Test and measurement instrument having multi-channel telecommunications mask testing capability
First Claim
1. A test and measurement instrument for multi-channel mask testing comprising:
- a group of M signal input terminals for receiving M signal input from a circuit under test;
an acquisition system coupled to said M signal input terminals for acquiring samples of a waveforms at each of said M signal input terminals;
a controller for generating mask pixel data defining a mask;
a memory for storing said waveform samples and said mask pixel data, said mask pixel data including an identification code;
comparison circuitry for reading a memory location, and determining if any acquired waveform simple of said signal from each of said M signal input terminals is to be written into a memory location currently storing a mask pixel, causing a mask violation; and
display circuitry for simultaneously displaying a representation of said mask and all of said waveforms from said M signal input terminals.
1 Assignment
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Accused Products
Abstract
In a test and measurement instrument having M signal input channels, individual samples representing a signal from each channel are compared to mask pixels to detect non-compliance with a given specification. Initial mask and waveform positions on a display screen of the oscilloscope are determined by an AUTOSET TO MASK function. Comparison of mask pixels and waveform pixels to detect collision between a waveform pixel and a mask pixel (i.e., a mask violation) is performed substantially in real time, as the pixels are being composited into a raster memory by a rasterizer. Acquisitions are performed simultaneously and repeatedly. Acquired waveforms from all M signal input channels are sequentially compared to the mask and drawn on screen during the following acquisition period. Thus, M waveforms can be tested for compliance with a telecom mask substantially within a single acquisition time period. A system employing a multiplexer can select M channels at a time from a group of N channels to decrease the time required to test all N channels. The intensity of pixels representing samples violating the mask is preferably increased for better visibility against the telecom mask.
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Citations
18 Claims
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1. A test and measurement instrument for multi-channel mask testing comprising:
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a group of M signal input terminals for receiving M signal input from a circuit under test;
an acquisition system coupled to said M signal input terminals for acquiring samples of a waveforms at each of said M signal input terminals;
a controller for generating mask pixel data defining a mask;
a memory for storing said waveform samples and said mask pixel data, said mask pixel data including an identification code;
comparison circuitry for reading a memory location, and determining if any acquired waveform simple of said signal from each of said M signal input terminals is to be written into a memory location currently storing a mask pixel, causing a mask violation; and
display circuitry for simultaneously displaying a representation of said mask and all of said waveforms from said M signal input terminals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
said comparison circuitry is a rasterizer; said memory is a raster memory;
said comparison is performed by said rasterizer examining pixel data of said raster memory for said identification code as said waveform samples are composited into said raster memory; and
said comparison being performed sequentially on a waveform basis.
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3. The test and measurement instrument of claim 2, wherein each of said waveforms is displayed in a different one of M colors and said mask is displayed in an M+1 color.
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4. The test and measurement instrument of claim 3, wherein
in response to a determination of a mask violation, said rasterizer increases an intensity value of said waveform sample violating said mask prior to compositing said sample into said raster memory. -
5. The test and measurement instrument of claim 1 wherein said controller generating mask pixels is a microprocessor.
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6. The test and measurement system of claim 1 wherein said controller generating mask pixels is a dedicated ASIC.
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7. The test and measurement instrument of claim 1 wherein:
said test and measurement instrument is a digital oscilloscope.
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8. A test and measurement system for multi-channel mask testing, comprising:
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a multiplexer having N input channels and M output channels, where N is greater than M, and M is greater than one, for selecting ones of said N-channels in groups of M-channels at a time in response to a first control signal;
each of said N input channels being coupled to receive a signal from a respective one of N output channels of a circuit under test;
a test and measurement instrument operating in response to a second control signal, and including;
a group of M signal input terminals, each of said M signal input terminals being coupled to a respective one of said M signal output channels;
an acquisition system coupled to said M signal input terminals for acquiring samples of a waveform at each of said M signal input terminals;
a controller for generating mask pixel data defining a mask;
a memory for storing said waveform samples and said mask pixel data, said mask pixel data including an identification code;
comparison circuitry for reading a memory location, and determining if any acquired waveform sample of said signal from each of said M signal input terminals is to be written into a memory location currently storing a mask pixel, causing a mask violation; and
display circuitry for simultaneously displaying a representation of said mask and all of said waveforms from said M signal input terminals; and
a controller coupled to said multiplexer and to said test and measurement instrument for generating said first and second control signals. - View Dependent Claims (9, 10, 11, 12, 13, 14)
said comparison circuitry is a rasterizer; said memory is a raster memory;
said comparison is performed by said rasterizer examining pixel data of said raster memory for said identification code as said waveform samples are composited into said raster memory; and
said comparison being performed sequentially on a waveform basis.
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10. The test and measurement system of claim 9, wherein each of said waveforms is displayed in a different one of M colors and said mask is displayed in an M+1 color.
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11. The test and measurement system of claim 10, wherein
in response to a determination of a mask violation, said rasterizer increases an intensity value of said waveform sample violating said mask prior to compositing said sample into said raster memory. -
12. The test and measurement system of claim 8 wherein said controller generating mask pixels is a microprocessor.
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13. The test and measurement system of claim 8 wherein said controller generating mask pixels is a dedicated ASIC.
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14. The test and measurement system of claim 8 wherein:
said test and measurement instrument is a digital oscilloscope.
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15. A method for performing multi-channel mask testing in test and measurement system including a test and measurement instrument having mask testing capability, comprising the steps of:
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selecting M channels at a time from a group of N channels;
acquiring samples of waveforms at M input terminals coupled to said M channels;
generating mask pixel data defining a mask;
storing said waveform samples and said mask pixel data in a memory, said mask pixel data including an identification code;
comparing mask pixel data and waveform sample data by reading a memory location, and determining if a waveform sample of said acquired waveform samples is to be written into a memory location currently storing a mask pixel, causing a mask violation;
compositing said waveform samples into a raster memory;
displaying simultaneously said mask and said M waveforms on a display screen. - View Dependent Claims (16, 17, 18)
said comparing step is performed by a rasterizer examining pixel data of said raster memory for said identification code as said waveform samples are composited into said raster memory; - and
said comparison of said samples is made on a waveform basis.
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17. The method of claim 16, further including the step of:
increasing an intensity value of a sample determined to cause a mask violation before compositing said sample in said raster memory.
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18. The method of claim 15, wherein said displaying step includes:
displaying each of said waveforms in one of M different colors and displaying said mask in an M+1 color.
Specification