JPH04354210A - Reception circuit for communication equipment - Google Patents

Abstract

PURPOSE:To provide the reception circuit for the communication equipment in which a proper impedance is kept even in a strong electric field so as to prevent the deterioration in the sensitivity suppression. CONSTITUTION:When the electric field strength of a radio wave received by an antenna 6 in the strong electric field is high, a level of a DC signal outputted from a final stage demodulator 5 of a reception circuit is detected by a comparator means and when the detection level is higher than the setting level of the comparison means, a signal to turn on a relay is outputted to a relay 11 and the relay 11 is turn on and a reception signal filtered by a reception radio wave passes through an attenuation means and the reception signal of the level attenuated by the attenuation means is inputted to an amplifier 2 to suppress the power consumption at the amplifier 2 and a mixer 4 at the post-stage thereby keeping a proper impedance and preventing deterioration in the sensitivity suppression.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving circuit for a communication device.

[0002] This receiving circuit is used in a communication device such as a mobile communication terminal radio device. A mobile communication terminal radio device communicates while moving within the radio wave zone of a base station connected to a switching control station, and the reception level changes depending on the electric field level.

[0003] For this reason, in a strong electric field, the input level increases and the performance of the wireless device deteriorates, so there is a need for a receiving circuit that can stably operate the wireless device even in a strong electric field. There is.

0004

2. Description of the Related Art FIG. 4 shows a block diagram of a conventional receiving circuit used in a communication device such as a mobile communication terminal radio device, and will be explained below.

The receiving circuit shown in this figure includes a transmitter/receiver duplexer 1
, an amplifier 2 , an interstage duplexer 3 , a mixer 4 , and a demodulator 5 .

[0006] The transmitting/receiving duplexer 1 separates transmitting and receiving waves, and filters radio waves from a base station (not shown) received by the antenna 6, and sends the received signals S1 to the amplifier 2.
At the same time, the transmitted signal from the transmitter is filtered and transmitted from the antenna 6.

[0007] The amplifier 2 amplifies the received signal S1 and outputs it to the interstage duplexer 3. The interstage duplexer 3 outputs the amplified signal from the amplifier 2 to the mixer 4 , and also filters the local oscillation signal from the synthesizer section and outputs it to the mixer 4 .

[0008] The mixer 4 receives the signal from the interstage duplexer 3;
The difference in frequency from the local oscillation signal from the synthesizer section is taken and outputted to the demodulator 5 as a difference signal.

The demodulator 5 demodulates the difference signal and outputs it as a DC signal (RSSI) S2 to the control section. Then, the control section performs control for communication based on this DC signal S2.

0010

By the way, in the above-described receiving circuit, the level of the received signal S1 changes linearly in accordance with the electric field strength of the radio waves received by the antenna 6. This received signal S1 is directly input to the amplifier 2, and after being amplified by the amplifier 2, it is input to the mixer 4 via the interstage duplexer 3. Therefore, in a strong electric field, as shown in FIG. , the level of the received signal S1 increases, and the current consumption of the amplifier 2 and mixer 4 increases.

[0011] When the current consumption increases in this way, there is a problem in that the impedance shifts accordingly, and this shift in impedance causes deterioration in sensitivity suppression.

[0012] When such a problem arises, the performance of the wireless device using this receiving circuit deteriorates, resulting in the wireless device not operating stably.

The present invention has been made in view of these points, and it is possible to maintain an appropriate impedance even in a strong electric field, thereby preventing deterioration of sensitivity suppression from occurring. The purpose of the present invention is to provide a receiving circuit for a communication device that can perform the following functions.

[0014]

[Means for Solving the Problems] FIG. 1 shows a principle diagram of a receiving circuit according to the present invention. In the figure, reference numeral 1 denotes a duplexer that filters radio waves received by the antenna 6 and outputs a received signal S1 of a level corresponding to the field strength of the radio waves.

Reference numeral 2 denotes an amplifier, which amplifies the received signal S1 outputted from the duplexer 1 and outputs the amplified signal. 3
is an interstage duplexer that filters the signal output from the amplifier 2 and outputs the filtered signal.

A mixer 4 takes the frequency difference between the signal output from the interstage duplexer and the local oscillation signal from the synthesizer section, and outputs this as a difference signal.

