CN1390368A - Variable phase shifter - Google Patents

Abstract

A variable phase shifter comprises first and second coupled signal conductors (6,7,17) providing a transmission path through the phase shifter. The signal conductors are relatively movable to vary the actual length of the transmission path. The first signal conductor comprises a pair of electrically level travelling arms (6,7) and the second signal conductor (17) is disposed between the arms of the first signal conductor. The ground plane (1) is arranged on one side of the signal conductor.

Description

variable phase shifter

field of invention

The invention relates to a variable phase shifter and a manufacturing method of the variable phase shifter.

Background of the invention

A phase shifter is an essential element of a phased antenna array. There is a need for a low cost, high reliability and low complexity phase shifter to fit into a phased antenna array.

Various methods for phase shifting signals have been used so far. Semiconductor devices such as PIN diodes have been used. There are electronically controlled switches used to vary the RF circuit to achieve the desired phase shift but not to allow continuous phase shift, these switches cause intermodulation, they are power limited and require complex control circuits. Phase shifters that change the dielectric constant of the material disposed between the conductor and the ground plane have also been used.

Another conventional approach employs first and second coupled signal conductors that provide a transmission path through the phase shifter, the signal conductors being relatively movable to vary the actual length of the transmission path. An example of such a phase shifter is described in US-A-5801600. This approach makes it difficult to ensure good signal coupling between conductors that minimizes intermodulation at the boundaries between conductors.

Summary of the invention

According to a first aspect of the present invention, there is provided a variable phase shifter comprising first and second coupled signal conductors providing a transmission path through the phase shifter, the signal conductors being relatively movable to vary the transmission path The actual length wherein the first signal conductor includes a pair of horizontal parallel arms and the second signal conductor is placed between the arms of the first signal conductor.

This configuration has several advantages. First, by placing the second signal conductor between the arms of the first signal conductor, the electrical coupling between the first and second conductors is maximized. This enables the length of the transport path to vary widely. Second, the conductor configuration forms highly symmetrical bifurcated transmission paths. Third, the spacing between the arms of the first signal conductor can be precisely controlled and adjusted if necessary.

Preferably, support means are provided on opposite sides of the first signal conductor in order to maintain a maximum spacing between the arms of the first signal conductor. This enables the first and second signal conductors to be kept in close proximity to maximize electrical coupling between the conductors and to precisely control line impedance. The first signal conductor is receivable within a hole in a support rib, wherein opposite sides of the hole provide support means. Alternatively, a pair of ribs may be provided, one of which has a recess for receiving the conductor, wherein the support means is provided by the base of the recess and the edge of the other rib.

According to a second aspect of the present invention, there is provided a variable phase shifter, comprising: first and second coupling signal conductors providing a transmission path through the phase shifter, the signal conductors can be relatively moved to change the transmission path a physical length; and a conductive ground plane disposed on at least one side of the signal conductor.

The setting of the ground plane enables the signal to propagate in TEM or quasi-TEM mode. The ground plane may be connected to a floating voltage reference, but is preferably electrically grounded. Preferably, the ground plane is connected to a voltage reference (or ground) at more than one point. This ensures that in use, the voltage across the entire ground plane is approximately constant.

Only one ground plane can be provided (called a microstrip configuration). Alternatively, a second ground plane may be provided on the opposite side of the signal conductors (stripline configuration). In another "hybrid" configuration, narrower ground strips may be provided on opposite sides of the signal conductors.

Those skilled in the art will appreciate that the ground plane may or may not be completely planar. Preferably, however, the or each ground plane has one or more substantially planar surface portions facing the first and second signal conductors.

Preferably, the width of the ground plane is significantly larger (for example, more than three times) than the width of each signal conductor (transverse to the signal propagation direction).

In a preferred configuration, one or both ground planes have a first portion proximate to the first conductor, a second portion proximate to the second conductor, and a step between the first and second portions. This enables control of the line impedance presented by the first and second conductors (ie, by varying the distance between the ground plane and the signal conductor).

Typically, the signal conductors have a generally planar surface facing the or each ground plane. This allows for easier manufacture of the signal conductors (for example by stamping the sheet metal process) and increases the field uniformity between the signal conductors and the ground plane.

Typically, the first and second signal conductors have opposing generally planar coupling surfaces. This also allows for ease of manufacture of the signal conductors (eg, through the process of stamping sheet metal) and maximizes the coupling between conductors.

Preferably, the arms of the first signal conductor respectively have substantially planar coupling surfaces arranged on opposite sides of the second signal conductor and arranged substantially parallel to each other.

The signal conductors may be C-shaped or L-shaped (as seen in a cross-sectional view taken along the direction of signal propagation), or may have interlocking grooves or steps. However, in a preferred embodiment, the signal conductors are strips of sheet material having a substantially rectangular cross-section.

