JPH058899B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a system in which a slave station mounted on a moving object such as an automobile and powered by a battery receives weak radio wave signals from a master station. Note that in the following figures, the same reference numerals indicate the same or corresponding parts. Furthermore, logic or levels "High" and "Low" are simply written as "H" and "L".

[Prior art and its problems]

In this type of system, the batteries that power the slave stations are particularly required to have a long lifespan, for example, 5 to 10 years, and therefore the current consumption of the batteries in the slave stations must be kept as low as possible. It is necessary to suppress it. For example, if you install a 200mAH coin-shaped lithium battery as a power source in a slave station and try to guarantee operation for 10 years, the total number of hours in those 10 years will be 24H x 365 days x 10 years = 87600H. Therefore, if the battery is to be continuously energized during this period, the average current that can be supplied by the battery will be 200mAH/87600H = 2.3μA. However, this current value includes not only the current of the circuit for detecting the calling signal from the master station, but also the current of the circuit for receiving the transmission data from the master station at high speed. Therefore, the current value that can be consumed by the above-mentioned ringing signal detection circuit is 1/ of the above-mentioned 2.3μA.
It is a very small value of 2 or less, that is, about 1 μA or less. By the way, in general, the current consumption of a receiving amplifier and its gain (therefore, the receiving detection lower limit voltage of the amplifier)
There is a correlation (therefore, an inverse correlation) with the current consumption, and by increasing the current consumption, it is possible to detect a smaller received voltage (in other words, it is possible to amplify the voltage and determine whether it is above a certain level). Conversely, if the received voltage is large enough, an amplification circuit is not necessary.
Naturally, the current consumption of the receiving circuit can be reduced. The radio waves that can be used for this type of communication for general industrial purposes are generally weak due to legal restrictions, and the current consumption of a high-gain receiving amplifier that can amplify these weak radio waves is as explained above. Since it becomes large, there is a problem that it goes against the goal of extending the life of the battery. On the other hand, an LC resonant circuit is used in the receiving circuit to receive weak radio wave signals, and the input detection voltage is multiplied by Q (for example, 200 to 300 times, but this Q is the resonance of the LC resonant circuit). Q is the value representing sharpness
= ω・L/R. Note that ω is the resonance angular frequency, and R is the series resistance in the LC circuit. ), it is possible to eliminate the need for the above-mentioned high gain amplifier and reduce the current consumption of the calling signal detection circuit of the slave station. However, this method also has the following problems. In other words, the fact that the Q of the LC resonant circuit is high means that the input voltage based on the received radio waves to this circuit (this is proportional to R I (however, I: current in the resonant circuit)) is very small. , a relatively large resonant current I flows, and for example, ω・
This means that a large detection voltage V of L・I (I/ω・C at both ends of C) is obtained, and in this state, between L and C, L・I ² /2≒C・V ² /2 A relatively large amount of energy is exchanged between them. In this way, until energy is accumulated in the LC circuit, it is necessary to input the received radio wave for a corresponding excitation time, that is, a time length proportional to Q, before the arrival of the received radio wave is detected. In other words, obtaining an effective detection voltage from a high-Q LC resonant circuit involves a large time delay, and therefore there is a problem in that the communication speed between the parent and slave stations cannot be increased as is. By the way, the distance from the main station antenna is around 50cm.
In order for a slave station moving at 10 to 20 km/h to communicate effectively with the master station, each communication must be completed within 0.1 to 0.2 seconds at a bit rate of several Kbps. To enable this speed, the Q value must be set to a low value of 30 to 50 in order to reduce the above-mentioned time delay, and therefore it is necessary to use an amplifier with a high gain, as described above. This goes against the desire to reduce the current consumption of the call signal detection circuit.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a wireless data reception system that can reduce the average current consumption of the battery of a mobile slave station and increase the speed at which the slave station receives data transmitted from the master station. shall be.

