Linearizer

Abstract

To provide a linearizer circuit configuration even in a frequency band of 100 GHz or more.SOLUTION: A linearizer according to the present invention is connected to a transmission path to an input terminal of an amplifier that takes a high-frequency signal as an input signal. The linearizer according to the present invention includes a diode or transistor, a transmission line, and a DC power supply. The anode of the diode or the base of the transistor is connected to the transmission path. The transmission line is placed between the cathode of the diode or the emitter of the transistor and ground. The DC power supply applies a bias voltage to the input terminal.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a linearizer that compensates for distortion in an amplifier that receives a high-frequency signal as an input signal. [Background technology]

[0002] Electrical communications, particularly wireless communications, require amplifiers to boost the power of transmitted waves in order to ensure the signal-to-noise ratio (SNR) required for communications. Nonlinear distortion (especially third-order intermodulation distortion: IM3) generated in amplifiers causes degradation of signal quality (specifically, a drop in SNR). Linearizers are known as electronic circuits that compensate for distortion, and are applied to cellular amplifiers using frequency bands from several hundred MHz to several GHz. The technology shown in Patent Document 1 is an example of a linearizer, while Non-Patent Document 1 generally describes methods for achieving low distortion and high efficiency in amplifiers.

[0003] FIG. 1 shows a conventional linearizer using diodes. The operating principle of this linearizer is to compensate for amplifier distortion using diodes, taking advantage of the fact that the amplifier and diode have opposite AM-AM (Amplitude-Amplitude Distortion) and AM-PM (Amplitude-Phase Distortion) characteristics. The linearizer 800 shown in FIG. 1 is disposed between the amplifier 900 and a capacitor 910 that passes only the AC component of the input signal. The linearizer 800 is disposed between the input terminal of the amplifier 900 and ground. The linearizer 800 includes a diode 820 and a DC power supply 840. The anode terminal of the diode 820 is connected to the main transmission path of the high-frequency signal (the wiring between the capacitor 910 and the amplifier 900 in FIG. 1). The cathode terminal of the diode 820 is connected to ground. The DC power supply 840 applies a bias voltage to the input terminal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 179087 [Non-patent literature]

[0005] [Non-Patent Document 1] Masatoshi Nakayama, Nao Takagi, "Methods for low distortion and high efficiency of power amplifiers," [Retrieved February 14, 2022], Internet<https: / / www.apmc-mwe.org / mwe2005 / src / TL / TL03-02.pdf> . Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the frequency band of 100 GHz or higher, which is expected to be put into practical use in 6G and beyond, there is a problem that it is difficult to realize a linearizer because the high frequency causes significant imperfections in the linearizer circuit (such as characteristic degradation due to parasitic capacitance).The present invention aims to provide a linearizer circuit configuration even in the frequency band of 100 GHz or higher. [Means for solving the problem]

[0007] The linearizer of the present invention is connected to a transmission path leading to the input terminal of an amplifier that receives a high-frequency signal as an input signal. The linearizer of the present invention includes a diode or a transistor, a transmission line, and a DC power supply. The anode of the diode or the base of the transistor is connected to the transmission path. The transmission line is disposed between the cathode of the diode or the emitter of the transistor and ground. The DC power supply applies a bias voltage to the input terminal. [Effects of the Invention]

[0008] According to the linearizer of the present invention, it is possible to set the linearizer characteristics due to the resonance phenomenon between the parasitic capacitance of the diode or transistor and the transmission line so as to cancel the amplifier characteristics, thereby providing a linearizer circuit configuration even in frequency bands of 100 GHz or higher. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a linearizer known in the prior art. [Figure 2] FIG. 1 is a diagram showing a circuit including a first linearizer of the present invention. [Figure 3] FIG. 10 is a diagram showing a circuit including a second linearizer of the present invention. [Figure 4] FIG. 10 is a graph showing the simulation results of the change in the amplitude of S21 relative to the input power (AM-AM characteristics) when the electrical length of the transmission line at 100 GHz is changed. [Figure 5] FIG. 10 shows the simulation results of the change in the phase of S21 relative to the input power (AM-PM characteristics) when the electrical length of the transmission line at 100 GHz is changed. [Figure 6] FIG. 10 is a graph showing the simulation results of the relationship between the input signal strength and the S21 deviation at 100 GHz. [Figure 7] FIG. 10 is a diagram showing the results of a simulation of the relationship between the intensity and amplitude deviation of an output signal at 100 GHz when the linearizer of the present invention is added to an amplifier, when a conventional linearizer is added, and when only an amplifier is used. [Figure 8] FIG. 10 is a diagram showing the results of a simulation of the relationship between the intensity and phase deviation of an output signal at 100 GHz when the linearizer of the present invention is added to an amplifier, when a conventional linearizer is added, and when only an amplifier is used. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail. Components having the same functions are given the same numbers, and duplicated explanations will be omitted. [Example]

