JP5191221B2 - Low temperature receiver amplifier - Google Patents

Low temperature receiver amplifier Download PDF

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JP5191221B2
JP5191221B2 JP2007309239A JP2007309239A JP5191221B2 JP 5191221 B2 JP5191221 B2 JP 5191221B2 JP 2007309239 A JP2007309239 A JP 2007309239A JP 2007309239 A JP2007309239 A JP 2007309239A JP 5191221 B2 JP5191221 B2 JP 5191221B2
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receiving amplifier
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JP2009010910A (en
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恭宜 鈴木
祥一 楢橋
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NTT Docomo Inc
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Description

本発明は、無線通信基地局受信系などに用いる低温受信増幅器に関する。 The present invention relates to a cryogenic receiving amplifier device used for such a wireless communication base station reception system.

極低温の環境で動作する増幅器として、衛星地球局用受信増幅器、電波天文用受信増幅器などが例示される（非特許文献１）。また、移動通信基地局受信系統への超伝導フィルタの適用も検討されており、超伝導フィルタおよび低温受信増幅器で極低温受信フロントエンドを構成している（非特許文献２）。これらの冷却には液体窒素、液体ヘリウムまたは真空容器が用いられ、受信フロントエンドは１０数Ｋから６０Ｋ程度まで冷却される。いずれも冷却によって受信増幅器を低雑音にすることで受信感度を高めている。   Examples of amplifiers that operate in a cryogenic environment include satellite earth station reception amplifiers and radio astronomy reception amplifiers (Non-Patent Document 1). In addition, application of a superconducting filter to a mobile communication base station receiving system is also being studied, and a cryogenic receiving front end is configured with a superconducting filter and a low-temperature receiving amplifier (Non-patent Document 2). Liquid nitrogen, liquid helium, or a vacuum vessel is used for these cooling operations, and the reception front end is cooled to about 10 to 60K. In either case, the receiving sensitivity is increased by reducing the noise of the receiving amplifier by cooling.

低雑音化を目的とする極低温受信増幅器に用いられるマイクロ波半導体として、高電子移動度トランジスタ（HEMT：High Electron Mobility Transistor）または電界効果トランジスタ（FET：Field Effect Transistor）が用いられている（非特許文献３）。一般にHEMTの方がFETよりも冷却時の低雑音特性が優れることが知られている（非特許文献４）。また、代表的なHEMTの材料として、ガリウム砒素（GaAs）が用いられている。GaAs HEMTでは、０．３ｄＢ程度の雑音指数を得ることができるが、飽和出力が１５ｄＢｍ程度である。これに対して、GaAs FETはGaAs HEMTほどの低い雑音指数を得ることはできないが、３５ｄＢｍ程度の飽和出力を得ることができる。   High microwave mobility transistors (HEMTs) or field effect transistors (FETs) are used as microwave semiconductors used in cryogenic receiver amplifiers for noise reduction (non-effect transistors) Patent Document 3). In general, it is known that HEMT has better low noise characteristics during cooling than FET (Non-patent Document 4). Further, gallium arsenide (GaAs) is used as a typical HEMT material. With GaAs HEMT, a noise figure of about 0.3 dB can be obtained, but the saturation output is about 15 dBm. On the other hand, GaAs FET cannot obtain a noise figure as low as GaAs HEMT, but can obtain a saturation output of about 35 dBm.

移動通信基地局用の極低温受信増幅器として、それぞれのトランジスタの特長を組み合わせることが検討されている（非特許文献５）。非特許文献５では、初段にGaAs HEMT、２段目にGaAs FET、３段目にGaAs FETを用いた３段増幅器構成による極低温受信増幅器が提案されている。この例では、初段の低雑音指数のHEMTと２段目以降の高飽和出力のFETを組み合わせることで、低雑音指数かつ高い飽和出力を達成している。非特許文献５によれば、雑音指数０．２５ｄＢ、利得４３ｄＢ、出力インターセプトポイント３８．５ｄＢｍ、最大電力付加効率１５％以下である。移動通信基地局用の受信系統では、セル内の遠近差のある移動端末の電波を同時に増幅するため、１Ｗから２Ｗ程度の出力インターセプトポイントが必要である。   Combining the features of each transistor as a cryogenic receiving amplifier for a mobile communication base station is being studied (Non-patent Document 5). Non-Patent Document 5 proposes a cryogenic receiving amplifier having a three-stage amplifier configuration using GaAs HEMT in the first stage, GaAs FET in the second stage, and GaAs FET in the third stage. In this example, a low noise figure and a high saturation output are achieved by combining the first stage low noise figure HEMT and the second and subsequent high saturation output FETs. According to Non-Patent Document 5, the noise figure is 0.25 dB, the gain is 43 dB, the output intercept point is 38.5 dBm, and the maximum power added efficiency is 15% or less. In a receiving system for a mobile communication base station, an output intercept point of about 1 W to 2 W is required to simultaneously amplify radio waves of mobile terminals having a difference in distance within a cell.

近年、窒化ガリウム高電子移動度トランジスタ（以下、GaN HEMTとも表記する。）が高出力マイクロ波半導体として盛んに研究されている。GaN HEMTの特徴は、GaAs FETに比較して高電圧動作が可能であることにある。このため高負荷インピーダンスにて増幅器を構成できることから、整合回路の損失低減を図れる。また、GaN HEMTには動作温度を高く設定できる利点がある。即ち、GaN HEMTの熱容量が大きい特徴がある。このためGaN HEMTで許容できない熱を外部に取り除く放熱器を小さくでき、増幅器全体の小型化・軽量化を図れる（非特許文献６）。これらの特徴から、GaN HEMTは、常温で使用される高出力マイクロ波半導体として基地局用送信増幅器への適用が盛んに検討されている。
浜部，斉藤，大村，耳野，”極低温冷却HEMT増幅器”，電子情報通信学会技術研究報告(電子デバイス)，ED88-122, Jan. 1989. T. Nojima, S. Narahashi, T. Mimura, K. Satoh, Y. Suzuki, “2-GHz band cryogenic receiver front end for mobile communication base station systems”, IEICE Transactions on Communications, vol. E83-B, no. 9, pp. 1834-1843, Aug. 2000. M. W. Pospieszalski, S. Weinreb, R. D. Norrod, and R. Harris, “FET’s and HEMT’s at cryogenic temperatures --- their properties and use in low-noise amplifiers--- “, IEEE Transactions on Microwave Theory and Techniques, vol. 36, no. 3, pp. 552-560, March 1988. K. H. G. Duh, M. W. Pospieszalski, W. F. Kopp, A. A. Jabra, P-C Chao, P. M. Smith, L .F. Lester, J. M. Ballingall, and S. Weinreb, “Ultra-low-noise cryogenic high-electron-mobility transistors”, IEEE Transactions on Electron Devices, vol. 35, no. 3, pp.249-256, March 1988. 三村，楢橋，野島，”移動通信受信用２ＧＨｚ帯極低温３段増幅器”，1999年電子情報通信学会総合大会，B-5-31，March 1999. T. Kikkawa, and K. Joshin, “High power GaN-HEMT for wireless base station applications”, IEICE Transactions on Electron., vol. E89-C, no. 5, pp. 608-615, May 2006. In recent years, a gallium nitride high electron mobility transistor (hereinafter also referred to as GaN HEMT) has been actively studied as a high-power microwave semiconductor. The feature of GaN HEMT is that it can operate at a higher voltage than GaAs FET. For this reason, the amplifier can be configured with a high load impedance, so that the loss of the matching circuit can be reduced. In addition, GaN HEMT has the advantage that the operating temperature can be set high. That is, GaN HEMT has a large heat capacity. For this reason, it is possible to reduce the size of the radiator that removes heat that cannot be tolerated by GaN HEMT to the outside, and to reduce the size and weight of the entire amplifier (Non-Patent Document 6). Because of these characteristics, GaN HEMTs are actively studied for application to transmission amplifiers for base stations as high-power microwave semiconductors used at room temperature.
Hamabe, Saito, Omura, Aino, "Cryogenically cooled HEMT amplifier", IEICE Technical Report (Electronic Devices), ED88-122, Jan. 1989. T. Nojima, S. Narahashi, T. Mimura, K. Satoh, Y. Suzuki, “2-GHz band cryogenic receiver front end for mobile communication base station systems”, IEICE Transactions on Communications, vol. E83-B, no. 9, pp. 1834-1843, Aug. 2000. MW Pospieszalski, S. Weinreb, RD Norrod, and R. Harris, “FET's and HEMT's at cryogenic temperatures --- their properties and use in low-noise amplifiers ---“, IEEE Transactions on Microwave Theory and Techniques, vol. 36 , no. 3, pp. 552-560, March 1988. KHG Duh, MW Pospieszalski, WF Kopp, AA Jabra, PC Chao, PM Smith, L .F.Lester, JM Ballingall, and S. Weinreb, “Ultra-low-noise cryogenic high-electron-mobility transistors”, IEEE Transactions on Electron Devices, vol. 35, no. 3, pp.249-256, March 1988. Mimura, Takahashi, Nojima, "2 GHz band cryogenic 3-stage amplifier for mobile communication reception", 1999 IEICE General Conference, B-5-31, March 1999. T. Kikkawa, and K. Joshin, “High power GaN-HEMT for wireless base station applications”, IEICE Transactions on Electron., Vol. E89-C, no. 5, pp. 608-615, May 2006.

