High-frequency amplifier

Abstract

A high-frequency amplifier as in the present disclosure comprises: a high-frequency input terminal; a high-frequency output terminal; a plurality of amplifiers that each have a transistor and are connected in series; and a stabilizer circuit, a first band elimination filter, and an output bias circuit that are each provided to at least two amplifiers of the plurality of amplifiers. Each of the stabilizer circuits has a band-pass filter, and a first resistor connected in parallel to the band-pass filter. Each of the first band elimination filters has a first resonance frequency. Each of the output bias circuits has a second band elimination filter that has a second resonance frequency. In the at least two amplifiers, the first resonance frequency and the second resonance frequency are different from one another and have a lower frequency than a use-frequency of the amplifiers, or the first resonance frequency and the second resonance frequency are different from one another and have a higher frequency than a use-frequency of the amplifiers.

Description

[Technical Field]

[0001] The present disclosure relates to high frequency amplifiers. [Background technology]

[0002] Patent Document 1 discloses a high-frequency multistage low-noise amplifier. This high-frequency multistage low-noise amplifier includes a high-frequency input terminal, a high-frequency output terminal, and a multistage circuit provided between the high-frequency input terminal and the high-frequency output terminal. The multistage circuit includes two or more amplifiers connected in series, each having an input matching circuit, a transistor, and an output matching circuit. At least two amplifiers in the multistage circuit are provided with a stabilization circuit in which a band-pass filter and a resistor are connected in parallel, and a band-elimination filter that eliminates frequencies lower than the operating frequency of the amplifier. The stabilization circuit and the band-elimination filter are provided between the output terminal of the transistor of the amplifier to which they belong and the output matching circuit, or within the output matching circuit. The resonant frequency of a band-pass filter is lower the closer it is to the high-frequency input terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 024189 Summary of the Invention [Problem to be solved by the invention]

[0004] In general, high-frequency low-noise amplifiers are required to have low noise in the amplified and output high-frequency power and to be stable across the entire frequency band. In particular, in satellite communications or terrestrial base station communications, improving the amplifier's distortion characteristics and eliminating unwanted signals are sometimes required to ensure communication quality. For these purposes, it may be necessary to suppress the gain of a frequency band different from the amplifier's operating band but adjacent to it, i.e., an exclusion band. The high-frequency amplifier disclosed in Patent Document 1 can reduce the pass loss across the entire operating band from the low to high end while suppressing the gain in the exclusion band. Therefore, a low noise figure can be achieved across a wide band, and gain flatness across the operating band can be improved.

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

[0006] Generally, when a band-elimination filter is placed, circuit loss occurs at the resonant frequency of the band-elimination filter, and the gain of the amplifier is attenuated at the resonant frequency. However, it is practically impossible to attenuate the gain at only a single frequency. As a result, circuit loss also occurs in the operating band, affecting the gain or noise figure of the amplifier in the operating band. This increases circuit loss, which may worsen the noise figure at the band edge of the operating band. It may also worsen the flatness of the gain in the operating band.

[0007] For example, if a band-rejection filter with a center frequency of 13 GHz is installed in an amplifier operating in the 14-16 GHz band, the gain at 13 GHz can be reduced. However, the filter's attenuation characteristic tails off over frequency. This results in circuit loss even in the operating band. In the above example, where the rejection band is lower than the operating band, there is a risk of a reduction in gain and a deterioration in noise figure at 14 GHz, the lower end of the operating band.

[0008] To further increase the attenuation or attenuation bandwidth in the rejection band, it is possible to add another band rejection filter with a center frequency of 13 GHz. Alternatively, instead of the band rejection filter with a center frequency of 13 GHz, it is possible to provide a band rejection filter with a center frequency of 12.8 GHz and another band rejection filter with a center frequency of 13.2 GHz. In this case, the gain at the lower end of the usable band, 14 GHz, may be further reduced, potentially worsening the noise figure.

[0009] An object of the present disclosure is to provide a high-frequency amplifier that can improve the attenuation or attenuation bandwidth in the exclusion band while suppressing a decrease in gain or a deterioration in noise figure in the band of use. [Means for solving the problem]

[0010] a first band-elimination filter provided in the at least two amplifiers; and an output bias circuit provided in the at least two amplifiers for supplying a bias to an output terminal of a corresponding transistor, wherein each of the stabilization circuits has a band-pass filter and a first resistor connected in parallel with the band-pass filter and is provided between the output terminal of the corresponding transistor and the high-frequency output terminal, each of the first band-elimination filters having a first resonant frequency and being provided between the output terminal of the corresponding transistor and the high-frequency output terminal, and each of the output bias circuits has a second band-elimination filter having a second resonant frequency, and in the at least two amplifiers, the first resonant frequency and the second resonant frequency are different from each other and are lower than an operating frequency of the amplifier, or the first resonant frequency and the second resonant frequency are different from each other and are higher than an operating frequency of the amplifier. [Effects of the Invention]

[0011] In the high-frequency amplifier according to the present disclosure, the first band-elimination filter and the second band-elimination filter can improve the attenuation or attenuation bandwidth in the exclusion band while suppressing a decrease in gain or a deterioration in noise figure in the band of use. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a configuration of a high-frequency amplifier according to a first embodiment. [Figure 2] FIG. 10 is a diagram showing changes in the gain of a stabilization circuit with respect to frequency. [Figure 3] FIG. 10 is a diagram showing a change in gain of an output bias circuit with respect to frequency. [Figure 4] 4 is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit included in the front-stage amplifier according to the first embodiment. FIG. [Figure 5] 4 is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit included in the amplifier at the subsequent stage according to the first embodiment. FIG. [Figure 6] FIG. 4 is a diagram illustrating a gain of a first band-elimination filter according to the first embodiment. [Figure 7] FIG. 3 is a diagram illustrating the gain of the high-frequency amplifier according to the first embodiment. [Figure 8] 4 is a diagram showing the noise figure of the high-frequency amplifier according to the first embodiment. FIG. [Figure 9] FIG. 10 is a diagram illustrating the configuration of a high-frequency amplifier according to a second embodiment. [Figure 10] FIG. 10 is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit included in the amplifier at the previous stage according to the second embodiment. [Figure 11] FIG. 10 is a diagram showing the sum of the gains of the stabilization circuit and the output bias circuit included in the amplifier at the subsequent stage according to the second embodiment. [Figure 12] FIG. 10 is a diagram illustrating the gain of the high-frequency amplifier according to the second embodiment. [Figure 13] FIG. 10 is a diagram illustrating the noise figure of the high-frequency amplifier according to the second embodiment. [Figure 14]FIG. 10 is a diagram illustrating the configuration of a high-frequency amplifier according to a fourth embodiment. [Figure 15] FIG. 10 is a diagram illustrating the configuration of a high-frequency amplifier according to a fifth embodiment. [Figure 16] FIG. 10 is a diagram illustrating the configuration of a high-frequency amplifier according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] High-frequency amplifiers according to the embodiments will be described with reference to the drawings. The same or corresponding components are designated by the same reference numerals, and repeated description may be omitted.

