Radio apparatus and method having a d.c. component signal superposed on a transmission-signal

[0002] 1. Field of the Invention

[0003] This invention relates to a radio apparatus which is used in a base station in a mobile telephone system and which has receiving/sending equipment and an antenna, in particular, to a method of controlling the radio apparatus in which the receiving/sending equipment and an antenna are disposed apart from each other.

[0004] 2. Description of the Related Art

[0005] In general, a mobile telephone system has a plurality of base stations and a great number of mobile stations communicable with the base station or stations. In this event, each of the base stations is structured by a transmitter/receiver and an antenna unit which is remote from the transmitter/receiver by several meters or so and which is connected to the transmitter/receiver through a cable, such as a coaxial cable. The transmitter/receiver is located indoors while the antenna unit is placed outdoors .

[0006] Under the circumstances, it is necessary to detect, on a side of the transmitter/receiver, failure or trouble which might occur in the antenna unit. To this end, a failure detection circuit is usually included in the transmitter/receiver of each base station to detect the failure or the trouble in the antenna unit and to produce an alarm on detection of such failure or trouble.

[0007] However, it has been found out that such a failure detection circuit can not correctly detect the failure or trouble in the antenna unit. This is because the antenna unit is distant from the transmitter/receiver, which causes a standing wave to occur on the cable between the antenna unit and the transmitter/receiver.

[0008] Specifically, occurrence of the standing wave might often result in wrong detection of the failure or trouble in the antenna unit, since the standing wave has, at a demodulating point, a node at which the standing wave becomes the smallest in amplitude.

[0009] Therefore, it is an object of the invention to solve the above problem.

[0010] It is also another object of the invention to provide a radio apparatus and method of controlling the radio apparatus which can accurately detect trouble of the antenna apparatus which is disposed apart from the receiving/sending apparatus and troubles of connecting between thereof, efficiently send a signal, and protect the sending apparatus when the troubles occur.

[0011] According to a first aspect of the invention, there is provided a radio apparatus including an antenna unit which radiates a transmission signal and a transmitter unit which supplies the transmission signal to the antenna unit through a line between the transmitter unit and the antenna unit. Here, the antenna unit comprises a coupler which partially extracts the transmission signal to produce an extracted signal and a rectifying circuit which rectifies the extracted signal into a d.c. component signal and superposes the d.c. component signal on the transmission signal. On the other hand, the transmission unit comprises a separating circuit which separates the d.c. component signal from the transmission signal.

[0012] According to a second aspect of the invention, the rectifying circuit includes a detector which rectifies the extracted signal into the d.c. component signal.

[0013] According to a third aspect of the invention, the rectifying circuit includes a first coil which superposes the d.c. component signal on the transmission signal.

[0014] According to a fourth aspect of the invention, the separating circuit includes a second coil which separates the d.c. component signal from the transmission signal.

[0015] According to a fifth aspect of the invention, the transmitter unit includes a control circuit which compares the d.c. component signal separated from the transmission signal with a predetermined reference signal and detects trouble when the d.c. component signal is lower than the predetermined reference signal.

[0016] According to a sixth aspect of the invention, the control circuit further decreases the power of the transmission signal when the d.c. component signal as lower than the predetermined reference signal.

[0017] According to a seventh aspect of the invention, the transmitter unit further comprises a variable attenuator which varies the power of the transmission signal and an arithmetic circuit which controls the variable attenuator based on a voltage level of the d.c. component signal separated from the transmission signal.

[0018] According to an eighth aspect of the invention, the transmitter unit further comprises a matching circuit which matches an impedance of the transmitter unit to that of the antenna unit and a matching control circuit which controls the matching circuit based on a voltage level of the d.c. component signal separated from the transmission signal.

[0019] According to a ninth aspect of the invention, the transmitter unit includes a control circuit which determines whether or not the d.c. component signal which is separated from the transmission signal falls within a predetermined range and detects trouble when the d.c. component signal does not fall within the predetermined range.

[0020] According to a tenth aspect of the invention, there is provided a method of controlling a radio apparatus including an antenna unit which radiates a transmission signal and a transmitter unit which supplies the transmission signal. Here, the antenna unit and the transmitter unit being connected electrically from each other, and the method comprises the steps of partially extracting, at the antenna unit, the transmission signal, rectifying, at the antenna unit, the extracted signal into a d.c. component signal, superposing, at the antenna unit, the d.c. component signal on the transmission signal, and separating, at the transmitter unit, the d.c. component signal from the transmission signal.

[0021] According to an eleventh of the invention, there is provided a method of controlling an antenna unit remote from a transmitter unit. Here, the antenna unit which radiates the transmission signal and the transmitter unit which whiles the transmission signal are included in a radio apparatus and connected electrically from each other, and the method comprises the steps of partially extracting the transmission signal, rectifying the extracted signal into a d.c. component signal, and superposing the d.c. component signal on the transmission signal.

