WO2018118927A1

WO2018118927A1 - Rf connection apparatus for printed circuit boards with antenna contact pads

Info

Publication number: WO2018118927A1
Application number: PCT/US2017/067325
Authority: WO
Inventors: Bill Murphy
Original assignee: Thomson Licensing
Priority date: 2016-12-21
Filing date: 2017-12-19
Publication date: 2018-06-28

Abstract

An assembly for transferring RF signals from antenna contact pads on a printed circuit board includes a first printed circuit board, at least one conductive contact attached to the first printed circuit board, an RF connector attached to the first printed circuit board having a center conductor of the RF connector attached to the at least one conductive contact, and a second printed circuit board having RF circuitry and at least one contact pad. The second printed circuit board is mounted orthogonally to the first printed circuit board such that the at least one conductive contact of the first printed circuit board makes mechanical contact with the at least one contact pad on the second printed circuit board.

Description

RF CONNECTION APPARATUS FOR PRINTED CIRCUIT BOARDS WITH

ANTENNA CONTACT PADS

FIELD

[0001] The present invention relates to an interconnection system to an antenna, specifically, an interconnection between a board having antenna contact pads and an interface circuit board having RF connectors for antenna interconnection use.

BACKGROUND

[0002] Regulatory compliance for radio transmitters, such as WiFi transmitters dictates maximum power limits of wireless transmitters in products. However, it is desirable to transmit at high power levels to increase the range/reach of wireless radios. Therefore, it is common in the industry to measure and calibrate power level of wireless transmitters for most on-board radios in production such that radio transmitter power levels are slightly lower than the regulatory limit. This renders the best compliant performance. This measurement/calibration is typically done during board-level testing, before finally assembly into the chassis where finding failures is costlier.

[0003] To accurately measure transmitter power, a calibrated connection must be made from the transmitter to the test equipment. Typically, the antenna is required to be disconnected to prevent measurement inaccuracy caused by radiated power loss of the antenna. Typically, a "switch connector" is placed in series between the transmitter and receiver for this purpose. One typical switch connector is manufactured by muRata™ manufacturing. This switch connector is placed in a series connection to break a transmission line trace in an RF circuit to permit on- card testing of the RF components of a printed circuit board (PCB).

[0004] The main disadvantage of switch connectors is the added cost of the PCB assembly. One switch connector is required in the device under test (DUT) for each transmitter to be tested. As wireless technology proliferates, the number of radios increase, and the cost of antennas along with the number of switch connectors increases. Other disadvantages include the slight insertion loss of the switch connector and the complexity of adding a component whose purpose is solely for testing.

[0005] Therefore, the need for a new configuration useful for measuring transmitter power level exists so the switch connectors can be eliminated from RF circuit board designs. SUMMARY

[0006] This summary is provided to introduce a selection of concepts in a simplified form as a prelude to the more detailed description that is presented later. The summary is not intended to identify key or essential features of the invention, nor is it intended to delineate the scope of the claimed subject matter.

[0007] In one embodiment, a radio-frequency connector interface board includes a first printed circuit board (110), at least one conductive contact (125) attached to the first printed circuit board (110), and an RF connector (115) attached to the first printed circuit board (110) having a center conductor (410) attached to the at least one conductive contact (125). The at least one conductive contact (125) is formed to make electrical contact with at least one contact pad (120) on a second printed circuit board (105).

[0008] The connector interface board has a first printed circuit board tab (305) that facilitates mounting to a chassis (130) providing support for the apparatus and the second printed circuit board (105). The first printed circuit board (110) is mounted orthogonally to the second printed circuit board (105). The at least one conductive contact (125) forms roughly a 90 degree angle for contact with the at least one contact pad (120) on the second printed circuit board (105). A chassis (130) provides support for the at least one conductive contact (125). The at least one conductive contact (125) is attached to the first printed circuit (110) by soldering to a trace (405) on the first printed circuit board (110).