The conductive material from which the signal conductors are made is usually a metal such as copper, brass, or aluminum alloy.

In a preferred configuration, the phase shifter further includes a third signal conductor, wherein the second signal conductor has a first arm coupled to the first signal conductor and a second arm coupled to the third signal conductor, whereby The second signal conductor provides a transmission path between the first and third signal conductors, and the second signal conductor and the first and third signal conductors are relatively movable to change the actual length of the transmission path.

The arms of the second signal conductor may be arranged obliquely relative to each other (ie, the second signal conductor may be V-shaped). Preferably, however, the first and second arms of the second signal conductor extend in substantially parallel directions.

The first and third conductors are movable, but preferably fixed, while the second signal conductor is movable (in the manner of a trombone slider).

A second aspect of the present invention also provides a method of manufacturing a variable phase shifter, the method comprising the following steps:

i) first and second coupled signal conductors are arranged to provide a transmission path through the phase shifter, the signal conductors can be moved relative to each other to change the actual length of the transmission path;

ii) making a conductive ground plane from a substantially planar plate of conductive material; and

iii) Place the ground plane on one side of the signal conductor.

In a preferred method of manufacturing the above phase shifter, the ground plane is formed from a substantially planar plate of conductive material. In contrast to coaxial configurations (traditionally made by an extrusion process), the ground plane can be formed from sheet material, for example by stamping or cutting. This makes the manufacturing process cheaper and simpler.

In its finished form, the ground plane may not be perfectly planar. For example, the sheet of material may be bent, bent, or otherwise formed with walls, grooves, ridges, and the like. In a preferred embodiment, the ground plane is formed with a pair of side walls and a stepped portion.

The following descriptions are given for the first and second aspects of the present invention.

The conductors may have sliding conductive contacts whereby the conductors are ohmically coupled, but preferably the second signal conductor is separated from the first signal conductor by an insulator whereby the first and second signal conductors are capacitively coupled. This can be used to minimize intermodulation that may be caused by metal-metal contacts.

The insulator may comprise a layer of air, but preferably the insulator comprises solid or liquid insulating material.

The solid insulator may be provided as a separate layer or coating (eg, a lubricious coating such as PTFE (polytetrafluoroethylene) or polyester) on the first and/or second signal conductors. In the case of the first aspect of the invention, the insulating coating is generally provided on the opposite coupling surface of the second conductor coupled to the arm of the first conductor.

The problem with using PTFE is that it wears out over time, causing direct contact between the signal conductors. This causes intermodulation.

According to a third aspect of the present invention, there is provided a variable phase shifter comprising first and second coupled signal conductors providing a transmission path through the phase shifter, the signal conductors being relatively movable to change the actual transmission path length, wherein at least one of the signal conductors has a coupling surface facing the other signal conductor and provided with an oxide coating.

The oxide coating serves to prevent direct contact between relatively moving conductive surfaces—thus preventing intermodulation.

Typically, the coating has been formed by anodizing, preferably hard anodizing. Hard anodized coatings have high hardness values and good wear characteristics.

Preferably, the oxide-coated signal conductor is made of aluminum or its alloys. Aluminum itself is easily anodized.

Usually, anodizing is carried out at a temperature below 5°C.

Typically, anodizing involves immersing a conductor in an electrolyte and passing a current through the conductor with a current density greater than 2 A/dm2.

Typically, the thickness of the oxide layer is greater than 25 microns.

One of the conductors, preferably the oxide-coated conductor, may have a lubricious coating (eg, PTFE) formed on one of its surfaces.

A third aspect of the present invention also provides a method of manufacturing a variable phase shifter, the method comprising the following steps:

i) first and second coupled signal conductors are arranged to provide a transmission path through the phase shifter, the signal conductors being relatively movable to vary the actual length of the transmission path; and

ii) forming an oxide coating on a surface of at least one of the signal conductors.

In a preferred embodiment, the phase shifter has connection terminals soldered directly to the coaxial cable. However, coaxial cables are expensive and difficult to connect.

According to a fourth aspect of the present invention, a variable phase shifter is provided, comprising: a circuit board with at least two conductive paths formed thereon; a first signal terminal connected to one of the conductive paths; a second signal terminal to which the conductive path is connected; and means for providing a variable phase shift between the first and second connection terminals.

The fourth aspect of the invention minimizes the number of coaxial cables required to interface with the phase shifter. In addition, the terminals can be easily and securely connected to the conductive paths on the circuit board.

Preferably, at least two connection holes are formed in the circuit board, and each signal terminal passes through a corresponding hole.

