FR2721756A1 - An omnidirectional transmit-receive antenna system with angular diversity and polarization. - Google Patents

Abstract

The invention relates to an omnidirectional transmit-receive antenna system. It comprises a first (1) unidirectional radio antenna in a first direction defined by two orthogonal planes, one of the planes defining a first plane (C) and a second unidirectional radio antenna (2) in a second direction defined by two orthogonal planes , one of the planes defining a second plane (B). The first (1) and the second antenna (2) are placed so that the first and the second plane being orthogonal and the first and the second direction being orthogonal, we thus obtain an omnidirectional radiation pattern formed by a bidirectional radiation pattern in a third plane (A), which, orthogonal to the first and second plane, is formed by a main plane of the first and of the second antenna and by a unidirectional radiation pattern in the first and in the second plane. A coupling circuit (3) makes it possible to ensure in reception a switching on one or the other of the first or second antenna as a function of the relative level of signal received. Application to transmitter devices, or transmitter-receivers, for example.

Description

OMNIDIRECTIONAL TRANSMIT-RECEPTION ANTENNA SYSTEM

  A ANGULAR DIVERSITY AND POLARIZATION

  The invention relates to an antenna system for transmitting

  angular diversity and polarization omnidirectional reception-reception, usable on transceivers or

  simple portable receivers used in paging.

  In paging systems, such as the

  R.D.S. system for "Radio Data System" in English

  Saxon, digital data management or use of this network are broadcast on the wave carrier of a signal of

  frequency modulation broadcasting of band II.

  The data disseminated can be very diverse in nature and is usually broadcast as messages

intended for subscribers.

  Today, paging is a means of communication that is widely used by a category of users who are often called upon to

  various means of locomotion, in geographical

very varied.

  In general, the receiver or transmitter / receiver

  tor, is intended to be worn by its user, either inside a jacket pocket or for example hung

at his belt.

  The user ignores and is not at all concerned about whether the receiver, or the transceiver, is correctly oriented vis-à-vis the transmitter that broadcasts the messages. Indeed, the receivers or transceivers are very compact and normally equipped with an antenna

  which determines their dimensional characteristics.

  the. This antenna, sensitive in general to the magnetic component of the electromagnetic wave carrier, component H, is most often constituted by a metal frame

  very selective and optimized in gain, which gives the year

  thus formed a radiation pattern of the type

  unidirectional, having a good directivity.

  In order for the reception and, where appropriate, the

  If it is efficient, it is necessary that the orientation of this type of conventional antenna be performed as a function of the polarization of the carrier wave. The polarization of the waves

  issued by the facilities of the broadcasters, or radiotele

  lephonia, is in general either horizontal or vertical,

  very rarely circular or oblique.

  In the case where such a conventional antenna is not oriented accordingly, it can not allow to receive the polarized carrier wave as mentioned above,

  which leads to a detected signal loss not neglected

  ble, of the order of 20dB to 35dB when the orientation of the antenna is in quadrature with respect to the preferred axis

polarization of the field.

  In addition, this type of antenna does not have, in

  because of its unidirectional radiation pattern

  nel, an ability to receive, or transmit, radio signals in all azimuthal directions, this

  which normally also requires the user to

  receiver, or transceiver, in the horizontal plane. At best, this type of antenna, as shown in FIG. 1 for a metal frame antenna, with or without a ferrite core, presents a unidirectional radiation pattern in two orthogonal planes, the antennas then being placed that one of the planes is the horizontal plane, the other plane, vertical, in front of

  correspond to the plane of polarization of the electromagnetic wave

  spread, which of course implies two orienta-

for optimal reception.

  The object of the present invention is to remedy the aforementioned drawbacks by implementing an angular diversity and polarization omnidirectional transmission-reception antenna system for which the contingencies relating to the orientation of the antenna system for a

  reception, or transmission-reception, optimal, are

deleted.