[0009] In another embodiment, an assembly includes a first printed circuit board (110), at least one conductive contact (125) attached to the first printed circuit board (110), an RF connector (115) attached to the first printed circuit board (110) having a center conductor (410) of the RF connector attached to the at least one conductive contact (125), and a second printed circuit board (105) having RF circuitry and at least one contact pad (120).

[0010] The second printed circuit board (105) is mounted orthogonally to the first printed circuit board (110) such that the at least one conductive contact (125) of the first printed circuit board (110) makes mechanical contact with the at least one contact pad (120) on the second printed circuit board (105). The second printed circuit board (105) includes at least one antenna contact pad (120). The RF connector (115) is mated to an RF cable (155) to drive RF signals to an antenna (150). A chassis (130) supports the first printed circuit board (110) and the second printed circuit board (105). The second printed circuit board (105) is separably connected from the first printed circuit board (110). The at least one conductive contact (125) forms roughly a 90 degree angle for contact with the at least one contact pad (120) on the second printed circuit board (105). The chassis (130) provides support for the at least one conductive contact (125). The first printed circuit board (110) has a tab (305) that facilitates mounting to the chassis (130). The second printed circuit board (105) is absent a switch connector for testing of the second printed circuit board (110).

[0011] Additional features and advantages of the invention will be made apparent from the following detailed description of illustrative embodiments which proceeds with reference to the accompanying figures. It should be understood that the drawings are for purposes of illustrating the concepts of the disclosure and is not necessarily the only possible

configuration for illustrating the disclosure. Features of the various drawings may be combined unless otherwise stated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing summary of the invention, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the accompanying drawings, which are included by way of example, and not by way of limitation with regard to the claimed invention. In the drawings, like numbers represent similar elements.

[0013] Figure 1 illustrates a configuration relevant to the present disclosure;

Figure 2 illustrates a configuration of printed circuit board and interface board according to principles of the disclosure;

Figure 3A depicts a mounting scheme for an interface board;

Figure 3B depicts an interface board installed onto a chassis according to principles of the disclosure;

Figure 4A depicts an interface board before conductive contact attachment;

Figure 4B depicts a sheet metal contact pair before attachment;

Figure 4C depicts an interface board after conductive contact attachment;

Figure 5A depicts a signal side view of the interface board;

Figure 5B depicts a ground side view of the interface board;

Figure 6 A depicts a bottom side view of an RF PCB showing antenna contact pads;

Figure 6B depicts a bottom side view of an RF PCB showing metal conntact feet in contact with the antenna contact pads;

Figure 7A depicts antenna contact pad with respect to a chassis element;

Figure 7B depicts a single conductive contact with respect to an antenna contact pad; Figure 7C depicts two conductive contacts with respect to two antenna contact pads; and

Figure 7D depicts a complete interface board mounted on a chassis.

DETAILED DISCUSSION OF THE EMBODIMENTS

[0014] In the following description of various illustrative embodiments, reference is made to the accompanying drawings, which form a part thereof, and in which is shown, by way of illustration, how various embodiments in the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modification may be made without departing from the scope of the present invention.

[0015] This disclosure relates to a chassis-mounted antenna which has exposed metal contact pads on the printed circuit board (PCB) that hold the RF driver circuitry. This is in contrast with a board-mounted antenna configuration which would require switch connectors placed on the RF PCB for testing. In the disclosed configuration, an RF PCB having metal pads on the edge of the PCB may be manufactured without switch connectors. In the current disclosure, RF connection to metal pads on the RF PCB is assumed. The challenge is then to develop an architecture that accommodates transfer of RF signals from the antenna pads on the RF PCB and well as board level testing of RF PCB without switch connectors. The figures of the present disclosure describe embodiments of an RF interface board that accommodates an interconnection from the RF signal metal pad contacts on a RF PCB to an RF connector. The configuration supports RF PCB board level testing without switch connectors. The configuration also supports deployment of an antenna without connectors or cables on the RF PCB board.

