Radio communication apparatus including power supply device

Abstract: A radio communication apparatus includes a power supply device which includes a solar battery connected to each of communication channels via a different switch. A controller constantly monitors the voltage of the solar battery to turn on or off the switches stepwise, so that the number of active channels is reduced stepwise with the decrease in the capacity of the solar battery. The rate of decrease in the capacity of the solar battery is reduced to shorten the period of time during which communication is prevented, whereby operation is insured over a long period of time. Further, communication, i.e., power consumption is averaged to reduce the required capacity of the solar battery.

Description: BACKGROUND OF THE INVENTION The present invention relates to a radio communication apparatus including a power supply device of the type using a solar battery and, more particularly, to a power supply device capable of operating over a long period of time with a relatively small capacity. In a radio communication system suh as a single channel per carrier (SCPC) communication system, a radio communication apparatus whose capacity is relatively small is implemented with a power supply device of the type using a solar battery for the ease of maintenance. It has been customary to construct a solar battery type power supply device such that the voltage of a solar battery is monitored and, when it is lowered to a predetermined level, power supply is interrupted so as to protect the battery and insure its long service life. Further, it is a common practice to use a solar battery having a capacity which is ten times greater than the maximum capacity used, providing for nighttime and rainy weather. A drawback with such a prior art device is that upon the drop of voltage beyond the predetermined level all the communications are shut off although the solar battery may be protected. In addition, the capacity which is approximately ten times greater than the maximum capacity used as stated above is undesirable from the cost standpoint. In the specification of West German Patent Application No. 3502826.2 which was published on August 14 1985, there is described a solar current battery charging apparatus in which when a predetermined battery voltage is exceeded the charging current is simultaneously reduced and a connection between the battery and the consumer is made. A radio communication apparatus will be described below which has a power supply device using a solar battery which is capable of operating over a long period of time with a relatively small capacity. In a particular arrangement to be described there is a plurality of switches, each switch being associated with a respective one of a plurality of communication channels for selectively feeding power from a solar battery to a power supply device, and a controller for turning on or off the switches stepwise by detecting the voltage of the solar battery. Embodiments of the invention will be described below, by way of example, with reference to the accompanying drawings in which:- Fig. 1 is a schematic block diagram showing a radio communication apparatus including a power supply device in accordance with the present invention; and Fig. 2 is a plot representative of qualitative charging and discharging characteristics of a solar battery. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, a radio communication apparatus including a power supply device according to the present invention is shown and generally designated by the reference numeral 10. In the illustrative embodiment, the apparatus 10 is a 9-channel SCPC radio communication apparatus by way of example. As shown, nine terminals 11 to 19 such as telephones and facsimile transceivers are individually connected to the apparatus 10 by independent channels. The apparatus 10 comprises MODEMs 21 to 29, an intermediate frequency (IF) combiner 40, frequency converters 42 and 48, a separator 44, an antenna 46, a divider 50 and a power supply device 100. The power supply device 100 further comprises switches 31 to 39, 54 and 56, a solar battery 52 and a controller 58. Each of the MODEMs 21 to 29 is associated with a respective one of the nine channels. The switches 31 to 39 selectively feed power to the MODEMs 21 to 29. The IF combiner 40 combines modulated carrier waves at the IF stage while the frequency converter 42 serves to raise intermediate frequency to radio frequency. The separator 44 is connected to an antenna 46. The frequency converter 48 is adapted to convert radio frequency to intermediate frequency, and the divider 50 is adapted to divide an IF signal. The switches 54 and 56 are operable to establish and interrupt power supply to the frequency converters 48 and 42, respectively. The controller 58 turns on and off the switches 31 to 39 based on the voltage of the solar battery 52 which it constantly monitors. Also, the controller 58 controls the switches 54 and 56. The operation of the radio communication apparatus 10 will be described by following the flow of signals. Assuming one particular channel, e.g., the channel associated with a telephone 11, a voice signal is modulated by a modulator section of the MODEM 21 to become an IF signal. Applied to the IF combiner 40, the IF signal is combined with other modulated carrier waves into a single IF signal. This composite IF signal is converted by the frequency converter 42 to have a frequency which lies in a radio frequency (RF) band, the resulting signal being transmitted to another apparatus or station by radio via the separator 44 and antenna 46. On the other hand, an answer from another apparatus or station comes in through the antenna 46 in the RF band and then routed through the separator 44 to the frequency converter 48. The output of the frequency converter 48 is divided by the divider 50, then demodulated by a demodulator section of the MODEM 21, and then fed to the telephone 11 as a voice signal. How the power supply to various active portions in communication apparatus is controlled will be described with reference made to Fig. 2 also. Power generated by the solar battery 52 is fed to various active portions via the switches 31 to 39, 54 and 56. Voltage of the solar battery 52 is constantly monitored by the controller 58. When the voltage of the solar battery 52 is lowered to a predetermined level such as V₂, the controller 58 maintains only four of the nine channels which have been supplied with power active. For example, the controller 58 turns off the switches 35 to 39 which are respectively associated with the fifth to ninth channels, while holding the first to fourth channels active. In practice, power supply to those channels which are not being occupied for communication is interrupted for user's convenience. Specifically, a voice detector is installed in each of the MODEMs 21 to 29 to determine whether or not its associated channel is busy, and the controller 58 totally decides the instantaneous condition based on the outputs of the voice detectors so as to deactivate those channels which are not busy. An arrangement may be made such that when the number of busy channels is greater than that of channels to be deactivated, the busy channels are deactivated according to a predetermined priority order. When the voltage of the solar battery 52 is further lowered to, for example, a level V₁ which is lower than the level V₂, the switches 32 to 39 are turned off so that the first channel alone is maintained active. As the voltage is lowered beyond the level V₁ to, for example, a level V₀, all the switches 31 to 39, 54 and 56 are turned off resulting in all the channels being deactivated. In Fig. 2, a curve a shows that voltage is fed to all the active circuits so long as the battery voltage remains higher than V₂. Should such minute threshold voltages V₂ and V₁ be absent, power supply would be entirely interrupted at a time t₁ as indicated by a dashed line in the figure. In the device 10 of the present invention, when the voltage is lowered to V₂, power otherwise consumed by five channels is saved so that the rate of voltage drop is reduced as represented by a solid curve b . Upon the drop of the voltage to V₁, power is fed to one channel only with the result that the rate of voltage drop is further reduced as indicated by a solid curve c . Consequently, the power supply is fully interrupted at a time t₂. Such a sequentially decreasing rate of voltage drop is successful in extending the time at which the last channels becomes deactive, although all the channels will eventurally become unusable. The fact that at least one channel is available for communication means the extension of service time. Further although the number of active channels may be limited as stated above, subscribers can hold communications except when those channels are busy, on condition that the MODEMs are under demand assignment multiple access (DAMA). If desired, the apparatus 10 may be used in such a manner as to secure the last channel for emergency communication. As the voltage of the solar battery 52 is lowered to V₀ and therefore power is not consumed any longer, the battery 52 begins to be charged at a time t₂ which is later than the time t₁, as indicated by a solid curve d . At a time t₃ when the previously stated threshold voltage (V₂ in the example of Fig. 2) is reached, power supply to the communication equipment is resumed. In contrast, a prior art power supply device starts charging a battery at the time t₁ and sequentially charges it as represented by a dashed curve f and, therefore, it is not until a time t₄ at which the battery is sufficiently charged that power is fed to communication equipment. Of course, the inclination or curvature of the curve f is the same as that of the curve d . It follows that the reactivation time t₃ attainable with the device 10 of the present invention is earlier than the reactivation time t₄ particular to the prior art device. The curves shown in Fig. 2 have been discussed simply by neglecting the amount of charge which is stored in the solar battery 52 at the time of power supply to the equipment. This offers no problem so far as the qualitative aspect is concerned. Hence, the device 100 reduces the period of time during which the power supply to the equipment should be interrupted for charging the solar battery 52. Moreover, the communication is averaged due to the threshold levels V₂ and V₁ which are adapted to limit the number of active channels and to lower the voltages for deciding charged conditions. Such averaged communication allows the capacity of the solar battery 52 to be reduced. For example, assume that the MODEMs 21 to 29 and frequency converters 42 and 48 shown in Fig. 1 consume power of 1 W each, i. e. , the total power consumption of 11 W. Then, the prior art device would need a solar battery whose capacity is 110 W which is ten times greater than 11 W. On the other hand, since the number of channels used for communication is averaged to, for example, four in accordance with this embodiment, the solar battery 52 needs only to have a capacity of (4 + 2) × 10 = 60 W even with a ten times greater margin included. Although the wattage of 60 W is smaller than the previously mentioned 110 W, it is of course sufficiently greater than the maximum value of 11 W necessary for using all the channels and therefore brings about no problem. In summary, it will be seen that the present invention provides a radio communication apparatus including a power supply device which reduces the rate of decrease in the capacity of a solar battery, shortens the period of time during which communication is prevented to thereby insure operation over a long period of time, and averages communication, i. e. , power consumption to reduce the required capacity of a solar battery. Although the invention has been described, by way of example, with reference to particular embodiments, it will be understood that variations and modifications thereof, as well as other embodiments, may be made within the scope of the appended claims.

