High-frequency amplifier

Abstract

This high-frequency amplifier is provided with: a high-frequency input terminal; a high-frequency output terminal; a plurality of amplifiers each having a transistor and connected in series; a stabilization circuit provided in at least two amplifiers among the plurality of amplifiers; a first band elimination filter; each of the stabilization circuits has a band-pass filter and a first resistor connected in parallel to the band-pass filter, each of the first band-excluding filters has a first resonant frequency, each of the output bias circuits has a second band-excluding filter having a second resonant frequency, and each of the first and second band-excluding filters has a second resonant frequency. In the at least two amplifiers, the first resonant frequency and the second resonant frequency differ from each other and are lower than the frequency used as the amplifier, or the first resonant frequency and the second resonant frequency differ from each other and are higher than the frequency used as the amplifier.

Description

Technical Field

[0001] The present disclosure relates to a high-frequency amplifier. Background Art

[0002] A high-frequency multi-stage low-noise amplifier is disclosed in Patent Document 1. The high-frequency multi-stage low-noise amplifier includes: a high-frequency input terminal, a high-frequency output terminal, and a multi-stage circuit provided between the high-frequency input terminal and the high-frequency output terminal. In the multi-stage circuit, two or more amplifiers each having an input matching circuit, a transistor, and an output matching circuit are connected in series. In at least two of the amplifiers in the multi-stage circuit, a stabilization circuit in which a band-pass filter is connected in parallel with a resistor, and a band rejection filter that excludes a frequency band lower than the operating frequency of the amplifier are provided. The stabilization circuit and the band rejection filter are provided between the output terminal of the transistor of the amplifier to which they belong and the output matching circuit, or inside the output matching circuit. The resonance frequency of the band-pass filter is lower the closer it is to the high-frequency input terminal.

[0003] Patent Document 1: International Publication No. 2022 / 024189

[0004] Generally, in a high-frequency low-noise amplifier, it is necessary to reduce the noise of the amplified output high-frequency power and to have stability from the low frequency to the high frequency of the operating band. In particular, in satellite communication or terrestrial base station communication, etc., in order to ensure communication quality, it is sometimes required to improve the distortion characteristics of the amplifier, eliminate unnecessary waves, etc. For such purposes, it is sometimes necessary to suppress the gain of a frequency band different from the operating band, that is, the rejection band, which is near the operating band of the amplifier. In the high-frequency amplifier of Patent Document 1, the gain of the rejection band can be suppressed, and the through-loss from the low-frequency end to the high-frequency end of the operating band can be reduced. Therefore, a low noise figure can be obtained over a wide band, and the gain flatness in the operating band can be improved.

[0005] In order to reduce the gain of the rejection band in the high-frequency amplifier of Patent Document 1, the attenuation amount is increased by the band rejection filter. When the required attenuation amount or attenuation bandwidth becomes large, for example, it may be necessary to arrange a plurality of inductors and capacitors constituting the band rejection filter.

[0006] Generally, if a band rejection filter is arranged, circuit loss occurs at the resonance frequency of the band rejection filter, and the gain of the amplifier attenuates at the resonance frequency. However, in reality, it is impossible to attenuate the gain only at a single frequency. Therefore, circuit loss also occurs in the operating band, which affects the gain or noise figure in the operating band of the amplifier. As a result, it is possible to increase the circuit loss and deteriorate the noise figure at the band edge of the operating band. In addition, it is possible to deteriorate the flatness of the gain in the operating band.

[0007] For example, in an amplifier with an operating frequency band of 14 to 16 GHz, when a band rejection filter centered at 13 GHz is provided in the vicinity thereof, the gain at 13 GHz can be reduced. However, the attenuation characteristic of the filter decreases with frequency extension. Therefore, circuit losses will also occur within the operating frequency band. In the above example where the rejection band is lower than the operating frequency band, at 14 GHz, which is the low-frequency end of the operating frequency band, a reduction in gain and a deterioration in noise figure may occur.

[0008] To further increase the attenuation amount or attenuation bandwidth of the rejection band from this state, it is considered to add another band rejection filter centered at 13 GHz. Additionally, for example, it is considered to provide a band rejection filter centered at 12.8 GHz and a band rejection filter centered at 13.2 GHz instead of the band rejection filter centered at 13 GHz. In this case, at 14 GHz, which is the low-frequency end of the operating frequency band, the gain will be further reduced and the noise figure may deteriorate. Summary of the Invention

[0009] An object of the present disclosure is to obtain a high-frequency amplifier that can suppress a decrease in gain or a deterioration in noise figure within the operating frequency band and improve the attenuation amount or attenuation bandwidth within the rejection band.

[0010] The high-frequency amplifier of the present disclosure includes: a high-frequency input terminal; a high-frequency output terminal; a plurality of amplifiers disposed between the high-frequency input terminal and the high-frequency output terminal, each having a transistor and connected in series; a stabilization circuit disposed in at least two of the plurality of amplifiers; a first band rejection filter disposed in the at least two amplifiers; and an output bias circuit disposed in the at least two amplifiers to supply a bias to the output terminal of the corresponding transistor. Each of the stabilization circuits includes: a band-pass filter and a first resistor connected in parallel with the band-pass filter, and is disposed between the output terminal of the corresponding transistor and the high-frequency output terminal. Each of the first band rejection filters has a first resonance frequency and is disposed between the output terminal of the corresponding transistor and the high-frequency output terminal. Each of the output bias circuits includes a second band rejection filter having a second resonance frequency. In the at least two amplifiers, the first resonance frequency and the second resonance frequency are different from each other and lower than the operating frequency of the amplifier, or the first resonance frequency and the second resonance frequency are different from each other and higher than the operating frequency of the amplifier.

[0011] In the high-frequency amplifier of the present disclosure, by means of the first band rejection filter and the second band rejection filter, it is possible to suppress the reduction of the gain or the deterioration of the noise figure in the used band, and to increase the attenuation amount or the attenuation bandwidth in the rejection band. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram for explaining the structure of the high-frequency amplifier of Embodiment 1.

[0013] Figure 2 It is a diagram showing the change of the gain of the stabilization circuit with respect to frequency.

[0014] Figure 3 It is a diagram showing the change of the gain of the output bias circuit with respect to frequency.

[0015] Figure 4 It is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit of the amplifier in the front stage of Embodiment 1.

[0016] Figure 5 It is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit of the amplifier in the rear stage of Embodiment 1.

[0017] Figure 6 It is a diagram showing the gain of the first band rejection filter of Embodiment 1.

[0018] Figure 7 It is a diagram showing the gain of the high-frequency amplifier of Embodiment 1.

[0019] Figure 8 It is a diagram showing the noise figure of the high-frequency amplifier of Embodiment 1.

[0020] Figure 9 It is a diagram for explaining the structure of the high-frequency amplifier of Embodiment 2.

[0021] Figure 10 It is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit of the amplifier in the front stage of Embodiment 2.

[0022] Figure 11 It is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit of the amplifier in the rear stage of Embodiment 2.

