High-frequency front-end circuit

Abstract

A high-frequency front-end circuit (10A) that has the following features: a triplexer circuit (20A) comprising a first transmit filter (211), a receive filter (221) and a second transmit filter (212), wherein one end of the first transmit filter (211) and one end of the receive filter (221) and one end of the second transmit filter (212) are connected to each other by a common junction; a low-noise amplifier (LNA); and a phase adjustment circuit (30A) that is connected between the receive filter (221) and the low-noise amplifier (LNA), where the first transmit filter (211) is set such that a fundamental frequency of a first transmit signal in a first communication band falls into a passband of the first transmit filter (211), the receive filter (221) is set such that a fundamental frequency of a received signal in the first communication band falls into a passband of the receive filter (221), the second transmit filter (212) is set such that a fundamental frequency of a second transmit signal in a second communication band, which differs from the first communication band, falls into a passband of the second transmit filter (212), where the transmission of the second transmit signal and the reception of the received signal are carried out simultaneously, wherein, assuming that a Smith chart is divided into four quadrants by a first line representing pure resistance and by a second line connecting points along an outer periphery of the Smith chart, each with a phase of 90°, and a reference impedance point, the phase adjustment circuit (30A) performs a phase adjustment such that, at a harmonic frequency of the second transmit signal, a quadrant in which a phase of the low-noise amplifier (LNA) is present when viewed from the receive filter (221), and a quadrant in which a phase is present when viewed from the low-noise amplifier (LNA) towards the receive filter (221), are not in a conjugate relationship.

Description

Technical field

[0001] The present invention relates to a high-frequency front-end circuit for transmitting and receiving high-frequency signals. State of the art

[0002] A variety of high-frequency front-end circuits have been designed to date. One example of such a circuit is a duplexer, which is a combination of a transmit filter and a receive filter, as disclosed in patent document 1.

[0003] In a duplexer, one end of the transmit filter and one end of the receive filter are connected to a common terminal, and this common terminal is connected to an antenna or an antenna-side circuit. The other end of the transmit filter is connected to a transmit circuit, and the other end of the receive filter is connected to a receive circuit.

[0004] In the high-frequency front-end circuit of the type described above, since it has a configuration in which the transmit filter and the receive filter are connected, an impedance is set such that the circuit is open at a fundamental frequency of a transmit signal when viewed from the receive filter side towards the transmit filter side, with the intention of preventing the transmit signal from entering the receive filter side. List of mentioned documents Patent document

[0005] Patent document 1: Unexamined Japanese patent application with publication no. 2004-120295.

[0006] From DE 699 29 534 T2, a high-frequency radio circuit is known in which a phase controller is arranged between a receiving filter and a low-noise amplifier. The phase controller is designed such that the impedance of a receiving terminal at the transmitting frequency and the input impedance of the low-noise amplifier cannot be matched by complex conjugates. Brief description of the invention Technical problem

[0007] However, in the high-frequency front-end circuit of the related technique, it was found that the receive sensitivity in the receiving circuit connected to the receiving filter deteriorates, even when attempts are made to ensure isolation between the transmitting filter and the receiving filter, as described above.

[0008] Accordingly, it is an object of the present invention to create a high-frequency front-end circuit that is capable of preventing a deterioration of receiver sensitivity. Solution to the problem

[0009] The present invention provides a high-frequency front-end circuit according to claim 1.

[0010] With the features described above, an impedance mismatch at the harmonic frequency, which differs from the fundamental frequency of the received signal, can easily be established between the receiving filter and the low-noise amplifier. Consequently, noise corresponding to the harmonic frequency is prevented from being fed into the low-noise amplifier.

[0011] In the high-frequency front-end circuit according to the present invention, the phase adjustment circuit preferably performs the phase adjustment such that at the harmonic frequency, the quadrant in which the phase of the low-noise amplifier is present when viewed from the receiving filter, and the quadrant in which the phase is present when viewed from the low-noise amplifier towards the receiving filter, are positioned on opposite sides of the second line.

