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XC0900A-20 参数 Datasheet PDF下载

XC0900A-20图片预览
型号: XC0900A-20
PDF下载: 下载PDF文件 查看货源
内容描述: 20分贝定向耦合器 [20 dB Directional Coupler]
分类和应用:
文件页数/大小: 23 页 / 576 K
品牌: ANAREN [ ANAREN MICROWAVE ]
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Model XC0900A-20  
Rev F  
The effects of the test fixture on the measured data must be minimized in order to accurately determine the  
performance of the device under test. If the line impedance is anything other than 50Ω and/or there is a discontinuity  
at the microstrip to SMA interface, there will be errors in the data for the device under test. The test environment can  
never be “perfect”, but the procedure used to build and evaluate the test boards (outlined below) demonstrates an  
attempt to minimize the errors associated with testing these devices. The lower the signal level that is being  
measured, the more impact the fixture errors will have on the data. Parameters such as Return Loss and  
Isolation/Directivity, which are specified as low as 27dB and typically measure at much lower levels, will present the  
greatest measurement challenge.  
The test fixture errors introduce an uncertainty to the measured data. Fixture errors can make the performance of the  
device under test look better or worse than it actually is. For example, if a device has a known return loss of 30dB and  
a discontinuity with a magnitude of –35dB is introduced into the measurement path, the new measured Return Loss  
data could read anywhere between –26dB and –37dB. This same discontinuity could introduce an insertion phase  
error of up to 1°.  
There are different techniques used throughout the industry to minimize the affects of the test fixture on the  
measurement data. Anaren uses the following design and de-embedding criteria:  
Test boards have been designed and parameters specified to provide trace impedances of 50  
±1Ω. Furthermore, discontinuities at the SMA to microstrip interface are required to be less than  
–35dB and insertion phase errors (due to differences in the connector interface discontinuities  
and the electrical line length) should be less than ±0.25° from the median value of the four  
paths.  
A “Thru” circuit board is built. This is a two port, microstrip board that uses the same SMA to  
microstrip interface and has the same total length (insertion phase) as the actual test board. The  
“Thru” board must meet the same stringent requirements as the test board. The insertion loss  
and insertion phase of the “Thru” board are measured and stored. This data is used to  
completely de-embed the device under test from the test fixture. The de-embedded data is  
available in S-parameter form on the Anaren website (www.anaren.com).  
Note: The S-parameter files that are available on the anaren.com website include data for frequencies that are  
outside of the specified band. It is important to note that the test fixture is designed for optimum performance through  
2.3GHz. Some degradation in the test fixture performance will occur above this frequency and connector interface  
discontinuities of –25dB or more can be expected. This larger discontinuity will affect the data at frequencies above  
2.3GHz.  
Circuit Board Layout  
The dimensions for the Anaren test board are shown below. The test board is printed on Rogers RO4350 material  
that is 0.030” thick. Consider the case when a different material is used. First, the pad size must remain the same to  
accommodate the part. But, if the material thickness or dielectric constant (or both) changes, the reactance at the  
interface to the coupler will also change. Second, the linewidth required for 50Ω will be different and this will introduce  
a step in the line at the pad where the coupler interfaces with the printed microstrip trace. Both of these conditions will  
affect the performance of the part. To achieve the specified performance, serious attention must be given to the  
design and layout of the circuit environment in which this component will be used.  
If a different circuit board material is used, an attempt should be made to achieve the same interface pad reactance  
that is present on the Anaren RO4350 test board. When thinner circuit board material is used, the ground plane will  
be closer to the pad yielding more capacitance for the same size interface pad. The same is true if the dielectric  
constant of the circuit board material is higher than is used on the Anaren test board. In both of these cases,  
narrowing the line before the interface pad will introduce a series inductance, which, when properly tuned, will  
compensate for the extra capacitive reactance. If a thicker circuit board or one with a lower dielectric constant is used,  
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(315) 432-8909  
(800) 411-6596  
+44 2392-232392  
Available on Tape  
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