[0023] Figure 12 It is a diagram showing the gain of the high-frequency amplifier of Embodiment 2.

[0024] Figure 13 It is a diagram showing the noise figure of the high-frequency amplifier of Embodiment 2.

[0025] Figure 14This is a diagram showing the structure of the high-frequency amplifier according to Embodiment 4.

[0026] Figure 15 This is a diagram showing the structure of the high-frequency amplifier according to Embodiment 5.

[0027] Figure 16 This is a diagram showing the structure of the high-frequency amplifier according to Embodiment 6. Detailed Embodiments

[0028] The high-frequency amplifiers of the respective embodiments will be described with reference to the accompanying drawings. The same or corresponding components are denoted by the same reference numerals, and repeated descriptions may be omitted sometimes.

[0029] Embodiment 1.

[0030] Figure 1 This is a diagram showing the structure of the high-frequency amplifier 100 according to Embodiment 1. The high-frequency amplifier 100 is also referred to as a high-frequency multi-stage low-noise amplifier. The high-frequency amplifier 100 is, for example, a high-frequency power amplifier that amplifies high-frequency power such as microwaves or millimeter waves.

[0031] The high-frequency amplifier 100 includes: a high-frequency input terminal T1, a high-frequency output terminal T6, and a multi-stage circuit provided between the high-frequency input terminal T1 and the high-frequency output terminal T6. The high-frequency input terminal T1 is a terminal for inputting high-frequency power to the high-frequency amplifier 100. The high-frequency output terminal T6 is an output terminal of the high-frequency amplifier 100. The multi-stage circuit includes a plurality of amplifiers connected in series. Each amplifier has an input matching circuit M1, M3, transistors Tr1, Tr2, and an output matching circuit M2, M4. Although two amplifiers are shown in Figure 1 , the multi-stage circuit may connect two or more amplifiers in series, and the number of amplifiers is not limited.

[0032] In Figure 1 's example, the first-stage amplifier has: an input matching circuit M1, an input bias circuit B1, an input bias power supply terminal T2, a transistor Tr1, and a source inductor SI1. The first-stage amplifier also has: a stabilization circuit S1, a first band rejection filter BRFm1, an output bias circuit B2, an output bias power supply terminal T3, and an output matching circuit M2. The first-stage amplifier and the second-stage amplifier are connected by an inter-stage capacitor C. The second-stage amplifier has: an input matching circuit M3, an input bias circuit B3, an input bias power supply terminal T4, a transistor Tr2, and a source inductor SI2. The second-stage amplifier also has: a stabilization circuit S2, a first band rejection filter BRFm2, an output bias circuit B4, an output bias power supply terminal T5, and an output matching circuit M4.

[0033] Thus, each part from the input matching circuit M1 to the output matching circuit M2 forms a first-stage amplifier when observed from the high-frequency input terminal T1 side. The input matching circuit M1 is the input-side matching circuit of the transistor Tr1. The input bias circuit B1 is a circuit that applies a bias voltage to the gate terminal of the transistor Tr1. The input bias power supply terminal T2 is a power supply terminal for supplying power to the input bias circuit B1. The transistor Tr1 is an amplification element that amplifies high-frequency power. One end of the source inductor SI1 is connected to the source terminal of the transistor Tr1, and the other end of the source inductor SI1 is grounded.

[0034] The stabilization circuit S1 is provided between the transistor Tr1 and the output matching circuit M2. The stabilization circuit S1 includes: a band-pass filter BPF1 and a resistor Rs1 connected in parallel with the band-pass filter BPF1. The band-pass filter BPF1 is, for example, a series resonance circuit of an inductor Ls1 and a capacitor Cs1 that resonates at a frequency fs1. The stabilization circuit S1 can be provided between the output terminal of the transistor Tr1 belonging to the same amplifier and the output matching circuit M2, or inside the output matching circuit M2. That is, the stabilization circuit S1 can be provided between the output terminal of the corresponding transistor Tr1 and the high-frequency output terminal T6 within the first-stage amplifier.

[0035] The first band-rejection filter BRFm1 is provided between the transistor Tr1 and the output matching circuit M2. The first band-rejection filter BRFm1 is composed of a series resonance circuit of an inductor Lr1 and a capacitor Cr1 that resonates at a frequency fr. The series resonance circuit is shunt-connected. Hereinafter, the resonance frequency fr of the first band-rejection filter BRFm1 is sometimes referred to as the first resonance frequency. The first band-rejection filter BRFm1 can be provided between the output terminal of the transistor Tr1 belonging to the same amplifier and the output matching circuit M2, or inside the output matching circuit M2. That is, the first band-rejection filter BRFm1 can be provided between the output terminal of the corresponding transistor Tr1 and the high-frequency output terminal T6 within the first-stage amplifier.

[0036] The stabilization circuit S1 and the first band-stop filter BRFm1 are connected in series with the stabilization circuit S1 and the first band-stop filter BRFm1 in sequence, and are connected in parallel to the output terminal of the transistor Tr1. The order of the stabilization circuit S1 and the first band-removing filter BRFm1 can also be reversed.

[0037] The output bias circuit B2 is a circuit that supplies a bias to the output terminal of the transistor Tr1. The output bias circuit B2 is provided between the output terminal of the corresponding transistor Tr1 and the output bias power supply terminal T3. The output bias circuit B2 includes: a second band rejection filter BRFb1, and a resistor Rb1 connected in series with the second band rejection filter BRFb1. In the output bias circuit B2, the resistor Rb1 and the inductor Lb1 are connected in series with respect to the bias path to the transistor Tr1. In addition, the capacitor Cb1 is connected in shunt with respect to the bias path. The inductor Lb1 functions as a power path for imparting a bias voltage. In addition, the inductor Lb1 and the capacitor Cb1 together form the second band rejection filter BRFb1 that resonates at the frequency fb. Hereinafter, the resonance frequency fb of the second band rejection filter BRFb1 may sometimes be referred to as the second resonance frequency.

[0038] The output bias power supply terminal T3 is a power supply terminal for supplying power to the output bias circuit B2 and supplying a bias to the output terminal of the transistor Tr1. The output matching circuit M2 is an output side matching circuit for the transistor Tr1. The inter-stage capacitor C is a DC cut-off capacitor that blocks DC current from the output matching circuit M2 and the input matching circuit M3.

[0039] When viewed from the high-frequency input terminal T1 side, each part from the input matching circuit M3 to the output matching circuit M4 forms a second-stage amplifier. The structure of the second-stage amplifier is the same as that of the first-stage amplifier. The stabilization circuit S2 includes a band-pass filter BPF2 and a resistor Rs2 connected in parallel with the band-pass filter BPF2. The band-pass filter BPF2 is, for example, a series resonance circuit of an inductor Ls2 and a capacitor Cs2 that resonates at the frequency fs2.