[0012] The feature described above can easily increase the degree of impedance mismatch at the harmonic frequency between the receiving filter and the low-noise amplifier.

[0013] In the high-frequency front-end circuit according to the present invention, the phase adjustment circuit preferably performs a phase adjustment such that an impedance is set at the fundamental frequency of the received signal in order to approximate the reference impedance.

[0014] The feature described above can further reduce transmission loss of the received signal at the fundamental frequency, while ensuring impedance mismatch at the specific frequency.

[0015] The high-frequency front-end circuit according to the present invention is preferably configured as follows. The phase-setting circuit comprises at least one electronic component of the type shown, which includes a reactance component.

[0016] With the feature described above, the configuration of the phase adjustment circuit can be easily modified, and the impedance mismatch at the harmonic frequency between the receiving filter and the low-noise amplifier can be ensured with higher reliability.

[0017] The high-frequency front-end circuit according to the present invention can be configured as follows. The phase adjustment circuit performs the phase adjustment for a signal at the harmonic frequency based on the length of a transmission line over which the received signal is transmitted.

[0018] With the feature described above, the high-frequency front-end circuit can be implemented with a simple configuration, while reliably ensuring impedance mismatch at the harmonic frequency between the receiving filter and the low-noise amplifier.

[0019] The features described above reliably prevent the transmitted signal from being fed into the LNA (low-noise amplifier) ​​during simultaneous communication, according to carrier aggregation. Consequently, a deterioration in receive sensitivity during carrier aggregation is prevented. Advantageous effects of the invention

[0020] According to the present invention, it is possible to prevent a signal in a frequency band, with the exception of the fundamental frequency of the received signal, from propagating in steps following the receiving filter, and to prevent a deterioration of the receiving sensitivity. Brief description of the drawings Fig. Figure 1 is a block diagram of a high-frequency front-end circuit according to a first example. Fig. Figure 2 shows the Smith chart, which is referenced to explain the principle of the high-frequency front-end circuit according to the first example. Fig. Figure 3 is an equivalent circuit diagram illustrating an example of a phase adjustment circuit according to the first example. Fig. Figure 4 is an equivalent circuit diagram illustrating another example of the phase adjustment circuit according to the first example. Fig. Figure 5 shows the Smith chart, which is referenced to explain the principle of another example of the high-frequency front-end circuit according to the first example. Fig. Figure 6 is a block diagram of a high-frequency front-end circuit according to an embodiment of the present invention. Fig. Figure 7 shows the Smith chart, which is referenced to explain the principle of the high-frequency front-end circuit according to the embodiment of the present invention. Description of the exemplary implementations

[0021] A high-frequency front-end circuit according to a first example is described below with reference to the drawings. Fig. Figure 1 is a block diagram of the high-frequency front-end circuit according to the first example.

[0022] As in Fig. As illustrated in Figure 1, the high-frequency front-end circuit designated 10 comprises a duplexer 20, a phase adjustment circuit 30, and a low-noise amplifier LNA. The duplexer 20 comprises a Tx filter 21, which corresponds to a "transmit filter" in the present invention, and an Rx filter 22, which corresponds to a "receive filter" in the present invention.

[0023] One end of the Tx filter 21 and one end of the Rx filter 22 are connected at a common junction. This common junction is connected to an antenna or an antenna-side circuit (not illustrated). The antenna serves to transmit a signal that has passed through the Tx filter 21 and to receive a signal from the outside.

[0024] The Tx filter 21 is set such that a fundamental frequency of the transmitted signal falls within a passband of the Tx filter 21. The Tx filter 21 is set to provide a predetermined attenuation for a frequency of the received signal. The other end of the Tx filter 21 is connected to an output terminal of a power amplifier PA in a transmit circuit 80. An impedance matching circuit may be included here to perform impedance matching at the frequency of the transmitted signal between the power amplifier PA and the Tx filter 21.