Multiple phase shifters can be mounted on a circuit board and connected by conductive paths. In this case, only one coaxial cable connection may be required.

The following description applies to phase shifters in accordance with all aspects of the invention.

The variable phase shifter may be installed in a power splitter/combiner comprising three or more signal connection terminals, wherein the variable phase shifter is coupled between two of the signal terminals.

In order to minimize signal reflection, an impedance matcher can also be coupled between two of the signal terminals.

Phase shifters are preferably used in feed networks for phased antenna arrays, typically in communication networks such as cellular mobile telephone networks.

Typically, phase shifters are sized to provide variable phase shifting for signals in a wavelength band having a lower limit equal to or greater than 400 MHz and an upper limit equal to or less than 3 GHz. In a preferred case, the phase shifter is dimensioned to provide a variable phase shift for signals in a wavelength band having a lower limit equal to or greater than 800 MHz and an upper limit equal to or less than 2.5 GHz.

Brief introduction to the drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a variable phase shifter;

Fig. 2 is a plan view of a pair of variable phase shifters, wherein all concealed components are shown, and coaxial cables are omitted;

Fig. 3 is a sectional view taken along line AA in Fig. 2;

Fig. 4 is a sectional view taken along line BB in Fig. 2;

Figure 5 is a side view of the phase shifter seen from the left side of Figure 2;

Figure 6 is a plan view of a double phase shifter, showing all concealed components and omitting coaxial cables;

Figure 7 is a perspective view of the upper side of a paired variable phase shifter test assembly with the slider in its fully retracted position;

Fig. 8 is a side view seen from the left side of Fig. 7 with all vertical dimensions magnified by 100%.

Figure 8a is a sectional view cut transversely to the direction of signal propagation through one of the support ribs;

Figure 9 is a perspective view of the underside of the assembly;

10 is a partial enlarged perspective view showing the underside of the assembly of the cable connector;

Figure 10a is a cross-sectional view showing the connector shown in Figure 10 connected to a coaxial cable;

Figure 11 is a perspective view of the bottom side of the assembly with some parts removed and the slider in its fully extended position;

Figure 12 is an end view seen from the left side of Figure 7;

Figure 13 is a partially enlarged perspective view of the assembly;

Figure 14 is a partial end view of the assembly seen from the right side of Figure 7;

Figure 15 is a circuit diagram of a dual-polarization phased antenna array; and

FIG. 16 is a side view of the antenna array shown in FIG. 15 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Please refer to FIG. 1 , a variable phase shifter includes a metal plate shell 1 providing a ground plane and connected to an electrically grounded outer conductor of a coaxial cable 2-4. The housing 1 has a planar base (as shown in FIG. 1 ) and a planar cover (not shown). The variable delay output signal conductor 5 comprises a pair of strips 6 , 7 of conductive material such as copper or brass connected by an end wall 8 . The inner conductor 9 of the coaxial cable 2 is connected to the end wall 8 . The input signal conductor 10 comprises a pair of copper or brass strips 11 , 12 connected by an end wall 13 . The inner conductor 14 of the coaxial cable 3 is connected to the end wall 13 . The lower electrode strip 12 has an arm 23 providing a fixed delay output terminal and connected to the inner conductor 15 of the third coaxial cable 4 . Thus, an input signal on conductor 14 is split at end wall 13 and passed along strips 11, 12 in electrical rows (ie, electrically connected so as to be joined together with conductor 14 at a common point).

The U-shaped slide 16 provides a variable length signal conductor. The slider 16 has an output arm 17 sandwiched between the bars 6 , 7 and an input arm 18 sandwiched between the bars 11 , 12 . The copper or brass slider 16 is coated on the top and bottom with a low friction insulating material such as polyester or Teflon ^™ (PTFE). The slider 16 is capacitively coupled to the signal conductors 5, 10 and changes the actual length of the transmission path by sliding in and out (as shown at 22) (i.e. changing the conductor length between the cables 3, 4 and the cable 2). length).

The capacitive coupling between the slider 16 and the signal conductors 5, 10 is sufficient to provide a broadband bandpass connection over its entire adjustment range.

The input signal 19 on coaxial cable 3 is split and output into a fixed delay output signal 20 on coaxial cable 4 and a variable delay output signal 21 on coaxial cable 2 . By adjusting the sliding electrodes 16, the phase shift of the output signal 21 with respect to the input signal 19 and the fixed-delay output signal 20 can be continuously varied.

A paired variable phase shifter package incorporating two phase shifters of the type shown in FIG. 1 is shown in detail in FIGS. 2-5. The signal conductors are housed within a brass or copper housing that includes a generally planar base 30 , end walls 35 , a pair of side walls 36 , 37 and a cover 31 . The cover 31 has a substantially planar lower portion 32 , a substantially planar upper portion 33 and a stepped portion 34 . The cover 31 also has six tabs 120 , 121 , 123 - 126 welded into the walls 35 - 37 to provide a secure electrical connection between the base 30 and the cover 31 .

