【正文】 3 shows the fractional power loss of the input and output windows, calculated from the measured plex Sparameter data asFL=1?Re(S11)2?Im(S11)2?Re(S21)2?Im(S21)2. (1)The baseline fractional loss of the input/output waveguide transitions is approximately 30%. Peaks in the fractional loss are characteristic of resonant “ghost” modes that exist inside the window and have transverse structure similar to a circular waveguide mode but are below the cutoff frequency of the corresponding mode in empty waveguide。 they are thus trapped in the vicinity of the window and evanesce into the waveguide on either side. Ghost mode resonances associated with perturbations such as offset or tilt misalignment of the window disk, nonuniformity of the window edge metallization/braze, or nonuniformity of the dielectric material can also be excited by waveguide propagating modes. Three ghost modes observed near 200–210 GHz and one near 230 GHz are TE41?, TE12?, TM11?, and TE51?like modes, respectively, and were intentionally moved outside our operating band in thedesign.An extended interaction klystron was used to test windows at W, 100% duty at 218 GHz for several minutes. No pulse distortion or reflection that would indicate breakdown was observed during the highpower testing.Fig. 3. Measured fractional power loss of (a) input window and (b) output window. The baseline 30%loss is due to the input/output waveguide transitions.Fig. 4. S11 measurements of output window during tuning procedure, between lapping operations.B. Window TuningThe window response was tuned by lapping the copper cylinder piece on each end face to adjust the circular waveguide length L, which was initially fabricated oversized to allow tuning. This was done prior to taking the final coldtest data shown in Fig. 2. Fig. 4 shows the S11 of the output window during the tuning procedure, measured between lapping operations. Each lapping removed ～10–30 μm of copper from one end of the cylinder, and lapping was alternated between the two ends to maintain symmetry. For this particular window, the tuning procedure widened the pass band by 15 GHz and improved reflection by 15 dB over the band in parison to the initially fabricated piece. The final L values for the two windows were in the range of 730–870 