EP3493324A1 - Active multi-band antenna for terrestrial broadcast reception - Google Patents

Abstract

The invention relates to an active multiband antenna for terrestrial radio reception, comprising receiving structures consisting of loop and stitch-shaped conductor tracks, which are arranged on a dielectric carrier (4), as well as matching circuits, frequency filters, balancing members and amplifier circuits provided in the connection areas of the receiving structures. According to the invention, a first and a second loop-shaped conductor track are formed for a first and a second frequency band. The corresponding loop-shaped conductor tracks are connected to frequency filters and the output signals are made available band-selectively via baluns and amplifiers. Parallel to the longer extension of a first loop-shaped conductor track for the FM range, a monopole stub line is provided for the AM frequency band.

Description

The invention relates to an active multiband antenna for terrestrial radio reception, comprising receiving structures, consisting of loop and stitch-shaped conductor tracks, which are arranged on a dielectric support, and provided in the terminal areas of the receiving structures matching circuits, frequency filters, baluns and amplifier circuits according to the preamble of the claim 1.

From the US Pat. No. 4,791,426 B1 or the US Pat. No. 6,215,450 B1 Rear window antennas are already known. In the case where, for example, pressure-applied heating elements of the pane are used as antenna radiators, decoupling filters are necessary in order to separate the heating direct current from the high-frequency signals. Such decoupling filters are bulky and expensive. In the case of defective heating conductor loops, the antenna loses the desired efficiency or its function as a whole.

From the DE 34 10 415 A1 is an active antenna for the rear window of a vehicle previously known. This antenna is intended to provide AM reception in the long, medium and shortwave bands as well as FM reception, ie in the FM band. In this antenna, another, with the heating field galvanically not connected, areal trained antenna conductor is generated on the disc. This antenna conductor is connected to the connection of an input terminal of a low-noise amplifier with capacitive high-impedance input resistance. The ground connection of the antenna amplifier is connected via a short line to the border of the conductive part of the rear window. The corresponding distances and transverse dimensions of the antenna conductor based on the boundary and the heating field itself are subject to a specific dimensioning, which is vehicle-specific and can not be optimized for all frequency and reception conditions.

From the WO 02/05236 A1 An active antenna is previously known, which comprises loop-shaped conductor tracks and wherein an interruption bridged by a capacitor or a connection region is provided. In the connection area, the primary side of a matching transformer is connected, whose secondary side leads to an amplifier circuit.

The state of the art still includes the DE 10 2010 010 371 B4 , From this document an active antenna for multi-frequency diversity reception comprising a loop-shaped conductor track with a bridge bridged by a breaker and a connection area is already known, wherein in the connection area, the primary side of a matching transformer is connected, whose secondary side leads to an amplifier circuit. The loop-shaped conductor is in communication with a stub, wherein the remote from the loop-shaped conductor end of the stub is connected to the secondary side of the matching transformer, so that by the choice of the connection point between the stub and the loop-shaped conductor a vote on the electric field component and the relevant input impedance of the amplifier circuit in the FM area is done.

Based on the described prior art, it is an object of the invention to provide a further developed active multiband antenna for terrestrial broadcasting on the basis of loop-shaped interconnects, which largely dispenses with elaborate adaptation of transformers and which is capable of optimal reception properties with sufficient selectivity To ensure completely different frequency ranges or frequency bands, wherein the surface area of the multiband antenna is as small as possible in order to arrange them in particular as a multi-band adhesive antenna at a variety of locations, in particular a motor vehicle.

The object of the invention is achieved with an active multiband antenna according to the combination of features according to claim 1, wherein the Subclaims represent at least expedient embodiments or a preferred application.

It is therefore assumed that an active multiband antenna, which is intended for terrestrial broadcasting.

This active multiband antenna comprises receiving structures, consisting of loop and stitch-shaped conductor tracks, which are arranged on a dielectric support. Furthermore, matching circuits, frequency filters, baluns and amplifier circuits are provided in terminal areas of the receiving structures.

The active multiband antenna is earth-symmetrical and does not need a ground connection to the vehicle body, which simplifies mounting the antenna to the vehicle.