[0025] The Rx filter 22 is configured such that a fundamental frequency of the received signal falls within a passband of the Rx filter 22. The Rx filter 22 is configured to provide a predetermined attenuation for the fundamental frequency of the transmitted signal. The Rx filter 22 features unbalanced-to-balanced conversion functionality, and its other end forms a pair of balanced terminals. The other end of the Rx filter 22 is connected, via the phase-adjusting circuit 30, to an input terminal of the low-noise amplifier LNA. An output terminal of the low-noise amplifier LNA is connected to a receive demodulation circuit (not shown).

[0026] The phase adjustment circuit 30 has a circuit configuration to perform impedance matching between the Rx filter 22 and the low-noise amplifier LNA in a fundamental frequency band of the received signal. The circuit configuration of the phase adjustment circuit 30 is implemented based on the principle described below. Fig. Figure 2 shows the Smith chart, which is referenced to explain the principle of the high-frequency front-end circuit according to the first example.

[0027] In the high-frequency front-end circuit 10 of the present invention, as described in Fig. As illustrated in Figure 2, phase matching is performed by dividing the Smith chart into four quadrants, as described below, and by utilizing the property that the impedance is present in each of the four quadrants. It should be noted that Fig. Figure 2 illustrates the normalized Smith chart. In other words, in Fig. 2 the Smith diagram illustrates that an impedance of 100 Ω corresponds to the impedance 1 in a pair of symmetrical lines.

[0028] One method of dividing the Smith chart into four quadrants is described first. It is assumed that a pure resistance line exists in the Smith chart, specifically a line in Fig. A line extending from a point of impedance 0, passing a point of impedance 1 (i.e., a reference impedance point), and reaching a point of impedance ∞ is considered a first line. Furthermore, a line passing two points along an outer periphery of the Smith chart, with a phase at each point being 90°, and passing a point of impedance 1 (i.e., the reference impedance point), is considered a second line. Four regions divided by the first and second lines, which are perpendicular to each other, are defined as the first, second, third, and fourth quadrants. The first quadrant is a region exhibiting inductive reactance and a large impedance. The second quadrant is a region exhibiting inductive reactance and a small impedance. The third quadrant is a region exhibiting capacitive reactance and a small impedance.The fourth quadrant is an area that exhibits capacitive reactance and high impedance.

[0029] In Fig. 2 ZLNA(fn) represents an impedance at a specific frequency, different from the fundamental frequency of the received signal and becoming noise, in a state where the phase-adjusting circuit 30 is not used, when viewed from the Rx filter 22 towards the side of the low-noise amplifier LNA. The term "specific frequency" means a frequency that differs from the fundamental frequency of the received signal and becomes noise, which is picked up and amplified by the low-noise amplifier LNA. ZRX(fn) represents an impedance at the specific frequency in the state where the phase-adjusting circuit 30 is not used, when viewed from the low-noise amplifier LNA towards the side of the Rx filter 22.ZRXc1 (fn) represents a first impedance at the specific frequency in the state where the phase-adjusting circuit 30 is used, as viewed from the low-noise amplifier LNA towards the side of the Rx filter 22. ZRXc2 (fn) represents a second impedance at the specific frequency in the state where the phase-adjusting circuit 30 is used, as viewed from the low-noise amplifier LNA towards the side of the Rx filter 22. ZRX (fr0) represents an impedance at the fundamental frequency of the received signal in the state where the phase-adjusting circuit 30 is not used, as viewed from the Rx filter 22 towards the side of the low-noise amplifier LNA. ZRXc2 (fr0) represents an impedance at the fundamental frequency of the received signal in the state in which the phase adjustment circuit 30 is used, when viewed from the Rx filter 22 towards the side of the low-noise amplifier LNA.

