EP1055931A2 - Circuit for testing the operation of at least one antenna - Google Patents

Abstract

A by-pass impedance (Z) forms a shunt circuit between the aerial (14) and ground (oo). A dc test supply (Us) injects a curre (Ic) into the by-pass circuit formed by aerial and by-pass impedance. A comparator (COM) compares the resultant test voltage (Uc with a reference voltage (UREF) to determine whether or not the aerial is serviceable

Description

The invention relates to a circuit arrangement for checking the operational readiness an antenna, especially in a vehicle telephone, which has several Has antennas. The invention enables the vehicle telephone to make errors at any time the antenna cable, unmounted, incorrectly installed, or failed vehicle antennas, for example as a result of damage in a traffic accident recognize and automatically switch to a functional antenna.

Since the functionality of a radio telephone is only given when all Components of the communication system work and the antennas because of their Location are often particularly sensitive mechanically, increases the solution according to the Invention in an emergency significantly increases the reliability of a radio telephone.

Vehicle phones are usually equipped with an outside or window antenna equipped, their local location primarily according to the requirements of an optimal Receive and transmit quality is selected.

However, it is disadvantageous that when selecting such a position the It is likely that in the event of an accident with the vehicle or a other external force, the antenna is damaged until mm total failure. In the case of an external antenna in particular, for example, the force also occurs a malicious destruction by strangers or breaking when driving through low Obstacles. A total failure of the antenna can result from a traffic accident or Vehicle damage has fatal consequences, since the establishment of a telephone connection does not is more possible to call for help.

In order to remedy this defect, mm is an example from the publication EP 0 859 237-A1 known to install an emergency or alternative antenna at another installation location. This takes over after a functional failure of the one used as the main antenna External antenna for transmission / reception. Both antennas are each separate Coaxial cable connected to the radio telephone.

To achieve maximum transmission quality and avoid Interference in communication is that during the function of the main antenna Emergency antenna out of order. That means the automatic commissioning of the emergency antenna and the corresponding line is only carried out during an emergency manual or automatic establishment of an emergency call. For this, either The emergency button is pressed or the control of the air bags and / or belt tensioner sends them Trigger a corresponding control signal to the radio telephone to send it to the second Switch antenna connection.

In principle, switching to the emergency antenna takes place according to different solutions:

With simple solutions, the establishment of an emergency call connection in the radio telephone triggers inevitably a switchover to the connection for the emergency antenna, regardless of Functional state of the main antenna. It is assumed that the emergency antenna is on Because of their protected installation position together with the separate antenna cable high probability is still functional.

This creates the problem that both when connecting the antenna in the Vehicle manufacturing as well as defects or damage when using the vehicle the antenna line to the emergency antenna can occur, which remain undetected because it is not used for normal operation. Thus, in an emergency, under certain circumstances the antenna is not working. In addition, with an internal installation of the emergency antenna Efficiency is generally lower than that of the main antenna due to its installation position. This may lead to a connection being established in an unfavorable vehicle position to the base station is possible with an intact main antenna, but not with the less powerful emergency antenna.

To avoid this deficiency, radio telephones with multiple antenna connections lead and extended equipment periodically, for example every 10th Minutes, a test procedure in which the antennas operate one after the other taken and checked for functionality. This is done, for example by comparing the strength of the received signals. Doing so will result in errors and damage recognized and reported on the antennas and lines, and in time for one functional antenna branch switched. The test procedure is usually too performed when an emergency call is triggered, so that only the less powerful Emergency antenna is switched if the main antenna is canceled, for example of the antenna rod has failed.

If both antennas due to different designs and locations also show different reception results, this method is more unequal Intensity of the received signals not very reliable.

A test procedure is carried out in accordance with the document EP 0 859 237 A1 Measurement of the antenna adaptation by determining the reflection factor on the Antenna line with a bidirectional directional coupler and a circuit for Forming the quality signal. The disadvantage of this solution is the high effort for both the hardware as well as for the software to implement the test procedure.

In addition, a device is already from the document DE 196 27349-A1 known for testing vehicle antennas which are in a current loop Receiving coils from vehicle antennas constantly with a low quiescent test current supervised. The receiving coils take along a rail vehicle Line conductor, such as the rails or the overhead line, inductive signal currents. The Quiescent test current is preferably a direct current and continuously indicates that all Antennas are both present and connected to the vehicle.

However, it is disadvantageous that these vehicle antennas are not used in motor vehicle construction preferred antenna form, such as an excited to earth Rod antennas, but receiving coils for inductive signal coupling. The solution is So applicable to motor vehicles only if instead of the previously used advantageous Rod or dipole antennas with an open rod radiator are known folding dipoles with a closed loop heater. However, this is compared to the used solutions complex and offers none for the intended application essential advantages. Another disadvantage of the known solution is that a Short circuit of the antenna line is also displayed as a functioning antenna.