According to the invention, a first loop-shaped conductor track is designed to be tuned to a first frequency band FM. This first loop-shaped track has an interruption located at an end remote from the antenna port.

The interruption is bypassed with a first matching circuit.

In the connection region of the first loop-shaped conductor track, the connection ends of which are closely adjacent, a first and a second frequency filter are provided which have a high load impedance for the first loop-shaped conductor track in the second frequency band (DAB) and thereby minimize their near-field coupling to a second loop-shaped conductor track ,

The respective outputs of the first and the second frequency filter are connected to the balanced inputs of a first balun, the unbalanced output of the balun being applied to the input of a first amplifier.

The output of the first amplifier forms the output terminal for the first frequency band FM.

The second loop-shaped conductor track, which is designed to be matched to the second frequency band DAB, is arranged delimited from the first loop-shaped conductor track on the dielectric carrier.

In the connection region of the second loop-shaped conductor track for the second frequency band DAB, a second and a third matching circuit is provided, the respective output of which leads to a third and a fourth frequency filter. In the first frequency band FM, these frequency filters have a high load impedance for the second loop-shaped conductor track and can thereby minimize their near-field coupling to the first loop-shaped conductor track (1).

The respective output of the third and fourth frequency filter is connected to the balanced inputs of a second balun.

The unbalanced output of the second balun is applied to the input of a second amplifier. The output of the second amplifier now forms the connection for the second frequency band DAB.

Furthermore, a monopole stub tuned to a third frequency band AM is formed essentially parallel to the longer extent of the first loop-shaped conductor track. The feed end of the monopole stub is connected to the input of a third amplifier via a frequency filter. The output of the third amplifier forms the connection for the third frequency band AM.

In a development of the invention, the loop-shaped conductor tracks have a substantially rectangular design.

In this case, the first loop-shaped conductor track can surround the second loop-shaped conductor track at a distance, so that, as it were, an interleaving is present.

The conductor tracks preferably form a planar structure.

In an embodiment of the invention, the dielectric support has a layer or a coating for bonding to a particular plastic or glass surface.

The connections for the respective frequency bands can be formed as separate coaxial outputs.

Alternatively, it is possible to form the outputs for the frequency bands completely split or for at least two frequency bands.

The length of the loop-shaped conductor tracks is preferably ≦ 0.2 times the smallest wavelength of the respective desired reception range.

In a preferred development of the invention, all essential antenna components can be arranged on a dielectric foil wiring carrier.

This film wiring support can then have the already mentioned adhesive coating on one side in order to accomplish bonding in the sense of a glass adhesive antenna.

According to the invention, moreover, the application of the presented multiband antenna for the field of motor vehicles, here again in particular for cars, motorhomes, buses or commercial vehicles.

The invention thus represents a highly integrated active multiband antenna system for the terrestrial radio reception of the frequency bands FM, DAB and AM and starts from a first and a second loop-shaped conductor track.

The first loop-shaped track has an interruption bridged by a matching circuit and a connection area.

The connection region is connected via the aforementioned frequency filters, which are provided for the decoupling of the FM and DAB reception structures, to the first balun, the output of which is connected to the input of an amplifier circuit, which in turn represents the output of the antenna system for the first frequency band FM.

The first loop-shaped conductor path delimits the second loop-shaped conductor track and surrounds this in a preferred embodiment.

The ends of the second loop-shaped track are connected by matching circuits for the second frequency band DAB and by means of frequency filter for the first frequency band FM with the balanced inputs of a second balun, whose unbalanced output is connected to the input of a second amplifier.

The output of the second amplifier in turn forms the output of the antenna system for the second frequency band DAB.

Particularly according to the invention, the approach is to arrange a monopole parallel to the longer side of the first loop-shaped conductor track, one end of which is connected via a frequency filter to the input of a third amplifier whose output forms the output of the antenna system for the AM frequency band.

The presented multiband antenna is due to their planar structure and the compact design and the existing decoupling particularly suitable for applications in the field of automotive technology and in particular independent of the type of vehicle body.

The invention will be explained below with reference to an exemplary embodiment.