[0016] Figure 1 depicts an electronic device 100 having at least two printed circuit boards. The electronic device is typical of modems, gateways, and set-top boxes, and the like that have RF components on printed circuit boards that are eventually connected to antennas for deployed operation. One PCB board in electronic device 100 is an RF PCB 105 that includes RF circuity chain components, such as RF drivers and receivers. Unique to RF PCB 105 is the cost-efficient lack of RF connector components for distribution and testing of RF signals. RF PCB 105 has antenna pads for the connection of an antenna element instead of on-board RF connectors. Thus, according to principles of the disclosure, an interface board 110 is used which can interface from the metal antenna pads on RF PCB 105 to RF connector 115. The advantages of such a configuration include connector simplicity of the RF PCB design, and simplicity of test access without the need for on-board switch connectors or RF cables. Another advantage is that the interface board 110 can be used in the electronic device 100 as an interface for an RF cable 155 to connect to an antenna 150. Note that the RF cable 155 is not connected to the RF PCB 105 where the RF circuitry is located. Instead, the RF cable 155 is connected to the interface board 110 via RF connector 115. The antenna 150 can be mounted either internally or externally to the electronic device 100 using RF cable 155.

[0017] Figure 2 depicts an assembly 200 as one embodiment which includes an RF PCB 105 and an interface board 110. The RF PCB has antenna contact pads 120, 121 which essentially eliminate the need for standard connectors (such as RF connectors) on the RF PCB 105. In the embodiment shown in Figure 2, the interface board 110 is a vertically mounted PCB. This produces an orthogonal mounting relationship between the interface board 110 and the RF PCB 105. The interface board 110 has at least one conductive contact 125. In one embodiment, two conductive contacts are used; one on each side of the interface board 110. Also referred to as a sheet metal contact 125, the conductive contact is used to connect the RF signal from the RF PCB 105 antenna contact pad 120 to the signal conductor of connector 115 using a trace of the interface board 110. In one embodiment, the signal conductor is a center conductor on the connector 115. Another contact, not shown in Figure 2, is used to connect the signal ground of the antenna pad 121 to an outer conductor of RF connector 115. In one embodiment, the signal ground antenna pad 121 is connected to the connector body of RF connector 115. Also shown in Figure 2 is a chassis 130 used to support the assembly 200. In one embodiment, the chassis is an insulator material and thus can be made of a plastic or other non-conducting material.

[0018] The configuration of Figure 2 exploits the fact that the antenna contact points 120, 121 are exposed and disconnected during any board level test using the RF PCB 105. In one embodiment, a vertically mounted interface board 110 with specially formed sheet metal contacts 125, 126 makes electrical and mechanical connection to the antenna contact pads 120, 121 on the RF PCB 105. The contacts 120, 121 are formed such that the characteristic impedance of the feed trace in the RF PCB 105 is maintained. In one embodiment, the impedance is 50 ohms. With a controlled impedance, the RF signal is transferred from the RF PCB 105 contact pads 120, 121 to the sheet metal contacts 125, 126 to the trace on the interface board going to the RF connector 115 with minimal insertion loss and minimal reflection. It should be noted that sheet metal contact 125 of Figure 2 and 126 of Figure 4B can be made of any conductive material. Thus, they are conductive contacts (125-126). Examples of material that can be used are copper, aluminum, gold, tin, or any conductive alloy. In one embodiment, the conductive contact, when part of PCB 110, is electrically connected to a trace on the PCB 110. Although referred to herein as sheet metal contacts 125-126 for convenience, one of skill in the art will recognize items 125-126 as being conductive contact 125-126. One implementation being a folded conductive item, such as a sheet metal contact. [0019] The RF signal exits the interface board 115 via a cable (not shown) connected to an RF connector 115 at the edge of the interface board 110. Simulations show the loss to be approximately 0.3 dB at 2.4 GHz and 1.1 dB at 6 GHz. The variance on the insertion loss is minimal making this a suitable method for measuring or transferring transmitter power at the board level. Thus, the need for a switch connector or any special component for the express purpose of testing transmitter power is eliminated.