  Another object of the present invention is, in particular, the implementation of a transmission-reception antenna system having a radiation pattern

  substantially omnidirectional in a plane, the horizontal plane

  tal. Another object of the present invention is, in

  In addition, the implementation of a transmission antenna system

  reception having a unidirectional radiation pattern

  two other plans, the three plans being

orthogonal each to each.

  The omnidirectional transceiver antenna system

  recessive angular diversity and polarization, object of the present invention, is remarkable in that it

  includes a first unidirectional radio antenna

  in a first direction defined by two orthogonal planes, forming principal planes of this antenna, one of the planes defining a first plane, and a second unidirectional radio antenna with respect to a second direction defined by two orthogonal planes, forming principal planes of this antenna, one of the plans defining a second plane. The first and second antennas are positioned so that the first and second planes are orthogonal, the first and second directions are orthogonal. The antenna system thus formed has a bidirectional radiation pattern in a third plane, orthogonal to the first and second plane and formed by a main plane of the first and second antenna respectively, and by a unidirectional radiation pattern in the first and second respectively. plan. A coupling circuit makes it possible to receive, on reception, an output switching of the antenna system on one or the other of the first or second antenna, as a function of the relative level of the radio signal received at the output of the antenna.

each antenna.

  The antenna system, object of the present invention

  is applied to paging and, more generally, to radiocommunication or mobile radiotelephony.

  It will be better understood by reading the description

  and to the observation of the drawings in which, in addition to FIG. 1 relating to the prior art, FIGS. 2a, 2b, 2c, 2d, 2e and 2f represent

  different antenna radiation patterns

  of the antenna system and the antenna system, object of the present invention, - Figures 3a and 3b show a practical embodiment of the antenna system, object of the present invention,

  FIGS. 4a, 4b and 4c represent the diagrams

  three of the orthogonal planes of the antenna system, object of the invention, as shown in FIGS. 3a, 3b; FIG. 5 represents a block diagram of the coupling circuit of the antenna system, object of the present invention; invention,

  FIG. 6 represents a chronogram of the control

  sequence of the switching on reception between the

first and second antenna.

  A more detailed description of an antenna system

  omnidirectional transmission and reception systems with angular diversity and polarization, in accordance with the subject of the present invention, will now be given in connection with

Figures 2a to 2e and 2f.

  In accordance with the above figures, it is indicated that the antenna system, object of the present invention, has a first radio antenna, denoted 1, unidirectional in a first direction, this direction, denoted OX in Figure 2a, being defined by two planes orthogonal, plans OX, OZ respectively OX, OY. The above-mentioned planes form the main planes of this antenna 1, one of the planes, the plane OX, OZ defining a first plane,

noted C in Figure 2a.

  The antenna system, object of the present invention

  also includes a second radioelectric antenna

  that unidirectional, denoted 2, in a second direction, the direction OY in Figure 2b, this direction being defined by two orthogonal planes, OX, OY, respectively OY, OZ. These two planes form principal planes of the antenna 2, one of the planes, the plane OY, OZ defining a second plane, denoted B in FIG. 2b. The first 1 and the second antenna 2 are placed in the vicinity of each other.

  way that the first C and the second plane B being orthogonal

  the first and second OX directions, respectively

  OY are also orthogonal. This allows to obtain

  for the antenna system 1,2 a radiation pattern

  substantially omnidirectional, formed by a bidirectional radiation pattern in a third plane A, as shown in Figure 2c. The plane A is orthogonal to the first and second planes and is formed by a main plane of the first respectively of the second antenna 1,2. The substantially omnidirectional radiation pattern of the antenna system thus formed also includes a unidirectional radiation pattern in the first C respectively in the second B plane, and

  as shown in Figures 2e and 2d.

