JPH01316030A - Carrier detection system for radio communication system - Google Patents

Abstract

PURPOSE:To attain accurate discrimination of the presence of carrier independently of the quantity of environmental noise by comparing the 1st output of an IF filter through which a carrier frequency passes with the 2nd output of an IF filter through which the carrier frequency cannot pass so as to detect the carrier. CONSTITUTION:Since the spectrum (r) of environmental noise is spread flat wider than the carrier spectrum (s) and distributed flat, the level of monitor signals, Sa, Sb obtained from the IF signal extracted from IF filters 2e, 2i through reception signal intensity monitor circuits 2g, 2j is nearly equal to each other independently of the quantity of the noise level in the absence of carrier, a discrimination section 4 discriminates it to be the absence of carrier thereby enabling the transmission of a transmission section 1. In the presence of a carrier, the level of the signal Sa of the circuit 2g is increased and when a difference between the level of the signal Sa and the level of the signal Sb is more than a prescribed quantity X of over, the discrimination section 4 discriminates the presence of carrier to output a transmission control signal C thereby controlling the transmission section 1 not to be in operation.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a carrier detection method for a wireless communication system. FIG. 5 shows a wireless communication system that transmits data D, etc. between...

In the illustrated wireless communication system, each wireless phone A1
・・・The same frequency f so that transmission and reception can be carried out freely between
There are two ways to communicate using a carrier consisting of R.

In such a system, multiple radio devices A,...
Since simultaneous transmission from the transmitting section 1 will cause interference, the presence or absence of a carrier within the reception band of the receiving section 2 is detected in advance using the circuit configuration shown in FIG. Therefore, the transmission δ can be performed only when it is determined that the carrier does not exist. In this circuit, a reception signal extracted from the reception section 2 as a monitor signal S of the reception section 2 with respect to a set level L corresponding to a constant reception voltage (or reception electric field) set at the determination level setting section 3 for carrier detection. As shown in FIG. 7(a), the determination unit 4 compares whether the level of the carrier is large or small to determine the presence or absence of carriers.

[Problems to be Solved by the Invention] In addition, in the forward carrier detection, if the level of environmental noise is high, such as when the noise source 5 of a personal thin fuser or motor is nearby, the monitor signal S may fall within the receiving band of the receiving section 2. , the level of this monitor signal S exceeds the set level L as shown in FIG. 7(b) due to the noise signal.

As a result, it is determined that there is a carrier even though there is no carrier, and the opportunity for communication is lost because the control is performed so that the transmission does not occur even though there is no fear of interference in □. It had the disadvantage that it would attract insects.

The present invention has been made in view of the above-mentioned problems, and its purpose is to enable accurate carrier detection and judgment even when the level of environmental noise around the radio is large, thereby eliminating missed opportunities for communication. An object of the present invention is to provide a carrier detection method for a wireless communication system that can prevent such problems.

[Means for Solving the Problems 1] The present invention performs communication between a plurality of non-#i boards equipped with transmitting/receiving sections using a common carrier, and detects the presence of a carrier prior to transmission to detect the presence of the carrier. In a wireless communication system, in order to prevent interference, do not transmit.In a wireless communication system, the receiving section uses a >4'-hetero gain reception method, and the first output of an IF filter that allows the carrier frequency to pass, and the carrier frequency The signal is compared with the second output of the J11F filter through which the signal cannot pass, and when the first output becomes larger than the second output by a predetermined amount or more, it is determined that carriers are present.

[Function] Since the present invention has the above-described configuration, the output of the IF filter that passes the carrier frequency even if the level of environmental noise is large, and the output of the IF filter that does not pass the carrier frequency. The relative relationship does not change regardless of the magnitude of environmental noise in the absence of carriers, and therefore the presence or absence of carriers can be accurately determined without being affected by environmental noise.

[Example 1] Fig. 1 shows the circuit configuration of the radio device A of the example, in which the receiving section 2 uses a support bar heterogain detection method, and includes an RFm width circuit for amplifying the received signal. 2a, the local oscillation circuit 2''b, the received signal amplified by the RF amplifier circuit 2a, and the local oscillation frequency fL from the local oscillation circuit 2b.
an IF amplifier circuit 2d that amplifies the intermediate frequency extracted from the mixer 2c, a first IF filter 2e with a center frequency of fi, and r A received signal strength monitor circuit 2g outputs the received IF signal as a monitor multi-signal Sa, a demodulation circuit 2f demodulates the transmitted signal from the IFi signal output from the IF filter 2e, and reproduces data D from the a-modulated transmitted signal. A data reproducing circuit 211 that sets the center frequency to fi+Δ
The second □■F filter 21 with f and the engineering F filter 2
1, and a received signal strength monitor circuit 2j that outputs the signal ``F(l!'' extracted from 1) as the monitor signal sb.

The determining unit 4 is for determining the presence of a carrier by comparing the output level of the received signal strength monitor circuit 2g and the output level of the received signal strength monitor circuit 2j. The level is predetermined 1 from the level of the monitor signal sb of the received signal strength monitor circuit 2j.
When the value is greater than or equal to x, it is determined that a carrier is present, and a transmission control signal C is output that suppresses the transmission operation of the transmitter 1.

Next, let us explain the operation of this embodiment.