It is therefore the object of the invention to check the operational readiness at least one antenna for a radio telephone a simple, inexpensive To create circuit arrangement which avoids the aforementioned shortcomings and is largely applicable regardless of the antenna shape. In addition, the Invention possible when connecting several antennas to a radio telephone Clearly identify connection errors.

The solution according to the invention includes an antenna with an open radiator, for example a rod heater. This has a first end at which you can remove it or feeding the RF signal, an antenna line is connected, and a second End, which projects openly into the room, so that a capacity of the rod is distributed in the room an RF path that forms the signal circuit for message communication closes.

To solve the task, the radio telephone sends one via the antenna line Test current to the antenna. This happens regardless of the signal current. The test current is advantageously a direct current or an alternating current with a wavelength that is around a Is many times larger than the wavelength of the signal current.

According to the invention, a secondary path with an impedance is on the radiator connected, which is a rear for the test current to the antenna line Current path forms and which is parallel to the RF path. At this impedance, the Test current a voltage drop.

In contrast to the known solution, the circuit arrangement has one Voltage evaluator on, which is constantly on the antenna connections of the radio telephone monitors the voltage that occurs across the impedance as a result of the test current. In order to The radio telephone not only recognizes whether the rod radiator is correctly connected to the antenna connection is connected, but at least also possible short circuits of the antenna line.

The impedance value of the secondary path lies both for the signal current and for the test current many times over the radiation resistance of the antenna. The Impedance at the radiator is short in relation to the transmission wavelength Connection line connected.

According to a special feature of the invention, the impedance of the Secondary paths from a structure with an extended body length, which for example as Individual component has a length which is in the order of magnitude of the rod radiator, or a series connection of several discrete individual elements, so that the connecting lines to the individual elements in the secondary path in relation to the operating wavelength are short and influence the RF properties of the radiator as little as possible.

FIG. 1

das Grundprinzip der Schaltungsanordnung gemäß der Erfindung

FIG. 2

eine Ausführungsform der Schaltungsanordnung gemäß der Erfindung mit mehreren Antennen

FIG. 3a bis 3c

weitere Ausführungsformen der Schaltungsanordnung gemäß der Erfindung mit mehreren Antennen

FIG. 4 bis 6

verschiedene Antennenformen für die Schaltungsanordnung entsprechend der Erfindung mit Stabstrahlern

FIG. 7

eine Ausführung mit einer Wendelantenne

FIG. 8

eine Antennenform mit einem senkrecht strahlenden Dipol und

FIG. 9

eine Antennenform mit einer Flächenantenne

The invention will be explained below using exemplary embodiments. The corresponding drawings show:

FIG. 1

the basic principle of the circuit arrangement according to the invention

FIG. 2nd

an embodiment of the circuit arrangement according to the invention with several antennas

FIG. 3a to 3c

further embodiments of the circuit arrangement according to the invention with a plurality of antennas

FIG. 4 to 6

different antenna shapes for the circuit arrangement according to the invention with rod radiators

FIG. 7

a version with a spiral antenna

FIG. 8th

an antenna shape with a perpendicularly radiating dipole and

FIG. 9

an antenna shape with a surface antenna

A radio telephone 10 has, as FIG. 1 shows, a transmitting / receiving part RF. This is connected via an antenna connection 12 to an antenna 14, which is preferably designed as an external antenna and is arranged, for example, on the roof of a vehicle, not shown. An antenna line 16, in the present case a coaxial cable, which is usually laid under the interior trim of the vehicle, connects the antenna 14, which is remote from the radio telephone 10, to the antenna connection 12. As a result of the concealed installation, errors and damage to the antenna line 16 and the antenna connection 12 Visible with difficulty. The antenna connection 12 contains a signal contact O _S and a ground contact O ₀ .

In the present example, the antenna 14 is a vertical known per se arranged rod radiator with a length of approximately a quarter of Transmission wavelength λ of the transmit / receive signal. The antenna line 16 is on lower end of the radiator connected. The other end protrudes for acceptance / delivery of high frequency radiation open into the room.

As is known, the open end of the radiator forms a capacitance C _E distributed in space, which, as a capacitive RF path, closes the circuit for the high-frequency signal current I _HF without a galvanic path between the open radiator end and the ground contact GND. Since the antenna 14 is attached to a vehicle body, there is a direct connection between the ground contact GND, the antenna line 16 and the conductive surface of the body.