  Finally, as shown in FIG. 2f, a coupling circuit 3 makes it possible to provide, in reception, an output switching of the antenna system on one or the other of the first or second antenna 1,2, depending on the level relative radio signal received at the output of each antenna. It will of course be understood that the antenna system, which is the subject of the present invention, can be used both at reception and at transmission, because of the dual nature of the radiation pattern in reception, or in transmission, respectively. radiation being, in accordance with the classical theory of antennas, identical to the emission

and at the reception.

  Of course, in the context of a reception device

  paging function, the transmission function is not

  necessary, which can then be deleted.

  A more detailed description of an antenna system

  of omnidirectional angular diversity and polarization

  The object of the present invention will now be given with reference to FIGS. 3a and 3b in the nonlimiting context of an application to paging by

example.

  As shown in FIG. 3a, the first antenna 1 is a metal frame antenna surrounding the actual body of the receiver R and the second antenna 2 is a ferrite core frame antenna. The metal frame antenna 1 for example surrounds the receiver circuits R, as shown in FIG. 3a, and is housed in the housing, not shown, of the receiving apparatus, which of course comprises a

  P battery power supply.

  The second antenna 2 also comprises a metal frame 20 which is further associated with a ferrite core 21. The second ferrite core antenna is placed in the vicinity of one of the sides of the metal frame

  constituent of the first antenna 1 for example.

  The configuration thus produced makes it possible, of course, for a given position of the receiver in space, to receive in all the azimuth positions, that is to say for any orientation of the receiver in the plane A, a

  signal level due to the orthogonal difference

  Polar radiation patterns relating to

  each of the antennas, as shown in Figure 2c.

  In FIG. 3b, there is shown, for the mode of

  embodiment of FIG. 3a, the orthogonal induction fluxes

  nals received by the first 1 and the second antenna 2 in the directions OX and OY. It is thus understood that, in the representation of FIG. 3b, the plane B is the plane of the sheet containing FIG. 3b, the plane A is a horizontal plane orthogonal to the plane of the sheet containing FIG. 3b and the plane C is a vertical plane orthogonal to the plane of the sheet containing Figure 3b. The reference OXYZ, respectively O'X'Y'Z 'corresponds to the oxyz mark of

  Figures 2a to 2e. In FIGS. 4a, 4b and 4c, there is shown

  felt the polar patterns of respective radiation received by the first and the second antenna in the directions

OX and OY.

  It is thus understood that the antenna system, object of the present invention, offers the possibility of a quasi-omnidirectional reception in the horizontal plane A thanks to the coupling circuit 3, which allows, thanks to an electronic control system which will be described below with reference to FIG. 5, to switch on the choice of one or the other constituting antenna of the system

antennas according to the invention.

  In general, as shown in FIG. 5, it is indicated that the coupling circuit 3 may advantageously comprise a switch 35 formed by at least one dual-channel switch, denoted 351, this dual-channel switch comprising a first channel of FIG. an input connected to the first antenna 1 and a second input channel connected to the second antenna 2. It is indicated that the first and the second antenna 1, 2 are connected to the aforementioned input channels and each have matching capabilities, noted Cal, Ca2. The output of the dual-channel switch 351 in fact comprises a first and a second output channel, the first output channel, in the case where the antenna system, which is the subject of the present invention, is designed for a paging-type receiver, being directly connected to a reception channel, designated RECEIVER, of conventional type. The reception chain, or

  receiver, usually comprises a radiofrequency

  a radio frequency filter, a mixer circuit powered by a local oscillator and an intermediate frequency filter, itself followed by an intermediate frequency amplifier and an intermediate frequency demodulator device. The second output channel of the dual-channel switch 351 can then be directly connected to the

  reference voltage or mass voltage of the device.

  In addition, the coupling circuit 3 comprises a control channel of the dual-channel switch 351 as a function of the signal level delivered by the output of the

antenna system.

  In a non-limiting embodiment, as shown in FIG. 5, the control chain advantageously comprises a field level detector 31 whose input is directly connected to the intermediate frequency amplifier of the receiver, this detector delivering a signal of rated level U0, and a threshold comparator circuit 32 receiving the level signal U0 and a value of

determined threshold, denoted U1.

