JP2778546B2 - Received signal attenuation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an attenuation control device, and more particularly to an attenuation control device for attenuating a received signal in a wireless communication device.

[0001]

2. Description of the Related Art Generally, an amplifier circuit is used in a radio to amplify a received signal and supply it to a demodulator. However, when a signal having a high signal level, that is, a signal having a strong electric field intensity is received, the signal is saturated by the nonlinearity of the transistor included in the amplifier circuit, and the operating point of the transistor moves. When the operating point of the transistor moves, the gain of the amplifier circuit for the desired wave included in the received signal decreases, and the receiving sensitivity of the desired wave deteriorates.

Therefore, in order to prevent the receiving sensitivity of a desired wave from deteriorating, an attenuating circuit for attenuating a received signal is provided in a stage preceding the amplifying circuit. The attenuation circuit attenuates the received signal, thereby weakening the electric field strength and preventing the gain of the amplifier circuit from decreasing.

FIG. 9 is a functional block diagram showing a conventional radio having the above-described attenuation circuit.

[0004] In FIG. 9, the wireless device includes an antenna 1, an attenuation circuit 2, an amplification circuit 3, a reception field strength detection circuit 4 and a demodulation circuit 6.

[0005] The attenuation circuit 2 attenuates the received signal received by the antenna 1. The amount of attenuation in the attenuation circuit 2 is determined by the output voltage value from the reception electric field strength detection circuit 4. The amplification circuit 3 amplifies the attenuated reception signal from the attenuation circuit 2 and outputs the amplified reception signal to the reception electric field strength detection circuit 4 and the demodulation circuit 6. The reception electric field strength detection circuit 4 outputs the electric field strength value of the reception signal,
, And outputs a DC voltage corresponding to the amplitude to the attenuation circuit 2.

FIG. 10 is a characteristic diagram showing an ideal relationship between an input voltage value to the amplifier circuit 3 and an output voltage value from the reception electric field strength detection circuit 4.

As shown in FIG. 10, the input voltage value to the amplifier circuit 3, that is, the electric field strength value of the received signal and the output voltage value from the received electric field strength detection circuit 4 have a direct proportional relationship, and Is strong, the output voltage value from the reception field strength detection and detection circuit 4 increases.

Since the amount of attenuation of the attenuation circuit 2 is set according to the output voltage value from the reception electric field strength detection circuit 4, the electric field intensity value of the reception signal becomes strong, and the reception electric field strength detection circuit 4
When the output voltage value from the input terminal increases, the amount of attenuation in the attenuation circuit 2 increases. Due to the increase in the attenuation, the electric field of the received signal having a strong electric field strength value is weakened, and a decrease in the gain in the amplifier circuit 3 is prevented.

[0009]

However, in the above-mentioned conventional wireless device, the relationship between the input voltage value to the amplifier circuit and the output voltage value from the detection circuit actually has a characteristic as shown in FIG. Instead, as shown in the characteristic diagram of FIG. 11, when the input voltage value to the amplifier circuit ranges from zero to A,
The output voltage value from the reception electric field strength detection circuit remains constant at B and does not become zero.

[0010] This is because even if the electric field intensity of the received signal becomes small, noise due to thermal noise is input to the received electric field intensity detection circuit via the amplifier circuit, and the received electric field intensity detection circuit outputs the electric field intensity value ( Amplitude) into a DC voltage and output from the attenuation circuit. Since the attenuation of the attenuation circuit is set by the DC voltage value from the reception electric field strength detection circuit at this time, even if the electric field intensity value of the reception signal is small, the attenuation amount in the attenuation circuit is equal to the electric field intensity value. On the other hand, it is set to be large, and the electric field strength value of the received signal is weakened more than necessary. Therefore, there is a problem that the receiving sensitivity is deteriorated.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a reception signal attenuation control device that improves the minimum operation sensitivity with respect to the signal level of a reception signal.

[0012]

In order to achieve the above-mentioned object, a reception signal attenuation control device according to the present invention detects an electric field intensity value of a received signal and outputs an electric field intensity signal indicating the detected electric field intensity value. Electric field intensity detecting means for outputting, an attenuating means for attenuating a received signal based on the amount of attenuation set by the magnitude of the electric field intensity value indicated by the electric field intensity signal, and a predetermined electric field intensity value indicated by the electric field intensity signal Control means for controlling the attenuation means so as to give an attenuation amount smaller than the attenuation amount set in the following cases.

