original bitmap image obtained from processor 510 and the second bitmap image obtained from processor 550. Note that signal data is used. The original data (test signal data) obtained from the acquisition (data acquisition) system is down-converted (frequency conversion) before being sent to a second image generator such as the second DPX bitmap processor 550. Additional processing such as processing and filtering may be performed. Initial filtering and down-conversion may be performed by the down converter 530, and optionally a narrow span correction filter 540 may be provided in the system.

  Before being displayed on the main window 520 and the zoom window (second window) 560, the first and second second DPX bitmaps are corrected for time consistency.

  FIG. 6 is a flowchart of an example method according to an embodiment of the invention. First, it is assumed that a test signal is received and the first bitmap image of the signal is generated. In process 610, a flow (process flow) 600 receives input from a user regarding a portion to be observed in more detail. This is done, for example, by the user selecting a zoom process or opening a zoom window on the test and measurement device. In the process 620, input from the user is received. This input relates to a generated zoom window, for example, and includes a width and a position for specifying a portion of the first bitmap image. In process 630, various setting values (including parameters: window width, height, position, etc.) of the zoom window may be adjusted in response to user input. Subsequently, in process 640, a zoom window is generated from the same data (test signal data) that generated the original bitmap image, and is displayed to the user in process 650. The generated second bitmap image covers a portion in the first bitmap image specified by the user in the process 620. Thereafter, the processing may return again to the processing 630 to adjust the zoom window.

  Depending on the embodiment, as shown in FIG. 4, the first and second bitmap images are temporally aligned and then displayed simultaneously. As described above, the second bitmap image may be down-converted and filtered before being generated.

  FIG. 7 is a diagram illustrating an embodiment of the present invention that includes two second spectra generated from the first spectrum, ie, two zoom windows. FIG. 7 is similar to that of FIG. 4, but two zoom windows 722 and 732 are generated from two portions 720 and 730 of the main window 712 on the display 710, respectively, and separate display devices 714. And 716 are different from each other. Two zoom windows 722 and 732 may be generated as described above for a single zoom window, but in parallel with the first and second processors 510 and 550 of FIG. A map processor may be used.

  FIG. 8 is a diagram illustrating another embodiment of the present invention including two second spectra 822 and 832 generated corresponding to two identified portions 820 and 830 in the first spectrum 812, respectively. This embodiment is similar to that shown in FIG. 7, but two zoom windows 822 and 832 are shown on a single display 814. Finally, as shown in FIG. 9, the system displays a zoom window 922 that is a detailed display of the portion 920 of the original main window 912, and in addition, a detailed display of the portion 940 of the first zoom window 922. The second zoom window 942 may be included. These windows may be referred to as first, second, and third windows, and may be displayed on separate display devices 910, 914, and 916, respectively. Further, these three windows may be displayed on a single display device.

  Many of the embodiments described above include a user interface through which the user inputs various parameters (such as settings), but instead the test and measurement device automatically determines the various parameters. You may do it.

  In the embodiment illustrated and described above, the present invention has been described as being used in a real-time spectrum analyzer, but embodiments of the present invention include a swept spectrum analyzer, a signal analyzer, a vector signal analyzer, It will be apparent that it can be used effectively in any type of test and measurement device that displays frequency domain signals, such as an oscilloscope.

  In various embodiments, the various elements of the present invention may be implemented in hardware, software, or a combination of the two, and may be a general purpose microprocessor, digital signal processor (DSP), application specific An IC (ASIC), an FPGA (Field Programmable Gate Array), or the like may be used.

  As is clear from the above description, the present invention represents a significant advance in the field of frequency domain bitmap display. While specific embodiments of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention.

500 Test and Measurement Equipment 510 Full Span DPX Bitmap Processor 520 Main Display Window 530 Down Converter 540 Narrow Span Correction Filter 550 Second DPX Bitmap Processor 560 Zoom Display Window 710 First Display Device 712 Main Window 714 Second Display Device 716 Third display 720 Identified portion of main window 722 First zoom window 730 Identified portion of main window 732 Second zoom window 810 First display device 812 Main window 814 Second display device 820 Identified portion of main window 822 First zoom window 830 Identified portion of main window 832 Second zoom window 910 First display 912 Indou 914 second display device 916 the third display device 920 main window identified portion 922 first zoom window 940 identified portion 942 second zoom window of the first zoom window

Claims (2)

A processor for generating a bitmap image from an input test signal;
A user interface for identifying a portion of the bitmap image;
A test and measurement apparatus comprising: a second image generation unit configured to generate a second image including the part of the bitmap image. An image generation method in a test and measurement apparatus,
Receiving a test signal;
Generating a first bitmap image of the test signal;
Receiving user input identifying a portion of the first bitmap image;
Generating a second bitmap image that covers the portion of the first bitmap image.