Referring to FIG. 2, the casings 30-37 house a pair of variable phase shifters 38,39. The variable phase shifters 38 and 39 are the same, so only the phase shifter 38 will be described in detail below.

The phase shifter 38 includes an input signal conductor 40 , an output signal conductor 41 and a slider 42 . The output signal conductor 41 shown in FIG. 3 includes a lower brass or copper strip 48 which is bent at one end so as to form an end wall 49 (shown in the partial enlargement of FIG. 3 ). An upper brass or copper strip 47 is welded to the end wall 49 so as to be parallel to the lower strip 48 . The input signal conductor shown in FIG. 4 includes a pair of parallel brass or copper strips 44, 45 and end walls 46 (FIG. 2). The U-shaped slide 42 has an input arm 43 sandwiched between bars 44 , 45 and an output arm 50 sandwiched between bars 47 , 48 . As shown in detail in the partially enlarged view of FIG. 4 , the upper and lower surfaces of the sliding electrode 42 are coated with PTFE layers 51 , 52 .

The input and output conductors 40,41 are supported by a pair of support assemblies 53,54 shown in FIG. The components 53 , 54 are identical in structure, one of which 54 is shown in FIG. 4 . The assembly 54 includes a pair of plastic insulating ribs 55 , 56 extending between the side walls 36 , 37 and bolted to the base 30 and cover 31 . The rib 55 has four recesses that receive the phase shifter conductors. The low friction properties of the PTFE layers 51, 52 ensure that the slider 42 moves easily and reduces wear and interlocking.

The ribs 55, 56 are as narrow as possible in order to minimize their influence on the wave impedance of the emission line. In another embodiment, the ribs 55, 56 may be contoured as shown by the dashed line 54' in Figure 2 to make them narrower. If the ribs cause a jump in wave impedance, the jumps can be removed by forming holes (not shown) in the cover 31 and/or base 30 at the points where the ribs rest on the signal conductors. reduced to a minimum.

The pair of slides is connected to a common insulated drive 60 supported by a pair of slide bearings 61 , 62 .

In use, six coaxial cables 110-115 (FIG. 5) are connected to the opposite input cable 111 to the phase shifter shown in FIG. The outer conductor 63 of the cable 111 is inserted into the hole 66 in the end wall 35 so that the end of the conductor 63 is flush with the inner surface of the wall 35 . The outer conductor is fixed to the end wall 35 by means of solder 64 . The inner conductor 65 passes through a hole (not shown) in the end wall 49 and is secured by solder 67 . The end wall 49 is separated from the housing by an insulating gasket 68 .

Referring to FIG. 2, the input signal conductors 40, 72 each have a widened portion with a larger width 101 that reduces the impedance of this portion relative to the slider, output signal conductors and fixed delay output terminals. The widened portion also has a length of one quarter wavelength. This provides impedance matching to minimize reflections of the input signal at the point at which the transmission path splits at the fixed delay output terminal.

As can be clearly seen in FIG. 3 , the distance 150 between the upper part 33 of the cover and the upper bar 47 is approximately the distance 151 between the lower part 32 of the cover and the slider 42 . As a result, the wave impedance of the slider 42 approximates the wave impedance of the signal conductors 40,41. Instead of forming the stepped portion 34 by deformation, the stepped portion 34 may be formed by adding a conductor plate to the underside of the cover 31 .

A double variable phase shifter is shown in FIG. 6 . This phase shifter is similar to the paired phase shifters shown in FIGS. 2-5 , with the main difference that conductor 41 is connected to conductor 69 of second phase shifter 39 . This produces a double phase shift between the input signal 70 and the output signal 71 . Conductor 72 has a narrow profile (similar to output conductor 41 ) and there is only a single fixed delay output terminal arm 23 .

A paired phase shifter test assembly is shown in Figures 7-14. The two phase shifters 200, 201 in this assembly are identical, so only the phase shifter 200 will be described below. The signal conductors are attached to the substantially planar aluminum plate 202 . This board 202 provides a first ground plane (similar to substrate 30 in the embodiment shown in FIGS. 2-6). However, the embodiments shown in Figures 7-14 do not have an opposing ground plane. Instead, the dissipated flux lines are collected by a bent brass ground bar having a generally planar lower portion 203 , a generally planar upper portion 204 and a sloped step portion 205 . We have found that the narrower width of the strip 204 (compared to the width of the cap 31 in the embodiment shown in Figures 2-6) does not significantly degrade the performance of the phase shifter. In fact, the strip 204 could be narrower and still function as an effective matching shield.