[0014] Embodiment 1 1 is a diagram illustrating the configuration of a high-frequency amplifier 100 according to a first embodiment. The high-frequency amplifier 100 is also called a high-frequency multistage low-noise amplifier. The high-frequency amplifier 100 is a high-frequency power amplifier that amplifies high-frequency power such as microwaves or millimeter waves.

[0015] High-frequency amplifier 100 includes a high-frequency input terminal T1, a high-frequency output terminal T6, and a multi-stage circuit disposed between the high-frequency input terminal T1 and the high-frequency output terminal T6. The high-frequency input terminal T1 is a terminal through which high-frequency power is input to high-frequency amplifier 100. The high-frequency output terminal T6 is an output terminal of high-frequency amplifier 100. The multi-stage circuit includes multiple amplifiers connected in series. Each amplifier includes input matching circuits M1 and M3, transistors Tr1 and Tr2, and output matching circuits M2 and M4. While two amplifiers are shown in FIG. 1, the multi-stage circuit may include two or more amplifiers connected in series; the number of amplifiers is not limited.

[0016] In the example of Figure 1, the first-stage amplifier includes 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 further includes a stabilization circuit S1, a first band-elimination 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 includes 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 further includes a stabilization circuit S2, a first band-elimination filter BRFm2, an output bias circuit B4, an output bias power supply terminal T5, and an output matching circuit M4.

[0017] In this way, the components from the input matching circuit M1 to the output matching circuit M2 constitute the first stage amplifier when viewed from the radio frequency input terminal T1 side. The input matching circuit M1 is the input-side matching circuit of transistor Tr1. The input bias circuit B1 is a circuit that applies a bias voltage to the gate terminal of 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 amplifying element that amplifies radio frequency power. One end of the source inductor SI1 is connected to the source terminal of transistor Tr1, and the other end of the source inductor SI1 is grounded.

[0018] 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 resonant circuit of an inductor Ls1 and a capacitor Cs1 that resonates at a frequency fs1. The stabilization circuit S1 may be provided between the output terminal of the transistor Tr1 and the output matching circuit M2 of the same amplifier, or within the output matching circuit M2. In other words, the stabilization circuit S1 may be provided between the output terminal of the corresponding transistor Tr1 and the high-frequency output terminal T6 in the first-stage amplifier.

[0019] The first band-elimination filter BRFm1 is provided between the transistor Tr1 and the output matching circuit M2. The first band-elimination filter BRFm1 is configured as a series resonant circuit of an inductor Lr1 and a capacitor Cr1 that resonates at a frequency fr. The series resonant circuit is shunt-connected. Hereinafter, the resonant frequency fr of the first band-elimination filter BRFm1 may be referred to as the "first resonant frequency." The first band-elimination filter BRFm1 may be provided between the output terminal of the transistor Tr1 and the output matching circuit M2 that belong to the same amplifier, or within the output matching circuit M2. In other words, the first band-elimination filter BRFm1 may be provided between the output terminal of the corresponding transistor Tr1 and the high-frequency output terminal T6 in the first-stage amplifier.

[0020] Stabilization circuit S1 and first band exclusion The filter BRFm1 is connected to the stabilization circuit S1, the first band exclusion The stabilization circuit S1 and the first bandpass filter BRFm1 are connected in series to the output terminal of the transistor Tr1. exclusion The order of the filter BRFm1 may be reversed.

[0021] The output bias circuit B2 supplies a bias to the output terminal of the transistor Tr1. The output bias circuit B2 is located 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-elimination filter BRFb1 and a resistor Rb1 connected in series with the second band-elimination filter BRFb1. In the output bias circuit B2, the resistor Rb1 and an inductor Lb1 are connected in series with the bias path to the transistor Tr1. The capacitor Cb1 is shunt-connected to the bias path. The inductor Lb1 functions as a power supply path that applies the bias voltage. The inductor Lb1 and the capacitor Cb1 together form a second band-elimination filter BRFb1 that resonates at a frequency fb. Hereinafter, the resonant frequency fb of the second band-elimination filter BRFb1 may be referred to as the second resonant frequency.

[0022] The output bias power supply terminal T3 is a power supply terminal that supplies power to the output bias circuit B2 and supplies 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 interstage capacitor C is a DC blocking capacitor that blocks DC current from the output matching circuit M2 and the input matching circuit M3.

[0023] The components from the input matching circuit M3 to the output matching circuit M4 constitute the second-stage amplifier when viewed from the radio-frequency input terminal T1 side. The configuration of the second-stage amplifier is the same as that of the first-stage amplifier. The stabilization circuit S2 has 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 resonant circuit of an inductor Ls2 and a capacitor Cs2 that resonates at a frequency fs2.

[0024] The first band-elimination filter BRFm2 is composed of a series resonant circuit of inductor Lr2 and capacitor Cr2 that resonates at frequency fr. This series resonant circuit is shunt-connected. Inductor Lr2 has the same inductance as inductor Lr1, for example. Capacitor Cr2 has the same capacitance as capacitor Cr1, for example. Therefore, the resonant frequency of the first band-elimination filter BRFm2 is equal to the resonant frequency fr of the first band-elimination filter BRFm1.

