Non-uniformized matching ultra-wideband duplexer structure

Abstract

Non-uniformized matching ultra-wideband duplexer structure (1) for mm wavelength frequency range. The structure consists of a ring hybrid circuit (8) and a radar chip (2). The ring hybrid circuit (8) consists of a transmission-reception line (5), a reception line (6), a transmission line (7), isolation line (16) and phase-shifting sections (9) arranged in a ring between the individual lines (5, 6, 7, 16). On the ring (13) formed by the phase- shifting sections (9) arranged in the shape of a ring, at the branching of the reception line (6) and the isolation line (16), a non-uniformized symmetrical waveguide matching cutout (11) is formed. The cutout (11) is in the shape of an isosceles triangle. The base (12) of the cutout (11) is closer to the center of the ring (13).

Description

[0001] NON-UNIFORMIZED MATCHING ULTRA-WIDEBAND DUPLEXER STRUCTURE

[0002] The invention relates to a non-uniform ized matching ultra-wideband duplexer structure for mm wavelength frequency range. The structure consists of a ring hybrid circuit and a radar chip. The ring hybrid circuit is arranged on a microwave substrate made of conductive film and consists of a transmission-reception line namely an excitation line, a reception line, a transmission line, an isolation line and phase-shifting sections arranged in a ring between the individual lines. The reception line and the transmission line are connected to the radar chip.

[0003] The mm-wave level measurement has developed greatly in recent years due to the universal acceptance of the polluter pays principle. The discharge of waste water has a significant impact on the environment. For this reason, the measurement of waste water emissions has been introduced in many countries at major emitters under official supervision. The polluter pays the waste water treatment fee based on the amount of waste water it emits, i.e., the polluter pays principle applies. The amount of emission can be measured with a level measuring radar in an open-channel flow measurement arrangement. An important breakthrough occurred in technical life, because cheap and extremely accurate level measuring radar chips with a bandwidth of 77-81 GHz appeared.

[0004] With the help of these radar chips, the tank level measuring radar can be made in the case of a suitable antenna adapter unit and a millimeter-range ultra-wideband design duplexer. Until now, radars with a bandwidth of 77-81 GHZ have been implemented using expensive thin-film integrated circuits with one or more layers of ceramic or sapphire substrates providing high dimensional accuracy.

[0005] In the field of wideband microwave matching circuits, several solutions are known from the field of tank level measuring radars. Patent application US 8416033 B2 describes a compact wideband metamaterial-based ring hybrid. The patent uses two-band compensated metamaterial-based matching circuits in the phase-shifting lines. Due to the tolerance sensitivity of the matching circuit, the solution cannot be used in wavebands in the millimeter range.

[0006] The solution with the double ring hybrid duplexer according to patent application JP 3600940 B2 eludes the issue of matching on a separate line. The solution can be used in millimeter waveband applications, but only in low-precision radar applications using an external mixer.

[0007] US 9413053 B2 describes a non-uniformized directional coupler solution with wideband galvanic isolation with stepped matching. This solution is very sensitive to tolerances and requires an external wideband termination, making it difficult to realize in millimeter wavelength applications.

[0008] Patent application US 8207796 B2 includes a wideband millimeter range resonator matching circuit. A significant disadvantage of it is the tolerance sensitivity. Thus, it cannot be mass-produced on a cheap microwave substrate.

[0009] The disadvantage of the previously known solutions for ring hybrid duplexers is that most of them were developed for high-stability thin-film circuits. The described laminated microwave plastic layered versions are not suitable for use with 77-81 GHz bandwidth mm-wavelength signals, because their manufacturing accuracy is low. The compensability of the matching closing ultra-wideband symmetric ratio holding design did not come up in case of ring hybrids, as its solution is not trivial.

[0010] The document CN206271848U entitled "Differential pair line interface based on circulator" implements differential signal transmission in a 24 GHz microwave circuit, which converts the signal of the asymmetric drive power line into a symmetrical output in order to enable the signal to be routed over a greater distance on the printed circuit board. To this end, it uses a ratrace hybrid circuit with resistive port termination. The circuit does not contain matching power line elements with non-uniform waveguides and does not operate in the millimeter range (above 40 GHz). This adapter with resistive port cannot be implemented with a circuit solution in the mm range, since such a wideband terminator cannot be manufactured in this frequency band with a bandwidth of 3-4 GHz.

[0011] By developing the solution according to the present invention, our goal was to create a chip-sealed-term inated and ultra-wideband hybrid duplexer structure operating in the mm-wave range, which enables reproducible mass production and the creation of a ring hybrid duplexer with high reflection attenuation in the case of a cheap laminated microwave plastic substrate.