In addition to a transmitting / receiving part RF, both a voltage source and an input of a voltage evaluator are connected to the signal contact O _S. In the present example, the voltage source provides a source voltage U _S and causes a test current I _C to flow to the antenna 14 via a source resistor R _S. Instead of the voltage source, however, a current source can be used, which advantageously provides a constant current. In this embodiment, the voltage evaluator is a window comparator COM, which determines whether its input voltage U _{IN is} within a predetermined range.

According to the invention, the rod radiator of the antenna 14 is connected directly to a secondary path, which contains an impedance Z. The secondary path closes the circuit for the test current I _C from the rod radiator to the GND ground contact. The impedance Z forms a voltage divider with the source resistance R _S. The test current I _C generates a test voltage U _C at the impedance Z, the magnitude of which depends on the value of the impedance which is effective between the signal contact O _S and the ground contact O ₀ . If the antenna 14 is missing or not connected, the test voltage is U C. = U S while the antenna connection 12 or the antenna line 16 is short-circuited, the voltage U C. / n = 0 is. The window comparator COM compares the test voltage U C. = U IN with a reference _voltage U _REF and generates an indication signal U _O for a control circuit of the radio telephone 10, which corresponds to the functional state of the antenna 14.

The influence of the secondary path on the radiation properties of the antenna 14 To keep it as low as possible, the impedance Z is connected to the rod radiator a connection line that is short in relation to the transmission wavelength λ.

The ratio of impedance Z and source resistance R _S is advantageously chosen such that the window comparator COM clearly shows the test voltage when the antenna 14 is functioning U C. = U S / n at the signal contact O _S differs from the source voltage U _S , which occurs in the event of an error on the antenna 14. For the function of the circuit arrangement, it is important that the impedance Z is connected as firmly as possible to the antenna 14, so that the absence of the antenna 14 by the rise in the test voltage U _C at the signal contact O _{S is} recognized as reliably as an interruption in the antenna line 16 The impedance Z can be formed both by a discrete ohmic resistor R and by a conductive structure, such as a thin high-resistance conductor track, which is mounted in the antenna body or its surface as an insulated resistor track. A complex arrangement, such as an inductor with a correspondingly high series resistance, can also be used advantageously.

According to a particularly advantageous embodiment, the impedance Z is an ohmic resistance with a resistance value approximately or equal to the source resistance R _S , so that approximately half the source voltage U _S is at the signal contact O _S as in the present example.

A coupling capacitor C _{K is} arranged between the signal contact O _S and the RF port of the transmitting / receiving part RF, which prevents the circuit arrangement for testing and the transmitting / receiving part RF from influencing one another. The decoupling resistor R _K reduces the load on the high-frequency signal circuit I _HF through the input of the window comparator COM.

FIG. 2 shows a radio telephone 30 with a transmitting / receiving part RF, which is alternatively connected either to the antenna 14 or to an antenna 20 via an antenna selector switch 18, for example in the form of a relay. In contrast to the previously described embodiment, the radio telephone 30 has, in addition to the antenna connection 12, a further antenna connection 22 with a signal contact O _S 2.

It is assumed that the antenna selector switch 18 is switched to the signal contact O _S 1 of the antenna connector 12 in its rest position. Then this connection is occupied by the main antenna, which is positioned at a favorable receiving and transmitting location, and an emergency or alternative antenna is located at the antenna connection 22. Each antenna 14, 20 is connected via a separate antenna line 16, 24 and contains a secondary path with its own impedance, in the present case the resistors R1 and R2. In this embodiment, the source voltage U _S is connected to the output of the antenna selector switch 18, so that it also switches the current paths for the test currents I _C 1 and I _C 2 to the antennas 14, 20.

To establish a telephone connection, the antenna connection 12 has priority over the antenna connection 22 and the antenna selection switch 18 is predominantly in the corresponding position. During this time, regardless of the activity of the signal current I _HF , the test current I _C 1 flows continuously to the antenna 14 in order to monitor its operational readiness. In the present embodiment, the voltage evaluator VE is a window detector circuit for DC voltages, which constantly checks whether the test voltage U _C at the output of the selector switch 18 is within a target range. If there is a short circuit or an open circuit at the antenna connection 12, the test voltage is outside the target range and signals that the antenna 14 is no longer ready for operation with certainty. Then the voltage evaluator VE immediately switches over to the emergency antenna, the antenna 20, with its output signal U ₀ , in order to restore the operational readiness of the system.

In order to monitor the operational readiness of the antenna 20, which is never active when the antenna 14 is intact, according to a further feature of the invention, a control circuit, not shown, switches the antenna selector switch 18 periodically for a short period each time via the control connection S while the radio telephone 30 is idle Signal contact O _S 1 to signal contact O _S 2 around without a signal current I _HF flowing. The test current I _C 2 flows through the resistor R2. If, when switching over to antenna 20, the test voltage U _{C is} outside the target range due to a fault in the antenna connection 22, the radio telephone 30 signals, for example optically by means of a display in its display and / or acoustically, that the emergency antenna is not ready to be repaired . Since the communication system is still working in the event of an error on the emergency antenna, the telephone operation is carried out unchanged via the antenna 14.

