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A stereo FM-radio transmitter with Radio Data System (RDS) support based on an all-digital PLL is presented. It has been designed as a fully integrated single-chip transmitter in a 90-nm CMOS technology to be compatible with digital deepsubmicrometer processes. Target application of the proposed system is the cointegration with baseband processors and transmitters for mobile communication systems. Nowadays mobile phones have a lot of multimedia capabilities e. g. an integrated MP3 player. The proposed transmitter enables a mobile device to stream audio data to a FM receiver which is popular and existing in most households world wide. RDS support allows to send additional information e. g. title and artist of a song. As mobile applications are the main target for the transmitter great attention has been attached to saving power and area. Therefore, the presented transmitter works on a 1V supply voltage and is aimed for using a 32.768 kHz reference crystal oscillator instead of the commonly used 26MHz reference oscillator while still providing wideband frequency modulation capability.

The design of a multi-GHz digitally controlled oscillator (DCO) achieving low noise and power consumption is presented. The DCO is part of an all-digital phase lock loop (ADPLL) for an FM-radio transmitter prototype chip designed in a 90nm CMOS process. For this application the oscillator frequency of 3.05–3.45GHz is divided by 32 or 36 to cover the frequency span of 87.5–108.0MHz. A wide tuning range combined with a precise frequency tuning is achieved by different digitally controlled variable capacitors grouped as banks. Different approaches of these variable capacitors and oscillator topologies are simulated and compared. The design is chosen considering low phase noise combined with low power consumption. The power consumption of the designed DCO core is below 1.7mW at 1V supply voltage. This setup shows a phase noise below −154 dBc Hz at 20MHz offset. The chip area utilised by one DCO is 260 × 500 µm. Simulations show the performance of this DCO is state-of-the-art.