[0025] The output bias circuit B4 supplies a bias to the output terminal of the transistor Tr2. The output bias circuit B4 includes a second band-elimination filter BRFb2 and a resistor Rb2 connected in series with the second band-elimination filter BRFb2. In the output bias circuit B4, the resistor Rb2 and an inductor Lb2 are connected in series with the bias path to the transistor Tr2. The capacitor Cb2 is shunt-connected to the bias path. The inductor Lb2 and the capacitor Cb2 form a second band-elimination filter BRFb2 that resonates at a frequency fb. The resistor Rb2 has, for example, the same resistance 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 as the capacitor Cb1. Therefore, the resonant frequency of the second band-elimination filter BRFb2 is equal to the resonant frequency fb of the second band-elimination filter BRFb1.

[0026] The frequency used as an amplifier, that is, the center value of the band used as an amplifier, is denoted by fc. The relationship between the resonance frequencies fs1 and fs2 of the bandpass filters BPF1 and BPF2, the first resonance frequency fr, and the second resonance frequency fb is as follows: fb <fr≦fs1<fc<fs2 The first resonance frequency fr is lower than the operating frequency fc. The resonance frequencies fs1 and fs2 of the band-pass filters BPF1 and BPF2 are lower the closer they are to the high-frequency input terminal T1.

[0027] In low-noise amplifiers, a source inductor is often used to ensure stability within the operating frequency band. However, the addition of a source inductor can impair stability at the higher frequencies of the operating frequency band. For this reason, it is necessary to insert a stabilization circuit with pass loss not only at the lower frequencies of the operating frequency band but also at the higher frequencies. It is also necessary to provide stabilization for each transistor stage. For this reason, it is preferable not to connect the stabilization circuit S1 and the stabilization circuit S2 in series. Therefore, it is recommended that the stabilization circuit S1 be located between the output terminal of transistor Tr1 and the output matching circuit M2, or inside the output matching circuit M2. It is also recommended that the stabilization circuit S2 be located between the output terminal of transistor Tr2 and the output matching circuit M4, or inside the output matching circuit M4.

[0028] In addition, it is preferable not to connect the first band-elimination filters BRFm1 and BRFm2 continuously in series. Therefore, it is preferable to provide the first band-elimination filter BRFm1 between the output terminal of the transistor Tr1 and the output matching circuit M2, or inside the output matching circuit M2. Furthermore, it is preferable to provide the first band-elimination filter BRFm2 between the output terminal of the transistor Tr2 and the output matching circuit M4, or inside the output matching circuit M4. This makes it possible to prevent excessive input of high-frequency power to all of the transistors Tr1 and Tr2, and to improve the distortion characteristics of each amplification stage.

[0029] Naturally, the output bias circuits B2 and B4 are not connected in series because they serve to provide bias voltages to the output terminals of the transistors Tr1 and Tr2, respectively.

[0030] In the above configuration, the LC series resonant circuit in the stabilization circuit S1 functions as a bandpass filter BPF1 that passes power at frequency fs1. Figure 2 is a diagram showing the change in gain of the stabilization circuit with respect to frequency. The vertical axis in Figure 2 represents the gain of the stabilization circuit. Circuit loss corresponds to the absolute value of the negative value in Figure 2. In other words, the further down the vertical axis, the smaller the gain and the larger the circuit loss.

[0031] When an LC series resonant circuit and resistor Rs1 are connected in parallel, the resonant circuit acts as a band-pass filter at the resonant frequency fs1, and ideally the pass loss is zero. On the other hand, when the frequency moves away from fs1, the input power is propagated via resistor Rs1. This increases the circuit loss, enabling stabilization.

[0032] The resistance value of resistor Rs1 is set arbitrarily based on the required insertion loss from near frequency fs1 to far away. The dashed line in Figure 2 indicates the gain when the resistance value of resistor Rs1 is increased from the reference value to a level that maintains the required circuit loss from near frequency fs1 to far away. At this time, the ratio of input power propagating via the LC series resonant circuit to input power propagating via resistor Rs1 increases. As a result, the circuit loss of the entire stabilization circuit S1 at frequencies near frequency fs1, excluding frequency fs1, is smaller than the reference value of the circuit loss.

[0033] The dotted line in Figure 2 shows the gain when the resistance value of resistor Rs1 is small enough to maintain the required circuit loss at a frequency far from the reference value at frequency fs1. At this time, the ratio of input power propagating via resistor Rs1 to input power propagating via the LC series resonant circuit increases. As a result, the circuit loss of the entire stabilization circuit S1 at frequencies near frequency fs1, excluding frequency fs1, becomes larger than the circuit loss at the reference value.

[0034] Similarly, the LC series resonant circuit in stabilization circuit S2 functions as a bandpass filter BPF2 that passes power at the resonant frequency fs2. At frequency fs2, the resonant circuit acts as a bandpass filter, and ideally the pass loss is zero. On the other hand, when the frequency moves away from fs2, the input power propagates via resistor Rs2. This increases the circuit loss, enabling stabilization.

[0035] Like resistor Rs1, the resistance value of resistor Rs2 is set arbitrarily based on the required insertion loss over the frequency range from near to far frequency fs2. For example, the resistance value of resistor Rs2 is the same as that of resistor Rs1. As with the stabilization circuit S1, the overall circuit loss of the stabilization circuit S2 varies depending on the value of resistor Rs2, as shown in Figure 2.

[0036] The first band-elimination filters BRFm1 and BRFm2 each eliminate power of frequency fr that is input from the radio frequency input terminal T1 and output to the radio frequency output terminal T6. The circuit loss of the first band-elimination filters BRFm1 and BRFm2 is maximized at frequency fr, and has frequency characteristics that tail off from the vicinity to a greater distance.