It is advantageous that the test currents I _C 1, I _C 2 flow independently of the signal current I _HF , so that switching to the antenna 20 is possible immediately after the antenna 14 has failed. Another advantage of the circuit according to FIG. 2 is that the operational readiness of the antenna selector switch 18 is constantly checked.

According to an extension of the invention, the resistors R1 and R2 in the secondary paths depending on the designs of the antennas 14, 20 different Resistance values. This allows the control circuit of the radio telephone 30 or a when mounting the antennas on the radio telephone connected external test device Automatically detect antenna types that are connected to antenna connections 12 and 22 are connected. This enables a corresponding display of swapped connected antennas 14 and 20 and / or a corresponding internal correction the antenna selector switch 18. The latter allows the antenna connections 12 and 22 at Assemble as you like. For this purpose, the antenna selector switch 18 is advantageous Impulse relay or similar executed so that after identifying the connected antennas 14, 20 a set pulse the antenna selector switch 18 in the sets that of two positions, in the outside a preferred antenna (14), that is Main antenna, is connected.

Also a simple indication that an incorrect antenna design has been installed to realize with it.

Because the transmission power in car phones compared to conventional mobile phones about four times, measures can also be taken against one impermissibly high transmission field strength can be triggered inside the vehicle. Usually becomes the main antenna of a car phone outside the vehicle body at a distance attached to the occupants in order to influence, among other things, this transmission power to keep the vehicle occupants low. Receives the after the failure of the main antenna Auxiliary antenna inside the vehicle has the same power, so there can be a strong transmission field pose a risk to the health of the occupants. Even unfavorable multiple reflections on the inner surfaces of the body can spread the broadcast signal to disturb. When such an antenna is recognized, for example, the Control circuit the transmitter / receiver part RF, the active antenna connector To reduce transmission power. This takes place primarily if, for example, after a visit to a car wash was forgotten, the removable outdoor antenna to be reassembled and normal telephone operation via the emergency antenna runs. At the Triggering an emergency call should, however, the transmitting / receiving part RF that of the Provide the maximum power required by the base station.

In this embodiment of the invention, the voltage evaluator shows VE for everyone Antenna design a separate detector window.

It goes without saying that in practice the voltage evaluator VE can be contained in the digital control circuit of the radio telephone. In such a case, there is an analog / digital converter at its input for converting the test voltage U _C into a digital value. The windows are represented by one or more value ranges of digital values and the digital value at the converter output is checked whether it lies in the or one of these value ranges. As a further alternative to the voltage evaluators VE mentioned, measuring circuits for alternating voltage amplitudes are also conceivable, provided an alternating current source generates the test currents I _C 1 and I _C 2.

Figures 3a to 3c show further embodiments of the invention. These have the advantage that the operational readiness of both antennas 14 and 20 is continuously monitored by the test currents I _C 1 and I _C 2 both during radio / transmission operation and in the standby of the radio telephone 40. For this purpose, the radio telephone 40, in contrast to the radio telephone 30, has a separate source resistor R _S 1 or R _S 2 for each antenna connection 12, 23, which is connected directly to the corresponding signal contact O _S 1 and O _S 2.

The execution according to FIG. 3a also contains a separate voltage evaluator VE1 and VE2 for each antenna connection 12, 22, each of which is connected to the corresponding signal contact O _S 1 and O _S 2 via a decoupling resistor R _K 1 or R _K 2. Depending on the corresponding test voltages U _C 1 and U _C 2, an indication signal U _O 1 continuously indicates the operational readiness of antenna 14 and an indication signal U _O 2 indicates the operational readiness of antenna 20.

In contrast, the designs according to FIG. 3b and FIG. 3c only the voltage evaluator VE1. According to a further feature of the invention, all possible combinations of functioning and / or faulty antenna connections 12 and 22 are identified by a corresponding voltage value that only occurs with the specific combination. For this purpose, the decoupling resistors R _K 1 and R _K 2 combine the test voltages U _C 1 and U _C 2 or U _C 3 and U _C 4 of the two antenna connections 12 and 22, one decoupling resistance being a multiple n greater than the other, for example R K 2 = 3 rows K 1 . In addition, both decoupling resistors R _K 1 and R _K 2 are many times larger than the resistors R1 and R2 in the secondary paths and the input circuit of the voltage evaluator VE1 has an electrometer input, ie a very high input resistance R _IN >> R _K 2. With these The following useful effect occurs under conditions:

As long as the same connection conditions are present at both antenna connections 12 and 22, the resistance ratio R _K 1: R _K 2 remains without influence on the level of the input voltage U _IN for the voltage evaluator VE1 as a result of the electrometer input. If both antennas 14, 20 are missing, the input voltage arises U IN = U C. on. Are both antennas ready for use and the resistors R1 = R S 1 and R2 = R S 2nd is the input voltage U IN = 0.5 U C. , and if both antennas are short-circuited, the input voltage U _IN = 0 is set.

