- May 11, 2008
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I thought it could be fun to start a thread with such information and to continuously update it with progress. Feel free to join in.
Background information :
http://www.hobbyprojects.com/oscilloscope_tutorial/oscilloscope_working.html
Basic analog oscilloscope :
Basic digital oscilloscope :
To create a proper analog frontend of an oscilloscope, any old analog design will do of an old analog 25MHz/50MHz/60MHz or 100Mhz oscilloscope. Use some modern components in the design and it could be a good start.
When wanting to make a digital oscilloscope, it is very important that there is a relation between the sampling rate and the timebase. We want the sampling rate as high as possible because then the horizontal (time)resolution increases as well, which makes it possible to see hf glitches in the signal. And we want a known preset relationship between the sample rate and the time base. This relationship is a compromise of maximum sample rate together with the available amount of memory to store the digitized signal we want to examine. The time base produces the horizontal sweep in an analog oscilloscope. In a digital oscilloscope it is also present but does not provide a sweep signal. It does however produce time information. The screen is divided into sections such a volt/div and sec/div. This is called the oscilloscope graticule. The time base adjust the value for the sec/div sections. The setting of the amplifier/attenuator section in the analog frontend determines the volt/div. As we will later see in another post, we also have to establish a relationship between the resolution of the analog to digital converter and the volt/div setting. The better(higher) the resolution, the more voltage level information we can capture.
For to make the time base or to make a signal wave generator (ofcourse with added components to adjust signal voltage level and adjustable low pass filter), the AD9834 in combination with an FPGA (and programmable PLL for the ADC) is very usable :
The AD9833 is the 12,5Mhz(25Mhz) version.
Background information :
http://www.hobbyprojects.com/oscilloscope_tutorial/oscilloscope_working.html
Basic analog oscilloscope :
Basic digital oscilloscope :
To create a proper analog frontend of an oscilloscope, any old analog design will do of an old analog 25MHz/50MHz/60MHz or 100Mhz oscilloscope. Use some modern components in the design and it could be a good start.
When wanting to make a digital oscilloscope, it is very important that there is a relation between the sampling rate and the timebase. We want the sampling rate as high as possible because then the horizontal (time)resolution increases as well, which makes it possible to see hf glitches in the signal. And we want a known preset relationship between the sample rate and the time base. This relationship is a compromise of maximum sample rate together with the available amount of memory to store the digitized signal we want to examine. The time base produces the horizontal sweep in an analog oscilloscope. In a digital oscilloscope it is also present but does not provide a sweep signal. It does however produce time information. The screen is divided into sections such a volt/div and sec/div. This is called the oscilloscope graticule. The time base adjust the value for the sec/div sections. The setting of the amplifier/attenuator section in the analog frontend determines the volt/div. As we will later see in another post, we also have to establish a relationship between the resolution of the analog to digital converter and the volt/div setting. The better(higher) the resolution, the more voltage level information we can capture.
For to make the time base or to make a signal wave generator (ofcourse with added components to adjust signal voltage level and adjustable low pass filter), the AD9834 in combination with an FPGA (and programmable PLL for the ADC) is very usable :
http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9834/products/product.htmlThe AD9834 is a 75 MHz low power DDS device capable of producing high performance sine and triangular outputs. It also has an on-board comparator that allows a square wave to be produced for clock generation. Consuming only 20 mW of power at 3 V makes the AD9834 an ideal candidate for power-sensitive applications.
Capability for phase modulation and frequency modulation is provided. The frequency registers are 28 bits; with a 75 MHz clock rate, resolution of 0.28 Hz can be achieved. Similarly, with a 1 MHz clock rate, the AD9834 can be tuned to 0.004 Hz resolution. Frequency and phase modulation are affected by loading registers through the serial interface and toggling the registers using software or the FSELECT pin and PSELECT pin, respectively.
The AD9834 is written to using a 3-wire serial interface. This serial interface operates at clock rates up to 40 MHz and is compatible with DSP and microcontroller standards.
The device operates with a power supply from 2.3 V to 5.5 V. The analog and digital sections are independent and can be run from different power supplies, for example, AVDD can equal 5 V with DVDD equal to 3 V.
The AD9834 has a power-down pin (SLEEP) that allows external control of the power-down mode. Sections of the device that are not being used can be powered down to minimize the current consumption. For example, the DAC can be powered down when a clock output is being generated.
The part is available in a 20-lead TSSOP.
Applications
Frequency stimulus/waveform generation
Frequency phase tuning and modulation
Low power RF/communications systems
Liquid and gas flow measurement
Sensory applications: proximity, motion, and defect detection
Test and medical equipment
The AD9833 is the 12,5Mhz(25Mhz) version.
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