Further, the attenuation smaller than the set attenuation may be set to substantially zero. When the electric field intensity value is larger than a predetermined value, a high-level signal is output to the control means, and the electrolytic intensity value is reduced. When the value is equal to or less than the predetermined value, a Schmitt trigger circuit that outputs a low-level signal, a switch that turns on when a high-level signal is input, and a switch that turns off when a low-level signal is input, and one end of the switch. And a resistor connected to the other end and grounded.

The control means supplies an electric field intensity signal to the attenuating means when the electric field intensity value is equal to or less than a predetermined value, and when the electric field intensity value is larger than the predetermined value, the control means supplies the electric field intensity signal to the attenuating means. The obtained signal is supplied to the attenuation means.

In the present invention, by employing the above-described configuration,
When the electric field strength value indicated by the electric field detection signal is equal to or less than a predetermined value by the control means, an electric field strength signal indicating zero electric field strength value is output. The attenuation is reduced, and the electric field strength value of the received signal is not unnecessarily weakened. Therefore, it is possible to improve the minimum operation sensitivity to the received signal level, that is, the electric field strength value of the received signal.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a functional block diagram of a reception signal attenuation control device according to one embodiment of the present invention.

Referring to FIG. 1, the present invention includes an antenna 1, an amplification circuit 3, a reception electric field strength detection circuit 4, a control circuit 5, and a demodulation circuit 6.

The received signal received via the antenna 1 is attenuated by the attenuator 2 and output to the amplifier 3.
The amount of attenuation of the attenuation circuit 2 is set according to the output voltage value from the reception electric field strength detection circuit 4.

The received signal attenuated by the attenuating circuit 2 is amplified by the amplifying circuit 3 and output to the received electric field strength detection circuit 4 and the demodulation circuit 6. The electric field strength value of the amplified reception signal, that is, the amplitude of the reception signal from the amplifier circuit 3 is converted into a DC voltage by the reception electric field strength detection circuit 4, and this DC voltage value is output to the control circuit 5.

A threshold value VTH is set in the control circuit 5, and when the voltage value from the reception electric field strength detection circuit 4 is lower than the threshold value VTH, an output voltage value to the attenuation circuit 2 is output to zero. When the threshold value is equal to or higher than the threshold value VTH, the voltage value from the reception electric field strength detection circuit 4 is output as it is.

FIG. 2 is a circuit diagram of the attenuation circuit shown in FIG.

In FIG. 2, the attenuation circuit 2 includes a diode 21 having an anode connected to a constant power supply terminal, and a diode 21.
A diode 22 having an anode connected to the cathode of the diode 22, a resistor 23 having one end connected to the cathode of the diode 21,
Is provided. The attenuation circuit 2 includes a transistor 24 having a collector terminal connected to the other end of the resistor 23, a base terminal connected to one end of the resistor 25, and an emitter terminal grounded.
And a resistor 2 whose other end is connected to the reception electric field strength detection circuit 4.
5 is provided.

In the attenuating circuit 2, the impedance of the transistor 24 changes in proportion to the magnitude of the DC voltage value from the receiving electric field strength detecting circuit 4, and the diode 21
And the current flowing through 22 changes. Since the impedance of the diodes 21 and 22 changes due to the change in the current value, the impedance of the attenuation circuit 2 changes.

Therefore, as the electric field strength of the received signal increases, the impedance of the attenuation circuit 2 increases,
When the electric field intensity value of the received signal decreases, the impedance of the attenuation circuit 2 decreases. Therefore, when the electric field intensity value of the reception signal which is the input voltage to the amplification circuit 3 is large, the attenuation in the attenuation circuit 4 increases, The electric field strength value of the received signal is weakened.

FIG. 3 is a circuit diagram of the control circuit 5 shown in FIG.

In FIG. 3, the control circuit 5 includes an attenuation circuit 2
, A switch 51 connected in series to the reception electric field strength detection circuit 4, a Schmitt trigger circuit 52 for controlling the switch 51 to be turned on / off by a DC voltage value from the reception electric field strength detection circuit 4, and a switch between the attenuation circuit 2 and the switch 51. And a resistor 53 that is connected to one end and the other end is grounded.