[0012] During the innovation process, it has been realized how the expensive thin-film integrated circuit can be replaced with a cheap, industrial BGA-encapsulated integrated circuit and a laminated microwave plastic substrate in the case of a special design (this solution was described in detail in Hungarian Patent P2200116). In order to be able to summarize the transmission and reception signal of the millimeter wave radar without intermodulation distortions, an ultra-broadband coplanar waveguide hybrid and a terminating resistor with a bandwidth of several GHz must be implemented. It is mentioned here that the coplanar definition means the coplanar waveguide electric plane transmission line that can be manufactured using printed circuit board technology and is used to transmit microwave frequency signals. On a smaller scale, coplanar waveguide transmission lines are often incorporated into monolithic microwave integrated circuits. A conventional coplanar waveguide (CPW) consists of a single conducting track printed onto a dielectric substrate and a pair of return conductors located on either side of the strip. All three conductors are located on the same side of the substrate. The return conductors are separated from the center track by a small gap, the width of which does not change along the length of the line. Moving away from the central conductor, the return conductors usually extend to an indefinite but large distance, so that each of them is notionally a semi-infinite plane.

[0013] It has been realized that by switching a redundant port of multi-port radar chips to receive mode, a not very good, but wideband closure can be created. With a suitable matching circuit, the problem of exact matching can be solved, but due to the small dimensions, this requires high dimensional accuracy. It has been realized that wideband matching can be achieved with a symmetric non-uniformized coplanar waveguide matching construction formed in the ring hybrid, if the phase shift of the ring hybrid is modified. Since the design of the adapter is proportional, it does not require subsequent adjustment or tuning. With this solution, the degree of wideband matching exceeds the 35 dB reflection attenuation in the mm wavelength range in the middle of the band.

[0014] It has also been realized that the attenuation between the transmission and reception signals of a cheap ring hybrid can be maximized by providing a perfect match on its power sink side. This can best be closed in the millimeter wave band with an unused input of a multi-channel radar integrated circuit. In order for the termination to result in a high reflection attenuation even in a wideband, an additional compensating circuit is needed, but this cannot be realized with the prior art stub process in the millimeter wave band on a plastic substrate. It has been realized that the branching of the ring hybrid can be taken as a power divider, and with the known MASON node relocation in waveguides, the compensation can be symmetrically placed beyond the node. Therefore, according to the rules of the MASON signal path diagram, the compensating circuit required in the matching branch was placed beyond the node in order to implement it symmetrically. Articles describing the theory of Mason's nod relocation: I. Mason, S.J. (1956) Feedback Theory — Further Properties of Signal Flow Graphs. IEEE, 44, 920-926. and II. Mason, Samuel J. (September 1953). Feedback Theory - Some Properties of Signal Flow Graphs. Proceedings of the IRE. 41 (9): 1144-1156.lt has been realized that the frequency dependence of the required compensation reactance can be specified in a simulator with a simple optimization objective function. After the optimization, a non-trivial but very simple triangular cutout, much smaller than the wavelength resulted in a very high reflection attenuation with a large bandwidth. The solution can be easily produced on a plastic microwave substrate in a reproducible manner. A similar ring hybrid reactance compensating solution has not been found in the prior art, since the compensation was carried out in the phaseshifting branch in previous solutions, which resulted in complicated compensating solutions. The increase in attenuation between the transmission and reception signal of the ring hybrid resulted in an increase in the radar range. Accordingly, the present invention is a non-uniform ized matching ultra-wideband duplexer structure for the mm wavelength frequency range. The structure consists of a ring hybrid circuit and a radar chip. The ring hybrid circuit is arranged on a microwave substrate made of conductive film and consists of a transmission-reception line, namely an excitation line, a reception line, a transmission line, an isolation line and phase-shifting sections arranged in a ring between the individual lines. The reception line and the transmission line are connected to the radar chip. At the branching of the ring, the receiving line and the isolation line, a non-uniform symmetrical waveguide matching cutout is formed on the film of the ring hybrid circuit. The isosceles triangular cutout is formed between at least two phase shift sections. The base of the cutout is perpendicular to the radius of the ring hybrid circuit and the base of the cutout is closer to the center of the ring.

[0015] Some advantageous embodiments are described in the dependent claims.

