AU683933B2

AU683933B2 - A repeater for a mobile radio system

Info

Publication number: AU683933B2
Application number: AU77486/94A
Authority: AU
Inventors: Manfred Bohm
Original assignee: Alcatel NV
Current assignee: Alcatel Lucent NV
Priority date: 1993-10-30
Filing date: 1994-10-26
Publication date: 1997-11-27
Anticipated expiration: 2014-10-26
Also published as: FI945088A; EP0651524A2; AU7748694A; FI945088A0; DE4337244A1; NZ264804A; EP0651524A3

Description

P/001011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990 0**

C..

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "A REPEATER FOR A MOBILE RADIO SYSTEM" The following statement is a full description of this invention, including the best method of performing it known to us:- C. 9 C 5 The present invention relates to a mobile-radio system with at least one mobile station, at least one base station, and at least one repeater.

Such mobile-radio systems are known, for example, from EP-B1 0 261 127. That patent specification discloses a mobile-radio system which consists of two mobile stations (a portable station and a station installed in a vehicle), a base station, and a repeater.

There, effective utilisation of the spectrum of radio-frequency transmission channels is to be achieved in a time division multiple access (TDMA) radio system which distributes channels to at least two time slots.

Signal transmission from the base station to the mobile stations (downlink) and in the opposite direction (upiink) takes place via the repeater.

Repeaters in mobile-radio systems generally serve to amplify incoming signals and retransmit the amplified signals.

The repeater used in the above-mentioned mobile-radio system is oooo designed for bidirectional transmission, for transmission in the downlink and uplink directions. It receives signals at a first frequency and retransmits the signals either at the first frequency or at a second frequency. This repeater includes a controller, a clock generator, a duplexer, and a memory to ensure transmission and reception in different time slots.

from Through the transmission and reception in different time slots, feedback from the transmitter to the receiver is avoided. Such feedback occurs mainly if the transmitted signal has the same frequency as the received signal.

This mobile-radio system is expensive. The repeater used therein is very complicated and costly because of its bidirectional transmission capability and since transmission and reception take place in different time slots.

It is desirable to provide a simpler mobile-radio system in which mobile stations, particularly portable units, with low transmitting power can be used, so that, among other things, possible health hazards are reduced and a longer conversation time is possible with unchanged battery output. This specification discloses a mobile-radio system with at least one base station and at least one mobile station, wherein it has at least one repeater which is involved in the transmission of signals in a single direction only, namely from the mobile station

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to the base station.

It is also desirable to provide a simple repeater for such a mobile-radio system. This specification also discloses a repeater for a mobile-radio system as claimed in claim 1, including an amplifier which amplifies the signals to be transmitted without changing characteristic parameters of the signals.

Further advantageous features of the invention are defined in the subclaims.

The invention is advantageous in that feedback from the transmitter to the receiver is avoided by a simple antenna unit, not by a frequeilcy conversion of the signal to be transmitted or by the fact that transmission and reception take place in different time slots.

The invention will now be explained in more detail with reference to the accompanying drawings, in which; SFigure 1 shows a simple mobile-radio system with a base station, a repeater, and a mobile station; Figure 2 shows an embodiment of a repeater, and Figure 3 shows a schematic vertical antenna pattern of the repeater, Figure 1 shows a cell of a cellular mobile-radio system which contains a S base station BTS, a repeater R according to the invention, and a mobile station 2 MS. A radio signal from the mobile station MS is transmitted to the base 9**9 station BTS with the aid of the repeater R. By contrast, a radio signal from the base station BTS is transmitted to the mobile station MS direct. The directions of transmnission are indicated by arrows.

Thus the novel mobile-radio system is a system in which the repeater R is involved in the transmission of signals in only one direction, namely from the mobile station MS to the base station BTS (uplink).

Figure 2 shows one embodiment of a repeater R. The repeater has a transmitting antenna 1 in the form of a vertical monopole which is mounted on a horizontal, electrically conducting plane 4, Below the plane 4, it has a receiving antenna 2 in the form of a pylon antenna which extends in the longitudinal direction of the monopole 1. The transmitting antenna 1, the receiving antenna 2, and the plane 4 form an antenna unit. The repeater further 4 includes a broadband amplifier 3, which is located here below the plane 4, and energy supply means (not shown). Exemplary transmit and receive directions are indicate, The antenna 1 and 2 of the repeater R have vertical radiation patterns as shown in Figure 3. The radiation pattern of the monopole 1 is denoted by S1, and that of the pylon antenna 2 by E2. The two radiation patterns are circularly symmetrical with respect to a vertical axis Y. It can be seen that the radiation pattern S1 of the monopole 1 is raised with respect to a horizontal axis X, while the pattern E2 of the pylon antenna 2 is lowered with respect to the horizontal axis X. This means that radio signals are received from a mobile station MS in an angular range determined by the pattern E2, and transmitted to the base station BTS in an angular range determined by the pattern S1.