従来の極低温受信増幅器は、線形性と低雑音指数を維持するためにＡ級バイアスで用いられていた。また、１０ｄＢｍから２０ｄＢｍ程度の低い飽和出力のトランジスタを用いていることから、十分に高い電力付加効率を得られなかった。さらに、１Ｗ以上の高い飽和出力を達成するには３段以上の段数が必要だった。そして、多段の極低温受信増幅器の低消費電力化のために、２段目以降のFETのバイアス電圧をＡＢ級またはＢ級に設定すると、極低温受信増幅器の総合線形性が劣化する課題もあった。線形性と電力付加効率はトレードオフの関係にあることから、従来のＡ級バイアス電圧設定のFETを用いた極低温受信増幅器構成では、飽和出力１Ｗ以上かつ電力付加効率５０％（Ａ級バイアスでの理論最大値）以上を達成できなかった。   Conventional cryogenic receiver amplifiers have been used with class A bias to maintain linearity and low noise figure. Further, since a transistor with a low saturation output of about 10 dBm to 20 dBm is used, a sufficiently high power added efficiency cannot be obtained. Furthermore, in order to achieve a high saturation output of 1 W or more, three or more stages were required. And, in order to reduce the power consumption of multi-stage cryogenic receiver amplifiers, if the bias voltage of FETs in the second and subsequent stages is set to class AB or class B, there is a problem that the total linearity of the cryogenic receiver amplifier deteriorates. It was. Since linearity and power added efficiency are in a trade-off relationship, the conventional cryogenic receiver amplifier configuration using a class A bias voltage setting FET has a saturation output of 1 W or more and power added efficiency of 50% (with class A bias). (Theoretical maximum value) could not be achieved.

本発明は、飽和出力１Ｗ以上かつ電力付加効率５０％以上を達成できる低温受信増幅器を提供することを目的とする。
The present invention aims to provide a cryogenic receiving amplifier device that can achieve saturation output 1W or more and the power added efficiency of 50% or more.

本発明の低温受信増幅器は、窒化ガリウム高電子移動度トランジスタを極低温の環境で増幅素子として用いる。そして、増幅素子のゲートと入力端子の外部とのインピーダンス整合を行う入力整合回路と、増幅素子のゲートに直流電圧を印加するゲートバイアス回路と、増幅素子のドレインと出力端子の外部とのインピーダンス整合を行う出力整合回路と、増幅素子のドレインに直流電圧を印加するドレインバイアス回路とを備える。ゲートバイアス回路は、分圧された抵抗値が極低温でのゲート抵抗に整合されている抵抗分圧回路を有するようにすればよい。   The low-temperature receiving amplifier of the present invention uses a gallium nitride high electron mobility transistor as an amplifying element in a cryogenic environment. An input matching circuit that performs impedance matching between the gate of the amplification element and the outside of the input terminal, a gate bias circuit that applies a DC voltage to the gate of the amplification element, and impedance matching between the drain of the amplification element and the outside of the output terminal And an output matching circuit for performing the above and a drain bias circuit for applying a DC voltage to the drain of the amplifying element. The gate bias circuit may have a resistance voltage dividing circuit in which the divided resistance value is matched with the gate resistance at an extremely low temperature.

また、ガリウム砒素高電子移動度トランジスタを極低温の環境で増幅素子として用いた低温受信増幅器を初段とし、窒化ガリウム高電子移動度トランジスタを極低温の環境で増幅素子として用いた低温受信増幅器を２段目とすることで、２段の低温受信増幅器を構成することもできる。   In addition, a low temperature receiving amplifier using a gallium arsenide high electron mobility transistor as an amplifying element in a cryogenic environment is used as a first stage, and a low temperature receiving amplifier using a gallium nitride high electron mobility transistor as an amplifying element in a cryogenic environment is used. By using the stage, a two-stage low-temperature receiving amplifier can be configured.

また、好ましくは、本発明の低温受信増幅器を１５０Ｋ以下に冷却する。   Preferably, the low-temperature receiving amplifier of the present invention is cooled to 150K or less.

また、窒化ガリウム高電子移動度トランジスタに、窒化ガリウムのバンドギャップに相当する波長の光を照射する発光手段Ａ、または、可視スペクトルの青色領域に相当する波長の光（青色光）を照射する発光手段Ｂ、または、前記青色光を含む光を照射する発光手段Ｃを備えるとしてもよい。このような発光手段によって、窒化ガリウム高電子移動度トランジスタに、窒化ガリウムのバンドギャップに相当する波長の光、または、可視スペクトルの青色領域に相当する波長の光（青色光）、または、青色光を含む光を照射することで、低温環境下で生じる電流崩壊現象（Current Collapse Environment）による窒化ガリウム高電子移動度トランジスタのドレイン−ソース間電流の減少を改善することができる。なお、発光手段Ａ、または、前記発光手段Ｂ、または、前記発光手段Ｃは、青色発光ダイオードとすることができる。   Further, light emission means A for irradiating light with a wavelength corresponding to the band gap of gallium nitride to the gallium nitride high electron mobility transistor, or light emission for irradiating light with a wavelength corresponding to the blue region of the visible spectrum (blue light) Means B or light emitting means C for irradiating light including the blue light may be provided. By such a light emitting means, light having a wavelength corresponding to the band gap of gallium nitride, light having a wavelength corresponding to the blue region of the visible spectrum (blue light), or blue light can be applied to the gallium nitride high electron mobility transistor. By irradiating light containing gallium nitride, the reduction in the drain-source current of the gallium nitride high electron mobility transistor due to the current collapse environment occurring in a low temperature environment can be improved. The light emitting means A, the light emitting means B, or the light emitting means C can be a blue light emitting diode.

そして、窒化ガリウム高電子移動度トランジスタのドレイン−ソース間電流をモニタする回路と、このモニタした電流を積分する積分器と、この積分器の出力と基準電流値との差を求める比較器と、この比較器の出力を０にするように青色発光ダイオードの順方向電流を制御する制御器とを含む構成としてもよい。低温環境下でドレイン−ソース間電流は長時間にわたって緩慢に増減することから、ドレイン−ソース間電流をモニタして青色発光ダイオードの順方向電流を制御して光の照射を行うようにする。   A circuit for monitoring a drain-source current of the gallium nitride high electron mobility transistor, an integrator for integrating the monitored current, a comparator for obtaining a difference between an output of the integrator and a reference current value, It may be configured to include a controller that controls the forward current of the blue light emitting diode so that the output of the comparator is zero. Since the drain-source current slowly increases and decreases over a long period of time in a low temperature environment, the drain-source current is monitored, and the forward current of the blue light emitting diode is controlled to perform light irradiation.

本発明では、マイクロ波トランジスタとして、窒化ガリウム高電子移動度トランジスタ（GaN HEMT）を用いている。GaN HEMTは、高いドレイン電圧（５０Ｖ以上）で動作することができるので、出力整合回路を比較的高インピーダンスで構成できる利点がある。また、GaN HEMTの飽和出力は数Ｗ以上であり、線形性と電力付加効率にも優れている。さらに、極低温環境でのゲート抵抗に整合するゲートバイアス回路によって、高利得なGaN HEMTを安定して動作させることができる。したがって、線形性を維持しながら、飽和出力１Ｗ以上かつ電力付加効率５０％以上を実現できる。   In the present invention, a gallium nitride high electron mobility transistor (GaN HEMT) is used as the microwave transistor. Since GaN HEMT can operate at a high drain voltage (50 V or more), there is an advantage that the output matching circuit can be configured with a relatively high impedance. Moreover, the saturation output of GaN HEMT is several W or more, and is excellent in linearity and power added efficiency. Furthermore, a high gain GaN HEMT can be stably operated by a gate bias circuit that matches the gate resistance in a cryogenic environment. Therefore, it is possible to realize a saturation output of 1 W or more and a power added efficiency of 50% or more while maintaining linearity.

また、GaAs HEMTを初段に用い、GaN HEMTを２段目に用いることで、２段構成の低温受信増幅器でも低い雑音指数、高い飽和出力、高い電力付加効率を実現できる。   Also, by using GaAs HEMT as the first stage and GaN HEMT as the second stage, a low noise figure, high saturation output, and high power added efficiency can be realized even with a two-stage low-temperature receiving amplifier.

また、１５０Ｋ以下に冷却することで、低温受信増幅器の入出力電力によらずその良好な利得と電力付加効率を得ることができる。   Further, by cooling to 150K or less, it is possible to obtain good gain and power added efficiency regardless of the input / output power of the low-temperature receiving amplifier.

