Apparatus and method for input channel isolation within an electronic test instument

• US 20040116094A1
• Filed: 12/16/2002
• Published: 06/17/2004
• Est. Priority Date: 12/16/2002
• Status: Active Grant

• Current Assignee: Tektronix Incorporated (Fortive Corp.)
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Eastwood, James S.
• Granted Patent: US 7,113,750 B2
• Time in Patent Office: Days
• US Class Current: 455/323
• CPC Class Codes: H04B 5/75 for isolation purposes
• CPC Class Codes: H04L 1/24 Testing correct operation

Abstract

An electrical isolation device wherein a signal to be electrically isolated is mixed with a carrier signal by a multiplier to produce a modulated carrier signal which is passed through an isolation barrier and demodulated and filtered to extract thereby the initial input signal.

Claims

1. Apparatus, comprising:

a modulator, for modulating an input signal onto a carrier signal to produce thereby a modulated carrier signal having associated with it a first ground reference;

an isolator, for processing said modulated signal to produce a corresponding modulated signal having associated with it a second ground reference;

a demodulator, for demodulating said corresponding modulated signal and a corresponding carrier signal to produce thereby a demodulated signal; and

a smoother, for retrieving a corresponding input signal from said demodulated signal.

2. The apparatus of claim 1, wherein said modulator comprises a switch operating to multiply the input signal by ±

1 in response to the carrier signal.

3. The apparatus of claim 1, wherein said modulator and demodulator comprise balanced mixers.

4. The apparatus of claim 1, wherein said isolator comprises a transformer.

5. The apparatus of claim 4, wherein said isolator comprises a pulse transformer and said carrier signal comprises a square wave having a frequency greater than twice the frequency of said input signal.

6. The apparatus of claim 1, wherein said isolator comprises at least one of a linear optocoupler and a fiber optic device.

7. The apparatus of claim 1, wherein said isolator comprises a radio frequency (RF) transmitter/receiver.

8. The apparatus of claim 1, further comprising:

an oscillator, for generating said carrier signal; and

a second isolator, for processing said carrier signal to produce said corresponding carrier signal;

said carrier signal having associated with it said first ground reference;

said corresponding carrier signal having associated with it said second ground reference.

9. The apparatus of claim 1, further comprising:

an oscillator, for generating said corresponding carrier signal; and

a second isolator, for processing said corresponding carrier signal to produce said carrier signal;

said carrier signal having associated with it said first ground reference;

said corresponding carrier signal having associated with it said second ground reference.

10. The apparatus of claim 9, wherein:

said first and second isolators comprise transformers.

11. The apparatus of claim 1, wherein:

said carrier and corresponding carrier signals comprise respective square wave signals having a common predetermined frequency.

12. The apparatus of claim 11, wherein said predetermined frequency is less than a input signal frequency.

13. The apparatus of claim 1, wherein said smoother comprises at least one of a Bessel filter, a Gaussian filter and an Elliptical filter.

14. A method, comprising:

modulating an input signal onto a carrier signal to produce thereby a modulated carrier signal having associated with it a first ground reference;

transmitting the modulated signal to a demodulator using an isolator;

demodulating the transmitted modulated signal to produce thereby a demodulated signal; and

filtering the demodulated signal to retrieve said input signal.

15. The method of claim 14, wherein said carrier signal comprises one of a sine wave, a square wave and a saw tooth wave.

16. The method of claim 14, wherein said isolator comprises one of a transformer, optical isolator and radio frequency (RF) transmitter/receiver.

17. The method of claim 14, wherein said step of modulating is performed using one of a balanced mixer and a switch.

18. The method of claim 14, wherein said filtering is realized using at least one of a Bessel filter, a Gaussian filter and elliptical filter.

19. A test and measurement instrument, comprising:

a modulator, for modulating an input signal onto a carrier signal to produce thereby a modulated carrier signal having associated with it a first ground reference;

an isolator, for processing said modulated signal to produce a corresponding modulated signal having associated with it a second ground reference;

a demodulator, for demodulating said corresponding modulated signal and a corresponding carrier signal to produce thereby a demodulated signal; and

a smoother, for retrieving a corresponding input signal from said demodulated signal.