JPH09191263A - Reception signal amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To demodulate a reception signal even when the electric field strength of the reception signal is high and to increase the reception sensitivity without incurring increased current consumption even when the electric field strength of the reception signal is weak. SOLUTION: A preamplifier 31 acts like an amplifier whose gain is higher than the unity. An attenuator 32 acts like an amplifier whose gain is smaller than the unity. A signal line 33 acts like an amplifier whose gain is the unity. An intermediate frequency amplifier section 139 detects an electric field strength of a reception signal. Switches 34, 35 and a control section 36 are used to insert the attenuator 32 between an antenna multicoupler 12 and a high frequency amplifier 131 whose gain is constant when the detected electric field strength is a 1st threshold level, to insert the signal line 33 when the electric field strength is a 2nd threshold level or over and less than the 1st threshold level and to insert the preamplifier 31 when the electric field strength is less than the 2nd threshold level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a received signal amplifying apparatus for amplifying a high frequency signal received by an antenna by a high frequency amplifying means having a constant gain.

[0002]

2. Description of the Related Art Generally, in a mobile phone, a high frequency signal received by an antenna is amplified to a predetermined level and then demodulated. In the case of amplifying a high frequency signal received by an antenna, a conventional mobile phone is designed to be amplified by a high frequency amplifier having a predetermined constant gain.

[0003]

However, in such a configuration, when a high-frequency signal having a strong electric field exceeding a predetermined dynamic range is received, the output of the high-frequency amplifier is distorted and the received signal is not received. There was a problem that it could not be demodulated.

In order to solve this problem, an automatic gain control amplifier (hereinafter referred to as "AGC amplifier") is used as a high frequency amplifier.
That. ) Can be used. However,
In such a configuration, if the dynamic range of the signal level to be handled is widened, the power consumption increases,
It cannot be used in mobile phones that use batteries as power sources.

Further, in the conventional mobile phone, since not only the high frequency amplifier but also the gain of the entire receiver is constant, there is a problem that only a sensitivity determined by this gain can be obtained in a weak electric field. .

The present invention has been made in view of the above problems, and its object is to demodulate a received signal without increasing the current consumption even when a high frequency signal having a strong electric field strength is received. In addition, it is an object of the present invention to provide a reception signal amplifying device capable of increasing the reception sensitivity as compared with the conventional case when a high frequency signal having a weak electric field is received.

[0007]

According to a first aspect of the present invention, there is provided a received signal amplifying device for amplifying a high frequency signal received by an antenna by a high frequency wave amplifying device having a constant gain. 1 amplifying means, 2nd amplifying means having a gain of 1, 3rd amplifying means having a gain larger than 1, electric field strength detecting means for detecting electric field strength of the high frequency signal received by the antenna, and electric field When the electric field strength detected by the strength detecting means is equal to or higher than the first threshold value set in advance, the first amplifying means is selected and inserted between the antenna and the high frequency amplifying means, and the electric field strength is the first.
If it is less than the second threshold value that is less than the predetermined threshold value of
If the amplification means is selected and inserted between the antenna and the high frequency amplification means, and the electric field strength is less than the second threshold value,
And selecting means for selecting the amplifying means and inserting it between the antenna and the high frequency amplifying means.

In the above structure, when the electric field strength of the received signal is equal to or higher than the first threshold value, the first amplifying means is inserted between the antenna and the high frequency amplifying means. As a result, the received signal having a high electric field strength is attenuated and input to the high frequency amplification means. If the electric field strength is less than the first threshold value and equal to or more than the second threshold value, the second amplification means is inserted. As a result, the received signal having a normal electric field strength is directly input to the high frequency amplification means. If the electric field strength is less than the second threshold value, the third amplifying means is inserted. As a result, the received signal having a weak electric field strength is amplified and input to the high frequency amplification means. From the above, it is possible to deal with a received signal having a weak electric field strength to a received signal having a strong electric field strength without expanding the dynamic range of the high frequency amplifying means.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[One Embodiment] First, one embodiment of the present invention will be described. In the following description, the case where the present invention is applied to a received signal amplifying device of a mobile phone adopting a digital cellular system as a communication system will be described as a representative.

[Structure] FIG. 1 is a block diagram showing the structure of an embodiment of a received signal amplifying apparatus of the present invention. Before describing the configuration of FIG. 1, the configuration of a digital cellular type mobile phone to which the present invention is applied will be described first.

FIG. 2 is a block diagram showing the configuration of a digital cellular type mobile phone. In the mobile phone shown, a high frequency signal sent from a base station (not shown) is received by the antenna 11 and then limited to a predetermined band by the antenna duplexer 12. As a result, unnecessary components included in the received signal are removed.

