Transmission arrangement, particularly for mobile radio
View Patent ↗The invention specifies a transmission arrangement, particularly for mobile radio, which has a homodyne design and in which a feedback path is routed from the input or from the output of the vector modulator ( 10, 11, 12, 14 ) via a switch ( 20 ) and an A/D converter ( 19 ) back to the digital signal processing ( 3 ) in baseband ( 1 ). As a result, it is a particularly simple matter to detect offsets and amplitude mismatches and to correct them without difficulty in a digital signal processor ( 3 ). This allows both significantly improved carrier frequency suppression and significantly improved sideband suppression to be achieved with little complexity. The mobile radio transmitter described is particularly suitable for use in modern mobile radio systems such as GSM EDGE and UMTS.
1. A transmission arrangement for a mobile radio, comprising:
a baseband signal processing unit configured to condition a useful signal comprising an inphase component and a quadrature component with a respective digital/analog converter, and provide such conditioned useful signal components at an inphase path output and a quadrature path output, respectively;
a frequency converter comprising an inphase input coupled to the inphase path output, and a quadrature input coupled to the quadrature path output of the baseband signal processing unit, and further comprising an output, and configured to provide a modulated signal derived from the useful signal at the frequency converter output; and
a feedback path comprising an analog/digital converter comprising an input connected to the inphase input and to the quadrature input of the frequency converter via a respective switch, and comprising an output connected to a control input of the baseband signal processing unit,
wherein the baseband signal processing unit is configured to alter one of the inphase component and the quadrature component of the useful signal in response to a signal at the control input.
2. The transmission arrangement of claim 1 , wherein the frequency converter comprises a quadrature modulator, the quadrature modulator comprising:
a first radio-frequency mixer comprising a first input connected to the inphase path output, and a second input configured to receive a carrier signal, and configured to up-convert the inphase component to a frequency associated with the carrier signal;
a second radio-frequency mixer comprising a first input connected to the quadrature path output, and a second input configured to receive the carrier signal, and configured to up-convert the quadrature component to the frequency associated with the carrier signal; and
a summing element comprising inputs connected to outputs of the first and second radio-frequency mixers, respectively, and configured to combine the outputs of the first and second radio-frequency mixers and provide such combination at an output that forms the output of the frequency converter,
wherein the input of the analog/digital converter in the feedback path is connected to the first inputs of the first and second radio-frequency mixers via a respective switch.
3. The transmission arrangement of claim 2 , wherein the first radio-frequency mixer and the second radio-frequency mixer each comprise, at their first inputs, a means for tapping off a signal which is proportional to the inphase component and the quadrature component, respectively.
4. The transmission arrangement of claim 3 , wherein each of the first and second radio-frequency mixers further comprise:
a controlled current source coupled to the respective first input, and configured to supply current as a function of the inphase component and the quadrature component, respectively;
a mixer cell coupled to the controlled current source and configured to mix the inphase component and the quadrature component with the carrier signal, respectively; and
a supplemental current source coupled to the controlled current source, and configured to generate a signal that is proportional to the inphase component and the quadrature component, respectively, and provide the signal at the feedback path.
5. The transmission arrangement of claim 4 :
wherein the controlled current sources each comprise transistors in a respective current mirror, the current mirrors each comprising a transistor and a diode-connected transistor connected thereto, and configured to actuate the transistor, and
wherein the supplementary current sources each comprise a transistor having a control input connected to the diode-connected transistor.
6. The transmission arrangement of claim 1 , further comprising two voltage/current converters respectively connected between the outputs of the respective digital/analog converters in the baseband signal processing unit and the first inputs of the first and second radio-frequency mixers.