Douglas R Wagner

US Patent:

51210657, Jun 9, 1992

Filed:

Jul 13, 1990

Appl. No.:

7/553539

Inventors:

Douglas R. Wagner - Monroe WA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

G01R 1900

US Classification:

324607

Abstract:

Aliasing and synchronization difficulties in determining transfer functions in mixed domain (analog and digital) systems are overcome by sampling the analog signal at an integer multiple of the digital signal, and zero filling the set of sampled digital data so that the sampled digital data corresponds to the more densely sampled analog data. By so doing, a single fixed frequency anti-alias filter in the analog channel can be used to avoid aliasing problems in mixed domain measurements over any span of frequencies, up to the entire passband of the filter.

US Patent:

52911403, Mar 1, 1994

Filed:

Aug 19, 1993

Appl. No.:

8/109844

Inventors:

Douglas R. Wagner - Monroe WA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

G06F 1100
H03K 1302

US Classification:

324615

Abstract:

Aliasing and synchronization difficulties in determining transfer functions in mixed domain (analog and digital) systems are overcome by sampling the analog signal at a higher sampling frequency that the digital signal, and zero filling the set of sampled digital data (if necessary) so that the sampled digital data corresponds to the more densely sampled analog data. By so doing, a single fixed frequency anti-alias filter in the analog channel can be used to avoid aliasing problems in mixed domain measurements over any span of frequencies, up to the entire passband of the filter. The invention is particularly illustrated with reference to measurements both across digital-to-analog boundaries and across analog-to-digital boundaries.

US Patent:

55984398, Jan 28, 1997

Filed:

May 13, 1994

Appl. No.:

8/242484

Inventors:

Douglas R. Wagner - Monroe WA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

H04L 2714

US Classification:

375326

Abstract:

A method and apparatus for recovering the phase of a symbol clock operating at a predetermined symbol rate is described. A modulated RF signal which has been downconverted or a modulated baseband signal is filtered and sampled by a high speed converter. A high speed digital signal processor processes the digitized signal to determine the phase of the symbol clock. The symbol phase is determined independent of carrier phase by repetitively resampling the digitized signal and constructing the histogram for each resample of that signal. By comparing the histograms of each resample the symbol phase may be identified. Using the symbol rate and phase, the signal may be analyzed for carrier phase and frequency errors and modulation accuracy using eye diagrams, modulation trajectories and symbol content.