JPH04216226A - Received signal detector - Google Patents

Abstract

PURPOSE:To secure a communication enable area matching the ability of reception by detecting the arrival of radio waves from a communicating party station on reception standby with a direct current voltage V2 lower than a direct current voltage V1 corresponding to a legal reception level as a threshold value. CONSTITUTION:A received intermediate frequency signal is converted to a direct current voltage by a rectifier integration circuit 11 and inputted to first and second voltage comparators 12 and 13 later. The direct current voltage V1 corresponding to the legislated reception level is inputted to the first voltage comparator 12 as the threshold value and therefore, a carrier sense function is presented. The direct current voltage V2 (V2<V1) corresponding to the reception level when a demodulation S/N is a reference value is inputted to the second voltage comparator 13 as the threshold value and therefore, the arrival of radio waves from the communicating party station on reception standby is judged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a received signal detection device used in a local radio station, a specific low power radio station, or the like.

0002

[Prior Art] Prior to transmission, in-plant radio stations and specified low-power radio stations are required by law to have a carrier sense function that prevents transmission if a receiving antenna input voltage exceeding a certain value is detected. There is.

[0003] In order to realize this function, a received signal detection device shown in FIG. 4 has conventionally been used. This inputs the received intermediate frequency signal (hereinafter referred to as the received IF signal) to the rectifying and integrating circuit 1, converts it into a DC voltage corresponding to the received signal level, and converts the DC voltage to the inverting input terminal of the voltage comparator 2 ( −)
is supplied to. A DC voltage is input as a threshold value from a reference voltage generator 3 to a non-inverting input terminal (+) of this voltage comparator 2.

The voltage comparator 2 determines whether the input DC voltage exceeds a threshold value, and uses the determination output to drive a microprocessor 4 and a light emitting diode (hereinafter referred to as LED) 5 to light up. It is supplied to circuit 6. When a high level signal is input from the voltage comparator 2, the microprocessor 4 determines that the DC voltage is below the threshold value and permits transmission, and when a low level signal is input, the microprocessor 4 determines that the DC voltage is below the threshold. The drive circuit 6 determines that the voltage exceeds the threshold value and prohibits transmission, and the drive circuit 6 lights up the LED 5 when a high level signal is input from the voltage comparator 2, and also lights up the LED 5 when a low level signal is input. When is being input, the LED 5 is turned off.

The microprocessor 4 also has a voltage comparator 2.
The arrival of a received signal from the communication partner station is also determined based on the determination output from the communication partner station, and the LED 5 is also used to display the communicable area in that case.

[0006]

[Problem to be Solved by the Invention] However, in this conventional device, there is only one threshold value for determining the received signal level, so if this threshold value is set to a legal level, signals below that level will be Since the signal cannot be detected, the receiving function does not operate even though the device has the ability to receive signals weaker than the legal level, resulting in a problem in that the communicable area is narrowed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a received signal detection device that is equipped with a carrier sense function during transmission and can secure a communicable area commensurate with the reception capability. Further, the present invention aims to provide a received signal detection device that can notify that a communicable area has been secured, taking into account a reception level fluctuation margin.

[0008]

[Means for Solving the Problems] The present invention provides DC voltage output means for outputting a DC voltage corresponding to a received signal level;
A first voltage comparator receives a DC voltage V1 corresponding to the legal reception level as a threshold, and determines whether the DC voltage from the DC voltage output means exceeds the threshold; The DC voltage V2 (V2 < V1) corresponding to the reception level when the N ratio becomes the reference value is input as a threshold value, and it is determined whether the DC voltage from the DC voltage output means exceeds the threshold value. The output of the second voltage comparator and each voltage comparator is taken in, and the output of the first voltage comparator is used to determine the detection of radio waves from other stations immediately before transmission, and the output of the second voltage comparator is used to determine the detection of radio waves from other stations immediately before transmission. A determination means is provided for determining the arrival of radio waves from the communication partner station.

Further, the present invention further provides that the DC voltage V3 (V2 < V3 < V1) corresponding to the reception level when the demodulated S/N ratio becomes a certain level larger than the reference value is input as a threshold value, and the DC voltage A third voltage comparator for determining whether the DC voltage from the output means exceeds the threshold value and an indicator responsive to the output of the third voltage comparator are provided.