After that, the received signal is amplified to a certain level by the receiving unit 13 and then converted into an intermediate frequency signal. The intermediate frequency signal is demodulated by the modulator / demodulator 14. As a result, the intermediate frequency signal is converted into a baseband signal. The baseband signal is decoded by the audio processing unit 15. As a result, an analog voice signal is obtained. This voice signal is converted into voice by the speaker 16 and provided to the user.

On the other hand, the voice of the user is the microphone 1
7, it is converted into an analog voice signal. This audio signal is encoded by the audio processing unit 15. As a result, a digital voice signal is obtained. This audio signal is modulated by the modulation / demodulation unit 14. Thereby, an intermediate frequency signal is obtained.

The intermediate frequency signal is converted into a high frequency signal by the transmission section 18 and then amplified to a certain level.
The amplified high frequency signal is band-limited by the antenna duplexer 12 and then transmitted from the antenna 11 to the base station.

In FIG. 2, reference numeral 19 denotes an operation unit for the user to perform a call-out operation and a call-in operation. Also, 2
Reference numeral 0 is a control unit that controls each unit of the telephone according to a transmission / reception sequence and controls for interfacing with the user. The above is the configuration of the digital cellular mobile phone.

Next, with reference to FIG. 1, the structure of a received signal amplifying apparatus which is a feature of the present invention will be described. FIG.
In FIG. 2, the same reference numerals are given to the parts that perform the same functions as in FIG.

The received signal amplifying apparatus of the present embodiment sets the amplitude level of the received signal input to the high frequency amplifier 131 provided in the receiving unit 13 based on the electric field strength of the received signal detected by the receiving unit 13. To control. Therefore, first, the configuration of the receiving unit 13 will be described.

FIG. 1 shows a receiver of the double superheterodyne system as the receiver 13. That is, the high frequency signal input to the receiving unit 13 is first amplified by the high frequency amplifier 131 with a constant gain, and then band-limited to a predetermined band by the band pass filter 132. The band-limited high-frequency signal is transmitted to the mixer 133 and the local oscillator 134.
Is converted into a first intermediate frequency signal by the.

The first intermediate frequency signal is band-limited to a predetermined band by the band pass filter 135 and then converted into a second intermediate frequency signal by the mixer 136 and the local oscillator 137. The second intermediate frequency signal is band-limited to a predetermined band by the band pass filter 138 and then amplified by the intermediate frequency amplifier 139.

As the high frequency amplifier 131, for example, a low noise amplifier having a low noise figure and good distortion characteristics is used. Further, as the intermediate frequency amplifier 139, for example, a logarithmic amplifier is used to detect the electric field strength of the received signal. The above is the configuration of the receiving unit 13.

The receiving signal amplifying apparatus of the present embodiment focuses on the fact that the electric field strength of the receiving signal is detected by the intermediate frequency amplifier 139, and based on the electric field strength detected by the intermediate frequency amplifier 139, the high frequency amplifier is detected. The input level of the received signal to 131 is controlled.

This control is performed by the preamplifier 31 and the attenuator 3
2, signal line 33, switches 34 and 35, and control unit 36
Is executed by

Here, the preamplifier 31 has a function of amplifying the received high frequency signal. That is, the preamplifier 31 operates as an amplifier having a gain larger than 1 (0 dB in logarithmic display). The gain of this preamplifier 31 is set to, for example, 10 dB. Attenuator 3
2 has a function of attenuating the received high frequency signal.
That is, the attenuator 32 operates as an amplifier having a gain smaller than 1. The gain of the attenuator 32 is, for example,
It is set to -20 dB. The signal line 31 has a function of passing the received high frequency signal as it is. That is,
This signal line operates as an amplifier having a unity gain.

The switch 34 has a function of inserting any one of the preamplifier 31, the attenuator 32, and the signal line 33 between the antenna duplexer 12 and the high frequency amplifier 131. The switch 35 has a function of connecting the power supply terminal of the preamplifier 31 to the power supply line or disconnecting it from this power supply line.

The control unit 36 has a function of controlling the operations of the switches 34 and 35 based on the electric field strength of the received signal detected by the intermediate frequency amplification unit 139, the details of which will be described later. The control unit 36 is the control unit 2 shown in FIG.
It may be combined with 0.

[Operation] The operation of the above configuration will be described. First, the electric field strength detection operation of the intermediate frequency amplifier 139 will be described.