As shown in the characteristic diagram of FIG. 4, when the input voltage, that is, the voltage value from the reception electric field strength detection circuit 4 is from zero to the threshold value VTH, the Schmitt trigger circuit 52 has a low-level voltage value VL. And when the input voltage is higher than the threshold value VTH, the high-level voltage value VH
Is output. The threshold value VTH is set to, for example, the voltage B shown in FIG.

Next, the operation of the control circuit 5 will be described with reference to a characteristic diagram showing the relationship between the input voltage and the output voltage in the control circuit 5 of FIG.

The input voltage from the reception electric field strength detection circuit 4 is supplied to a switch 51 and a Schmitt trigger circuit 52. As shown in FIG. 4, the Schmitt trigger circuit 52 outputs a low-level voltage value VL when the input voltage is equal to or lower than the threshold value VTH, and outputs a high-level voltage value VH when the input voltage is higher than VTH. I do.

When the output of the Schmitt trigger circuit 52 is at VH, the switch 51 is turned on, and when it is at VL, it is turned off. Therefore, the Schmitt trigger circuit 5
When the input voltage value to 2 is higher than VTH, switch 5
1 is turned on, and the input voltage value is output to the attenuation circuit 2 as it is. The input voltage value at this time becomes a voltage value equal to the input voltage value to the control circuit 5, as shown in FIG.

On the other hand, when the voltage value from the reception electric field strength detection circuit 4 is lower than VTH, the switch 51 is turned off,
Since the attenuation circuit 2 and the ground are grounded via the resistor 53, the voltage value output to the attenuation circuit 2 becomes zero as shown in FIG.

FIG. 6 is a characteristic diagram showing the amount of attenuation with respect to the input voltage from the antenna 1 to the attenuation circuit 2.

In FIG. 6, the antenna 1 is connected to the attenuation circuit 2.
When the input voltage from is small, that is, when the input voltage is equal to or less than the voltage value D, the attenuation amount becomes a value close to zero, and the attenuation circuit 2
When the input voltage from the antenna 1 becomes larger than D,
The amount of attenuation increases rapidly. The input voltage value D is a voltage level that is not affected by thermal noise.

Next, another embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a characteristic diagram showing the relationship between the input voltage of the Schmitt trigger circuit 52 and the output voltage, and FIG. 8 is a characteristic diagram showing the relationship between the input voltage of the control circuit 5 and the output voltage.

In this embodiment, the threshold is set to VTHH when the input voltage is increasing, and the threshold is set to VTHL when the input voltage is decreasing.

The input / output characteristics of the control circuit 9 at this time are shown in FIG.
When the input voltage is in the process of increasing, the output voltage value is set to zero when the input voltage is equal to or lower than the threshold value VTHH, and when the input voltage is higher than the threshold value VTHH, the output voltage value is input. Make it equal to the voltage value.

On the other hand, when the input voltage is in the process of decreasing, when the input voltage is equal to or higher than the threshold value VTHL, the output voltage value is made equal to the input voltage value. The output voltage value is set to zero.

In this embodiment, since the input / output characteristics of the control circuit have hysteresis characteristics, when the input voltage to the control circuit 5 is near the threshold value, the output voltage immediately changes from zero to the input voltage value. Can be suppressed, and the characteristics of the loop circuit including the reception electric field strength detection circuit and the control circuit 5 can be stabilized.

[0040]

As described above, in the received signal attenuation control device according to the present invention, when the signal level of the received signal, that is, the electric field strength value is equal to or less than a predetermined value, for example, a value affected by thermal noise, Since the voltage value for controlling the attenuation of the attenuating circuit is configured to be zero, it is possible to solve the problem that the received signal is excessively attenuated due to thermal noise or the like when the received signal level is low. Operation sensitivity can be improved.

[Brief description of the drawings]

FIG. 1 is a mechanism block diagram of a reception signal attenuation control device of a wireless device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of the attenuation circuit shown in FIG.

FIG. 3 is a block diagram of a control circuit shown in FIG. 1;

FIG. 4 is a characteristic diagram showing input / output characteristics of the Schmitt trigger circuit shown in FIG. 2;

FIG. 5 is a characteristic diagram showing input / output characteristics of the control circuit shown in FIG. 1;

FIG. 6 is a characteristic diagram showing a relationship between an input voltage value from the antenna 1 to the attenuation circuit shown in FIG. 1 and an attenuation amount.