[0037] Both second band-elimination filters BRFb1 and BRFb2 eliminate power of frequency fb that is input from radio frequency input terminal T1 and output to radio frequency output terminal T6. The circuit loss of the second band-elimination filters BRFb1 and BRFb2 is maximized at frequency fb, and has frequency characteristics that tail off from the vicinity of frequency fb to a greater extent.

[0038] The output bias circuit B2 provides a bias voltage to the output terminal of the transistor Tr1 and functions as a band-elimination filter that rejects power at frequency fb. The resistance value of the resistor Rb1 that constitutes the output bias circuit B2 is set arbitrarily based on the required insertion loss over a range from near to far frequency fb.

[0039] Figure 3 shows the change in gain of the output bias circuit B2 with respect to frequency. The vertical axis in Figure 3 represents the gain of the output bias circuit B2, and the circuit loss corresponds to the absolute value of the negative value in Figure 3. As in Figure 2, the gain decreases, i.e., the circuit loss increases, as you move downward on the vertical axis.

[0040] The dashed line in Figure 3 shows the gain when the resistance value of resistor Rb1 is increased from the reference value to a level that allows for an acceptable increase in circuit loss in the operating band. In this case, the frequency characteristics of the second band-elimination filter BRFb1 become gentler. Therefore, the circuit loss of the output bias circuit B2 at frequency fb and frequencies near frequency fb is smaller than the reference value. Furthermore, the circuit loss of the output bias circuit B2 at frequencies far from frequency fb is larger than the reference value.

[0041] The dotted line in Figure 3 shows the gain when the resistance value of resistor Rb1 is reduced from the reference value to a level that allows for an acceptable reduction in circuit loss in the rejection band. At this point, the frequency characteristics of the second band rejection filter BRFb1 become steeper. Therefore, the circuit loss of the output bias circuit B2 at frequency fb and frequencies near frequency fb becomes greater than the reference value. Furthermore, the circuit loss of the output bias circuit B2 at frequencies far from frequency fb becomes smaller than the reference value.

[0042] Here, the frequency fb and the resistance value of resistor Rb1 are set so that when the resistance value of resistor Rb1 increases from its reference value, the circuit loss of output bias circuit B2 in the band used as an amplifier becomes larger than the original circuit loss. Also, the frequency fb and the resistance value of resistor Rb1 are set so that when the resistance value of resistor Rb1 decreases from its reference value, the circuit loss of output bias circuit B2 in the band used as an amplifier becomes smaller than the original circuit loss.

[0043] Similarly, output bias circuit B4 provides a bias voltage to the output terminal of transistor Tr2 and functions as a band-elimination filter that rejects power at frequency fb. The resistance value of resistor Rb2, which constitutes output bias circuit B4, is set arbitrarily based on the required insertion loss over a range from near frequency fb to far. When the resistance value of resistor Rb2 increases or decreases from its reference value, the circuit loss of output bias circuit B4 changes in the same way as the circuit loss of output bias circuit B2.

[0044] The resistance values of resistors Rs1, Rs2, Rb1, and Rb2 also serve to arbitrarily set the bias voltages applied to the output terminals of transistors Tr1 and Tr2. In general, a voltage at which the performance of a transistor is maximally exerted is applied to the transistor under voltage conditions that ensure the reliability of the required elements. In a low-noise amplifier, a voltage at which characteristics such as the noise figure and gain are optimal needs to be applied to the output terminal of the transistor.

[0045] On the other hand, voltages are applied to output bias power supply terminals T3 and T5 from a power supply of a module or the like in which the high-frequency amplifier 100 is incorporated. Each resistance value is set so that a desired voltage is applied to the output terminals of transistors Tr1 and Tr2 by dropping the voltage by a required amount by resistors Rs1, Rs2, Rb1, and Rb2.

[0046] Next, the effects on the gain flatness and noise figure in the used band by the second band rejection filters BRFb1 and BRFb2, and the effects on the gain attenuation characteristics in the rejection band will be described. Here, a case where the rejection band is lower than the used band, that is, a case where the first resonance frequency fr and the second resonance frequency fb are lower than the used frequency as an amplifier will be described. Here, when the condition fr < fs1 < fc < fs2 is satisfied, the following two cases will be considered. Case (1): When the output bias circuit does not include the second band rejection filter Case (2): When the output bias circuit includes the second band rejection filter Case (2) corresponds to the present embodiment.

[0047] For these cases, we will explain how the circuit losses occurring in the stabilization circuits S1 and S2, the first band-elimination filters BRFm1 and BRFm2, and the output bias circuits B2 and B4 change, as well as how the gain flatness and noise figure in the operating band change. Here, the operating band is assumed to be 14 to 16 GHz, and the center of the exclusion band of the first band-elimination filters BRFm1 and BRFm2 is 13 GHz. Furthermore, we will assume that the center frequency of the power rejected by the second band-elimination filters BRFb1 and BRFb2 is on the order of GHz, lower than 13 GHz but not so low that circuit losses will occur at 13 GHz.

[0048] Fig. 4 is a diagram showing the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 included in the front-stage amplifier according to embodiment 1. Fig. 5 is a diagram showing the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 included in the rear-stage amplifier according to embodiment 1. Fig. 6 is a diagram showing the gains of the first band-elimination filters BRFm1 and BRFm2 according to embodiment 1.

[0049] 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 correspond to the absolute values ​​of the negative values ​​in Figures 4 to 6. In the calculation examples of Figures 4 to 6, the resonant frequencies of the LC resonant circuits that make up the stabilization circuits are set so that the circuit loss of stabilization circuit S1 becomes zero at 14 GHz, and the circuit loss of stabilization circuit S2 becomes zero at 16 GHz.

[0050] In both cases (1) and (2), the attenuation of the first band-elimination filters BRFm1 and BRFm2 was assumed to have a maximum value of 10 dB at 13 GHz and a circuit loss of 0.6 dB at 14 GHz. The attenuation of the second band-elimination filters BRFb1 and BRFb2 was assumed to have a maximum value at frequencies well below 13 GHz, with a circuit loss of 1.5 dB at 13 GHz and nearly zero at 14 GHz and above. Based on these assumptions, the gain and noise figure of the high-frequency amplifier 100 were calculated, 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 that of the stabilization circuit, output bias circuit, and band-elimination filters.

