For the first time, a fully functional single-chip "Direct Conversion Transceiver" for future mobile communications is presented. This single-chip transceiver contains all RF functions except the antenna. It has been realised in a silicon bipolar 0,s pm / 25 GHz technology and is operating up to 1.5 GHz. This enables for the first time a two-chip "communicator" handheld (RF transceiver chip + baseband processor chip).Introduction For second generation mobile communications at 1 -2 GHz (GSM, DECT, UMTS, PCN,..) there are three open findamental questions for the RF part:Architecture of the transceiver for lowest cost and lowest overall power consumption 0 degree of monolithic integration of the RF components -is a single chip RF transceiver feasible?This paper gives answers to all the questions mentioned. The direct conversion principle was proposed for receivers about 10 years ago [l]. It has been applied to a pager at the frequency of 150 MHz. The extension of the principle to the transmitter at the same chip and the operation up to 900 MHz, but with lower degree of integration has been described recently [2]. To the knowledge of the authors no complete integration has been published.Architecture Figure 1 shows the transceiver concept. The quadrature down converter" of the receiver (top) and the quadrature up converter" of the transmitter (bottom) are seen in the middle of Fig. 1. Both quadrature converters are supplied with a quadrature LO signal from the phase shifter via a multiplexer. The phase shifter is realised by a 2:l static frequency divider with outputs taken from the master and the slave flip flop. Master and slave are driven by clock signals with 180" phase shift at twice the LO frequency. Dividing by two yields a 90" phase shift between master and slave outputs. Such a phase shifter concept allows for operation from dc up to the maximum toggle frequency of the 2:l divider so that operation in the full spectrum is secured. This concept avoids crosscoupling from the VCO to the receiving path because the VCO is oscillating at twice the LO frequency. Coupling from LO to the receiving input is one of the critical factors for "Direct Conversion" receivers because it causes a dc offset at the baseband 0 0 which semiconductor technology can be applied? output. The operating frequency range of the transceiver is determined by the VCO which is fixed by an external resonator. The fine tuning of the VCO is managed by the integrated dual modulus prescaler and an external low frequency PLL circuit.Receiver The receiver consists of a LNA followed by two variable gain amplifiers (VGA) and the quadrature down-converter.In the case of "Direct Conversion" the F W input pin can be supplied with the antenna signal because no mirror rejection filtering is necessary. The channel selection is achieved by lowpass filters at the quadrature downconverter outputs. This filtered baseband signal can be demodulated. The quadrature down-converter is highly flexible with respect to modulation. With this receiver architecture all a...
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