A printed circuit board (PCB) 208 is attached to opposite major sides of the board 202 by means of double-sided adhesive tape (not shown). The PCB 208 includes an insulating layer with a layer of copper 301 coated on one surface (as shown in the cross-sectional view of Figure 10a) and a plurality of copper lines 210, 211, etc. (see Figure 9) formed on the other surface thereof. Plate 300.

The upper bar 214 and the lower parallel bar 206 form the input pins of the phase shifter. Both pins are the same, so only the input pins will be described below. The upper bar 228 and the lower bar 229 form the output pins of the phase shifter. The upper bars 214, 228 and the ground bar 204 etc. are omitted in FIG. 11 to show the lower bars.

As shown in Figure 8, the lower brass or copper strip 206 is bent down at one end thereof and has a connection terminal 207 passing through a hole 351 in the PCB 208 (best seen in Figure 13). As shown in FIG. 13 , the upper brass or copper strip 214 is also bent down at one end thereof and has a connection terminal 215 passing through the hole 351 . The copper layer 301 on the PCB is etched away to form a window 209 around the hole 351 as shown in FIG. 13 to ensure that the conductors 206, 214 are not electrically grounded. The other surface of the PCB 208 (shown in FIG. 9 ) is printed with copper strips 210, 211 having widened end connection areas 212, 213 surrounding the terminals 215, 207. As shown in FIG. 8, the terminals 215, 207 pass through the PCB 208. In a subsequent processing step, the tabs 215, 207 are soldered to the copper connection area 212 in order to ensure a good connection.

The brass strip 204 ( FIGS. 8 , 13 ) is bent at one end thereof and has a terminal end 250 passing through a hole 252 in the PCB 208 as shown in FIG. 13 . In a subsequent processing step, the tab 250 is soldered against the copper layer 301 on the PCB to provide a solid ground connection.

When in use, a set of metal clips 216, 217 etc. is connected to the coaxial cable. The coaxial cable is not shown in Figure 9, but a single exemplary cable connection is shown in detail in Figure 10a. The clip 216 shown in Figures 7 and 10 has a pair of lugs 218, 219 securing the clip against the copper layer 301 on the surface of the PCB. In a subsequent processing step, the lugs 218, 219 are soldered in order to ensure a firm connection. The clip 216 also has four arms 220-223 that pass through holes 224 in the PCB 208 (shown in FIG. 10 ). The coaxial cable shown in FIG. 10 a has an outer conductor 225 joined to arms 220 - 223 and an inner conductor 226 joined to copper wire 210 . In a subsequent processing step, the arms 220 - 223 are bent inwardly and welded to securely grip the outer conductor, and the inner conductor 226 is welded to the copper strip 210 . The connection of Figure 10a is actually solid. The width of the critical gap 227 between the end of the wire 210 and the hole 224 can also be precisely controlled.

U-shaped slide 230 (best seen in FIG. 11 ) has a first arm 231 sandwiched between bars 206 , 214 and a second arm 232 sandwiched between bars 228 , 229 . The slide 230 is connected to a co-insulated drive 238 supported by three slide bearings 239-241. The driver 238 is formed as a single piece by injection molding with a central layer 242 , upper and lower reinforcement layers 243 , 244 and bosses 236 , 237 housed in holes (not labeled) in the slider 230 . In a subsequent processing step, the projections 236 , 237 are flattened relative to the slide in order to fix the slide on the drive 238 .

The signal conductors are supported by a pair of supports 233,234. The structures of the supports 233 and 234 are the same, so only one of them will be described below. The support 233 is formed as a single piece of insulating plastic having a rectangular hole to receive the signal conductor and press fit clips 234, 235 for securing the upper ground conductor bar 204 (shown in FIG. 7). The support 233 is secured to the rest of the assembly by lugs 251-253 passing through holes (noted) in the board 202 and PCB 208 and press-fitted against the opposite side of the PCB 208 as shown in FIG. 9 .

In use, a 50 ohm coaxial cable is connected to the clips 216,217. The copper strips 210, 211 and the phase shifter signal conductors are each sized to exhibit a wave impedance of approximately 50 ohms and thereby minimize signal reflections.

As shown in the embodiment shown in Figures 2-6, the wave impedance of the slider 230 is controlled by the step 205 provided in the grounding strip.