Instead of the monopole 1 with the circularly symmetrical pattern Si, a S monopole-Yagi-antenna combination can be used to concentrate the radio signals in the direction of the base station. This antenna combination consists of a monopole and a Yagi antenna and makes it possible to reduce the transmitting power of the transmitting antenna 1.

The raising and lowering of the antenna patterns is effected by the electrically conducting plane 4, which has a diameter D equal to, at least five times the wavelength A of the radio signal, D 5 A. Primarily, or however, the conducting plane serves to provide electromagnetic decoupling between transmitting antenna and receiving antenna. This means that the antenna unit is designed to prevent electromagnetic interference between the 99 S two antennas 1, 2. Electromagnetic decoupling is provided here by a special design of the antenna unit, not by frequency conversion of the signal to be transmitted, for example. Since the repeater R transmits and receives on the same frequency, sufficient decoupling must be provided to prevent signals transmitted by the repeater R from being received by the receiving antenna of the same repeater. The likewise circularly symmetrical radiation pattern E2 is determined by the geometric parameters of the pylon antenna 2. Parameters are, for example, the cylinder diameter D and the number of slots, According to Heilmann, "Antennen", Bibliographisches Institut, Mannheim, Wien, Zurich,

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1970, pages 119 to 148, the horizontal radiation pattern is nearly circular if the diameter D is less than A/8. The receiving antenna 2 may also consist of a multislot pylon antenna. To prevent any shadow loss caused by a thick cylinder, 3 to 4 slots, for example, may be spaced by 90' around the circumference of the cylinder.

The receiving antenna may also be a dipole array with a reflector.

The broadband amplifier 3 is, for example, a transparency amplifier, whose gain in the frequency range considered is independent of the frequency f; the frequency fi, of the signal to be amplified is equal to the frequency of the amplified signal; fin fout.

The only function of this amplifier is to amplify the signals to be transmitted, without changing the characteristic parameters of the signals.

Such characteristic parameters are, inter alia, the frequency, the type of modulation, and the occupied time slots. There is no demodulation of the received signals, no transformation into the baseband, no charge of occupied time slots, and no frequency conversion. Transmission and reception thus take place in the same time slot.

The repeater R must be located in the radio cell so that its receiving antenna can receive the signals from the subscriber, who is usually at ground level; it must be mounted in an elevated place, eg., on roofs or masts.

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Claims

1. A mobile-radio system with at least one base station and at least one mobile station, wherein it has at least one repeater which is involved in the transmission of signals in a single direction only, namely from the mobile station to the base station.

2. A repeater for a mobile-radio system as claimed in claim 1, including an amplifier which amplifies the signals to be transmitted without changing characteristic parameters of the signals.

3. A repeater as claimed in claim 2, including an antenna unit consisting of a transmitting antenna and a receiving antenna and designed to prevent electromagnetic interference between the transmitting antenna and the receiving antenna.

4. A repeater as claimed in claim 3, wherein the transmitting antenna is disposed above a horizontal, electrically conducting plane and the receiving i" 15 antenna is disposed below said plane, which substantially prevents interference between the two antennas.

5. A repeater as claimed in claim 4, wherein the transmitting antenna has a raised radiation pattern with respect to the plane, and the receiving antenna a lowered radiation pattern with respect to the plane. 2(C

6. A repeater as claimed in claim 5, wherein the transmitting antenna is a monopole and the receiving antenna a dipole pylon antenna.

7. A repeater as claimed in claim 5, wherein the transmitting antenna is a 0 oo monopole-Yagi-antenna combination and the receiving antenna a dipole pylon antenna.

8. A repeater as claimed in claim 4, wherein the plane has diameter equal to at least five times the signal wavelength A. I 7

9. A repeater substantially as herein described with reference to the accompa 3 drawings. A mobile radio system substantially as herein described with reference to the accompanying drawings. DATED THIS NINETEENTH DAY OF OCTOBER 1994 ALCATEL N.V *o 9 9 9** 9 *o 99 *o **l f• I_ r- ABSTRACT In mobile-radio systems, repeaters are used to ensure communication over long distances with mobile radio-telephones which have low transmitting power. Low transmitting power is desired in order to reduce, among other things, possible health hazards. The repeater used in the mobile-radio system has a transmitting antenna whose radiation pattern (S1) is raised with respect to a horizontal conducting plane and a receiving antenna whose radiation pattern (E2) is lowered with respect to the plane Transmission and reception take place on the same frequency and without a time-slot change. (Figure 2) o o* «*09 **t 0o 0 0 @0 -C