[0030] As in Fig. As illustrated in Figure 2, if the phase of the impedance ZLNA(fn) differs from the fundamental frequency of the received signal at the specific frequency when viewed from the Rx filter 22 towards the side of the low-noise amplifier LNA, and if the phase of the impedance ZRX(fn) at the specific frequency, when viewed from the low-noise amplifier LNA towards the side of the Rx filter 22, is present in the conjugate quadrant, the phase adjustment circuit 30 performs a phase shift. More precisely, the impedance ZRX(fn) is shifted to the quadrant that is not conjugate to the quadrant where the impedance ZLNA(fn) is present, as denoted by the impedances ZRXc1(fn) and ZRXc2(fn).

[0031] Thus, at the specific frequency, which differs from the fundamental frequency of the received signal, the low-noise amplifier LNA and the Rx filter 22 are kept in a state of impedance mismatch. Accordingly, noise at this specific frequency is not fed from the Rx filter 22 into the low-noise amplifier LNA. Consequently, it is prevented that the relevant noise, for example, from the Tx filter 21, enters the low-noise amplifier LNA or is reflected by the antenna and flows through the Rx filter 22 into the low-noise amplifier LNA. This prevents any degradation in the received sensitivity.

[0032] Furthermore, as in Fig. As illustrated in Figure 2, the phase adjustment circuit 30 allows the impedance at the fundamental frequency of the received signal to be adjusted to approximate the reference impedance (100 Ω). Consequently, transmission loss of the received signal can be further reduced and the deterioration of the receiver sensitivity can be more effectively suppressed.

[0033] To perform the phase shift as described above, the phase adjustment circuit 30, for example, has a Fig. 3 illustrated circuit configurations. Fig. Figure 3 is an equivalent circuit diagram illustrating an example of the phase adjustment circuit according to the first example.

[0034] The phase adjustment circuit 30 comprises inductors 311P and 311N. Inductor 311P is connected between a lead electrode for one of the balanced lines connecting the Rx filter 22 and the low-noise amplifier LNA, and ground. Inductor 311N is connected between a lead electrode for the other balanced line connecting the Rx filter 22 and the low-noise amplifier LNA, and ground. The respective inductances of inductors 311P and 311N are adjusted to provide a first or second phase shift, as shown in Fig. 2 illustrates how to execute the instructions.

[0035] The inductors 311P and 311N can each be implemented with an electrode structure formed on a substrate or with an attached electronic component. When the inductors 311P and 311N are implemented with the electrode structures, the phase-setting circuit 30 and the high-frequency front-end circuit 10 can be implemented in a simple configuration. On the other hand, when the inductors 311P and 311N are implemented with attached electronic components, the inductances can be easily changed by replacing the attached electronic components, thus simplifying inductance adjustment.

[0036] Accordingly, a desired amount of phase shift can be obtained with higher accuracy.

[0037] The phase adjustment circuit can have a circuit configuration as described below. Fig. Figure 4 is an equivalent circuit illustrating another example of the phase-setting circuit according to the first example. A phase-setting circuit 30' comprises inductors 312P and 312N and capacitors 313P and 313N.

[0038] The inductor 312P is connected in series at an intermediate position of the lead electrode for one of the symmetrical leads connecting the Rx filter 22 and the low-noise amplifier LNA. The capacitor 313P is connected between an end section of the inductor 312P on the side closer to the low-noise amplifier LNA and ground.

[0039] The inductor 312N is connected in series at an intermediate position of the lead electrode for the other of the symmetrical leads that connect the Rx filter 22 and the low-noise amplifier LNA. The capacitor 313N is connected between an end section of the inductor 312N on the side closer to the low-noise amplifier LNA and ground.

