Phase shifters play an important role in many radio frequency (RF) circuit applications (e.g., in phased antenna arrays). Ferrite phase shifters are the preferred type of phase shifters used in non-active RF applications because of their low insertion loss, high power handling, fast switching, high resolution and high accuracy. While ferrite phase shifters are the preferred type of phase shifter, they are not easily integrated into stripline based RF circuit boards, which provide the dominant medium for RF circuits. Instead, in conventional implementations, ferrite phase shifters are often times interfaced with microstrip line boards.
Systems and methods for sit on top circuit board ferrite phase shifters are provided. In at least one embodiment, the system comprises a waveguide ferrite phase shifter configured to propagate electromagnetic energy longitudinally between a first and second end of the waveguide ferrite phase shifter, a stripline circuit board, wherein the stripline circuit board has at least one conductive trace, and one or more conductive pins configured to couple electromagnetic energy between the at least one conductive trace and one of the first or second ends of the waveguide ferrite phase shifter. The waveguide ferrite phase shifter comprises at least one ferromagnetic core that extends longitudinally between the first and the second ends of the waveguide ferrite phase shifter, one or more dielectric slabs that abut one side of the ferromagnetic core and extends longitudinally through the waveguide ferrite phase shifter against the at least one ferromagnetic core, and a metalized rectangular housing that encases the at least one ferromagnetic core and the at least one dielectric slab and extends longitudinally between the first and second ends of the waveguide ferrite phase shifter.
Understanding that the drawings depict only exemplary embodiments and are not therefore to be considered limiting in scope, the exemplary embodiments will be described with additional specificity and detail through the use of the accompanying drawings, in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the exemplary embodiments.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments. However, it is to be understood that other embodiments may be utilized and that logical, mechanical, and electrical changes may be made. Furthermore, the method presented in the drawing figures and the specification is not to be construed as limiting the order in which the individual steps may be performed. The following detailed description is, therefore, not to be taken in a limiting sense.
The embodiments described within this disclosure address the problem of integrating ferrite phase shifters with striplines, which makes the integration much simpler, cleaner, higher performing (i.e., less transition obstacles) and more cost effective. The embodiments described herein do so by configuring a pin to couple electromagnetic energy between a conductive trace in a stripline circuit board and a waveguide ferrite phase shifter.
A stripline circuit board 102 is an electromagnetic transmission line medium that has a conductive trace 110 to transport electromagnetic energy. The conductive trace 110 is a strip of conductive material disposed between two parallel ground plates 112. Moreover, a dielectric 114 separates the conductive trace 110 from the two parallel ground plates 112. The width of the conductive trace 110 along with the thickness and permittivity of the dielectric 114 determine the characteristic impedance of the stripline circuit board 102. The characteristic impedance of the stripline circuit board 102 may be matched by other parts of the sit on top circuit board ferrite phase shifter 100A as discussed in more detail below. The waveguide ferrite phase shifter 104 is cleanly integrated into the stripline circuit board 102 without the need for a microstrip transition, as in conventional embodiments.
In at least one embodiment, an electromagnetic signal travels from the one or more conductive traces 110 (shown in
As discussed above, the waveguide ferrite phase shifter 104 shifts the phase of an electromagnetic wave that passes through the waveguide ferrite phase shifter 104 using one or more ferromagnetic cores 120 that extend longitudinally between the first 106 and second 108 ends of the waveguide ferrite phase shifter 104. In some embodiments, the one or more ferromagnetic cores 120 have toroidal cross sections. In other embodiments, different cross sections of the ferromagnetic cores 120 can be used.
The waveguide ferrite phase shifter 104 also includes one or more dielectric slabs 118 that abut one side of the one or more ferromagnetic cores 120 for which the electromagnetic energy, in the form of a wave, propagates through. The one or more dielectric slabs 118 extend along the longitudinal axis of the ferromagnetic core 120. In exemplary embodiments, there is one dielectric slab 118 that is sandwiched between the two ferromagnetic cores 120. The dielectric slab 118 in this embodiment serves the same purpose as a dielectric center core, except that the dielectric constant of the dielectric slab 118 can be significantly higher than the dielectric constant of the center core of the ferromagnetic cores 120. As a result, more wavelengths of RF interaction are possible for a given physical length which makes this twin toroidal design more mass efficient than a single toroid design. Further, unlike other designs, the twin toroidal design provides a thermal path to remove heat from the toroid generated by RF power dissipation. In some embodiments, the ferromagnetic cores 120 and the dielectric slabs 118 can be secured using an epoxy and metalized. Using this twin toroidal configuration, the most RF-active ferrite in the ferromagnetic core 120 is located on each side of the dielectric slab 118. The outer portions of the ferromagnetic cores 120 are relatively inactive and serve merely to complete a magnetic path and allowing latching operations as explained below.
