Patent Description:
As is known in the art, quadrature couplers are used in a variety of microwave circuits to split an input signal into a pair of output signals, usually with equal magnitudes, that are ninety degrees apart in phase. Examples of such quadrature couplers are an embedded stripline broadside coupler or a topside quadrature coupler, such as a Lange or hybrid (branchline) splitter. One use of quadrature couplers is to impedance match pairs of devices. The devices are arranged so that reflections from them are terminated in a load that is isolated from the quadrature coupler's input because of the <NUM> degree (quadrature) phase difference.

As is also known in the art, prior art quadrature couplers are integrated into a larger board that has many functions. As such, the design such as the degree of coupling, is not easy alterable. An internal coupling structure in surface mount coupler is known from <CIT>. A HF coupler or Hf power splitter, especially a narrow-band and/or 3dB coupler or power splitter is known from <CIT>. A strip line coupler is known from <CIT>. Quasi-ideal multilayer two- and three-strip dimensional couplers for monolithic and hybrid MIC's are known from <NPL>.

<CIT> describes a multilayer coupled-lines directional coupler of the quarter wavelength type that comprises a first, a second and a third conductive layer, joined by means of dielectric layers. The first conductive layer comprises a first and a second conductive strip, separated, mutually parallel, each in one end connected to a first output and in another end connected to a second output. The second conductive layer comprises a third conductive strip, parallel to the first and the second conductive strip, in one end connected to a third output and in another end connected to a fourth output. The first conductive layer comprises a fourth conductive strip, parallel to and located between the first and the second conductive strip, in one end connected to the third output, and in another end connected to the fourth output.

There is provided, according to the present invention, a quadrature coupler according to claim <NUM>. Further embodiments are provided in the dependent claims.

With such an arrangement, the shield provides improved electrical isolation for the coupling region.

In one embodiment, portions of the coupler are formed by printing or additive manufacturing.

With such an arrangement, printing or additive manufacturing enables the coupler strip conductor widths and hence the degree of coupling between the pair of strip conductors to be adjusted, or tuned, while the coupler is still on a board having multiple functionality.

In one embodiment, a directional coupler includes a second pair of ground pads, the coupling region being disposed between the second pair of ground pads, and the first-mentioned pair of ground pads. The first-mentioned pair of ground pads and the second pair of ground pads are disposed along perpendicular lines. The electrically conductive shield layer is disposed over a second pair of opposing sides of the dielectric layer and onto the second pair of ground pads.

There is also provided a method for tuning a quadrature coupler according to claim <NUM>.

The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below.

Referring now to <FIG>, a dielectric substrate <NUM> is shown having: a first metal layer <NUM> disposed on an upper surface of the substrate <NUM>; and a ground plane conductor <NUM>, here for example gold, is disposed on a bottom surface of the substrate <NUM>. The first metal layer <NUM> is patterned to provide: a two pairs of ground pads; pair 16a<NUM>, 16a<NUM>, and pair 16b<NUM>, 16b<NUM>, respectively, as shown; a first lower strip conductor <NUM>, spaced from the pair of ground pads, having: an input at first end <NUM>I, an output at a second end <NUM>O; and, a coupling region <NUM> disposed between the first end <NUM>I, the second end <NUM>O, and between the two pairs on ground pads 16a<NUM>, 16a<NUM>, and pair 16b<NUM>, 16b<NUM>, respectively, as shown; a second lower strip conductor <NUM> having: an input end <NUM>I and an output end <NUM>O; and, a third lower strip conductor <NUM> having an input end <NUM>I and an output end <NUM>O, as shown. The first metal layer <NUM> may be printed, formed using additive manufacturing, or formed using conventional photolithographic-etching processing, as used in forming printed circuit boards, for example.

Referring now to <FIG>, a first dielectric layer <NUM>, here for example epoxy based dielectric ink <NUM>-<NUM> from Creative Materials, Ayer, MA is disposed over the coupling region <NUM> using printing or additive manufacturing, for example.

Referring now to <FIG>, a second metal layer, strip conductor <NUM> here printed or formed by additive manufacturing, for example, using a conductive ink, for example, Paru nanosilver PG-<NUM> or Dupont CB028, as a strip conductor disposed on the first dielectric layer <NUM>. It is noted that portions 28a and 28b of the second metal layer are formed over portions of the outer sidewalls of the first dielectric layer <NUM> onto portions of the output end <NUM>o of the third lower strip conductor <NUM> and onto portions of the input end <NUM>I of the second lower strip conductor <NUM>. Thus, second metal layer <NUM> has one end 28a disposed on, and electrically connected to, the input end <NUM>I of the second lower strip conductor <NUM> and has a second end 28b disposed on, and electrically connected to the output end <NUM>O of the third lower strip conductor <NUM>. The width of the second metal layer <NUM> over the coupling region <NUM> may be adjusted by the additive manufacturing or printing process to tune the quadrature coupler <NUM>.

Referring now to <FIG>, a second dielectric layer <NUM> is disposed over the second metal layer <NUM> and between the two pairs of ground pads 16a<NUM>, 16a, and pair 16b<NUM>, 16b<NUM>, as shown. The second dielectric layer <NUM> may be printed or formed by additive manufacturing, for example, using any suitable dielectric, for example epoxy based dielectric ink <NUM>-<NUM> from Creative Materials, Ayer, MA.

