EP1813032B1 - Antenna architecture and lc coupler - Google Patents

Abstract

Disclosed is an antenna architecture for the non-reacting connection of an antenna to a power amplifier, the antenna being connected to the power amplifier via a coupler. The inventive architecture is improved by the fact that the coupler is provided with an input gate for feeding the signal that is to be transmitted to the antenna while comprising a first and a second antenna gate for transmitting the signal to the antenna, the input gate and the load gate encompassing a joint gate terminal and the first and the second antenna gate being equipped with a joint gate terminal. Furthermore, the antenna comprises a first and a second, identically designed individual antenna, the first individual antenna being connected to the first antenna gate and the second individual antenna being connected to the second antenna gate. Additionally, an adjusted terminating resistor is connected to the load gate while the coupler transmits the signal to the first antenna gate at a phase angle of 0° and to the second antenna gate at a phase angle of 90°.

Description

The invention relates to an antenna architecture according to the preamble of patent claim 1.

In modern wireless communication systems, such as the UMTS mobile phone standard or in a wirelessly networked computer network, a so-called wireless local area network (WLAN), the digital data to be transmitted is transmitted via a gigahertz radio link. For example, in the UMTS standard frequencies between 1.900 and 2.170 GHz and for a WLAN frequencies around 2.4 GHz are used. For radio signals of these frequencies, the wavelengths are a few centimeters and thus in the microwave range. Radio signals of this wavelength are thus to be disturbed by comparatively small objects, with the interference of an object depending on the distance of the object to the antenna and on the electrical conductivity of the object. The smaller the distance of the object to the antenna and the greater its electrical conductivity, the more the radio signal emitted by the antenna is disturbed. In this case, the disturbance can on the one hand cause the propagation of the radio signal to be impaired, on the other hand, the radio signal can be deflected in its direction, in particular reflected, so that the reflected portion is directed back to the antenna, for example.

If necessary, and in particular in the event that a good electrical conductive object is located in the vicinity of the antenna, not only the emitted signals are disturbed by an object in their propagation, but it comes, for example by the small distance, also to changes in the antenna characteristic, in particular the input resistance of the antenna.

In practice, the antennas of such a UMTS or WLAN device are almost directly connected to a power amplifier, so that for optimum transmission of the transmission power between the power amplifier and the antenna, an adaptation of the resistors must be present. In the ideal state, if no disturbing object in the vicinity of the antenna changes the antenna characteristic, adaptation is present. If, however, the input resistance of the antenna changes, this leads to a change in the operating point of the power amplifier and the transmission behavior: In practice, the value of the Error Vector Magnitude (EVM value), which is used as a measure of the linearity deviation of high-frequency power amplifiers ,

To achieve a high data transmission rate, however, a linear transmission behavior of the upstream power amplifier must be achieved. A shift of the operating point of the power amplifier, which is accompanied by an increasing EVM value, is disadvantageous. Attempts to design a power amplifier so robust in its behavior that an electrically good conductive, close object does not affect the operating point, have so far been unsuccessful.

It is known in the art that in such systems so-called "isolators" are used which are connected between the antenna and the power amplifier and "isolate" the power amplifier from the antenna so as to prevent feedback to the power amplifier. These insulators thus cause the operating point of the power amplifier is not shifted from the ideal point. Furthermore, in addition to these existing passive components insulators to electronic control solutions worked in which electronic controllers are used. Such isolators and electronic control solutions are described for example in Bezooijen A., Chanlo Ch., Roermund, AHM, Adaptively Preserving Power Amplifier Linearity under Antenna Mismatch, IMS2004, Fort Worth.

The use of such known from the prior art isolators brings several disadvantages. Insulators are expensive, they require a lot of space and have a high weight compared to other components. Furthermore, they have a high attenuation, so that the output power output by the power amplifier is not optimally transmitted to the antenna and thus emitted. This leads to an increased power consumption by the amplifier and thus in particular in battery-powered mobile devices, such as UMTS mobile phones, so-called handsets, to the fact that the batteries or rechargeable batteries are quickly empty. Furthermore, the electronic control based insulators may tend to be unstable due to the feedback control loop, possibly causing further unwanted noise. The use of such isolators for decoupling the antenna from the power amplifier is thus possible, but associated with great disadvantages and difficulties.
A generic antenna architecture is from the WO 2004/051878 A1 and the US 3,375,524 known.

The object of the invention is thus to propose a reaction-free and adapted antenna architecture. To achieve this, a circuit is to be proposed which can be implemented with as few and simple components as possible.