[0020] Figure 3 A depicts one embodiment of the interface board 110 that has a tab 305 used for mounting. The chassis 130 has a surface 310 having a slot or groove which can accept the tab 305 and thus secure the interface board 110 in the chassis 130. Figure 3B shows an assembly of the interface board 110 mounted on the chassis 130. A sheet metal contact foot 315 is part of the sheet metal contact 125 (conductive contact 125). The foot 315 rests on the raised surface 320 of the non-conductive chassis 130 to provide support. The RF PCB 105 is shown not yet mounted in Figure 3B. Sheet Metal Contact 315 bends 90° along the surface 320 to permit wrapping under RF PCB 105 (not shown).

[0021] It can be appreciated that the configuration of Figure 3B can be used as a test fixture for testing RF PCBs. Thus, the configuration of Figure 3B can be used in the assembly shown in Figure 2 where the RF PBC 105 is separable from the interface board 110 for test or replacement purposes.

[0022] Figure 4A shows an image of the interface board 110 with a connector 115, but without the sheet metal contacts 125, 126 attached. Figure 4B shows one embodiment of sheet metal contact 125 (conductive contact 125) and 126 showing sheet metal contact foot portions 315 and 316. One method of attaching the sheet metal contacts to the RF trace 310 involves soldering. Figure 4C shows the result of soldering the sheet metal contact 125 to RF copper trace 405. This completed sub-assembly of the interface board 110 thus allows an RF signal connection from the sheet metal contact foot 315 to the connector conductor 410 via trace 405. In one embodiment, the connector 115 is an RF connector, and the signal connector 410 of the connector 115 is a center conductor 410.

[0023] Figure 5 A shows a signal side view of the interface board 110. The RF PCB 105 sits on top of the sheet metal contact (conductive contact) foot 315. The metal contact foot 315 is supported by the non-conductive chassis surface 320. Thus, the metal contact foot 315 is sandwiched between the RF PCB 105 and the chassis surface 320. Although not shown for clarity, the metal contact foot 315 makes physical (mechanical) contact with the antenna contact pad 120 on the RF PCB 105. The metal contact foot 315, part of conductive contact 125, thus makes direct mechanical and electrical contact with the antenna pad 120 to allow an RF signal to flow between the center conductor 410 and the antenna contact pad 120 of RF PCB 105.

[0024] Figure 5B shows a ground side view of the interface board 110. The RF PCB 105 sits on top of the sheet metal contact (conductive contact) foot 316. The metal contact foot 316 is supported by the non-conductive chassis surface. Thus, the metal contact foot 316 is sandwiched between the RF PCB 105 and the chassis surface. Although not shown for clarity, the metal contact foot 316 makes physical contact with the antenna contact pad 121 on RF PCB 105. The metal contact foot 316, part of metal sheet contact 126, thus makes direct contact with the antenna pad 121 to allow a ground signal connection between the antenna contact pad 121 and the interface board 110. In one embodiment, the ground signal pad 121 can make a connection to an outer conductor of RF connector 115. In another embodiment, the configuration of Figure 5B can make a connection from an antenna pad 121 on RF PCB 105 to an RF connector case 505 via sheet metal contact 126. Shown in Figure 5B is the ground signal side of a copper plated interface board 110 allowing a connection between the soldered sheet metal contact 126 to the connector case 505.

[0025] Figure 6A shows a bottom side view of an RF PCB 105 showing antenna contact pads 120 and 121. The view of Figure 6A makes invisible the sheet metal contacts 315 and 316. The Figure 6A view shows the orthogonal relationship between the RF PCB 105 and the interface board 110. Figure 6B shows the bottom side view of the RF PCB 105 showing antenna contact pads 121 and 121 covered by sheet metal contact feet 315 and 316 respectively. The Figure 6B view shows the orthogonal relationship between the RF PCB 105 and the interface board 110.