さらに、窒化ガリウム高電子移動度トランジスタに光を照射することで、電流崩壊現象によるドレイン−ソース間電流の増減を改善し、また、青色発光ダイオードの順方向電流を制御することでドレイン−ソース間電流の安定を図ることができ、低温環境下でも安定した増幅特性を得ることができる。   Furthermore, by irradiating light to the gallium nitride high electron mobility transistor, the increase / decrease of the drain-source current due to the current collapse phenomenon is improved, and the forward current of the blue light emitting diode is controlled to control the drain-source current. The current can be stabilized, and a stable amplification characteristic can be obtained even in a low temperature environment.

［第１実施形態］
図１（ａ）に、本発明の第１実施形態の低温受信増幅器１００の構成を示す。増幅素子としてGaN HEMT１１０を用いる。そして、GaN HEMT１１０のゲートと低温受信増幅器１００の入力端子Ｔ１との間で、GaN HEMT１１０のゲートと低温受信増幅器１００の外部とのインピーダンス整合を行う入力整合回路１２０と、GaN HEMT１１０のゲートに直流電圧を印加するゲートバイアス回路１３０と、GaN HEMT１１０のドレインと低温受信増幅器１００の出力端子Ｔ２との間で、GaN HEMT１１０のドレインと低温受信増幅器１００の外部とのインピーダンス整合を行う出力整合回路１４０と、GaN HEMT１１０のドレインに直流電圧を印加するドレインバイアス回路１５０を備えている。 [First Embodiment]
FIG. 1A shows the configuration of the low-temperature receiving amplifier 100 according to the first embodiment of the present invention. GaN HEMT110 is used as an amplifying element. An input matching circuit 120 that performs impedance matching between the gate of the GaN HEMT 110 and the outside of the low-temperature receiving amplifier 100 between the gate of the GaN HEMT 110 and the input terminal T1 of the low-temperature receiving amplifier 100, and a DC voltage across the gate of the GaN HEMT 110 An output matching circuit 140 that performs impedance matching between the drain of the GaN HEMT 110 and the outside of the low-temperature receiving amplifier 100 between the drain of the GaN HEMT 110 and the output terminal T2 of the low-temperature receiving amplifier 100; A drain bias circuit 150 for applying a DC voltage to the drain of the GaN HEMT 110 is provided.

入力整合回路１２０と出力整合回路１４０の設計周波数は、例えば、２ＧＨｚである。入力整合回路１２０と出力整合回路１４０は、それぞれ先端開放スタブを持ち、これらのスタブ長が動作周波数に適応するように調整されている。   The design frequency of the input matching circuit 120 and the output matching circuit 140 is, for example, 2 GHz. Each of the input matching circuit 120 and the output matching circuit 140 has an open-ended stub, and these stub lengths are adjusted so as to adapt to the operating frequency.

図１（ｂ）に示すゲートバイアス回路１３０は、発振防止回路１３１と抵抗分圧回路１３２を備えている。抵抗分圧回路１３２は、直流電源１６０の電圧をGaN HEMT１１０のゲート電圧に分圧している。分圧比は、抵抗３と発振防止回路１３１を含めたゲート側抵抗による直列抵抗値と抵抗２とで構成される並列抵抗値と、抵抗１との比である。   The gate bias circuit 130 shown in FIG. 1B includes an oscillation prevention circuit 131 and a resistance voltage dividing circuit 132. The resistance voltage dividing circuit 132 divides the voltage of the DC power supply 160 to the gate voltage of the GaN HEMT 110. The voltage dividing ratio is a ratio between the resistance 1 and the parallel resistance value constituted by the series resistance value of the gate-side resistance including the resistance 3 and the oscillation prevention circuit 131 and the resistance 2 and the resistance 1.

ドレインバイアス回路１５０は、発振防止回路１５１と給電回路１５２を備えている。給電回路１５２は、GaN HEMT１１０のドレインに、直流電源１７０から供給される直流電圧を印加する。   The drain bias circuit 150 includes an oscillation prevention circuit 151 and a power feeding circuit 152. The power feeding circuit 152 applies a DC voltage supplied from the DC power supply 170 to the drain of the GaN HEMT 110.

入力整合回路１２０側から見たGaN HEMT１１０のゲート抵抗は、常温時の１００オーム程度から、例えば６０Ｋ程度の極低温時には１０オーム程度に減少する。また、GaN HEMT１１０の相互コンダクタンス（ｇｍ）は、極低温時には常温時よりも増加する。したがって、１００オームのゲート抵抗を前提として低温受信増幅器１００を設計したのでは、GaN HEMT１１０のドレイン電流を制御できない。第１実施形態の低温受信増幅器１００は、１０オームのゲート抵抗を前提として設計した。   The gate resistance of the GaN HEMT 110 viewed from the input matching circuit 120 side decreases from about 100 ohms at room temperature to about 10 ohms at an extremely low temperature of about 60K, for example. Further, the mutual conductance (gm) of the GaN HEMT 110 increases at a very low temperature than at a normal temperature. Therefore, the drain current of the GaN HEMT 110 cannot be controlled if the low temperature receiving amplifier 100 is designed on the assumption of a gate resistance of 100 ohms. The low-temperature receiving amplifier 100 of the first embodiment is designed on the assumption of a gate resistance of 10 ohms.

図２は、第１実施形態の低温受信増幅器１００を、極低温環境で動作させる装置の構成を示している。低温受信増幅器１００は、真空保持容器９１０内の冷却ステージ９２０上に設置される。真空保持容器９１０の内部では、常に真空ポンプによって吸引されることで、所定の真空度が維持されている。また、冷却装置９３０は、真空保持容器９１０の内部を極低温に維持している。冷却温度は、後述するように１５０Ｋ以下とするのが好適である。なお、以下に示す実験では、図２に示した装置を用いた。   FIG. 2 shows a configuration of an apparatus for operating the low-temperature receiving amplifier 100 of the first embodiment in a cryogenic environment. The low-temperature receiving amplifier 100 is installed on the cooling stage 920 in the vacuum holding container 910. A predetermined degree of vacuum is maintained inside the vacuum holding container 910 by being always sucked by a vacuum pump. Further, the cooling device 930 maintains the inside of the vacuum holding container 910 at a very low temperature. The cooling temperature is preferably 150 K or less as will be described later. In the experiment shown below, the apparatus shown in FIG. 2 was used.

図３に、３００Ｋと６０Ｋでの低温受信増幅器１００の静特性を示す。この実験では、ゲート電圧を一定として、ドレイン電圧（Ｖｄ）を５０Ｖまで印加し、ドレイン電流（Ｉｄ）を測定した。図３から明らかなように、６０Ｋでの静特性は、ドレイン電圧の増加に応じてドレイン電流が増大している。これに対して３００Ｋでの静特性では、ドレイン電圧が増加してもドレイン電流は増加しておらず、典型的なトランジスタの静特性を示している。図３に示す実験結果から冷却によって、GaN HEMT１１０の相互コンダクタンス（ｇｍ）が増大していることが分かる。   FIG. 3 shows the static characteristics of the low-temperature receiving amplifier 100 at 300K and 60K. In this experiment, the drain voltage (Id) was measured by applying the drain voltage (Vd) up to 50 V with the gate voltage kept constant. As is clear from FIG. 3, in the static characteristics at 60K, the drain current increases as the drain voltage increases. On the other hand, in the static characteristics at 300 K, the drain current does not increase even when the drain voltage increases, indicating a typical static characteristic of a transistor. From the experimental results shown in FIG. 3, it can be seen that the mutual conductance (gm) of the GaN HEMT 110 is increased by cooling.

図４に、１つの搬送波の場合の低温受信増幅器１００の入出力特性を示す。測定周波数は２ＧＨｚである。GaN HEMT１１０のドレイン電圧（Ｖｄ）とドレイン電流（Ｉｄ）は、それぞれ５０Ｖと５０ｍＡとした。これは、３００ＫでのＡＢ級バイアス点である。３００Ｋと６０Ｋの場合では、冷却することで低温受信増幅器１００の利得は最大３ｄＢ向上している。飽和出力は、３００Ｋの場合でも６０Ｋの場合でも３５ｄＢｍである。冷却によって利得が拡大するのは、図３に示したように、相互コンダクタンス（ｇｍ）が冷却によって増加するためである。   FIG. 4 shows the input / output characteristics of the low-temperature receiving amplifier 100 in the case of one carrier wave. The measurement frequency is 2 GHz. The drain voltage (Vd) and drain current (Id) of the GaN HEMT 110 were 50 V and 50 mA, respectively. This is the class AB bias point at 300K. In the case of 300K and 60K, the gain of the low-temperature receiving amplifier 100 is improved by 3 dB at maximum by cooling. The saturation output is 35 dBm for both 300K and 60K. The reason why the gain is increased by cooling is that the mutual conductance (gm) is increased by cooling, as shown in FIG.