A demodulator 5 demodulates the differential signal output from the mixer 4 and outputs it.

The 10 comparing means, 11 relays and 12 damping means are characteristic elements of the invention.

Comparison means 10 compares the level arbitrarily set to this means and the DC signal (RSS) output from demodulator 5.
I) It compares the level of S2 and outputs a signal S3 of a predetermined level according to the comparison result, and turns on when the level of DC signal S2 output from the demodulator 5 exceeds the set level. It operates so that the signal S3 at a predetermined level is outputted, and when the level of the DC signal (RSSI) S2 becomes below the set level, it enters the off state and the output level becomes approximately 0.

When the signal S3 outputted from the comparison means 10 is supplied, the relay 11 turns on and connects the duplexer 1 to the amplifier 2 via the attenuation means 12, so that the output level of the comparison means 10 becomes approximately 0. That is, when the signal S3 is no longer supplied, it is turned off and the duplexer 1 and amplifier 2 are connected.

The attenuating means 12 attenuates the level of the received signal S1 from the first filter by a desired amount when the relay 11 is turned on, and outputs the level.

[0022]

[Operation] If a communication device using the receiving circuit of the present invention described above is used in a strong electric field, the antenna 6 will receive radio waves with high electric field strength, and at this time, the duplexer A high-level received signal S1 is output from the amplifier 1 and input to the amplifier 2.

Then, the received signal S1 is amplified by an amplifier, outputted to a demodulator 5 via an interstage duplexer 3 and a mixer 4, and demodulated by the demodulator 5. The DC signal (RSSI) S2 outputted from the demodulator 5 has a high level based on the previous process, and if this level is higher than the set level of the comparison means 10, the comparison means 10 is turned on and the signal S3 is output.

When the signal S3 is output, the relay 11 is turned on, and the first filter 1 is connected to the amplifier 2 via the attenuation means 12.

[0025] As a result, the received signal S1 outputted from the duplexer 1 is input to the attenuation means 12 and its level is attenuated, and the received signal S1 at this attenuated level is input to the amplifier 2. .

Conventionally, if the amount of attenuation is determined so that the level of the received signal S1 input to the amplifier 2 is at a level that allows the receiving circuit to operate properly, the amplifier The level of the received signal input to the amplifier 2 increases, the current consumption of the amplifier 2 and the mixer 4 increases, and this increase eliminates impedance shifts and sensitivity suppression deterioration.

[0027] Furthermore, it is possible to stably operate a communication device such as a radio using this receiving circuit.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of a receiving circuit according to an embodiment of the present invention. In this figure, parts corresponding to those of the conventional example shown in FIG. 4 are given the same reference numerals, and their explanations will be omitted.

The receiving circuit of this embodiment is constructed by providing a comparator 10, a relay 11, and an attenuator 12 in addition to the components of the conventional circuit shown in FIG.

The comparator 10 is composed of an operational amplifier 13 and resistors 14, 15, and 16 having arbitrary resistance values.
The positive phase input terminal "+" is connected to the output terminal of the demodulator 5 through the resistor 15, and the positive phase input terminal "+" and the output terminal are connected through the resistor 16. has been done.

Further, this comparator 10 is provided with hysteresis to suppress the fluttering of the comparator 10 during operation and to ensure stable operation.

The operating point of this comparator 10 will be explained with reference to FIG. FIG. 3 is a diagram showing the relationship between the level of the received signal S1 and the voltage of the DC signal S2, and as the electric field strength of the radio waves received by the antenna 6 increases, the received signal S
1 becomes higher, and the voltage of the DC signal (RSSI) S2 increases linearly according to this level up to a certain level.

That is, since the comparator 10 is provided with hysteresis, as shown in FIG. , it turns on and outputs a signal S3 of an arbitrary level, and when the voltage of the DC signal S2 falls below a certain voltage value indicated by a dashed-dotted line 21, it turns off and stops the signal S3. . In other words, the level of the received signal S1 and the DC signal (RSSI)
It is configured to turn on/off in a linear portion with respect to the voltage of S2.

The relay 11 is turned on/off by a signal S3 from the comparator 10. This relay 11 normally connects the transmitter/receiver 1 and the amplifier 2 as shown by the solid line when in the off state, so that the reception signal S1 output from the transmitter/receiver 1 is directly output to the amplifier. However, when the signal S3 from the comparator 10 is supplied, it switches to the side shown by the broken line,
A received signal S1 from the duplexer 1 is outputted to an amplifier 2 via an attenuator 12.