In the digital cellular mobile phone system, in order to reduce the power consumption of the mobile phone,
The receiving unit 13 and the transmitting unit 18 of the mobile phone are driven in a time division manner. Therefore, the intermediate frequency amplifier 139 detects the electric field strength of the received signal only during the period when the receiver 13 is driven.

This will be described in more detail with reference to FIG. FIG. 3 is a diagram showing physical channels for performing communication between a mobile phone and a base station. As shown, this physical channel has a time slot T for transmission.
, A reception time slot R, and an idle time slot I.

In such a configuration, the transmission from the mobile telephone to the base station is performed during the transmission time slot T, and the transmission from the base station to the mobile telephone (reception of the mobile telephone) is the reception time. It is performed in the period of slot R.
Therefore, the reception unit 13 of the mobile phone is driven during the reception time slot R, and the transmission unit 18 is driven during the transmission time slot T. However, the receiving unit 13 is also driven during the idle time slot I. This is to monitor the electric field strength of the signal transmitted from the base station of the adjacent cell.

From the above, the intermediate frequency amplifier 139 detects the electric field strength of the received signal during the period of the receiving time slot R and the period of the idle time slot I. In this case, the electric field strength of the combined signal of the desired signal and the interfering signal is detected during the receiving time slot R. On the other hand, during the idle time slot I, the electric field strength of the interfering signal is detected.

Here, the desired signal is a high frequency signal sent from the base station with which the user is communicating. In contrast,
The interfering signal is a high-frequency signal or the like sent from a base station other than the base station with which it is communicating. A base station other than the one with which you are communicating is a base station of the mobile phone system because you are using it, and you are using with a base station other than the base station with which you are communicating. A base station of a mobile phone system other than a mobile phone system.

That is, in the telephone communication by the digital cellular type mobile phone, the wireless zones of a plurality of mobile phone systems are currently mixed. FIG. 4 shows an example. In the illustrated example, the cells A, B, C, D, and
A case where a wireless zone X including E, F, and G and a wireless zone Y including cells a, b, and c indicated by broken lines are mixed is shown.

In such a situation, the wireless zone X
When the user Ms of moves from cell D to cell C and passes directly under the base station of cell a in the wireless zone Y, the high frequency signal output from this base station is received as a strong electric field interference signal. As a result, the high-frequency amplifier 131 is subject to sensitivity suppression due to saturation, inter-modulation distortion sensitivity suppression, and the like. The above is the electric field strength detection operation of the intermediate frequency amplifier 139.

Next, the operation of controlling the input level of the high frequency signal to the high frequency amplifier 131 based on the detected electric field strength will be described.

The signal RSSI indicating the electric field strength detected by the intermediate frequency amplifier 139 is supplied to the control unit 36. The control unit 36 controls the selection operation of the switches 34 and 35 based on the electric field strength indicated by the received electric field strength detection signal RSSI. However, this control is performed based on the electric field strength detected during the reception time slot R. Thereby, the selection operation of the switches 34 and 35 is
It will be controlled based on the electric field strength of the combined signal.

This control is performed as follows. First, a case will be described in which the electric field strength indicated by the received electric field strength detection signal RSSI is equal to or higher than a predetermined first threshold value (for example, -30 dBm). That is, a case where a high frequency signal having a strong electric field strength is received will be described. In this case, the switch 34 is set to the off state. As a result, the power supply of the preamplifier 31 is set to the cutoff state.
As a result, the preamplifier 31 is set to the off state. As a result, the current consumption of the preamplifier 31 becomes zero.

In this case, the movable contact 351 of the switch 35 is connected to the fixed contact 353. As a result, the attenuator 32 is inserted between the antenna duplexer 12 and the high frequency amplifier 131. As a result, the high frequency signal band-limited by the antenna duplexer 12 is attenuated by the attenuator 32 and then supplied to the high frequency amplifier 131.

As a result, it is possible to prevent the high frequency amplifier 131 from becoming saturated even though a high frequency signal having a strong electric field strength is received. As a result, the received signal can be demodulated without increasing the current consumption.

Next, a case where the electric field strength indicated by the received electric field strength detection signal RSSI is less than the first threshold value and is equal to or more than the second threshold value (for example, -90 dBm) set in advance will be described. That is, the case where the electric field strength of the received signal is good will be described. In this case, the switch 34 is set to the off state as in the case of the strong electric field. As a result, the preamplifier 31 is set to the off state.

In this case, the movable contact 351 of the switch 35 is connected to the fixed contact 354. As a result, the signal line 33 is inserted between the antenna duplexer 12 and the high frequency amplifier 131. As a result, the high-frequency signal band-limited by the antenna duplexer 12 is directly used as the high-frequency amplifier 13
1 is supplied. Thereby, in this case, the normal operation is performed.