図５に、１つの搬送波の場合の低温受信増幅器１００の電力付加効率特性を示す。測定周波数は２ＧＨｚである。冷却によって、最大電力付加効率が５％向上した。また、最大電力付加効率は６２％であり、従来のFETを冷却した多段型増幅器の電力付加効率（１５％程度）の４倍以上の飛躍的に高い最大電力付加効率を達成している。冷却することでデバイス内の損失を低減でき、電力付加効率が改善したと考えられる。GaN HEMTは高耐圧トランジスタであり、高い電力付加効率が得られるトランジスタであるが、冷却しても常温と同様に高い電力付加効率が得られることが確認された。   FIG. 5 shows power added efficiency characteristics of the low-temperature receiving amplifier 100 in the case of one carrier wave. The measurement frequency is 2 GHz. Cooling improved the maximum power added efficiency by 5%. In addition, the maximum power added efficiency is 62%, and the maximum power added efficiency that is four times or more the power added efficiency (about 15%) of the conventional multi-stage amplifier cooled by the FET is achieved. It is thought that the loss in the device can be reduced by cooling and the power added efficiency is improved. GaN HEMT is a high withstand voltage transistor and is a transistor that can obtain high power added efficiency, but it has been confirmed that even when cooled, high power added efficiency can be obtained as at room temperature.

図６に、低温受信増幅器１００の相互変調歪特性を示す。測定では、中心周波数２ＧＨｚ、周波数間隔１００ｋＨｚの等振幅の２つの搬送波を用いた。６０Ｋでの出力インターセプトポイントは３６ｄＢｍである。冷却することで、３００Ｋでの出力インターセプトポイントを２ｄＢ改善している。冷却による出力インターセプトポイントの向上は、利得の拡大と３次相互変調歪成分の低減によると考えられる。   FIG. 6 shows the intermodulation distortion characteristics of the low-temperature receiving amplifier 100. In the measurement, two carrier waves having a center frequency of 2 GHz and an equal amplitude with a frequency interval of 100 kHz were used. The output intercept point at 60K is 36 dBm. By cooling, the output intercept point at 300K is improved by 2 dB. The improvement of the output intercept point by cooling is considered to be due to the increase in gain and the reduction of the third-order intermodulation distortion component.

図７に、低温受信増幅器１００の１波あたりの３次相互変調歪成分対主波の比（ＩＭ３/Ｓ）と１波あたりの５次相変調歪成分対主波の比（ＩＭ５/Ｓ）を示す。冷却することでＩＭ３/Ｓは最大５ｄＢ、ＩＭ５/Ｓは最大２０ｄＢ向上している。特に、ＩＭ５/Ｓでの冷却による向上効果は顕著である。相互変調歪特性が改善する理由には、冷却による相互コンダクタンス（ｇｍ）の増大とデバイス内部の低損失化が考えられる。   FIG. 7 shows the ratio of the third-order intermodulation distortion component per main wave (IM3 / S) and the ratio of the fifth-order modulation distortion component per main wave to the main wave (IM5 / S). Indicates. By cooling, IM3 / S is improved by a maximum of 5 dB and IM5 / S is improved by a maximum of 20 dB. In particular, the improvement effect by cooling with IM5 / S is remarkable. The reason why the intermodulation distortion characteristic is improved is considered to be an increase in mutual conductance (gm) due to cooling and a reduction in loss inside the device.

図８に、低温受信増幅器１００の雑音指数特性を示す。この実験では、低温受信増幅器１００の入力と出力の両方に１ｄＢの損失を持つケーブルを接続し、ケーブルごと真空保持容器９１０内部に格納し、雑音指数測定器によって雑音指数特性を測定した。図８から分かるように、２ＧＨｚでは、３００Ｋの場合と６０Ｋの場合とで雑音指数は、ほぼ同じである。この実験に用いた低温受信増幅器１００は、入力整合回路と出力整合回路が２ＧＨｚで設計されている。しかし、必ずしも雑音指数を最小化する設計でないことから、冷却による雑音指数の改善効果は見られなかった。また、利得は６０Ｋに冷却することで３００Ｋの場合よりも５ｄＢから６ｄＢ程度改善している。入力整合回路１２０と出力整合回路１４０の設計周波数が２ＧＨｚであることから、利得の最大値は２ＧＨｚで得られる。また、２．２ＧＨｚ以上で利得が０ｄＢ以下になるのは、入力整合回路１２０と出力整合回路１４０の設計による。   FIG. 8 shows the noise figure characteristic of the low-temperature receiving amplifier 100. In this experiment, a cable having a loss of 1 dB was connected to both the input and output of the low-temperature receiving amplifier 100, the cable was stored in the vacuum holding container 910, and the noise figure characteristic was measured by a noise figure measuring device. As can be seen from FIG. 8, at 2 GHz, the noise figure is almost the same between 300K and 60K. The low-temperature receiving amplifier 100 used in this experiment has an input matching circuit and an output matching circuit designed at 2 GHz. However, since it is not necessarily a design that minimizes the noise figure, the improvement effect of the noise figure by cooling was not seen. Further, the gain is improved by about 5 dB to 6 dB over the case of 300K by cooling to 60K. Since the design frequency of the input matching circuit 120 and the output matching circuit 140 is 2 GHz, the maximum value of the gain can be obtained at 2 GHz. Further, the reason why the gain becomes 0 dB or less at 2.2 GHz or more is due to the design of the input matching circuit 120 and the output matching circuit 140.

第１実施形態の低温受信増幅器１００は、上述のように、高い相互コンダクタンス（ｇｍ）によって、利得が最大３ｄＢ、最大電力付加効率が５％、出力インターセプトポイントが２ｄＢ、ＩＭ３/Ｓが最大５ｄＢ、ＩＭ５/Ｓが最大２０ｄＢ向上した。特に、最大電力付加効率は６２％であり、従来のFETを冷却した多段型増幅器の電力付加効率（１５％程度）の４倍以上の飛躍的に高い最大電力付加効率を達成した。GaN HEMTの飽和出力は数Ｗ以上なので、第１実施形態の低温受信増幅器１００によれば、線形性を維持しながら、飽和出力１Ｗ以上かつ電力付加効率５０％以上を実現できる。   As described above, the low-temperature receiving amplifier 100 of the first embodiment has a maximum transconductance (gm) of up to 3 dB, a maximum power added efficiency of 5%, an output intercept point of 2 dB, and IM3 / S of up to 5 dB. IM5 / S improved by up to 20 dB. In particular, the maximum power added efficiency was 62%, and the maximum power added efficiency that was dramatically higher than four times the power added efficiency (about 15%) of the conventional multistage amplifier that cooled the FET was achieved. Since the saturation output of GaN HEMT is several W or more, according to the low-temperature receiving amplifier 100 of the first embodiment, a saturation output of 1 W or more and a power added efficiency of 50% or more can be realized while maintaining linearity.

［低温受信増幅器の温度依存特性］
次に、GaN HEMT１１０の低温環境での動作について温度依存特性を明らかにするために、図２に示す冷却装置９３０の温度設定値を変更することで、低温受信増幅器１００の入出力特性を測定した。この測定では、搬送波を２ＧＨｚの１波とし、低温受信増幅器１００の入力電力を０ｄＢｍ，５ｄＢｍ，１０ｄＢｍとした。また、GaN HEMT１１０のドレインバイアス電圧を５０Ｖ、ドレイン電流を５０ｍＡとするゲートバイアス電圧を設定した。図１０に低温受信増幅器１００の利得の温度依存特性を示す。３００Ｋから１５０Ｋまでは一次の傾き（ほぼ１．５ｄＢ／１００Ｋの割合である。）で利得が増加している。１５０Ｋから５０Ｋまでは冷却による利得向上効果がほとんどみられない。このことから、冷却による相互コンダクタンス（ｇｍ）の増大は１５０Ｋまでである。 [Temperature dependence characteristics of low-temperature receiving amplifier]
Next, in order to clarify the temperature dependence characteristics of the operation of the GaN HEMT 110 in the low temperature environment, the input / output characteristics of the low temperature receiving amplifier 100 were measured by changing the temperature setting value of the cooling device 930 shown in FIG. . In this measurement, the carrier wave was one wave of 2 GHz, and the input power of the low-temperature receiving amplifier 100 was 0 dBm, 5 dBm, and 10 dBm. The gate bias voltage was set such that the drain bias voltage of the GaN HEMT 110 was 50 V and the drain current was 50 mA. FIG. 10 shows the temperature dependence characteristics of the gain of the low-temperature receiving amplifier 100. From 300K to 150K, the gain increases with a first-order slope (roughly 1.5 dB / 100K). From 150K to 50K, there is almost no gain improvement effect due to cooling. Therefore, the increase in mutual conductance (gm) due to cooling is up to 150K.

