**Applied Signal Technology, Inc.Exhibit 31.1**

| I,Gary Yancey, Chief Executive Officer of the registrant, certify that: |
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| 1.                                                                      | Ihave reviewed this quarterly report on Form 10-Q of Applied Signal Technology, Inc.; |
| 2.                                                                      | Basedon my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; |
| 3.                                                                      | Basedon my knowledge, the condensed consolidated financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, and cash flows of the registrant as of, and for, the periods presented in this report; |
| 4.                                                                      | Theregistrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a–15e and 15d–15e) and internal control over financial reporting (as defined in Exchange Act Rules 13a–15(f) and 15d–15(f)) for the registrant and have: |
|                                                                    | (a) | Designedsuch disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared; |
|                                                                    | (b) | Designedsuch internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles; |
|                                                                    | (c) | Evaluatedthe effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and |
|                                                                    | (d) | Disclosedin this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and |
| 5.                                                                      | Theregistrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions): |
|                                                                    | (a) | Allsignificant deficiencies and material weaknesses in the design or operation of internal control over financial reporting that are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and |
|                                                                    | (b) | Anyfraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal controls over financial reporting. |

 

| /s/ Gary L. Yancey      --------------------------------------------------------- | August 31, 2006      -------------------------------- |
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| Gary L. Yancey, Chief Executive Officer                                           |                                                  |