Further, as explained above, the waveguide ferrite phase shifter 104 includes a metalized rectangular housing 122 that encapsulates the one or more ferromagnetic cores 120 and the one or more dielectric slabs 118. In exemplary embodiments, the metalized rectangular housing 122 is a substrate that includes a metal coating such as copper and/or gold. In other embodiments, the metalized rectangular housing 122 can be a full metal casing. The metalized rectangular housing 122 encapsulates the one or more ferromagnetic cores 120 and the one or more dielectric slabs 118 along their longitudinal axis to create a waveguide structure. The width of the metalized rectangular housing 122 can be chosen depending on the wavelength of the RF energy that passes through the waveguide ferrite phase shifter 104, wherein RF energy with wavelengths more than twice the width of the metalized rectangular housing 122 will not propagate in the waveguide ferrite phase shifter 104.
In some embodiments, one or more conductive latch wires 124 extend through the middle of the one or more ferromagnetic cores 120 from the first end 106 to the second end 108 of the waveguide ferrite phase shifter 104. The latch wire 124 can magnetize the ferromagnetic core 120 to a desired degree of magnetization by passing a current through the latch wire 124, which will in turn create a magnetic field surrounding the latch wire 124 and magnetize the ferromagnetic core 120. The magnetized ferromagnetic core 120 will shift any electromagnetic signal passing through the waveguide ferrite phase shifter 104. The level of shift experienced by the electromagnetic signal will depend on the level of magnetization of the ferromagnetic core 120. In some embodiments, the latch wire 124 can come out at the end of the ferromagnetic core 120 and be soldered down to a via pad on the stripline circuit board 102 as shown in
As stated above, a pin 126 couples electromagnetic energy between the conductive trace 110 (shown in
To integrate the pin 126 into the stripline circuit board 102, a via 128 is created in the stripline circuit board 102. The pin 126 is then inserted inside the via 128 and electrically connected to the stripline circuit board 102, such as soldering the pin 126 to the stripline circuit board 102, so that an electromagnetic signal can travel between the stripline circuit board 102 and the pin 126. The pin 126 and the via 128 can function similar to a coaxial wire. In exemplary embodiments, the distance from the sides of the via 128 to the pin 126 can be chosen so the characteristic impedance of the pin 126 and the via 128 matches the characteristic impedance of the stripline circuit board 102, according to the characteristic impedance formula,
where D1 is the distance of the pin 126 from the sides of the via 128, d1 is the diameter of the pin 126 inside the via 128 and ∈r is the relative dielectric constant.
In addition to choosing the correct dimensions of the via 128 and the pin 126, in some embodiments, the apparatus 200 can be designed as follows to help tune and match impedances in the apparatus 200. The cross section of the ferrite phase shifter 104 can be chosen to match the impedance of the stripline circuit board 102. That is, the height and width of the ferromagnetic cores 120 and dielectric 118 can be chosen based on the desired frequency bandwidth and power handling demands that were chosen for the stripline circuit board 102. Once the ferrite phase shifter 104 and the stripline circuit board 102 are chosen to have matching impedances, the following can be varied in order to tune the apparatus 200, wherein exact values for each of the following characteristics can be obtained by routine experimentation. First, the distance between the pin 126 and the end of the ferrite phase shifter 104 can be varied to help match impedances. Second, a series capacitor can be inserted between the pin 126 and the waveguide ferrite phase shifter 104, wherein the length of the series capacitor can be varied. In at least one embodiments, the series capacitance is created by coupling a metal strip 130 to the end of the pin 126. The separation of the metal strip 130 from the metalized rectangular housing 122 can be the length of the capacitor. Third, the width of the conductive trace 110 immediately before the pin 126 can be varied, as shown in
Additionally, method 400 comprises providing a waveguide ferrite phase shifter, wherein the waveguide ferrite phase shifter is positioned to sit on top of the stripline circuit board and is secured to the stripline circuit board (block 404). In some embodiments, the positioning of the waveguide ferrite phase shifter can be the same or similar to how the waveguide ferrite phase shifter 104 is positioned on the stripline circuit board 102 in
Method 400 further comprises coupling electromagnetic energy between the at least one conductive trace and an end of the waveguide ferrite phase shifter using at least one conductive pin, wherein the at least one conductive pin is inserted into the stripline circuit board through a via (block 406). The one or more conductive pins and the via can have some or all of the same characteristics as the one or more conductive pins 126 and the via 128 discussed above under
Example 1 includes a system comprising: a waveguide ferrite phase shifter configured to propagate electromagnetic energy longitudinally between a first and second end of the waveguide ferrite phase shifter comprising: at least one ferromagnetic core that extends longitudinally between the first and the second ends of the waveguide ferrite phase shifter, at least one dielectric slab that abuts one side of the ferromagnetic core and extends longitudinally through the waveguide ferrite phase shifter against the at least one ferromagnetic core, and a metalized rectangular housing that encases the at least one ferromagnetic core and the at least one dielectric slab and extends longitudinally between the first and second ends of the waveguide ferrite phase shifter; a stripline circuit board, wherein the stripline circuit board has at least one conductive trace; and at least one conductive pin configured to couple electromagnetic energy between the at least one conductive trace and one of the first or second ends of the waveguide ferrite phase shifter.
