EP1077508A2 - Indoor antenna with changeable antenna characteristics for communication with high data rates - Google Patents

Abstract

The antenna has drivable radiating antenna elements mounted on a base body. The base body (G) is in the form of a truncated cylinder (Z) with a polyhedron (K) mounted on it, whereby each surface of the polyhedron has an antenna element (E1,E2,E5). An Independent claim is also included for a method of operating an antenna.

Description

The invention relates to an antenna arrangement, in particular for an interior, according to the preamble of claim 1.

Such an antenna is used in the context of a communication application used in the interior area, such Antenna at the base station to transmit the data via the radio channel to the receiving units or terminals (downlink) is arranged. Data sent from the terminals (Uplink) are correspondingly from the antenna of the base station receive. Such data exchange occurs either between the base station and a specific terminal or all Terminals. One can therefore of a "directed" or speak "undirected" data exchange.

Realizations already exist for nationwide as well directed radio transmission. The non-directional or nationwide Radiation in a half-space can be, for example by means of monopoles, dipoles or patches with conductive planes or slots. Such Realization has the disadvantage that directly below no power is available to the antenna, however with specially shaped lens antenna this disadvantage is eliminated can be. Is the non-directional appearance constructive been set up, but it can be in the known antenna arrangements no longer in a directed broadcast switch.

The directional broadcast can be e.g. with array antennas, which consist of horns, dipoles or patches, realize. The direction of the largest antenna radiation through the properties of the radiating elements as well as through a feed network, which the amplitude and phase assignment of the individual radiation elements defined. In the simplest case, the network is fixed, so that the antenna characteristic generally does not change can be. A pivoting of the initially fixed Antenna beam can be made by inserting switchable detour lines can be realized, and also addressing everyone individual element may be possible. With the individual response the cost of each element increases significantly, however can generate almost any antenna characteristic become.

It is also from E. Gschwendtner et. al .: "Compliant, semicircular Array antenna for mobile users of future service integrators Satellite Systems ", ITG Technical Report 149, VDE publishing house, Berlin, Offenbach 1998, S.117-122, known, controllable Patch elements on a hemispherical or cylindrical Position the surface of a body, where the individual patch elements are switchable.

The invention has for its object an antenna, preferably for the interior, the generic type too create that easily between nationwide and directional antenna characteristic is switchable, and to provide a method for operating such an antenna.

According to the invention, this object is achieved by the characteristics of the antenna according to claim 1 and the method according to claim 13 solved. Preferred embodiments of the invention are objects of subclaims.

According to the invention, an antenna comprises a base body with a Variety of radiating antenna elements, the Base body in the form of a cylinder with an attached polyhedron and each polyhedron surface has an antenna element. The attached polyhedron is preferably formed by a truncated cone formed, depending on the number of antenna elements used flattened on the sides (four, six, eight ...) is. This creates several flat surfaces, the fixed angular relationships to each other. The size of the angle will by calling for an optimal nationwide Characteristics, as well as after low radiation against the ceiling and walls given.

However, it is also possible to pass through the attached polyhedron an approximate one with corresponding flats Hemisphere to use.

About the spatial arrangement of the radiating elements a first alignment of the radiation. Through the the simultaneous excitation of several radiating elements Directivity can be changed during operation. One at known pivoting antennas usual variation of the directional characteristic due to amplitude / phase weights is unnecessary here.

Individual radiating elements can be used to change the directivity can be switched on or off. For the nationwide To radiate, all radiating elements must have a fixed default Have phase relationship to each other. To do this without additional Alignment or calibration measurements reproducible and without realizing production-related fluctuations, the entire network is on a continuous substrate manufactured. Thanks to the special base body apply the two-dimensional substrate three-dimensionally. The This can be done mainly on the cylindrical network Part will be housed, with the network consisting of a flexible Substrate is produced.

The individual radiant elements on the flattened Sides of the body are positioned over individual continuous conductor tracks fed.

The substrate is glued to the surface of the base body or screwed on. The correct positioning is ensured by bores in the base body and in the substrate.

Round by using asymmetrically wide ground surfaces around the individual patches it is possible to set the distances between to choose the patches minimally, with which an omnidirectional Realize the characteristic with a ripple of less than 3 dB leaves.