To solve this problem is an antenna architecture with the features.

In the present context, the term "LC coupler" encompasses all coupler architectures which use lumped elements, ie concentrated components such as SMD components, thin-film or thick-film elements, semiconductor elements, capacitors or coils and similar assemblies.

The LC coupler has a load port at which a signal that is not emitted and reflected by an antenna can be coupled out, so that it is ensured in a simple and reliable manner that this reflected signal no longer reaches a power amplifier.

The proposed antenna architecture thus preferably consists of a four-core 0 ° / 90 ° LC coupler and an antenna, which is formed from two identical individual antennas and a termination or load resistor, which is adapted in its resistance of the system impedance. The input port of the LC coupler is connected to the power amplifier and the load port is terminated with the terminator. Each of the two identical individual antennas is connected to one antenna port each.

The LC coupler causes a wave entering the LC coupler from the output to ultimately be absorbed in the matched terminator. Thus, wave portions reflected on an object close to the antenna and received by one of the individual antennas are absorbed in the terminating resistor of the LC coupler and thus do not revert to the power amplifier. In this respect, the LC coupler acts for these from the output into the circuit incoming waves as an insulator with respect to the power amplifier, so that the 0 ° / 90 ° coupler forms an isolator antenna in conjunction with the two individual antennas.

For the simplest possible realization of such an antenna architecture, a 0 ° / 90 ° coupler is proposed alternatively or cumulatively, which has an input port, a load port and another first and another second port, each gate each of a first and a second Torklemme is formed. Between the Torklemmen adjacent gates are not in the working frequency range substantially effective, so ohmic or otherwise influence signals components so that two Torklemmen adjacent gates each coincide to a Torklemme and can form a common Torklemme, of course, negligible and never completely avoidable residual resistances, - inductances and capacities are present or may be present. Such an arrangement is referred to herein as short-circuited, so that the first gate terminal of the input gate and the first gate terminal of the first further gate are short-circuited, the second gate terminal of the input gate and the first gate terminal of the load gate are short-circuited, the second gate terminal of the first further gate and the first gate terminal of the second further gate are short-circuited and the second gate terminal of the second further gate and the second gate terminal of the load gate are short-circuited.

Thus, the first gate terminal of the input gate is preferably the first gate terminal of the first further gate and the second gate terminal of the input gate is the first gate terminal of the load gate. The second gate terminal of the first further gate is the first gate terminal of the second further gate and the second gate terminal is preferably the second gate terminal of the load gate. The 0 ° / 90 ° coupler thus has only four gate terminals.

The LC coupler is now characterized in that the first gate terminal of the input gate is connected via a first LC element to the second terminal of the second further gate and the second gate terminal of the input port is connected via a second LC element to the second gate terminal of the first further gate is, and that the dimensioning of the two LC-members in the intended working frequency range causes a phase shift of 90 ° between the two signal transmission paths.

In this way, the 0 ° / 90 ° coupler can be realized in particular with only two passive components which effect the desired phase shift in the signal transmission paths in the range of the operating frequency of the 0 ° / 90 ° coupler.

On the other hand, couplers are known as a way of connecting two signal-carrying circuits to one another in such a way that an exchange of the signals can take place. So in the literature, " Measuring Systems of High Frequency Technology ", Burkhard Schiek, Hütbig Verlag 1984 , a line coupler is mentioned as a possibility for defined signal attenuation or signal attenuation, and it is stated that couplers can be used to split signals into multiple ports. Finally, it is stated that line couplers can be used to generate two signals with broadband 90 ° phase shift. As an example, an abstract sketched ring coupler is given. Furthermore, a resistive coupler is mentioned, which has only resistances, ie purely ohmic resistors as coupler resistors and for which an example calculation for determining the attenuation is given. A phase shift between the gates is not possible with this resistive coupler due to the use of pure resistors. Finally, for this resistive coupler it is stated that the coupler resistances can also be complex. Thus, for example, one effective resistance can be replaced by an inductance and the other effective resistance can be replaced by a capacitance. Although the coupler would then be lossless and decoupled to a broadband gate, the coupling itself would become frequency-dependent.