μm.III. CONCLUSIONThis brief has presented measurements of broadband pillbox vacuum windows that transmit mmW in the range of 210–235 GHz. Our coldtest data and simulations demonstrate systematic tuning of each window after fabrication to achieve broadband transmission close to an ideal design. We found it necessary to control the circular waveguide length to ≤ 10 μm tolerance. Another critical parameter was the variance in the as fabricated thickness of the BeO disks。 we observed a 10GHz shift in the window pass band for a 20μm difference in thickness, as predicted in simulation. While we did not measure the dielectric constant of the BeO to verify the specified value of ε = , we do not expect variation between the windows because they came from the same material stock. These results demonstrate a successful method for fabricating broadband windows for upper mmW vacuum electron devices.翻譯文稿. 翻譯文稿220GHz行波管放大器輸出窗設(shè)計(jì)電氣與電子工程師協(xié)會(huì)研究員Takuj Kimura,Edward L. Wright, Jeffrey P. Calame，副研究員Alan M. Cook，Colin D. Joye摘要本文介紹氧化鈹陶瓷材料220GHz行波管放大器錐型窗的電磁冷腔測(cè)試參數(shù)。通過(guò)傳輸和反射測(cè)試顯示在中心頻率處最少25GHz帶寬內(nèi)回波損耗優(yōu)于20dB。觀測(cè)到當(dāng)圓波導(dǎo)長(zhǎng)度改變窗的輸出波形也相應(yīng)改變。，在218GHz出現(xiàn)100%功率傳輸。索引詞大功率放大器，毫米波設(shè)備，毫米波測(cè)量微波電真空器件要想正常傳輸微波，需要輸出窗作為隔離高真空區(qū)域的電子束與管外大氣環(huán)境的分界面。阻抗匹配條件使得輸出窗只能傳輸一定頻段的電磁波，在頻段外電磁波的大部分能量將被反射。對(duì)與毫米波放大器如行波管，為了在整個(gè)工作頻段防止反饋振蕩，在輸出窗輸出口和輸入口保持足夠低的反射是很必要的。常規(guī)矩形波導(dǎo)輸出窗是半波諧振窗，通常是在一段導(dǎo)波中填充一些介質(zhì)材料。當(dāng)導(dǎo)波波長(zhǎng)等于兩倍窗片厚度時(shí)，這時(shí)此諧振匹配的輸出窗允許進(jìn)入的毫米波以低反射通過(guò)。這種結(jié)構(gòu)的響應(yīng)帶寬是窄帶的，因此不適應(yīng)要求傳輸帶寬 10%的寬頻放大器。一個(gè)良好的阻抗匹配寬帶設(shè)備可以通過(guò)設(shè)計(jì)一種特殊窗口即圓錐形陶瓷微波輸出窗來(lái)得到，這種輸出窗由從矩形波導(dǎo)到圓波導(dǎo)的一段過(guò)渡和半波諧振匹配窗片構(gòu)成。在工作頻段，選擇合適的圓波導(dǎo)長(zhǎng)度來(lái)消除進(jìn)出口錐形和窗片帶來(lái)的反射。有數(shù)據(jù)顯示具有半波諧振匹配輸出窗和錐形輸出窗的毫米波設(shè)備已經(jīng)被應(yīng)用到W頻段（75~110GHz）。隨著頻率的增加，達(dá)到寬帶阻抗匹配必要的所需制造誤差變得越來(lái)越困難。加膜窗片是替代錐形輸出窗的更高端潛在毫米波設(shè)備，但它的制備可能帶來(lái)其他制作工藝方面的挑戰(zhàn)。簡(jiǎn)單來(lái)說(shuō)，我們給出了在220GHz的寬帶錐形輸出窗的實(shí)驗(yàn)測(cè)試結(jié)果。必要的制造誤差是通過(guò)在冷測(cè)試中精確調(diào)整錐形窗結(jié)構(gòu)得到的。這種輸出窗是為行波管放大器在頻帶 范圍內(nèi)輸出功率超過(guò)50W而設(shè)計(jì)的。從而提出了這項(xiàng)延伸工作。 圖1顯示這種窗的裝置示意圖。輸入和輸出端口是標(biāo)準(zhǔn)WR4波導(dǎo)（ ）。錐形模型轉(zhuǎn)換裝置將矩形波導(dǎo)的TE10模轉(zhuǎn)換為圓波導(dǎo)的TE11模。這個(gè)輸出窗由一個(gè)邊緣金屬化的氧化鈹陶瓷窗片焊接在一段銅管上構(gòu)成。