[0040] The first band rejection filter BRFm2 is formed by a series resonance circuit of an inductor Lr2 and a capacitor Cr2 that resonates at the frequency fr. This series resonance circuit is connected in shunt. The inductor Lr2, for example, has the same inductance as the inductor Lr1. The capacitor Cr2, for example, has the same capacitance value as the capacitor Cr1. Therefore, the resonance frequency of the first band rejection filter BRFm2 is equal to the resonance frequency fr of the first band rejection filter BRFm1.

[0041] The output bias circuit B4 is a circuit that supplies a bias to the output terminal of the transistor Tr2. The output bias circuit B4 includes: a second band rejection filter BRFb2, and a resistor Rb2 connected in series with the second band rejection filter BRFb2. In the output bias circuit B4, the resistor Rb2 and the inductor Lb2 are connected in series with respect to the bias path to the transistor Tr2. In addition, the capacitor Cb2 is connected in shunt with respect to the bias path. The inductor Lb2 and the capacitor Cb2 form the second band rejection filter BRFb2 that resonates at the frequency fb. The resistor Rb2 has, for example, the same resistance value as the resistor Rb1. The inductor Lb2 has, for example, the same inductance as the inductor Lb1. The capacitor Cb2 has, for example, the same capacitance value as the capacitor Cb1. Therefore, the resonance frequency of the second band rejection filter BRFb2 is equal to the resonance frequency fb of the second band rejection filter BRFb1.

[0042] Let the center value of the frequency used as the amplifier, that is, the center value of the frequency band used as the amplifier, be fc. The relationships among the resonance frequencies fs1, fs2 of the band-pass filters BPF1, BPF2, the first resonance frequency fr, and the second resonance frequency fb are as follows.

[0043] fb < fr ≤ fs1 < fc < fs2

[0044] The first resonance frequency fr is lower than the use frequency fc. The resonance frequencies fs1, fs2 of the band-pass filters BPF1, BPF2 are lower the closer they are to the high-frequency input terminal T1.

[0045] In a low-noise amplifier, a source inductor is often used to achieve stability in the used frequency band. However, due to the loading of the source inductor, the stability on the high-frequency side of the used frequency band may sometimes be impaired. Therefore, not only for the low-frequency side but also for the high-frequency side of the used frequency band, it is necessary to insert a stabilization circuit for the loss. In addition, it is necessary to achieve stabilization for each stage of the transistor. Therefore, the stabilization circuit S1 and the stabilization circuit S2 are preferably not connected in series continuously. Therefore, the stabilization circuit S1 can be provided between the output terminal of the transistor Tr1 and the output matching circuit M2, or inside the output matching circuit M2. In addition, the stabilization circuit S2 can be provided between the output terminal of the transistor Tr2 and the output matching circuit M4, or inside the output matching circuit M4.

[0046] In addition, it is preferable that the first band rejection filters BRFm1 and BRFm2 are not connected in continuous series. Therefore, the first band rejection filter BRFm1 can be disposed between the output terminal of the transistor Tr1 and the output matching circuit M2, or inside the output matching circuit M2. Additionally, the first band rejection filter BRFm2 can be disposed between the output terminal of the transistor Tr2 and the output matching circuit M4, or inside the output matching circuit M4. Thereby, over-input of high-frequency power can be prevented for all of the transistors Tr1 and Tr2, and the distortion characteristics can be improved for each amplification stage.

[0047] Of course, the output bias circuit B2 and the output bias circuit B4 respectively serve to apply a bias voltage to the output terminals of the transistor Tr1 and the transistor Tr2, and thus are not connected continuously.

[0048] In the above structure, the LC series resonance circuit in the stabilization circuit S1 functions as a band-pass filter BPF1 that passes the power at the frequency fs1. Figure 2 It is a diagram showing the change of the gain of the stabilization circuit with respect to the frequency. Figure 2 The vertical axis represents the gain of the stabilization circuit. The circuit loss corresponds to Figure 2 the absolute value of the negative value in

[0049] When the LC series resonance circuit is connected in parallel with the resistor Rs1, the resonance circuit functions as a band-pass filter at the resonance frequency fs1, and the passing loss is ideally zero. On the other hand, when the frequency is far from fs1, the input power propagates via the resistor Rs1. Therefore, the circuit loss becomes large, and stabilization can be achieved.

[0050] The resistance value of the resistor Rs1 is arbitrarily set according to the value of the passing loss required from near the frequency fs1 to far away. Figure 2 The dashed line in

[0051] Figure 2The dashed line in [Fig. 0] represents the gain when the resistance value of the resistor Rs1 is reduced from the reference value to the extent of the circuit loss required to maintain at a distance from the frequency fs1. At this time, the ratio of the input power propagated through the resistor Rs1 is larger than that of the input power propagated through the LC series resonance circuit. Therefore, the circuit loss of the entire stabilization circuit S1 at frequencies near fs1 other than fs1 is larger than the circuit loss of the reference value.

[0052] Similarly, the LC series resonance circuit in the stabilization circuit S2 functions as a band-pass filter BPF2 that allows the power at the resonance frequency fs2 to pass through. At the frequency fs2, the resonance circuit acts as a band-pass filter, and the loss is ideally zero. On the other hand, when the frequency is far from fs2, the input power is propagated through the resistor Rs2. Therefore, the circuit loss increases, and stabilization can be achieved.

[0053] Similar to the resistor Rs1, the resistance value of the resistor Rs2 is arbitrarily set according to the value of the pass loss required from near the frequency fs2 to a distance. The resistance value of the resistor Rs2 is, for example, the same as the resistance value of the resistor Rs1. The circuit loss of the entire stabilization circuit S2 varies according to the value of the resistor Rs2 as shown in Figure 2 shown.

[0054] The first band rejection filters BRFm1 and BRFm2 both reject the power of the frequency fr input from the high-frequency input terminal T1 and output to the high-frequency output terminal T6. The circuit losses of the first band rejection filters BRFm1 and BRFm2 have a frequency characteristic that is maximum at the frequency fr and decreases as it extends from near it to a distance.

[0055] The second band rejection filters BRFb1 and BRFb2 both reject the power of the frequency fb input from the high-frequency input terminal T1 and output to the high-frequency output terminal T6. The circuit losses of the second band rejection filters BRFb1 and BRFb2 have a frequency characteristic that is maximum at the frequency fb and decreases as it extends from near it to a distance.

[0056] The output bias circuit B2 functions as a band rejection filter that applies a bias voltage to the output terminal of the transistor Tr1 and rejects the power of the frequency fb. At this time, the resistance value of the resistor Rb1 that constitutes the output bias circuit B2 is arbitrarily set according to the value of the pass loss required from near the frequency fb to a distance.

[0057] Figure 3 is a graph showing the change in the gain of the output bias circuit B2 with respect to frequency. Figure 3 The vertical axis of [Fig. 23] represents the gain of the output bias circuit B2, and the circuit loss corresponds to Figure 3 the absolute value of the negative value in Figure 2Similarly, the closer to the lower side of the vertical axis, the smaller the gain, that is, the greater the circuit loss.