[0016] The duplexer structure according to the invention will be described with reference to the accompanying drawings in which:

[0017] Figure 1 A shows the top view of the chip-sealed-terminated non-uniformized matching ultra-wideband ring hybrid duplexer structure;

[0018] Figure 1 B. shows the top view of the back side of the chip-sealed non-uniformized matching ultra-wideband ring hybrid duplexer structure;

[0019] Figure 1 C is a cross-sectional representation of the portion at intersection line B - B of Figure 1A;

[0020] Figure 2 is an enlarged top view of the parts of the ring hybrid circuit;

[0021] Figure 3 is a cross-sectional representation of the portion at the intersection line A - A of Figure 2;

[0022] Figure 4 shows the frequency curves of the reflection attenuation without a cutout and in the case of cutouts with different base sizes; Figure 5 shows the frequency curves of the isolation attenuation without a cutout and in the case of cutouts with different base sizes;

[0023] Figure 6 shows the functions of the reflection factor of the reception line as a function of the angle of cutout;

[0024] Figure 7 shows the isolation attenuation of the reception line and the transmission line as a function of the angle of cutout;

[0025] Figure 8 shows the functions of the reflection factor of the reception line as a function of the depth of the cutout;

[0026] Figure 9 shows the isolation attenuation of the reception line and the transmission line as a function of the depth of the cutout.

[0027] The non-uniform ized matching ultra-wideband duplexer structure 1 according to the present invention has been developed for the frequency range of mm wavelength, preferably for the frequency range of 75-83 GHz. Structure 1 consists of the ring hybrid circuit 8 and the radar chip 2 (Figure 1 ). The 8-ring hybrid circuit is made of a conductive film 4 arranged on a microwave substrate 3. The ring hybrid circuit 8 consists of the transmission-reception line 5, the reception line 6, the transmission line 7, the isolation line 16 and the phase-shifting sections 9 arranged in a ring 13 between the individual lines 5, 6, 7, 16 (Figure 2). The reception line 6 and the transmission line 7 are connected to the radar chip 2 (Figure 1 ). On the ring 13 formed by the phaseshifting sections 9, at the branching of the reception line 6 and the isolation line 16, a non-uniformized symmetrical waveguide matching cutout 11 is formed from the conductive film 4 of the ring 13 (Figure 2). The cutout 11 is in the shape of an isosceles triangle and is formed between at least two phase shift sections 9. The base 12 of the cutout 11 is perpendicular to the radius of the ring 13 of the ring hybrid circuit 8, it is located in the center line of the lines 6, 16, and the base 12 of the cutout 11 is closer to the center of the ring 13.

[0028] The transmission-reception branch 5 is actually the so-called excitation line, the design and operation of which was previously described in the Hungarian invention No. P2200116.

[0029] Figure 1 shows the non-uniformized ultra-wideband ring hybrid duplexer structure 1 sealed with radar chip 2 according to the present invention, where the transmission- reception line 5 is connected to the ring 13 of the ring hybrid circuit 8. A cutout 11 , as described above, is formed where the coplanar waveguide coupled to the reception line 6 connects to the ring 13. The transmission-reception line 5 and the reception line 6 are designed in such a way that they transmit the radar signal with a phase shift of 90° relative to each other. The phase-shifting section 9 between the height 14 of the cutout 11 and the center line of the transmission-reception line 5 creates a phase shift of 90° in the middle of the band. Figure 1 shows the shielding islands 10 known in the art formed around the ring hybrid circuit 8. For example, they can be formed from solder points 18 of different sizes. Advantageously, the optimal size and arrangement of the solder points 18 is determined by finite element simulation.

[0030] The isolation line 16 is a coplanar waveguide that functions only as a matching, and the cutout 11 is formed where it connects with the ring 13. The isolation line 16 is connected to the radar chip 2. The isolation line 16 and the reception line 6 are designed in such a way that a 90° phase shift is created in the middle of the band, between the height 1 of the cutout 11 formed at the connection of the isolation line 16 with the ring 13 and the height 14 of the cutout 11 formed at the connection of the reception line 6 with the ring 13.

[0031] The matching closure of the isolation line 16 by connecting it to the unused other input 17 of the radar chip 2 provides better isolation compared to previously used closure solutions. The basic structure of the closure, the problem of closing the isolation line 16, has been known for a long time. At the same time, the design used in the present invention enhances the advantages of the solution according to the invention. The disadvantage of the previously known closures is that they require more space. The matching closure of the isolation branch 16 used in the present invention by connecting it to the other input 17 requires little space, and at the same time solves this problem in the case of the ultra-wideband duplexer structure 1 of the present invention.

