University of Twente Student Theses
AM/PM Conversion in Transceiver Systems
Zanten, S. van (2017) AM/PM Conversion in Transceiver Systems.
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| Abstract: | One nonlinear effect in transceiver systems is the phase modulation at the output due to amplitude modulation at the input (AM/PM conversion). These changes in phase are undesired and limit the performance of RF systems. For the development of new technologies like advanced radar, suppression of AM/PM conversion effects will be vital. This research has focussed on characterizing these effects in a simplified model to gain insight that can be used to synthesize better transceiver systems. To this end, a first-order low-pass RC-circuit with a nonlinear capacitor has been presented as a simplified equivalent circuit to heterojunction bipolar transistors (HBTs) for the modelling of AM/PM conversion effects in transceiver systems. Two different analyses have been performed to characterize the AM/PM conversion effects in this simplified RC-circuit after which the impact of circuit parameters on the effects has been identified. To deepen insight, several simplifications and assumptions have been introduced in both analyses; their impact on the model accuracy has been considered. First, a frequency domain analysis has been conducted to characterize the nonlinear phase component of the fundamental frequency that depends on the input amplitude. This model is only valid for modelling weak nonlinearities due to the omission of the influence of higher harmonics, but has shown to be a good approximation to AM/PM conversion in HBTs for relatively small input amplitude values. A second method does include these higher harmonics; this time domain based analysis of the deviation in zero-crossing timings was found to hold for slightly stronger nonlinearities in HBTs. Theoretical analysis in both the frequency and time domain indicated that the AM/PM conversion effects in the first-order low-pass RC-filter could be reduced by reducing either the value of the resistor, the value of the third-order nonlinear capacitance constant or the input frequency. Simulations have verified these claims, but have also shown that the cut-off frequency plays a major role in the accuracy of the theoretical approximations. |
| Item Type: | Essay (Bachelor) |
| Faculty: | EEMCS: Electrical Engineering, Mathematics and Computer Science |
| Subject: | 53 electrotechnology |
| Programme: | Electrical Engineering BSc (56953) |
| Link to this item: | https://purl.utwente.nl/essays/74220 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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