[0058] Figure 3 The dotted line of represents the gain when the resistance value of the resistor Rb1 increases from the reference value to the degree of increase in the circuit loss in the allowable use frequency band. At this time, the frequency characteristics of the second band rejection filter BRFb1 become flat. Therefore, the circuit loss of the output bias circuit B2 at the frequency fb and frequencies near the frequency fb is less than the circuit loss of the reference value. In addition, the circuit loss of the output bias circuit B2 at frequencies far from the frequency fb is greater than the circuit loss of the reference value.

[0059] Figure 3 The dotted line of

[0058] represents the gain when the resistance value of the resistor Rb1 decreases from the reference value to the degree of decrease in the circuit loss in the allowable rejection frequency band. At this time, the frequency characteristics of the second band rejection filter BRFb1 become steep. Therefore, the circuit loss of the output bias circuit B2 at the frequency fb and frequencies near the frequency fb is greater than the circuit loss of the reference value. In addition, the circuit loss of the output bias circuit B2 at frequencies far from the frequency fb is greater than the circuit loss of the reference value.

[0060] Here, the frequency fb and the resistance value of the resistor Rb1 are set such that when the resistance value of the resistor Rb1 increases from the reference value, the circuit loss of the output bias circuit B2 in the use frequency band of the amplifier is greater than the original circuit loss. In addition, the frequency fb and the resistance value of the resistor Rb1 are set such that when the resistance value of the resistor Rb1 decreases from the reference value, the circuit loss of the output bias circuit B2 in the use frequency band of the amplifier is less than the original circuit loss.

[0061] Similarly, the output bias circuit B4 functions as a band rejection filter that gives a bias voltage to the output terminal of the transistor Tr2 and rejects the power of the frequency fb. The resistance value of the resistor Rb2 constituting the output bias circuit B4 is arbitrarily set according to the value of the passing loss required from near the frequency fb to far away. The circuit loss of the output bias circuit B4 when the resistance value of the resistor Rb2 increases or decreases from the reference value changes in the same way as the circuit loss in the output bias circuit B2.

[0062] The resistance values of the resistors Rs1, Rs2, Rb1, and Rb2 also serve to arbitrarily set the bias voltage applied to the output terminals of the transistors Tr1 and Tr2. Generally, under voltage conditions that ensure the reliability of the required components, a voltage that maximally exerts the performance of the transistor is applied to the transistor. In a low-noise amplifier, it is necessary to apply a voltage that optimizes characteristics such as the noise figure and gain to the output terminal of the transistor.

[0063] On the other hand, a voltage is applied from a power supply such as a module incorporated in the high-frequency amplifier 100 to the output bias power supply terminals T3 and T5. The voltage is reduced by the required amount through the resistors Rs1, Rs2, Rb1, and Rb2, and thus the respective resistor values are set so as to apply a desired voltage to the output terminals of the transistors Tr1 and Tr2.

[0064] Next, the effects of the second band rejection filters BRFb1 and BRFb2 on the gain flatness and noise figure in the used band, and the attenuation characteristics of the gain in the rejected band are described. Here, the case where the rejected band is lower than the used band, that is, the case where the first resonance frequency fr and the second resonance frequency fb are lower than the used frequency of the amplifier is described. Here, under the condition of fr < fs1 < fc < fs2, the following two cases are studied.

[0065] Case (1): The case where the second band rejection filter is not included in the output bias circuit

[0066] Case (2): The case where the second band rejection filter is included in the output bias circuit

[0067] Case (2) corresponds to this embodiment.

[0068] Regarding these cases, how the stabilization circuits S1 and S2, the first band rejection filters BRFm1 and BRFm2, the circuit losses generated in the output bias circuits B2 and B4, the gain flatness in the used band, and the noise figure change are described. Here, the used band is 14 to 16 GHz, and the center of the rejected band of the first band rejection filters BRFm1 and BRFm2 is 13 GHz. In addition, the center frequency of the power rejected by the second band rejection filters BRFb1 and BRFb2 is less than 13 GHz, and the frequency does not drop to the extent that there is a circuit loss at 13 GHz in GHz level.

[0069] Figure 4 It is a diagram showing the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 of the pre-stage amplifier of Embodiment 1. Figure 5 It is a diagram showing the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 of the post-stage amplifier of Embodiment 1. Figure 6 It is a diagram showing the gains of the first band rejection filters BRFm1 and BRFm2 of Embodiment 1.

[0070] The circuit losses of the stabilization circuits S1 and S2, the output bias circuits B2 and B4, and the first band rejection filters BRFm1 and BRFm2 are equivalent to Figures 4 - 6 the absolute value of the negative value of Figures 4 - 6In the calculation example, the resonance frequencies of the LC resonance circuits constituting the stabilization circuit are set such that the circuit loss of the stabilization circuit S1 becomes zero at 14 GHz and the circuit loss of the stabilization circuit S2 becomes zero at 16 GHz.

[0071] It is assumed that the attenuation amounts of the first band rejection filters BRFm1 and BRFm2 have a maximum value of 10 dB at 13 GHz and a circuit loss of 0.6 dB at 14 GHz in either of the cases (1) and (2). Additionally, it is assumed that the attenuation amounts of the second band rejection filters BRFb1 and BRFb2 have a maximum value at a frequency sufficiently lower than 13 GHz, and have a circuit loss of almost zero at 1.5 dB at 13 GHz and above 14 GHz. On the above premise, calculate the gain and noise figure of the high-frequency amplifier 100 assuming that the gain of each transistor is 10 dB regardless of the frequency, the noise figure is 0.6 dB, and there is no circuit loss other than the stabilization circuit, the output bias circuit, and the band rejection filter.

[0072] Figure 7 It is a graph showing the gain of the high-frequency amplifier 100 of Embodiment 1. In cases (1) and (2), the gain from the low-frequency end to the high-frequency end of the used band of the amplifier is almost the same. On the other hand, the attenuation amount near 13 GHz is larger in case (2). Additionally, in case (2), the attenuation bandwidth is wider than that in case (1). For example, the bandwidth with a gain of 5 dB or less in the rejection band is 0.3 GHz in case (1) and 0.6 GHz in case (2) of the present embodiment.

[0073] Figure 8 It is a graph showing the noise figure of the high-frequency amplifier 100 of Embodiment 1. In cases (1) and (2), the noise figure from the low-frequency end to the high-frequency end of the used band of the amplifier is almost the same.

[0074] Thus, in the present embodiment, by combining the first band rejection filter and the second band rejection filter, it is possible to suppress a decrease in gain or a deterioration in noise figure in the used band, and to increase the attenuation amount and the attenuation bandwidth in the rejection band. Generally, when increasing the band rejection filter, there is a concern that the gain in the used band also decreases. In contrast, in the present embodiment, from the low-frequency end to the high-frequency end of the used band, it is possible to maintain the same noise figure and gain deviation as before the increase of the band rejection filter.

[0075] In addition, in the present embodiment, by adding the second band rejection filters BRFb1 and BRFb2 with a simple structure, it is possible to increase the attenuation amount and the attenuation bandwidth in the rejection band. Therefore, an increase in the circuit scale can be suppressed.

