United States Patent  [li] Patent Number: 5,614,834
Black et al.  Date of Patent: Mar. 25,1997
 SAMPLING RECEIVERS
 Inventors: Alistair Black, Los Gatos; Raj B.
Apte, Palo Alto; David M. Bloom,
Portola Valley, all of Calif.
 Assignee: The United States of America as
represented by the Secretary of the
Air Force, Washington, D.C.
Heinrich, H.K. et al, "Noninvasive sheet charge density probe for integrated silicon devices", Appl. Phys. Lett. 48 (16), 21 Apr. 1986, pp. 1066-1068.
Primary Examiner—Kenneth A. Wieder
Assistant Examiner—Barry C. Bowser
Attorney, Agent, or Firm—William G. Auton
 Appl. No.: 404,859
 Filed: Mar. 15,1995
 Int. CI.6 G01R 23/17; G01R 1/04;
G06G 9/00; G01B 9/02
 U.S. CI 324/753; 364/822; 364/713;
 Field of Search 324/753; 364/822,
364/77 K, 845, 726, 713, 485, 821, 887;
A Golay sampling receiver is used for optical sampling of voltage and charge at the internal nodes of analog and digital integrated circuits. The sampling receiver uses very high sampling rates together with narrow banding to recover very small signals in the presence of noise. The sampling system is based on harmonic mixing, which is the interaction of a laser sampling train with the electro-optic modulator formed in the GaBs substrate of the device under test. The application of the Golay sampling receiver to an electro-optic sampling system allows the flexibility of running the signal under test at a subharmonic of the laser pulse repetition rate, as well as any harmonic of these subharmonics. The subharmonics are determined by the length code used in the Golay receiver. For a given signal to be sampled, the fundamental frequency is chosen to be a function of the fixed sample rate divided by the code length, and the baseband offset.
3 Claims, 4 Drawing Sheets