西安电子科技大学研究生专业英语文献翻译大作业样例

A Simple Circular-to-Rectangular Waveguide Transition

Eric L. Holzman, Senior Member, IEEE

Abstract —We describe a novel one-step 11T E -mode circular waveguide to 10T E -mode rectangular waveguide transition. The primary advantage of this device over existing transitions is its ease of fabrication. We have incorporated our transition into a number of waveguide components operating at V-band. The transition’s measured return loss exceeds 15 dB over a 12% bandwidth c entered near 60 GHz.

Index Terms —Circular waveguides, rectangular waveguides, waveguide junctions, waveguide transitions, waveguides.

Ⅰ. INTRODUCTION

①TRANSITIONS between metal electromagnetic waveguides of different cross sections are probably nearly as old as waveguides themselves. ②In particular, horn and reflector antennas often use circular waveguide feeds but require more standard rectangular waveguide for connection to the rest of the microwave system. ③A variety of methods exist for transforming between a circular waveguide propagating the 11T E mode and a rectangular waveguide propagating the mode. A gradual

transition, in which the rectangular cross section is transformed continuously over the length of the transition into a circular cross section, provides very low insertion loss and high return loss over a broad bandwidth, but is relatively long. ④The bandwidth of a stepped transition, in which the rectangular waveguide is matched to the circular waveguide via one or more intermediate structures of constant cross section, increases with the number of steps [1]–[5]. We also can butt the rectangular and circular

waveguides directly together with an iris at the junction for matching [6]. ⑤All these structures require a significant amount of precision machining, especially in the millimeter-wave bands, where the waveguide dimensions are small.

We describe a simple, easy-to-implement, one-step transition for dominant mode circular to rectangular waveguide. ⑥The transition requires a single machining operation to fabricate. Our design appears to be novel.

Ⅱ. CONCEPT

⑦Fig. 1 shows a conventional one-step circular-to-rectangular waveguide transition, much like that described in [5]. Typically, the step is the output of the component with the circular waveguide. ⑧The circular waveguide has a diameter that is greater than the height of standard rectangular waveguide if we are to operate at least 10% above the 11T E mode cutoff frequency. ⑨Thus, to machine a one-step transition out of a block of metal, the circular waveguide is drilled from one end a precisely controlled depth, leaving exactly enough distance to machine the transition step from the other end of the block.

Ourtransition, shownin Fig. 2, is much simpler to fabricate. We drill the circular waveguide completely through the metal block fromeitherside. Then we machine the transition slot to the desired end of the block in a single operation. ⑩This transition

can even be addedasan“after-thought” to structures that were created without one.

?Because the circular waveguide diameter is greater than the step height, the transition cross-sectional structure is a complex shape, perturbed by the circular waveguide as shown in Fig. 2(b). However, with available three-dimensional(3-D) numericalelec- tromagnetic simulators and optimizers, we easily can select the transition length and cross-sectional dimensions for the optimum impedance match and lowest insertion loss.

The transition in Fig. 2 is sized to operate from 57 to 64 GHz.? For this frequency range, we use WR-15 rectangular waveguide,0.148 in wide and 0.074 in high with a

T E mode cutoff frequency of 39.9 GHz. ?Full radius WR-15 waveguide, shown in 10

Fig. 2(a), is easier to machine, and its width of 164 mils makes it electrically equivalent to the standard waveguide. Our transition will operate with either waveguide. The circular waveguide has a

T E mode cutoff frequency of 49.1 GHz.

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?The next higher order mode, the

T M mode, cuts off at 64.1 GHz.

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Ⅲ. PERFORMANCE

We have built many of the V-band transitions shown in Fig. 2 and used them on horn antennas, transmitters, and receivers. Fig. 3 shows a photograph of an actual transition. We used computer simulation technology’s (CST) microwave studio to de- sign and analyze the transition, and the predicted and measured input match are shown in Fig. 4. In addition, the predicted performance of a conventional one-step transition (see Fig. 1) is shown for comparison. We measured the transition’s return loss with a WR-15 scalar analyzer. The test fixture consisted of a well-matched circular waveguide horn with the transition machined at its input. We loaded the horn with a crude taper made from foam absorber. The transition’s measured return loss is greater than 15 dB over a 12% bandwidth centered near 60 GHz. The frequency shift of the return loss maximum and overall decrease in return loss are caused by our imperfect V-band load.