[0076] In this embodiment, the second resonance frequency fb is lower than the first resonance frequency fr. That is, it is assumed that the frequencies excluded by the second band rejection filters BRFb1 and BRFb2 are lower than the frequencies excluded by the first band rejection filters BRFm1 and BRFm2. However, it is not limited to this, and the second resonance frequency fb may also be higher than the first resonance frequency fr. That is, the first resonance frequency fr and the second resonance frequency fb may be different from each other and lower than the operating frequency fc of the amplifier. For example, even if the first resonance frequency fr is set to a value lower than the center frequency 13 GHz of the rejection band and the second resonance frequency fb is set to 13 GHz, the effects of this embodiment can be obtained.

[0077] The above modifications can be appropriately applied to the high-frequency amplifier of the following embodiments. In addition, for the high-frequency amplifier of the following embodiments, there are many common points with Embodiment 1, so the description will focus on the differences from Embodiment 1.

[0078] Embodiment 2.

[0079] Figure 9 FIG. is a diagram for explaining the structure of the high-frequency amplifier 200 according to Embodiment 2. In Embodiment 1, the resistor Rs1 and the resistor Rs2 have the same resistance value, and the resistor Rb1 and the resistor Rb2 have the same resistance value. However, it is not limited to this, and the resistance value of the resistor Rs1 may be set to be larger than the resistance value of the resistor Rs2, and the resistance value of the resistor Rb1 may be set to be smaller than the resistance value of the resistor Rb2. That is, in this embodiment, the resistance values of the resistors Rs1 and Rs2 of the stabilization circuits S1 and S2 are larger for the amplifier closer to the high-frequency input terminal T1. In addition, the resistance values of the resistors Rb1 and Rb2 of the output bias circuits B2 and B4 are smaller for the amplifier closer to the high-frequency input terminal T1. Other structures are the same as those of Embodiment 1. In addition, Figure 9 the resistor Rs2 having a resistance value different from that of the resistor Rs1 is denoted as the resistor Rs2′, and the resistor Rb2 having a resistance value different from that of the resistor Rb1 is denoted as the resistor Rb2′.

[0080] To explain the effects of Embodiment 2, the following three cases where the magnitude relationships of the resistance values of the resistor Rs1, the resistor Rs2, the resistor Rb1, and the resistor Rb2 are changed are studied. Other conditions are the same as those described in Embodiment 1.

[0081] Case (1): Resistance value of Rs1 = Resistance value of Rs2, Resistance value of Rb1 = Resistance value of Rb2

[0082] Case (2): Resistance value of Rs1 < Resistance value of Rs2, Resistance value of Rb1 > Resistance value of Rb2

[0083] Case (3): Resistance value of Rs1 > resistance value of Rs2, resistance value of Rb1 < resistance value of Rb2

[0084] Case (1) corresponds to Embodiment 1. Case (3) corresponds to this embodiment.

[0085] For the above three cases, an explanation will be given on how the stabilization circuits S1 and S2, the first band rejection filters BRFm1 and BRFm2, the circuit losses generated in the output bias circuits B2 and B4, the gain flatness of the used band, and the noise figure change.

[0086] Similar to the research conducted in Embodiment 1, the used band is 14 to 16 GHz, and the center of the rejection band of the first band rejection filters BRFm1 and BRFm2 is 13 GHz. In addition, the center frequency of the power rejected by the second band rejection filters BRFb1 and BRFb2 is less than 13 GHz, and the frequency does not drop to the GHz level where there is a circuit loss at 13 GHz.

[0087] Figure 10 It is a diagram showing the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 of the amplifier in the front stage of Embodiment 2. Figure 11 It is a diagram showing the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 of the amplifier in the rear stage of Embodiment 2. As Figure 10 , 11 shown, in this calculation example, in any of Cases (1) to (3), the resonance frequencies of the LC resonance circuits constituting the stabilization circuits S1 and S2 are set such that the circuit loss of the stabilization circuit S1 becomes zero at 14 GHz and the circuit loss of the stabilization circuit S2 becomes zero at 16 GHz.

[0088] Compared with Case (1), in Case (2), the overall circuit loss of the stabilization circuit S1 is larger at frequencies near but other than the frequency fs1. In addition, compared with Case (1), in Case (2), the circuit loss of the output bias circuit B2 is larger on the far side of the frequency fb in the used band. Thus, Figure 10 the absolute value of the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 shown, that is, the circuit loss, is larger in Case (2) compared with Case (1).

[0089] Similarly, compared with Case (1), in Case (2), the overall circuit loss of the stabilization circuit S2 is smaller at frequencies near but other than the frequency fs2. In addition, compared with Case (1), in Case (2), the circuit loss of the output bias circuit B4 is smaller on the far side of the frequency fb in the used band. Thus, Figure 11The absolute value of the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 shown, that is, the circuit loss, is smaller in case (2) than in case (1).

[0090] On the other hand, compared with case (1), in case (3), the overall circuit loss of the stabilization circuit S1 is smaller at frequencies near but other than the frequency fs1. In addition, compared with case (1), in case (3), the circuit loss of the output bias circuit B2 is smaller on the far side of the frequency fb in the used frequency band. Thus, Figure 10 The absolute value of the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 shown, that is, the circuit loss, becomes smaller in case (3) than in case (1).

[0091] Similarly, compared with case (1), in case (3), the overall circuit loss of the stabilization circuit S2 is larger at frequencies near but other than the frequency fs2. In addition, compared with case (1), in case (3), the circuit loss of the output bias circuit B2 is larger on the far side of the frequency fb in the used frequency band. Thus, Figure 11 The absolute value of the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 shown, that is, the circuit loss, is larger in case (3) than in case (1).

[0092] On the above premise, calculate the gain and noise figure of the high-frequency amplifier 200 assuming that the gain of each transistor is 10 dB regardless of frequency, the noise figure is 0.6 dB, and there is no circuit loss other than the stabilization circuit, the output bias circuit, and the band rejection filter.

[0093] Figure 12 It is a diagram showing the gain of the high-frequency amplifier 200 of Embodiment 2. By adding the attenuation characteristics of the stabilization circuit S1 and the output bias circuit B2, and the stabilization circuit S2 and the output bias circuit B4, it can be seen that the rejection band in case (3) is wider than that in case (1). For example, for the frequency range of the rejection band where the gain of the high-frequency amplifier 200 becomes 5 dB or less, case (3) is about 0.1 GHz wider than case (1). Thus, in the present embodiment corresponding to case (3), an effect of further widening the attenuation characteristics can be obtained.

[0094] Figure 13 It is a diagram showing the noise figure of the high-frequency amplifier 200 of Embodiment 2. For the worst value in the used frequency band of the noise figure, it is 0.73 dB in case (1), 0.77 dB in case (2), and 0.69 dB in case (3).

[0095] The noise figure of a two-stage amplifier is generally calculated by the following formula.