[0051] 7 is a diagram showing the gain of the high-frequency amplifier 100 according to the first embodiment. In cases (1) and (2), the gain is almost the same from the low-frequency end of 14 GHz to the high-frequency end of 16 GHz in the amplifier's operating band. On the other hand, the attenuation near 13 GHz is greater in case (2). Also, the attenuation bandwidth is wider in case (2) than in case (1). For example, the bandwidth in which the gain in the exclusion band is 5 dB or less is 0.3 GHz in case (1), and 0.6 GHz in case (2) of this embodiment.

[0052] 8 is a diagram showing the noise figure of the high-frequency amplifier 100 according to the embodiment 1. In cases (1) and (2), the noise figures are almost the same from 14 GHz at the lower end to 16 GHz at the upper end of the operating band of the amplifier.

[0053] As described above, in this embodiment, by combining the first band-elimination filter and the second band-elimination filter, it is possible to improve the attenuation and attenuation bandwidth in the exclusion band while suppressing a decrease in gain or a deterioration in noise figure in the usable band. Generally, adding a band-elimination filter may also reduce the gain in the usable band. In contrast, in this embodiment, it is possible to maintain the same noise figure and gain deviation as before adding the band-elimination filter from the low-end to the high-end of the usable band.

[0054] Furthermore, in this embodiment, by adding the second band rejection filters BRFb1 and BRFb2 with a simple configuration, it is possible to improve the attenuation amount and the attenuation bandwidth in the rejection band, thereby suppressing an increase in the circuit size.

[0055] In this embodiment, the second resonance frequency fb is set to be lower than the first resonance frequency fr. That is, it is assumed that the frequencies rejected by the second band rejection filters BRFb1 and BRFb2 are lower than the frequencies rejected by the first band rejection filters BRFm1 and BRFm2. However, this is not limiting, and the second resonance frequency fb may 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 may be lower than the operating frequency fc of the amplifier. For example, the effects of this embodiment can be obtained even if the first resonance frequency fr is set to a value lower than the center frequency of the rejection band, 13 GHz, and the second resonance frequency fb is set to 13 GHz.

[0056] The above-described modifications can be applied as appropriate to the high-frequency amplifiers according to the following embodiments. Note that the high-frequency amplifiers according to the following embodiments have many points in common with the first embodiment, so the following description will focus on the differences from the first embodiment.

[0057] Embodiment 2 FIG. 9 is a diagram illustrating the configuration of a high-frequency amplifier 200 according to a second embodiment. In the first embodiment, resistors Rs1 and Rs2 have the same resistance value, and resistors Rb1 and Rb2 have the same resistance value. However, this is not limited to this. The resistance value of resistor Rs1 may be set to be greater than that of resistor Rs2, and the resistance value of resistor Rb1 may be set to be smaller than that of resistor Rb2. That is, in this embodiment, the resistance values ​​of resistors Rs1 and Rs2 in stabilization circuits S1 and S2 are greater for amplifiers closer to high-frequency input terminal T1. Furthermore, the resistance values ​​of resistors Rb1 and Rb2 in output bias circuits B2 and B4 are smaller for amplifiers closer to high-frequency input terminal T1. The other configurations are the same as those in the first embodiment. Note that in FIG. 9, resistor Rs2, which has a resistance value different from that of resistor Rs1, is referred to as resistor Rs2′, and resistor Rb2, which has a resistance value different from that of resistor Rb1, is referred to as resistor Rb2′.

[0058] To explain the effect of the second embodiment, the following three cases will be considered, in which the magnitude relationship between the resistance values ​​of resistors Rs1, Rs2, Rb1, and Rb2 is changed. The other conditions are the same as those described in the first embodiment. Case (1): Resistance value of Rs1 = Resistance value of Rs2, Resistance value of Rb1 = Resistance value of Rb2 Case (2): Resistance value of Rs1 < Resistance value of Rs2, Resistance value of Rb1 > Resistance value of Rb2 Case (3): Resistance value of Rs1 > Resistance value of Rs2, Resistance value of Rb1 < Resistance value of Rb2 Case (1) corresponds to Embodiment 1. Case (3) corresponds to this embodiment.

[0059] Regarding the above three cases, it will be explained how the circuit losses occurring in the stabilization circuits S1 and S2, the first band rejection filters BRFm1 and BRFm2, and the output bias circuits B2 and B4, as well as the gain flatness and noise figure of the used band, change.

[0060] Similar to the study 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. Also, the center frequency of the power rejected by the second band rejection filters BRFb1 and BRFb2 is smaller than 13 GHz and is on the order of GHz such that the frequency is not too low to have circuit losses at 13 GHz.

[0061] FIG. 10 is a diagram showing the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 included in the pre-stage amplifier according to Embodiment 2. FIG. 11 is a diagram showing the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 included in the post-stage amplifier according to Embodiment 2. As shown in FIGS. 10 and 11, 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 becomes zero at 14 GHz for the stabilization circuit S1 and at 16 GHz for the stabilization circuit S2.

[0062] In case (2), the circuit loss of the entire stabilization circuit S1 is larger at frequencies near frequency fs1, excluding frequency fs1, compared to case (1). Also, in case (2), the circuit loss of the output bias circuit B2 is larger on the far side of frequency fb within the operating band, compared to case (1). As a result, the absolute value of the sum of the gains of the stabilization circuit S1 and output bias circuit B2 shown in Figure 10, i.e., the circuit loss, is larger in case (2) compared to case (1).

[0063] Similarly, in case (2), the circuit loss of the entire stabilization circuit S2 at frequencies near frequency fs2, excluding frequency fs2, is smaller than in case (1). Also, in case (2), the circuit loss of the output bias circuit B4 is smaller on the far side of frequency fb in the operating band than in case (1). As a result, the absolute value of the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 shown in FIG. 11, i.e., the circuit loss, is smaller in case (2) than in case (1).