Fig. 1

ein Blockschaltbild der prinzipiellen Ausführungsform der erfindungsgemäßen Multiband-Antenne mit separaten koaxialen Ausgängen für die einzelnen Frequenzbänder;

Fig. 2

eine Darstellung eines Blockschaltbildes analog der ersten Ausführungsform der Erfindung, jedoch mit gesplittetem Ausgang für die Frequenzbänder 1 und 3, das heißt FM und AM; und

Fig. 3

ein Blockschaltbild einer Ausführungsform mit gesplittetem Koaxialausgang für alle Frequenzbänder, das heißt FM, DAB und AM;

Fig. 4

ein beispielhaftes Frequenzfilter;

Fig. 5

ein elektrisches Symmetrierglied bestehend aus HF Transformator zur Anwendung gemäß Ausführungsbeispiel; und

Fig. 6

ein Ersatzschaltbild eines Symmetriergliedes aus diskreten kapazitiven und induktiven Bauelementen als Brückenschaltung.

Hereby show:

Fig. 1

a block diagram of the basic embodiment of the multiband antenna according to the invention with separate coaxial outputs for the individual frequency bands;

Fig. 2

a representation of a block diagram analogous to the first embodiment of the invention, but with a split output for the frequency bands 1 and 3, that is, FM and AM; and

Fig. 3

a block diagram of a split coaxial output embodiment for all frequency bands, that is FM, DAB and AM;

Fig. 4

an exemplary frequency filter;

Fig. 5

an electrical balun consisting of RF transformer for use according to the embodiment; and

Fig. 6

an equivalent circuit diagram of a balun of discrete capacitive and inductive components as a bridge circuit.

The highly integrated active multiband antenna according to the illustrations after Figure 1 to 3 consists first of a first loop-shaped conductor 1 and a second loop-shaped conductor 2, which is delimited from the first loop-shaped conductor 1. Furthermore, a stub 3 is present, which preferably runs parallel to one of the longer sides of the first loop-shaped conductor 1.

The loop-shaped conductor tracks 1 and 2 and the stub line 3 are preferably located on a planar dielectric support, for example a foil-like printed circuit board.

The first loop-shaped conductor 1, which is tuned for the frequency band 1, that is FM, has an interruption on one of its conductor track sides, which is bridged by a first adaptation circuit 5.

The opposite side of the first loop-shaped conductor track has two closely adjacent ends 6 and 7.

One of these ends is connected to the input of a first frequency filter 8 and the second of these ends 7 is connected to the input of a second frequency filter 9.

The outputs of the frequency filters 8 and 9 are connected to the balanced inputs of a first balun 10.

The unbalanced output of the first balun 10 is connected to the input of a first amplifier 11. The output 12 of the first amplifier 11 forms the output terminal of the first frequency band FM.

The second loop-shaped track 2, which is tuned for the DAB frequency band, has two closely adjacent ends 13 and 14.

A first end 13 is connected to the input of another matching circuit 15 and a second end 14 is connected to the input of the matching circuit 16.

The output of the matching circuit 15 is connected to the input of another frequency filter 17 and the output of the matching circuit 16 to the input of a frequency filter 18 in combination.

The outputs of the frequency filters 17 and 18 are connected to the balanced inputs of a second balun 19.

The unbalanced output of the second balun 19 is connected to the input of a second amplifier 20.

The output 21 of the second amplifier 20 forms the output terminal for the second frequency band, that is the DAB band.

The stub 3, which is located on the dielectric support 4, forms a monopole for the AM frequency band.

One end of the stub 3 is connected to the input of a frequency filter 22 whose output is connected to the input of a third amplifier 23 in connection.

The output 24 of the third amplifier 23 represents the connection for the AM frequency band.

In the presentation after FIG. 2 the terminals 12 and 24 for the first and the third frequency band are connected to the inputs 25 and 26 of a splitter.

The splitter has an output 27 for selectively tapping corresponding signals of said frequency bands.

The output 21 for the second frequency band is as a separate coaxial output in the embodiment according to FIG. 2 realized.