The slider 230 is manufactured through a process described below.

slider manufacturing process bath describe Chemicals 1 pre-cleaning Al Probright ^™ 2 pre-cleaning rinse overflow H ₂ O 3 Corrosive erosion sodium hydroxide solution 4 Corrosive rinse overflow H ₂ O 5 To residue (desmut) nitric acid solution 6 Rinse off residue overflow H ₂ O 7 Hard anodizing sulfuric acid solution 8 Hard Anodized Rinse overflow H ₂ O 9 hot water rinse Thermal overflow H ₂ O

Bath No. 1 Pre-cleaning

Chemicals: Al PROBRIGHT ^™

            Al Probright is a

Dirt on its alloys and alkali on most polishing pastes

A neutral solution.

Tank volume: 14.4 liters

Bath Composition: 10% AlProbright

90% deionized water

Temperature: Ambient temperature

Time: 3 minutes or more (depending on contamination)

Bath No. 2 Pre-cleaning and rinsing

Chemicals: Flood H ₂ O

Tank volume: 18 liters

Chemical test: 1.pH8-10

2. Maintain specifications (specs) by controlling overflow

Bath No. 3 Corrosive Erosion

Chemicals: Sodium Hydroxide

Sodium hydroxide is a strong alkaline etchant which will form

                                                will

Prevents insoluble aluminum hydroxide from precipitating in the etch bath

middle.

Tank volume: 14.4 liters

Bath composition: 40 g/l sodium hydroxide

14.4 liters of deionized water

Temperature: Ambient temperature

Time: 3 minutes

Bath No. 4 Corrosive Rinse

Chemicals: Flood H ₂ O

Tank volume: 18 liters

Chemical test: 1.pH10-11

2. Maintain specifications by controlling overflow

Bath No. 5 Remove residue

Chemicals: Nitric Acid

                  Nitric acid is designed to

Remove residue from gold and brighten its surface.

Tank volume: 14.4 liters

Bath composition: 30% nitric acid

70% deionized water

Temperature: Ambient temperature

Time: 3 minutes

No. 6 bath to remove residue and rinse

Chemicals: Flood H ₂ O

Tank volume: 18 liters

Chemical test: 1.pH2-3

2. Maintain specifications by controlling overflow

Bath No. 7 Hard Anodized

Chemicals: sulfuric acid

Tank volume: 14.4 liters

Bath composition: 10% sulfuric acid (98%)

Operating parameters: 175-225 g/L

Temperature: 0℃±1℃

Time: 60 minutes (thickness is almost a function of time)

Current density: 3 amps/dm2 ^-5 amps/ ^dm2

Aluminum alloy grade: 5005

Bath No. 8 Hard Anodized Rinse

Chemicals: Flood H ₂ O

Tank volume: 18 liters

Parameters: pH2-3

Immersion time: up to 2 minutes

Bath Control: Prolonged immersion with a pH greater than 3 can

Causes uneven discoloration. maintained by adding sulfuric acid

pH value.

Bath No. 9 Hot water rinse

Chemicals: overflow water

Tank volume: 14.4 liters

Temperature: 50-60℃

Chemical test: pH6-7

Maintain pH specification by adjusting overflow rate

Note that this process does not include a sealing step. This step is excluded to ensure a wear-resistant oxide coating.

The slides were made of aluminum alloy which was hard anodized (see bath No. 7 above) to form the oxide layer shown in Figure 8a. FIG. 8 a is a cross-sectional view cut from a portion of the support rib 233 . Figure 8a is not to scale. The support rib has a hole 310 sized to loosely receive the signal conductor. In one example, the hole 310 is 2.4mm high, while the signal conductors 206, 214, 231 are 0.7mm thick—giving a total of 0.3mm play. The holes 310 can be precisely positioned and dimensioned to precisely control the wave impedance of the conductor.

The slide arm 231 shown in Figure 8a has an aluminum alloy core 311 surrounded by a 50 micron thick oxide layer 312 formed during hard anodizing. The upper and lower sides of the slider are spray-coated with PTFE thin layers 313, 314.

In use, PTFE's low-friction properties reduce wear between moving parts. Should the PTFE layers 313, 314 wear away, the oxide layer 312 (being an electrical insulator) prevents any metal-to-metal contact between the electrodes, thereby preventing intermodulation. The oxide layer 312 is also relatively wear resistant, and we have found that PTFE tends to fill the cracks in the oxide, thereby improving wear characteristics.

The PTFE layers 313, 314 may be omitted if necessary. The signal conductors 206, 214 may also be made of hard anodized aluminum alloy with a PTFE coating.

The assembly shown in Figure 7-14 is a test assembly used to test the performance of a phase shifter. When installed in a phased antenna array system (described below), multiple phase shifters can be mounted on a single PCB and connected together by wires on the upper surface of the PCB. In this configuration, only a single coaxial connection to the PCB is required.