If, however, there are unequal impedances at the antenna connections 12 and 22, there is consequently also a difference .DELTA.U _C between the test voltages U _C 1 and U _C 2, which has an influence on the input voltage U _IN . The decoupling resistors R _K 1 and R _K 2 form a voltage divider for this difference, and add the divided voltage difference ΔU _C to the smallest test voltage U _C 1 or U _C 2.

Due to the unequal decoupling resistors R _K 1 and R _K 2, a different division ratio is effective for the difference ΔU _C depending on the antenna connection at which the highest test voltage U _C 1 or U _C 2 is applied.

Leerlauf", betriebsfähig" oder kurz geschlossen" aufweisen. Damit ergeben sich neben der Möglichkeit, dass beide Antennen betriebsfähig sind, acht weitere mögliche Kombinationen, bei denen mindestens eine Antenne nicht betriebsfähig ist. Für alle diese Kombinationen nimmt die Eingangsspannung U_IN je nach Zuordnung der Antennen zu den Antennenanschlüssen 12, 22 einen für jede Kombination typischen, von den drei vorgenannten Fällen abweichenden Spannungswert an. Dieser ermöglicht auf Grund der typischen Höhe ein eindeutiges Zuordnen jeder Störung zum entsprechenden Antennenanschluß.
Fehlt beispielsweise die Antenne 14 und ist die Antenne 20 funktionsfähig, so beträgt die Prüfspannung UC1 = US , die Prüfspannung UC2 = 0,5 US und die Differenz ΔUC = 0,5 US . Die Differenz ΔU_C wird im Teilerverhältnis N1 = RK2 : (RK1 + RK2) geteilt. Mit dem genannten Verhältnis der Entkoppelwiderstände RK2 = 3 RK1 wird N1 = 3 RK1 : (RK1 + 3 RK1),
d.h., N1 = 3 : 4 = 0,75. Somit ist die Eingangsspannung UIN = UC2 + 0,75 ΔUC UIN = 0,5 US + 0,5*0,75 US = 0,5 US + 0,375 US = 0,875 US .
Fehlt jedoch die Antenne 20 und ist die Antenne 14 funktionsfähig, so beträgt die Prüfspannung UC1 = 0,5 US , die Prüfspannung UC2 = US und die Differenz ΔUC = 0,5 US . Die Differenz ΔU_C wird jetzt jedoch im Teilerverhältnis N2 = RK1 : (RK1 + RK2) geteilt. Dann ist
N2 = RK1 : (RK1 + 3 RK1) = 1 : 4 = 0,25 und die Eingangsspannung UIN = UC2 + 0,25 ΔUC . D.h. die Eingangsspannung UIN = 0,5 US + 0,125 US = 0,625 US unterscheidet sich eindeutig von der bei der vorangegangenen Kombination.After assembly, each antenna 14 and 20 can have one of three possible connection states:

Neutral", operational "or In addition to the possibility that both antennas are operational, there are eight further possible combinations in which at least one antenna is not operational. For all these combinations, the input voltage U _{IN takes,} depending on the assignment of the antennas to the antenna connections 12 , 22 indicates a voltage value that is typical for each combination and differs from the three aforementioned cases, and because of the typical level, this enables a clear assignment of each interference to the corresponding antenna connection.
If, for example, the antenna 14 is missing and the antenna 20 is functional, the test voltage is U C. 1 = U S , the test voltage U C. 2 = 0.5 U S and the difference ΔU C. = 0.5 U S . The difference ΔU _C is in the division ratio N1 = R K 2: (R K 1 + R K 2) divided. With the specified ratio of the decoupling resistors R K 2 = 3 rows K 1 becomes N1 = 3 rows K 1: (R K 1 + 3 rows K 1) ,
that is, N1 = 3: 4 = 0.75. So the input voltage U IN = U C. 2 + 0.75 ΔU C. U IN = 0.5 U S + 0.5 * 0.75 U S = 0.5 U S + 0.375 rev S = 0.875 rev S .
However, if the antenna 20 is missing and the antenna 14 is functional, the test voltage is U C. 1 = 0.5 U S , the test voltage U C. 2 = U S and the difference ΔU C. = 0.5 U S . However, the difference ΔU _C is now in the division ratio N2 = R K 1: (R K 1 + R K 2) divided. Then
N2 = R K 1: (R K 1 + 3 rows K 1) = 1: 4 = 0.25 and the input voltage U IN = U C. 2 + 0.25 ΔU C. . Ie the input voltage U IN = 0.5 U S + 0.125 rev S = 0.625 U S is clearly different from that of the previous combination.