[0064] On the other hand, in case (3), the circuit loss of the entire stabilization circuit S1 at frequencies near frequency fs1, excluding frequency fs1, is smaller than in case (1). Also, in case (3), the circuit loss of the output bias circuit B2 is smaller on the far side of frequency fb in the operating band than in case (1). As a result, the absolute value of the sum of the gains of the stabilization circuit S1 and the output bias circuit B2 shown in Figure 10, i.e., the circuit loss, is smaller in case (3) than in case (1).

[0065] Similarly, in case (3), the circuit loss of the entire stabilization circuit S2 is greater at frequencies near frequency fs2, excluding frequency fs2, compared to case (1). Also, in case (3), the circuit loss of the output bias circuit B2 is greater at frequencies farther from frequency fb in the operating band than in case (1). As a result, the absolute value of the sum of the gains of the stabilization circuit S2 and the output bias circuit B4 shown in FIG. 11, i.e., the circuit loss, is greater in case (3) than in case (1).

[0066] Based on the above assumptions, the gain and noise figure of high-frequency amplifier 200 were calculated 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 in the stabilization circuit, output bias circuit, and band-elimination filter.

[0067] 12 is a diagram showing the gain of high-frequency amplifier 200 according to the second embodiment. It can be seen that the exclusion band is wider in case (3) than in case (1) because the attenuation characteristics of stabilization circuit S1 and output bias circuit B2, and stabilization circuit S2 and output bias circuit B4 are combined. For example, the frequency range of the exclusion band where the gain of high-frequency amplifier 200 is 5 dB or less is about 0.1 GHz wider in case (3) than in case (1). In this way, this embodiment, which corresponds to case (3), has the effect of further widening the attenuation band.

[0068] 13 is a diagram showing the noise figure of high-frequency amplifier 200 according to embodiment 2. The worst value of the noise figure in the operating band is 0.73 dB in case (1), 0.77 dB in case (2), and 0.69 dB in case (3).

[0069] The noise figure of a two-stage amplifier is generally calculated using the following formula: F=F1+(F2-1) / G1...(Formula 1) Here, F is the noise figure of the two-stage amplifier, F1 and F2 are the noise figures of the first and second stage amplifiers, 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 larger the circuit loss of the first stage amplifier, the worse the noise figure of the first stage amplifier will be, resulting in a worse noise figure for the multi-stage amplifier. In other words, if the circuit loss of the first stage amplifier can be reduced, the noise figure of the multi-stage amplifier can be improved even if the total circuit loss of all stages is the same.

[0070] The reason why a lower noise figure was obtained in case (3) than in case (2) is because the resistance value of resistor Rs1 was set larger than that of resistor Rs2, and the resistance value of resistor Rb1 was set smaller than that of resistor Rb2. This makes it possible to suppress the circuit loss of the stabilization circuit S1 and the output bias circuit B2, and to suppress the worst value of the noise figure of the first-stage amplifier within the operating band.

[0071] Based on this technical concept, in the high-frequency amplifier 200 of this embodiment, the resistance value of resistor Rs1 is greater than the resistance value of resistor Rs2, and the resistance value of resistor Rb1 is less than the resistance value of resistor Rb2. This makes it possible to obtain an even lower noise figure while maintaining flat gain characteristics in the band of use, and to further improve the attenuation and attenuation bandwidth in the exclusion band.

[0072] Note that the noise figure can be improved 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 is satisfied. Therefore, high-frequency amplifier 200 may be applied with only one of the following: the resistance values ​​of resistors Rs1 and Rs2 are larger for amplifiers closer to high-frequency input terminal T1, and the resistance values ​​of resistors Rb1 and Rb2 are smaller for amplifiers closer to high-frequency input terminal T1.

[0073] Embodiment 3 This embodiment differs from the first embodiment in that the rejection band is higher than the operating band. Other configurations are the same as those of the first embodiment. The first band-elimination filters BRFm1 and BRFm2 of this embodiment reject power at frequencies higher than the operating band of the amplifier. In other words, the first resonant frequency fr at which the first band-elimination filters BRFm1 and BRFm2 experience the maximum loss is higher than the operating frequency of the amplifier. Furthermore, the second band-elimination filters BRFb1 and BRFb2 reject power at frequencies even higher than those rejected by the first band-elimination filters BRFm1 and BRFm2. In other words, the second resonant frequency fb at which the second band-elimination filters BRFb1 and BRFb2 experience the maximum loss is higher than the first resonant frequency fr of the first band-elimination filters BRFm1 and BRFm2.

[0074] In this embodiment, the resonant frequency fs1 of the LC resonant circuit that constitutes stabilization circuit S1 is set higher than the center value fc of the band used by the amplifier. Furthermore, the resonant frequency fs2 of the LC resonant circuit that constitutes stabilization circuit S2 is set lower than the center value fc of the band used by the amplifier. Thus, the resonant frequencies fs1 and fs2 of bandpass filters BPF1 and BPF2 are higher the closer they are to the high-frequency input terminal T1. From the above, the following equation holds: fs2 <fc<fs1≦fr<fb

[0075] In this embodiment, by providing the second band rejection filters BRFb1 and BRFb2, it is possible to obtain the same effect as in the first embodiment based on the same principle as in the first embodiment.

[0076] In this embodiment, the second resonance frequency fb is higher than the first resonance frequency fr. However, the second resonance frequency fb may be lower than the first resonance frequency fr. In other words, the first resonance frequency fr and the second resonance frequency fb are different from each other, and they may be higher than the operating frequency fc of the amplifier.

[0077] Furthermore, this embodiment may be combined with the second embodiment. That is, one or both of the following conditions may be added: 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. This allows, based on the same principle as the second embodiment, to obtain a lower noise figure while maintaining flat gain characteristics in the band of use, and further improve the attenuation and attenuation bandwidth in the exclusion band.