The use of "lumped elements" makes it possible with the LC couplers according to the invention to limit the electrical length to 20 °. As a result, the corresponding coupler can be built very small and especially in mobile devices are readily used. On the other hand, it is understood that the limitation of the electrical length of the coupler to 20 ° or 18 ° or 15 ° in particular regardless of the use of "lumped elements" is advantageous to structurally small and robust antenna architectures for non-reactive connection of an antenna with a Power amplifier in which the antenna is connected via a coupler to the power amplifier, wherein the coupler for feeding the signal to be transmitted to the antenna has an input port and for transmitting the signal to the antenna, a first and a second antenna port, wherein the antenna a first and a second, identical single antenna, wherein the first individual antenna is connected to the first antenna port and the second individual antenna to the second antenna port, wherein the load port is completed, and wherein the coupler, the signal to the first antenna port with a first phase and the second antenna port mi t transmits a second, by 90 ° relative to the first phase shifted phase.

Figur 1:

eine schematische Schaltskizze der Antennenarchitektur;

Figur 2:

eine schematische Schaltskizze der Antennenarchitektur mit mehreren, in Reihe geschalteten 0°/90°-Kopplern;

Figur 3:

eine Schaltskizze eines 0°/90°-Kopplers; und

Figur 4

eine Schaltskizze eines -90°/90°-Dual-Band-Kopplers.

There are now several ways to design the antenna architecture according to the invention and the 0 ° / 90 ° LC coupler in an advantageous manner. Several preferred embodiments of the antenna architecture and the 0 ° / 90 ° LC coupler will now be described with reference to drawings. It shows

FIG. 1:

a schematic circuit diagram of the antenna architecture;

FIG. 2:

a schematic circuit diagram of the antenna architecture with multiple, connected in series 0 ° / 90 ° couplers;

FIG. 3:

a circuit diagram of a 0 ° / 90 ° coupler; and

FIG. 4

a circuit diagram of a -90 ° / 90 ° dual-band coupler.

FIG. 1 1 shows a schematic circuit diagram of the antenna architecture 1 with a 0 ° / 90 ° LC coupler, an antenna 3 formed from two identical individual antennas 3a, 3b and a terminating resistor 4. The input port 5 of the 0 ° / 90 ° LC coupler 2 is connected via the non-phase-shifting signal transmission path 6 with the first antenna port 7, to which the individual antenna 3a is connected. about the 90 ° phase-shifting signal transmission path 8, the input 5 is connected to the second Antennenausgangstor 9, to which the sub-antenna 3b is connected. At the fourth port of the LC coupler, the load gate 10, the terminating resistor 4, which is matched in its resistance value to the system impedance of the 0 ° / 90 ° coupler, is connected.

Now runs a wave from a power amplifier, not shown here via the input port 5 in the 0 ° / 90 ° coupler 2, it is transmitted to the one not on the phase-shifting signal transmission path 6 to the first antenna port 7 and thus to the sub-antenna 3a. On the other hand, the wave is transmitted via the 90 ° phase-shifting signal transmission path 8 to the second antenna port 9 and thus to the second sub-antenna 3b. The wave signal fed into the 0 ° / 90 ° coupler is thus split between the two signal transmission paths 6, 8 and emitted by the first subantenna 3a without phase shift and by the second subantenna 3b with a phase shift of 90 °.

Thus, each of the sub-antennas 3a, 3b must emit only half of the energy emitted by the power amplifier, so that thus the sub-antennas 3a, 3b must be designed for only half of the energy emitted by the power amplifier. Thus, the subantenna 3a, 3b must be designed compared to the classical solution with an antenna and insulators only for half the current carrying capacity, so that this antenna architecture can also be realized in media that was hardly possible for the classic design with an antenna. The arrangement is also much more robust against interference, since often only one of the two sub-antennas is detected by such a disorder.

Another advantage is that the directional characteristic of the antenna 3 can be optimized, so that, for example, in a mobile phone, the electromagnetic load of a user can be reduced.

The arrangement has the particular advantage that a wave reflected by an antenna or a wave traveling from the output into the circuit is absorbed in the terminating resistor 4 and thus is not reflected to the input port.

As LC coupler, for example, a 0 ° / 90 ° hybrid coupler can be used, which is particularly suitable when the subantenna 3a, 3b and the input port 5 are constructed in unbalanced line technology. It is understood that other 0 ° / 90 ° couplers can be used.