With monopole emitters on a reflector or with symmetrical emitters mounted on cylinder surfaces always along the axis of the emitter or the cylinder a zero in the antenna characteristic with area coverage Radiation. With the present antenna can this by means of a fixed, slightly asymmetrical excitation of the individual radiating elements can be eliminated.

Determining the direction from which the terminal station is sending can be done simply by measuring the individual elements. To complex signal processing, as in known Antennas is necessary, can therefore be dispensed with.

Advantageously, in the antenna according to the invention Production and assembly effort low. Hence the antenna versatile and affordable.

The number of radiating elements used is arbitrary. The more elements are used, the more directed radiation lobes can be set up. As radiant elements can directly- as well as radiation-coupled patch elements or broadband dipoles can be used. So that can the relative frequency bandwidth and the polarization of the antenna adapt to the required specification. By a simultaneous excitation of several patches can be additional Form antenna lobes, with which an adaptation to the spatial conditions or to the requirements of the communication network is possible during operation. The antenna can not only at base stations, but because of their cost-effectiveness can also be used at terminals.

There are several alternatives as network structures:

If mainly extensive radiation is planned, can a symmetrical network e.g. used with Wilkinson dividers become. Only one RF lead is required here. The Switching logic can be integrated directly on the HF substrate.

For a directional broadcast is a more complex network advantageous. The individual radiating elements can with higher performance. An external switch board is with the antenna board over several RF lines connected. The digital logic is also on this switch board realized and the switching signals are sent to the Hand over the antenna board.

The following are also possible: More complex networks where by switchable amplitude and / or phase weights further influence on the directional radiation can be. Freely adjustable amplitude and / or phase weights can be in the antenna base body according to the invention also realize. There are also mixed forms of the above Alternatives conceivable.

In summary, the use of several, partially independent or intelligently switchable Feed routes selected by simple switching the desired directionality of the antenna is switched on and over. All networks, as well as the digital control circuit, are housed on a substrate, eliminating all phase relationships are reproducibly specified. The spatial orientation the patch elements to each other is identified by a special shaped base body allows and this without additional Adjustment. The versatile antenna is also inexpensive.

Fig. 1 zeigt eine erfindungsgemäße Antenne in schematischer Ansicht,

Fig.2 zeigt ein Schema eines Kommunikationssystems,

Fig.3 zeigt eine zeitliche Rahmenstruktur für die Kommunikation eines Kommunikationssystems nach Fig. 2,

Fig.4 stellt eine Kommunikation einer Basisstation mit den Terminals dar,

Fig.5 zeigt ein erstes Netzwerk einer erfindungsgemäßen Antenne , und

Fig.6 zeigt ein zweites Netzwerk einer erfindungsgemäßen Antenne.

Preferred embodiments of the invention are explained in more detail below with reference to the drawings.

1 shows an antenna according to the invention in a schematic view,

2 shows a schematic of a communication system,

3 shows a time frame structure for the communication of a communication system according to FIG. 2,

4 represents a communication of a base station with the terminals,

5 shows a first network of an antenna according to the invention, and

6 shows a second network of an antenna according to the invention.

1 shows an embodiment of an antenna according to the invention shown. The antenna has a base body G which consists of a cylindrical part Z and a part placed thereon Truncated cone K exists. In the most general form of The antenna becomes a corresponding polyhedron instead of the truncated cone K used. The truncated cone K has in the embodiment 1 four flattenings (or six, eight, ...) according to the number of radiating elements, whereby only the radiating elements E1 and E2 are shown are visible. On top of the truncated cone K is another one Surface essentially perpendicular to the truncated cone axis arranged, which also has a radiating element E5. The spatial positioning of the radiating elements E1, E2, ..., E5 is ensured by the base body G. The polarization of the antenna is due to the orientation with the radiating elements E1, E2, ..., E5 on the base body G are attached, and by the choice of elements fixed. As radiating elements E1, E2, ..., E5 can all structures that can be made planar, e.g. Patch or Dipoles are used. It is also on the cylindrical Part Z of the base body G applied a substrate S, which Contains supply network for the radiating elements.