?To understand the impact of machining tolerances better, we performed some tolerance analyses with our simulation software. We observed a roughly 200-MHz change in passband center frequency per 0.001-in change in slot height. The center frequency changed about half as much per 0.001-in change in slot width. In both cases, there was essentially no change to the depth of the return loss null at the band center. ?The most sensitive dimension is the depth of the slot, which shifts the passband about 250 MHz higher per 0.001-in decrease.

Because higher order rectangular waveguide modes are above cutoff within the slot transition, and the circular waveguide

T M propagates above 64 GHz, we

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performed simulations to study E- and H-plane misalignment of the WR-15 waveguide relative to the slot transition and circular waveguide, which were kept perfectly aligned. Misalignment along the H-plane (width of slot) slightly perturbs the center frequency of the passband, about 70 MHz increase per 0.001-in offset. Mis-

alignment in the E-plane is more deleterious, with the primary effect being the occurance of a low return loss resonance at 59.3 GHz. WR-15 waveguides are precision aligned with dowel pins, and with these in place we observed no resonance in our measurement (see Fig. 4). However, when we removed the dowel pins and intentionally misaligned the transition and WR-15 test waveguide, we measured the resonance in the return loss at 58.9 GHz.

Ⅳ.CONCLUSION

We have described a novel, single-step, simple to fabricate circular waveguide to rectangular waveguide transition. The transition has the same bandwidth as a conventional single-step transition. It requires a single machining operation to construct and can be added as an “after-thought” to structures that were created without a transition.

REFERENCES

[1]G. Spinner and L. Treczka, “Waveguide transition,” U.S. Patent 3 686 589, Aug. 22, 1972.

[2]M. Schneider, “Coupling for two electromagnetic waveguides with dif- ferent cross-sectional shapes,” U.S. Patent 5 886 588, Mar. 23, 1999.

[3]S. Stuchly and A. Kraszewski, “Wide-band rectangular to circular wave- guide mode and impedance transformer,” IEEE Microw. Theory Tech., vol. 13, no. 5, pp. 379–380, May 1965.

[4]U. Rosenberg, J. Bornemann, and K. Rambabu, “Analysis and design of

flange-integrated rectangular-to-circular waveguide transformers for splashplate antenna feeds,” in Proc. 32nd Eur. Microwave Conf., Milan, Italy, Sep. 2002, pp. 601–604.

[5]M. Mongiardo and C. Tomassoni, “Modal analysis of discontinuities between elliptical waveguides,” IEEE Microw. Theory Tech., vol. 48, no. 4, pp. 597–605, Apr. 2000.

[6]C. Fischer, “Radar rotary joint,” U.S. Patent 4 654 613, Mar. 31, 1987.

一、语言点

①as old as比较级，表示和...一样老

②介词for表目的，the rest of...表示剩余的...

③propagating动名词作定语修饰前面的waveguide

④in which引导的定语从句，说明前面的transition

⑤where引导的定语从句，进一步说明前面的东西

⑥machining动名词作定语，介词to表目的

⑦much like that described in作插入语补充说明，that代词指代前面的东西

⑧greater than...比较级用法，表示比...大

⑨leaving distance动名词短语作状语，后面的to不定式表目的

⑩that引导的定语从句

? as shown...如...所示，shown过去分词表示被动

?介词for表示因为...

?shown过去分词作定语，表被动

?the

T M mode同位语说明前面的mode

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? to不定式表目的

?the depth of... 表示...的深度

二、翻译：

1、④The bandwidth of a stepped transition, in which the rectangular waveguide is matched to the circular waveguide via one or more intermediate structures of constant cross section, increases with the number of steps.

当矩形波导通过一个或多个等截面中间结构与圆波导匹配时，阶跃过渡的带宽随阶跃次数的增加而增加。

2、⑤All these structures require a significant amount of precision machining, especially in the millimeter-wave bands, where the waveguide dimensions are small. 所有这些结构都需要大量的精密加工，特别是在波导尺寸较小的毫米波段。

3、⑨Thus, to machine a one-step transition out of a block of metal,the circular waveguide is drilled from one end a precisely controlled depth, leaving exactly enough distance to machine the transition step from the other end of the block.

因此，为了要加工出一块一步过渡的金属块，圆波导是从一端钻一个精确控制的深度，留出足够的距离，以便从块的另一端加工过渡步骤。

4、?The next higher order mode, the

T M mode, cuts off at 64.1 GHz.

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下一个更高阶模式

T M在64.1GHz时截止。

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5、?To understand the impact of machining tolerances better, we performed some tolerance analyses with our simulation software.

为了更好地理解加工耐受性的影响，我们用仿真软件进行了耐受性分析。