X3C09P2-30S Datasheet, PDF (20/23 Pages) Anaren Microwave – 30 dB Directional Coupler

Model X3C09P2-30S
Rev B
INPUT
1
4
FORWARD
MEASUREMENT
ISOLATOR
2
3
**TERMINATION
LOAD
Reflected
Wave
REVERSE
MEASUREMENT
*Recommended Terminations
Power (Watts)
Model
8
RFP- 060120A15Z50-2
10
RFP- C10A50Z4
16
RFP- C16A50Z4
20
RFP- C20N50Z4
50
RFP- C50A50Z4
100
RFP- C100N50Z4
200
RFP- C200N50Z4
Figure ap.n.1-2. Forward and Reverse Sampling
The isolator in Figure ap.n.1-2 prevents the reflected wave from exciting the directional coupler. A list of recommended
terminations is shown in the figure.
Directional Couplers in Feed-Forward Amplifier Applications
Feed-forward amplifiers are widely used to reduce distortion due to nonlinearities in power amplifiers. Although the
level and complexity of feed-forward amplifiers varies from one manufacturer to another, the basic building block for this
linearization scheme remains the same. A basic feed-forward schematic is shown in Figure ap.n.2-1. The input signal
is split in two using a hybrid coupler or power divider. The output of the main amplifier is sampled with a 20dB-30dB
directional coupler. The X3C09P2-30S is an excellent candidate for this sampling since it provides great return loss and
directivity. The sampled signal, which consists of a sample of the original input signal plus some distortion, is inverted
and then combined with the output of the first delay line. This procedure subtracts (through destructive interference) the
sample of the original input signal, leaving only the distortion or error component. The error component is then
amplified and combined with the output of the second delay line using another directional coupler. In many cases, a
10dB coupler is used to combine the two signals. The XC0900E-10 is a perfect choice for this injection because it has
tight coupling, superior directivity, and excellent match.
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