[0022] According to a twelfth of the invention, there is provided a method of controlling a transmitter unit. Here, the transmitter unit which supplies a transmission signal and an antenna unit which radiates the transmission signal are included in a radio apparatus and connected electrically from each other, and the method comprises the step of receiving a d.c. component signal via the transmission signal from the antenna unit and separating the d.c. component signal from the transmission signal.

[0023] According to a thirteenth of the invention, the method further comprises the steps of comparing the d.c. component signal which is separated from the transmission signal with a predetermined reference signal and detecting trouble when the d.c. component signal is lower than the predetermined reference signal.

[0024] According to a fourteenth of the invention, the method further comprises the step of decreasing the power of the transmission signal when the d.c. component signal is lower than the predetermined reference signal.

[0025] According to a fifteenth of the invention, the method further comprises the steps of varying the power of the transmission signal based on a voltage level of the d.c. component signal separated from the transmission signal and controlling intensity of the transmission signal which is radiated from the antenna unit so that the intensity may be equal to a predetermined value.

[0026] According to a sixteenth of the invention, the method further comprises the step of controlling matching of an impedance of the transmitter unit to that of the antenna unit so that a voltage level of the d.c. component signal separated from the transmission signal may become maximum.

[0027] According to a seventeenth of the invention, the method further comprises the step of determining whether or not the d.c. component signal which is separated from the transmission signal falls within a predetermined range and detecting trouble when the d.c. component signal does not fall within the predetermined range.

[0028] FIG. 1 shows a block diagram of a radio apparatus according to a first embodiment of the invention;

[0029] FIG. 2 shows a block diagram of an example of a control circuit 14 of the first embodiment shown in FIG. 1; and

[0030] FIG. 3 shows a block diagram of a radio apparatus according to a second embodiment of the invention.

[0031] First Embodiment of the Invention

[0032] Hereinafter, descriptions will be made about a first embodiment of the invention with reference to accompanying drawings.

[0033] As shown in FIG. 1, a radio apparatus according to the first embodiment of the invention includes a transmitter unit 12 which may be incorporated in a transmitter/receiver (not shown) disposed indoors and an antenna unit 13 which is close to an antenna 11 and which is disposed outdoors.

[0034] Also, the transmitter unit 12 and the antenna unit 13 are connected to each other through a high-frequency cable 17, such as a coaxial cable.

[0035] In FIG. 1, the transmitter unit 12 includes a modulator 1 which produces a modulated wave, a variable attenuator 2 which has a variable attenuation factor controlled by a control circuit 14 as described later, and an amplifier 3.

[0036] The modulated wave which is modulated by the modulator 1 is supplied to the amplifier 3 through the variable attenuator 2.

[0037] The modulated wave is amplified by the amplifier 3 into an amplified signal of predetermined electric power, and is supplied from an antenna connector 4 through a capacitor 35. The capacitor 35 serves to cut a d.c. component.

[0038] The antenna connector 4 is connected to one end of a coil 5, and the other end of the coil 5 is connected to the control circuit 14.

[0039] The coil 5 has an inductance specified by a high reactance value at a frequency of the modulated wave (for example 1.9 GHz) and, consequently, allows only a d.c. component to pass therethrough.

[0040] The control circuit 14 supplies a control voltage V_cthaving a value based on the d.c. component which passes through the coil 5 and controls the attenuation factor of the above-described variable attenuator 2 and produces an ALC alarm signal SAL when any failure is detected by the control circuit 14.

[0041] An antenna connector 6 is attached to the antenna unit 13 and is connected to the antenna 11 through a coupler 8 including a directional coupler.

[0042] One end of the coupler 8 is terminated through a terminator 10, such as resistor, while the other end of the coupler 8 is connected to a detector 9.

[0043] The illustrated detector 9 is formed by a diode for rectification. The diode may be replaced by a smoothing circuit including a capacitor.

[0044] In the illustrated example, the detector 9 has an anode electrode connected to the coupler 8 and a cathode electrode connected to the antenna connector 6 through a coil 7.

[0045] The coil 7 also has an inductance specified by a high reactance value at a frequency of a transmission wave sent through the antenna 11.

[0046] The transmission wave is obtained by being modulated by the modulator 1 of the transmitter unit 12 to be attenuated at the variable attenuator 2 to a predetermined level which is determined under control of the control circuit 14 and to be amplified by the amplifier 3.

[0047] The amplifier 3 amplifies the modulated wave into the amplified signal to supply the amplified signal to the antenna connector 4 as the transmission signal.

[0048] Then, the transmission wave is supplied from the antenna connector 6 to the antenna unit 13, and radiated from the antenna 11 through the coupler 8.

[0049] The transmission wave which is supplied from the antenna connector 6 to the antenna unit 13 is partially separated through the coupler 8. The detector 9 rectifies the output of the coupler 8 to generate a rectified voltage V_DT. The rectified voltage V_DTis then superposed to the original transmission wave through the coil 7.