However, if antenna 20 is short-circuited and antenna 14 is functional, the test voltage U _C 1 = 0, the test voltage U C. 2 = 0.5 U S and the difference as well ΔU C. = 0.5 U S . Since the smallest test voltage U _{C is} 1 = 0 and the division ratio N2 = 1: 4 is effective U IN = 0.125 rev S on.

However, if the antenna 14 were short-circuited and the antenna 20 was functional, the input voltage would be N2 = 1: 4 because of the division ratio U IN = 0.375 rev S .

It can be seen from the explanations that any possible combinations with at least one disturbed antenna connection 12 or 22 assume the input voltage U _IN a voltage value typical for this combination. This is particularly advantageous when the antennas 14 and 20 are mounted on the radio telephone 40, because an error can also occur at both antenna connections 12, 22. In this case, the voltage evaluator VE1, as part of the control circuit of the radio telephone 40, has the task of comparing the digitized value of the input voltage U _IN with permanently stored value ranges and of outputting a data signal DS which uniquely identifies the current state of the assignment of the antenna connections 12 or 22. This signal uses the control circuit of the radio telephone 40 or an analysis device connected during the assembly for error display. Each connection is uniquely assigned its current status. Even extreme error messages, such as Main antenna interrupted or not available! - Emergency antenna short-circuited! "Can thus be realized.

FIG. 3c also shows two further features of the invention. The execution of FIG. 3c is based on the embodiment according to FIG. 3b and takes into account the fact that the present number of a total of nine possible combinations of error-free and faulty antenna connections 12, 22 can only be evaluated inexpensively with a microcomputer which is connected to an analog / digital converter. It is disadvantageous, however, that many analog / digital converters of microcomputers only work faultlessly due to an asymmetrical voltage supply if the input voltage U _{IN is} above a minimum value. In order to correct this deficiency in a simple manner, the invention are according to a further feature in series to the Qellenwiderständen R _S1 and R _S2 series resistors R _V 1 and R _V 2 and the Entkoppelwiderstände R _K1 and R _K2 are at the connecting points connected in series. As a result, the test voltages U _C 3 and U _C 4 contain the minimum value that the test current I _C 1 or I _C 2 causes at the series resistors R _V 1 and R _V 2, even if the antenna connection 12 or 22 is short-circuited, so that the analog / The digital converter of the voltage evaluator VE1 is working correctly.

According to a further feature of the invention, these series resistors R _V 1 and R _V 2 are used to identify, in addition to the nine possible combinations of the antenna states mentioned, the case in which both antennas 14, 20 are connected interchanged. This is achieved in that, on the one hand, the antennas 14 and 20 have different resistances R ₁ , R ₂ in the secondary branches, as already shown, and on the other hand the values for the series resistors R _V 1 and R _V 2 are selected in this way that for both antenna connections 12, 22 the sum of the corresponding resistor R1 or R2 in the secondary branch and the series resistor R _V 1 or R _V 2 in series therewith are equal to one another, that is R1 + R V 1 = R2 + R V 2nd is. This has the advantage that the above-mentioned typical voltage values for the input voltage U _IN only occur on an intact antenna if the antennas 14, 20 are not interchanged at the antenna connections 12, 22. The following have proven to be favorable resistance conditions: R S 1 = R S 2nd ; R S 1 = R1 + R V 1 and R S 2 = R2 + R V 2nd , being in a secondary branch, for example R1 = 0.5 R S 1 and R V 1 = 0.5 R S 1 and in the other R2 = 0.75 R S 1 and R V 2 = 0.25 R S 1 are advantageous values. It is obvious that when both antennas 14, 20 are correctly connected, the test voltages U C. 3 = U C. 4 = 0.5 U S amount, while with swapped antennas 14, 20 these are like the ratio of the sums
(R2 + R V 1): (R1 + R V 2) = (0.75 + 0.5): (0.5 + 0.25) = 1.25: 0.75 = 5: 3 behavior.