FIG. 2 shows a schematic circuit diagram of the antenna architecture 1 with a plurality of 0 ° / 90 ° -Koppplem connected in series. In this case, the power amplifier is connected to the input port 5 of the uppermost 0 ° / 90 ° coupler 2. To the load port 10 of the first 0 ° / 90 ° coupler 2, the input port 5 of the second 0 ° / 90 ° coupler is connected. A plurality of 0 ° / 90 ° couplers 2 can thus be connected in series one behind the other, wherein an input port 5 of a 0 ° / 90 ° coupler is always connected to the load port 10 of the preceding 0 ° / 90 ° coupler and thus forms the terminating resistor , Only the last 0 ° / 90 ° coupler 2 in the row must then be completed with a matching terminating resistor 4. The 0 ° / 90 ° couplers in this series connection can then be advantageously designed to be dimensioned for different, mutually adjacent operating frequencies, thereby forming an ultra broad band (UWB) antenna and so that the antenna architecture over a wide frequency range can be used. On the other hand, separate frequency bands can be controlled if the operating frequencies do not adjoin one another.

FIG. 3 shows a 0 ° / 90 ° coupler 2, which can be realized in the manner described above only with a capacitance 11 and an inductance 12, and thus can be referred to as LC coupler. Each gate of the LC coupler 2 is formed from two gate clamps. Each gate terminal of a gate is connected to a gate terminal of the respective adjacent gate via an ideal line, so that in each case two to one Torklemme coincide. Thus, for example, the gate terminal 5a of the entrance gate 5 is connected via an ideal line to the gate terminal 7a of the first further gate 7, so that these two coincide to form a common gate terminal. Likewise, the Torklemmen 7b and 10, 10b and 9b and 9a and 5b fall together in each case to a common Torklemme, so that the LC coupler 2 actually has only four gate terminals. The capacitance 11 and the inductance 12 are connected between these four gate terminals so that the capacitance 11, the common gate terminal of the input gate 5 and the first further gate 7 with the common gate terminal of the load gate 10 and the second further gate 9, and the inductor 12th the common gate terminal of the input 5 and the antenna gate 9 connects to the common gate terminal of the first further gate 7 and the second further gate 10.

The necessary for the function of the 0 ° / 90 ° coupler 2 phase shift is obtained for the intended operating frequency of the LC coupler via a suitable dimensioning of the capacitance 11 and the inductance 12, for the following a short example is carried out according to the known calculation rules ,

$${\mathrm{Z}}_2\mathrm{=}{\mathrm{\omega }}_{\mathrm{0}}\mathrm{L}$$

mit ω₀=2πf₀
Mit den für einen Resonanzkreis bekannten Bedingungen

1. 1. Z₁ + Z₂ = 0 und
2. 2. Z₁ * Z₂ = Z₀ ² lassen sich die Werte für die Induktivität L und der Kapazität C bestimmen zu $$\mathrm{L}\mathrm{=}{\mathrm{Z}}_{\mathrm{0}}\mathrm{/}\mathrm{2}{\mathrm{\pi f}}_{\mathrm{0}}\mathrm{=}\mathrm{3}\mathrm{,}\mathrm{97}\mathrm{nH}$$
   
   $$\mathrm{C}\mathrm{=}\mathrm{1}\mathrm{/}{{\mathrm{\omega }}_{\mathrm{0}}}^{\mathrm{2}}\mathrm{L}\mathrm{=}\mathrm{1}\mathrm{,}\mathrm{59}\mathrm{pF}$$
   

In this example, let the system impedance of the LC coupler be Z ₀ = 50 ohms and let the operating frequency be f ₀ = 2 GHz. The resistance Z _{1 of} a capacitance C and the resistance Z _{2 of} an inductance L can then be determined $${\mathrm{Z}}_{}$$$${\mathrm{}}_{\mathrm{1}}\mathrm{=}\mathrm{1}\mathrm{/}{\mathrm{\omega }}_{\mathrm{0}}\mathrm{<figure-callout\; id="2"\; label="C\; Z"\; filenames="imgf0001.png"\; state="\{\{state\}\}">C\; </figure-callout>}$$

$${\mathrm{Z}}_{}$$$${\mathrm{}}_2\mathrm{=}{\mathrm{\omega }}_{\mathrm{0}}\mathrm{L}$$

with ω ₀ = 2πf ₀
With the conditions known for a resonant circuit

1. 1. Z ₁ + Z ₂ = 0 and
2. 2. Z ₁ * Z ₂ = Z ₀ ² , the values for the inductance L and the capacitance C can be determined $$\mathrm{L}\mathrm{=}{\mathrm{Z}}_{\mathrm{0}}\mathrm{/}\mathrm{2}{\mathrm{\pi f}}_{\mathrm{0}}\mathrm{=}\mathrm{3}\mathrm{.}\mathrm{97}\mathrm{nH}$$
   
   $$\mathrm{C}\mathrm{=}\mathrm{1}\mathrm{/}{{\mathrm{\omega }}_{\mathrm{0}}}^{\mathrm{2}}\mathrm{L}\mathrm{=}\mathrm{1}\mathrm{.}\mathrm{59}\mathrm{pF}$$
   

With this dimensioning of the capacitance and the inductance, a phase shift of 0 ° or 90 ° is achieved for the selected operating frequency of 2 GHz. Thus, the LC coupler is a mono-band 0 ° / 90 ° coupler for a working frequency of 2GHz.