如圖1所示，這種輸出窗就是由這兩部分夾緊構(gòu)成。氧化鈹窗片的性能如表1所示。圖1 （a）錐形輸出窗的幾何模型。矩形波導(dǎo)TE10模到圓波導(dǎo)TE11模之間的錐形過(guò)渡帶。圓波導(dǎo)的長(zhǎng)度為L(zhǎng)。（b）用顯微鏡觀察到的50倍放大焊接窗片。（c）放在硬幣旁的窗片組件照片用矢量網(wǎng)絡(luò)分析儀測(cè)量輸出窗復(fù)雜的反射系數(shù)（S11）和透射系數(shù)（S21）。在140~325GHz頻段的測(cè)量是用兩個(gè)毫米波鏡片完成的，一個(gè)在WR5波段（140~220GHz）一個(gè)在WR3波段（220~325GHz）。兩種輸出窗都是在冷測(cè)裝置中將模式轉(zhuǎn)化器、輸入輸出端WR4矩形波導(dǎo)通過(guò)WR5/ WR3與WR4的錐形裝換連接到相應(yīng)測(cè)試端口。在整個(gè)帶寬中，波導(dǎo)和過(guò)渡段的整個(gè)插入損耗。陶瓷窗片本身的插入損耗被確定為＜，這個(gè)結(jié)果低于我們所設(shè)置的噪聲閥值。如圖2所示用輸出窗的S11和S21的波動(dòng)來(lái)選擇行波管的輸入輸出端口。通過(guò)包括三位電磁仿真結(jié)果（基于HFSS）的對(duì)比，在給定窗片厚度t的情況下通過(guò)調(diào)節(jié)圓波導(dǎo)的長(zhǎng)度L可以得到最優(yōu)的設(shè)計(jì)模型。用下面B部分所描述的優(yōu)化過(guò)程，輸出窗可以做到最優(yōu)化的諧振特性，在20GHz帶寬內(nèi)得到 20dB的反射效果。在輸入輸出端口窗片的厚度分別為t = 292 177。 5μm、 t = 275 177。 5μm。輸出端口的帶寬約為10GHz，比輸入端口稍微寬點(diǎn)。將此輸出窗作為輸出端是為了減小在放大器預(yù)設(shè)增益線高頻尾端的反饋震蕩。圖3表示從測(cè)量出的復(fù)雜的S參數(shù)通過(guò)計(jì)算得到輸入輸出窗口的部分功率損耗，公式如下:FL=1?Re(S11)2?Im(S11)2?Re(S21)2?Im(S21)2. (1)輸入輸出波導(dǎo)過(guò)渡帶的基本損耗大約為30%。部分損耗的峰值具有存在于輸出窗中諧振鬼模的特性，具有類(lèi)似于圓波導(dǎo)的橫向諧振結(jié)構(gòu)，但是其頻率低于對(duì)應(yīng)空波導(dǎo)的截止頻率；因此他們被束縛在輸出窗附近并消失在波導(dǎo)兩側(cè)。鬼模共振的出現(xiàn)與例如窗片的失調(diào)或傾斜錯(cuò)位等擾動(dòng)有關(guān)，窗片邊緣金屬和焊接的不均勻，或者不均勻的介質(zhì)材料都可能激起傳導(dǎo)模式的畸變。在200~210GHz附近像TE41?, TE12?, TM11?,這種模式的三個(gè)鬼模和在230GHz附近的像TE51?這種模式的一個(gè)鬼模，在這種設(shè)計(jì)中是我們分別特意將其移出工作頻段的。圖2 (a)輸入窗S21與S22（b）輸出窗S21與S22。（黑色十字線，黑色實(shí)線）HFSS的仿真結(jié)果表明基于測(cè)量窗片厚度而設(shè)計(jì)出的最優(yōu)輸出窗效果。圖3 （a）輸入窗口的功率損耗（b）輸出窗口的功率損耗。其中最起碼有30%的損耗是由于輸入/輸出波導(dǎo)過(guò)渡帶引起的。，218GHz，100%工作效率下測(cè)試輸出窗幾分鐘。如果沒(méi)有脈沖失真或反射，則表明高功率測(cè)試下故障將被觀察到。圖4 在優(yōu)化過(guò)程中測(cè)量出的輸出窗參數(shù)S21通過(guò)在兩個(gè)端面研磨銅管以調(diào)節(jié)圓波導(dǎo)長(zhǎng)度L來(lái)優(yōu)化窗的響應(yīng)，為允許優(yōu)化最初焊接較大尺寸的L。這樣做是為了將最后的冷腔測(cè)試數(shù)值表示在圖2中。圖4顯示了測(cè)量改變過(guò)程，輸出窗S11的優(yōu)化過(guò)程。每次將銅軸圓減小約10–30 μm厚，并且減小時(shí)保持兩端的對(duì)稱(chēng)。相比最初的模型，通過(guò)優(yōu)化這種輸出窗擴(kuò)展了15GHz的帶寬，并且在所在頻段內(nèi)將反射系數(shù)改善了15dB。最終確定兩個(gè)窗的L值都在730–870 。3．總結(jié)本文簡(jiǎn)要介紹了在210–235 ，錐形輸出窗的參數(shù)測(cè)定。經(jīng)過(guò)冷腔測(cè)試和模擬優(yōu)化后，每個(gè)窗口實(shí)現(xiàn)在要求頻段內(nèi)的傳輸接近理想設(shè)計(jì)。發(fā)現(xiàn)有必要將圓波導(dǎo)長(zhǎng)度誤差控制在≤ 10 μm。另一個(gè)關(guān)鍵的參量為氧化鈹窗片的厚度，通過(guò)仿真可以預(yù)測(cè)到窗片厚度每改變20μm，整個(gè)窗的帶寬就相應(yīng)改變10GHZ。，但是我們還是不希望同一規(guī)格的窗片介質(zhì)材料會(huì)有所不同。以上結(jié)果充分證明這是一種設(shè)計(jì)高頻毫米波電真空器件寬頻輸出窗的成功方法。翻譯文稿