図１１に低温受信増幅器１００の電力付加効率の温度依存特性を示す。３００Ｋから１５０Ｋまでは、低温受信増幅器１００の電力付加効率は冷却に伴い向上している。例えば、入力電力１０ｄＢｍのとき、３００Ｋでの電力付加効率は４０％であるが、１５０Ｋでの電力付加効率は５２％であり、冷却によって１２％向上している。１５０Ｋから５０Ｋまでは冷却による電力付加効率の向上効果があまりみられない。例えば、GaN HEMT１１０の冷却温度が１５０Ｋでの電力付加効率は、冷却温度５０Ｋでの電力付加効率とほぼ同一である。また、図１１に示すように、入力電力が低下すると電力付加効率の向上の程度は低下するものの、冷却による電力付加効率の向上効果を認めることができる。   FIG. 11 shows the temperature dependence characteristics of the power added efficiency of the low-temperature receiving amplifier 100. From 300K to 150K, the power added efficiency of the low-temperature receiving amplifier 100 is improved with cooling. For example, when the input power is 10 dBm, the power added efficiency at 300K is 40%, but the power added efficiency at 150K is 52%, which is improved by 12% by cooling. From 150K to 50K, the effect of improving the power added efficiency by cooling is not so much seen. For example, the power addition efficiency when the cooling temperature of the GaN HEMT 110 is 150K is substantially the same as the power addition efficiency when the cooling temperature is 50K. Further, as shown in FIG. 11, when the input power is reduced, the degree of improvement in the power added efficiency is reduced, but the effect of improving the power added efficiency by cooling can be recognized.

図１２に低温受信増幅器１００の飽和出力電力の温度依存特性を示す。測定結果から、飽和出力電力は３４．０ｄＢｍから３４．３ｄＢｍの範囲であり、冷却によっても飽和出力電力は増大していない。これは、飽和出力電力はGaN HEMT１１０の温度に依存しない構造のパラメータ（フィンガー長等）によるためである。   FIG. 12 shows the temperature dependence characteristics of the saturation output power of the low-temperature receiving amplifier 100. From the measurement results, the saturated output power is in the range of 34.0 dBm to 34.3 dBm, and the saturated output power is not increased by cooling. This is because the saturation output power depends on the structure parameters (finger length, etc.) independent of the temperature of the GaN HEMT 110.

図１３に低温受信増幅器１００の雑音指数の温度依存特性を示す。これは図８に示す測定結果に関連する測定結果であるが、冷却による雑音指数の向上効果は見られなかった。一般には低雑音HEMTまたはFETでは冷却することで利得と雑音指数が向上することが知られているが、今回の実験にて雑音指数が向上しない理由としては、雑音指数を最適化する整合回路設計を行っていないことと、飽和出力電力４Ｗ級の高出力GaN HEMT１１０を用いたことによる熱雑音が一因であると考えられる。   FIG. 13 shows the temperature dependence characteristics of the noise figure of the low-temperature receiving amplifier 100. Although this is a measurement result related to the measurement result shown in FIG. 8, the effect of improving the noise figure by cooling was not seen. Generally, low noise HEMT or FET is known to improve gain and noise figure by cooling, but the reason why the noise figure does not improve in this experiment is the matching circuit design that optimizes the noise figure This is considered to be due to the fact that the thermal noise is not performed and the high-power GaN HEMT 110 having a saturation output power of 4 W class is used.

図１０〜図１３の各図に示す実験結果から、冷却による低温受信増幅器１００の諸特性（利得と電力付加効率）の向上に十分な温度範囲は入出力電力によらず１５０Ｋ以下であると認められる。１５０Ｋより低く冷却しても利得と電力付加効率に対する顕著な向上効果はみられない。換言すれば、GaN HEMT１１０を１５０Ｋ以下に冷却した環境下で増幅素子として用いることで、低温受信増幅器１００の入出力電力によらずその良好な利得と電力付加効率を得ることができる。   From the experimental results shown in FIGS. 10 to 13, it is recognized that a temperature range sufficient for improving various characteristics (gain and power added efficiency) of the low-temperature receiving amplifier 100 by cooling is 150 K or less regardless of input / output power. It is done. Even when cooling below 150K, no significant improvement in gain and power added efficiency is seen. In other words, by using the GaN HEMT 110 as an amplifying element in an environment cooled to 150K or less, it is possible to obtain good gain and power added efficiency regardless of the input / output power of the low-temperature receiving amplifier 100.

一般に知られている高温超伝導材料の臨界温度がおよそ７７Ｋであることを勘案すれば、超伝導効果を発揮する高温超伝導材料の冷却温度（およそ７７Ｋ以下）を達成する冷却装置を改造することなく使用することで、GaN HEMT１１０を用いた低温受信増幅器１００の冷却温度１５０Ｋ以下を実現できる。すなわち、例えば同一の冷却ステージ９２０（図２参照）に低温受信増幅器１００を搭載することで、低温受信増幅器１００を高温超伝導材料を用いたマイクロ波回路（例えば図１４に示す超伝導フィルタ９５０）と一緒に冷却することができる。   Taking into account that the critical temperature of a generally known high-temperature superconducting material is approximately 77K, remodeling the cooling device that achieves the cooling temperature of the high-temperature superconducting material that exhibits the superconducting effect (approximately 77K or less) By using the GaN HEMT 110, the cooling temperature of the low-temperature receiving amplifier 100 using the GaN HEMT 110 can be reduced to 150K or less. That is, for example, by mounting the low temperature receiving amplifier 100 on the same cooling stage 920 (see FIG. 2), the low temperature receiving amplifier 100 is a microwave circuit using a high temperature superconducting material (for example, the superconducting filter 950 shown in FIG. 14). Can be cooled together.

もちろん、低温受信増幅器１００および高温超伝導材料を用いた超伝導フィルタ９５０で構成される受信フロントエンドでは、真空保持容器９１０内の冷却ステージ９２０を超伝導フィルタ９５０と低温受信増幅器１００とで別個のものとしてもよい。これは、高温超伝導材料の臨界温度（およそ７７Ｋ）と低温受信増幅器１００の上限冷却温度１５０Ｋの温度差に着目した真空保持容器９１０の構成である。同一の真空保持容器９１０内に超伝導フィルタ９５０と低温受信増幅器１００を設置する場合、一例として、図１４に示すように、冷却能力の高い冷却ステージ９２２に超伝導フィルタ９５０を設置し、冷却能力の低い冷却ステージ９２１に低温受信増幅器１００を設置する。この構成は、冷却装置９３０の冷却能力に限界がある場合などに有効である。また、真空保持容器９１０全体を高温超伝導材料の臨界温度以下に冷却する必要がないことから、冷却装置９３０の冷却能力を削減し、真空保持容器９１０全体の小型化が可能である。   Of course, in the reception front end composed of the low-temperature receiving amplifier 100 and the superconducting filter 950 using the high-temperature superconducting material, the cooling stage 920 in the vacuum holding container 910 is separated by the superconducting filter 950 and the low-temperature receiving amplifier 100. It may be a thing. This is the configuration of the vacuum holding container 910 focusing on the temperature difference between the critical temperature of the high temperature superconducting material (approximately 77 K) and the upper limit cooling temperature 150 K of the low temperature receiving amplifier 100. When the superconducting filter 950 and the low-temperature receiving amplifier 100 are installed in the same vacuum holding container 910, as an example, as shown in FIG. 14, the superconducting filter 950 is installed in a cooling stage 922 having a high cooling capacity, and the cooling capacity The low-temperature receiving amplifier 100 is installed on the cooling stage 921 having a low temperature. This configuration is effective when the cooling capacity of the cooling device 930 is limited. Further, since it is not necessary to cool the entire vacuum holding container 910 below the critical temperature of the high-temperature superconducting material, the cooling capacity of the cooling device 930 can be reduced, and the entire vacuum holding container 910 can be reduced in size.

［第２実施形態］
図９に、本発明の低温受信増幅器１００を２段目に用いた２段受信増幅器の構成を示す。初段には雑音指数の低いGaAs HEMT２１０を用いた低温受信増幅器２００を用いる。上記非特許文献５に示されているように、初段のGaAs HEMT２１０は、例えば雑音指数０．３ｄＢ、利得１０ｄＢという特性を有している。例えば、２段目のGaN HEMT１１０の特性を、雑音指数２ｄＢ、利得２６ｄＢに設計すると、図９の構成での雑音指数は、およそ０．５３ｄＢとなる。上記非特許文献５の３段極低温受信機と比較して、段数を軽減しつつ、雑音指数０．５３ｄＢで飽和出力を１Ｗ以上かつ電力付加効率６２％を達成できる。 [Second Embodiment]
FIG. 9 shows a configuration of a two-stage receiving amplifier using the low-temperature receiving amplifier 100 of the present invention as the second stage. In the first stage, a low-temperature receiving amplifier 200 using a GaAs HEMT 210 having a low noise figure is used. As shown in Non-Patent Document 5, the first-stage GaAs HEMT 210 has characteristics such as a noise figure of 0.3 dB and a gain of 10 dB, for example. For example, when the characteristics of the second-stage GaN HEMT 110 are designed to have a noise figure of 2 dB and a gain of 26 dB, the noise figure in the configuration of FIG. 9 is approximately 0.53 dB. Compared with the three-stage cryogenic receiver disclosed in Non-Patent Document 5, the saturation power is 1 W or more and the power added efficiency is 62% with a noise figure of 0.53 dB while reducing the number of stages.

なお、第２実施形態の構成であっても、低温受信増幅器１００について、GaN HEMT１１０を１５０Ｋ以下に冷却した環境下で増幅素子として用いることができる。   Even in the configuration of the second embodiment, the low-temperature receiving amplifier 100 can be used as an amplifying element in an environment where the GaN HEMT 110 is cooled to 150K or less.

