Wideband active-passive differential signal probe

• US 7,619,419 B2
• Filed: 04/28/2006
• Issued: 11/17/2009
• Est. Priority Date: 06/13/2005
• Status: Expired due to Fees

• Current Assignee: FormFactor Beaverton, Inc. (FormFactor Incorporated)
• Original Assignee: Cascade Microtech Incorporated (FormFactor Incorporated)
• Inventors: Campbell, Richard
• Primary Examiner(s): Ghayour; Mohammad H
• Assistant Examiner(s): DSOUZA, JOSEPH FRANCIS A
• Application Number:
  US11/413,738
• Publication Number:
  US 20060290357A1
• Time in Patent Office: 1,299 Days
• Field of Search: 375/247, 375/258, 361/782, 330/69, 330/252, 381/100
• US Class Current: 324/600
• CPC Class Codes: G01R 1/06766 Input circuits therefor
• CPC Class Codes: G01R 1/06772 High frequency probes
• CPC Class Codes: G01R 19/10 Measuring sum, difference or ratio

Abstract

A wideband differential signal probe includes separate paths to convert a lower frequency component and a higher frequency component of a differential signal to a lower frequency single ended signal and a higher frequency single ended signal which are combined for the probe'"'"'s output which is commonly input to instrumentation.

Claims

1. A probe for communicating a differential signal of a device under test, said differential signal comprising at least one of a higher frequency component, including at least one of a higher frequency common mode signal and a higher frequency differential mode signal, and a lower frequency component, including at least one of a lower frequency common mode signal and a lower frequency differential mode signal, said probe comprising:

(a) a choke attenuating said higher frequency common mode signal of said differential signal and having a choke output comprising at least one of said higher frequency differential mode signal and said lower frequency component of said differential signal;

(b) a first filter blocking said higher frequency differential mode signal of said choke output and transmitting said lower frequency component of said choke output;

(c) a differential amplifier attenuating said lower frequency common mode signal of said lower frequency component transmitted by said first filter and converting said lower frequency differential mode signal to a single ended, lower frequency signal;

(d) a second filter blocking transmission of said lower frequency component of said common mode choke output and transmitting a higher frequency single ended signal corresponding to said higher frequency differential mode signal; and

(e) a combiner summing said single ended, lower frequency signal and said single ended, higher frequency signal.

2. The probe of claim 1 wherein a loop gain of said differential amplifier is less than unity.

3. A probe for communicating a differential signal of a device under test, said differential signal comprising at least one of a higher frequency component, including at least one of a higher frequency common mode signal and a higher frequency differential mode signal, and a lower frequency component, including at least one of a lower frequency common mode signal and a lower frequency differential mode signal between a device under test and an instrument, said probe comprising:

(a) a choke attenuating said higher frequency common mode signal of said differential signal and having a choke output comprising at least one of said higher frequency differential mode signal and said lower frequency component of said differential signal;

(b) a first filter blocking said higher frequency differential mode signal of said choke output and transmitting said lower frequency component of said choke output;

(c) a differential amplifier attenuating said lower frequency common mode signal of said lower frequency component transmitted by said first filter and converting said lower frequency differential mode signal to a single ended, lower frequency signal;

(d) a second filter blocking transmission of said lower frequency component of said common mode choke output and transmitting a higher frequency single ended signal corresponding to said higher frequency differential mode signal; and

(e) a resistive combiner to combine said single ended, lower frequency signal and said single ended, higher frequency signal;

(f) a first attenuator conductively connected to said combiner and to an input of said differential amplifier; and

(g) a second attenuator conductively connected to said combiner and to an output of said differential amplifier.

4. A probe for communicating a differential signal of a device under test, said differential signal comprising at least one of a higher frequency component, including at least one of a higher frequency common mode signal and a higher frequency differential mode signal, and a lower frequency component, including at least one of a lower frequency common mode signal and a lower frequency differential mode signal, said probe comprising:

(a) a choke attenuating said higher frequency common mode signal of said differential signal and having a choke output comprising at least one of said higher frequency differential mode signal and said lower frequency component of said differential signal;

(b) a first filter blocking said higher frequency differential mode signal of said choke output and transmitting said lower frequency component of said choke output;

(c) a differential amplifier attenuating said lower frequency common mode signal of said lower frequency component transmitted by said first filter and converting said lower frequency differential mode signal to a single ended, lower frequency signal;

(d) a second filter blocking transmission of said lower frequency component of said common mode choke output and transmitting said higher frequency differential mode signal;

(e) a distributed amplifier receiving said higher frequency differential mode signal and outputting a single ended higher frequency signal; and

(f) a resistive combiner to combine said single ended, lower frequency signal and said single ended, higher frequency signal.

5. A probe for communicating a differential signal of a device under test, said differential signal comprising at least one of a higher frequency component, including at least one of a higher frequency common mode signal and a higher frequency differential mode signal, and a lower frequency component, including at least one of a lower frequency common mode signal and a lower frequency differential mode signal, said probe comprising:

(a) a choke attenuating said higher frequency common mode signal of said differential signal and having a choke output comprising at least one of said higher frequency differential mode signal and said lower frequency component of said differential signal;

(b) a first filter blocking said higher frequency differential mode signal of said choke output and transmitting said lower frequency component of said choke output;

(c) a differential amplifier attenuating said lower frequency common mode signal of said lower frequency component transmitted by said first filter and converting said lower frequency differential mode signal to a single ended, lower frequency signal, said differential amplifier having;

(i)a variable lower frequency common mode signal input impedance; and

(ii)a variable lower frequency differential mode signal input impedance;

(d) a second filter blocking transmission of said lower frequency component of said common mode choke output and transmitting said higher frequency differential mode signal;

(e) an attenuator of said higher frequency differential mode signal transmitted from said second filter;

(f) a distributed amplifier receiving said attenuated higher frequency differential mode signal and outputting a single ended higher frequency signal; and

(g) a combiner summing said single ended, lower frequency signal and said single ended, higher frequency signal.