Referring now to <FIG>, an electrically conductive shield layer <NUM> is disposed on an upper surface of the second dielectric layer <NUM> extending over sides of the second dielectric layer <NUM> and onto the pair of ground pads 16a<NUM>, 16a<NUM>, and pair 16b<NUM>, 16b<NUM>, as shown. Conductive layers 34a, 34b are disposed on the sides of the substrate <NUM> to electrically connect the ground pads 16a<NUM>, 16a<NUM> to the ground plane conductor <NUM>, as shown, thereby completing the quadrature coupler <NUM>. It is noted that the conductive shield layer <NUM> and conductive layers 34a, 34b are here printed or formed by additive manufacturing, for example, using a conductive ink, for example Para nanosilver PG-<NUM> or DuPont CB028.

Because of the additive manufacturing printing process, the quadrature coupler <NUM> can be easily tuned. More particularly, referring to <FIG> and <FIG>, first, prior to the manufacturing process a determination is made as to the width required for the strip conductor <NUM> prior to forming the dielectric material <NUM> (<FIG>) so that the competed quadrature coupler <NUM> will have a proper width to produce quadrature coupler <NUM> with a desired, predetermined degree of coupling between the upper strip conductor <NUM> and the lower strip conductor <NUM> after forming the dielectric material <NUM> and shield <NUM>. Thus, referring to <FIG>, a computer simulation, using, for example <NUM>-dimensional electromagnetic simulator such as Ansys-HFFS (Ansys corporation, Canonsburg, PA <NUM>) is used to model a completed quadrature coupler <NUM> comprising: entering parameters of the simulated completed quadrature coupler, such parameters including: a width for upper strip conductor <NUM> estimated to provide a predetermined, desired degree of coupling between the lower strip conductor <NUM> and the upper strip conductor <NUM>; the dielectric materiel <NUM>, its thickness and its dielectric constant; the dielectric materiel <NUM>, its thickness and its dielectric constant; and shield layer <NUM> into a computer simulator to have the computer generate the actual degree of coupling produced by the simulated quadrature coupler. From the generated actual degree of coupling, a comparison is made between the generated actual degree of coupling and a predetermined desired degree of coupling. If the generated actual degree of coupling and the predetermined desired degree of coupling are different, the width of the upper strip conductor <NUM> in the simulation is changed and the process continues until they are equal. Next, the dielectric material <NUM>, its thickness and its dielectric constant; and shield layer <NUM> are removed from the simulation to thereby provide a computer model of the coupler at an intermediate stage in its fabrication, shown in <FIG>. Next, the degree of coupling of such coupler at the intermediate stage in its fabrication is recorded.

This recorded degree of coupling is used during the actual fabrication of the quadrature coupler <NUM>. More particularly, referring to <FIG>, the fabrication process includes: (a) providing the quadrature coupler after completion of the structure shown in <FIG> with the width of the upper strip conductor <NUM> having a minimum predicted width; (b) measuring the degree coupling between the pair of strip conductors using any conventional process such as for example an S-parameter analyzer; (c) comparing the measured degree of coupling with the recorded degree of coupling; (d) incrementally increasing the width of the upper strip conductor <NUM> (<FIG>); (e) repeating (b) through (d) until the degree of coupling reaches the recorded degree coupling; and (f) complete the quadrature coupler <NUM> as described above and in connection with <FIG>. It should be understood that instead of setting a minimum coupler specification and line width <NUM> and increasing line width <NUM> to achieve the desired coupler, a nominal or larger line width for <NUM> for the coupler can be used and techniques such as laser trim or milling tools can be used to reduce the line width to the desired level.

It should now be appreciated a quadrature coupler according to an example that does not have all the claimed features includes: a pair of overlying strip conductors separated by a first dielectric layer to provide a coupling region between the pair of overlying strip conductors; a pair of opposing ground pads, the coupling region being disposed between the pair of opposing ground pads; a second dielectric layer disposed over the coupling region and between the pair of opposing ground pads; and an electrically conductive shield layer disposed over the second dielectric layer, extending over opposing sides of the dielectric layer and onto the pair of opposing ground pads. The quadrature coupler may also include the feature including a second pair of ground pads, the coupling region being disposed between the second pair of ground pads, the first-mentioned pair of ground pads, the first-mentioned pair of ground pads and the second pair of ground pads being disposed along perpendicular lines, the electrically conductive shield layer being disposed over a second pair of opposing sides of the dielectric layer and onto the second pair of ground pads.

Claim 1:
A quadrature coupler, comprising:
a dielectric substrate (<NUM>);
a first metal layer disposed on an upper surface of the substrate, the first metal layer being patterned to provide:
a first pair of ground pads (16b<NUM>, 16b<NUM>);
a first lower strip conductor (<NUM>), spaced from the first pair of ground pads, having an input (<NUM>I) at a first end, an output (<NUM>O) at a second end, and a coupling region (<NUM>) disposed between the first end and the second end, and between the first pair of ground pads;
a second lower strip conductor (<NUM>) having an input end (<NUM>I) and an output end (<NUM>O); and
a third lower strip conductor (<NUM>) having an input end (<NUM>I) and an output end (<NUM>O);
a first dielectric layer (<NUM>) disposed over the coupling region;
a second metal layer (<NUM>) configured as a strip conductor disposed on the first dielectric layer over the coupling region, the second metal layer having one end (28b) disposed on, and electrically connected to, the output end (<NUM>O) of the third lower strip conductor (<NUM>) and having another end (28a) disposed on, and electrically connected to, the input end (<NUM>I) of the second lower strip conductor (<NUM>);
a second dielectric layer (<NUM>) disposed over the second metal layer and between the first pair of ground pads; and
an electrically conductive shield layer (<NUM>) disposed on an upper surface of the second dielectric layer;
characterized in that:
the electrically conductive shield layer (<NUM>) extends over a first pair of opposing sides of the second dielectric layer and onto the first pair of ground pads.