In the embodiment according to FIG. 3 is also the output 21 of the second frequency band to another input 28 of a splitter out at the output 27, the signals of the relevant frequency bands FM, AM and DAB can be tapped.

In the embodiment of the frequency filters (8; 9; 17; 18), after FIG. 4 is an inductive component L parallel to a capacitive element C and an electrical resistance R turned on. They form a parallel resonant circuit. The resonance frequency of the frequency filters 8 and 9 is in the middle region of the second frequency band DAB. The resonant frequency of the frequency filters 17 and 18 is in the middle region of the first frequency band FM. This is the maximum decoupling between the reception structures for the FM and DAB frequency bands and ensures maximum reception quality in the FM and DAB frequency bands.

$$C=\frac{1}{{\omega }_0\cdot Z_0},$$

wobei mit Z₀ die charakteristische Impedanz des Frequenzfilters (8; 9; 17; 18) bezeichnet wird. Um die bessere Anpassung des Frequenzfilters an das dahinter stehende Symmetrierglied zu gewährleisten, wird Z₀ = 50 Ohm angenommen.The inductance L and the capacitance C of the frequency filter can be determined according to the following relationships: $$L=\frac{z_0}{{\omega }_0}.$$

$$C=\frac{1}{{\omega }_0\cdot Z_0}.$$

where Z _{0 is} the characteristic impedance of the frequency filter (8; 9; 17; 18). In order to ensure better adaptation of the frequency filter to the balun behind it, Z ₀ = 50 ohms is assumed.

wird die mittlere Frequenz f₀ des entsprechenden Frequenzbandes FM bzw. DAB bezeichnet.
Die FM und DAB Frequenzbänder haben entsprechende Bandbreiten 20 MHz und 60 MHz mit mittleren Frequenzen 98 MHz und 200 MHz.
Diesen Bandbreiten entspricht der Gütefaktor Q $$Q=\frac{f_0}{f_2-f_1}=\mathrm{5...3},3,$$

With $${\omega }_0=2\cdot \pi \cdot f_0$$

the mean frequency f _{0 of} the corresponding frequency band FM or DAB is designated.
The FM and DAB frequency bands have respective bandwidths of 20 MHz and 60 MHz with mean frequencies of 98 MHz and 200 MHz.
These bandwidths correspond to the quality factor Q $$Q=\frac{f_0}{f_2-{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">f</figure-callout>}}_1}=\mathrm{5\; ...\; 3}.3.$$

F ₂ and f ₁ denote the upper and lower frequencies of the frequency band. The quality factor Q can be defined by the frequency filter parameters: $$Q=R\cdot \sqrt{\frac{C}{L}}.$$

R denotes the load resistance R of the frequency filter.
The load resistance R can be determined according to the formula (5): $$R=Q\cdot \sqrt{\frac{L}{C}}.$$

To ensure the appropriate bandwidth, the load resistor R has a resistance of 150 ohms to 300 ohms.

In the embodiment according to FIG. 5 the balun (10; 19) is implemented as an HF transformer / balun for converting a symmetrical received signal into a single-ended signal. The balun has two balanced inputs In1 and In2 and one unbalanced output Out.

FIG. 6 illustrates the preferred embodiment of the balun (10; 19) as a bridge circuit consisting of two capacitances C1, C2 and two inductors L1, L2. The balun has two balanced inputs In1 and In2 and one unbalanced output Out. Paired together first terminals of a first capacitance C1 and a first inductance L1 and a second capacitance C2 and a second inductance L2 form a first balanced input In1 and a second balanced input In2 of the balun. A second terminal of the capacitor C1 is connected to the second terminal of an inductor L2 and forms an unbalanced output Out of the balun, whose ground-connected output is formed by interconnected second terminals of the capacitance C2 and the inductance L1.

The inductances and the capacitances can be determined according to the regulations (1), (2), and (3).