Another advantage of the solution according to the invention is that both the source resistances R _S 1 and R _S 2 and the resistors R1 and R2 in the secondary paths can be selected to be large enough that the test currents I _C 1 and I _C 2 supply the operating power of the radio telephone 10, 30 or 40 only insignificantly. In practice, for example, the source resistances R _S , R _S 1 and R _S 2 and the resistors R1 and R2 are around 10 kΩ and the test currents I _C 1 and I _C 2 are less than 1 mA. In addition, the coupling resistors R _K , R _K 1 and R _K 2, the source resistors R _S , R _S 1 and R _S 2 and the resistors R1 and R2 are dimensioned so that the influence of the entire detection circuit on the RF circuit of the Cellular phones 10, 30 and 40 is minimal. Another advantage of the invention is that it is also indicated if an incorrect antenna type is connected to the antenna connections 12, 22 when the vehicle is being installed. For example, a radio antenna that has no secondary path.

Figures 4 to 8 show different forms of antennas for the circuit according to the invention. The antennas in FIGS. 4 to 6 are so-called λ / 4 vertical radiators with a rod length l1 = λ / 4 . Here λ denotes the transmission wavelength.

FIG.4 shows a particularly inexpensive version for an antenna with a Resistor R directly between the HF connection Si and the ground connection GND. The box 26 represents a non-conductive covering for the area of the base, which connects the resistor R mechanically with the rod radiator. So that causes Breaking of the antenna 14 at a structurally planned predetermined breaking point in the area of Base bracket or disassembly also the removal of the side path with the Resistor R and thus leads to the desired detection by the circuit in Radio telephone 10, 30 or 40.

While the antenna according to the embodiment according to FIG. 4 requires a constructive measure that ensures a break at the base, the antenna according to FIG. 5 break anywhere. For this purpose, there is an impedance with distributed components, in the present case a series connection composed of at least two individual resistors Ra and Rb, between a connection point on the antenna tip 28 and the ground connection GND. This design enables a secondary path with discrete ohmic resistors to be attached to the outside of the antenna body. In order to suppress RF activities of the leads to the distributed individual resistors Ra and Rb as antenna elements, their lead lengths 12 to 14 can be chosen so that each is shorter than λ / 10. Depending on the desired radiation characteristics of the antenna, it may also be advantageous to make the lead length l2 particularly short and the remaining length: l R = l1 - l2 - (length of the individual resistors Ra + Rb) to be distributed over the supply line lengths l3 and l4. In this antenna design, the non-conductive sheathing encloses the entire radiator rod with the individual resistors Ra + Rb and their leads.

FIG. 6 shows a rod radiator 32 which is designed as a hollow body. This points on free end of a head 34 with an enlarged diameter. In the hollow body 32 the secondary path is housed with a resistor R. The location of the resistor R in Head 34 ensures the function of the circuit in this embodiment, if the Rod emitter 32 breaks off at any point. Due to the inner location of the secondary path is a Influence on the radiation characteristics of the antenna is not expected. Only that Length l1 of the rod radiator 32 must be due to the higher spatial capacity of the head 34 Earth can be shortened somewhat.

In the antenna according to FIG. 7 also leads the secondary path with the resistor R. through the interior of the radiator 36. However, the radiator 36 is used for the RF circuit one-sided open conductor coil used, the length of which is significantly shorter than one Rod heater.

Using FIG. 8 shows that the principle of the invention also applies to λ / 2 dipole antennas applicable, which are open at the ends. The present version shows a λ / 2 vertical radiator in the form of an axially fed dipole. The arrangement of the Secondary path corresponds to the design according to FIG. 5. The secondary path can also be used λ / 2 dipole antennas can also be designed in accordance with FIGS. 4 and 6.

FIG. 9 shows the design of a planar antenna, such as that shown in FIG Vehicle interior can be installed as an emergency antenna. The dipole surfaces 42 and 44 are together with the resistor R and a balun BAL on a circuit board PB arranged. The balun BAL points between the inputs and outputs galvanic connections, for example a detour line, and is therefore advantageous included in the constant monitoring of the operational readiness of the antenna.

Claims (18)

