GB2379096A

GB2379096A - Apparatus and method for making an RF connection to an RF module

Info

Publication number: GB2379096A
Application number: GB0120399A
Authority: GB
Inventors: Neil Peniket
Original assignee: Ubinetics Ltd
Current assignee: Aeroflex Cambridge Ltd
Priority date: 2001-08-22
Filing date: 2001-08-22
Publication date: 2003-02-26
Also published as: GB0120399D0

Abstract

An RF module having a planar connector area, preferably a PCB, for connection to a coaxial cable 18 and for test probing. The connector area comprises a conductive outer area 6 and a conductive inner area 8, the outer area 6 substantially but not wholly encloses the inner conductive area 6, and the inner and outer conductive areas 6,8 are electrically isolated by an intermediate insulative area 10. The arrangement of the conducting areas 6,8 permits access for a soldering iron (15, Fig 3) to the inner conductive area 8.

Description

APPARATUS AND METHOD FOR MAKING AN RF CONNECTION TO AN RF MODULE This invention relates to an RF module particularly though not exclusively for use in cellular mobile devices such as those for use in GSM or GPRS enabled communications networks.

In accordance with a first aspect of the invention there is provided an RF module having a generally planar connector area for connection to a coaxial cable and for test probing, the connector area comprising a conductive outer area and a coplanar conductive inner area, the outer area substantially but not wholly enclosing the inner conductive area, and the inner and outer conductive areas being electrically isolated by an intermediate insulative area.

In a second aspect, the invention provides a method of providing electrical connectivity to an RF module comprises providing a conductive outer area and a coplanar conductive inner area substantially but not wholly enclosed by the outer conductive area, the inner and outer conductive areas being electrically isolated by an intermediate insulative area.

Embodiments of the invention will now be described by way of example with reference to the drawings in which :- Figure 1 is a schematic plan view of an RF module in accordance with the invention; Figure 2 is an enlarged plan view of the portion marked A of Figure 1 showing test probing of the module ; Figure 3 is an enlarged plan view of the portion marked A in Figure 1 showing access for a soldering tool ; and Figure 4 is an enlarged plan view of the portion marked A of Figure 1 showing attachment of a coaxial cable to the module.

Miniaturised embedded wireless communications modules (such as Ubinetics Part No. GM400) require a connection to an external RF signal such as that leading to an antenna. A schematic view of such a module is shown in Figure 1.

The module has an integral PCB 2 upon which is mounted a shielded can 4 which contains the components forming the RF module. The can 4 is raised above the surface of the PCB (extending out of the plane of the drawing). Conventionally, such modules have a test probe area allowing testing of the assembled module and a separate connector area for connection to an antenna once the module is assembled for example to form a mobile handset. In many cases, in the prior art, no probe area for testing purposes is provided and testing of the module is carried out"over the air" by establishing a wireless link via the antenna. However, it will be appreciated that an over the air link can only be carried out once the module has been assembled into the final product and thus failure of the module results in a requirement either to disassemble the product or to scrap the product complete with the failed module.

Thus, over the air testing can incur significant costs if the failure rate of the modules reaches a significant rate.

Conversely, the prior art provision of separate probing areas and areas for connecting to an antenna increases unit cost and also unit size.

With reference to Figures 2,3 and 4, the arrangement of conductive pads formed on the PCB is such that probing and connection to a coaxial cable may be achieved within a compact area of the PCB.

With particular reference to Figure 2, an outer conductive area 6 partially surrounds an inner conductive area 8. The two conductive areas are electrically isolated by an unplated portion of the PCB substrate 10 which forms an intermediate insulative area.

With this arrangement, an"off the shelf'test probe consisting of a centre pin 12 and an outer concentric ground ring 14 may be placed over the test area so that the centre pin 12 makes electrical contact with the inner conductive area 8 and the concentric ground ring 14 makes electrical contact with a large part of the outer conductive area 6 (in the example shown, more than half the circumference of the outer ground ring is in contact with the pad 6).

The use of a coaxial probe allows accurate impedance matching to be achieved (which is important particularly for calibration purposes).

With reference to Figure 3, the outer conductive area 6 deliberately has an opening 13 facing towards the edge of the PCB (away from the raised can 4) which allows easy access for a soldering iron 15 without risk of bridging the insulative area 10 with a solder flow. Therefore, with reference to Figure 4, it is relatively simple to attach the inner conductor 16 of a coaxial cable to the inner conductive area 8 using solder 17 and also to connect the outer conductor of the coaxial cable 18 to an enlarged portion 20 of the outer conductive area 6 using solder 21.

Thus by providing coaxial inner and outer conductive areas which allow test probing using an impedance matched probe and also providing comfortable access for hand soldering of a coaxial cable during final assembly, the dual requirements of a single connection area and the avoidance of an expensive RF connector (such as an SMA connector) are met. Furthermore, the pads may be implemented simply as additional plated areas in the design of the PCB for the module. Thus the additional cost required to provide this type of "connector-less" electrical connection is negligible.

Claims

Claims 1. An RF module having a generally planar connector area for connection to a coaxial cable and for test probing, the connector area comprising a conductive outer area and a coplanar conductive inner area, the outer area substantially but not wholly enclosing the inner conductive area, and the inner and outer conductive areas being electrically isolated by an intermediate insulative area.
2. An RF module according to claim 1, wherein the inner conductive area is located substantially at the geometric centre of the outer conductive area.
3. An RF module according to claim 1, or claim 2, wherein the outer conductive area has an inner perimeter defining part of the circumference of an outer circle and wherein the inner conductive area is located substantially at the centre of the circle.
4. An RF module according to claim 3, wherein the inner conductive area is circular and is located coaxially within the outer circle.
5. An RF module according to any preceding claim, wherein the connector area is formed as conductive areas formed adjacent an edge of a PCB forming part of the module, and the outer area being arranged to have an opening facing the edge of the PCB to permit access for a soldering iron to the inner conductive area.
6. An RF module according to any preceding claim, wherein the outer conductive area has a pad area arranged to receive a soldered coupling to an outer conductor of a coaxial cable.
7. A method of providing electrical connectivity to an RF module comprises providing a conductive outer area and a coplanar conductive inner area substantially but not wholly enclosed by the outer conductive area, the inner and outer conductive areas being electrically isolated by an intermediate insulative area.

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8. An RF module constructed and arranged as described herein with reference to the drawings.