SBAA555 august   2023 AFE8092

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2RF Droop
    1. 2.1 Reasons Behind RF Droop
    2. 2.2 Digital Correction of RF Droop
    3. 2.3 Overview of RF Droop Correction Measurements
    4. 2.4 Enabling the RF Droop Correction
    5. 2.5 Example for Using the RF Droop Correction
    6. 2.6 Frequency Response Before and After Droop Correction and Limitations
  6. 3Summary
  7. 4References

2.1 Reasons Behind RF Droop

One of the important performance requirements in the RF Transmitter is to provide constant power across frequency in the band being used. Multiple external and internal factors (to the device) cause change in the output power across frequency. This phenomenon is referred to as RF droop in this document. An overview of reasons causing the RF droop is given below

  1. Capacitors or inductors in the path: The output path of a transmitter contains multiple capacitors and inductors either for some design purpose or can occur as parasitic components. Since the impedance of these components changes with frequency, the output power changes across frequency.
  2. Matching Circuits: Matching circuits are designed to make the frequency response as flat as possible by matching the device impedance to the characteristic impedance of the transmission system. Still some amount of non-flat frequency response is seen due to the insertion losses and reflected power. Such frequency variation becomes prominent for wide band applications as designing matching circuits for wide band applications is quite difficult.
  3. Power amplifier: In general, systems employ a power amplifier at the output of transmitter and before the antenna as shown in Figure 2-1. This power amplifier also gives rise to a particular frequency response according to the parameters.