2 shows an overview of a communication system under Use of an antenna according to Fig. 1 presented. In particular, a constellation within a "point to multipoint "system. The antenna, not separately here is used at the base station BS. For example, the antenna is mounted on a ceiling and should have a direct line of sight to the terminals shown T1, T2, T3, T4, Tn. Possibly due to a Obstacle H a reflector R can be used like this is the case for Terminal T4. The antenna communicates with an indefinite number n of terminals. Their positions can change during communication.

3 shows a basic frame structure for communication between the base station and the terminals of a system 2, wherein time slots for data transmission be used. Downlink DL contains data D from the base station BS to the terminals T1, T2, ..., Tn. It sends information that is common to all terminals are important and are called broadcast BC namely in time slot 0, as well as those that are only for individual Terminals are determined, namely data D in the time slots D1, D2, D3, etc. For the broadcast BC case in the time slot 0 a nationwide broadcast is necessary. At the time slots D1, D2, D3, ... for data transmission D on the other hand, a directed radiation offers the advantage that Reflections and fading effects are reduced, in the uplink UL becomes data D directly from the terminals to the base station transfer. Each terminal sends on its own time slot U1, U2, U3, ... data D. Since known at the base station BS is where the individual terminals are, is for time slots U1, U2, U3, ... a directional antenna characteristic used. A random access channel RAC with time slots R1, R2, R3, ... of the frame enables the booking new terminals at the base station BS. Because at the base station BS this time is not known where the individual terminals must stand for time slots R1, R2, R3, ... with the nationwide Antenna characteristics are worked.

4 shows a possible situation of communication of the Base station BS shown with the terminals T1, T2, T3, T4. An antenna with 4 elements E1, E2, E3, E4 is used, define the 4 sectors S1, S2, S3, S4. For your understanding the functioning of the antenna and its integration in the system there follows a short communication sequence illustrated.

Frame 1:

D1 → T1 ⇒ BS sendet auf E1   U1 → T1 ⇒ BS empfängt auf E1

D2 → T1 ⇒ BS sendet auf E1   U2 → T2 ⇒ BS empfängt auf E2

D3 → T2 ⇒ BS sendet auf E2   U3 → T2 ⇒ BS empfängt auf E2

The terminals T1 and T2 are known. Base station BS broadcasts the use of the channels in time slot 0:

D1 → T1 ⇒ BS sends on E1 U1 → T1 ⇒ BS receives on E1

D2 → T1 ⇒ BS sends on E1 U2 → T2 ⇒ BS receives on E2

D3 → T2 ⇒ BS sends on E2 U3 → T2 ⇒ BS receives on E2

Terminal T3 has listened to time slot 0 and is logging on the base station BS in time slot R1. Base station BS receives with omnidirectional, i.e. nationwide, characteristic and finds that the signal from Terminal T3 with antenna element E3 is best received.

Frame 2:

D1 → T1 ⇒ BS sendet auf E1   U1 → T1 ⇒ BS empfängt auf E1

D2 → T2 ⇒ BS sendet auf E2   U2 → T2 ⇒ BS empfängt auf E2

D3 → T2 ⇒ BS sendet auf E2   U3 → T3 ⇒ BS empfängt auf E3

D4 → T3 ⇒ BS sendet auf E3

Terminals T1, T2 and T3 are known. Base station BS broadcasts the use of the channels in time slot 0:

D1 → T1 ⇒ BS sends on E1 U1 → T1 ⇒ BS receives on E1

D2 → T2 ⇒ BS sends on E2 U2 → T2 ⇒ BS receives on E2

D3 → T2 ⇒ BS sends on E2 U3 → T3 ⇒ BS receives on E3

D4 → T3 ⇒ BS sends on E3

T2 moves from sector 2 to sector during transmission 1. Even if ES receives on E2, the reception level or the RSSI (Received Signal Strength Information) of the others Antenna elements evaluated. BS now notes that the Receive signal from T2 to E1 becomes stronger than to E2. in the next frame then E1 is used for T2. A variant is the introduction of a hysteresis regarding the reception power the antenna branches to avoid switching too often. This ensures that the terminals are adjusted accordingly.

