Wave transmission lines and networks – Plural channel systems – Nonreciprocal gyromagnetic type
Reexamination Certificate
2000-05-12
2002-01-08
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Nonreciprocal gyromagnetic type
C333S024200, C361S818000
Reexamination Certificate
active
06337607
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
The increased demand from the communication industry to provide greater channel capacity coupled with the increased power requirements has exposed a condition within RF structures referred to as Intermodulation Distortion (IMD). This condition occurs when non-linearity within the structures, especially in their lead portions, distort the waveform resulting in generation of the other frequencies which can effectively block the channel. In other words, the distorted waveform consists of the desired fundamental plus a decaying series of related harmonics that, in themselves, interact with other carriers present on the transmission line. Intermodulation signals grow rapidly with power, and power tends to increase. In cellular phone communications, for example, maximum emission power can be as high as 30 Watts. In some applications it can be even 50 Watts and over. The reduction of nonlinear intermodulation noises is therefore of crucial importance, not only to improve the quality of signals, but also to allow fewer radio stations to be distributed in the transmission network. The above is the first aspect that should be taken into consideration in isolator/circulator design.
The second aspect is a body mechanical structure, particularly leads for connecting the ferrite isolator/circulator disposed inside the body to signal transmission lines outside the body. With huge applicability of ferrite isolators/circulators in microwave industry, the great importance is ease of installation and subsequent progression into automated placement. For an automated pick and place method to be used in production, the following requirements should be met: (a) robust structure of the body and contacts of the device, and (b) complanarity of the contact leads with the bottom surface of the body.
Structures that were intended to conform to both aspects mentioned above are known. According to Jussaume and Paquette teaching (U.S. Pat. No. 6,011,449), the leads (electrical conductors) for the passive device extend from openings in the body of the structure to substantially rigid supports. The conductors are positioned above said support and are electrically connected to contacts that are secured in apertures formed in the supports. For isolating the contacts from the supports a dielectric material is disposed on perimeter of the contacts. Those contacts go through the supports and exposed at bottom surfaces thereof. Bottom surface of the contacts is substantially coplanar with the bottom surface of the body. The body is metal; a ferrite isolator/circulator is disposed inside the body.
In the known structure, each conductor connecting the device disposed inside the body to a transmission line located outside the body goes via (a) opening in the body, (b) portion of the support, and (c) dielectric inside the aperture in the support. In order to avoid IMD all those three segments of the conductor's path should have the same impedance (usually 50 Ohms) and minimal mechanical imperfections. However, meeting these requirements with the known structure is problematic. The body is formed of two parts: a housing and a cover. In order to keep given impedance in segment (a), location of the conductor relative to the housing and the cover should be precisely defined. Considering a structure comprising a very thin conductor (usually 0.005″ thick) in the air within a rectangular opening formed by two sheet metal parts, some non-linearity deem inevitable. In segment (b) the same thin conductor located in the air above sheet metal support. In operation, the conductor and the support produce capacitance that is portion of the impedance. Any variations in distance between the conductor and the support lead to variations in capacitance and, in turn, in impedance. And, at last, a transition from segment (b) to segment (c) and imperfections in the assembled segment (c) can also lead to non-linearity.
There is one more aspect of the structure that should be taken into consideration: electrical arcing. With high power, the probability of arcing between a conductor in the air and metal ground is also high due to relatively low permitivity of the air (versus that of a dielectric material).
Another aspect: the necessity for the known structure to have openings in the housing for conductors in the air to go through. In operation, the RF field produced by the ferrite isolator/circulator disposed inside the structure may freely emit outside through those openings. The emission becomes more important with power. The openings also affect rigidity of the structure.
Accordingly, what is needed is a structure for ferrite isolator/circulator having more homogeneous construction of the leads to transmission lines of an outside system with no or minimum portions of the conductors in the air. Such a structure will enable to minimize IMD and probability of arcing in high power ferrite devices. In combination with the homogeneous structure of the leads, a robust and truly surface mount contact assembly that enables fully automated placement and soldering is also needed. A closed structure that minimizing RF field emission into environment is also needed.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a structure having substantially homogeneous leads that provide minimum non-linearity connection from a ferrite isolator/circulator disposed inside the structure to a signal transmission line disposed outside the structure. The structure according to the present invention comprises a housing, a cover and plurality of leads. The housing having central substantially flat round portion, peripheral portion, bottom and top surfaces, and slots is a base portion of the structure. The housing further comprises supports extended from the peripheral portion to receive printed circuit boards (PCBs) and tabs to receive the cover. The housing and the cover are metal. The slots are made in the supports and partially extended into the central portion of the housing. The PCBs are snugly inserted in the slots and secured in them by a gluing compound (epoxy, for example). The bottom surface of the housing is coplanar with the bottom surface of the PCBs. The supports are bent a little up and go diagonally on both sides of each PCB from its bottom surface to its top surface, mechanically reinforcing the PCB. The supports and the PCBs together constitute leads. Because of the bent supports the bottom surface of the PCBs has better access for soldering to a signal transmission line. The tabs are extended from the peripheral portion of the housing, and bent up to approximately 90 degrees. Each tab has a dimple protruding outward the housing. The cover comprises a saucer-like portion and a skirt having holes to receive the dimples, and notches to receive the PCBs. The tabs are located inside the cover, the skirt makes edge contact to the peripheral portion of the housing, and the notches in the cover make contact to the PCBs on their top surface and side portion. The dimples protrude into holes in the cover and lock it in place. The ferrite isolator/circulator is disposed on the top surface of the central portion of the housing and is held in place by the saucer-like portion of the cover. This portion provides some spring action causing the ferrite isolator/circulator to be pressed in place between the cover and the housing. The slots in the housing and, accordingly, the PCBs are extended into the central portion up to the ferrite isolator/circulator.
All PCBs in this structure are identical. Each PCB comprises a ground plane and a signal transmission line on both top and bottom surface. Side portions are bare dielectric. On the top surface of the PCB the signal line starts from the ferrite isolator/circulator and stops within the cover near its skirt, where it is connected by a printed through hole (PTH) to the signal line on the bot
Bettendorf Justin P.
Renaissance Electronics Corporation
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