Browse Prior Art Database

UHF HELICAL DIPLEXER FIXTURE FOR PRODUCTION TEST AND TUNE

IP.com Disclosure Number: IPCOM000008644D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jul-01
Document File: 5 page(s) / 229K

Publishing Venue

Motorola

Related People

Claudio Rodriguez: AUTHOR [+4]

Abstract

This fixture enables the testing and tuning of a production helical diplexer filter unit in a produc- tion environment. The physical contiguration and electrical operating frequency (UHF) of the device to be tested places severe constraints on its testability. The apparatus achieves a successful balance between the demands of an electrically correct connection exhibiting a high degree of repeatability in the 450 MHz frequency range, while overcoming the difficulties encountered in the tuning and evalua- tion of the tested device in a demanding production environment. Through the application of creative mechanical techniques and microstrip technology, a great number of leaded helical diplexers may be evaluated quickly and reliably for their intended application in a production transceiver. Furthermore, consistent results are attained through the implementation of a robust ground signal connection scheme.

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MOTOROLA Technicd Developments

8

UHF HELICAL DIPLEXER FIXTURE FOR PRODUCTION TEST AND TUNE

by Claudio Rodriguez, Mike Lange, Lorenzo Ponce de Leon and Robert Vasquez

ABSTRACT two filters to test in the same package.

  This fixture enables the testing and tuning of a production helical diplexer filter unit in a produc- tion environment. The physical contiguration and electrical operating frequency (UHF) of the device to be tested places severe constraints on its testability. The apparatus achieves a successful balance between the demands of an electrically correct connection exhibiting a high degree of repeatability in the 450 MHz frequency range, while overcoming the difficulties encountered in the tuning and evalua- tion of the tested device in a demanding production environment. Through the application of creative mechanical techniques and microstrip technology, a great number of leaded helical diplexers may be evaluated quickly and reliably for their intended application in a production transceiver. Furthermore, consistent results are attained through the implementation of a robust ground signal connection scheme.

INTRODUCTION

  Helical filter technology has been around almost since the earliest days of radio. Although it has been replaced in most applications, some designs still employ these filters for a variety of purposes. Motorola currently produces a low cost

UHF transceiver which uses a dual (diplexer) helical filter for the receiver preselector and first oscillator injection filter. This unit is somewhat unique in that it provides two distinct filtering func- tions in one compact package, occupying less than ,075 cubic inches of space. Consequently, this design poses a significant challenge to its manufac- turability. For example, the socket type tuning screws of the filter project perpendicularly from the same plane as the four leads serving as the filter interconnects. The body of the unit serves as the shield and grounding point. With the two halves of the resonator being independent, there are in effect

  Difficulty in testing and tuning of the filter comes from its configuration. The leads and the tuning screws both project from the bottom which is then soldered to the circuit board in the intended application. So to effect an accurate test, this requires that the fixture provide a faithful simula- tion of the actual in-circuit connection of the leads and ground. An added difftculty lies with the tuning

screws because they require a socket type tool which acts axially in relation to the screws and falls in line with the connection leads of the filter. To minimize the number of operations required by production personnel in the tuning of the filter, a configuration eliminating the need to invert the fixture to access the screws was developed. This is in contrast to the preceding fixture which required location and insertion from one side and then a fixture inversion step to allow access to the tuning screws along the bott...