[0032] It should be noted here that the ring hybrid circuit 8 used in the present invention is the design known from the art (Dr. Istvan Kasa: Microwave integrated circuits; Muszaki Kbnyvkiadb, 1978), with the exception of the non-uniformized symmetrical waveguide matching cutout 11 constituting the subject of the invention. That is, the geometric angle between the center line of the transmission-reception line 5 and the reception line 6, the geometric angle between the reception line 6 and the isolation line 16, and the geometric angle between the isolation line 16 and the center line of the transmission line 7 is 60 - 60°. The center line of the transmission-reception line 5 and the center line of the transmission line 7 fall in a straight line. The size of the ring hybrid circuit 8 is determined by the wavelength of the given signal, the thickness 15 of the microwave conductive film 4 and the relative dielectric constant of the substrate 3. Dimensioning this is the job of a specialist engineer based on the known relationships.

[0033] The design calculated in theory is optimized in practice with computer finite element simulation, since in practice it is not necessary to dimension it for a specific frequency or wavelength, but for a slightly wider range. The design can be optimized with simulation according to needs. The essential novelty of the invention is the design of the cutout 11 , the efficiency of which was optimized by computer finite element simulation and confirmed by measurements. The use of computer simulation can be expected from a person skilled in the art.

[0034] Accordingly, the optimal dimensions were determined using a so-called parametric simulation. This means that the rated sizes were defined as variables, and the computer, changing these variables finely and gradually, calculated the originating result we were examining for each size variant. From the set of results, the (desired) end result that was considered to be the most favorable was selected, and the corresponding base 12 and height 14 values were searched for. The parameters used in the parametric simulation are the base 12 and the height 14 of the cutout 11 , the thickness 15 of the conductive film 4 (Figures 2 and 3) and the thickness 19 and relative permittivity of the substrate 3.

[0035] Our aim with the simulation program is to establish a base 12 and height 14 value pair that provide maximum isolation in the specified frequency band between the transmission line 7 and the reception line 6. As little portion as possible of the power input to the transmission line 7 should go towards the reception line 6, because the power arriving here will deteriorate the reception parameters of the receiving unit. Furthermore, during transmission, as much portion as possible of the power input to the transmission line 7 as possible should go towards the transmission-reception line 5.

[0036] Parametric simulation is performed as follows. The basic parameters in the simulator (frequency band, center frequency, thickness 19 of the substrate 3, thickness 15 of the conductive film 4, and relative permittivity of the substrate 3) are set. A RatRace hybrid circuit is calculated based on the required knowledge of a microwave specialist.

[0037] At the branch position of the non-uniformized matching hybrid circuit, an isosceles triangle is cut out on its inner side, the base 12 of which is 1 to 3 times the thickness 19 of the substrate 3, its height 14 is 1 to 4 times the thickness 19 of the substrate 3, the relative permittivity of the substrate 3 is a known data. For example, in the case of the application of ISOLA MT77, this value is 3. Based on considerations, the base material of the substrate can be low-loss substrates even in the millimeter range. For example, the Rogers RO5880 and Rogers R03003 and the ISOLA MT77 are suitable for implementing a non-uniformized matching hybrid duplexer circuit.

[0038] First, during the parametric simulation, we select an arbitrary height value, based on what was described above, i. e. , a value between 1 and 4 times the substrate thickness 19. Then the value of the base 12 is changed between values 1 and 3 times the substrate thickness 19 in optional direction, starting at any value, in steps of 0.001 to 0.009 mm. Then, in the case of the selected optimal value of the base 12, the aperture angle of the cutout is given. With this aperture angle, the value of the height 14 is increased in steps of 0.001 - 0.009 mm, so that the position of the base 12 is constant with respect to the inner edge of the RatRace hybrid. After that, the value of the aperture angle is optimized similarly to the previous steps, and then the value of height 14 is changed in steps already described. If the optimal parameter ratios are found, the non-uniformized matching hybrid circuit can be made.

[0039] The measurement results are illustrated in Figures 4 and 5, where the frequency range of 75 - 83 GHz and the expected bandwidth of 3 GHz within the frequency range were given.

[0040] The diagram according to Figure 4 shows the reception reflection attenuation as a function of frequency during the optimization of the non-uniform compensation parameter when its base 12 was changed, between 0.01 mm — essentially without cutout 11 — and 0.38 mm in case of some cutouts 11. It can be seen that the cutout 11 causes more than 20 dB increase in reflection attenuation in the midband. At three points (1 , 2, 3) the related values of frequency and attenuation are indicated to support our statement.

