Patent Application
20120163635
The disclosure herein relates to the field of small broadband antennas, and more particularly to helical antennas that may be used with wireless microphones that transmit in the UHF band range.
It may be desirable to implement a small, robust, and inexpensive antenna that is easy to assemble in one or more of various wireless applications such as wireless microphones, computers, mobile devices, and other wireless transmission devices.
U.S. Pat. No. 7,301,506 to Kenkel et al. (“Kenkel”), which is incorporated herein fully by reference, discloses one such example. Kenkel discloses a helical antenna assembly formed by taking a non-metallic tape and placing a metallic tape strip diagonally onto the non-metallic tape. A dielectric core is then wrapped with the tape. An electrical connector and a central conductor that is located in the center of the dielectric core contact the metallic tape strip. One or two tabs on the tape are bent over the ends of the dielectric core to prevent the tape assembly from separating from the dielectric core. Eyelets are also affixed to the center conductor to pin the tabs. The pitch and width of the conductive portion of the tape assembly can be altered to obtain the desired electrical characteristics when the tape assembly is wrapped around the dielectric core.
In one exemplary embodiment, the present disclosure contemplates an antenna assembly comprising a dielectric core with antenna tape having a conductive portion wrapped around the dielectric core, and a printed circuit board that may extend from a chassis. The printed circuit board and the conductive portion on the tape can be electrically coupled.
In another exemplary embodiment, the present disclosure contemplates a wireless microphone assembly comprising a sound capsule, a chassis, and an antenna assembly connected to the chassis. The antenna assembly comprises a dielectric core which extends into the chassis. An antenna tape comprising a conductive portion is wrapped around the dielectric core. A printed circuit board may extend from the chassis, and at least a portion of the printed circuit board is located in the chassis. The printed circuit board and the conductive portion on the tape are electrically coupled.
In another exemplary embodiment, the present disclosure contemplates a method for forming an antenna comprising wrapping an antenna tape comprising a conductive portion around the dielectric core, mounting a printed circuit board to a chassis at a point located away from the chassis, and electrically coupling the printed circuit board and the conductive portion.
Other objects and features of the invention will become apparent by reference to the following description and drawings.
The present disclosure is illustrated by way of example and not limited in the accompanying figures:
In the following description of various example structures in accordance with the present disclosure, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration of various structures in accordance with the invention recited in the claims. Additionally, it is to be understood that other specific arrangements of parts and structures may be utilized and structural and functional modifications may be made without departing from the scope of the present disclosure. Also, while the terms “top” and “bottom” and the like may be used in this specification to describe various example features and elements of the disclosure, these terms are used herein as a matter of convenience, e.g., based on the example orientations shown in the FIGS. and/or the orientations in typical use. Nothing in this specification should be construed as requiring a specific three dimensional or spatial orientation of structures in order to fall within the scope of the claims.
A conductive element such as a coupling wire 106 or flex cable (not shown) may electrically couple a conductive portion 122 of the antenna tape 120 to the PCB 110, which acts as a strain relief connection interface between the two components. A ground element, which can be a screw 112, may be used to connect the PCB 110 to the chassis 104 near the wire 106 to allow for a proper ground reference.
The dielectric core 130 can mount near the PCB 110 and in the chassis 104. The PCB 110 extends past a chassis wall 105 and into an opening 144 of a handheld microphone. Additionally, a shock absorbing member 146 comprising a small piece of shock absorbing foam can be placed between the inside area of the antenna cover 114 and the end of the dielectric core 130 to provide additional shock absorption capability to absorb shock energy during drop impact if the antenna is mishandled. In one exemplary embodiment, the shock absorbing member 146 can be formed of a poron pad. The coupling wire 106 provides strain relief between the PCB 110 and the antenna 100. In particular, the coupling wire 106 can be provided with extra length so as to provide additional slack in the wire such that it can freely move during drop impact without being severed. This enhances the shock absorption capabilities of the antenna 100 if it is dropped or mishandled, or if the antenna 100 is otherwise moved relative to the PCB 110.
In order to properly feed the antenna 100, the radio frequency (“RF”) signal needs to be properly referenced to a ground. The ground screw 112 can be added between the chassis 104 and the PCB 110 to act as the ground reference.
