Abstract:
A RF interconnect comprising a dielectric resonator is disclosed. The dielectric resonator may be included in an interconnect housing. The dielectric resonator includes metalized side surfaces useful for securing the dielectric resonator in an aperture formed in the interconnect housing. The dimensions or material selected for the dielectric resonator may be predetermined to enable the dielectric resonator to operate as a filter or waveguide, as desired.

Description:
FIELD OF INVENTION 
     The invention relates to a system and method for RF interconnects, and more particularly a system and method for a connectorless RF interconnect. 
     BACKGROUND OF INVENTION 
     Active antenna arrays are expected to provide performance improvements and reduce operating costs of communications systems. An active antenna array includes an array of antenna elements. In this context, the antenna element may be viewed as being a transducer which converts between free-space electromagnetic radiation and guided waves. In an active antenna array, each antenna element, or a subgroup of antenna elements, is associated with an active module. The active module may be a low-noise receiver for low-noise amplification of the signal received by its associated antenna element(s), or it may be a power amplifier for amplifying the signal to be transmitted by the associated antenna element(s). The active modules, in addition to providing amplification, ordinarily also provide amplitude and phase control of the signals traversing the module to point the beam(s) of the antenna in the desired direction. In some arrangements, the active module also includes filters, circulators, and/or other functions. 
     Carefully designed interconnects are needed to transmit a RF signal between two electronic modules or assemblies, such as printed circuit boards. In high-powered RF electronics applications, including RF power amplifiers for cellular base stations, a relatively high amount of energy is transmitted through the interconnect. Signal attenuation may occur as a result of radiation of energy into the air or reflections caused by the signal transfer properties of the interconnect. Therefore, one important characteristic of interconnect assemblies is good signal transfer properties with minimal signal attenuation. Other important characteristics are low cost and ease of manufacture. 
     Known prior art interconnects are generally mechanical interconnects requiring some form of mechanical coupling to ensure proper RF signal transmission. Conventional methods of constructing interconnects include using blind mate connector systems, metal ribbon connections, and printed circuit pin and spring socket systems. Each of these approaches has shortcomings which include bulkiness in size, the need for manual labor which increases costs, difficulty in manufacturing, and insufficient shielding. 
     One prior art interconnect that has gained popularity is known as a “Gilbert”™ contact, which consists of a male pin that is soldered or brazed to the next level assembly. The mating contact is a female pin which opens up to allow a male pin to slide into it. Although widely accepted by the industry, it requires a pin to be soldered or brazed at the next level of interconnect, which increases the overall cost of the system. 
     Another typical example of a prior art interconnect is described in U.S. Pat. No. 4,957,456. The &#39;456 patent describes a self-aligning blind mate RF push-on connector. One problem with the connector described in the &#39;456 patent is its bulkiness, which makes the connector unsuitable for systems with space limitations. 
     Therefore, a need exists for a RF interconnect that reduces signal attenuation and costs associated with the prior mechanical interconnects. It would therefore represent an advance in the art to provide a RF connector which does not require any special mating provisions except for a pad area. 
     SUMMARY OF INVENTION 
     The present invention addresses many of the shortcomings found in the prior art, especially in the area of RF interconnects. In one aspect, the present invention uses a dielectric resonator in the RF interconnect. The invention takes advantage of the characteristics of dielectric resonators to have very low dielectric loss at microwave frequencies, and to provide small controllable temperature coefficients of the resonance frequency over a useful operating range. The invention teaches a RF interconnect that includes a dielectric resonator that does not use mechanical couplings. 
     In another aspect, the invention uses the dielectric resonator in a RF interconnect to provide filtering properties. The resonance frequency of the dielectric resonator interconnect is controllable by pre-selecting the dielectric resonator material. In this way, the dielectric resonator may be configured to provide filtering properties as desired. 
     In yet another aspect, the invention uses a dielectric resonator in a RF interconnect as a dielectric loaded circular waveguide. That is, the invention may be used to guide electromagnetic waves by preconfiguring, for example, the cross-sectional dimensions of the dielectric resonator interconnect, the type of dielectric material inside the dielectric resonator interconnect, and the frequency of the circuit. 
     In one particular embodiment, the RF interconnect disclosed includes a dielectric resonator disposed between two circuit elements of an antenna array. The dielectric resonator provides a low loss pathway for providing RF signals between the two circuit elements. For example, the dielectric resonator may place an element and a microstrip, two microstrips, or two circuit elements in communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, wherein like numerals depict like elements, illustrate exemplary embodiments of the present invention, and together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is an exemplary depiction of a prior art dielectric resonator useful with the present invention; 
         FIG. 2  is a depiction of an exemplary RF interconnect housing useful with the present invention; 
         FIG. 3  is a depiction of portion of an exemplary RF interconnect housing useful with the present invention; 
         FIG. 4  is a depiction of an exemplary circuit in which the present invention may be used; and 
         FIG. 5  is an exemplary depiction a cross-sectional view of circuit in which the present invention may be used. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides a connectorless RF interconnect including a metalized dielectric resonator. Dielectric resonators are commonly used in filters, oscillators and other electronic devices. Although different forms of dielectric resonators are commercially available, the dielectric resonators that are most often used have the form of a short circular straight-wall cylinder which may have or may not have an axially-extending hole in the center of the cylinder and a length-to-radius ratio which is often close to one. 
