JPH0282731A - Radio communication equipment - Google Patents

Abstract

PURPOSE:To prevent the malfunction in a carrier sensing and to reduce energy consumption by transmitting the data of a low transmission rate prior to transmission data and executing the carrier detection through a filler having a pass band applied approximately only to the data of a low transmission rate with a receiver. CONSTITUTION:At the transmission, the data of the transmission rate lower than it prior to the data to be transmitted are transmitted. At a receiver, the cut-off frequency of a low pass filter(LPF) 26 at the front step of a carrier detecting circuit 7b is set to the low frequency approximately suitable for the passing of the low transmission rate data from the transmitter. Consequently, even when the prior transmission rate data passes through an LPF 26 and the presence/absence is detected, the level reduction hardly occurs, in addition, since most of noises is cut, the output of the LPF 26 becomes the waveform corresponding to only the low transmission rate data approximately. Thus, the malfunction in the carrier sensing does not occur and the energy consumption can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wireless communication device that transmits and receives digital data using radio waves, light, etc. The present invention relates to a wireless communication device that is an improved carrier sense method.

[Conventional technology]

Receivers for wireless paging systems, systems, etc. need to be portable, so they are required to operate on batteries.

Therefore, low power consumption is one of the most important performance requirements for a receiver. A conventionally used method for reducing power consumption is battery saving technology using carrier sense.

Such a conventional device will be explained with reference to a block diagram of a receiver of a conventional wireless paging system shown in FIG.

The receiver has a first block 20 that is always powered on, and a second block 21 that is powered on only when a carrier is detected.
It is divided into two parts.

The first block 20 includes an antenna 1 that receives radio waves (for example, 400 MHz band) modulated by digital data from a transmitter, an AGCRF amplifier 2 that voltage-amplifies the received radio waves, and a frequency converter (for example, 455-MHz band) that converts the amplified received signal.
mixer 3 and local oscillator 4
, a bandpass filter (BPF) 5 that passes only the required band from the frequency-converted signal, an IF amplifier (IFAMP) 6 that amplifies the BPF output, a carrier detection circuit 7 that detects the presence or absence of a received signal from the IFAMP output, and a carrier detection output. Monostable multi-bi break 8 with trigger input
, a switch 9 controlled by a monostable multivibrator output, and a battery 10 that supplies power to each of the above components and also supplies power to the second block 19 via the switch 9. When the signal is transmitted from the transmitter, the first block 20 sends an IF multiplied signal to the second block 21, and also outputs a control signal for a predetermined time from the carrier detection circuit 7 to the switch 9 via the monostable multivibrator 8. Then, the switch 9 is turned on, and the second block 21 is turned on. That is, the second block 21 is activated only when a signal is transmitted.

Next, the configuration and operation of the second block 21 will be explained. In this second block 21, the demodulation circuit 11
The modulation method (for example, FSKS) on the transmitting side is
A baseband signal of digital data is extracted using a demodulation method compatible with PSK, ASK, etc.). This demodulated baseband signal is filtered through a low-pass filter (
The signal is input to the comparator 13 via the LPF) 12 and converted to the TTL level. This level-converted baseband signal is reproduced into digital data by the decoding circuit 14 and input to the decoding circuit 15. The decoding circuit 15 determines whether it is the own device that is being called based on the digital data, and if it is the own device, outputs a control signal to the buzzer drive circuit 16 to make the buzzer 17 sound, and also reads the decoded digital data. If the message text is included in the message text, the message text is sent to the display drive circuit 18 and the text is displayed on the display device 19.

As described above, the paging reception operation is completed, but the switch 9 is turned off after a predetermined time has elapsed after the message is displayed, and the power of the second block 21 is turned off.

In this way, in paging, the waiting time is extremely long compared to the communication time, so only the part (first block 20) necessary for carrier sensing is always energized.
Power is supplied to the next stage (second block 21) only when a carrier sense signal is obtained, thereby reducing power consumption.

In addition to the above-mentioned method, there is also a method in which carrier sensing is performed after demodulation, as shown in the block diagram of FIG.

FIG. 5 shows a circuit commonly used in the carrier detection circuit 7, 7a of a receiver such as that shown in FIG. 3 or 4. In FIG.

As shown in the figure, it is determined whether the level of the input signal Vin (the IF multiplied signal is the demodulated output signal) exceeds a predetermined level by comparing it with the threshold level vth, and if it exceeds the level, the control signal VO is The comparator 24 outputting to the vibrator 8 constitutes the basic part of the carrier detection circuits 7 and 7a.

[Problem that the invention seeks to solve]

In such a conventional carrier sense method, the carrier/noise ratio (C/N ratio) of the received signal is low due to poor reception conditions.
If the signal is bad, the gain of the AGCRF amplifier 2 becomes high, and as a result, the IF multiplied signal noise level or the noise level of the demodulated output signal increases. On the other hand, the carrier detection circuits 7 and 7a have an input level Vin as shown in FIG.
Threshold level v
Since the judgment is made by comparing with
output frequently. Therefore, the output of the monostable multivibrator is almost always at the H level, and all the blocks are constantly in operation, resulting in a significant increase in battery consumption.

Therefore, an object of the present invention is to provide a wireless communication device that does not cause carrier sense malfunction even when the C/N ratio of a received signal is poor and can effectively reduce power consumption.