[0096] F = F1 + (F2 - 1) / G1 ··· (Equation 1)

[0097] Here, F is the noise figure of the second-stage amplifier, F1 and F2 are the noise figures of the first-stage amplifier and the second-stage amplifier respectively, and G1 is the gain of the first-stage amplifier. According to Equation 1, even if the total circuit loss of the multi-stage circuit is the same, the greater the circuit loss of the first-stage amplifier, the worse the noise figure of the first-stage amplifier, and thus the worse the noise figure of the multi-stage amplifier. In other words, as long as the circuit loss of the first-stage amplifier can be reduced, even if the total circuit loss of all stages is the same, the noise figure of the multi-stage amplifier can be improved.

[0098] The reason for obtaining a lower noise figure in case (3) than in case (2) is that the resistance value of resistor Rs1 is set larger than that of resistor Rs2, and the resistance value of resistor Rb1 is set smaller than that of resistor Rb2. Thereby, the circuit losses of the stabilization circuit S1 and the output bias circuit B2 can be suppressed, and the worst value within the operating frequency band of the noise figure of the first-stage amplifier can be suppressed.

[0099] Under this technical concept, in the high-frequency amplifier 200 of the present embodiment, it is assumed that the resistance value of resistor Rs1 > the resistance value of resistor Rs2, and the resistance value of resistor Rb1 < the resistance value of resistor Rb2. Thereby, a flat gain characteristic in the operating frequency band can be maintained, a lower noise figure can be obtained, and the attenuation amount and attenuation bandwidth in the rejection frequency band can be further increased.

[0100] In addition, if either the resistance value of resistor Rs1 > the resistance value of resistor Rs2 or the resistance value of resistor Rb1 < the resistance value of resistor Rb2 holds, the effect of improving the noise figure can be obtained. Therefore, either the resistance values of resistors Rs1 and Rs2 are made larger for the amplifier closer to the high-frequency input terminal T1, or the resistance values of resistors Rb1 and Rb2 are made smaller for the amplifier closer to the high-frequency input terminal T1 can be applied to the high-frequency amplifier 200.

[0101] Embodiment 3.

[0102] In this embodiment, it is different from Embodiment 1 in that the rejection band is higher than the used band. Other structures are the same as those in Embodiment 1. The first band rejection filters BRFm1 and BRFm2 in this embodiment reject the power of frequencies higher than the used band of the amplifier. That is, the first resonance frequency fr at which the maximum loss is given to the first band rejection filters BRFm1 and BRFm2 is higher than the used frequency of the amplifier. In addition, the second band rejection filters BRFb1 and BRFb2 reject the power of frequencies higher than the frequencies rejected by the first band rejection filters BRFm1 and BRFm2. That is, the second resonance frequency fb at which the maximum loss is given to the second band rejection filters BRFb1 and BRFb2 is higher than the first resonance frequency fr of the first band rejection filters BRFm1 and BRFm2.

[0103] In this embodiment, the resonance frequency fs1 of the LC resonance circuit constituting the stabilization circuit S1 is set higher than the center value fc of the used band of the amplifier. In addition, the resonance frequency fs2 of the LC resonance circuit constituting the stabilization circuit S2 is set lower than the center value fc of the used band of the amplifier. In this way, the resonance frequencies fs1 and fs2 of the band-pass filters BPF1 and BPF2 are higher the closer they are to the high-frequency input terminal T1. Based on the above, the following equation holds.

[0104] fs2 < fc < fs1 ≤ fr < fb

[0105] In this embodiment, by providing the second band rejection filters BRFb1 and BRFb2, based on the same principle as in the case of Embodiment 1, the same effects as in Embodiment 1 can also be obtained.

[0106] In addition, in this embodiment, the second resonance frequency fb is higher than the first resonance frequency fr. However, it is not limited thereto, and the second resonance frequency fb may also be lower than the first resonance frequency fr. That is, the first resonance frequency fr and the second resonance frequency fb may be different from each other and higher than the used frequency fc of the amplifier.

[0107] In addition, this embodiment and Embodiment 2 may be combined. That is, one or both of the conditions that the resistance value of the resistor Rs1 > the resistance value of the resistor Rs2 and the resistance value of the resistor Rb1 < the resistance value of the resistor Rb2 may be added. Thereby, based on the same principle as in Embodiment 2, a flat gain characteristic in the used band can be maintained, a lower noise figure can be obtained, and the attenuation amount and attenuation bandwidth in the rejection band can be further increased.

[0108] Embodiment 4.

[0109] Figure 14This is a diagram showing the structure of the high-frequency amplifier 300 according to Embodiment 3. Although in Embodiment 1, the resonance frequencies of the second-band rejection filters BRFb1 and BRFb2 are the same, they may also be different. In this embodiment, the second-band rejection filter BRFb2 includes an inductor Lb2' and a capacitor Cb2', and thus the second-band rejection filter BRFb2 has a resonance frequency fb'. The second resonance frequency fb' of the second-band rejection filter BRFb2 is set to a value lower than the first resonance frequency fr of the first-band rejection filters BRFm1 and BRFm2 and higher than the second resonance frequency fb of the second-band rejection filter BRFb1. That is, the closer the second resonance frequencies fb and fb' of the amplifier are to the high-frequency input terminal T1, the lower they are. Other structures are the same as those in Embodiment 1.

[0110] The resonance frequencies fs1 and fs2 of the band-pass filters BPF1 and BPF2, the center value fc of the used frequency band, the resonance frequency fr of the first-band rejection filters BRFm1 and BRFm2, and the resonance frequencies fb and fb' of the second-band rejection filters BRFb1 and BRFb2 satisfy the following relationship.

[0111] fb < fb' < fr ≤ fs1 < fc < fs2

[0112] Even if the total circuit loss of the multi-stage circuit is the same, by adopting the above structure, the circuit loss in the used frequency band of the first-stage amplifier can be reduced. Therefore, similar to the principle shown in Embodiment 2, even if the total circuit loss of all stages is the same, the noise figure of the multi-stage amplifier can be improved. Therefore, in the high-frequency amplifiers of Embodiments 1 and 2, by applying the above conditions, a lower noise figure can be obtained from the low-frequency end to the high-frequency end of the used frequency band.

[0113] In addition, this embodiment and Embodiment 3 can be combined. In this case, the second resonance frequency fb is set to be higher the closer it is to the high-frequency input terminal T1. That is, fs2 < fc < fs1 ≤ fr < fb' < fb. As a result, a lower noise figure than that in Embodiment 3 can be obtained.

[0114] Embodiment 5.

[0115] Figure 15 This is a diagram showing the structure of the high-frequency amplifier 400 according to Embodiment 5. In Embodiment 1, the input bias power supply terminal T2 and the input bias power supply terminal T4 are provided separately. In addition, the output bias power supply terminal T3 and the output bias power supply terminal T5 are provided separately. However, it is not limited thereto, and bias can also be supplied to a plurality of amplifiers from a common input bias common power supply terminal Tg. In addition, bias can also be supplied to a plurality of amplifiers from a common output bias common power supply terminal Td.