The phase shifters shown in FIGS. 2-14 can be used in the circuit configuration shown in FIG. 15 . A signal generator 80 generates a signal which is input to a double phase shifter 81 of the type shown in FIG. 6 . Auxiliary output terminal arm 23 of phase shifter 81 is connected to phase shifter 82 which in turn is connected to a pair of dual polarized radiators 83 , 84 . The variable delay output of the phase shifter 81 is input to a phase shifter 85 which in turn is connected to a pair of dual polarized radiators 86 , 87 . The opposite terminals of the emitters are driven by a set of complementary drive circuits (shown in the top half of Figure 15).

The phase shifters 82, 95 may be housed together in a pair of phase shifter packages. Similarly, phase shifters 85, 96 may be housed together in a pair of phase shifter packages. Alternatively, phase shifters 95, 96 and 82, 85 may be housed together.

Referring to Figure 16, the antennas 83, 84, 86, 87 may be arranged vertically and emit phase-shifted signals traveling as a common wavefront 97. The wavefront 97 dips down at an angle 98 that is proportional to the relative phase shift of the signals. Therefore, the downtilt angle can be adjusted by adjusting the variable phase shifts 81 , 82 , 85 , 95 , 96 , 99 . Typically, this is accomplished by connecting the drive members 60 of the four phase shifter packages to a common drive arm.

Typically, antennas are part of cellular communication systems and transmit in the wavelength range between 800-2500 MHz. However, it will be appreciated that the described phase shifters can be operated in a variety of wavelength regions with appropriate scaling.

It should be seen that the present invention provides a variable phase shifter that is easy to manufacture and has a wide phase shift range. Although phase shifters have been illustrated as being used in conjunction with an array of transmit antennas, it is to be understood that phase shifters may also be used in conjunction with an array of receive antennas. In this case it will act as a phase shifter/power combiner rather than a phase shifter/power splitter.

Although the present invention has been described by way of example, it will be appreciated that the invention can be modified and/or varied without departing from the scope of the invention as defined in the appended claims.

Claims (45)