[0041] The diagram of Figure 5 shows the isolation attenuation between transmission and reception as a function of frequency during the optimization of the non-uniform compensation parameter, when its base 12 was changed between 0.01 mm — essentially without cutout 11 — and 0.38 mm in case of some cutouts 11. It can be seen that the cutout 11 causes more than 10 dB of isolation attenuation increase in the midband.

[0042] Figure 6 shows the functions of the reflection factor of the reception line 6 as a function of the cutting angle. It can be seen in the figure that the curve of reflection factor number 16 shows a much more unfavorable — less reflection — attenuation than the optimal reflection factor curve number 15. The difference is very significant, 23 dB in the middle of the band. At the same time, the approximation represented by curves 3, 9 and 17 is less optimal and does not result in a significant increase in reflection attenuation.

[0043] Figure 7 shows the isolation attenuation of the reception line and the transmission line as a function of the cutting angle. The figure shows that the isolation attenuation curve number 16 shows a much less favorable, smaller isolation attenuation than the isolation attenuation curve number 15, which can be considered optimal. The difference in the middle of the band is 15 dB, which is significant. At the same time, the approximation represented by curves 3, 9 and 17 is less optimal; it does not result in a significant increase in isolation attenuation.

[0044] The diagram presented in Figures 6 and 7 shows that during the optimization, the cutting angle, i.e. , the size of the base 12, can be found, in the case of which a significant improvement in reflection factor and isolation can be observed.

[0045] Figure 8 shows the functions of the reflection factor of the reception line 6 as a function of the depth of the cutting. It can be seen in the figure that the reflection factor curve number 16 shows a much more unfavorable — less reflection — attenuation than the optimal reflection factor curve number 15. The difference is very significant, 23 dB in the middle of the band. At the same time, the approximation represented by curves 13 and 14 is less optimal, which does not result in a significant increase in reflection attenuation.

[0046] Figure 9 shows the isolation attenuation of the reception line 6 and the transmission line 7 as a function of the depth of the cutting. The figure shows that the isolation attenuation curve number 16 shows a much less favorable — smaller isolation — attenuation than the optimal isolation attenuation curve number 15. The difference in the middle of the band is 15 dB, which is significant. At the same time, the approximation represented by curves No. 13 and 14 is less optimal, which does not cause a significant increase in isolation attenuation.

[0047] The two diagrams according to Figures 8 and 9 show that during the optimization, the cutout depth, i.e. , the height 14, can be found, at which a significant improvement in reflection factor and isolation can be observed.

[0048] To support our statement, at three points (a, 0, y)the related values of frequency and attenuation are indicated.

[0049] Each diagram clearly supports the importance of the solution according to the present invention. It clearly shows that in case of the embodiment without cutout 11 the attenuation factor is much lower.

[0050] The advantage of the ultra-wideband duplexer structure according to the present invention is that it can be mass-produced with the microwave laminated plastic substrate described in the description, instead of an expensive sapphire or ceramic substrate. The technical solution with a cheap industrial BGA encased integrated circuit results in high attenuation between transmission and reception, and thus negligible intermodulation distortion, which significantly increases the detectability range of the radar thanks to the improvement of the signal-to-noise ratio.

[0051] The technical design can ensure high reflection attenuation in a bandwidth of several gigahertz.

Claims

Claims1 Non-uniform ized matching ultra-wideband duplexer structure (1 ) for mm wavelength frequency range, the structure consists of a ring hybrid circuit (8) and a radar chip (2), the ring hybrid circuit (8) is arranged on a microwave substrate (3) made of conductive film (4) and consists of a transmission-reception line (5) namely an excitation line, a reception line (6), a transmission line (7), an isolation line (16) and phase-shifting sections (9) arranged in a ring between the individual lines, the reception line (6) and the transmission line (7) are connected to the radar chip (2), characterized in that on the ring (13) formed by the phase shifting sections (9) arranged in the shape of a ring, at the branching of the receiving branch (6) and the isolation branch (16), a non- uniformized symmetrical waveguide matching cutout (11 ) is formed on the conductive film (4) of the ring (13) of the ring hybrid circuit (8) between at least two phase shifting sections (9), where the cutout (11 ) is in the shape of an isosceles triangle whose base (12) is perpendicular to the radius of the ring hybrid circuit (8), and the base (12) of the cutout (11 ) is closer to the center of the ring (13).2 Duplexer structure according to claim 1 characterized in that the isolation line (16) is connected to an unused, other input 17 of the radar chip 2.3 Duplexer structure according to claims 1 or 2 characterized in that shielding islands (10) are formed around the ring hybrid circuit (8).

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