Next, the case where the electric field strength indicated by the received electric field strength detection signal RSSI is less than the second threshold value will be described. That is, a case where a high frequency signal having a weak electric field strength is received will be described. In this case, the switch 34 is set to the ON state. As a result, the power supply of the preamplifier 31 is turned on. As a result, the preamplifier 31 is set to the ON state.

In this case, the movable contact 351 of the switch 35 is connected to the fixed contact 352. As a result, the preamplifier 31 is inserted between the antenna duplexer 12 and the high frequency amplifier 131. As a result, the antenna duplexer 12
The high-frequency signal whose band has been limited by is amplified by the preamplifier 31 and then supplied to the high-frequency amplifier 131.

As a result, the input level of the received signal to the high frequency amplifier 131 can be increased even though the high frequency signal having a weak electric field strength is received. As a result, the reception sensitivity of the high frequency signal can be increased. Incidentally, if the gain of the preamplifier 31 is set to 10 dB, the receiving sensitivity can be increased by about 2 dB.

[Effects] According to the present embodiment described above, the following effects can be obtained. (1) First, according to the present embodiment, three types of amplifiers (a preamplifier 31, an attenuator 32, and a signal line 33) are prepared, and one of these is selected based on the electric field strength of the received signal. Is selected and the selected amplifier is inserted between the antenna duplexer 12 and the high frequency amplifier 131.
When a high-frequency signal with a strong electric field strength is received, the received signal can be demodulated without increasing the current consumption. The sensitivity can be increased.

Even when a high frequency signal having a strong electric field strength is received, it is possible to demodulate the received signal or to increase the reception sensitivity when a high frequency signal having a weak electric field strength is received. 12 and high frequency amplifier 131
Can be achieved by providing an AGC amplifier between and. However, in such a configuration, the AGC amplifier must be set to the ON state at all times, so that the power consumption of the AGC amplifier becomes a problem. On the other hand, in the present embodiment, since only the amplifier inserted between the antenna duplexer 12 and the high frequency amplifier 131 has to be set to the ON state, such a problem does not occur.

(2) Further, according to the present embodiment, since the amplifier having the gain smaller than 1 is realized by the attenuator 32 constituted by the passive element, the power consumption of this amplifier can be ignored. it can.

(3) Further, according to the present embodiment, since the amplifier having the gain of 1 is realized by the signal line 33, the power consumption of this amplifier can be ignored.

(4) Further, according to the present embodiment, the electric field strength detected by the intermediate frequency amplifier 139 is used as the electric field strength of the received signal, so the number of components dedicated to the received signal amplifying apparatus is reduced. be able to.

(5) Further, according to the present embodiment, since the electric field strength of the reception signal during the period of the reception time slot R is used as the electric field strength of the reception signal, the case where the electric field strength is increased by the interfering signal. Not only this, it is possible to deal with the case where the electric field strength of the desired signal becomes strong due to variations in the propagation environment of the desired signal.

[Other Embodiments] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment.

(1) For example, in the above embodiment, the case where one amplifier is used as the amplifier having the amplification degree larger than 1 has been described. However, in the present invention, by using a plurality of thresholds as the first threshold, a plurality of amplifiers having different amplification degrees may be used as the amplifier. According to such a configuration, there is an advantage that the input level of the high frequency signal to the high frequency amplifier 131 can be finely controlled according to the electric field strength. This is also the case for amplifiers whose gain is less than unity.

(2) In the above embodiment, the case where the input level of the high frequency signal to the high frequency amplifier 131 is controlled based on the electric field strength detected during the time slot R has been described. However, in the present invention, the input level may be controlled based on the electric field strength detected during the reception time slot R and the electric field strength detected during the idle time slot I.

That is, as an amplifier having an amplification degree smaller than 1, for example, two amplifiers having different amplification degrees are prepared.
The electric field strength detected during the reception time slot R is equal to or higher than the first threshold value, and the idle time slot I
When the electric field intensity detected during the period is less than the third threshold value set in advance, one of the amplifiers is inserted between the high frequency amplifier 131 of the antenna duplexer 12 and detected during the receiving time slot R. When the generated electric field strength is equal to or higher than the first threshold value and the electric field strength detected during the idle time slot I is equal to or higher than the third threshold value, the other amplifier is inserted.

According to this structure, when the electric field strength of the desired signal is normal but the electric field strength of the interfering signal becomes large, one of the amplifiers has a high frequency amplifying section 131 of the antenna duplexer 12. If the electric field strength of the desired signal becomes large even though the electric field strength of the interfering signal is small, the other amplifier is inserted.
As a result, different levels can be set as the input level of the high frequency amplifier 131 depending on whether the electric field strength of the combined signal becomes large due to the interfering signal or when the desired signal becomes large. An input level suitable for each case can be set.