[Key points of the invention]

The gist of the present invention is to use an LC resonant circuit in the receiving circuit of the slave station, and to set the Q value of the resonant circuit to a high value whenever the slave station is waiting for a calling signal from the master station.
Therefore, the gain of the amplifier used in combination is kept low to reduce the constant battery current consumption, and the next time the slave station detects the ringing signal, a damping resistor is temporarily inserted and connected to the LC resonant circuit. By switching the value of Q to a low value and operating a high gain amplifier, the slave station can receive transmission data from the master station at high speed, and as a result, the battery of the slave station is reduced. The key point is that effective high-speed communication between the parent and slave stations is possible while keeping the average current consumption at a low value. In other words, the main point of the present invention is that a mobile slave station (0
2, etc.) receives weak radio wave signals from a master station (01, etc.), the master station receives a calling signal (modulated Call data 7 in transmission number 8a
A transmission radio wave (such as the part a) and a modulated transmission data signal (such as the part of the calling data 7b in the modulated transmission number 8a) obtained by modulating the carrier signal with a signal containing transmission data following the calling signal. means for transmitting (modulated transmission signal 8a, etc.) (original transmission signal output circuit 70, transmission modulation circuit 8, transmission antenna 9
), and the slave station is equipped with an LC resonant circuit (such as 1) that resonates at the frequency.
and means (high voltage detection amplifier 4, reception controller 6, etc.) for determining that the level of the reception signal (resonance circuit reception signal 11, etc.) of the transmitted radio wave in the resonant circuit has been established at a predetermined value or higher. , Based on this determination, a damping resistor (2
etc.) to the LC resonant circuit (resistance switching SW 3, reception controller 6, etc.), and together with this insertion connection, means for amplifying the received signals in the LC resonant circuit (high gain amplifier 5, etc.). etc.) (via the high gain amplifier opening/closing signal 10, etc.) and reading the transmission data from the master station (receiving controller 6, etc.).

[Embodiments of the invention]