       FIG. 1  illustrates an exemplary dielectric resonator (“DR”) DR  100  useful with the present invention. DR  100  is of the short circular straight-wall cylinder type, having a first substantially planar circular upper surface  102  and a second substantially planar circular bottom surface  104 . Upper surface  102  and bottom surface  104  are joined by a cylindrical straight-wall side surface  106 . As shown, the radius r of the upper surface  102  (and the radius r of the bottom surface  104 ) may be in one to one ratio relationship with the length L of the cylindrical straight-wall side surface  106 . 
     In one exemplary embodiment of the invention, DR  100  is metalized on a portion of cylindrical straight-wall side surface  106 . In this context “metalized” means that side surface  106  is coated with a thin metal film that is useful for bonding side surface  106  to another surface. Suitable metal films which are useful with the invention include gold, silver, tin, lead, nickel, copper or any other metal permitting DR  100  to be affixed to another surface. 
     For coupling DR  100  to a transmission line, DR  100  may be interposed within an interconnect housing.  FIG. 2  depicts a suitable interconnect housing  300  useful with the present invention. In general, interconnect housing  300  may be any structure capable of supporting the connection of one electrical component to another electrical component, which additionally aids in the transmission of RF signals therebetween. Exemplary interconnect housing may be a metal, ceramic, Teflon or other material suitable for electronic or microwave circuit enclosures. Interconnect housing  300  may be any housing capable of supporting DR  100  such that DR  100  may receive and/or transmit RF signals from one electrical circuit element to another. Interconnect housing  300  is configured to receive and fix DR  100  in a location for enabling RF transmission. As such, interconnect housing  300  may be composed of any material providing suitable rigidity for holding DR  100  in place. Additionally, interconnect housing  300  may have a first surface  302  which may be planar, conical or other suitable shape facilitating connection of DR  100  to electrical components. Alignment features such as alignment pins or optical alignment targets as are known may be added to the surface  302  of the interconnector housing  300  to a RF interface discussed below. 
     In some instances, it may be desired to transmit one or more RF signals to a plurality of electrical components. In that regard, interconnect housing  300  may be operable to receive and fix a plurality of DR  100 . In such an instance, a plurality of DR  100  may be in communication with a plurality of electrical components. For example, interconnect housing  300  is depicted having a first surface  302  having a plurality of interconnect locations  304  for receiving a plurality of DR  100 . In this instance, each interconnect location  304  is configured to receive a DR  100  and fix DR  100  for use in transmitting a RF signal. 
     The metalized DR  100  may be affixed to interconnect housing  300  using conventional solder conductive or nonconductive epoxy or other suitable affixing agent, operable to provide structural support and/or to hermetically seal DR  100  in interconnect housing  300 . The solder may be placed on the RF interconnect housing  300  in the interconnect location  304  for eventual placement of DR  100 . To aid in holding DR  100  in a fixed position, interconnect location  304  may be a recess suitably shaped for receiving DR  100 . DR  100  may be positioned inside the recess such that upper surface  102  and bottom surface  104  are in communication with an electrical circuit element. Upon being positioned inside or at interconnect location  304 , the DR  100  is held in a fixed position using any one of the affixing agents noted above. DR  100  may be placed at the RF interconnect location  304  using any conventional machine or robot useful for fixing circuit components for a RF interconnect. 
       FIG. 3  depicts a closer view of DR  100  positioned at interconnect location  304  showing DR  100  held in place. As shown, DR  100  is affixed at interconnect location  304  using a suitable affixing agent  402 . In the example shown, interconnect housing  300  includes a substantially planar surface  302  such that surface  302 , DR  100  and upper surface  102  are substantially in the same plane. In one exemplary embodiment, upper surface  102  may be parallel to planar surface  302 , but upper surface  102  may lie in a different plane than planar surface  302 . 
     The diameter of interconnect location  304  may be slightly greater than the diameter of upper surface  102  such that DR  100  may be positioned inside interconnect location  304 . In one exemplary embodiment, the diameter of interconnect location  304  may be substantially similar to the diameter of upper surface  102 , such that DR  100  may be positioned in interconnect location  304  with application of minimal force along the axial direction to interconnect location  304 . 
     As shown, the affixing agent  402  may be positioned between the perimeter of interconnect location  304  and the perimeter of upper surface  102 . In one exemplary embodiment, the affixing agent  402  may be positioned abutting side wall  106  prior to positioning DR  100  at interconnect location  304 . In another exemplary embodiment, the affixing agent  402  may be positioned in a recess formed at interconnect location  304  prior to positioning DR  100  at interconnect location  304 . In yet another exemplary embodiment, DR  100  may be positioned at interconnect location  304  prior to positioning the affixing agent  402  in proximity to DR  100  and interconnect location  304 . 