(3) Further, in the above embodiment, the case where the present invention is applied to the received signal amplifying apparatus of the digital cellular type portable telephone has been described. However, the present invention can also be applied to a received signal amplifying device for an analog cellular type mobile phone.

In this case, if two receiving units having a small correlation are provided, the input level of the high frequency amplifier 131 is controlled based on the electric field strength of the combined signal and the electric field strength of the interfering signal as in (2) above. can do. That is, of the two receiving units, the electric field strength detected by the receiving unit having the poor reception state is the electric field strength of the interfering signal, and the electric field strength detected by the receiving unit having the good reception state is the composite signal. The electric field strength is used.

In an analog cellular type mobile phone, a space diversity system is usually adopted as a receiving system. Therefore, in such a mobile phone, the above-mentioned control can be performed without adding one receiving unit.

In this case, when the switching method is adopted as the output method of the reception signal, the electric field strength detected by the selected reception section is used as the electric field strength of the combined signal, and the reception section not selected is used. The electric field strength detected in step 3 may be used as the electric field strength of the interfering signal. On the other hand, when the combining method is adopted as the output method, the electric field strength detected by the receiving section with the poor reception state is used as the electric field strength of the combined signal, and the electric field strength detected by the better receiving section is used. May be used as the electric field strength of the interfering signal.

Besides this, the present invention can of course be variously modified without departing from the scope of the invention.

As described above, according to the present invention, 3
A kind of amplifying means is prepared, one of them is selected based on the electric field strength of the received signal, and the selected amplifying means is inserted between the antenna and the high frequency amplifying means. When a high-frequency signal with a strong signal is received, the received signal can be demodulated without increasing the current consumption, and when a high-frequency signal with a weak electric field strength is received, the receiving sensitivity is higher than before. Can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a digital cellular type mobile phone.

FIG. 3 is a diagram for explaining the operation of the embodiment and is a diagram for explaining an electric field strength detection operation.

FIG. 4 is a diagram for explaining the operation of the embodiment and is a diagram for explaining the types of interfering signals.

[Explanation of symbols]

 11 ... Antenna 12 ... Antenna duplexer 13 ... Receiving part 131 ... High frequency amplifying part 132, 135, 138 ... Band pass filter 133, 136 ... Mixer 134, 137 ... Local oscillator 139 ... Intermediate frequency amplifying part 31 ... Preamplifier 32 ... Attenuator 33 ... Signal lines 34,35 ... Switch 36 ... Control unit

Claims (3)

[Claims] 1. A received signal amplifying device for amplifying a high frequency signal received by an antenna by a high frequency wave amplifying means having a constant gain, comprising: a first amplifying means having a gain smaller than 1; and a second amplifying means having a gain of 1. Means, third amplifying means having a gain larger than 1, electric field strength detecting means for detecting electric field strength of the high frequency signal received by the antenna, and electric field strength detected by the electric field strength detecting means are predetermined. In the case of the first threshold value or more, the first amplifying means is selected and inserted between the antenna and the high frequency amplifying means, and the electric field strength is less than the first threshold value and the second predetermined value is set. In case of the threshold value or more, the second amplifying means is selected and inserted between the antenna and the high frequency amplifying means,
When the electric field strength is less than the second threshold value, it is provided with a selecting means for selecting the third amplifying means and inserting it between the antenna and the high frequency amplifying means. Received signal amplifier. 2. The first amplifying means is an attenuating means composed of a passive element, and the second amplifying means is
The received signal amplifying device according to claim 1, wherein the received signal amplifying device is a signal line that allows an input signal to pass therethrough. 3. The first amplifying means has two different gains.
It is configured to have two amplification means, the electric field strength detection means, as the electric field strength of the received signal,
The selecting means is configured to detect the electric field strength of the combined signal of the desired signal and the disturbing signal and the electric field strength of the disturbing signal, and the selecting means has the electric field strength of the combined signal equal to or higher than the first threshold value and the disturbing effect. When the electric field strength of the signal is equal to or higher than a predetermined third threshold value, one of the two amplifying means is selected and inserted between the antenna and the high frequency amplifying means, and the combined signal is obtained. Is greater than or equal to the first threshold value and the electric field strength of the interfering signal is less than a predetermined third threshold value, the other amplifying means is selected and the antenna and the high frequency amplifying means are selected. It is constituted so that it may be inserted between them.
The received signal amplifying device described.