[0050] On the other hand, the rectified voltage V_DTis partially sent back to the transmitter unit 12 and is taken out by the coil 5 to be supplied to the control circuit 14. ache control circuit 14 executes an ALC (Automatic Level Control) operation to control the attenuation factor of the variable attenuator 2 based on the rectified voltage V_DT.

[0051] In FIG. 2, the control circuit 14 includes comparators 21, 22, and 23.

[0052] The comparators 21 and 22 are given reference voltages V_R1(in this embodiment, 4 [V]) and V_R2(in this embodiment, 1 [V]), respectively. Comparison results of the comparators 21 and 22 are supplied as ALC alarm signals S_ALthrough an OR gate 24.

[0053] On the other hand, the comparator 23 is given a reference voltage V_R3(in this embodiment, 0.5 [V]). Comparison result of the comparator 23 is produced as antenna alarm signal S_AN.

[0054] The control circuit 25 further includes an arithmetic circuit which is operable in response to the control voltage V_CTbased on the rectified voltage V_DT. A detailed description and a figure about the arithmetic circuit 25 will be omitted because the arithmetic circuit 25 itself is known in the art.

[0055] The control voltage V_CTsupplied from the arithmetic circuit is provided through an analog switch 26, wherein the signal S_ANfrom the comparator 23 is given to a control input terminal of the analog switch 26.

[0056] In this embodiment, the variable attenuator 2 is adjusted or trimmed so that a standard output may be supplied, and the rectified voltage V_DTat that time is set as the reference value (in this example, 3.0[V]).

[0057] The control circuit 14 increases the attenuation factor to decrease power of the transmission wave when the rectified voltage V_DTis higher than the predetermined reference value (for example, V_DT=3.5[V]). On the other hand, the control circuit 14 decreases the attenuation factor to increase power of the transmission wave when the rectified voltage V_DTis lower than the predetermined reference value (for example, V_DT=2.5[V]).

[0058] The control circuit 14 converges the rectified voltage V_DT(for example, 3[V]) by the above mentioned operations.

[0059] Also, the control circuit 14 supplies the ALC alarm signal S_ALwhen the rectified voltage V_DTdoes not fall within the predetermined voltage range. Therefore, in this embodiment, the ALC alarm signal S_ALis supplied when the rectified voltage V_DTexceeds 4 [V]or is lower than 1 [V].

[0060] In this embodiment, when any trouble occurs in electrical connection between the antenna connector 4 and the antenna connector 6 (for example, breakage of a wire), the transmission wave is not transmitted to the antenna unit 13. Thereby, the detector 9 cannot produce the rectified voltage V_DTand, as a result, the rectified voltage V_DTis not sent back to the transmitter unit 12.

[0061] Therefore, the voltage supplied to the control circuit 14 is close to 0. However, when the ALC operations are continued in the Move case, the amplifier 3 generates maximum output since the control circuit 14 minimizes the attenuation factor of the variable attenuator 2.

[0062] In order to avoid the above-mentioned situation, the control circuit 14 not only cuts off the control voltage V_DTto decrease output power of the amplifier 3 but also produces the antenna alarm signal S_ALwhen voltage supplied to the control circuit 14 is low (in this embodiment, less than or equal to 0.5 [V]).

[0063] Second Embodiment of the Invention

[0064] Hereinafter, a description is made about a second embodiment of the invention with reference to FIG. 3. Also, parts shown in FIG. 3 each of which is the same as the corresponding part shown in FIG. 1 have the same numeric symbols as the corresponding parts shown in FIG. 1, and description will be omitted about the same parts.

[0065] In FIG. 3, a transmitter unit 12aincludes a matching circuit 15, which is formed, for example, by a coil for resonance or variable capacitor for controlling voltage.

[0066] In the illustrated transmitter unit 12a, the transmission wave supplied from an amplifier 3 is provided to the antenna connector 4 through a capacitor 35 and the matching circuit 15.

[0067] In this embodiment, a matching control circuit 16 controls the matching circuit 15 and determines a matching point by retrieving a point which has maximum rectified voltage V_DT.

[0068] The Matching point is then stored in the matching control circuit 16 and is held until the antenna 11 is modified.

[0069] A description about operations after the determining operation, namely ALC operation will be omitted since the operations are the same as those of the first Embodiment of the invention.

[0070] According to the invention, transmission output can be kept at a certain level, regardless of the distance between a transmitter unit and an antenna since the detector is located in the vicinity to the antenna rather than inside the transmitter unit.

[0071] Also, according to the invention, the detector cannot rectify the transmission wave when the antenna is not connected to the transmitter unit since the illustrated antenna unit has a demodulation circuit. Therefore, it is easy to determine whether the antenna unit is normally connected or not.

[0072] Further, according to the invention, it is previously possible to know an impedance between the transmitter unit and the antenna unit since the detector is included in the antenna unit. Further, the antenna unit is correctly matched with the transmitter unit in impedance since the above-mentioned impedance can be fed back to the matching circuit.