EP2178155A1 - Directional coupler with compensation of direction accuracy with target error adjustment - Google Patents

Abstract

The coupler (30) has a first connection (10) for coupling a signal to a second connection (13) with high attenuation, and a third connection (11) for coupling the signal to the second connection with small attenuation. The second connection is connected with a terminating impedance (20). The impedance is dimensioned such that the impedance causes a target error adjustment of the second connection and reflection of portion of the signal at the second connection. The signal applied to the connection and the signal reflected at the connection are interfered in a partially destructive manner.

Description

The invention relates to a directional coupler for directional transmission of high-frequency signals.

The state of the art is here, for example, on the US 5,424,694 directed. In this a directional coupler is described, which is constructed in stripline technology on a substrate level. Ohmic resistances and inductances influence the frequency response of the directional coupler. A targeted electrical extension of the coupled lines is performed. However, a superposition of signals to exploit interference does not take place.

Conventionally coupled lines are used in directional couplers. With a single-layer construction on a printed circuit board, however, only small sharpening can be achieved. Conventionally, the terminations of directional couplers are matched as closely as possible to the desired terminating resistor of typically 50Ω. This also goes from the US 5,424,694 out. This results in a useful for most applications directivity.

A directivity of more than 30 dB can be achieved with conventional construction only with a three-layered or mechanically very complex structure or by an explicit optimization of the directivity of each directional coupler during manufacture.

The invention is based on the object to provide a directional coupler, which achieves a high level of quality with low production costs and small footprint.

The object is achieved for the device by the features of independent claim 1. Advantageous developments are the subject of the dependent claims.

A directional coupler has at least four terminals and a termination impedance. The directional coupler is configured to couple signals from a first terminal to a third terminal with low attenuation, and to couple signals from a second terminal to the third terminal with very high attenuation. Furthermore, the directional coupler is configured such that signals from the first terminal couple to a fourth terminal with very high attenuation and that signals from the second terminal couple to the fourth terminal with low attenuation. The fourth connection is connected to the terminating impedance. The termination impedance is dimensioned to cause a targeted mismatch of the fourth terminal and a reflection of a portion of a signal received at the fourth terminal. The signal reflected at the fourth terminal and a signal applied to the third terminal interfere at least partially destructively. This ensures a very high level of directivity with low frequency selectivity and low production costs. Even a small footprint is the result.

The termination impedance is preferably further dimensioned such that it has a phase difference of the fourth terminal reflected signal compared to the signal input to the third terminal of 180 ° causes.

Advantageously, the directional coupler includes at least two strip lines. A first stripline preferably connects the first terminal to the second terminal. A second stripline preferably connects the third terminal to the fourth terminal. The two stiffening lines are preferably arranged in spatial proximity to one another. This makes it possible to use common directional couplers. Stripline directional couplers are also very easy to manufacture and only require a small footprint.

The terminating impedance is preferably an ohmic resistance and / or an inductance and / or a capacitance. Thus, for different phase differences of the coupled signals and different amplitudes, the optimal termination impedance can be selected.

The terminating impedance is preferably dimensioned such that the amplitudes of the signal reflected at the fourth terminal and the signal arriving at the third terminal are substantially identical.

The directional coupler is advantageously constructed in such a way that signals coupled from the first terminal or the second terminal to the third terminal and to the fourth terminal are phase-shifted by a certain angle. Thus, the termination impedance can be selectively selected to make the phase difference of the signal reflected at the fourth terminal from the signal input at the third terminal to 180 °.

The directional coupler is preferably constructed in such a way that signals coupled from the first connection or the second connection to the third connection and to the fourth connection are phase-shifted by 180 °. Thus, an adjustment of the phase shift by the terminating impedance is not necessary.

Fig. 1

einen beispielhaften Richtkoppler, und

Fig. 2

ein Ausführungsbeispiel des erfindungsgemäßen Richtkopplers.

The invention will be described by way of example with reference to the drawing, in which an advantageous embodiment of the invention is shown. In the drawing show:

Fig. 1

an exemplary directional coupler, and

Fig. 2

An embodiment of the directional coupler according to the invention.

First, based on the Fig. 1 an exemplary directional coupler and its operation explained. through Fig. 2 Subsequently, the structure and operation of the directional coupler according to the invention is illustrated. Identical elements have not been repeatedly shown and described in similar figures.

In Fig. 1 an exemplary directional coupler 1 is shown. A first strip line 2 has the connections 10, 11. A second strip line 3 has the connections 12, 13. The two strip lines 2, 3 are arranged in a large spatial proximity on a substrate, not shown here. Signals applied to terminal 10 couple with low attenuation to terminal 12, and high attenuation to terminal 13. Signals applied to terminal 11 couple with less Damping to port 13, and high damping to port 12.