1. A variable phase shifter comprising first and second coupled signal conductors providing a transmission path through said phase shifter, said signal conductors being relatively movable to vary the actual length of said transmission path, wherein said The first signal conductor includes a pair of horizontal parallel arms, and the second signal conductor is disposed between the arms of the first signal conductor. 2. The variable phase phase shifter of claim 1, further comprising support means disposed on opposite sides of the first signal conductor to maintain the distance between the arms of the first signal conductor. Maximum spacing. 3. A variable phase shifter comprising: first and second coupled signal conductors providing a transmission path through said phase shifter, said signal conductors being relatively movable to vary the actual length of said transmission path; and A conductive ground plane is disposed on at least one side of the signal conductor. 4. The variable phase shifter of claim 3, further comprising a second ground plane disposed on an opposite side of the signal conductor. 5. The variable phase shifter according to claim 3 or 4, wherein said one or two ground planes have a first portion close to said first conductor, a second portion close to said second conductor , and a step between the first and second parts. 6. A variable phase shifter as claimed in any one of claims 3-5, wherein the signal conductors each have a substantially planar surface facing the or each ground plane. 7. A variable phase shifter according to any one of claims 3-6, wherein the or each ground plane has one or more ground planes facing the first and second signal conductors. Roughly planar surface portion. 8. The variable phase shifter according to any one of claims 3-7, wherein said ground plane and said first and second signal conductors respectively have corresponding width, and the width of the ground plane is more than three times greater than the width of each of the signal conductors. 9. The variable phase shifter according to any one of claims 3-8, wherein the ground plane is made of a substantially planar conductive material plate. 10. A variable phase shifter comprising first and second coupled signal conductors providing a transmission path through said phase shifter, said signal conductors being relatively movable to vary the actual length of said transmission path, wherein said At least one of the signal conductors has a coupling surface facing the other signal conductor and provided with an oxide coating. 11. The variable phase shifter of claim 10, wherein the coating has been formed by anodizing. 12. The variable phase shifter of claim 11, wherein the coating has been formed by hard anodizing. 13. The variable phase shifter according to any one of claims 10-12, wherein the signal conductor with the oxide coating is made of aluminum or its alloys. 14. A variable phase shifter according to any one of claims 10-13, wherein at least one of the signal conductors has a lubricious coating formed on a surface thereof. 15. The variable phase shifter of claim 16, wherein the lubricious coating is formed on top of the oxide coating. 16. A variable phase shifter as claimed in any one of the preceding claims, wherein the first and second signal conductors have opposing generally planar coupling surfaces. 17. The variable phase shifter according to claim 16 , wherein the arms of the first signal conductor respectively have substantially flat surfaces arranged on opposite sides of the second signal conductor and substantially parallel to each other. shape coupling surface. 18. A variable phase shifter according to any one of the preceding claims, further comprising a third signal conductor, said second signal conductor having a A first arm and a second arm coupled to the third signal conductor, whereby the second signal conductor provides a transmission path between the first and third signal conductors, and the second signal conductor and The first and third signal conductors are relatively movable to change the actual length of the transmission path. 19. The variable phase shifter of claim 18, wherein the first and second arms of the second signal conductor extend in substantially parallel directions. 20. A variable phase shifter according to any one of the preceding claims, wherein said second signal conductor is separated from said first signal conductor by an insulator, whereby said The first and second signal conductors are capacitively coupled. 21. The variable phase shifter of claim 20, wherein the insulator comprises a solid or liquid insulating material. 22. The variable phase shifter of claim 21, wherein the insulator comprises an insulating coating on the first and/or second signal conductors. 23. A variable phase shifter as claimed in claim 21 or 22, wherein the insulating material is in contact with the two signal conductors, whereby when the signal conductors move relative to each other, the insulating material provides a sliding bearing surface . 24. A variable phase shifter, comprising: a circuit board with at least two conductive paths formed thereon; a first signal terminal connected to one of the conductive paths; a second signal terminal connected to the other conductive path ; and means for providing a variable phase shift between said first and second connection terminals. 25. The variable phase shifter as claimed in claim 24, further comprising at least two connection holes formed in the substantially planar surface, and the signal terminals respectively pass through a corresponding hole. 26. The variable phase shifter of claim 24 or 25, further comprising a coaxial cable having an inner conductor and an outer conductor, the inner conductor being connected to one of the conductive paths. 27. The variable phase shifter according to any one of the preceding claims, wherein the size of the phase shifter is made such that its lower limit is greater than or equal to 400MHz, and its upper limit is less than or equal to 3GHz Signals in the wavelength band provide variable phase shift. 28. The variable phase shifter as claimed in claim 27, wherein the size of the phase shifter is made to be a signal in a wavelength band whose lower limit is greater than or equal to 800MHz and whose upper limit is less than or equal to 2.5GHz Provides variable phase shift. 29. A power splitter/combiner comprising three or more signal terminals and a variable phase shifter as claimed in any one of the preceding claims coupled between two of the signal terminals. 30. The power splitter/combiner of claim 29, further comprising an impedance matcher coupled between two of the signal terminals. 31. A phased antenna array comprising: at least two radiating elements; and a supply network for supplying relatively phase-shifted signals to said radiating elements, wherein said supply network comprises one or more - A variable phase shifter as claimed in any one of claims 28 and/or a power splitter/combiner as claimed in claims 29 or 30. 32. A cellular communication system comprising the phased antenna array of claim 31. 33. A method of manufacturing a variable phase shifter, said method comprising the steps of: i) first and second coupled signal conductors are arranged to provide a transmission path through said phase shifter, said signal conductors being relatively movable to vary the actual length of said transmission path; ii) making a conductive ground plane from a substantially planar plate of conductive material; and iii) Providing the ground plane on one side of the signal conductor. 34. The method of claim 33, wherein said step of forming a ground plane includes the step of bending a pair of opposing edges of said plate to form a pair of side walls. 35. A method as claimed in claim 33 or 34, wherein said step of forming a ground plane comprises bending said plate so that there is a difference between the first portion of said first conductor and the second conductor The step of forming a stepped portion between the second portions. 36. The method according to any one of claims 33-35, wherein said step of providing first and second signal conductors comprises forming each conductor from a substantially planar sheet of conductive material. step. 37. A method of manufacturing a variable phase shifter, said method comprising the steps of: i) first and second coupled signal conductors are arranged to provide a transmission path through said phase shifter, said signal conductors being relatively movable to vary the actual length of said transmission path; and ii) forming an oxide coating on a surface of at least one of the signal conductors. 38. The method of claim 37, wherein step i) comprises forming an oxide by anodizing. 39. The method of claim 38, wherein step i) comprises forming an oxide by hard anodizing. 40. The method of claim 39, wherein the anodizing is performed at a temperature below 5°C. 41. A method according to any one of claims 38-40, wherein the anodizing comprises immersing the conductor in an electrolyte at a current density greater than ² amperes per decimeter current flows through the conductor. 42. The method of any one of claims 37-41, further comprising the step of forming a lubricious coating on a surface of at least one of the signal conductors. 43. The method of claim 42, wherein the lubricious coating is formed on top of the oxide coating. 44. A variable phase shifter manufactured by the method of any one of claims 33-43. 45. The variable phase shifter of claim 3, further comprising a conductive ground strip disposed on an opposite side of the signal conductor, the ground strip having a width transverse to the direction of signal propagation, The width is less than the width of the ground plane.

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