[0116] The present embodiment and Embodiment 2 can also be combined. That is, it can also be set that the resistance value of resistor Rs1 > the resistance value of resistor Rs2 and the resistance value of resistor Rb1 < the resistance value of resistor Rb2. For example, consider the case where the characteristics such as the noise figure or gain become optimal at the same voltage in transistors Tr1 and Tr2 by making the transistors Tr1 and Tr2 have the same gate width or the like. At this time, the respective resistance values can be set such that the sum of the resistance value of resistor Rs1 and the resistance value of resistor Rb1 is equal to the sum of the resistance value of resistor Rs2 and the resistance value of resistor Rb2.

[0117] Accordingly, a voltage is applied from a power supply such as a module incorporated in the high-frequency amplifier 400 to the output bias common power supply terminal Td, and the voltage drop values generated by resistor Rs1 and resistor Rb1, and resistor Rs2 and resistor Rb2 are the same values. Therefore, both transistors Tr1 and Tr2 can operate at a voltage at which characteristics such as the noise figure or gain are optimal.

[0118] In this way, in the present embodiment, by making the input bias power supply terminal and the output bias power supply terminal common in each stage of the amplifier, simplification of the terminal structure and miniaturization of the circuit can be achieved. And by setting the resistance values as described above, the same effects as those shown in Embodiments 1 to 4 can be obtained.

[0119] In addition, as described in Embodiment 2, the circuit loss of each amplifier has a characteristic opposite to the resistance values of the two resistors included in the amplifier. These two resistors are connected in series between the output bias common power supply terminal Td and the output terminal of the transistor. Due to such a relationship and configuration, the above effects are produced. Specifically, in the amplifier arranged at the position closest to the high-frequency input terminal T1, by increasing the resistance value of resistor Rs1 and on the other hand decreasing the resistance value of resistor Rb1, the circuit loss can be reduced. Also, in the amplifier arranged at the position farthest from the high-frequency input terminal T1, the resistance value of resistor Rs2 can be decreased and on the other hand the resistance value of resistor Rb2 can be increased. Thereby, the sum of the resistance values can be made constant in all the amplifiers, and both the transistor Tr1 and the transistor Tr2 can operate at a voltage at which characteristics such as the noise figure or gain are optimal.

[0120] In other words, the above effects cannot be obtained only by arranging a stabilization circuit in which a band-pass filter is connected in parallel with a resistor in each stage. Similarly, the above effects cannot be obtained only by arranging an output bias circuit in which a band-rejection filter is connected in series with a resistor in each stage.

[0121] Embodiment 6.

[0122] Figure 16This is a diagram showing the structure of the high-frequency amplifier 500 according to Embodiment 6. The high-frequency amplifier 500 of this embodiment includes a three-stage amplifier. Although the two-stage amplifier has been mainly described in Embodiments 1 to 5, Embodiments 1 to 5 can also be applied to high-frequency multi-stage low-noise amplifiers in which three or more stages of amplifiers are connected in series.

[0123] In Figure 16 , the input matching circuit M1 to the output matching circuit M2 are the first-stage amplifier, the input matching circuit M3 to the output matching circuit M4 are the second-stage amplifier, and the input matching circuit M5 to the output matching circuit M6 are the third-stage amplifier. Inter-stage capacitors C1 and C2 are connected between the stages. The structures of the first-stage and second-stage amplifiers are the same as those of Embodiment 1.

[0124] The third-stage amplifier has the same structure as the first-stage amplifier. The third-stage amplifier includes an input matching circuit M5, an input bias circuit B5, an input bias power supply terminal T7, a transistor Tr3, and a source inductor SI3. The third-stage amplifier also includes a stabilization circuit S3, a first band rejection filter BRFm3, an output bias circuit B6, an output bias power supply terminal T8, and an output matching circuit M6.

[0125] In the stabilization circuit S3, a series resonance circuit of an inductor Ls3 and a capacitor Cs3 that resonates at a frequency fs3 is connected in parallel with a resistor Rs3. In the first band rejection filter BRFm3, a series resonance circuit of an inductor Lr3 and a capacitor Cr3 is shunt-connected. The inductor Lr3 has, for example, the same inductance as the inductor Lr1. The capacitor Cr3 has, for example, the same capacitance value as the capacitor Cr1. Therefore, the resonance frequency of the first band rejection filter BRFm3 is equal to the resonance frequency fr of the first band rejection filter BRFm1.

[0126] In the output bias circuit B6, a resistor Rb3 and an inductor Lb3 are connected in series with respect to the bias path to the transistor Tr3. In addition, a capacitor Cb3 is shunt-connected with respect to the bias path. The resistor Rb3 has, for example, the same resistance value as the resistor Rb1. The inductor Lb3 has, for example, the same inductance as the inductor Lb1. The capacitor Cb3 has, for example, the same capacitance value as the capacitor Cb1. Therefore, the resonance frequency of the second band rejection filter BRFb3 formed by the inductor Lb3 and the capacitor Cb3 is equal to the resonance frequency fb of the second band rejection filter BRFb1.

[0127] In the case where a band rejection filter having a resonance frequency lower than the use frequency band of the amplifier is arranged, the resonance frequency of the series resonance circuit constituting the stabilization circuit is set to be lower for the amplification stage closer to the high-frequency input terminal T1. That is, the resonance frequency of the band-pass filter is lower for the amplification stage closer to the high-frequency input terminal T1. It is expressed by the following formula.

[0128] fb < fr ≤ fs1 < fs2 < fs3

[0129] On the other hand, in the case where a band rejection filter having a resonance frequency higher than the use frequency band of the amplifier is provided, the resonance frequency of the series resonance circuit constituting the stabilization circuit is set to be higher for the amplification stage closer to the high-frequency input terminal T1. That is, the resonance frequency of the band-pass filter is higher closer to the high-frequency input terminal T1. It is expressed by the following formula.

[0130] fs3 < fs2 < fs1 ≤ fr < fb

[0131] According to the present embodiment, as in Embodiments 1 to 5, on the basis of maintaining the noise figure and gain deviation from the low-frequency end to the high-frequency end of the use frequency band, it is possible to increase the attenuation amount and attenuation bandwidth of the rejection band.

[0132] Next, a case where the technical idea of Embodiment 2 is adopted in the present embodiment will be described. In this case, the resistance value of the resistor constituting the stabilization circuit is larger closer to the high-frequency input terminal T1, and the resistance value of the resistor constituting the output bias circuit is smaller closer to the high-frequency input terminal T1. That is, it is set that the resistance value of resistor Rs1 > the resistance value of resistor Rs2 > the resistance value of resistor Rs3, and the resistance value of resistor Rb1 < the resistance value of resistor Rb2 < the resistance value of resistor Rb3.

[0133] The noise figure of the n-stage amplifier is calculated by Equation 2 expanded from Equation 1.