0010

[Operation] In the present invention having such a configuration, when the first voltage comparator determines that the DC voltage from the DC voltage output means exceeds the threshold value V1 immediately before transmission, transmission from this side is prohibited, Further, when it is determined that the DC voltage from the DC voltage output means is below the threshold value, transmission from this side is permitted.

Further, when the second voltage comparator determines that the DC voltage from the DC voltage output means exceeds the threshold value V2 during reception standby, the arrival of radio waves from the communication partner station is detected. Further, in this state, when the third voltage comparator determines that the DC voltage from the DC voltage output means exceeds the threshold value V3, the display operates to notify that the other station is within a communicable distance.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the received IF signal is input to a rectifier/integrator circuit 11 to convert it into a DC voltage corresponding to the received signal level, and the DC voltage is sent to a first, second, and third voltage comparator 12. , 13, and 14, respectively.

The non-inverting input terminal (+) of the first voltage comparator 12 receives a DC voltage V1 corresponding to the legal reception level from the first reference voltage generator 15 as a threshold value. The non-inverting input terminal (+) of the second voltage comparator 13 receives a signal from the second reference voltage generator 16 equipped with a variable resistor 16a, which corresponds to the reception level when the demodulated S/N ratio becomes the reference value. The DC voltage V2 (V2 < V1) is input as the threshold value. The non-inverting input terminal (+) of the third voltage comparator 14 is supplied with a demodulated S/N ratio from a third reference voltage generator 17 including a variable resistor 17a and a fixed resistor 17b to a constant level higher than the reference value. DC voltage V3 corresponding to the reception level when it increases (V2<V3
<V1) is input as the threshold value.

The second and third reference voltage generators 16,1
The variable resistors 7 are variably controlled in conjunction with each other. The fixed resistor 17b connects the DC voltage V3 from the third reference voltage generator 17 to the second reference voltage generator 1.
This resistor is used to set the voltage to be higher than the DC voltage V2 from V2 by a certain level to allow for a fluctuation margin in the reception level.

The first voltage comparator 12 determines whether the DC voltage input from the rectifier/integrator circuit 11 exceeds a threshold value, that is, the DC voltage V1, and supplies the determination output to the microprocessor 18. are doing.

The second voltage comparator 13 determines whether the DC voltage input from the rectifier/integrator circuit 11 exceeds a threshold value, that is, the DC voltage V2, and sends the determination output to the microprocessor 18. supplying.

The microprocessor 18 constitutes a determining means, and when a high level signal is input from the first voltage comparator 12 immediately before transmission, the input DC voltage is below a threshold value. When a low-level signal is input, it is determined that the input DC voltage exceeds a threshold value and transmission is prohibited.

Furthermore, when the microprocessor 18 receives a low level signal from the second voltage comparator 13 during reception standby, it determines that the input DC voltage exceeds a threshold value, and selects the communication partner. It is designed to judge the arrival of radio waves from stations. At this time, receiving functions such as bit synchronization and data judgment are controlled.

The third voltage comparator 14 determines whether or not the DC voltage input from the rectifier/integrator circuit 11 exceeds a threshold value, that is, the DC voltage V3, and displays the determination output on an LED 19 as an indicator. Drive circuit 2 that drives the lighting
0. The drive circuit 20 controls the LED 19 to turn off when a high level signal is input from the third voltage comparator 14, and controls the LED 19 to turn on when a low level signal is input. .

The rectifying/integrating circuit 11, as shown in FIG. 2, for example, consists of a rectifying section composed of a capacitor 21, diodes 22, 23, and an integrating section composed of resistors 24, 25, and a capacitor 26.

For example, as shown in FIG. 3, the drive circuit 20 connects the LED 19 between the +V terminal and the ground via a PNP transistor 27, and connects the third LED to the base of the transistor 27 via a resistor 28. The output of the voltage comparator 14 is supplied. Note that a resistor 29 is connected between the emitter and base of the transistor 27. In this embodiment having such a configuration, the received reception IF signal is converted by the rectification/integration circuit 11 into a DC voltage corresponding to the reception signal level.

If this DC voltage exceeds the DC voltage V1 from the first reference voltage generator 15 immediately before transmission, the output of the first voltage comparator 12 becomes low level, so the microprocessor 18 It determines that the carrier sense level is detected and prohibits transmission. Further, this DC voltage is the DC voltage V1 from the first reference voltage generator 15.
If it is below, the output of the first voltage comparator 12 will be at a high level, so the microprocessor 18 will permit transmission.