[0011] FIG. 2 shows a circuit including a first linearizer of the present invention. The linearizer 100 is connected to a transmission path (the wiring between the capacitor 910 and the amplifier 920 in FIG. 2) to the input terminal of an amplifier 920, which receives a high-frequency signal as an input signal. The linearizer 100 includes a transistor 110, a transmission line 130, and a DC power supply 200. The linearizer 100 may also include a resistor 120. Since the circuit including the linearizer 100 handles signals of 100 GHz or higher, it is formed using an integrated circuit. In principle, the linearizer 100 can also be configured using bipolar transistors or field-effect transistors by utilizing the diode characteristics of the transistors. This specification describes a configuration using bipolar transistors.

[0012] The base of the transistor 110 is connected to the transmission path. "Connection" means electrical connection. The transmission line 130 is disposed between the emitter of the transistor 110 and ground. In other words, one end of the transmission line 130 is connected to the emitter of the transistor 110, and the other end is connected to ground. The transmission line 130 may be selected to have an appropriate electrical length at 100 GHz. For example, the electrical length may be selected to be 90 degrees or less. Although it depends on the dielectric constant of the substrate, it may be formed of indium phosphide (InP) or the like with a physical length of several hundred microns. The specific electrical length will be described later.

[0013] The resistor 120 may be placed between the collector of the transistor 110 and ground. In other words, one end of the resistor 120 may be connected to the collector of the transistor 110, and the other end may be connected to ground. In order to stabilize the potential of the collector terminal at high frequencies, the resistor 130 may be a resistor having a resistance value (for example, a value greater than several kΩ) that is sufficiently higher than the ON resistance of the diode, thereby connecting the collector terminal to the ground potential. The DC power supply 200 applies a bias voltage to the input terminal.

[0014] Figure 3 shows a circuit including a second linearizer of the present invention. Linearizer 101 is connected to a transmission path (the wiring between capacitor 910 and amplifier 920 in Figure 3) to the input terminal of amplifier 920, which receives a high-frequency signal as an input signal. Linearizer 101 includes diode 820, transmission line 130, and DC power supply 200. Since the circuit including linearizer 101 handles signals of 100 GHz or higher, it is formed as an integrated circuit. Diode 820 may be a diode element such as a Schottky barrier diode or a PN diode.

[0015] The anode of the diode 820 is connected to the transmission path. The transmission line 130 is disposed between the cathode of the diode 820 and the ground. In other words, one end of the transmission line 130 is connected to the cathode of the diode 820, and the other end is connected to the ground. The characteristic impedance and electrical length of the transmission line 130 at 100 GHz may be appropriately selected. For example, the electrical length may be selected from those of 90 degrees or less. Although it depends on the dielectric constant of the substrate, it may be formed of indium phosphide (InP) or the like with a physical length of several hundred microns. The specific electrical length will be described later.

[0016] The DC power supply 201 applies a bias voltage to the input terminal. To properly operate the linearizer 101 using the diode 820, it is necessary to set the anode-cathode bias of the diode 820 within an appropriate voltage range. In the linearizer 101, the DC power supply 201 should bias the anode-cathode bias to near the threshold voltage of the diode so that the impedance of the diode seen by the high-frequency signal (i.e., the impedance seen from the transmission path in FIG. 3 to the anode terminal of the diode) changes most significantly with changes in the high-frequency input power to the linearizer.

[0017] FIG. 4 shows the S when the electrical length of the transmission line 130 in the linearizer 100 is changed at 100 GHz. 21 The figure shows the simulation results of the change in amplitude of S with respect to the input power (AM-AM characteristics). The horizontal axis is the input voltage, and the vertical axis is S 21The numbers (0, 30, 50, etc.) on the right side of Figure 4 indicate the angle of the electrical length. For example, 30 indicates the case where the electrical length is 30 degrees. The results for electrical lengths of 0 degrees and 180 degrees overlap.