[0078] Embodiment 4 FIG. 14 shows an embodiment. 4This is a diagram for explaining the configuration of the high-frequency amplifier 300 according to [the relevant content]. In Embodiment 1, the resonance frequencies of the second band rejection filters BRFb1 and BRFb2 were the same, but they may be different. In this embodiment, since the second band rejection filter BRFb2 has an inductor Lb2' and a capacitor Cb2', 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 second resonance frequencies fb and fb' of the amplifier are lower the closer they are to the high-frequency input terminal T1. Other configurations are the same as those in Embodiment 1.

[0079] The resonance frequencies fs1 and fs2 of the band-pass filters BPF1 and BPF2, the center value fc of the used 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. fb < fb' < fr ≦ fs1 < fc < fs2

[0080] Even if the total circuit loss of the multi-stage circuit is the same, by adopting the above configuration, the circuit loss in the used 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 as a 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 band.

[0081] Note that this embodiment and Embodiment 3 may 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. Thereby, a lower noise figure than that in Embodiment 3 can be obtained.

[0082] Embodiment 5. 15 is a diagram illustrating the configuration of a high-frequency amplifier 400 according to a fifth embodiment. In the first embodiment, the input bias power supply terminal T2 and the input bias power supply terminal T4 are provided separately. Also, the output bias power supply terminal T3 and the output bias power supply terminal T5 are provided separately. However, this is not limiting, and a bias may be supplied to multiple amplifiers from a common input bias common power supply terminal Tg. Also, a bias may be supplied to multiple amplifiers from a common output bias common power supply terminal Td.

[0083] This embodiment and the second embodiment may be combined. That is, the resistance value of resistor Rs1 may be greater than the resistance value of resistor Rs2, and the resistance value of resistor Rb1 may be less than the resistance value of resistor Rb2. For example, consider a case where the voltage at which the noise figure, gain, or other characteristics are optimized is the same for transistors Tr1 and Tr2 because the transistors Tr1 and Tr2 have the same gate width. In this case, it is preferable to set each resistance value so that the sum of the resistance values ​​of resistors Rs1 and Rb1 is equal to the sum of the resistance values ​​of resistors Rs2 and Rb2.

[0084] As a result, the voltage drop caused by resistors Rs1 and Rb1, and resistors Rs2 and Rb2, is equal to the voltage applied to the output bias common power supply terminal Td from the power supply of the module in which the high-frequency amplifier 400 is incorporated. Therefore, both transistors Tr1 and Tr2 can be operated at a voltage that optimizes characteristics such as noise figure or gain.

[0085] In this manner, in this embodiment, the input bias power supply terminal and the output bias power supply terminal are common to the amplifiers of each stage, thereby simplifying the terminal configuration and miniaturizing the circuit. Furthermore, by setting the resistance values ​​as described above, it is possible to obtain the same effects as those shown in the first to fourth embodiments.

[0086] As described in the second embodiment, the circuit loss of each amplifier has opposite characteristics relative to the resistance values ​​of the two resistors in the amplifier. These two resistors are connected in series between the output bias common power supply terminal Td and the transistor output terminal. This relationship and arrangement produces the above-mentioned effects. Specifically, in the amplifier located closest to the high-frequency input terminal T1, the circuit loss can be reduced by increasing the resistance value of resistor Rs1 and decreasing the resistance value of resistor Rb1. Similarly, in the amplifier located farthest from the high-frequency input terminal T1, the resistance value of resistor Rs2 can be reduced and the resistance value of resistor Rb2 can be increased. This allows the sum of the resistance values ​​to be kept constant across all amplifiers, while both transistors Tr1 and Tr2 can be operated at voltages that optimize characteristics such as noise figure and gain.

[0087] In other words, the above-mentioned effect cannot be obtained simply by providing a stabilization circuit in each stage, in which a band-pass filter and a resistor are connected in parallel.Similarly, the above-mentioned effect cannot be obtained simply by providing an output bias circuit in each stage, in which a band-elimination filter and a resistor are connected in series.

[0088] Embodiment 6 16 is a diagram illustrating the configuration of a high-frequency amplifier 500 according to a sixth embodiment. The high-frequency amplifier 500 of this embodiment includes three amplifier stages. Although the first to fifth embodiments have mainly described two-stage amplifiers, the first to fifth embodiments may also be applied to a high-frequency multistage low-noise amplifier in which three or more amplifier stages are connected in series.

[0089] 16, the first-stage amplifier is comprised of an input matching circuit M1 to an output matching circuit M2, the second-stage amplifier is comprised of an input matching circuit M3 to an output matching circuit M4, and the third-stage amplifier is comprised of an input matching circuit M5 to an output matching circuit M6. Interstage capacitors C1 and C2 are connected between the stages. The configurations of the first and second-stage amplifiers are the same as those in the first embodiment.

[0090] The third-stage amplifier has a configuration similar to that of the first-stage amplifier. It 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. It also includes a stabilization circuit S3, a first band-elimination filter BRFm3, an output bias circuit B6, an output bias power supply terminal T8, and an output matching circuit M6.

[0091] In the stabilization circuit S3, a series resonant circuit consisting of an inductor Ls3 and a capacitor Cs3, which resonates at a frequency fs3, is connected in parallel with a resistor Rs3. In the first band-elimination filter BRFm3, a series resonant circuit consisting of an inductor Lr3 and a capacitor Cr3 is shunt-connected. For example, the inductor Lr3 has the same inductance as the inductor Lr1. For example, the capacitor Cr3 has the same capacitance as the capacitor Cr1. Therefore, the resonant frequency of the first band-elimination filter BRFm3 is equal to the resonant frequency fr of the first band-elimination filter BRFm1.

[0092] In the output bias circuit B6, a resistor Rb3 and an inductor Lb3 are connected in series to the bias path to the transistor Tr3. A capacitor Cb3 is also shunt-connected to the bias path. The resistor Rb3 has, for example, the same resistance 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 as the capacitor Cb1. Therefore, the resonant frequency of the second band-elimination filter BRFb3, which is formed by the inductor Lb3 and the capacitor Cb3, is equal to the resonant frequency fb of the second band-elimination filter BRFb1.