Embodiments of the present invention will be described below based on FIGS. 1 and 2. FIG. 1 is a block circuit diagram showing the configuration of main parts as an embodiment of the system of the present invention, and FIG. 2 is a waveform diagram of signals of each part for explaining the operation of FIG. 1. Next, the configuration and operation of FIG. 1 will be described with reference to FIG. 2. In FIG. 1, the original transmission number 7 (second
In FIG. 1), a carrier signal of a predetermined frequency is passed through a transmission modulation circuit 8 to the original transmitter signal 7 as shown in FIG.
A modulated transmission signal 8a whose amplitude is modulated by , is radiated from a transmission antenna 9 as a radio wave. Here, the original transmission number 7 includes the call data 7a as the "H" part at the beginning as shown in FIG.
It consists of the transmission data 7b following the calling data 7a, and the length of the calling data 7a is Ta.
(that is, the duration of the "H" level) is a value that is sufficiently longer than each bit length Tb in the transmission data 7b. This is to ensure that the level of the received signal of the LC resonant circuit having a high Q value in the slave station is sufficiently established within this time Ta, as will be described later. Next, the modulated transmission signals 8a, which have become radio waves, are received by the LC resonance circuit 1, which becomes the reception antenna of the slave station 02.Resonant circuit reception signals 11 and 11a are then received as signals.
has a waveform as shown in FIG. 2. This signal 11a
The waveform shown in FIG. 2 is a waveform assuming that the Q value of the LC resonant circuit 1 continues to be maintained at a high value. That is, when the amplitude of the resonant circuit receiving signal 11a gradually increases and exceeds a certain voltage value, the high voltage detection amplifier 4 detects the input signal, that is, the voltage across L (or C), and transmits the result to the second As shown in FIG. 4, it is transmitted to the reception controller 6 of the slave station as a high voltage detection amplifier output signal 4a. When the controller 6 receives this signal 4a, it applies a high gain amplifier open/close signal 10 to the high gain amplifier 5 to turn on the power of the amplifier 5, enable the operation of the amplifier 5, and perform the operation as shown in FIG. The attenuation resistance switching signal 14 is connected to the resistance switching switch 3 (note that the switch is
(also abbreviated as SW), and a damping resistor 2 is connected in parallel with L and C of the LC resonant circuit. This results in
The Q value of the LC resonant circuit 1 is switched to a low value. Note that in the state before this switching, the input impedance of the high gain amplifier 5 before activation is a high value, so its current consumption is small, and the high voltage detection amplifier 4 has a low current consumption like a CMOS element. Since the amplifier 4 only needs to have a low amplification factor, its input impedance can be kept at a very high value at all times, and as a result, the slave station 02 is always connected to the master station 01. The current consumption of the reception circuit of the slave station in the state of waiting for a calling signal (calling data 7a) can be kept very small. Now, as mentioned above, by connecting the damping resistor 2 in parallel between L and C, the Q value is lowered, and as a result, the amplitude of the resonant circuit receiving signal 11 (the voltage across the LC resonant circuit 1) is 2. The signal 11b in FIG. 5 has a reduced form. On the other hand, the Q of LC resonant circuit 1
As the value decreases, the response of this resonant circuit to changes in the received signal becomes faster (that is, the time delay is reduced). Therefore, the waveform of this resonant circuit receiving signal 11b is:
Compared to the waveform of the same signal 11a when the Q value is high (FIG. 2, 3), the waveform corresponds almost faithfully to the transmission data 7b in the original transmission signal 7. Even if the amplitude of the resonant circuit receiving signal 11b becomes small as described above, the high gain amplifier 5 is in an operating state at this time, and the high gain amplifier output signal 5a as the output of the amplifier 5 can be used. As a result, as shown in FIG. 2, the original transmission code 7 transmitted on the transmitting side can be demodulated. Although the length (time) Ta1 of the long "H" pulse at the beginning of the high gain amplifier output signal 5a is different from the length (time) Ta1 of the calling data 7a in the original transmission number 7, this is not a problem. That is, the input judgment of the reception controller 6a is made after outputting the high gain amplifier opening/closing signal 10 and confirming that the high gain amplifier output signal 5a is "H".The moment when this signal 5a first falls to "L" is the transmission data. 7
It is determined that it is the start point of b. In addition, the end of the high gain amplifier's reception mode is determined by two conditions: the scheduled number of pulses have been received from the master station, and the reception state with the master station has continued for a certain period of time.
This is done by turning off the power of the high gain amplifier 5 under two conditions, and in this way the slave station 02 enters a state of waiting for a call from the master station 01. Note that when the slave station 02 demodulates this original transmission signal 7, the current consumption of its receiving circuit (mainly of the high gain amplifier 5) increases temporarily, but this period is the same as the period of waiting for a regular call signal. As a result, the average current consumption of this receiving circuit can be kept sufficiently low. [Effects of the Invention] According to the present invention, a slave station detects a calling signal from a master station by detecting the level of a received signal of a high Q LC resonant circuit via a high voltage detection amplifier with extremely low current consumption. After this detection,
Although the Q of the LC resonant circuit is lowered and the current consumption is somewhat higher,
Since the transmitted data from the master station is received at high speed through an amplifier with a large gain, the battery current consumption of the slave station when it is constantly waiting for a ringing signal can be kept as low as possible, and as a result, the battery of the slave station can be reduced as much as possible. The slave station can receive valid transmission data from the master station at high speed while maintaining a low average current consumption. In addition, when a slave station detects a call signal from the master station, it is received by a high-Q LC resonant circuit, so it takes time to detect this call signal, so the possibility of malfunctions in detecting communication requests from the master station is low. It can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the configuration of main parts as an embodiment of the system of the present invention, and FIG. 2 is a waveform diagram of signals of each part for explaining the operation of FIG. 1. 01... Master station, 02... Slave station, 1... LC resonance circuit, 2... Attenuation resistor, 3... Resistance switching SW, 4
...High voltage detection amplifier, 5...High gain amplifier,
6... Reception controller, 70... Original transmission signal output circuit, 8... Transmission modulation circuit, 9... Transmission antenna.

Claims (1)

[Claims] 1. In a system in which a mobile slave station receives weak radio wave signals from a master station, the master station receives a signal of a predetermined level or higher using a carrier signal of a predetermined frequency for a predetermined period of time or more. means for transmitting a transmission radio wave consisting of a paging signal and a modulated transmission data signal obtained by modulating the carrier signal with a signal containing transmission data following the paging signal, the slave station having: resonating with the frequency; an LC resonant circuit; a means for determining that the level of a received signal of the transmitted radio wave in the resonant circuit has been established at a predetermined value or higher; and based on this determination, a Q value of the LC resonant circuit is set to a predetermined value. Applicable damping resistance to reduce below
means for inserting and connecting into the LC resonant circuit; and means for activating the means for amplifying the received signal in the LC resonant circuit and reading the transmitted data from the master station along with the inserting connection. A wireless data reception system for a mobile station, characterized in that: