JP5323613B2 - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein capability (weak electric field receiving capability) that a received signal is correctly demodulated even when field intensity of carrier wave to be received is weak is sacrificed when capability (interference wave resistance capability) for preventing accidental demodulation of the received signal by being influenced by electromagnetic waves having near frequency of a carrier wave frequency band is attempted to be raised in a receiver. <P>SOLUTION: When the field intensity of the received signal is less than first predetermined intensity, output impedance of a matching circuit becomes a value suitable for improvement of the weak electric field reception capability, when the field intensity of the received signal is equal to or more than second predetermined intensity, the output impedance of the matching circuit becomes a value suitable for improvement of the interference wave resistance capability, and thus, the weak electric field reception capability is not sacrificed even when the interference wave resistance capability is raised. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a receiving device, and more particularly to a receiving device including a matching circuit for guiding a received signal to an amplifier circuit.

A receiving apparatus typified by a mobile phone terminal or the like improves the ability to correctly demodulate a received signal (hereinafter referred to as “weak electric field receiving ability”) even when the electric field strength of received electromagnetic waves is weak. Is required.
As a technique for improving the weak electric field reception capability, for example, there is a technique disclosed in Patent Document 1.

On the other hand, even if the field strength of the received electromagnetic wave is stronger than the minimum field strength necessary for correctly demodulating the received signal, the receiving device is in the vicinity of the carrier frequency band carrying the received signal. The received signal may be erroneously demodulated by being influenced by electromagnetic waves having a frequency (hereinafter referred to as “jamming wave”).
Therefore, the receiving device is also required to improve the ability to correctly demodulate the received electromagnetic wave even if the interference wave is included (hereinafter referred to as “interference wave resistance capability”).

  In the receiver, in order to improve the capability to withstand interference, the output impedance of the matching circuit that guides the received signal to the first-stage amplifier circuit and the input impedance of the first-stage amplifier circuit do not intentionally match impedance. Thus, there is a circuit that suppresses the amplification degree of the interference wave included in the received signal in the first stage amplifier circuit.

JP 2000-13190 A

However, since the suppression of the amplification factor of the interference wave included in the reception signal also suppresses the amplification factor of the carrier wave included in the reception signal at the same time, such a receiving apparatus has an interference wave resistance capability. In order to improve, the weak electric field receiving capability is sacrificed.
Therefore, the present invention has been made in view of such problems, and an object of the present invention is to provide a receiving apparatus capable of improving the interference wave resistance capability without sacrificing the weak electric field reception capability.

  In order to solve the above-described problems, a receiving device according to the present invention is a receiving device that receives electromagnetic waves in a predetermined frequency band, and a matching circuit that transmits a received signal, and amplifies the received signal transmitted by the matching circuit An amplifying circuit, an electric field strength measuring circuit for measuring an electric field strength based on a received signal, and an impedance changing circuit for changing an output impedance of the matching circuit according to the electric field strength measured by the electric field strength measuring circuit. The impedance changing circuit is configured to output the output impedance of the matching circuit in the predetermined frequency band when the electric field intensity measured by the electric field intensity measuring circuit is equal to or higher than a first predetermined intensity. A value that does not match the input impedance in the frequency band, and the electric field strength is less than the first predetermined strength and less than the second predetermined strength. Case, characterized by a value that matches the input impedance in the predetermined frequency band of the amplifier circuit.

  Here, the mismatch between the output impedance of the matching circuit and the input impedance of the amplifier circuit means that the amplification factor of the amplifier circuit when the output impedance of the matching circuit and the input impedance of the amplifier circuit match (impedance matching). The relationship between the output impedance of the matching circuit and the input impedance of the amplifier circuit that decreases the amplification factor by 2 dBm or more as compared with the above.

  Here, the amplification factor is the power of the input signal input to the matching circuit and the output signal corresponding to the input signal output from the amplifier circuit when a signal of a predetermined frequency band is input to the matching circuit. This is the strength ratio.

  The receiving apparatus according to the present invention having the above-described configuration is a value in which the output impedance of the matching circuit and the input impedance of the amplifier circuit do not match when the electric field strength of the received reception signal is equal to or higher than the first predetermined strength. Thus, when the electric field strength of the received signal being received is less than the second predetermined strength, the value of matching between the output impedance of the matching circuit and the input impedance of the amplifier circuit is improved. As a result, the weak electric field receiving capability can be improved.

  Therefore, when the electric field strength of the received electromagnetic wave is weak by setting the electric field strength of the weak electromagnetic wave as the second predetermined strength and the electric field strength of the non-weak electromagnetic wave as the first predetermined strength (second predetermined strength). If the electric field strength of the received electromagnetic wave is not weak (in the case of the first predetermined strength or higher), the interference wave resistance capability is improved to be equal to or higher than that of the conventional receiving device. It has the effect of being able to.

  The impedance changing circuit may be configured such that when the electric field strength changes from less than the second predetermined strength to more than the second predetermined strength and the electric field strength is less than the first predetermined strength, the matching circuit The output impedance in the predetermined frequency band is set to a value that matches the input impedance in the predetermined frequency band of the amplifier circuit, and the electric field strength changes from the first predetermined strength or higher to less than the first predetermined strength. In this case, when the electric field strength is greater than or equal to the second predetermined strength, the output impedance of the matching circuit in the predetermined frequency band is set to a value that does not match the input impedance of the amplifier circuit in the predetermined frequency band. It may be characterized by this.

Thereby, the relationship between the output impedance of the matching circuit and the input impedance of the amplifier circuit changes from the matching relationship to the non-matching relationship, the threshold value of the electric field strength becomes the first predetermined strength, and changes from the non-matching relationship to the matching relationship. The threshold value of the electric field strength to be used is the second predetermined strength.
Therefore, even when the receiving device is used in a situation where the electric field strength frequently changes in a region of strength between the first electric field strength and the second electric field strength, the output impedance of the matching circuit Since the relationship with the input impedance of the amplifier circuit is not frequently changed, there is an effect that stable operation can be realized.

  The matching circuit includes an input terminal to which a received signal is input and an output terminal connected to the amplifier circuit, and the impedance changing circuit is on a connection path between the input terminal and the output terminal. The output impedance of the matching circuit in the predetermined frequency band may be changed by changing the impedance of the connection path between the specific point and the ground.

  As a result, the impedance changing circuit for changing the output impedance of the matching circuit can be configured not to be arranged in series on the connection path between the input terminal and the output terminal of the matching circuit. While propagating, the impedance changing circuit can be arranged so that the attenuation amount of the received signal is hardly affected.