つまり、GaAs FETを２段目と３段目に用いる従来の方法よりも、GaN HEMTを２段目として用いる方法によって、電力付加効率を飛躍的に改善できる。   In other words, the power added efficiency can be drastically improved by the method using the GaN HEMT as the second stage rather than the conventional method using the GaAs FET at the second and third stages.

［第３実施形態］
第３実施形態は、低温環境下で生じる電流崩壊現象によるGaN HEMT１１０のドレイン−ソース間電流の減少を改善する。低温環境における電流崩壊現象では、電子励起状態が凍結した状態から時間とともに電子励起数が増加する。このため、ゲートバイアス電圧を設定してもドレイン電流が緩慢に増減する現象が生じる。 [Third Embodiment]
The third embodiment improves the decrease in the drain-source current of the GaN HEMT 110 due to the current collapse phenomenon that occurs in a low temperature environment. In the current decay phenomenon in a low temperature environment, the number of electronic excitations increases with time from the state in which the electronic excitation state is frozen. For this reason, even if the gate bias voltage is set, the drain current slowly increases or decreases.

ところで、一般に半導体上に光を照射することで、その特性が変化することが知られている。これは、半導体内に光エネルギーが注入されることで電子励起が活発になるためである。注入される光エネルギーは半導体のバンドギャップと注入する光の波長と関係している。これまでGaN HEMT１１０に対して有効な光の波長は明らかにされていなかった。   By the way, it is generally known that the characteristics change by irradiating light onto a semiconductor. This is because electronic excitation becomes active when light energy is injected into the semiconductor. The injected optical energy is related to the band gap of the semiconductor and the wavelength of the injected light. So far, the effective wavelength of light for the GaN HEMT 110 has not been clarified.

第３実施形態では、GaN HEMT１１０に対して有効な光の波長を明らかにする。図１５にGaN HEMTに青色ＬＥＤ（light emitting diode）５００による光を照射する実施例を示す。青色ＬＥＤ５００は、GaN HEMT１１０の上部に設置される。例えば、低温受信増幅器１００のケース上部に設置される。青色ＬＥＤ５００はGaN HEMT１１０とともに低温冷却される。   In the third embodiment, the wavelength of light effective for the GaN HEMT 110 is clarified. FIG. 15 shows an embodiment in which GaN HEMT is irradiated with light from a blue LED (light emitting diode) 500. Blue LED 500 is installed on top of GaN HEMT 110. For example, it is installed on the upper part of the case of the low-temperature receiving amplifier 100. The blue LED 500 is cooled at a low temperature together with the GaN HEMT 110.

ＬＥＤの発光波長は材料のバンドギャップに依存している。青色ＬＥＤ５００は一般にGaNを用いておりまたGaN HEMT１１０もGaNを用いることからそれぞれのバンドギャップは大差ないと考えられる。このため、青色ＬＥＤ５００の発光波長はGaN HEMT１１０の電子励起を生じさせるに十分であると考えられる。この点を明らかにするために、図２に示す低温受信増幅器１００を用いて冷却温度６０Ｋにて実験を行った。   The emission wavelength of the LED depends on the band gap of the material. Since the blue LED 500 generally uses GaN, and the GaN HEMT 110 also uses GaN, it is considered that the respective band gaps are not significantly different. For this reason, it is considered that the emission wavelength of the blue LED 500 is sufficient to cause electronic excitation of the GaN HEMT 110. In order to clarify this point, an experiment was conducted at a cooling temperature of 60 K using the low-temperature receiving amplifier 100 shown in FIG.

図１６に３００ＫにおけるＬＥＤ発光色相違によるドレイン−ソース間電流特性を示す。使用したＬＥＤは赤、黄、緑、青色であり、暗箱内にＬＥＤを設置し、GaN HEMT１１０にＬＥＤによる光を照射した。図中、暗状態は低温受信増幅器１００のケースに覆いをして遮光した状態でありＬＥＤを点灯していない。明状態はGaN HEMT１１０に室内灯を照射した状態である。暗状態あるいは赤、黄、緑のいずれかのＬＥＤを点灯した場合に比べて、青色ＬＥＤ５００または室内灯を点灯した場合の方がドレイン−ソース間電流特性は良好であった。なお、室内灯を点灯した場合に青色ＬＥＤ５００を点灯させた場合とほぼ同様のドレイン−ソース間電流特性を示した理由として、室内灯の光（可視光線）が青色ＬＥＤ５００の発する光とほぼ同じ波長が含むからであると考えられる。以下の実験では発光手段として青色ＬＥＤ５００を用いているが、GaNのバンドギャップに相当する波長の光、可視スペクトルの青色領域[波長にしておよそ４３０ｎｍから４９０ｎｍ程度]の光、あるいはこの光を含む光を発することのできる発光手段であれば特に限定はない。   FIG. 16 shows drain-source current characteristics according to LED emission color differences at 300K. The LEDs used were red, yellow, green, and blue. The LEDs were installed in a dark box, and the GaN HEMT 110 was irradiated with light from the LEDs. In the figure, the dark state is a state in which the case of the low-temperature receiving amplifier 100 is covered and shielded from light, and the LED is not lit. The bright state is a state in which the GaN HEMT 110 is irradiated with a room light. The drain-source current characteristics were better when the blue LED 500 or the room light was lit than when the dark LED or any one of the red, yellow, and green LEDs was lit. Note that the reason why the drain-source current characteristics were almost the same as when the blue LED 500 was turned on when the room light was turned on is that the light of the room light (visible light) has substantially the same wavelength as the light emitted by the blue LED 500. Is considered to be included. In the following experiments, a blue LED 500 is used as a light emitting means. However, light having a wavelength corresponding to the band gap of GaN, light in the blue region of the visible spectrum [about 430 nm to 490 nm in wavelength], or light including this light. The light emitting means is not particularly limited as long as it can emit light.

GaN HEMT１１０への光の照射は、低温受信増幅器１００に備えられた発光手段によってなされるとするが、この構成に限定されない。例えば、低温受信増幅器１００の外部に発光手段を設けて、この発光手段から発せられた光を低温受信増幅器１００に設けた光透過性を有する窓から導くことで、GaN HEMT１１０への光の照射を行う。この構成では、窓を通して導入された光、換言すればGaN HEMT１１０に直接当たる光が、GaNのバンドギャップに相当する波長の光、可視スペクトルの青色領域[波長にしておよそ４３０ｎｍから４９０ｎｍ程度]の光、あるいはこの光を含む光であればよい。   The light irradiation to the GaN HEMT 110 is performed by the light emitting means provided in the low-temperature receiving amplifier 100, but is not limited to this configuration. For example, by providing a light emitting means outside the low temperature receiving amplifier 100 and guiding light emitted from the light emitting means from a light-transmitting window provided in the low temperature receiving amplifier 100, light irradiation to the GaN HEMT 110 is performed. Do. In this configuration, light introduced through the window, in other words, light directly hitting the GaN HEMT 110, light having a wavelength corresponding to the band gap of GaN, light in the blue region of the visible spectrum [about 430 nm to 490 nm in wavelength] Or any other light that contains this light.

図１７に６０Ｋでのドレイン−ソース間電流特性を示す。実験では青色ＬＥＤ５００の光照射をＯＮ／ＯＦＦにした。ドレイン−ソース間電圧が４０Ｖ以下で顕著であった電流崩壊現象が青色ＬＥＤ５００の光を照射したことによって改善されている。   FIG. 17 shows drain-source current characteristics at 60K. In the experiment, the light irradiation of the blue LED 500 was turned ON / OFF. The current collapse phenomenon, which is remarkable when the drain-source voltage is 40 V or less, is improved by irradiating the blue LED 500 with light.

図１８に相互コンダクタンス（ｇｍ）特性を示す。ドレイン−ソース間電圧が２０Ｖ以下で青色ＬＥＤ５００の光を照射したことによって相互コンダクタンス（ｇｍ）が改善している。   FIG. 18 shows the mutual conductance (gm) characteristics. The transconductance (gm) is improved by irradiating the blue LED 500 with a drain-source voltage of 20 V or less.

図１９に冷却温度６０Ｋおよび測定周波数２ＧＨｚでの入出力特性を示す。低温受信増幅器１００の構成は第１実施形態と同じである。青色ＬＥＤ５００の光を照射することで利得が０．５ｄＢ向上している。また、出力電力も０．５ｄＢｍ向上している。   FIG. 19 shows input / output characteristics at a cooling temperature of 60 K and a measurement frequency of 2 GHz. The configuration of the low-temperature receiving amplifier 100 is the same as that of the first embodiment. By irradiating the light of the blue LED 500, the gain is improved by 0.5 dB. The output power is also improved by 0.5 dBm.