  A flip-flop circuit 33 is furthermore provided in the above-mentioned control chain, this flip-flop receiving the signal delivered by the comparator 32 on comparison of the level signal with the threshold signal U1. An output Q of the flip-flop type circuit 33 allows to directly control the dual-channel switch 351 of the switch 35 according to an error criterion, which

  will be explained later in the description.

  Finally, it is indicated that the above-mentioned control chain also comprises a logic circuit 34 whose inputs are connected to the Q outputs and the complemented Q output of the flip-flop circuit 33 and whose output is connected to a microprocessor 36, which allows a reset to zero. RESET input of the flip-flop circuit 33. The logic circuit 34 comprises, for example, two parallel channels each comprising a delay circuit 341, 342 and an AND type logic circuit 343, 344. An input of each AND-type logic circuit is connected to the FIG. supplemented output Q and

  at the Q output via the timing circuit

  341, respectively at the Q output and at the output

  complemented Q through the timing circuit

  The output of the logic circuits ET 343 and 344 is connected to an OR logic circuit 345, which delivers a field presence signal.

low Uf to the microprocessor 36.

  The operating mode of the control chain previously described in connection with FIG. 5 will be described in

  connection with Figure 6, which represents a chrono-

  gram showing the sequential sequence of the control of the antenna system, object of the present invention, such as

  as described in connection with FIG.

  A detection of the instantaneous radio-frequency field level received at the instant To on the antenna 2 switched by default, the metal-framed antenna with ferrite core, is first performed, this detection being carried out by

  the field level detector 31 at the output of the amplifier

intermediate frequency.

  A comparison of this level received at the instant To is performed with the threshold level U1 by the comparator

  32, this threshold level U1 defining the switching threshold

tion.

  - If U0 <U1, then the comparator circuit 32 triggers the flip-flop 33, which controls the activation of the metal frame antenna 1 by switching control

of the dual-channel switch 351.

  - Activation of the time constant x introduced

  The output of the delay circuit 341 is at the same time performed.

  - If U0 <U1 for the duration defined by the constant

  With the above-mentioned time, then, the device generates error information via the OR gate 345, confirming the presence of a weak field, signal Uf, on the

  first and on the second antenna.

  It is of course understood that from the point of view of the operating mode of the control chain represented in FIG. 5, that the field level detector 31 supplies an instantaneous voltage U 0 that is proportional to the level of electromagnetic field HF captured by the second antenna 2 activated.

by default.

  The comparator circuit 32 receives the level signal U0 corresponding to the electromagnetic field received at the instant To, and the reference voltage U1 corresponding to the threshold of

  switching. The value of the switching threshold is determined

  based on the minimum signal-to-noise ratio for which the bit error rate on the R.D.S. by

example is still acceptable.

  The comparator 32 outputs a logic state, which controls the flip-flop circuit 33 according to the following relationships: U0 (T0) <U1 ---> comparator output = 1

  U0 (T0)> U1 ---> comparator output = 0.

  The toggle circuit 33 thus receives the control information from the comparator 32 and in turn activates the first metal frame antenna 1 while the

  second ferrite core antenna 2 is inhibited.

  In the logic circuit 34, it is in fact understood that it makes it possible to generate, from the switching information, the aforementioned time constant T which makes it possible to define the error criterion previously mentioned in FIG.

  description. If in the time interval x mentioned above

  second antenna 2 with ferrite core is again activated, then the output logic circuit OR 345 generates for the microprocessor 36 a so-called low field information Uf, indicating in fact that the level of the received field is

  less than the minimum threshold defined by the threshold value U1.

  The microprocessor 36 makes it possible to ensure the reset of

  the flip-flop 33 by the RESET command.