The attenuator 12 attenuates the level of the received signal S1 supplied via the relay 11 by a desired amount by configuring the resistors 17, 18, and 19 to be connected in a π type, and outputs the level to the amplifier 2. It is something.

In the receiving circuit shown in FIG. 2 having such a configuration, the electric field strength of the radio waves received by the antenna 6 is usually low, and the DC signal (RSSI) output from the demodulator 5 is
If the voltage of S2 is smaller than the voltage value indicated by the dashed-dotted line 20 in FIG. 11 to the amplifier 2, and operates in the same manner as the conventional receiving circuit shown in FIG.

However, in a strong electric field, the received signal S
1 becomes high, so the DC signal (RSSI) S2
The voltage value also increases, and this voltage value is indicated by the dashed line 20 in FIG.
When the voltage value becomes higher than the voltage value shown by , the comparator 10 is turned on.

As a result, the signal S from the comparator 10
3 is output and supplied to relay 11, so relay 1
1 is turned on, switching to the side shown by the broken line, and the transmitting/receiving unit 1 is connected to the amplifier 2 via the attenuator 12.

The received signal S1 outputted from the transmitting/receiving unit 1 is attenuated by the attenuator 12 and input to the amplifier 2.

Therefore, the attenuated signal level is inputted to the amplifier 2 and the mixer 4, so that the amplifier 2 and the current consumption of mixer 4 increases,
This increase eliminates the possibility of impedance deviation or sensitivity suppression deterioration.

[0041] This prevents the performance of the wireless device using this receiving circuit from deteriorating, so that the wireless device can operate stably even in a strong electric field.

[0042]

[Effects of the Invention] As explained above, the receiving circuit of the present invention has the effect of being able to maintain appropriate impedance even in a strong electric field, thereby preventing deterioration of sensitivity suppression from occurring. There is.

Therefore, it is possible to stably operate a communication device using this receiving circuit.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a receiving circuit of the present invention.

FIG. 2 is a block configuration diagram of a receiving circuit according to an embodiment of the present invention.

3 is a diagram showing the relationship between the DC signal voltage output from the demodulator and the received signal level output from the transmitting/receiving unit in the circuit shown in FIG. 2; FIG.

FIG. 4 is a block diagram of a conventional receiving circuit.

5 is a diagram showing the relationship between the current consumption of the RF amplifier and mixer in the circuit shown in FIG. 4 and the received signal level output from the transmitter/receiver common unit.

[Explanation of symbols] 1　Transmitter/receiver duplexer 2 Amplifier 3　Interstage duplexer 4 Mixer 5 Demodulator 6 Antenna 10 Comparison means 11 Relay 12 Attenuation means S1 Received signal S2 DC signal

Claims (1)

[Claims] 1. A duplexer (1) that filters radio waves received by an antenna (6) and outputs a received signal (S1) at a level corresponding to the field strength of the radio waves; ), an interstage duplexer (3) that filters and outputs the signal output from the amplifier (2), and an interstage duplexer (3) that amplifies and outputs the signal output from the interstage duplexer (3). A mixer (4) that takes the frequency difference between the signal and the local oscillation signal and outputs it as a difference signal, and demodulates the difference signal to generate an audio signal (S4) and a DC signal (RSSI after received field strength) ), when the level of the DC signal (RSSI) (S2) exceeds an arbitrarily set level, the receiver circuit of a communication device is turned on and outputs a signal at a predetermined level. signal (S
a comparison means (10) which outputs the signal (3) and turns off when the level of the DC signal (RSSI) (S2) becomes below an arbitrary set level, and the output level becomes almost 0; and the signal (S3). is turned on and the duplexer (1) is connected to the amplifier (2) via the attenuation means (12).
and the output level of the comparison means (10) is approximately 0.
When this happens, the duplexer (1) and the amplifier (
2) a relay (11) that connects the transmitter/receiver (1) when the relay (11) is turned on.
The level of the received signal (S1) outputted from the amplifier (S1) is attenuated by the attenuation means (12), and the received signal (S1) at this attenuated level is input to the amplifier (2). A receiving circuit for a communication device.