How to shift phase by 90 degrees between approx 10 Hz and 10 KHz ?

Bernhard Kraemer · 2005-04-22T19:48:25+00:00

Hello, For an experiment, I need to build a little Lock-In Amplifier an my owncircuit. I do not have an external Lock-In and so this will be the cheaperand better solution. The circuit is nearly finished. What lacks is a circuit which should becontrolled by an external oscillator and produces a two output signals,a TTL signal of the same frequency and another of 90 degreesphase shifted. The frequency range should be about 10 Hz to 10 KHz (7decades).I thought about first producing a sine and a cosine signal which I amgoing to convert to TTL afterwards. In "The Art of Electronics" p 294, if found an interestin circuit using the AD639. Unfortunately, our official provider Farnell doesn't offer the IC saying it wouldn't be produced nomore. There is another circuit on the next page using a lot of resitors andcapacities, but it only works for 2 decades instead of seven andhonestly, I would not even know how to calculate the necessary values ;)Finally, having tried another couple of ideas, I still don't figure outhow I can solve my problem. This is why I post on this forum. How couldI compose a circuit dephasing either two sinusoidal or digital signalsby 90 degrees (and if possible, without too much costful and placetaking electronic circuitry)?I hope someone could help me. Yours, Bernhard

Apr 22, 2005 20 Replies

Rate this thread:

"John Fields" a écrit dans le message de news: snipped-for-privacy@4ax.com...

You can have pretty good 50% duty cycle ratio with this:

VDD | | V k(1+cos(2x)) Schmitt Digital Multiplier | k cos(2x) trigger Electronic +-----+ | | +-----+ +-----+ sin(x) ---+--| | | || | | +-+-| clk | |--- Out1 | | X |-----||--+-------| | | |--+--| | +--| | || | |-+-+ | | | |--- Out2 +-----+ | +-----+ | +-----+ | | .-. .-. | | | | | | | | '-' '-' | || | +-----||---------+ | || | | /| | | /-|-------' '-----< | \+|- VDD/2 \|

(created by AACircuit v1.28 beta 10/06/04

formatting link

)

The 50% duty cycle accuracy depends on the VDD to VDD/2 ratio accuracy. However, it'll still be worse than a divided clock, unless you go to considerable efforts.