[0093] When a band-elimination filter with a resonant frequency lower than the operating band of the amplifier is placed, the resonant frequency of the series resonant circuit that makes up the stabilization circuit is set lower the closer the amplifier stage is to the high-frequency input terminal T1. In other words, the resonant frequency of the band-pass filter is lower the closer it is to the high-frequency input terminal T1. This can be expressed as the following formula: fb <fr≦fs1<fs2<fs3

[0094] On the other hand, when a band-elimination filter with a resonant frequency higher than the operating band of the amplifier is placed, the resonant frequency of the series resonant circuit that makes up the stabilization circuit is set higher the closer the amplification stage is to the high-frequency input terminal T1. In other words, the resonant frequency of the band-pass filter is higher the closer it is to the high-frequency input terminal T1. This can be expressed as the following equation: fs3 <fs2<fs1≦fr<fb

[0095] According to this embodiment, as in the first to fifth embodiments, it is possible to increase the attenuation and attenuation bandwidth in the exclusion band while maintaining the noise figure and gain deviation from the low end to the high end of the usable band.

[0096] Next, a case where the technical idea of ​​the second embodiment is incorporated into the present embodiment will be described. In this case, the resistance values ​​of the resistors constituting the stabilization circuit are set to be larger the closer they are to the radio frequency input terminal T1, and the resistance values ​​of the resistors constituting the output bias circuit are set to be smaller the closer they are to the radio frequency input terminal T1. That is, 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.

[0097] The noise figure of an n-stage amplifier is calculated by Equation 2, which is an extension of Equation 1. F=F1+(F2-1) / G1+(F3-1) / G1G2+…+(Fn-1) / G1G2…Gn-1 (Formula 2) 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.

[0098] According to Equation 2, even if the total circuit loss of the multistage circuit is the same, the larger the circuit loss of the amplifier closer to the high-frequency input terminal T1, the worse the noise figure of that amplifier, and therefore the worse the noise figure of the multistage amplifier. In other words, if the circuit loss of the amplifier closer to the high-frequency input terminal can be reduced, the noise figure of the multistage amplifier can be improved even if the total circuit loss of all stages is the same.

[0099] As explained above, in a high-frequency amplifier in which three or more stages of amplifiers are connected in series, it is preferable that the resistance value of the resistor in the stabilization circuit be larger the closer it is to the high-frequency input terminal T1, and that the resistance value of the resistor in the output bias circuit be smaller the closer it is to the high-frequency input terminal T1.

[0100] In the first to sixth embodiments, the stabilization circuit, the first band-elimination filter, and the output bias circuit having the second band-elimination filter may be disposed in all amplifiers constituting the high-frequency amplifier, or may be disposed in only certain amplifiers. The features of the amplifiers described in each embodiment may be applied to at least two of the amplifiers included in the multistage circuit. In other words, when the multistage circuit includes three or more amplifiers, the features of any of the amplifiers described in the first to sixth embodiments may be applied to any two or more of the amplifiers. For example, the technology according to the present embodiment may be applied to the first to third stage amplifiers of a four-stage amplifier, and any of the elements of the stabilization circuit, the first band-elimination filter, and the output bias circuit may not be disposed in the fourth stage amplifier.

[0101] The technical features described in each embodiment may be used in appropriate combination. [Explanation of symbols]

[0102] 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 Interstage 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 resistors, 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 transistors

Claims

1. A high frequency input terminal; A high frequency output terminal; a plurality of amplifiers each having a transistor and connected in series, the amplifiers being provided between the high frequency input terminal and the high frequency output terminal; a stabilization circuit provided in at least two amplifiers among the plurality of amplifiers; a first band rejection filter provided to the at least two amplifiers; an output bias circuit provided in each of the at least two amplifiers to supply a bias to an output terminal of the corresponding transistor; Equipped with each of the stabilization circuits includes a band-pass filter and a first resistor connected in parallel with the band-pass filter, and is provided between the output terminal of the corresponding transistor and the high-frequency output terminal; each of the first band-elimination filters has a first resonant frequency and is provided between the output terminal of the corresponding transistor and the high-frequency output terminal; each said output bias circuit having a second band rejection filter having a second resonant frequency; A high-frequency amplifier characterized in that, in the at least two amplifiers, the first resonant frequency and the second resonant frequency are different from each other and lower than the operating frequency of the amplifier, or the first resonant frequency and the second resonant frequency are different from each other and higher than the operating frequency of the amplifier.

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

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

4. 4. The high frequency amplifier according to claim 2, wherein the second resonant frequency is lower than the first resonant frequency in the at least two amplifiers.

5. 4. The high-frequency amplifier according to claim 2, wherein the second resonant frequencies of the at least two amplifiers are lower as they are closer to the high-frequency input terminal.

6. 2. The high frequency amplifier according to claim 1, wherein in the at least two amplifiers, the first resonant frequency is higher than the operating frequency.

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

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

9. 8. The high-frequency amplifier according to claim 6, wherein the second resonant frequencies of the at least two amplifiers are higher as they are closer to the high-frequency input terminal.

10. 4. The high frequency amplifier according to claim 1, wherein the resistance value of the first resistor of the stabilization circuit of the at least two amplifiers is larger in an amplifier closer to the high frequency input terminal.

11. each said output bias circuit having a second resistor connected in series with said second band rejection filter; 4. The high-frequency amplifier according to claim 1, wherein the resistance value of the second resistor of the output bias circuit of the at least two amplifiers is smaller in an amplifier closer to the high-frequency input terminal.

12. each said output bias circuit having a second resistor connected in series with said second band rejection filter; 4. The high-frequency amplifier according to claim 1, wherein, in the at least two amplifiers, the resistance value of the first resistor of the stabilization circuit is larger in an amplifier closer to the high-frequency input terminal, and the resistance value of the second resistor of the output bias circuit is smaller in an amplifier closer to the high-frequency input terminal.

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

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

Images