Claims (14)

Active multiband antenna for terrestrial radio reception, comprising receiving structures consisting of loop and stitch-shaped conductor tracks, which are arranged on a dielectric support (4), and matching circuits, frequency filters, baluns and amplifier circuits provided in the connection areas of the receiving structures,
characterized in that
a first loop-shaped conductor track (1) is adapted to a first frequency band (FM), this first loop-shaped track (1) having an interruption which is bridged by a first adaptation circuit (5),
a first and a second frequency filter (8; 9) is provided in the connection region (6; 7) of the first loop-shaped interconnect (1), which have a high load impedance for the first loop-shaped interconnect (1) in the second frequency band (DAB) and thereby their Minimize near-field coupling to a second loop-shaped track (2), wherein the respective outputs of the first and the second frequency filter (8; 9) are connected to the balanced inputs of a first balun (10), wherein the unbalanced output of the balun (10) is present at the input of a first amplifier (11) and the output (12) of the first amplifier (11) forms the connection for the first frequency band (FM),
the second loop-shaped conductor track (2) is matched to the second frequency band (DAB), wherein in the connection region (13; 14) of the second loop-shaped track (2) a second and a third matching circuit (15; 16) is provided whose respective outputs are fed to inputs of a third and a fourth frequency filter (17; 18) which have a high load impedance for the second loop-shaped track (2) in the first frequency band (FM) and thereby minimize their near-field coupling to the first loop-shaped track (1) , wherein the respective output of the third and the fourth frequency filter (17; 18) is connected to the balanced inputs of a second balun (19), the unbalanced output of the second balun (19) is applied to the input of a second amplifier (20) and the output (21) of the second amplifier (20) the connection for the second frequency band (DAB) forms, further substantially parallel to the longer extension of the first loop-shaped conductor track (1) on a third frequency band (AM) tuned monopole stub (3) is formed, the feed end via a frequency filter (22) to the input a third amplifier (23) whose output (24) forms the connection for the third frequency band (AM), wherein the input of the frequency filter (22) in the first frequency band (FM) and second frequency band (DAB) has a high load impedance for has the monopole stub (3) and thereby minimizes their near-field coupling to the first and second loop-shaped interconnects (1; 2). Antenna according to claim 1,
characterized in that
the loop-shaped conductor tracks (1; 2) have a substantially rectangular configuration. Antenna according to claim 2,
characterized in that
the first loop-shaped conductor track (1) surrounds the second loop-shaped conductor track (2) at a distance. Antenna according to one of the preceding claims,
characterized in that
the conductor tracks (1; 2) and the stub line (3) form a planar structure. Antenna according to one of the preceding claims,
characterized in that
the dielectric carrier (4) has a layer for adhering to a particular plastic or glass surface. Antenna according to one of the preceding claims,
characterized in that
the connections for the respective frequency bands (AM, FM, DAB) are each designed as a coaxial output. Antenna according to one of claims 1 to 5,
characterized in that
the outputs for the frequency bands (AM, FM, DAB) are completely split or split for at least two frequency bands. Antenna according to one of the preceding claims,
characterized in that
the length of the loop-shaped conductor tracks is ≤ 0.2 times the smallest wavelength of the respective desired reception range. Antenna according to one of the preceding claims,
characterized in that
substantially all antenna components are disposed on a dielectric foil wiring substrate. Antenna according to one or more of the preceding claims, characterized by
their use in motor vehicles, in particular passenger cars and commercial vehicles. Antenna according to one or more of the preceding claims, characterized in that
the interruption of the first loop-shaped conductor track (1) is arranged away from the connection area (6; 7). Antenna according to one or more of the preceding claims, characterized in that
the matching circuits (5; 15; 16) comprise capacitors. Antenna according to claim 12,
characterized in that
the matching circuits (5; 15; 16) are formed as planar capacitors on a common wiring substrate with other antenna components. Antenna according to one or more of the preceding claims, characterized in that
the frequency filters (8; 9; 17; 18) are in the form of a parallel resonant circuit with an inductance, an electrical resistance and a capacitance, the resonant frequency of the frequency filters (8; 9) being at the middle frequencies of the second frequency band (DAB) and the resonant frequency of the frequency band Frequency filters (17; 18) on the middle frequencies of the first frequency band (FM), wherein the resistance value is 150 ohms to 300 ohms.

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