Direct-conversion transmitter circuit and transceiver system
View Patent ↗Disclosed is a direct conversion type transmitter or transceiver circuit suitable for a mobile communication device which corresponds to broad signal output level variable width to be required by W-CDMA, which does not necessitate any high-performance low noise VCO and RF filter, capable of reducing a number of components and the cost. In the input portion of an orthogonal modulator composed of a divider, mixers, and a common load, there are provided variable attenuators. If an input signal level of the orthogonal modulator within the transmitter circuit lowers, this variable attenuator circuit is operated so as to lower the bias of the orthogonal modulator to reduce the amount of occurrence of carrier leak, and to prevent the signal during low output level and carrier leak ratio from being deteriorated. The direct conversion transmitter circuit is capable of easily realizing output level variable width of 70 dB or higher and reducing a variable amount in the high frequency circuit in which it is difficult to secure the variable gain width.
1. A transceiver integrated circuit chip comprising:
a plurality of interconnected different transceiver circuits capable of processing GSM, W-CDMA, and GSM-1800 signals respectively and formed monolithically on the transceiver integrated circuit chip;
a switch capable of switching between GSM, W-CDMA, and GSM-1800 transceiver operation depending upon the type of signal transmitted or received; and
an orthogonal modulator,
wherein said orthogonal modulator comprises:
a divider;
a plurality of mixers;
a common load to said plurality of mixers; and
a plurality of variable attenuators,
wherein each of the plurality of mixers has two input ports to which outputs of said divider and said variable attenuators are connected respective; and
wherein, if an input signal level of said orthogonal modulator within the transceiver integrated circuit chip becomes lower by adjusting gain of said variable attenuators, each bias current of said plurality of mixers becomes lower to reduce the amount of occurrence of carrier leak, and to prevent carrier leak ratio from being deteriorated.
2. The transceiver integrated circuit chip according to claim 1 ,
wherein a respectively different bias current is sent to each of said transmitter circuits from a bias current source,
wherein a selected transceiver circuit to be operated, from among said plurality of interconnected different transceiver circuits capable of processing GSM, W-CDMA, and GSM-1800 signals respectively, is switched at said switch in accordance with transmitting or receiving signal power which is controlled by a variable attenuator, and
wherein thereby transceiver maintains an acceptable signal to noise ratio for operation.
3. The transceiver integrated circuit chip according to claim 1 ,
wherein one of said plurality of interconnected different transceiver circuits capable of processing GSM, W-CDMA, and GSM-1800 signals respectively, is a digital circuit structured to process GSM signals and W-CDMA signals in the same circuit.
4. The transceiver integrated circuit chip according to claim 1 ,
wherein a signal output level has an adjustable useable width of 70 dB or higher for compatibility with W-CDMA systems.