  The impedance changing circuit includes an impedance element having a specific impedance value and a switch that is in one of an electrically conductive state and a non-electrically conductive state. The switch is connected in series on a connection path between the specific point and the ground, and the impedance changing circuit is configured to change the state of the switch when the electric field strength is equal to or higher than the first predetermined strength, It is good also as making it a different state from the case where it is less than 2nd predetermined intensity | strength.

Thus, for example, if an impedance element is an element composed of a capacitor and an inductor, an impedance change circuit can be realized by a combination of a switch, a capacitor, and an inductor that can be easily obtained at low cost. Has the effect of being able to.
The impedance changing circuit includes a variable capacitor connected in series on a connection path between the specific point and the ground, and the impedance changing circuit sets the capacitance value of the variable capacitor, Different electric field values may be used when the electric field intensity is equal to or higher than the first predetermined intensity and when the electric field intensity is lower than the second predetermined intensity.

  As a result, the output impedance of the matching circuit can be changed by changing the capacitance of the variable capacitor of the impedance changing circuit, so that the output impedance of the matching circuit can be changed to three or more different impedances. It has the effect of being able to.

Configuration diagram showing the configuration of the baseband wave generation circuit Impedance correspondence diagram showing relationship between output impedance of matching circuit 101 and input impedance of low noise amplifier circuit 121 Flow chart showing consistency relationship switching operation Configuration diagram showing the configuration of the baseband wave generation circuit Impedance correspondence diagram showing relationship between output impedance of matching circuit 101 and input impedance of low noise amplifier circuit 121 Flowchart 1 showing consistency relation switching operation Flowchart 2 showing consistency relationship switching operation

<Embodiment>
Hereinafter, as an embodiment of a receiving apparatus according to the present invention, the relationship in which the output impedance of the matching circuit and the input impedance of the high-frequency amplifier circuit are matched in accordance with the electric field strength of the received signal (hereinafter referred to as “matching relationship 1”). A mobile phone terminal that switches and receives a relationship that does not match (hereinafter referred to as “matching relationship 2”) will be described.

<Overview>
The mobile phone terminal according to the present embodiment communicates using a carrier wave in the 2 GHz band, and the electric field strength estimated as the electric field strength of the received reception signal (hereinafter, “the electric field strength of the received reception signal”). However, in the case of an electric field strength (for example, −104 dBm or less) that requires an improvement in weak electric field reception capability, the signal is received in matching relationship 1 and an electric field strength (for example, an improvement in interference wave resistance capability is required). -95 dBm or more), it is received with matching relationship 2.

  In addition, when the mobile phone terminal according to the present embodiment is receiving in the matching relationship 1 and the electric field strength of the received signal is changed from less than −95 dBm to −95 dBm or more, the mobile phone terminal changes to the present embodiment. Such a mobile phone terminal changes the relationship between the output impedance of the matching circuit and the input impedance of the high-frequency amplifier circuit (hereinafter referred to as “matching relationship”) from matching relationship 1 to matching relationship 2 and receives the matching relationship 2. In this case, when the electric field strength of the received signal changes from −104 dBm or more to less than −104 dBm, the mobile phone terminal according to the present embodiment changes the matching relationship from matching relationship 2 to matching relationship 1.

Therefore, the mobile phone terminal according to the present embodiment improves the weak electric field reception capability and the interference wave resistance capability when the electric field strength of the received reception signal requires the weak electric field reception capability. With the electric field strength that needs to be improved, the receiving device can improve the interference wave resistance capability.
The configuration and operation of the mobile phone terminal according to the above-described embodiment will be described in order.

<Configuration>
A feature of the cellular phone terminal according to the present embodiment is that one of the matching relations 1 and 2 is selected and received according to the electric field strength of the received signal.
A structural feature for realizing this feature is a part (hereinafter referred to as “baseband signal”) from when a received signal is received by an antenna until a signal indicating a demodulated wave of the baseband band (hereinafter referred to as “baseband signal”) is output. The baseband signal generation circuit ”will be described here, and the baseband signal generation circuit will be mainly described here. Other parts (the circuit after the baseband signal generation circuit in the transmission circuit and the reception circuit, the camera) The circuit for realizing various application functions such as a function is the same as that of an ordinary mobile phone terminal, and thus the description thereof is omitted.

Hereinafter, the configuration of the baseband signal generation circuit will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing the configuration of the baseband signal generation circuit 1000.
The baseband signal generation circuit 1000 receives a 2 GHz band carrier wave transmitted from a base station and converts the received signal into a baseband signal. The baseband signal generation circuit 1000 includes an antenna 103, a duplexer 104, a matching circuit 101, an RFIC ( Radio Frequency Integrated Circuit) 102 and impedance changing circuit 105.

The antenna 103 is an antenna for transmitting and receiving a 2 GHz band carrier wave, and is connected to the duplexer 104.
The duplexer 104 has a function of transmitting a reception signal received by the antenna 103 to the matching circuit 101, a function of transmitting a transmission signal input from a transmission circuit (not shown) to the antenna 103, and not transmitting to the matching circuit 101. Which is connected to the antenna 103, the matching circuit 101, and a transmission circuit (not shown).

The matching circuit 101 is a circuit that transmits a reception signal input from the duplexer 104 to the RFIC 102, and is connected to the duplexer 104, the RFIC 102, and the impedance changing circuit 105.
The matching circuit 101 includes a first inductor 111, a first capacitor 112, a second inductor 113, an input terminal 117, and an output terminal 118, and the connection relationship between each element is as shown in FIG. .

The inductances of the first inductor 111 and the second inductor 113 are 1.8 nH and 8.2 nH, respectively, and the capacitance of the first capacitor 112 is 100 pF.
The RFIC 102 has a function of converting the reception signal input from the matching circuit 101 into a baseband signal, and a function of estimating the electric field strength of the reception signal received by the antenna 103 based on the input reception signal. The semiconductor integrated circuit includes a matching circuit 101, an impedance changing circuit 105, and a baseband IC (not shown).

The RFIC 102 includes a low noise amplifier circuit (LNA) 121, a baseband signal conversion circuit 122, and an RSSI (Received Signal Strength Indication) value measurement circuit 123.
The low noise amplifying circuit 121 is a high frequency amplifying circuit having a small noise figure with an input impedance of 29.024 + j29.300Ω in the frequency region of 2 GHz band. And the RSSI value measuring circuit 123.

The baseband signal conversion circuit 122 converts the reception signal amplified by the low noise amplification circuit 121 (hereinafter referred to as “amplified signal”) into a baseband signal and outputs the baseband signal to the baseband IC.
The RSSI value measurement circuit 123 measures the intensity of the amplified signal input from the low-noise amplifier circuit 121 every 100 ms while measuring the time with a built-in timer, and receives the antenna 103 from the measured intensity of the amplified signal. The received field strength of the received signal is estimated, and the estimated field strength is output to the impedance changing circuit 105 as a field strength signal which is a digital value with dBm as a unit.

The RSSI value measurement circuit 123 calculates the electric field strength signal so that the electric field strength of the received signal received by the antenna 103 can be correctly estimated from the strength of the input signal based on an experiment in advance. The table to be used or the value of the coefficient group constituting the mathematical formula is defined.
The impedance changing circuit 105 changes the output impedance at the output terminal 118 of the matching circuit 101 in accordance with the electric field strength signal input from the RFIC 102, thereby changing the matching relationship to either the matching relationship 1 or the matching relationship 2. A circuit to be changed, which is connected to the RFIC 102 and the matching circuit 101.

  Here, the output impedance at the output terminal 118 of the matching circuit 101 is assumed that the antenna 103 and the duplexer 104 are connected, the duplexer 104 and the matching circuit 101 are connected, and the impedance changing circuit 105 and the matching circuit 101 are connected. In the case where nothing is connected to the tip of the output terminal 118, the impedance is in the frequency band of 2 GHz band when the antenna 103 side is viewed from the output terminal 118.

The impedance changing circuit 105 includes a switching signal generation circuit 151, a switch 154, a third inductor 155, and a second capacitor 156.
The switching signal generation circuit 151 includes a microprocessor and a memory (not shown). The switching signal generation circuit 151 has a function of latching a field strength signal that is a digital value input from the RFIC 102 and the following depending on the latched field strength signal. This is a circuit having a function of outputting such a switching signal and a function of latching the switching signal to be output.

  When the electric field strength indicated by the electric field strength signal input from the RFIC 102 is −95 dBm or more, the switching signal generation circuit 151 outputs “High” (for example, a signal having a potential of 3.3 V) as the switching signal, and − In the case of 104 dBm or less, when “Low” (for example, a signal with a potential of 0 V) is output and “High” is output as the switching signal, the electric field strength indicated by the input electric field strength signal is −104 dBm. If the switching signal is changed to less than −104 dBm from the above, when the switching signal is changed from “High” to “Low” and “Low” is output as the switching signal, the electric field strength indicated by the input electric field strength signal is −95 dBm. When it changes from less than -95 dBm or more, the switching signal is changed from "Low" to "High".

The switch 154, the third inductor 155, and the second capacitor 156 are connected in series as shown in FIG.
The switch 154 is a MOS (Metal Oxide Semiconductor) transistor switch that is in a conducting state when the switching signal input from the switching signal generation circuit 151 is “High” and is in a non-conducting state when the switching signal is “Low”. The inductance of the third inductor is 6.8 nH, and the capacitance of the second capacitor is 100 pF.

With the impedance changing circuit 105 configured as described above, the matching circuit 101 is configured such that the output impedance of the output terminal 118 in the frequency region of 2 GHz band is “High” when the switching signal input from the switching signal generation circuit 151 is “High”. 17.097 + j34.559Ω, and 29.024 + j29.300Ω when the switching signal is “Low”.
FIG. 2 is a diagram showing the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 in the frequency region of 2 GHz band, where the switching signal is “High” and “Low”. For each case, it is shown whether or not the two are in impedance matching.

  As shown in FIG. 2, when the switching signal is “High”, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplifier circuit 121 is impedance matching in the frequency region of 2 GHz band. When the switching signal is “Low”, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 is not impedance-matching.

The cellular phone terminal according to the present embodiment switches the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplifier circuit 121 between a matching relationship and a non-matching relationship, thereby receiving a weak electric field reception. This is a mobile phone terminal that switches between a case where reception is performed so as to be suitable for improvement in capability and a case where reception is performed so as to be suitable for improvement in interference wave resistance capability.
Hereinafter, the principle will be described.

If the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplifier circuit 121 is impedance matching in the frequency region of 2 GHz band, the received signal output from the matching circuit 101 in the 2 GHz band The signal of the frequency component is input to the low noise amplifier circuit 121 without being attenuated.
Therefore, when the switching signal output from the switching signal generation circuit 151 is “High”, the cellular phone terminal according to the present embodiment attenuates the received signal of the frequency component in the 2 GHz band that is the frequency band of the carrier wave. Therefore, it is possible to improve the weak electric field reception capability.

If the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 is not impedance-matched in the frequency region of 2 GHz band, the received signal output from the matching circuit 101 in the 2 GHz band The frequency component signal is attenuated and input to the low noise amplifier circuit 121.
In order to improve the jamming wave tolerance capability, it is effective to reduce the absolute value of the power intensity of the jamming wave input to the low noise amplifier circuit 121. Therefore, the jamming wave tolerance capability can be improved. At the same time, the carrier wave is also attenuated.

Increasing the amount of jamming wave attenuation can improve the ability to withstand jamming waves. However, the amount of carrier wave attenuation also increases at the same time. The case where it disappears occurs.
That is, the attenuation amount of the jamming wave satisfies the necessary jamming wave resistance capability and the necessary weak electric field receiving capability when the electric field strength of the received reception signal is −95 dBm or more. Attenuation is required.

  Therefore, the mobile phone terminal according to the present embodiment performs the later-described experiment, and when the received signal strength of the received signal is −95 dBm or more, satisfies the necessary interference wave resistance capability, and The attenuation amount of the interference wave that satisfies the required weak electric field reception capability is determined, and the inductances of the inductors 111, 113, and 115 and the capacitances of the capacitors 112 and 116 are determined so as to be the determined attenuation amount. Yes.

  Here, when the electric field strength of the received signal being received is −95 dBm, the interference wave tolerance capability (hereinafter referred to as “necessary interference wave tolerance capability”) required for the mobile phone terminal according to the present embodiment is as follows. When the mobile phone terminal according to the present embodiment is given an interference wave having a frequency of, for example, ± 0.1% of the frequency of the carrier wave, which is weaker by 30 dB than the electric field strength of the carrier wave, for example. This is an interference wave tolerance capability in which the error rate for erroneously demodulating the received signal is 0.5% or less, for example.

Further, the weak electric field reception capability (hereinafter referred to as “necessary weak electric field reception capability”) necessary for the mobile phone terminal according to the present embodiment when the electric field strength of the received signal being received is −95 dBm or more. This is a weak electric field reception capability in which the error rate for erroneously demodulating the received signal is 0.5% or less.
Therefore, in this case, if the necessary interference wave tolerance capability is satisfied, the necessary weak electric field reception capability is necessarily satisfied.

  The experimenter who determines the capability to withstand jamming uses a carrier wave of 2100 MHz, a jamming wave of 2098 MHz, and a jamming wave of 2102 MHz to change the output impedance of the matching circuit 101 little by little, An interference wave is applied to the antenna 103, and the mobile phone terminal according to the present embodiment measures an error rate at which the received carrier wave is erroneously demodulated.

The experimenter extracts the output impedance of the matching circuit 101 that satisfies the required interference wave tolerance capability and the required weak electric field reception capability from the measurement result, and based on the extracted output impedance of the matching circuit 101, Calculate the corresponding interference attenuation.
The mobile phone terminal according to the present embodiment has the error that the received signal is most erroneously demodulated within the range of the attenuation amount of the interference wave when the required interference wave tolerance capability is satisfied and the required weak electric field capability is satisfied. It is desirable to select an attenuation that results in a lower rate (highest interference wave tolerance capability).

For example, in the mobile phone terminal according to the present embodiment, as an example, the range of attenuation of the interference wave when the required interference wave resistance capability is satisfied and the required weak electric field capability is satisfied is 2 dBm to 10 dBm, It is assumed that the amount of attenuation is such that the error rate at which the received signal is demodulated most erroneously is low when it is 3 dBm.
Therefore, in the mobile phone terminal according to the present embodiment, the inductances of the inductors 111, 113, and 115 and the capacitances of the capacitors 112 and 116 are determined so that the attenuation amount of the interference wave is 3 dBm.

  However, as described above, in the mobile phone terminal according to the present embodiment, the inductances of the inductors 111, 113, and 115 and the capacitances of the capacitors 112 and 116 are determined according to the attenuation amount of the interference wave. In addition, the inductances of the inductors 111, 113, and 115 and the capacitances of the capacitors 112 and 116 are not limited to the case where the attenuation amount of the interference wave is 3 dBm as described above.

Furthermore, the mobile phone terminal according to the present embodiment has the least attenuation in the range of the attenuation amount of the interference wave when the required weak electric field capability is satisfied if the required interference wave resistance capability is satisfied. An attenuation amount may be selected.
<Operation>
The characteristic operation of the mobile phone terminal according to the above-described embodiment is that the matching relationship is switched from matching relationship 1 to matching relationship 2 or from matching relationship 2 to matching relationship 1 according to the electric field strength of the received signal. Since this is an operation for switching the matching relationship (hereinafter referred to as “matching relationship switching operation”), this matching relationship switching operation will be described below.

Since the operations other than the matching relationship switching operation are not characteristically different from the operation of a general mobile phone terminal, the description thereof is omitted.
FIG. 3 is a flowchart of the matching relationship switching operation.
The RSSI value measurement circuit 123 estimates the electric field strength of the received signal received by the antenna 103 (step S300), and outputs a digital value with dBm as a unit to the switching signal generation circuit 151 as an electric field strength signal.

  When the switching signal generation circuit 151 receives the electric field strength signal, the switching signal generation circuit 151 outputs “Low” as the switching signal, that is, the mobile phone terminal according to the embodiment receives the matching relationship 1 (step) In S310: Yes, when the received electric field strength signal is a signal indicating −95 dBm or more (step S320: Yes), the switching signal is changed to “High”, that is, the mobile phone terminal according to the present embodiment Changes the matching relationship from matching relationship 1 to matching relationship 2 (step S330), and when the electric field strength signal is not a signal indicating −95 dBm or more (step S320: No), the switching signal is not changed, that is, The cellular phone terminal according to the present embodiment does not change the matching relationship.

  When the switching signal generation circuit 151 receives the electric field strength signal, the switching signal generation circuit 151 outputs “High” as the switching signal, that is, the mobile phone terminal according to the present embodiment receives the matching signal 2. In the case (step S310: No), when the received electric field strength signal is a signal indicating −104 dBm or less (step S350: Yes), the switching signal is changed to “Low”, that is, according to the present embodiment. The mobile phone terminal changes the matching relationship from matching relationship 2 to matching relationship 1 (step S360), and does not change the switching signal when the electric field strength signal is not a signal indicating −104 dBm or less (step S350: No). That is, the mobile phone terminal according to the present embodiment does not change the matching relationship.

  When the processing of step S330 is completed, when the electric field strength signal is not a signal indicating −95 dBm or more in step S320, when the processing of step S360 is completed, or the electric field strength signal is not a signal indicating −104 dBm or less in step S350. Sometimes, the RSSI value measurement circuit 123 returns to step S300 again and receives the signal received by the antenna 103 after 100 ms has elapsed since the field strength of the received signal received by the antenna 103 was estimated last time (step S340). Estimate the electric field strength of the signal.

  Hereinafter, when the switching signal generation circuit 151 outputs “Low” as the switching signal, the electric field intensity of the received signal received by the antenna 103 changes from −97 dBm to −93 dBm, and then the electric field 10 minutes later. A specific operation of the mobile phone terminal according to the present embodiment when the intensity becomes −100 dBm and further changes to −106 dBm will be described.

When the switching signal generation circuit 151 outputs a “Low” signal, that is, when the mobile phone terminal according to the present embodiment is receiving with the matching relationship 1, the RSSI value measurement circuit 123 receives with the antenna 103. The electric field strength of the received signal is estimated (step S300), and since it is −97 dBm, a signal indicating −97 dBm is output as the electric field strength signal.
The switching signal generation circuit 151 receives an electric field strength signal indicating −97 dBm while “Low” is being output (step S310: Yes), and is not more than −95 dBm (step S320: No). Continue to output.

Therefore, the cellular phone terminal according to the present embodiment does not change the matching relationship.
The RSSI value measurement circuit 123 estimates the electric field strength of the received signal received by the antenna 103 again after 100 ms has elapsed since the previous estimation of the electric field strength of the received signal received by the antenna 103 (step S340). (Step S300) Since it can be seen that it has changed to -93 dBm, a signal indicating -93 dBm is output as the electric field strength signal.

The switching signal generation circuit 151 receives the electric field strength signal indicating −93 dBm while “Low” is being output (step S310: Yes), and is −95 dBm or more (step S320: Yes), so the switching signal is changed from “Low”. It is changed to “High” (step S330).
Therefore, the cellular phone terminal according to the present embodiment changes the matching relationship from matching relationship 1 to matching relationship 2 and receives the matching relationship.

  At this time, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplification circuit 121 is changed from the impedance matching relationship to the non-impedance matching relationship. Is attenuated by 3 dBm, and the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measurement circuit 123 is changed to -96 dBm.

However, since the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measurement circuit 123 is not less than −104 dBm, the matching relationship is not changed.
After 10 minutes have elapsed, the switching signal generation circuit 151 outputs a “High” signal, that is, the RSSI value measurement circuit 123 is in a state where the mobile phone terminal according to the present embodiment is receiving the matching relationship 2. The electric field strength of the received signal received by the antenna 103 is estimated (step S300), and −100 dBm (the received signal received by the antenna 103 is −97 dBm, but the matching relationship is the matching relationship 2; Compared to the case of relation 1, the intensity of the amplified signal output from the low noise amplifier circuit 121 is attenuated by 3 dB, and the RSSI value measurement circuit 123 is estimated to be −100 dBm, which is 3 dB less than the actual). A signal indicating −100 dBm is output as the electric field strength signal.

The switching signal generation circuit 151 receives an electric field strength signal indicating −100 dBm while outputting “High” (step S310: No), and is not less than −104 dBm (step S350: No). Continue to output.
Therefore, the cellular phone terminal according to the present embodiment does not change the matching relationship.
The RSSI value measurement circuit 123 estimates the electric field strength of the received signal received by the antenna 103 again after 100 ms has elapsed since the previous estimation of the electric field strength of the received signal received by the antenna 103 (step S340). (Step S300), it can be seen that the signal has changed to −106 dBm (the received signal received by the antenna 103 is −103 dBm), and thus a signal indicating −106 dBm is output as the electric field strength signal.

The switching signal generation circuit 151 receives an electric field strength signal indicating −106 dBm while “High” is being output (step S310: No), and is −104 dBm or less (step S320: Yes), so that the switching signal is changed from “High”. It is changed to “Low” (step S360).
Therefore, the mobile phone terminal according to the present embodiment performs demodulation by changing the matching relationship from matching relationship 2 to matching relationship 1.

  At this time, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 is changed from a relationship that is not impedance-matched to a relationship that is impedance-matched. Is not attenuated, and the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measurement circuit 123 is changed to −103 dBm.

However, since the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measuring circuit 123 is not more than −95 dBm, the matching relationship is not changed.
<Modification>
In the embodiment described above, an example of a mobile phone terminal that receives a matching relationship by selecting either the matching relationship 1 or the matching relationship 2 according to the electric field strength of the received reception signal has been described. However, in the modification, according to the electric field strength of the received signal being received, the matching relationship is the matching relationship 1 and the electric field strength of the received signal being received is, for example, −95 dBm or more and less than −85 dBm. A matching relationship suitable for improving the interference wave resistance capability (hereinafter referred to as “matching relationship 3”) and a matching relationship suitable for improving the interference wave resistance capability (hereinafter referred to as “matching relationship”) when the electric field strength of the received signal is −75 dBm or more, for example. An example of a mobile phone terminal that selects and receives one of the three matching relationships is described.

<Overview>
The mobile phone terminal according to this modification communicates using a carrier wave of 2 GHz band, and when the received signal has an electric field strength of −104 dBm or less, the mobile phone terminal receives the matching relationship 1 and −95 dBm or more− If it is less than 85 dBm, it is received with matching relationship 3, and if it is −75 dBm or more, it is received with matching relationship 4.

  In addition, when the mobile phone terminal according to this modification is received in the matching relationship 1 or 3, when the electric field strength of the received signal received is changed from less than −75 dBm to −75 dBm or more, the modification is performed. The mobile phone terminal changes the matching relationship from matching relationship 1 or 3 to matching relationship 4, and when receiving in matching relationship 1 or 4, the received signal strength of the received signal is less than -95 dBm or When changing from −85 dBm or more to −95 dBm or more and less than −85 dBm, the mobile phone terminal according to this modification changes the matching relationship from matching relationship 1 or 4 to matching relationship 3 and receives the matching relationship 3 or 4. If the received signal strength of the received signal changes from −104 dBm or more to less than −104 dBm, the mobile phone terminal according to this modification matches the matching relationship. Changing the alignment relationship 1 from engaging 3 or 4.

The configuration and operation of the mobile phone terminal according to the above-described modification will be described mainly with respect to differences from the mobile phone terminal according to the embodiment.
<Configuration>
FIG. 4 is a configuration diagram showing the configuration of the baseband signal generation circuit 2000.
The baseband signal generation circuit 2000 is a circuit that receives a 2 GHz band carrier wave transmitted from a base station and converts the received signal into a baseband signal. The baseband signal generation circuit 2000 includes an antenna 103, a duplexer 104, a matching circuit 101, an RFIC ( Radio Frequency Integrated Circuit) 102 and impedance changing circuit 405.

Since the antenna 103, the duplexer 104, the matching circuit 101, and the RFIC 102 are the same as those in the above-described embodiment, description thereof is omitted.
The impedance changing circuit 405 changes the output impedance at the output terminal 118 of the matching circuit 101 in accordance with the electric field strength signal input from the RFIC 102, thereby changing the matching relationship to either the matching relationship 1 or the matching relationship 2. A circuit to be changed, which is connected to the RFIC 102 and the matching circuit 101.

The impedance changing circuit 105 includes a control voltage generating circuit 451, a choke coil 457, and a variable capacitor 454.
The control voltage generation circuit 451 includes a microprocessor (not shown), a memory, and a DA (Digital Analog) converter, and latches a function of latching an electric field strength signal that is a digital value input from the RFIC 102. This is a circuit having a function of outputting a control signal having the following voltage between the processor and the memory according to the electric field strength signal and a function of holding the voltage of the control signal to be output.

  When the electric field strength indicated by the electric field strength signal input from the RFIC 102 is −75 dBm or more, the control voltage generation circuit 451 outputs “High” (for example, a signal having a potential of 3.3 V) as the control signal, and − When it is 95 dBm or more and less than −85 dBm, “Middle” (for example, a signal with a potential of 2.0 V) is output as the control signal, and when it is less than −104 dBm, the control signal is “Low” (for example, a potential of 0 V). Output signal).

  Further, when the control voltage generation circuit 451 outputs “Low” or “Middle” as the control signal, when the electric field strength indicated by the electric field strength signal changes from less than −75 dBm to −75 dBm or more, the control voltage is generated as “ When changing from “Low” or “Middle” to “High” and outputting “Low” or “High” as the control signal, the electric field strength indicated by the electric field strength signal is less than −95 dBm or more than −85 dBm, When it changes from -95 dBm to less than -85 dBm, the control signal is changed from "Low" or "High" to "Middle", and "Middle" or "High" is output as the control signal. When the electric field strength shown changes from −104 dBm or more to less than −104 dBm, the control signal is changed from “Middle” or “High” to “Low”.

