WO2011161711A1

WO2011161711A1 - Omnidirectional-antenna apparatus for receiving digital terrestrial television

Info

Publication number: WO2011161711A1
Application number: PCT/IT2011/000213
Authority: WO
Inventors: Albino Benedettini
Original assignee: Sound Light & Technologies Srl
Priority date: 2010-06-22
Filing date: 2011-06-22
Publication date: 2011-12-29
Also published as: ITRM20100339A1

Abstract

An omnidirectional-antenna apparatus for receiving digital terrestrial television, comprising a closed-dipole omnidirectional antenna (1) enclosed within a protective casing (5) resistant to atmospheric agents.

Description

OMNIDIRECTIONAL-ANTENNA APPARATUS FOR RECEIVING DIGITAL

TERRESTRIAL TELEVISION

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Technical sector

The present invention relates to an antenna for digital terrestrial television receiver systems.

In greater detail, the invention regards an antenna for use in mobile environments that are exposed to meteorological conditions, for example on board atercraft .

State of the art

Known systems for receiving the digital terrestrial television signal comprise antennas connected to a decoder that processes the video signal.

Antennas of a known type have an optimal direction of reception and can be oriented for "tracking" the best position.

The greater the departure from the optimal position or orientation, the worse the quality of the signal received up to loss of the minimum level of quality in reception needed to obtain a reproducible signal .

Moreover known are antennas of an

"omnidirectional" type based upon a complex technology of tuning with respect to the various possible directions of the signal to be received.

The need for an effective and reliable solution is particularly felt for installation of digital terrestrial television receiver systems in mobile environments, which are characterized by their very nature by an absolute variability of the orientation of the antenna · support and are normally exposed to the action of atmospheric agents, for example in the marine environment, pleasure boats, ships, etc.

Purpose of the invention

Consequently, a first purpose of the present invention is to provide a receiving antenna that will solve the drawbacks of apparatuses of a known type.

Summary of the invention

For the above purpose, an apparatus according to at least one of the annexed claims has been developed.

The advantages obtained basically consist in the fact that the apparatus can be installed outside on board watercraft and substantially maintain the capacity of receiving and sending a signal of good quality to a television system irrespective of the movements of the watercraft and the atmospheric conditions .

List of the drawings

The above and further advantages will be better understood by any person skilled in the branch from the ensuing description and from the annexed drawings, which are provided purely by way of non-limiting example and in which:

- Figures 1A and IB show, respectively, a diagram of an antenna and of an apparatus according to the invention;

- Figures 2A and 2B show orthogonal side views of the antenna;

- Figure 3 shows a general radiation diagram of a dipole antenna;

- Figure 4 shows the radiation diagram of an antenna according to the invention.

Detailed description of the invention

With reference to the attached drawings, an apparatus for receiving the digital terrestrial television signal is described, comprising an omnidirectional antenna 1 provided with a fixing support 4 and connected to a decoder 2.

Preferably, the antenna 1 is made up of at least two directional antennas 6, 7 oriented in a way staggered with respect to one another.

In the example described, the antennas 6, 7 are passive antennas with an operating frequency of between 200 MHz and 860 MHz and a gain of 6 dB, staggered by 90° and supported by a common mast 8 emerging from the support 4. In this way, a substantially omnidirectional antenna is obtained that receives the bands 3a, 4a and 5a of the digital terrestrial television.

For this purpose, said receiving antennas 6, 7 are basically formed by closed dipoles, preferably having a length of approximately 19 cm and a width of approximately 3 cm.

The antennas 6, 7 connected to the decoder 2 via communication means 3 of the wired or wireless type, and the decoder 2 is provided with means for selecting a preferred signal from among the signals coming from the antennas 6, 7.

In this connection, it should be noted that, according to the invention, it is envisaged that the signals of the two antennas 6, 7 are combined, by means of a normal mixer or signal adder before being sent on to a standard decoder 2. Alternatively, the decoder 2 can be of the two-input type (known commercially), and in this case the signals of the two antennas are sent thereto separately.

According to the invention, the antenna, 1 is enclosed inside a protective casing 5 resistant to atmospheric agents, constituted preferably by a shell made of glass-reinforced plastic sealed from the .external environment.

In use, the support 4 is fixed to an application surface, for example an external support of a watercraft, and the two antennas 6 and 7 are connected to the decoder 2, which is in turn connected to a television system (not illustrated in the figure) .

Thanks to the invention, the movements undergone by the watercraft both during navigation and when moored (roll, pitch) do not affect in a determining way the capacity of the omnidirectional antenna to receive a quality signal that can be selected by the decoder.

At the same time, thanks to the protective casing the antenna is sheltered from atmospheric agents and is able in any circumstance to receive and send the television signal to the decoder.

Advantageously, the apparatus of the invention moreover enables reception also of the analog television signal on board a watercraft.

Finally, in the example of embodiment illustrated, the antennas 6 and 7, set at 90° with respect to one another and set on top of one another by means of fixing to one and the same vertical mast 8, are constituted by two dipoles in air (which are closed dipoles) and are set at a vertical distance of 15 cm from one another, and are made of aluminium with balun so as to present an output impedance of 75 Ω.

In conclusion, it should be noted that from the tests conducted it has emerged .how the antenna 1 according to the present invention is specific for DVBT. This is proven by the BER (bit-error rate) values and MER (modulation-error rate) detected, which, if compared to a log-periodic antenna at a height of 5 m and with the gain of the reference antenna of +6 dB, yield the values appearing in the table below.

The spectrum of signals received with the antenna according to the invention displayed using a spectrum analyser highlights how the diversity system manages to maintain the signal squared also when moving, something that is impossible for all other antennas currently known .

The invention has been described with reference to a preferred embodiment, but it is understood that equivalent elements may be used, without thereby departing from the sphere of protection granted.

Claims

1. An omnidirectional-antenna apparatus for receiving digital terrestrial television, characterized in that it comprises a closed-dipole omnidirectional receiving antenna (1), provided with a fixing support (4) and connected to a decoder (2), as well as a protective casing (5) resistant to atmospheric agents designed to enclose within it said receiving antenna (1) ·

2. The apparatus according to Claim 1, wherein ' said antenna (1) comprises at least two directional receiving antennas (6, 7), each of which is constituted by a closed dipole and which are oriented in a way staggered with respect to one another; the signals of the two antennas (6, 7) being sent to said decoder (2) directly, in the case where the decoder is provided with two inputs, or else via interposition of a signal mixer or adder of a known type.

3. The apparatus according to Claim 2, wherein said antennas (6, 7) are two directional antennas oriented substantially at 90° with respect to one another and supported by a substantially vertical common mast ( 8 ) .

4. The apparatus according to Claim 2 or Claim 3, wherein each antenna (6, 7) is constituted by a closed dipole having a length of approximately 19 cm and a width of approximately 3 cm, which are installed on top of one another at a distance apart of approximately 15 cm.

5. The apparatus according to any one of the preceding claims, wherein said protective casing (5) is a shell made of glass-reinforced plastic sealed with respect to the external environment.

6. The apparatus according to Claim 4, wherein said antennas (6, 7) are passive antennas with an operating frequency of between 200 MHz and 860 MHz.

7. The apparatus according to any one of the preceding claims, wherein said antennas (6, 7) are passive antennas with a gain of 6 dB.

8. The apparatus according to any one of the preceding claims, comprising means for fixing said support (4) to an outer portion of a watercraft.