5 shows a network which is used for small radio cells, where only a few participants are addressed must be easy to implement. For example, by Wilkinson divider W1, ..., W3 a constant power output of the individual radiating elements E1, ..., E4 independently ensured by the operating mode. The digital circuit arrangement to control the individual switches S1, ..., S4 can can be integrated directly on the HF substrate. Through the control the corresponding switches S1, ..., S4 can also several radiating elements E1, ..., E4 excited simultaneously become, whereby additional directional lobes can be formed.

In Figure 6 a network is shown that is more suitable is when very many different characteristics are formed should be, or if in the directional radiation as much power as possible should be available. Be here the individual radiating elements E1, ..., E6 each with operated at maximum power. The effort that went into it is slightly higher because of an additional one Circuit board for the digital part, as well as for a first one HF switching step (1 on 4 - switch in the upper left part 6) and several RF feed lines 1, ..., 4 are required. Depending on whether the radiating elements E1, ..., E6 can only be operated individually or in combination switches at the distribution points T1, ..., T3, for example or Wilkinson divider can be used. In the connecting lines between the distribution points T1, ..., T3 and the Switches S1, ..., S6 can also be switched phase shifters install. Or e.g. at the distribution points T1, ..., T3 performed an asymmetrical power distribution, around special directional characteristics in this way fixed. So that different, exactly on that tailored variants are generated for each area of application. In both variants, the networks are designed that the line lengths to the radiating elements for the omnidirectional characteristics are all the same length, so in order Exclude phase errors caused by different lengths Paths are caused. As a variant, Length differences of the lines of multiples of the wavelength use this is possible as long as the frequency bandwidth is low, and the omnidirectional characteristic over the frequency range within that for the respective application specified specifications remains.

Claims (16)

Antenna, in particular for the interior, with controllable radiating antenna elements arranged on a base body,
characterized in that the base body (G) has the shape of a truncated cylinder (Z) with an attached polyhedron (K), each surface of the polyhedron (K) having an antenna element (E1, E2, E3, E4, E5). Antenna according to Claim 1, characterized in that the polyhedron (K) is formed by a truncated cone which has a number of flattened sides. Antenna according to claim 2, characterized in that the number of flattened sides is an even number greater than or equal to 4. Antenna according to one of claims 2 or 3, characterized in that the cone tip is designed as a surface and has an antenna element (E5). Antenna according to one of the preceding claims, characterized in that the antenna elements (E1, E2, E3, E4, E5) are designed as structures which can be produced in a planar manner. Antenna according to Claim 5, characterized in that the structures which can be produced planar are dipoles or patches. Antenna according to one of the preceding claims, characterized in that the antenna for each radiating antenna element (E1, E2, E3, E4, E5) has a switch (S1, S2, S3, S4) which switches each radiating antenna element (E1, E2, E3, E4, E5) separately on or off. Antenna according to claim 7, characterized in that the switches (S1, S2, S3, S4) are part of an antenna network. Antenna according to Claim 8, characterized in that the network has Wilkinson dividers (W1, W2, W3). Antenna according to one of claims 8 or 9, characterized in that the network is applied to a continuous flexible substrate (S). Antenna according to Claim 10, characterized in that the substrate is applied predominantly or entirely on the cylindrical part of the base body (G). Antenna according to one of claims 10 or 11, characterized in that the substrate (S) is adjusted by corresponding adjustment bores in the base body (G) and substrate (S). Method for operating an antenna according to one of the preceding claims in a point-to-multipoint communication system with a base station (BS) and at least one terminal (T1, T2, T3, T4, Tn), characterized in that for communication between the base station (BS ) and terminals (T1, T2, T3, T4, Tn) a frame structure of time slots (0, D1, ..., U1 ..., R1 ...) is used, with a first predetermined number of time frames for the downlink (DL), a second predetermined number of time slots for the uplink (UL) and a third predetermined number of time slots for a random access channel (RAC). A method according to claim 13, characterized in that an area-covering antenna characteristic is used in the downlink (DL) for the data which is important for all terminals, while a directional antenna characteristic is used for data which are directed to booked terminals. Method according to Claim 14, characterized in that a directional antenna characteristic is used for the uplink (UL) of terminals which have already been booked in. Method according to one of claims 13 - 15, characterized in that a surface-covering antenna characteristic is used for the random access channel (RAC).

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