For example, a signal is applied to terminal 11. The signal is applied to the first stripline 2 and couples to the second stripline 3. Since the terminals 12, 13 of the second stripline 3 are not terminated in this example, a significant portion of the signal coupled to the terminal 13 is reflected. This significantly deteriorates the directivity of the directional coupler. By an adapted termination on the terminal 13, this can be avoided to some extent. However, such a conclusion is frequency-selective, which causes a frequency dependence of the directivity.

Fig. 2 shows an embodiment of the directional coupler according to the invention. As well as in Fig. 1 The directional coupler 30 shown here has the connections 10, 11, 12, 13. The directional coupler according to the invention additionally includes a terminating impedance 20 connected to the connection 13. The terminating impedance 20 is furthermore connected to a ground connection 21. Within the directional coupler 30 according to the invention, a conventional directional coupler 1 is used. This can be both a stripline directional coupler, as in Fig. 1 represented, as well as any directional coupler be of a different design.

In a plurality of directional coupler types results in a phase difference of the two terminals 12, 13 coupled signals. This is usually 180 °. However, there are also known directional couplers, in which the Phase difference assumes other values. Directional couplers without the mentioned phase difference are known.

Assuming the phase difference is exactly 180 °, according to the invention a pure ohmic resistance is connected as a terminating impedance 20 to the terminal 13.

For example, if a signal is applied to terminal 11 it will couple with little attenuation, e.g. -20dB to port 13 and with high attenuation, e.g. -35dB to port 12. With optimum directivity, no signal component would be measurable at port 12. In order to come as close as possible to this ideal state, the terminal 13 is selectively mismatched by the terminating impedance 20. This results in the reflection of a part of the signal applied to the terminal 13. The terminating impedance 20 is selected such that the attenuation of the signal reflected at the terminal 13 corresponds to the attenuation of the signal coupled to the terminal 12. In this example, both attenuations are set to -35dB. By the caused by the exemplary directional coupler 1 phase difference of 180 ° occurs destructive interference; the signals cancel.

Suppose that caused by the directional coupler 1. Phase difference is less than 180 °, so this phase difference must be adjusted by means of the terminating impedance 20. By using inductors, capacitors and ohmic resistors, a phase jump of the reflected signal at the terminal 13 is intentionally caused. However, such an artificially induced phase shift has a certain frequency selectivity. An optimal directivity is thus only in a small frequency range too achieve. Preferably, a terminating impedance is used which is lower than in the case of a matched termination. A phase jump is achieved so reliably.

The invention is not limited to the illustrated embodiment. As already mentioned, different directional coupler types can be used. A mismatch of further connections according to the invention is also conceivable. All features described above or features shown in the figures can be combined with each other in any advantageous manner within the scope of the invention.

Claims (7)

Directional coupler (30) having at least four terminals (10, 11, 12, 13) and a terminating impedance (20),
wherein the directional coupler (30) is configured to couple signals from a first port (10) to a third port (12) with low attenuation, and that signals from a second port (11) to the third port (12) are high Coupling attenuation and coupling signals from the first port (10) to a high attenuation fourth port (13) and coupling signals from the second port (11) to the fourth port (13) with low attenuation,
wherein the fourth terminal (13) is connected to the terminating impedance (20),
characterized,
that the terminating impedance (20) is dimensioned such that it causes a targeted mismatch of the fourth terminal (13) and a reflection of a portion of a signal at the fourth terminal (13), and
in that the signal reflected at the fourth connection (13) and a signal present at the third connection (13) interfere at least partially destructively. Directional coupler according to claim 1,
characterized,
in that the terminating impedance (20) is further dimensioned such that it causes a phase difference of the signal reflected at the fourth terminal (13) from the signal from the third terminal (12) of 180 °. Directional coupler according to claim 1 or 2,
characterized,
in that the directional coupler (30) contains at least two strip lines (2, 3),
that a first strip line (2) said first terminal (10) to the second terminal (11),
that a second strip line (3) to the fourth port (13) connects the third terminal (12), and
that the two casting lines (2, 3) are arranged in spatial proximity to each other. Directional coupler according to one of claims 1 to 3,
characterized,
that the terminating impedance (20) is an ohmic resistance and / or inductance and / or capacitance. Directional coupler according to one of claims 1 to 4,
characterized,
in that the terminating impedance (20) is dimensioned such that the amplitudes of the signal reflected at the fourth terminal (13) and the signal arriving at the third terminal (12) are substantially identical. Directional coupler according to one of claims 1 to 5,
characterized,
in that the directional coupler (30) is constructed in such a way that signals coupled from the first terminal (10) or the second terminal (11) to the third terminal (12) and to the fourth terminal (13) are phase-shifted by a certain angle. Directional coupler according to one of claims 1 to 6,
characterized,
in that the directional coupler (30) is constructed in such a way that the first connection (10) or the second connection (11) to the third terminal (12) and to the fourth terminal (13) coupled signals are 180 ° out of phase.

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