Circuit arrangement for checking the operational readiness of at least one antenna (14, 20) for a radio telephone (10, 30, 40) with a control circuit, a test current (I _C , I _C 1, I _C 2) which is independent of a voltage source (U _C ) from a signal current (I _HF ) in an HF path via an antenna line (16, 24) to the antenna (14, 20), and with an evaluation device (COM, VE) mm monitoring the continuity of the test current (I _C , I _C 1, I _C 2), characterized in that each antenna has a radiator which projects openly into the room at one end, and that each radiator has a separate test current for returning it (I _C , I _C 1, I _C 2) A secondary path is connected parallel to the RF path, which has an impedance (Z, R, R ₁ , R ₂ ), the monitoring of the test current (I _C , I _C 1, I _C 2) using a voltage evaluator (COM, VE , VE1, VE2). Circuit arrangement according to claim 1, characterized in that the secondary path with the impedance (Z, R, R ₁ , R ₂ ) is inextricably linked to the radiator, so that breaking off the antenna (14, 20) or dismantling also means that the Secondary path with the resistance R causes. Circuit arrangement according to Claim 1, characterized in that the impedance (Z, R, R ₁ , R ₂ ) is connected to the radiator in the secondary path via a connecting line which is short in relation to the transmission wavelength (λ). Circuit arrangement according to claim 1, characterized in that the impedance (Z, R, R ₁ , R ₂ ) in the secondary path is many times higher than the radiation resistance of the antenna (14, 20). Circuit arrangement according to claim 1, characterized in that in the secondary path a series connection of separate resistors (Ra, Rb) with leads, whose lengths (l2, l3, l4) are less than one tenth of the transmission wavelength (λ), so that the supply lines do not or only have the radiofrequency property of the radiator influence insignificantly. Circuit arrangement according to claim 1, characterized in that the secondary path with the impedance (Z) inside the antenna body. Circuit arrangement according to claim 1, characterized in that the test current (I _C , I _C 1, I _C 2) is either a direct current or an alternating current, with a wavelength which is many times greater than the transmission wavelength (λ) of the signal current (I _HF ). Circuit arrangement according to Claim 1, characterized by a plurality of antenna connections (12, 22) for antennas (14, 20) which an antenna selector switch (18) alternatively connects to a transmitting / receiving part (RF) and which are provided by separate test currents (I _C 1, I _C 2) have branch branches through which they flow. Circuit arrangement according to claim 1 or 8, characterized in that each secondary path contains at least one ohmic resistor (R, R ₁ , R ₂ , Ra, Rb), and that to check the functionality of the corresponding antenna (14, 20) the voltage evaluator (VE , VE1, VE2) at the antenna connection (12, 22) the actual value of the test voltage (I _C , I _C 1, I _C 2) caused by the test current (U _C , U _C 1, U _C 2) with a setpoint (U _REF ) compares. Circuit arrangement according to claim 8 and 9, characterized in that the Secondary paths depending on the design of the antennas (14, 20) resistors (R1, R2) with different resistance values, so the control circuit of the radio telephone (30, 40) via the corresponding voltage evaluator (VE, VE1, VE2) the antennas (14, 20) connected to the antenna connections (12, 22) differentiates according to their design and automatically recognizes their assignment. Circuit arrangement according to claim 10, characterized in that the Control circuit after detection of the assignment of the antenna connections (12, 22) sets the antenna selector switch (18) to the switch position in which the internal Antenna connection with the transmitting / receiving part (RF) is connected to the outside a preferred antenna (14) is connected. Circuit arrangement according to claim 10, characterized in that the Control circuit after detection of the assignment of the antenna connections (12, 22) generates an error message for a display and / or the output / input data configured accordingly for the antenna connections (12, 22). Circuit arrangement according to claim 8 and 9, characterized in that during the waiting operation of the radio telephone (30) a control circuit via a Control input (S) the antenna selector switch (18) periodically for a short period Duration switched from a first antenna (14) to a second antenna (20) also check the functionality of the second antenna (20). Circuit arrangement according to Claims 8 and 9, characterized in that a separate voltage evaluator (VE1, VE2) is provided for the test voltage (U _C 1, U _C 2) of each antenna connection (12, 22). Circuit arrangement according to Claims 8 and 9, characterized in that decoupling resistors R _K 1 and R _K 2 bring the test voltages (U _C 1, U _C 2 or U _C 3, U _C 4) of the antenna connections (12, 22) together, so that a Voltage evaluator (VE1) analyzes the common input voltage (U _IN ) from both antenna connections (12, 22), and that one decoupling resistance is greater than the other in order to provide the voltage evaluator (VE1) with a clear and unambiguous assignment of errors at the antenna connections (12, 22) to enable. Circuit arrangement according to Claim 15, characterized in that the voltage evaluator (VE1) recognizes different typical input voltages (U _IN ) according to the number of possible combinations of errors at the antenna connections (12, 22) by comparison with stored value ranges and these as data signals (DS) outputs and that a control circuit with a microcomputer generates and outputs corresponding error messages corresponding to the output data signal (DS). Circuit arrangement according to Claim 1 or 15, characterized in that series resistors R _V 1 and R _V 2 are connected in series with the source resistors R _S 1 and R _S 2 and that the voltage evaluator (VE1) via decoupling resistors R _K 1 and R _K 2 to the Connection points of the series connection is connected. Circuit arrangement according to claims 10 and 17, characterized in that the values for the series resistors (R _V 1, R _V 2) are selected such that for both antenna connections (12, 22) the sum of the corresponding resistor (R1 or R2 ) in the secondary branch and the series resistor (R _V 1 or R _V 2) lying in series with one another are identical in order to also clearly identify the case in which the two antennas 14, 20 are connected interchanged.

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