[0134] F = F1 + (F2 - 1) / G1 + (F3 - 1) / G1G2 + … + (Fn - 1) / G1G2…Gn - 1 ··· (Equation 2)

[0135] Here, n is a natural number, F is the noise figure of the multi-stage amplifier, F1, F2, F3, …, Fn are the noise figures of the 1st to nth stage amplifiers, and G1, G2, …, Gn are the gains of the 1st to nth stage amplifiers.

[0136] According to Equation 2, even if the total circuit loss of the multi-stage circuit is the same, the greater the circuit loss of the amplifier closer to the high-frequency input terminal T1, the worse the noise figure of this amplifier, and thus the noise figure of the multi-stage amplifier deteriorates. In other words, as long as the circuit loss of the amplifier closer to the high-frequency input terminal can be reduced, even if the total circuit loss of all stages is the same, it is possible to improve the noise figure of the multi-stage amplifier.

[0137] As described above, it can be configured that in a high-frequency amplifier in which three or more stages of amplifiers are connected in series, the resistance value of the resistor of the stabilization circuit is larger closer to the high-frequency input terminal T1, and the resistance value of the resistor of the output bias circuit is smaller closer to the high-frequency input terminal T1.

[0138] In addition, in Embodiments 1 to 6, the output bias circuit having the stabilization circuit, the first band rejection filter, and the second band rejection filter may be arranged in all the amplifiers constituting the high-frequency amplifier, or may be arranged only in specific amplifiers. The features of the amplifiers described in each embodiment may be applied to at least two of the plurality of amplifiers included in the multi-stage circuit. That is, in the case where the multi-stage circuit includes three or more amplifiers, the features of any one of the amplifiers in Embodiments 1 to 6 may be applied to any two or more of them. For example, the technology of the present embodiment may also be applied to the first to third stages of a four-stage amplifier, and any element of the stabilization circuit, the first band rejection filter, and the output bias circuit may be arranged in the fourth-stage amplifier.

[0139] The technical features described in each embodiment may also be appropriately combined and used.

[0140] Description of Reference Numerals

[0141] 100, 200, 300, 400, 500... High-frequency amplifier; B1... Input bias circuit; B2... Output bias circuit; B3... Input bias circuit; B4... Output bias circuit; B5... Input bias circuit; B6... Output bias circuit; BPF1, BPF2... Band-pass filter; BRFb1, BRFB2, BRFb3... Second band rejection filter; BRFm1, BRFm2, BRFm3... First band rejection filter; C, C1, C2... Inter-stage capacitor; Cb1, Cb2, Cb3, Cr1, Cr2, Cr3, Cs1, Cs2, Cs3... Capacitor; Lb1, Lb2, Lb3, Lr1, Lr2, Lr3, Ls1, Ls2, Ls3... Inductor; M1... Input matching circuit; M2... Output matching circuit; M3... Input matching circuit; M4... Output matching circuit; M5... Input matching circuit; M6... Output matching circuit, Rb1, Rb2, Rb3, Rs1, Rs2, Rs3... Resistor; S1, S2, S3... Stabilization circuit; SI1, SI2, SI3... Source inductor; T1... High-frequency input terminal; T2... Input bias power supply terminal; T3... Output bias power supply terminal; T4... Input bias power supply terminal; T5... Output bias power supply terminal; T6... High-frequency output terminal; T7... Input bias power supply terminal; T8... Output bias power supply terminal; Td... Output bias common power supply terminal; Tg... Input bias common power supply terminal; Tr1, Tr2, Tr3... Transistor.

Claims

1. A high-frequency amplifier, characterized in that, Comprising: High-frequency input terminals; High-frequency output terminals; A plurality of amplifiers, which are arranged between the high-frequency input terminals and the high-frequency output terminals, each having a transistor and being connected in series; A stabilization circuit, which is arranged in at least two of the plurality of amplifiers; A first band rejection filter, which is arranged in the at least two amplifiers; And An output bias circuit, which is arranged in the at least two amplifiers and supplies a bias to the output terminals of the corresponding transistors, Each of the stabilization circuits has: a band-pass filter and a first resistor connected in parallel with the band-pass filter, and is arranged between the output terminal of the corresponding transistor and the high-frequency output terminal, Each of the first band rejection filters has a first resonance frequency and is arranged between the output terminal of the corresponding transistor and the high-frequency output terminal, Each of the output bias circuits has a second band rejection filter, and the second band rejection filter has a second resonance frequency, In the at least two amplifiers, the first resonance frequency and the second resonance frequency are different from each other and lower than the operating frequency of the amplifier, or the first resonance frequency and the second resonance frequency are different from each other and higher than the operating frequency of the amplifier.

2. The high-frequency amplifier according to claim 1, wherein In the at least two amplifiers, the first resonance frequency is lower than the operating frequency.

3. The high-frequency amplifier according to claim 2, wherein In the at least two amplifiers, the resonance frequency of the band-pass filter is lower the closer it is to the high-frequency input terminal.

4. The high-frequency amplifier according to claim 2 or 3, wherein In the at least two amplifiers, the second resonance frequency is lower than the first resonance frequency.

5. The high-frequency amplifier according to any one of claims 2 to 4, wherein The second resonance frequency of the at least two amplifiers is lower the closer it is to the high-frequency input terminal.

6. The high-frequency amplifier according to claim 1, wherein In the at least two amplifiers, the first resonance frequency is higher than the operating frequency.

7. The high-frequency amplifier according to claim 6, wherein In the at least two amplifiers, the resonance frequency of the band-pass filter is higher the closer it is to the high-frequency input terminal.

8. The high-frequency amplifier according to claim 6 or 7, wherein In the at least two amplifiers, the second resonance frequency is higher than the first resonance frequency.

9. The high-frequency amplifier according to any one of claims 6 to 8, wherein The second resonance frequency of the at least two amplifiers is higher the closer it is to the high-frequency input terminal.

10. The high-frequency amplifier according to any one of claims 1 to 9, wherein In the at least two amplifiers, for the amplifier closer to the high-frequency input terminal, the resistance value of the first resistor of the stabilization circuit is larger.

11. The high-frequency amplifier according to any one of claims 1 to 9, wherein Each of the output bias circuits has a second resistor connected in series with the second band rejection filter. Among the at least two amplifiers, the closer an amplifier is to the high-frequency input terminal, the smaller the resistance value of the second resistor of the output bias circuit.

12. The high-frequency amplifier according to any one of claims 1 to 9, wherein: Each of the output bias circuits has a second resistor connected in series with the second band rejection filter. Among the at least two amplifiers, the closer an amplifier is to the high-frequency input terminal, the larger the resistance value of the first resistor of the stabilization circuit, and the closer an amplifier is to the high-frequency input terminal, the smaller the resistance value of the second resistor of the output bias circuit.

13. The high-frequency amplifier according to claim 12, wherein: Among the at least two amplifiers, the sum of the resistance value of the first resistor and the resistance value of the second resistor is equal.

14. The high-frequency amplifier according to claim 13, wherein: Bias is supplied to the at least two amplifiers from a common output bias power supply terminal.

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