Example 2 includes the system of Example 1, wherein at least one conductive latch wire extends through the at least one ferromagnetic core from the first end to the second end of the waveguide ferrite phase shifter.
Example 3 includes the system of any of Examples 1-2, wherein a first conductive pin of the at least one conductive pins couples electromagnetic energy between a first conductive trace of the at least one conductive trace and the first end of the waveguide phase shifter and a second conductive pin of the at least one conductive pins couples electromagnetic energy between a second conductive trace of the at least one conductive trace and the second end of the waveguide phase shifter.
Example 4 includes the system of any of Examples 1-3, wherein the at least one ferromagnetic core comprises two ferromagnetic cores each with toroidal cross sections and the at least one dielectric slab comprises one dielectric slab that is disposed between the two ferromagnetic cores.
Example 5 includes the system of any of Examples 1-4, wherein an electromagnetic shield surrounds the waveguide ferrite phase shifter and the at least one conductive pin that is coupling electromagnetic energy between the at least one conductive trace and the one end of the first or second ends of the waveguide ferrite phase shifter.
Example 6 includes the system of any of Examples 1-5, wherein the at least one conductive pin and the one of the first or second ends of the waveguide phase shifter are separated by a dielectric.
Example 7 includes the system of any of Examples 1-6, wherein a series capacitor is inserted between the at least one conductive pin and the waveguide ferrite phase shifter.
Example 8 includes the system of any of Examples 1-7, wherein the width of the at least conductive trace is varied in order to aid in matching the impedance of the stripline circuit board with the at least one conductive pin.
Example 9 includes the system of any of Examples 1-8, wherein the characteristic impedance of the waveguide ferrite phase shifter is substantially equal to the characteristic impedance of the stripline circuit board.
Example 10 includes a method for constructing a sit on top stripline circuit board ferrite phase shifter, the method comprising: providing a stripline circuit board, wherein the stripline circuit board has at least one conductive trace; providing a waveguide ferrite phase shifter, wherein the waveguide ferrite phase shifter is positioned to sit on top of the stripline circuit board and is secured to the stripline circuit board; and coupling electromagnetic energy between the at least one conductive trace and an end of the waveguide ferrite phase shifter using at least one conductive pin, wherein the at least one conductive pin is inserted into the stripline circuit board through a via.
Example 11 includes the method of Example 10 further comprising separating the at least one conductive pin from the waveguide ferrite phase shifter by a dielectric in order to aid in matching the impedance of the at least one conductive pin with the impedance of the at least one waveguide ferrite shifter.
Example 12 includes the method of any of Examples 10-11 further comprising inserting a series capacitor between the at least one conductive pin and the waveguide ferrite phase shifter in order to aid in matching the impedance of the at least one conductive pin with the impedance of the at least one waveguide ferrite shifter.
Example 13 includes the method of any of Examples 10-12 further comprising varying the width of the at least conductive trace in order to aid in matching the impedance of the stripline circuit board with the at least one conductive pin.
Example 14 includes the method of any of Examples 10-14 wherein the at least one conductive pin and the waveguide phase shifter are surrounded by an electromagnetic shield.
Example 15 includes the method of any of Examples 10-15 wherein the characteristic impedance of the waveguide ferrite phase shifter is substantially equal to the characteristic impedance of the stripline circuit board.
Example 16 includes the method of Example 10, wherein the waveguide ferrite phase shifter comprises at least one ferromagnetic core with a toroidal cross section that extends longitudinally between the first and the second ends of the waveguide ferrite phase shifter and at least one dielectric slab that abuts one side of the ferromagnetic core and extends along the longitudinal axis of the ferromagnetic core.
Example 17 includes the method of Example 16 further comprising at least one conductive latch wire extending through the at least one ferromagnetic core.
Example 18 includes the method of any of Examples 16-18 wherein the waveguide ferrite phase shifter comprises two ferromagnetic cores each with a toroidal cross section and one dielectric slab disposed between the two ferromagnetic cores.
Example 19 includes an apparatus comprising: at least one conductive pin configured to couple electromagnetic energy between at least one conductive trace in a stripline circuit board and a waveguide ferrite phase shifter wherein the at least one conductive pin is separated from the waveguide ferrite phase shifter by a dielectric.
Example 20 includes the apparatus of any of Examples 19-20 wherein the at least one conductive pin is surrounded by an electromagnetic shield.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.