Furthermore, if the DC voltage corresponding to the received signal level exceeds the DC voltage V2 from the second reference voltage generator 16 during reception standby, the output of the second voltage comparator 13 becomes low level. The microprocessor 18 determines the arrival of radio waves from the communication partner station and controls reception functions such as bit synchronization and data determination.

In this way, during reception standby, even if the received signal level does not reach the legal carrier sense level, reception is possible if it exceeds the DC voltage V2, ensuring a communicable area commensurate with the reception capability of the device. can do.

Furthermore, during reception standby, if the DC voltage corresponding to the received signal level exceeds the DC voltage V3 from the third reference voltage generator 17, the output of the third voltage comparator 14 becomes low level. The transistor 27 of the drive circuit 20 turns on and the LED 19 lights up. This lets you know that stable communication is possible with the communication partner station even if there is some reception noise. In other words, it is possible to notify that a communicable area has been secured in consideration of the reception level fluctuation margin.

Furthermore, second and third reference voltage generators 16,
17 is a DC voltage V2 by variable resistors 16a and 17a.
, V3 can be varied, so the DC voltage V2 can be adjusted according to changes in the reception noise level depending on the installation location of the wireless device.
, V3 level can be adjusted. That is, in a place where the reception noise level is high, the levels of the DC voltages V2 and V3 may be set high. Moreover, variable resistors 16a and 17a
are varied in conjunction with each other, so the DC voltages V2 and V
3 and is variable while maintaining a constant level difference and can be easily adjusted.

Note that in the above embodiment, the third voltage comparator 1
4 is provided, and when this comparator output becomes low level, L
Although the ED 19 is turned on to notify that a communicable area has been secured with a reception level fluctuation margin in mind, this circuit section may be omitted.

[0029]

As described in detail above, according to the present invention, it is possible to provide a received signal detection device that is equipped with a carrier sense function during transmission and can secure a communicable area commensurate with the reception capability. Further, according to the present invention,
Furthermore, it is possible to provide a received signal detection device that can notify that a communicable area has been secured, taking into account a reception level fluctuation margin.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a specific circuit diagram of a rectifying and integrating circuit in the same embodiment.

FIG. 3 is a specific circuit diagram of a drive circuit in the same embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

[Explanation of symbols]

11... Rectifying and integrating circuit (DC voltage output means), 12, 13
, 14... Voltage comparator, 15, 16, 17... Reference voltage generator, 18... Microprocessor (determination means), 19... Light emitting diode (indicator).

Claims (2)

[Claims] 1. DC voltage output means for outputting a DC voltage corresponding to a received signal level; a DC voltage V1 corresponding to a legal reception level is input as a threshold value; A first voltage comparator determines whether or not the threshold value is exceeded, and a DC voltage V2 (
V2 < V1) is input as a threshold, and a second voltage comparator determines whether the DC voltage from the DC voltage output means exceeds the threshold; and determination means for determining the detection of radio waves from another station immediately before transmission based on the output of the first voltage comparator, and determining the detection of the arrival of radio waves from the communication partner station during reception standby based on the output of the second voltage comparator. A received signal detection device characterized by: 2. A DC voltage output means for outputting a DC voltage corresponding to a received signal level, a DC voltage V1 corresponding to a legal reception level being input as a threshold value, and a DC voltage from the DC voltage output means outputting a DC voltage corresponding to the received signal level. A first voltage comparator determines whether or not the threshold value is exceeded, and a DC voltage V2 (
V2 < V1 ) is input as a threshold value, and a second voltage comparator determines whether or not the DC voltage from the DC voltage output means exceeds the threshold value, and a demodulation S/N ratio is set to a reference value. A DC voltage V3 (V2 < V3 < V1) corresponding to the reception level when the received level becomes a certain level higher than the DC voltage output means is input as a threshold value, and the DC voltage from the DC voltage output means exceeds the threshold value. A third voltage comparator that determines the voltage, and the outputs of the first and second voltage comparators are taken in, and the output of the first voltage comparator is used to determine the detection of radio waves from other stations immediately before transmission. A received signal detection device comprising: a determining means for determining whether to detect the arrival of a radio wave from a communication partner station during reception standby based on the output of the third voltage comparator; and a display responsive to the output of the third voltage comparator.