図２０に電力付加効率特性を示す。青色ＬＥＤ５００の光を照射することで、最大電力付加効率を８％改善し６６％を達成している。このように、低温環境下で青色ＬＥＤ５００の光をGaN HEMT１１０に照射することで、電力付加効率を改善できることがいえる。
この第３実施形態によって、低温受信増幅器１００の増幅動作が安定化するとともに、受信フロントエンドの動作も安定化する。 FIG. 20 shows power added efficiency characteristics. By irradiating the light of the blue LED 500, the maximum power added efficiency is improved by 8% to achieve 66%. Thus, it can be said that the power added efficiency can be improved by irradiating the light of the blue LED 500 to the GaN HEMT 110 in a low temperature environment.
According to the third embodiment, the amplification operation of the low-temperature reception amplifier 100 is stabilized, and the operation of the reception front end is also stabilized.

［温度依存性］
図２１に、GaN HEMT１１０に青色ＬＥＤ５００の光が照射された低温受信増幅器１００の利得に関する温度依存性を示す。測定条件は低温受信増幅器１００の入力電力を０ｄＢｍ，５ｄＢｍ，１０ｄＢｍとした。また、青色ＬＥＤ５００の順方向電流は１０ｍＡとした。冷却温度１２０Ｋでそれぞれの利得は最大となりまたは飽和した。１２０Ｋ以下での利得偏差は入力電力５ｄＢｍと１０ｄＢｍでそれぞれ０．６ｄＢと０．３ｄＢである。これに対して、３００Ｋから１２０Ｋでの利得増加量は入力電力５ｄＢｍと１０ｄＢｍでそれぞれ２ｄＢと２．３ｄＢである。利得の温度依存性から青色ＬＥＤ５００を用いた低温受信増幅器１００は１２０Ｋ以下に冷却することが望ましい。なお、第１実施形態にて青色ＬＥＤ５００を用いない低温受信増幅器１００の好ましい冷却温度は１５０Ｋ以下であった。この冷却温度の差異は冷却環境下でのGaN HEMT１１０の増幅特性による。 [Temperature dependence]
FIG. 21 shows temperature dependence regarding the gain of the low-temperature receiving amplifier 100 in which the light of the blue LED 500 is irradiated on the GaN HEMT 110. Measurement conditions were such that the input power of the low-temperature receiving amplifier 100 was 0 dBm, 5 dBm, and 10 dBm. The forward current of the blue LED 500 was 10 mA. At a cooling temperature of 120K, each gain is maximized or saturated. The gain deviation below 120K is 0.6 dB and 0.3 dB for input powers of 5 dBm and 10 dBm, respectively. On the other hand, gain increases from 300K to 120K are 2 dB and 2.3 dB, respectively, at input powers of 5 dBm and 10 dBm. It is desirable that the low temperature receiving amplifier 100 using the blue LED 500 is cooled to 120K or less because of the temperature dependence of the gain. In addition, the preferable cooling temperature of the low temperature receiving amplifier 100 which does not use blue LED500 in 1st Embodiment was 150K or less. This difference in cooling temperature depends on the amplification characteristics of the GaN HEMT 110 in a cooling environment.

図２２に電力付加効率（ＰＡＥ）に関する温度依存性を示す。冷却温度１２０Ｋにて飽和しまたは最大値が得られている。３００Ｋから１２０ＫでのＰＡＥ改善量は入力電力１０ｄＢｍにて１０％改善している。このことは第１実施形態の図１１に示す結果と同様である。   FIG. 22 shows the temperature dependence regarding the power added efficiency (PAE). Saturation or a maximum value is obtained at a cooling temperature of 120K. The PAE improvement from 300K to 120K is improved by 10% at an input power of 10 dBm. This is the same as the result shown in FIG. 11 of the first embodiment.

図２１と図２２から明らかなように、GaN HEMT１１０に青色ＬＥＤ５００の光が照射された低温受信増幅器１００は、１２０Ｋ以下に冷却すれば利得及び電力付加効率の改善の点において十分である。超伝導フィルタの臨界温度が一般に７７Ｋであることから、超伝導フィルタと低温受信増幅器の真空容器内設置位置（第２実施形態参照）を工夫することで、一様に７７Ｋ以下に冷却する場合に比較して冷却能力を軽減できる。   As is clear from FIGS. 21 and 22, the low-temperature receiving amplifier 100 in which the light of the blue LED 500 is irradiated on the GaN HEMT 110 is sufficient in terms of improvement of gain and power added efficiency if it is cooled to 120K or less. Since the critical temperature of a superconducting filter is generally 77K, when the superconducting filter and the cryogenic receiving amplifier are installed in a vacuum container (see the second embodiment), the temperature is uniformly reduced to 77K or less. In comparison, the cooling capacity can be reduced.

［第４実施形態］
図２３に、GaN HEMT１１０に青色ＬＥＤ５００の光を照射した場合の低温受信増幅器１００の電流値収束特性を示す。実験条件は、冷却温度６０Ｋ、測定周波数２ＧＨｚ、入力電力５．５ｄＢｍとした。比較のためにGaN HEMT１１０に青色ＬＥＤ５００の光を照射しない場合の測定結果も示す。青色ＬＥＤ５００の光を照射することで、照射時間１５００秒までの電流値偏移は６％である。電流値設定は５０ｍＡであることから、電流値偏移は３ｍＡである。これに対して光を照射しないと１５００秒にて電流値偏移は４２％、電流値偏移は２１．４ｍＡである。このように、青色ＬＥＤ５００の光を照射することで低温受信増幅器１００の電流値を安定化できる。これは、低温受信増幅器１００の動作点安定化であり、利得、効率、線形性の安定化になる。青色ＬＥＤ５００の光を照射しない場合には、電流値が安定するまで低温受信増幅器１００のアイドル運転が必要である。この場合、送信出力の変化によって電流値が不安定になる。また、電流値安定化のために、定電流回路が必要である。しかし、青色ＬＥＤ５００の光を照射することで電流値安定化を簡易かつ高速に行うことができる。 [Fourth Embodiment]
FIG. 23 shows the current value convergence characteristics of the low-temperature receiving amplifier 100 when the GaN HEMT 110 is irradiated with light from the blue LED 500. The experimental conditions were a cooling temperature of 60K, a measurement frequency of 2 GHz, and an input power of 5.5 dBm. For comparison, a measurement result when GaN HEMT 110 is not irradiated with light from blue LED 500 is also shown. By irradiating the light of the blue LED 500, the current value shift until the irradiation time of 1500 seconds is 6%. Since the current value setting is 50 mA, the current value deviation is 3 mA. On the other hand, if no light is irradiated, the current value deviation is 42% and the current value deviation is 21.4 mA in 1500 seconds. Thus, the current value of the low-temperature receiving amplifier 100 can be stabilized by irradiating the light of the blue LED 500. This is the stabilization of the operating point of the low-temperature receiving amplifier 100, and the gain, efficiency, and linearity are stabilized. When the light of the blue LED 500 is not irradiated, it is necessary to idle the low temperature receiving amplifier 100 until the current value is stabilized. In this case, the current value becomes unstable due to a change in the transmission output. In addition, a constant current circuit is necessary to stabilize the current value. However, the current value can be stabilized simply and at high speed by irradiating the light of the blue LED 500.

図２４に低温におけるドレイン−ソース間電流を一定に維持する青色ＬＥＤ回路の一例を示す。回路６００は、積分回路６１０と、比較器６２０と、青色ＬＥＤ順方向電流制御回路６３０で構成される。積分回路６１０はドレイン−ソース間電流をモニタし、比較的長い積分時間でモニタした電流値を積分する。比較的長い積分時間を用いる理由は、低温環境下でのドレイン−ソース間電流の変化が数分単位に亘る緩慢な変化による。積分回路６１０は時定数の長いＬＣフィルタ回路で構成できる。ＬＣフィルタは集中定数素子で構成できる。   FIG. 24 shows an example of a blue LED circuit that maintains a constant drain-source current at a low temperature. The circuit 600 includes an integration circuit 610, a comparator 620, and a blue LED forward current control circuit 630. The integration circuit 610 monitors the drain-source current and integrates the monitored current value with a relatively long integration time. The reason for using a relatively long integration time is due to the slow change of the drain-source current in a low temperature environment over several minutes. The integrating circuit 610 can be composed of an LC filter circuit having a long time constant. The LC filter can be composed of lumped constant elements.

比較器６２０は、積分回路６１０の出力とドレイン−ソース間電流基準値との差をとる。積分回路６１０の出力がドレイン−ソース間電流基準値に一致していれば、比較器６２０の出力は０となる。比較器６２０はオペアンプで構成してもよい。また差動回路で構成してもよい。   The comparator 620 takes the difference between the output of the integrating circuit 610 and the drain-source current reference value. If the output of the integration circuit 610 matches the drain-source current reference value, the output of the comparator 620 becomes zero. The comparator 620 may be composed of an operational amplifier. Moreover, you may comprise with a differential circuit.