[0026] Figure 7A shows a detail view of the contact pads 120 and 121 before assembly. The contact pads are shown in relation to raised surface 320 of the nonconductive chassis 130. Figure 7B shows details of contact pad 120 and the relative position of metal contact 125. In Figure 7B, the interface board 110 and contact 126 are rendered invisible. Figure 7C shows the details of contact pads 120 and 121 and the relative positions of metal contacts 125 and 126 respectively. In Figure 7C, the interface board 110 is rendered invisible. Figure 7 D shows the ground signal connection side of the interface board 110 in an assembled configuration. Figure 7D shows the assembly details of an interface board 105 having a sheet metal (conductive) contact 126 mounted onto a slot in surface 310 of chassis 130. Antenna pad 121 of RF PCB 110 sits atop a sheet metal foot (not shown) resting on raised surface 320. [0027] Although specific embodiments are shown in the above listed figures, the principles of interfacing with an RF PCB having only antenna pads instead of connectors or cable interfaces can be used with variation that would be within the scope of the appended claims.

Claims

Claims:

1. An apparatus comprising:

a first printed circuit board (110);

at least one conductive contact (125) attached to the first printed circuit board (110); and

a connector (115) attached to the first printed circuit board (110) having a conductor (410) attached to the at least one conductive contact (125);

wherein the at least one conductive contact (125) is formed to make mechanical connection with at least one contact pad (120) on a second printed circuit board (105).

2. The apparatus of claim 1, wherein the apparatus has a first printed circuit board tab (305) that facilitates mounting to a chassis (130) providing support for the apparatus and the second printed circuit board (105). 3. The apparatus of any of the preceding claims, wherein the first printed circuit board (110) is mounted orthogonally to the second printed circuit board (105).

4. The apparatus of any of the preceding claims, wherein the at least one conductive contact (125) forms roughly a 90-degree angle for contact with the at least one contact pad (120) on the second printed circuit board (105).

5. The apparatus of any of the preceding claims, wherein a chassis (130) provides support for the at least one conductive contact (125). 6. The apparatus of any of the preceding claims, wherein the at least one conductive contact (125) is attached to the first printed circuit (110) by soldering to a trace (405) on the first printed circuit board (110).

7. An assembly (200), the assembly comprising:

a first printed circuit board (110);

at least one conductive contact (125) attached to the first printed circuit board (110); a connector (115) attached to the first printed circuit board (110) having a conductor (410) of the connector connected to the at least one conductive contact (125); and a second printed circuit board (105) having circuitry and at least one contact pad

(120);

wherein the second printed circuit board (105) is mounted orthogonally to the first printed circuit board (110) such that the at least one conductive contact (125) of the first printed circuit board (110) makes mechanical contact with the at least one contact pad (120) on the second printed circuit board (105).

8. The assembly of claim 7, wherein a second printed circuit board (105) comprises at least one antenna contact pad (120).

9. The assembly of any of claims 7-8, wherein the connector (115) is mated to a cable (155) to drive signals to an antenna (150).

10. The assembly of any of claims 7-9, further comprising a chassis (130) that supports the first printed circuit board (110) and the second printed circuit board (105).

11. The assembly of any of claims 7-10, wherein the second printed circuit board (105) is separably connected to the first printed circuit board (110). 12. The assembly of any of claims 7-11, wherein the at least one conductive contact (125) forms roughly a 90-degree angle for contact with the at least one contact pad (120) on the second printed circuit board (105).

13. The assembly of any of claims 10-12, wherein the chassis (130) provides support for the at least one conductive contact (125).

14. The assembly of any of claims 10-13, wherein the first printed circuit board (110) has a tab (305) that facilitates mounting to the chassis (130). 15. The assembly of any of claims 7-14, wherein the second printed circuit board (105) is absent a switch connector for testing of the second printed circuit board (110).

16. An electronic device (100) comprising an apparatus or assembly according to any preceding claim. An electronic device according to claim 16 wherein the electronic device is a gateway or a set-top box.