Quadrature Generation


Thread Starter



Can anybody help me out? What does exactly quadrature signal mean? how to generate a quadarture signal? you have a value in the counter which tells us about the postion of the encoder and then with this value i am supposed to create standard quadrature o/p (2 or 3 oututs, A B and RM) from PWM or outputcompare pins of a pic micro. The preferred frequency could be in the range of 1Mhz or more. The timing parameters for these outputs will be obtained to 2 Inputcapture modules in the microcontroller from the outside analogue world. Can we create this output at good resolution (around 1um resolution) when the linear change is around 1m/s? Is it possible to generate quadrature signals by just using a microcontroller. Will the micro be fast enough to do all the job.i am thinking of using a dsPIC 30 f series which runs at 30MHZ Fcy. Many thanks.

Kind regards,

Robert Scott

In general, quadrature signals mean two signals that are 90 degress out of phase, like a sine and cosine function, or a square wave version of these signals. In your case, it sounds like you want to generate quadrature signals that would simulate what an incremental encoder would produce, if it were moved in a manner that represents some real-world measurement (the 1um resolution that you spoke of). I don't think PWM or output compare pins of a PIC micro would do you any good here. If you are tracking some real-world measurement, then you need to change the A and B outputs in an irregular fashion so as to make the total quadrate count equal the real-world measurement. You could produce output transitions that are only 1 usec apart using PIC software alone. But be careful that you don't violate the input timing specification of the device that has to read your quadrature outputs. 1 usec. is quite fast, and many quadrate decoder boards cannot handle it.

Robert Scott
Real-Time Specialties

Thanks for your help Robert.

I have now been able to generate quad signals from 2 output compares which go onto maximin 1MHZ. Now how do i track the real world measurment? how do i convey the measurement with these quad signals. Say for examples i want to see 5000 pules. How do i do it? i haven't got a clue. is there anybody who can help me out? Many Thanks.


what are the ways we can generate quadrature output with max freq of 1.5 Mhz without using encoders?


Curt Wuollet

With a few logic (TTL or CMOS) chips or probably an ASIC these days. Google quadrature code generator or similar. I vaguely recall seeing chips to convert from step/direction or up/down counter to quadrature and various permutations.



anyone knows how to generate signals A B using a pic or hardware?


<b>moderator's note: I think he means PLC not pic.</b>
He probably does mean a pic chip, not a PLC. See:

I refer him to a standard Hall Effect sensor reference text, or even the instruction sheet that comes with one

Let us know what grade you get on your homework.


Walt Boyes, FInstMC, Chartered Measurement and Control Technologist
Life Fellow, International Society of Automation
Editor in Chief, Control and ControlGlobal.com