FIG. 7 is a characteristic diagram showing input / output characteristics of a Schmitt trigger circuit according to another embodiment of the present invention.

FIG. 8 is a characteristic diagram showing input / output characteristics of a control circuit according to another embodiment of the present invention.

FIG. 9 is a mechanism block diagram showing an example of a conventional reception signal attenuation control device.

FIG. 10 is a characteristic diagram showing an ideal relationship between an input voltage value to a conventional amplifier circuit and an output voltage value from a reception electric field strength detection circuit.

FIG. 11 is a characteristic diagram showing an actual relationship between an input voltage value to a conventional amplifier circuit and an output voltage value from a reception electric field strength detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Antenna 2 ... Attenuation circuit 3 ... Amplification circuit 4 ... Received electric field strength detection circuit 5 ... Control circuit 6 ... Demodulation circuit

Claims (5)

(57) [Claims] 1. An electric field intensity detecting means for detecting an electric field intensity value of a received signal and outputting an electric field intensity signal indicating the detected electric field intensity value, wherein the electric field intensity signal is set by an electric field intensity value indicated by the electric field intensity signal. and attenuation means for attenuating the received signal on the basis of the attenuation, to control the attenuating means to provide the attenuation is substantially zero when the electric field intensity value is less than the predetermined value indicated by the electric field strength signal Control means , wherein the control means determines that the electric field strength value is greater than the predetermined value.
To output a high-level signal, and the electrolytic strength value is
When the value is less than the predetermined value, a low level signal is output.
The Schmitt trigger circuit for output and the high-level signal are turned on when the high-level signal is input.
Switch that is turned off when a low-level signal is input, and a resistor having one end connected to the switch and the other end grounded.
And when the electric field strength value is equal to or less than the predetermined value,
Supplying the electric field intensity signal to the attenuating means;
When the value is greater than the predetermined value,
Received signal attenuation controller radios characterized that you a signal supplied to the damping means. 2. A received signal attenuation control device of a wireless device as recited in claim 1 wherein the input-output characteristic of the Schmitt trigger circuit and having a hysteresis. 3. An electric field strength value of a received signal is detected.
Electric field intensity that outputs the electric field intensity signal indicating the changed electric field intensity value
Detection means and the magnitude of the electric field intensity value indicated by the electric field intensity signal.
Attenuating the received signal based on a specified attenuation
Means, and an electric field intensity value indicated by the electric field intensity signal is a predetermined value.
When the amount of attenuation is smaller than the set attenuation,
Control means for controlling the attenuating means so as to provide a first diode having a cathode connected to a power supply; a second diode having a cathode connected to the anode of the first diode; A first resistor having one end connected to the anode of the second diode, a transistor having a collector terminal connected to the other end of the resistor, an emitter terminal grounded, and one end connected to the base of the transistor received signal attenuation controller radios, characterized in that it comprises a second resistor for supplying the base of said transistor the field strength signal by Rukoto. Wherein said field strength detecting means, the reception signal attenuation control apparatus according to claim 1 or 3, wherein the outputting the electric field strength signal by the amplitude DC conversion of a received signal. 5. The method according to claim 1, wherein an electric field strength value of the received signal is detected.
Electric field intensity that outputs the electric field intensity signal indicating the changed electric field intensity value
Detection means and the magnitude of the electric field intensity value indicated by the electric field intensity signal.
Attenuating the received signal based on a specified attenuation
Means, and an electric field intensity value indicated by the electric field intensity signal is a predetermined value.
The attenuation so as to give almost zero attenuation when
Control means for controlling the means, when the electric field strength value is greater than the predetermined value
Outputs a first signal, and the electrolytic strength value is set to the predetermined value.
Circuit for outputting a second signal when the value is equal to or less than the determined value.
Means for turning on when the first signal is input, and for turning on the second signal.
Switch means that is turned off when a signal is input, one end is connected to the switch means, and the other end is grounded.
And when the electric field strength value is equal to or less than the predetermined value,
Supplying the electric field intensity signal to the attenuating means;
When the value is greater than the predetermined value,
A receiving signal attenuation control device for a wireless device, wherein the received signal is supplied to the attenuation means .