[0040] With the configuration described above, as in Fig. As illustrated in section 5, one direction of the phase shift is that which in the case of Fig. 2 opposite. Fig. Figure 5 shows the Smith chart, which is referenced to illustrate the principle of another example of the high-frequency front-end circuit according to the first example. Furthermore, in this case, as in Fig. Figure 5 illustrates that if a phase of impedance ZLNA(fn) at the specific frequency, when viewed from the Rx filter 22 towards the side of the low-noise amplifier LNA, and a phase of impedance ZRX(fn) at the specific frequency, when viewed from the low-noise amplifier LNA towards the side of the Rx filter 22, are present in the conjugate quadrant, the phase adjustment circuit 30' performs the phase shift. Thus, impedance ZRX(fn) is shifted to the quadrant that is not conjugate to the quadrant in which impedance ZLNA(fn) is present, as denoted by impedance ZRXc1'(fn).

[0041] The phase shift mentioned above can be used to reduce the rate of deterioration of receiver sensitivity in a similar way.

[0042] Preferably, at the specific frequency, which differs from the fundamental frequency of the received signal, the phase of the impedance, as viewed from the Rx filter 22 towards the side of the low-noise amplifier LNA, and the phase of the impedance, as viewed from the low-noise amplifier LNA towards the side of the Rx filter 22, are present in the quadrants that exist on the same side with respect to the Reiner resistance line (first line) and that exist on opposite sides with respect to the second line. By maintaining both phases in such a relationship, the degree of impedance mismatch between the Rx filter 22 and the low-noise amplifier LNA at the specific frequency can be increased. Consequently, crosstalk of noise to the low-noise amplifier LNA can be suppressed with greater reliability, and the rate of degradation of the received sensitivity can be further reduced.

[0043] A high-frequency front-end circuit according to an embodiment of the present invention is described below with reference to the drawings. Fig. Figure 6 is a block diagram of the high-frequency front-end circuit according to the embodiment of the present invention. This embodiment represents an example in which a second harmonic frequency of a second transmit signal and a fundamental frequency of a first receive signal are close to each other, and further represents the case in which carrier aggregation is performed, whereby the transmission of the second transmit signal and the reception of the first receive signal are carried out at the same time.

[0044] As in Fig. As illustrated in Figure 6, the high-frequency front-end circuit of the exemplary embodiment features a triplexer configuration instead of the duplexer configuration used in the first example.

[0045] As in Fig. As illustrated in Figure 6, the high-frequency front-end circuit designated 10A comprises a triplexer 20A, a phase-adjustment circuit 30A, and a low-noise amplifier LNA. The triplexer 20A comprises a Tx1 filter 211, corresponding to a transmit filter in a "first communication band" of the present invention, a Tx2 filter 212, corresponding to a transmit filter in a "second communication band" of the present invention, and an Rx1 filter 221, corresponding to a receive filter in the "first communication band" of the present invention.

[0046] One end of the Tx1 filter 211, one end of the Tx2 filter 212, and one end of the Rx1 filter 221 are connected together. This connection point is connected to an antenna or an antenna-side circuit (not illustrated). The antenna serves to transmit a signal that has passed through the Tx1 filter 211 or the Tx2 filter 212 to the outside and to receive a signal from the outside.

[0047] The Tx1 filter 211 is configured such that the fundamental frequency of a transmitted signal in the first communication band falls within a passband of the Tx1 filter 211. The Tx2 filter 212 is configured such that the fundamental frequency of a transmitted signal in the second communication band falls within a passband of the Tx2 filter 212. The other end of the Tx1 filter 211 is connected to a power amplifier PA1. The other end of the Tx2 filter 212 is connected to a power amplifier PA2. An impedance matching circuit can be arranged here to perform impedance matching at the fundamental frequency of the transmitted signal in the corresponding communication band, either between the Tx1 filter 211 and the power amplifier PA1 or between the Tx2 filter 212 and the power amplifier PA2.

[0048] The Rx1 filter 221 is configured such that a fundamental frequency of the received signal in the first communication band falls within a passband of the Rx1 filter 221. The Rx1 filter 221 is configured to provide a predetermined attenuation of the fundamental frequency of both the transmitted signal in the first communication band and the transmitted signal in the second communication band. The Rx1 filter 221 features unbalanced-to-balanced conversion. The other end of the Rx1 filter 221 is connected to the low-noise amplifier LNA via the phase-adjustment circuit 30A.