As shown in
The dielectric core 130 has a first cylindrical portion 132 and a second elongated portion 134. The first cylindrical portion 132 is configured to receive the antenna tape 120, and the second elongated portion 134 is configured to be inserted into the chassis 104 of the microphone. The first cylindrical portion 132 may have a circular cross section for receiving the antenna tape 100. The second elongated portion 134 may have a D-shaped cross section or a partially curved profile with a flat surface for interfacing with the L-shaped tab 116 of the chassis 104 and the PCB 110 such that the dielectric core 130 does not interfere with the PCB 110 during assembly. In particular, the D-shaped profile corresponds to the inside profile of the chassis 104 formed by the opening 144 in the chassis 104, the tab 116, and the PCB 110, and allows the dielectric core 130 to be placed in the chassis 104 around the tab 116 and PCB 110. The addition of the second elongated portion 134 provides good shock absorption properties to the antenna 100. The second elongated portion 134 also has an opening 133 which may extend throughout the length of the second elongated portion 134, and to the first cylindrical portion 132. The second elongated portion 134 is also provided with two holes 136 for securing the dielectric core 130 and the antenna cover 114 to the chassis 104 via one or more screws 140. A notch 138 in the second elongated portion 134 provides a recess which provides clearance between an end of the ground screw 112 and the dielectric core 130. This permits the ground screw 112 to fully extend past the tab 116 of the chassis 104 without contacting the dielectric core 130, such that the screw 112 does not impact the positioning of the dielectric core 130 relative to the PCB 110. The two holes 136 can be formed suitable for mating to screws 140, which can be self tapping (shown in
Additionally, the dielectric core 130 can be modified into other shapes and configurations. For example, as shown in
As shown in
As shown in
An alternative embodiment is shown in
In the embodiments depicted in
In another alternative embodiment shown in
In an alternative embodiment, the antenna 100 could be formed on a piece of flexible PCB or be formed as part of the PCB 110 and wrapped onto the dielectric core 130 after the PCB 110 is assembled into the chassis 104. In particular, since the conductive portion 122 on the antenna tape 120 is just a trace of specific length and pitch, it could be fabricated as part of the PCB 110. In this embodiment, an adhesive backer could be added to the antenna tape 120 to allow for it to be wrapped onto the dielectric core 130. This would eliminate the solder operations associated with connecting the wire 106 to the PCB 110 and the conductive portion 122 and their associated costs but may add costs due to PCB material utilization.
In addition, both the first conductive element 123C, which forms an upward helical wrap in a first direction and the second conductive element 125C, which forms a downward helical wrap in the opposite direction will both be terminated on the RF feed from the PCB 110. Both the first conductive element 123C and the second conductive element 125C can be connected to the RF feed on the PCB 110 in operation, which is different than the embodiments shown in
To assemble the antenna, the dielectric core 130 is wrapped with the antenna tape 120. The PCB 110 is next secured to the L-shaped tab 116 of the chassis 104 by the screw 112. When the ground screw 112 is installed, it compresses an electrically conductive area on the PCB 110 against an electrically conductive area on the L-shaped tab 116 where the paint or finish has been masked, forming an electrical ground connection to provide RF grounding between the PCB 110 and the chassis 104. In order to improve the contact between the PCB 110 and the chassis 104, a solder mask can be removed near the screw hole and a paste can be added to increase the contact area and consistency of the ground reference. The coupling wire 106 or flex cable can then be soldered to the PCB 110 with either a copper pad or a copper-plated through hole on the PCB 110. The wire 106 or flex cable can then be soldered to the conductive portion 122 on the antenna tape 120. Next the dielectric core 130 is inserted into the chassis 104 and the antenna cover 114 is placed over the dielectric core 130. Both the dielectric core 130 and the antenna cover 114 are secured to the chassis 104 by two self-taping screws 140 that are inserted through the antenna cover 114 and into the holes 136 in the second elongated portion 134 of the dielectric core 130.
In an alternative exemplary embodiment, a rigid-flex can be used to extend from the PCB 110 and the end of the rigid-flex can be plated with copper. This plated rigid flex is then soldered directly to the conductive portion of the antenna removing the necessity of the coupling wire 106 and, therefore, eliminates having to solder the coupling wire 106 or flex cable to the antenna 100 and the PCB 110.
The antenna embodiments disclosed herein may achieve a 13% fractional bandwidth over 470-950 MHz with tuning by changing the conductor length while fitting into a small microphone chassis. The embodiments disclosed herein can be implemented in any future handheld wireless device, including but not limited to, devices operating in a similar frequency band that utilize a metal chassis and an antenna cover.
The reader should understand that these specific examples are set forth merely to illustrate examples of the invention, and they should not be construed as limiting the invention. Many variations may be made from the specific structures described above without departing from this invention.
While the invention has been described in detail in terms of specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and methods. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims.