     With brief reference to  FIG. 4 , the interconnect housing  300 , is illustrated as a filter and is shown in the ordinary environment in which it may be found. Interconnect housing  300  may be used in any conventional circuit requiring a RF interconnect and filtering. As illustrated, interconnect housing  300 , including DR  100 , is depicted providing filtering with respect to a MMIC  504 , via a microstrip  502 . Microstrip  502  is configured to place MMIC  504  in electrical communication with DR  100 , as described below. In this instance, where a plurality of DR  100  are used, the plurality DR  100  shown in  FIG. 2 , are installed in circuit  500  with the upper surface  102  of the plurality of DR  100  in electrical contact with microstrip  502  via RF interface  510 . In this regard, interconnect housing  300  is depicted as being hidden from view by RF interface  510  (interconnect housing  300  shown in broken lines in  FIG. 4 , underlying RF interface  510 ). 
     Interconnect housing  300  is in electrical communication with a RF interface  510 , which is in electrical communication with microstrip  502 , which is in electrical communication with MMIC  504 , as described more fully below. MMIC  504  may be in further contact with later circuitry (not shown) via conductors  506  for providing and receiving signals therefrom. 
     Although the circuit  500  is depicted as having RF interface  510 , microstrip  502 , and MMIC  504 , the circuit  500  may include any circuit elements as are well known to use RF interconnects. Thus, microstrip  502 , MMIC  504 , and conductors  506  may be any conventional similar elements. 
     Referring now to  FIG. 5 , DR  100  is shown used as a RF interconnect in the exemplary circuit  500 . More particularly,  FIG. 5  depicts a portion of  FIG. 4  in cross-section, wherein filter housing  300  connects with microstrip  502 , and wherein a single one of the plurality of DR  100  is shown in electrical communication with microstrip  502 . Conductors  506  may be in communication with MMIC  504  for providing biasing and control signals thereto. Microstrip  502  may send RF signals to DR  100  via conductors  506 . As shown, interconnect housing  300  includes a recess  608  for including DR  100 . The dimensions of the recess  608  may be chosen to closely follow the dimensions of DR  100 . In the example shown, DR  100  is substantially cylindrical in shape. Thus, recess  608  is depicted as being substantially cylindrical in shape such that the recess generally follows the shape of the DR  100 . Additionally, recess  608  may include recess side walls  612  configured to closely follow the shape of DR  100 . Moreover, in one exemplary embodiment, the dimensions of recess  608  are such that DR  100  may be securely fitted within recess  608 . In another exemplary embodiment, like the one depicted in  FIG. 5 , recess  608  is dimensionally slightly larger than DR  100 . More particularly, recess  608  is of sufficient size that free space may be included between DR  100  and the recess side walls  612 . The free space may be sufficient for including an affixing agent  402 . In some instances, it is desirable to hermetically seal the DR  100  within filter housing  300 . In this regard, DR  100  may be fixed in recess  608  using a paste, such as, for example, solder in similar manner as described above. The affixing agent  402  may be positioned in recess  608  for holding DR  100  in position. Additionally, the upper surface  102  of DR  100  is exposed so that it may be placed contact with later circuitry, described below. 
     RF interface  510  may include a transmission path  604  in communication with microstrip  502  for transmitting signals between the microstrip  502  and DR  100 . Transmission path  604  may include a planar pad of conducting material  608 , which is placed in substantial contact with the upper surface  102  of DR  100 . Notably, although the conducting material  608  is described as planar, conducting material  608  may be configured as desired to effectuate communication with upper surface  102 . In this way, signals may be transmitted between DR  100  and microstrip  502 , via the pad of conducting material  608  and the transmission path  604 . 
     DR  100  may be configured as a filter as described above, by pre-selecting the dimensions and composition of DR  100 . Thus, in operation, DR  100  may be configured to provide filtering at a predetermined resonance. Methods for selecting the dimensions and composition of dielectric resonators is well known, and any conventional method may be used. 
     Circuit  500  may receive a signal at filter housing  300  and provide the signal to DR  100 . DR  100  may filter the signal and provide the signal to microstrip  502  via pad  606  and transmission line  604 . Microstrip  502  may then provide the signal to MMIC  504  or some other suitable connected circuit element. 
     In another exemplary embodiment, DR  100  may be used as a waveguide in a waveguide structure. To configure DR  100  for use in a waveguide structure, the dimensions of DR  100  may be chosen to allow electromagnetic propagation but not cavity resonance, as is done with the filtering interconnect 
     The present invention has been described above with reference to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present invention. For example, the various operational steps, as well as the components for carrying out the operational steps, may be implemented in alternate ways depending upon the particular application or in consideration of any number of cost functions associated with the operation of the system (e.g., various of the steps may be deleted, modified, or combined with other steps). Alternatively, additional steps (e.g., solder paste placement steps) may be added to illustrate alternate embodiments of the invention. In addition, the various circuit component placement systems disclosed herein may be modified or changed to accommodate additional pucks or circuit components as may be desired. The changes and/or modifications described above are intended to be included within the scope of the present disclosure, as set forth in the following claims.