Claims: A radio communication apparatus (10) including a solar battery (52), means (58) for monitoring and controlling the output of the battery (52) and switch means (31 to 39; 54; 56) arranged to interrupt the power supply from the battery (52) when its voltage falls below a predetermined level, characterised in that the switch means (31 to 39; 54; 56) includes a plurality of switches, each switch being associated with a respective one of a plurality of communication channels (11 to 19) or other circuit elements (48; 42) for selectively feeding power from the solar battery (52) to portions of the apparatus (10), the monitoring and controlling means (58) turning on or off particular ones of the switch means (31 to 39; 54; 56) stepwise according to both the level of a detected voltage of the solar battery (52) and a characteristic of selected ones of the associated communication channels (11 to 19). A radio communication apparatus as claimed in claim 1, characterised in that when the voltage of the solar battery (52) has reached a threshold value, the particular ones of the switch means (31 to 39) which are to be turned off are those associated with those of the channels (11 to 19) which are not being used for communication at the time. A radio communication apparatus as claimed in claim 1, characterised in that the apparatus is a part of a single channel per carrier radio communication system.

Inventors: TOKUNAGA TADATSUGU C O NEC COR, TOMIMURA KAZUA C O NEC CORPORA, TOKUNAGA, TADATSUGU C/O NEC CORPORATION, TOMIMURA, KAZUA C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1988
Main classification: H04B1
IPC codes: H04B1, H02J7, H02J1, H04B7