青色ＬＥＤ順方向電流制御回路６３０は電流帰還型増幅回路で構成できる。また、青色ＬＥＤ順方方向電流制御回路６３０は定電流ダイオードで構成してもよい。比較器６２０の出力は電流帰還型増幅回路を構成するトランジスタ６８０のベースに入力される。電流帰還型増幅回路のベースバイアス電圧は二つの抵抗６４０、６５０にて分圧して与えられる。このベースバイアス電圧が順方向電流の基準値を決定する。比較器６２０は積分回路６１０の出力とドレイン−ソース間電流基準値との差を出力し、緩慢な時間変動成分でトランジスタ６８０のベースでのベースバイアス電圧を調整する。このとき順方向電流も変動し、GaN HEMT１１０へ照射する青色ＬＥＤ５００の光強度が変動する。これはGaN HEMT１１０のドレイン−ソース間電流がドレイン−ソース間電流基準値より少ないときは順方向電流を増やし、GaN HEMT１１０のドレイン−ソース間電流が多いときは順方向電流を減らす。この動作を積分回路６１０の時定数に依存して行うことで、GaN HEMT１１０のドレイン−ソース間電流の安定化を図ることができる。   The blue LED forward current control circuit 630 can be composed of a current feedback type amplifier circuit. Further, the blue LED forward current control circuit 630 may be formed of a constant current diode. The output of the comparator 620 is input to the base of a transistor 680 that forms a current feedback amplifier circuit. The base bias voltage of the current feedback amplifier circuit is given by being divided by two resistors 640 and 650. This base bias voltage determines the reference value of the forward current. The comparator 620 outputs the difference between the output of the integrating circuit 610 and the drain-source current reference value, and adjusts the base bias voltage at the base of the transistor 680 with a slow time variation component. At this time, the forward current also varies, and the light intensity of the blue LED 500 irradiated to the GaN HEMT 110 varies. This increases the forward current when the drain-source current of the GaN HEMT 110 is smaller than the drain-source current reference value, and decreases the forward current when the drain-source current of the GaN HEMT 110 is large. By performing this operation depending on the time constant of the integration circuit 610, the drain-source current of the GaN HEMT 110 can be stabilized.

本発明は、移動通信基地局受信系など無線通信基地局受信系に用いることができる。   The present invention can be used for a radio communication base station reception system such as a mobile communication base station reception system.

本発明の低温受信増幅器の構成を示す図。The figure which shows the structure of the low-temperature receiving amplifier of this invention. ゲートバイアス回路の一例を示す図。The figure which shows an example of a gate bias circuit. 本発明の低温受信増幅器を、極低温環境で動作させる装置の構成を示す図。The figure which shows the structure of the apparatus which operates the low temperature receiving amplifier of this invention in a cryogenic environment. 常温（３００Ｋ）と極低温（６０Ｋ）での低温受信増幅器１００の静特性を示す図。The figure which shows the static characteristic of the low temperature receiving amplifier 100 in normal temperature (300K) and extremely low temperature (60K). 低温受信増幅器１００の入出力特性を示す図。The figure which shows the input-output characteristic of the low temperature receiving amplifier 100. 低温受信増幅器１００の電力付加効率特性を示す図。The figure which shows the power added efficiency characteristic of the low temperature receiving amplifier. 低温受信増幅器１００の相互変調歪特性を示す図。The figure which shows the intermodulation distortion characteristic of the low temperature receiving amplifier 100. 低温受信増幅器１００の１波あたりの３次相互変調歪成分対主波の比（ＩＭ３/Ｓ）と１波あたりの５次相変調歪成分対主波の比（ＩＭ５/Ｓ）を示す図。The figure which shows the ratio (IM3 / S) of the 3rd-order intermodulation distortion component per main wave (IM3 / S) per wave of the low-temperature receiving amplifier 100, and the ratio (IM5 / S) of the 5th-order phase modulation distortion component per main wave. 低温受信増幅器１００の雑音指数特性を示す図。The figure which shows the noise figure characteristic of the low temperature receiving amplifier. 本発明の低温受信増幅器１００を２段目に用いた２段受信増幅器の構成を示す図。The figure which shows the structure of the two-stage receiving amplifier which used the low-temperature receiving amplifier 100 of this invention for the 2nd stage. 低温受信増幅器１００の利得に関する温度依存特性の測定結果を示す図。The figure which shows the measurement result of the temperature dependence characteristic regarding the gain of the low temperature receiving amplifier. 低温受信増幅器１００の電力付加効率に関する温度依存特性の測定結果を示す図。The figure which shows the measurement result of the temperature dependence characteristic regarding the power addition efficiency of the low temperature receiving amplifier. 低温受信増幅器１００の飽和出力電力に関する温度依存特性の測定結果を示す図。The figure which shows the measurement result of the temperature dependence characteristic regarding the saturation output electric power of the low temperature receiving amplifier. 低温受信増幅器１００の雑音指数に関する温度依存特性の測定結果を示す図。The figure which shows the measurement result of the temperature dependence characteristic regarding the noise figure of the low temperature receiving amplifier. 低温受信増幅器１００および超伝導フィルタ９５０を用いた受信フロントエンドの構成を示す図。The figure which shows the structure of the reception front end using the low temperature receiving amplifier 100 and the superconducting filter 950. GaN HEMTと青色ＬＥＤを用いた低温受信増幅器の実施例を示す図。The figure which shows the Example of the low-temperature receiving amplifier using GaN HEMT and blue LED. ＬＥＤの差異によるドレイン−ソース間電流の測定結果を示す図The figure which shows the measurement result of the drain-source current by the difference of LED 図１５に示す低温受信増幅器の静特性に関する測定結果を示す図。The figure which shows the measurement result regarding the static characteristic of the low temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器の相互コンダクタンス特性に関する測定結果を示す図。The figure which shows the measurement result regarding the transconductance characteristic of the low-temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器の入出力特性に関する測定結果を示す図。The figure which shows the measurement result regarding the input-output characteristic of the low-temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器の電力付加効率特性に関する測定結果を示す図。The figure which shows the measurement result regarding the power added efficiency characteristic of the low-temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器の利得の温度依存性に関する測定結果を示す図。The figure which shows the measurement result regarding the temperature dependence of the gain of the low-temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器の電力付加効率の温度依存性に関する測定結果を示す図。The figure which shows the measurement result regarding the temperature dependence of the power addition efficiency of the low-temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器の電流安定化に関する測定結果を示す図。The figure which shows the measurement result regarding the electric current stabilization of the low temperature receiving amplifier shown in FIG. 図１５に示す低温受信増幅器のドレイン−ソース間電流安定化回路の一例を示す図。The figure which shows an example of the drain-source current stabilization circuit of the low-temperature receiving amplifier shown in FIG.

Claims (1)

１５０Ｋ以下に冷却された環境で用いられる低温受信増幅器であって、
増幅素子としての窒化ガリウム高電子移動度トランジスタと、
窒化ガリウムのバンドギャップに相当する波長の光を照射する青色発光ダイオード、または、可視スペクトルの青色領域に相当する波長の光（青色光）を照射する青色発光ダイオード、または、前記青色光を含む光を照射する青色発光ダイオードと、
前記増幅素子のゲートと前記低温受信増幅器の入力端子の外部とのインピーダンス整合を行う入力整合回路と、
前記増幅素子のゲートに直流電圧を印加するゲートバイアス回路と、
前記増幅素子のドレインと前記低温受信増幅器の出力端子の外部とのインピーダンス整合を行う出力整合回路と、
前記増幅素子のドレインに直流電圧を印加するドレインバイアス回路と、
前記窒化ガリウム高電子移動度トランジスタのドレイン−ソース間の電流値をモニタする回路と、
前記モニタした前記電流値を積分する積分器と、
前記積分器の出力と基準電流値との差を出力する比較器と、
前記比較器の出力を０にするように前記青色発光ダイオードの順方向電流を制御する制御器と
を備えており、
前記順方向電流を制御された前記青色発光ダイオードから発せられた光を前記窒化ガリウム高電子移動度トランジスタに照射する
ことを特徴とする低温受信増幅器。 A low-temperature receiving amplifier used in an environment cooled to 150K or lower,
A gallium nitride high electron mobility transistor as an amplifying element ;
Blue light emitting diode for emitting light having a wavelength corresponding to the band gap of the nitride gallium, or blue light emitting diode for irradiating the wavelength corresponding to the blue region of the visible spectrum light (blue light), or including the blue light A blue light emitting diode that emits light;
An input matching circuit that performs impedance matching between the gate of the amplification element and the outside of the input terminal of the low-temperature receiving amplifier;
A gate bias circuit for applying a DC voltage to the gate of the amplifying element;
An output matching circuit for impedance matching between the drain of the amplifying element and the outside of the output terminal of the low-temperature receiving amplifier;
A drain bias circuit for applying a DC voltage to the drain of the amplifying element ;
A circuit for monitoring a drain-source current value of the gallium nitride high electron mobility transistor;
An integrator for integrating the monitored current value;
A comparator that outputs a difference between the output of the integrator and a reference current value;
A controller for controlling the forward current of the blue light emitting diode so that the output of the comparator is zero, and
The gallium nitride high electron mobility transistor is irradiated with light emitted from the blue light emitting diode controlled in the forward current.
Cryogenic receiving amplifier you wherein a.
JP2007309239A 2007-02-23 2007-11-29 Low temperature receiver amplifier Expired - Fee Related JP5191221B2 (en)

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