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RF2504 参数 Datasheet PDF下载

RF2504图片预览
型号: RF2504
PDF下载: 下载PDF文件 查看货源
内容描述: VCO /高隔离缓冲放大器 [VCO/HIGH-ISOLATION BUFFER AMPLIFIER]
分类和应用: 缓冲放大器射频微波分离技术隔离技术
文件页数/大小: 8 页 / 95 K
品牌: RFMD [ RF MICRO DEVICES ]
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Preliminary  
RF2504  
Application Notes  
The RF2504 has two functional parts: an oscillator and  
buffer amplifier. The functional blocks have separate  
ground and VCC pins to increase the isolation and  
reduce load pulling, one of the key design objectives.  
An external resonator is used to add design flexibility,  
and the loaded Q of this resonator will affect the perfor-  
mance of the resulting oscillator.  
The overall Q of the external resonator will affect per-  
formance. Lower Q means lower power, higher phase  
noise, and more load pulling. If the Q is too low, the cir-  
cuit will not oscillate. The IC is designed to oscillate  
into a resonator with Q>10. The performance is mea-  
sured with a microstrip resonator or high quality induc-  
tor, which usually has a Q>50. These measurements  
define the best performance that can be expected from  
the ICs. Lower Q resonators, particularly those includ-  
ing a lossy varactor, might have degraded perfor-  
mance.  
To create an oscillation, negative resistance is gener-  
ated at pin 2 with a circuit similar to a Colpitts oscillator.  
The input impedance at pin 2, measured with a vector  
network analyzer, is shown here in the data sheet. In  
general, the impedance looks like a negative resis-  
tance in series with a capacitor. The negative resis-  
tance decays as the frequency increases. An oscillator  
is created when an inductive element is placed on pin  
2 that is the conjugate of the capacitive reactance. A  
greater inductive element will create a lower frequency  
of oscillation.  
The specified output power is measured into a 50Ω  
load. The IC has a high output impedance, and if  
desired, output matching can be used to obtain more  
power by transforming 50into a higher impedance.  
On the RF2504, this could be accomplished by simply  
changing the values of the external output inductor and  
capacitor.  
The S11 looking into pin 2 is also shown here in the  
data sheet. It has return gain from 500 MHz to 2200  
MHz at room temperature. The specified frequency  
range of 750 MHz to 1500 MHz defines the region  
where the output power is relatively flat. At lower and  
higher frequencies, the power will tend to roll off from  
the nominal value. The specified frequency range is  
conservatively set to ensure oscillation and maintain  
performance, but the RF2504 can be used over a  
broader frequency range with degraded performance.  
12  
12-4  
Rev A2 010117