The choke coil 457 is an inductor that blocks the AC component current and transmits only the DC component current, and is connected to the control voltage generation circuit 451 and the variable capacitor 454.
The variable capacitor 454 is a varicap diode that changes its capacitance value according to the voltage between two terminals (anode and cathode). The capacitance value is determined by a control signal input from the control voltage generation circuit. When “High”, that is, 3.3 V, 10 pF, the control signal input from the control voltage generation circuit is “Middle”, that is, when 2.0 V, the control signal is input from the control voltage generation circuit, 5 pF. “Low”, that is, 0 pF in the case of 0 V, and is connected to the choke coil 457 and the ground.

  With the impedance changing circuit 405 configured as described above, the output impedance of the output terminal 118 in the frequency region of 2 GHz band is 3.9423 + j6 when the control signal input from the control voltage generation circuit 451 is “High”. .9355Ω, 31.924 + j10.395Ω when the control signal is “Middle”, and 29.024 + j29.300Ω when the control signal is “Low”.

FIG. 5 is a diagram showing the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplifier circuit 121 in the frequency region of 2 GHz band. The control signal is “High” and “Middle”. For each of the case and the case of “Low”, it is shown whether or not the two are in impedance matching.
As shown in FIG. 5, when the control signal is “Low”, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 is impedance-matched in the frequency region of 2 GHz band. When the control signal is “Middle” and “High”, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 is a relationship in which impedance matching is not performed.

  The mobile phone terminal according to the present modification can weaken the relationship between the output impedance of the matching circuit 101 and the input impedance of the low-noise amplifier circuit 121 by switching between a matching relationship and two types of non-matching relationships. When receiving so as to be suitable for improvement of electric field reception capability, when receiving received signal so as to be suitable for improvement of interference wave resistance capability when the electric field strength of the received signal is −95 dBm or more and less than −85 dBm, − This is a mobile phone terminal that switches between a case of 75 dBm or more and a case of reception so as to be suitable for improvement of interference wave resistance capability.

  The mobile phone terminal according to the present modified example has received the received signal by the experiment for determining the attenuation amount of the interference wave that has the lowest error rate for erroneously demodulating the received signal, as described in the embodiment. When the electric field strength of the received signal is −95 dBm or more and less than −85 dBm, the error rate at which the received signal is demodulated most erroneously when the attenuation amount of the interference wave is 2 dBm is low, and the electric field of the received received signal is low. In the case where the intensity is −75 dBm or more, it is determined that the error rate at which the received signal is demodulated most erroneously becomes low when the interference wave attenuation is 4 dB.

  Therefore, in the mobile phone terminal according to this modification, when the control signal is “Middle”, the attenuation amount of the interference wave is 2 dB, and when the control signal is “High”, the attenuation amount of the interference wave is 4 dB. When the control signal is “Low”, the inductance of the inductors 111 and 113, the capacitance of the capacitor 112, and the anode and cathode of the variable capacitor 454 are applied so that the matching relationship is the matching relationship 1. The voltage, that is, the potential indicated by the control signal is determined.

<Operation>
Since the characteristic operation of the mobile phone terminal according to the above-described modified example is the switching of the matching relationship as in the embodiment, the matching relationship switching operation will be described below, and the operations other than the matching relationship switching operation will be described below. Description of is omitted.
6 and 7 are flowcharts of the matching relationship switching operation.

The RSSI value measurement circuit 123 estimates the electric field strength of the received signal received by the antenna 103 (step S600), and outputs a digital value with dBm as a unit to the control voltage generation circuit 451 as an electric field strength signal.
When receiving the electric field strength signal, the control voltage generation circuit 451 outputs “Low” as the control signal, that is, when the mobile phone terminal according to the present modification receives the matching signal 1 (step) In S610: Yes), when the received signal is a signal indicating −95 dBm or more (step S620: Yes), if the received electric field strength signal is a signal indicating −75 dBm or more (step S630: Yes). The control signal is changed to “High”, that is, the mobile phone terminal according to the present modification changes the matching relationship from matching relationship 1 to matching relationship 4 (step S640), and the electric field strength signal indicates −75 dBm or more. If the signal is not a signal (step S630: No), the control signal is changed to “Middle”, that is, the mobile phone terminal according to the present modification changes the matching relationship. The operation of changing from relation 1 to matching relation 3 (step S650) is performed.

In step S620, when the received signal received is not a signal indicating −95 dBm or more (step S620: No), the control signal is not changed. That is, the mobile phone terminal according to this modification has a matching relationship. Not going to change.
In addition, when the control voltage generation circuit 451 receives the electric field strength signal, it does not output “Low” as the control signal (step S610: No), but outputs “Middle” (step S700: Yes). That is, when the mobile phone terminal according to the present modification is receiving with the matching relationship 3 and the received signal is a signal indicating −104 dBm or less (step S710: Yes), the control signal “ Changed to “Low” (step S720), that is, the mobile phone terminal according to the present modification performs an operation of changing the matching relationship from the matching relationship 3 to the matching relationship 1.

  In step S710, when the received signal is not a signal indicating −104 dBm or less (step S710: No), if the electric field strength signal is a signal indicating −75 dBm or more (step S730: Yes), the control signal is transmitted. Changed to “High” (step S740), that is, the mobile phone terminal according to this modification changes the matching relationship from matching relationship 3 to matching relationship 4, and the electric field strength signal is not a signal indicating −75 dBm or more. (Step S730: No), the control signal is not changed, that is, the mobile phone terminal according to the present modification does not change the matching relationship.

  Further, when the control voltage generation circuit 451 receives the electric field strength signal, it does not output “Low” or “Middle” as the control signal, that is, outputs “High” as the control signal (step S610). : No, Step S700: No), that is, when the mobile phone terminal according to the present modification is receiving with the matching relationship 4, when the received signal is a signal indicating −104 dBm or less (Step S750: In Yes), the control signal is changed to “Low” (step S760), that is, the mobile phone terminal according to the present modification performs an operation of changing the matching relationship from the matching relationship 4 to the matching relationship 1.

  In step S750, when the received signal is not a signal indicating −104 dBm or less (step S750: No), if the electric field strength signal is a signal indicating −85 dBm or more (step S730: Yes), the control signal is transmitted. If the mobile phone terminal according to the present modification does not change the matching relationship and the electric field strength signal is not a signal indicating −85 dBm or more (step S770: No), the control signal is set to “Middle”. Change (step S780), that is, the mobile phone terminal according to the present modification performs an operation of changing the matching relationship from the matching relationship 4 to the matching relationship 3.