A special feature of this 0 ° / 90 ° coupler is that one point of this circuit may be connected to ground, resulting in two unbalanced gates. If, for example, the common door terminal of the input door 5 and the antenna door 9 is connected to ground, unbalanced components can be connected to these two gates. Thus, it is a 0 ° / 90 ° coupler 2 with integrated balun functionality.

If one interchanges the placement of capacitance 11 and inductance 12, this results in a 0 ° / -90 ° coupler, which can be used alternatively.

Furthermore, in this 0 ° / 90 ° coupler, the two individual antennas 3 a, 3 b and the input port 5 can be realized either in symmetrical ladder technology, or all three components must be realized in asymmetrical ladder technology. If, on the other hand, a component to be connected is designed to be asymmetrical with respect to the others, a balun must be connected between the gate and the component in a known manner in order to restore the symmetry. Here, for example, a so-called Balun (balanced - unbalanced) can be used, which can be implemented as a transformer, for example.

FIG. 4 shows a circuit diagram in which a mono-band coupler described above to a -90 ° / 90 ° dual-band coupler 13 is developed. Like the mono-band 0 ° / 90 ° coupler 2 described above, the -90 ° / 90 ° coupler 13 has an input port 5 and an antenna port 9 and a first further port 7 and a second further port 10. The inductance and the capacitance used in the 0 ° / 90 ° coupler are here by a parallel resonant circuit, which is formed from the inductor 17 and the capacitor 16, and a series resonant circuit consisting of the capacitance 14 and the inductance 15 is formed replaced. The operation for the two operating frequencies of the dual-band coupler 13 is equal to that of the LC and the CL coupler. For the lower of the two operating frequencies of the dual-band coupler 13, the dual-band coupler thus acts as a 90 ° coupler and for the higher operating frequency than -90 ° coupler. If one interchanges the parallel and the series resonant circuit in this variant of the coupler 13, then the dual-band coupler 13 behaves correspondingly at the lower operating frequency as a -90 ° coupler and at the higher operating frequency as a 90 ° coupler. The respective center frequencies of the two operating frequencies of the dual-band coupler must stand in no particular distance from each other.

Claims (2)

1. An antenna architecture (1) for non-reactive connection of an antenna (3) to a power amplifier, said antenna (3) being connected to said power amplifier through a coupler (2), said coupler (2) comprising an entrance gate (5) for feeding the signal to be transmitted to the antenna (3) as well as a first and a second antenna gate (7, 9) for transmitting the signal to the antenna (3), said antenna (3) comprising a first and a second individual antenna (3a, 3b), said first individual antenna (3a) being connected to the first antenna gate (7) and said second individual antenna (3b) being connected to the second antenna gate (9) and the coupler (2) transmitting the signal to the first antenna gate (7) with a first phase and to the second antenna gate (9) with a second phase, which is displaced 90° with respect to the first phase, characterized in that the coupler (2) is an LC coupler the gates of which are respectively formed from two gate terminals (5a, 5b, 7a, 7b, 9a, 9b, 10a, 10b), that said first and said second individual antenna are built identically and that said individual antennae (3a, 3b) are each implemented in symmetrical conductor technique, that the load gate (10) is terminated with an adapted terminating resistor and that the entrance gate (5) is built in non-symmetrical conductor technique wherein the gate terminals of the entrance gate (5) and of the antenna gate (9) are connected together and grounded for the coupler (2) to comprise an integrated balun function.
2. The antenna architecture (1) as set forth in claim 1, characterized in that the terminating resistor (4) comprises at least one additional coupler, preferably an additional LC coupler, with an antenna and that the additional coupler comprises an entrance gate for feeding the signal to be transmitted to its antenna and a first and a second antenna gate for transmitting the signal to its antenna and also a load gate, that its antenna comprises a first and a second individual antenna of identical construction, its first individual antenna being connected to its first antenna gate and its second individual antenna to its second antenna gate, that its load gate is terminated and that the coupler transmits the signal to its first antenna gate with a first phase and to its second antenna gate with a second phase displaced 90° with respect to the first phase.

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