[Means for solving problems]

The present invention provides a wireless communication device for transmitting and receiving digital data, in which a transmitter has means for transmitting preceding low transmission rate data at a transmission rate lower than the transmission rate of the digital data, in advance of the digital data, and a receiver further comprising a carrier sense means for detecting the presence or absence of the preceding low transmission rate data through a filter having a passband approximately matching only the transmission rate of the preceding low transmission rate data to determine whether transmission is being performed. It is characterized by

[For production]

In transmission, data at a lower transmission rate is transmitted before the data to be transmitted. When this preceding low transmission rate data is received by a receiver, its presence or absence is detected through a filter having a pass band that approximately matches only the low transmission rate. Therefore, when passing through this filter, the preceding low transmission rate data is detected without much attenuation, but noise etc. are cut by the filter and do not affect carrier detection. Therefore, even when the C/N ratio is poor, accurate carrier detection is performed and no malfunction occurs.

〔Example〕

FIG. 1 shows a block diagram of a receiver according to an embodiment of the present invention, and FIG. 2(a) shows an example of a transmitted signal.

In the transmission signal shown in Figure 2(a), a low transmission rate signal (in this example, a low transmission rate signal of 100b/s, which is one-hundredth of the data transmission rate of 10kb/s) precedes the data to be sent. 1 bit of data (H level) is sent.

The receiver is divided into two parts: a first block 24 which is in operation by constantly being supplied with power from a battery (10), and a second block 25 which is powered on and operates only when a carrier is detected. The first block 24 has an antenna 1, an AGCRF amplifier 2, a mixer 3, a local oscillator 4, a BPF 5, an IFAMP 6, and a demodulation circuit 11, and is configured to perform carrier sensing based on the demodulated output. has been done. That is, the demodulated output is applied to the carrier detection circuit 7b via the LPF 26.

The carrier detection circuit 7b has a configuration as shown in FIG. 5, receives the output of the LPF 26 as an input signal V1n in a comparator, compares it with a predetermined threshold value Vth, and controls when the threshold value Vth is exceeded. The signal vO is output to the monostable multivibrator 8 as a trigger. and,
When the switch 9 is turned on by the output of the monostable multi-bi break 8, the second block 25 is powered on and operates.

The second block 25 includes an LPF 12 having the same configuration as the conventional device;
It is composed of a comparator 13, a decoding circuit 14, a decoding circuit 15, a buzzer drive circuit 16, a buzzer 17, a display drive circuit 18, and a display 19.

The feature of this receiver is that the cutoff frequency of the LPF 26 at the front stage of the carrier detection circuit 7b is inserted at a low frequency suitable only for passing low transmission rate data from the transmitter, for example, before the decoding circuit 14. This point is set to 1/100 of the cutoff frequency of the LPF 12.

Next, the operation will be explained with reference to FIG.

As mentioned above, the preceding transmission rate data, which is 1/100th the rate of the transmission data, is an LP with a low cutoff frequency.
There is almost no level drop when the signal passes through the F26, but most of the noise is cut out, so the output of the LPF 26 has a waveform that corresponds almost exclusively to low transmission rate data.

On the other hand, the output of the LPF 12 inserted before the decoding circuit 14 has a waveform containing noise as shown in FIG. 2(b). The waveform shown in FIG. 2(b) is the same as the waveform of the signal used for carrier detection in the conventional device, and the noise wave peak value is due to the fact that the cutoff frequency of the LPF 12 is 100 times that of the LPF 26 for carrier detection. From, 31og21
00-20 (dB)t, that is, the level is 10 times higher. Conversely, the noise contained in the signal input to the carrier detection circuit 7b (FIG. 2(C)) is one-tenth that of the decoding LPF output j. In other words, the carrier detection capability is ten times greater than that of the conventional method.

Therefore, the output of the carrier detection circuit 7 (control signal VO) contains almost no noise and has a waveform that faithfully corresponds to the low transmission rate data, as shown in FIG. 2(d). In response to this control signal, the monostable multi-by-break 8 turns on the switch 9 for a predetermined period of time, as shown in FIG. 2(e), and operates the second block 25. The operation of this second block 25 is similar to that of the conventional device.

Note that the present invention is not limited to the above embodiments,
Many variations are possible. For example, in the above embodiment, the cutoff frequency of the carrier detection LPF is set to 1/100 of that of the decoding LPF, but it is of course possible to set it higher or lower depending on various conditions.

〔Effect of the invention〕

As explained above, according to the present invention, low transmission rate data is transmitted from the transmitter prior to transmission data, and the receiver uses a filter having a pass band that is approximately adapted only to low transmission rate data. Since carrier detection is performed throughout, carrier sense malfunctions due to the influence of noise almost never occur even when the reception condition is poor and the C/N ratio is not sufficiently counted. It is possible to reduce the

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a receiver according to an embodiment of the present invention, and FIG. 2 is a block diagram of a receiver according to an embodiment of the present invention. ~(e)) Waveform diagrams, Figures 3 and 4 are block diagrams of a conventional receiver, Figure 5 is a basic circuit diagram of a carrier detection circuit, and Figure 6 is an output signal of each part of a conventional receiver. FIG. 7b...Carrier detection circuit, 8...Monostable multi-bi break, 9...Switch, 10...Battery, 11
... demodulation circuit, 12 ... low-pass filter for decoding,
14...Decoding circuit, 24...First block, 25...
...Second block, 26...Low pass filter for decoding.

Claims (1)

[Claims] 1. In a wireless communication device that transmits and receives digital data, the transmitter includes means for transmitting preceding low transmission rate data at a transmission rate lower than the transmission rate of the digital data, preceding the digital data. Then, the receiver detects the presence or absence of the preceding low transmission rate data through a filter having a passband that approximately matches only the transmission rate of the preceding low transmission rate data, and determines whether or not transmission is occurring. A wireless communication device comprising: means. 2. The receiver has a first part including the carrier sensing means and a second part not including the carrier sensing means, the first part being in a constantly active state, and the second part including the carrier sensing means. 1. A wireless communication device, wherein the wireless communication device is activated for a predetermined period of time only when the preceding low transmission rate data is detected.