  When the process of step S640 is completed, when the process of step S650 is completed, when the electric field strength signal is not a signal indicating −95 dBm or more in step S620, when the process of step S720 is completed, the process of step S740 is completed. In step S730, when the electric field strength signal is not a signal indicating −75 dBm or more, when the processing in step S760 ends, in step S770, when the electric field strength signal is a signal indicating −85 dBm or higher, or in step S780. When the process ends, the RSSI value measurement circuit 123 returns to step S600 and receives the signal from the antenna 103 after 100 ms has elapsed since the field strength of the received signal received by the antenna 103 was estimated last time (step S660). Of the received signal To estimate the field strength.

  Hereinafter, when the control voltage generation circuit 451 outputs “Low” as a control signal, the electric field strength of the received signal received by the antenna 103 changes from −97 dBm to −93 dBm, and then − A specific operation of the mobile phone terminal according to the present modification when it changes to 73 dBm, and then the electric field strength rapidly decreases to -107 dBm will be described.

When the control voltage generation circuit 451 outputs a “Low” signal, that is, when the mobile phone terminal according to the present modification receives the matching relationship 1, the RSSI value measurement circuit 123 receives the signal from the antenna 103. The signal strength of the received signal is estimated (step S600), and since it is −97 dBm, a signal indicating −97 dBm is output as the field strength signal.
The control voltage generation circuit 451 receives the electric field strength signal indicating −97 dBm while “Low” is being output (step S610: Yes), and is not greater than −95 dBm (step S620: No). Continue to output.

Therefore, the cellular phone terminal according to the present embodiment does not change the matching relationship.
The RSSI value measurement circuit 123 estimates the electric field strength of the received signal received by the antenna 103 again after 100 ms has elapsed since the previous estimation of the electric field strength of the received signal received by the antenna 103 (step S660). (Step S600), since it can be seen that it has changed to -93 dBm, a signal indicating -93 dBm is output as the electric field strength signal.

The control voltage generation circuit 451 receives an electric field strength signal indicating −93 dBm while outputting “Low” (step S610: Yes), and is −95 dBm or more (step S620: Yes) and not −75 dBm (step S630: No), the control signal is changed from “Low” to “Middle” (step S630).
Therefore, the cellular phone terminal according to the present embodiment changes the matching relationship from matching relationship 1 to matching relationship 3 and receives it.

  At this time, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplification circuit 121 is changed from the impedance matching relationship to the non-impedance matching relationship. Thus, the intensity of the amplified signal output from the signal is attenuated by 2 dBm, and the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measuring circuit 123 changes to -95 dBm.

However, since the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measurement circuit 123 is not −104 dBm or less and not −75 dBm or more, the matching relationship is not changed.
Thereafter, the control voltage generation circuit 451 outputs the “Middle” signal, that is, the mobile phone terminal according to this modification is receiving in the matching relationship 3, and the RSSI value measurement circuit 123 is connected to the antenna 103. The electric field strength of the received signal being received is estimated (step S600), and since it is −73 dBm, a signal indicating −73 dBm is output as the electric field strength signal.

The control voltage generation circuit 451 receives an electric field strength signal indicating −73 dBm while outputting “Middle” (step S610: No, step S700: Yes), and is not −104 dBm or less (step S710: No) and is −75 dBm or more. Since there is (Step S730: Yes), the control signal is changed from "Middle" to "High" (Step S740).
Therefore, the mobile phone terminal according to the present modification receives the matching relationship from the matching relationship 3 to the matching relationship 4.

  At this time, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplifier circuit 121 is 2 dBm attenuation compared to the relationship in which the intensity of the amplified signal output from the low noise amplifier circuit 121 is impedance matched. Therefore, the intensity of the amplified signal output from the low noise amplifier circuit 121 is changed to a relationship that attenuates by 4 dBm as compared with the impedance matching relationship, and the antenna estimated by the RSSI value measurement circuit 123 The electric field strength of the received signal received at 103 changes to -75 dBm.

However, since the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measuring circuit 123 is −85 dBm or more, the matching relationship is not changed.

After that, the control voltage generation circuit 451 outputs a “High” signal, that is, the mobile phone terminal according to this modification is receiving in the matching relationship 4, and the RSSI value measurement circuit 123 is received by the antenna 103. The electric field strength of the received signal is estimated (step S600), and since it is −107 dBm, a signal indicating −107 dBm is output as the electric field strength signal.

The control voltage generation circuit 451 receives an electric field strength signal indicating −107 dBm while “High” is being output (step S610: No, step S700: No), and is −104 dBm or less (step S710: Yes). Is changed from “High” to “Low” (step S760).
Therefore, the mobile phone terminal according to the present modification performs reception by changing the matching relationship from the matching relationship 4 to the matching relationship 1.

  At this time, the relationship between the output impedance of the matching circuit 101 and the input impedance of the low noise amplifier circuit 121 is 4 dBm attenuation compared to the relationship in which the intensity of the amplified signal output from the low noise amplifier circuit 121 is impedance matched. From this relationship, the impedance matching relationship is changed, and the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measurement circuit 123 changes to −103 dBm.

However, since the electric field strength of the received signal received by the antenna 103 estimated by the RSSI value measuring circuit 123 is not more than −95 dBm, the matching relationship is not changed.
<Supplement>
As described above, as an embodiment of the receiving apparatus according to the present invention, the mobile phone terminal that receives the received signal while changing the matching relationship according to the electric field strength of the received signal has been described with the example of the embodiment and the modification. The present invention can be modified as follows, and the present invention is not limited to the receiving apparatus as shown in the above-described embodiment.
(1) In the embodiment and the modification, the mobile phone terminal that performs communication using a carrier wave of 2 GHz band has been described as an example of the receiving device. However, a receiver equipped with a circuit corresponding to the matching circuit 101 may be used. For example, it may be a mobile phone terminal that communicates using a carrier wave in a frequency band other than the 2 GHz band, or may be a receiver other than the mobile phone terminal, such as a transceiver, radio, television, or the like.
(2) In the embodiment and the modification, the configuration of the matching circuit 101 has been described with respect to the example in which the inductors 111 and 113 and the capacitor 112 are connected as shown in FIG. I do not care.