  The previous description of the antenna system

  omnidirectional angular diversity and polarization, object of the present invention, concerned the case of a

  paging receiver type R.D.S. for example.

  Of course, the antenna system, which is the subject of the present invention, may, where appropriate, be used as an omnidirectional transmit / receive antenna system.

  example in the field of application of the radiotelephone.

  In this case, as also shown in the figure, the dual-channel switch 351 may be associated with another dual-path switch, noted 352. The switch 352 actually comprises a first and a second switch. A channel of the first and second switches is connected for example to a transmitter circuit, denoted EMITTER, while the other channel of the first switch is connected to the terminal

  the receiver and in particular the radiofrequency

  quence of it. The other path of the second switch is connected for example to the ground or reference voltage of the device. The switched channels of the first and second switches are respectively connected to the first output channel and the second output channel of the first switch 351. Thus, the second dual channel switch 352 has two switching positions, denoted I respectively II. Switching of the two switches of the second dual-channel switch 352 is carried out via the microprocessor 36 for example, which conventionally allows the switching to the receiving position according to the position I, the connection of the first double switch. track 351 being then brought back to

  that previously described in the description in the case

  of the R.D.S. or on the contrary in position II, position in which the first 1 and the second antenna 2 are supplied in parallel by the transmitter circuit. Of course, it is indicated that the switching of the receiving position I to the transmission position II and vice versa, is controlled via the microprocessor 36 in a conventional manner, in accordance with the control process of the known transceiver devices. As such, this switching will not be described in more detail. It is also understood that in order, if necessary, to take into account the disparities in yield or radiation pattern of the first and second transmit antennas, devices, not shown in FIG. to balance the emission levels of the

  first respectively of the second antenna.

  An antenna transmission system has been described.

  omnidirectional reception with particularly good angular diversity and polarization. In particular,

  in the case of use in a radio

  messaging, for example, it constantly provides an omnidirectional reception of messages transmitted by systems such as the R.D.S. system. by

example.

Claims (5)

  1. Omnidirectional transceiver antenna system   recessive angular diversity and polarization, characterized in that it comprises: - a first unidirectional radio antenna in a first direction defined by two orthogonal planes, forming principal planes of this antenna and one of the planes defining a first plane (C),   - a second unidirectional radio antenna   in a second direction, defined by two orthogonal planes, forming principal planes of this antenna and one of the planes defining a second plane (B), the first and the second antenna being placed so that the first and second planes being orthogonal, the first and second directions are orthogonal, thereby obtaining for said antenna system a substantially omnidirectional radiation pattern formed by a bidirectional radiation pattern in a third plane (A), orthogonal to the first and second plane and formed by a main plane of the first respectively second antenna, and a unidirectional radiation pattern in the first (C) respectively the second (B) plane, - coupling means for ensuring, in reception, a switching output of the antenna system to either of the first or second antennas as a function of the relative radio signal level r received in output of each antenna.   Antenna system according to claim 1, characterized in that the first antenna is a metal frame antenna and the second antenna is a ferrite core frame antenna, the ferrite core antenna being placed in the vicinity of the antenna. one of the sides of the frame forming the antenna to metal frame.   Antenna system according to one of the claims   preceding, characterized in that said coupling means comprise a dual-channel switch, a first input channel being connected to the first antenna and a second input channel being connected to the second   antenna, the output of said dual-channel switch,   killing output of said antenna system, being intended to be connected, in reception, to the radio frequency input of a receiver. 4. Antenna system according to claim 3, characterized in that it further comprises means for controlling said coupling means as a function of the level of the   signal delivered by the output of said antenna system.   Antenna system according to claim 4, characterized in that said coupling means comprise at least:   - a radio-frequency field level detector circuit   relay, providing a level signal, - a threshold comparator circuit receiving said level signal and outputting a comparison signal, a bistable flip-type circuit receiving said comparison signal, an output of said flip-flop circuit directly controlling means of   coupling according to an error criterion.