First, in the superheterodyne reception system, the reception center frequency is determined by the local oscillation frequency and the center frequency of the F filter. Therefore, if the IF filter 2e whose center frequency is fi and the F filter 21 for fi+8f are used as in this embodiment, each reception center frequency will be fL, where fL is the lower local oscillation frequency. +'f + 'gfL+ f
It becomes i+Δf. If the former frequency fL+fi is set to the frequency fR used as a carrier in the wireless communication system using this embodiment, the latter will receive a frequency higher than that by Δf.In this embodiment, This Δf is set to approximately 172 to 1 of the reception band (determined by the rF filter band), and the reception band (determined by the rF filter band) of the IF filters 2e and 2i is
By setting the widths of (a) and (b) to be the same, the relationship shown in FIG. 2 is obtained.

Since the spectrum of the environmental noise (c) is wider and more flatly distributed than the spectrum of the carrier (d), when no carrier exists, the spectrum of the environmental noise is as shown in Figure 3(a). Even if the level is small or
), the received signal strength monitor circuit 2g+2J from the IF multiplied signals extracted from the IF filters 2e and 2i.
The levels of the monitor signals Sa and Sb obtained through
transmission operation is possible. When there is a carrier, the level of the monitor signal Sa of the received signal strength monitor circuit 2g increases, and the difference between the level of this monitor signal Sa and the level of the monitor signal sb of the received signal strength ♀ monitor circuit 2j becomes a predetermined value f! When the value exceeds f, In this way, in this embodiment, the first IF filter 2e and the second IF filter 21
Since carrier detection is performed based on the relative relationship between the monitor signals Sa and Sb respectively obtained through the above, it is possible to accurately determine the presence or absence of a carrier regardless of the level of environmental noise.

FIG. 4 shows another embodiment of the present invention, in which the local oscillation frequency of the local oscillation circuit 2b is switched between k and rL+Δr under the control of the oscillation frequency control circuit 2.
The reception center frequency is rL+fi, corresponding to each local oscillation frequency, by the IF filter 2e whose center frequency is fi.
r, -+-fi+Δf, and similarly to the embodiment of FIG. 1, fL+fi=carrier frequency fR.

Further, the A/D conversion circuit 21 digitally converts the monitor signals Sa and Sb corresponding to the respective reception center frequencies obtained through the IF multiplied signal received signal strength monitor circuit 2g obtained by the IF filter 2e.

Further, in accordance with the switching control of the oscillation station and one wave number control circuit 2, the determination unit 4 temporarily holds the digital value of the monitor signal Sa that was A/D converted before switching, and uses this digital value and the A/D converted value after switching. The digital value of the D-converted monitor signal Sb is compared, and when the difference is greater than a predetermined amount, it is determined that a carrier is present, and the transmitter 1 is controlled in the same manner as the embodiment in FIG.

That is, in this embodiment, instead of using only one IF filter, the local oscillation frequency is switched to obtain IFM signals with different reception center frequencies, similar to the embodiment of FIG.

In each of the above embodiments, two reception center frequencies are set, but even if a configuration is adopted in which multiple carrier frequencies are set in addition to the reception frequency, for example, fR + Δr, "8 - Δf", the above Of course, the same effects as in each embodiment can be obtained.

[Effects of the Invention] The present invention provides a wireless communication system in which a superheterodyne reception method is used in the receiving section to provide a first output of an IF filter through which a carrier frequency can pass, and a second output of an IF filter through which a carrier frequency cannot pass. Compare with the output of
Since it is determined that a carrier is present when the first output becomes larger than the second output by a predetermined amount, the output of the IF filter that passes the carrier frequency even if the level of environmental noise becomes large, and the carrier frequency are determined to be present. IF that does not allow frequencies to pass through
The relative relationship with the output of the filter does not change in the absence of carriers regardless of the magnitude of environmental noise, and therefore the presence or absence of carriers can be accurately determined without being affected by environmental noise.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a radio device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the receiving frequency and receiving band characteristics of the same as above, tI & 3
4 is a circuit configuration diagram of another embodiment of the present invention, FIG. 5 is an overall configuration diagram of a wireless system, and FIG.
The figure is a circuit diagram of a conventional radio device, and FIG. 7 is an explanatory diagram of the same operation. 1 is a transmitting section, 2 is a receiving section, 4 is a determining section, 2e, 21 is an I
F filter, 2g+2j is received signal strength monitor circuit, S
a and Sb are monitor signals. Agent Patent Attorney Ishi 1) Chief Shichiko II Ward Deaf Scold I0 Ku ~ Buse 1. 1 11n+ to the wind ~ ° Explosive t>-view'=> Mi+l, +4! 2 gu
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l mouth, F rli, Hl 5th? Voluntary writing of procedural amendments)

Claims (1)

[Claims] (1) In addition to communicating using a common carrier between multiple radio devices equipped with transmitting and receiving sections, the presence of a carrier is detected prior to transmission, and when a carrier is present, no transmission is performed to prevent interference. In a wireless communication system, a superheterodyne reception method is used in the receiving section, and the first output of an IF filter that allows the carrier frequency to pass through is compared with the second output of the IF filter that does not allow the carrier frequency to pass. A carrier detection method for a wireless communication system, characterized in that it is determined that a carrier is present when the output of the second output becomes greater than a predetermined amount compared to the second output.