However, it is necessary to have a function of transmitting the received signal input to the matching circuit 101 to the low noise amplifier circuit 121 and a function of changing the output impedance by the impedance changing circuit 105.
(3) In the embodiment, the impedance change circuit 105 has been described with respect to the example in which the switching signal generation circuit 151, the switch 154, the inductor 155, and the capacitor 156 are connected as shown in FIG. Any other configuration may be used as long as it has a function of appropriately changing the impedance.

In addition, when the switch 154 is off, the output impedance of the impedance changing circuit 105 and the input impedance of the low noise amplifier circuit 121 are matched, and when the switch 154 is on, they are not matched. However, the switch 154 is on. It is possible to adopt a configuration in which the relationship is consistent when the switch is off and the relationship is not matched when the switch is off.
(4) In the modification, the impedance changing circuit 405 has been described with respect to the example in which the variable capacitor 454 and the choke coil 457 are connected as shown in the figure. However, there is a function for appropriately changing the output impedance of the impedance changing circuit 105. For example, other configurations may be used.

In addition, the control voltage generation circuit 451 outputs three types of signals “High”, “Middle”, and “Low”. When “High”, the matching relationship is the matching relationship 4 and when “Middle”, the matching relationship is matched. The example in which the relationship is the matching relationship 3 and the matching relationship is the matching relationship 1 in the case of “Low” has been described. However, in other combinations, for example, in the case of “High”, the matching relationship is the matching relationship 1 and “ The matching relationship may be a matching relationship 3 in the case of “Middle” and the matching relationship 4 in the case of “Low”, and two types of signals “High” and “Low” may be used. It may be configured to output.
(5) In the embodiment and the modification, the low noise amplifier circuit 121, the baseband signal conversion circuit 122, and the RSSI value measurement circuit 123 are included in one semiconductor integrated circuit called the RFIC 102. For example, the low noise amplification circuit 121, the baseband signal conversion circuit 122, and the RSSI value measurement circuit 123 may be separate components, and the RFIC 102 may include the low noise amplification circuit 121, the baseband signal conversion circuit 122, In addition to the RSSI value measurement circuit 123, a semiconductor integrated circuit including another circuit may be used.

In addition, the RSSI value measurement circuit 123 is connected to the output of the low noise amplifier circuit 121 and estimates the electric field strength of the reception signal input to the RFIC 102. However, the RSSI value measurement circuit 123 is received by the reception device. As long as the function of estimating the electric field strength of the received signal can be realized, the output of the low noise amplifier circuit 121 may not be input, and another signal may be input.
(6) In the embodiment and the modification, the RSSI value measurement circuit 123 estimates the electric field strength of the received signal every 100 ms and outputs a digital value in units of dBm as the electric field strength signal. The time interval for measuring the electric field intensity may be other intervals, or a signal that is not a digital value in units of dBm may be output as the electric field intensity signal.
(7) In the embodiment and the modification, the configuration in which no circuit exists between the duplexer 104 and the matching circuit 101 has been described. However, a diplexer or a triplexer is provided between the duplexer 104 and the matching circuit 101. For example, if there is no transmission circuit, the reception device may be configured without the duplexer 104.
(8) In the embodiment, the calibration method for correctly estimating the electric field strength of the received signal received by the antenna 103 by the RSSI value measurement circuit 123 has been described as an example. Any calibration method other than the calibration method described in the embodiment may be used as long as the calibration is performed so that the electric field strength of the received signal can be correctly estimated.
(9) In the embodiment, the experiment for determining the attenuation amount of the disturbing wave, in which the error rate for erroneously demodulating the received signal is the lowest, has been described with an example. If it is an experiment that can determine the attenuation amount of the interference wave that causes the lowest error rate to be demodulated, it may be determined by an experiment other than the experiment described in the embodiment.

  The present invention can be widely used in a receiving apparatus typified by a mobile phone terminal or the like.

101 matching circuit 102 RFIC
DESCRIPTION OF SYMBOLS 103 Antenna 104 Duplexer 105 Impedance change circuit 121 Low noise amplifier circuit 122 Baseband signal conversion circuit 123 RSSI value measurement circuit 151 Switching signal generation circuit 454 Variable capacity capacitor

Claims (4)

A receiving device for receiving electromagnetic waves in a predetermined frequency band,
A matching circuit for transmitting the received signal;
An amplifying circuit for amplifying the received signal transmitted by the matching circuit;
An electric field strength measuring circuit for measuring the electric field strength based on the received signal;
An impedance changing circuit that changes an output impedance of the matching circuit according to the electric field strength measured by the electric field strength measuring circuit;
When the electric field intensity measured by the electric field intensity measuring circuit is equal to or higher than a first predetermined intensity, the impedance changing circuit is configured to output the predetermined impedance of the amplifier circuit when the electric field intensity measured by the electric field intensity measuring circuit is greater than or equal to a first predetermined intensity. A value that does not match the input impedance in the band, and a value that matches the input impedance in the predetermined frequency band of the amplifier circuit when the electric field strength is less than the second predetermined strength that is less than or equal to the first predetermined strength and,
The matching circuit includes an input terminal for receiving a received signal and an output terminal connected to the amplifier circuit,
The impedance changing circuit changes the impedance of a connection path between a specific point on the connection path between the input terminal and the output terminal and the ground, and thereby outputs the matching circuit in the predetermined frequency band. A receiving apparatus characterized by changing impedance . When the electric field intensity changes from less than the second predetermined intensity to more than the second predetermined intensity and the electric field intensity is less than the first predetermined intensity, the impedance changing circuit is When the output impedance in a predetermined frequency band is set to a value that matches the input impedance in the predetermined frequency band of the amplifier circuit, and the electric field strength changes from the first predetermined strength or higher to less than the first predetermined strength. When the electric field strength is equal to or higher than the second predetermined strength, the output impedance of the matching circuit in the predetermined frequency band is set to a value that does not match the input impedance of the amplifier circuit in the predetermined frequency band. The receiving apparatus according to claim 1. The impedance changing circuit is:
An impedance element having a specific impedance value;
A switch that is in either one of the electrically conductive state and the non-electrically conductive state,
The impedance element and the switch are connected in series on a connection path between the specific point and the ground,
The impedance changing circuit makes the state of the switch different between a case where the electric field strength is equal to or higher than the first predetermined strength and a case where the electric field strength is lower than the second predetermined strength. Item 4. The receiving device according to Item 1 . The impedance changing circuit is:
A variable capacitor connected in series on a connection path between the specific point and ground;
The impedance changing circuit is configured such that the capacitance value of the variable capacitance capacitor is different from each other depending on whether the electric field strength is greater than or equal to the first predetermined strength and less than the second predetermined strength. The receiving device according to claim 1 .

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