[0049] The phase adjustment circuit 30A has a circuit configuration to perform impedance matching between the Rx1 filter 221 and the low-noise amplifier LNA in a fundamental frequency band of the received signal. The circuit configuration of the phase adjustment circuit 30A is implemented based on the principle described below. Fig. Figure 7 shows the Smith chart, which is referenced to explain the principle of the high-frequency front-end circuit according to the second embodiment of the present invention. The diagram in Fig. The illustrated Smith chart is similar to the one in Fig. 2 illustrated Smith chart and is divided into four quadrants according to the same concept as in Fig. Divided into 2.

[0050] In Fig. 7 ZLNA (ft2) represents an impedance at a second harmonic frequency of the transmitted signal in the second communication band in a state where the phase-adjusting circuit 30A is not used, as viewed from the Rx1 filter 221 towards the side of the low-noise amplifier LNA. ZRX (ft2) represents an impedance at the second harmonic frequency of the transmitted signal in the second communication band in the state where the phase-adjusting circuit 30A is not used, as viewed from the low-noise amplifier LNA towards the side of the Rx1 filter 221. ZRXc1 (ft2) represents a first impedance at the second harmonic frequency of the transmitted signal in the second communication band in the state where the phase-adjusting circuit 30A is used, as viewed from the low-noise amplifier LNA towards the side of the Rx1 filter 221.ZRXc2 (ft2) represents a second impedance at the second harmonic frequency of the transmitted signal in the second communication band when the phase-adjusting circuit 30A is used, viewed from the low-noise amplifier LNA towards the side of the Rx1 filter 221. ZRX (fr1) represents an impedance at the fundamental frequency of the received signal in the second communication band when the phase-adjusting circuit 30A is not used, viewed from the Rx1 filter 221 towards the side of the low-noise amplifier LNA. ZRXc2 (fr1) represents an impedance at the fundamental frequency of the received signal in the second communication band when the phase-adjusting circuit 30A is used, viewed from the Rx1 filter 221 towards the side of the low-noise amplifier LNA.

[0051] As in Fig. As illustrated in Figure 7, if a phase of impedance ZLNA (ft2) at the second harmonic frequency of the transmitted signal in the second communication band, as viewed from the Rx1 filter 221 towards the side of the low-noise amplifier LNA, and a phase of impedance ZRX (ft2) at the second harmonic frequency of the transmitted signal in the second communication band, as viewed from the low-noise amplifier LNA towards the side of the Rx1 filter 221, are present in the conjugate quadrant, the phase-adjusting circuit 30A shifts the phase of impedance ZRX (ft2). More precisely, impedance ZRX (ft2) is shifted to the quadrant that is not conjugate to the quadrant in which impedance ZLNA (ft2) is present, as denoted by impedances ZRXc1 (ft2) and ZRXc2 (ft2).

[0052] Thus, at the second harmonic frequency of the transmitted signal in the second communication band, the Rx1 filter 221 and the low-noise amplifier LNA are kept in a state of impedance mismatch. Accordingly, a signal at the second harmonic frequency of the transmitted signal in the second communication band is not fed from the Rx1 filter 221 to the low-noise amplifier LNA. Consequently, the signal is prevented from flowing into the low-noise amplifier LNA at the second harmonic frequency of the transmitted signal in the second communication band, and the degradation of the receive sensitivity for the received signal in the first communication band can be prevented, even in the case where carrier aggregation is performed.

[0053] Furthermore, as in Fig.As illustrated in Figure 7, the phase adjustment circuit 30A allows the impedance at the fundamental frequency of the received signal in the first communication band to be adjusted to approximate the reference impedance (100 Ω) of the balanced lines. Accordingly, transmission loss of the received signal in the first communication band can be further reduced, and the deterioration of the receiver sensitivity can be more effectively suppressed.

