In this bachelor thesis the design process of the audio and intermediate frequency amplifiers for a wireless FM tranceiver is documented and explained. The project was done using only descrete components for educational purposes.

This report details the design and implementation of subsystems within a wireless FM transceiver. All the subsystems will be developed and integrated into a working FM transceiver. The subsystems discussed in this report are the modulator and demodulator. The modulator, on the transmitter side, varies the carrier wave frequency, based on the input audio signal. The demodulator, on the receiver side, can detect these variations and retrieve the audio signal. The modulator is implemented using a voltage controlled oscillator, which is based on the Colpitts oscillator. The input audio signal controls the oscillation frequency by modulating varicaps. The demodulator consists of mixer, amplifier and a slope detector. The amplifier is not discussed in this thesis. The mixer uses a local oscillator to shift the RF input signal to an intermediate frequency. This thesis proposes a mixer integrated into a local oscillator, using only one transistor. The detector is based on a slope detector, which differentiates the FM signal and converts it into an AM signal. The differentiator is implemented using a bandpass filter. The audio signal is retrieved from the AM signal using an envelope detector. The work will be concluded with a display of the complete FM transceiver circuit.

This thesis explains the design process of two subsystems of a radio transmitter and receiver. The goal of the project is to transmit audio over a distance using FM modulation. This report will focus on the power amplifier leading to the transmitting antenna and the low noise amplifier connected to the receiving antenna. A design process for a class E power amplifier and a low noise amplifier will be discussed.

In this thesis, a new RF Power Amplifier design is proposed that targets for improving the efficiency profile of classical RF Amplifiers. This RF Power Amplifier is especially designed for modulation schemes that need a PA with high PAPR. The PA consists of two different stages that will be digitally controlled. One of these stages has an optimized efficiency profile for supporting input signals with nominal power and the other stage has an optimized efficiency profile for supporting input signals with peak power. The PA has been designed with GaN HEMT's which perform very well at high frequencies while delivering high power.

The PA has been designed to perform optimally for frequencies around 100 MHz. Simulations show that at peak power, which is 40 dBm for this amplifier design, the PA has an efficiency of 63.5%. At 6 dB power back-off, the PA has an efficiency of 65.5%. The PA has a gain of approximately 20 dB at peak power level and approximately 18 dB at nominal power level. Furthermore the stability of the PA is optimized for the carrier frequency of the input signal. At 100 MHz the Rollet Stability Factor K is of magnitudes higher than unity which guarantees the stability of the circuit.

Furthermore a PCB has been developed to do some investigations in how this new PA design will perform in practice. Measurements on this PCB show that in power back-off a maximum efficiency of 63% can be reached. Results of the performance at peak power show that the efficiency reaches a maximum level of 37%. A possible reason for this is insufficient suppression of undesired harmonics.

The objective of the bachelor graduation project detailed in this thesis is the development of a system suited for testing radio frequency (RF) power amplifiers (PAs). This PA test system is in particular set up for testing two-transistor interpolating-supply amplifiers.
Interpolating-supply PAs are efficiency-enhanced by employing multiple transistors supplied by different, fixed drain supply voltages, leading to different efficiency characteristics, which are then combined by switching between the transistors, resulting in an enchanced overal efficiciency. Turning on the right amplifying transistor takes place digitally by pre-adjusting the different data inputs or control of gate biases.
The PA test system is required to provide support for measurement and signal generation for 40 dBm output power of a 20 dB gain PA. Moreover, it is required to provide remote control access to the measurement equipment and automation of the tests, implemented in MATLAB.
The to-be-measured PA performance metrics were constrained to static tests for drain efficiency, power-added efficiency, AM/AM distortion, total harmonic distortion (THD) and intermodulation distortion (IMD).
In order to meet the requirements while making use of the available resources, it was recognized that the following subsystems were necessary:
• Baseband signal generation using a DAC;
• RF signal generation using a to-be-calibrated IQ modulator;
• Pre-amplifier, by own design; and
• Spectrum analyzer, controlled remotely.
The baseband signal generation subsystem was characterized with respect to noise and gain performance, which resulted in the making of noise-reducing LC low-pass filters. The provided IQ modulators were successfully calibrated for device non-idealities in an automated MATLAB GUI, allowing for clean RF signal generation. Three pre-amplifiers with over 27.5 dB power gain were realized for sufficient PA input power. A set of MATLAB functions and scripts for the spectrum analyzer and top-level control was written, enabling semi-automatic PA testing.
At the time of writing this thesis, the PA test system was put in use to characterize and evaluate two interpolating supply PAs. For automation, another GUI was implemented for the PA test system. The system proved to be able to determine PA input, output and DC power to measure the gain, linearity and efficiency in multiple static tests and for different PA bias conditions. Also THD and IMD for single-transistor were measured using the PA test system. The results were to a realistic extent similar to the simulated PA characteristics, aside from some anomalies which could possibly be explained by PA design implementation mistakes or test system nonidealities.