[0018] FIG. 5 shows the S when the electrical length of the transmission line 130 in the linearizer 100 is changed at 100 GHz. 21 The figure shows the simulation results of the change in the phase of the S with respect to the input power (AM-PM characteristics). The horizontal axis is the input voltage, and the vertical axis is S 21 The numbers (0, 30, 50, etc.) on the right side of Figure 5 indicate the angle of the electrical length. For example, 30 indicates the case where the electrical length is 30 degrees. The results for electrical lengths of 0 degrees and 180 degrees overlap.

[0019] 4 and 5, when the electrical length is set to 60°, the linearizer 100 has the inverse characteristics of the AM-AM characteristics (which usually decline with increasing input power) and AM-PM characteristics (which, in the case of an amplifier made up of transistors, usually decline with increasing input power) of the amplifier 920, and can therefore compensate for the distortion of the amplifier 920.

[0020] Figure 6 shows the relationship between the input signal strength and S at 100 GHz. 21 The figure shows the simulation results of the relationship between the deviation and the input signal strength. The horizontal axis is the input signal strength. The vertical axis is the S parameter S. 21 (phase), the input signal is at its lowest S 21The characteristic of the amplifier 920 alone changes in the negative direction when it exceeds -20 dBm. On the other hand, the characteristic of the linearizer 100 alone changes in the positive direction when it exceeds -20 dBm. This linearizer characteristic is realized by making the electrical length of the transmission line 130 about 60° and utilizing the resonance phenomenon between the parasitic capacitance of the transistor 110 and the transmission line 130. This characteristic makes it possible to cancel out the characteristics of the amplifier 920 by combining the linearizer 100 and the amplifier 920. The length of the transmission line 130 can be determined appropriately so that the characteristics of the linearizer 100 become the inverse characteristics of the amplifier 920. More specifically, the length of the transmission line 130 should be determined so that the characteristics of the linearizer 100 due to the resonance phenomenon between the parasitic capacitance of the transistor 110 and the transmission line 130 cancel out the characteristics of the amplifier 920 in terms of the AM-AM characteristics (Amplitude-Amplitude Distortion) and the AM-PM characteristics (Amplitude-Phase Distortion).

[0021] Figure 7 shows the simulation results of the relationship between the output signal strength and amplitude deviation at 100 GHz when the linearizer of the present invention is added to an amplifier, when a conventional linearizer is added, and when only the amplifier is used. When the conventional linearizer is added and when only the amplifier is used, the tendency of the amplitude deviation is almost the same, and the linearizer effect is not apparent. On the other hand, when the linearizer of the present invention is added, the amount of amplitude deviation is small even when the output signal is high. Compared to when only the amplifier is used and when a conventional linearizer is added, the addition of the linearizer of the present invention improves the 1 dB gain compression point output power (OP1 dB) by 1.4 dB. Figure 8 shows the simulation results of the relationship between the output signal strength and phase deviation at 100 GHz when the linearizer of the present invention is added to an amplifier, when a conventional linearizer is added, and when only the amplifier is used. When the conventional linearizer is added and when only the amplifier is used, the tendency of the phase deviation, like the amplitude deviation, is almost the same, and the linearizer effect is not apparent. By adding the linearizer of the present invention, the output signal can be improved by 2.6 dB when the absolute value of the phase deviation exceeds 5°, compared to when a conventional linearizer is added or when only an amplifier is used.

[0022] According to the linearizer of the present invention, it is possible to set the linearizer characteristics due to the resonance phenomenon between the parasitic capacitance of the diode or transistor and the transmission line so as to cancel the amplifier characteristics, thereby providing a linearizer circuit configuration even in frequency bands of 100 GHz or higher. [Explanation of symbols]

[0023] 100,101 Linearizer 110 Transistor 120 Resistor 130 Transmission line 200,201 DC power supply 800 Linearizer 820 Diode 840 DC power supply 900,920 Amplifier 910 Capacitor

Claims

[Claim 1] A linearizer connected to a transmission path to an input terminal of an amplifier that receives a high-frequency signal as an input signal, a transistor having a base connected to the transmission path; a transmission line disposed between the emitter of the transistor and ground; a resistor disposed between the collector of the transistor and ground; a DC power supply that applies a bias voltage to the input terminal; A linearizer comprising:

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