[0054] As described above, by implementing the configuration of this embodiment, the degradation rate of the receive sensitivity for the received signal itself can be reduced, provided that the harmonic frequency of the transmitted signal and the fundamental frequency of the received signal are close to each other when the transmitted and received signals are sent and received according to carrier aggregation.

[0055] Although the above description was made in connection with the case in which the fundamental frequency of the received signal in the first communication band and the second harmonic frequency of the transmitted signal in the second communication band are close to each other, similar advantageous effects as those in that case can also be obtained by using the configuration described above if it is unavoidable that a high-frequency signal, which differs from the fundamental frequency of the received signal in the first communication band, is fed into the low-noise amplifier LNA. Reference symbol list 10, 10A High-Frequency Front-End Circuit 20 Duplexers 20A Triplexer 21 Tx filters 211 Tx1 filter 212 Tx2 filter 22 Rx filters 221 Rx1 filter 30, 30', 30A Phase adjustment circuit 80 transmitting circuit 311P, 311N, 312P, 312N inductor 313P, 313N capacitor LNA low-noise amplifier PA, PA1, PA2 Power Amplifiers

Claims

[1] A high-frequency front-end circuit (10A) having the following features: a triplexer circuit (20A) comprising a first transmit filter (211), a receive filter (221) and a second transmit filter (212), wherein one end of the first transmit filter (211) and one end of the receive filter (221) and one end of the second transmit filter (212) are connected to each other by a common junction; a low-noise amplifier (LNA); and a phase adjustment circuit (30A) that is connected between the receive filter (221) and the low-noise amplifier (LNA), where the first transmit filter (211) is set such that a fundamental frequency of a first transmit signal in a first communication band falls into a passband of the first transmit filter (211), the receive filter (221) is set such that a fundamental frequency of a received signal in the first communication band falls into a passband of the receive filter (221), the second transmit filter (212) is set such that a fundamental frequency of a second transmit signal in a second communication band, which differs from the first communication band, falls into a passband of the second transmit filter (212), where the transmission of the second transmit signal and the reception of the received signal are carried out simultaneously, wherein, assuming that a Smith chart is divided into four quadrants by a first line representing pure resistance and by a second line connecting points along an outer periphery of the Smith chart, each with a phase of 90°, and a reference impedance point, the phase adjustment circuit (30A) performs a phase adjustment such that, at a harmonic frequency of the second transmit signal, a quadrant in which a phase of the low-noise amplifier (LNA) is present when viewed from the receive filter (221), and a quadrant in which a phase is present when viewed from the low-noise amplifier (LNA) towards the receive filter (221), are not in a conjugate relationship. [2] The high-frequency front-end circuit (10A) according to claim 1, wherein the harmonic frequency is a second harmonic frequency of the second transmit signal. [3] The high-frequency front-end circuit (10A) according to claim 1 or 2, wherein the phase adjustment circuit (30A) performs a phase adjustment such that at the harmonic frequency the quadrant in which the phase of the low-noise amplifier (LNA) is present when viewed from the receive filter (221) and the quadrant in which the phase is present when viewed from the low-noise amplifier (LNA) towards the receive filter (221) are arranged on opposite sides of the second line. [4] The high-frequency front-end circuit (10A) according to any one of claims 1 to 3, wherein the phase adjustment circuit (30A) performs the phase adjustment such that an impedance at the fundamental frequency of the received signal is set to approximate the reference impedance. [5] The high-frequency front-end circuit (10A) according to any one of claims 1 to 4, wherein the phase-setting circuit (30A) comprises at least one electronic component of the attached type having a reactance component. [6] The high-frequency front-end circuit (10A) according to any one of claims 1 to 5, wherein the phase adjustment circuit (30A) performs the phase adjustment for a signal at the specific frequency based on the length of a transmission line over which the received signal is transmitted.

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