Circuit arrangement for a predistorted feedback coupling from a transmitter to a receiver in a multi-mode mobile telephone
A circuit arrangement for a multimode mobile telephone that transmits and receives signals to and from various mobile radio networks contains a baseband and a transceiver unit. The transceiver unit includes a digital adaptive predistorter having a switching element. The switching element is arranged so that an optional connection is created. The optional connection connects an amplifier output to an input of a receiver causing that receiver input to be disconnected from an antenna changeover switch. This way, it is possible for the receiver to be disconnected from a transmitting and receiving antenna during periods when the receiver is not receiving signals from the transmitting and receiving antenna. While the receiver is disconnected from the transmitting and receiving antenna, the receiver is able to receive other signals. By using a simple switch the receiver can be disconnected from the transmitting and receiving antenna, and at the same time establish a connection between the output of the transmitter amplifier and the input of the receiver. By doing so, the receiver is able to tap off and detect signals at the output of the transmitter amplifier.
1. A circuit arrangement for a multimode mobile telephone comprising:
a baseband comprising a first analog to digital converter, a second analog to digital converter and a digital to analog converter;
a transceiver unit comprising a first receiver, a second receiver, an amplifier, an antenna changeover switch, and a receiving antenna, an output of the first receiver being connected to the first analog to digital converter, an output of the second receiver being connected to the second analog to digital converter, an input of the amplifier being connected to the digital to analog converter, an input of the first receiver being connected to the antenna changeover switch, an input of the second receiver being connected to the antenna changeover switch, an output of the amplifier being connected to the antenna changeover switch, and the antenna changeover switch being connected to the receiving antenna, wherein the second receiver provides a feedback branch using digital adaptive predistortion; and
a switching element that creates an optional connection by connecting the amplifier output to the second receiver input whereby the second receiver input is disconnected from the antenna changeover switch.
2. The circuit arrangement of claim 1 , wherein said switching element is arranged in the antenna changeover switch.
3. The circuit arrangement of claim 1 , wherein the first receiver is designed to receive signals from the UMTS network.
4. The circuit arrangement of claim 1 , wherein the second receiver is designed to receive signals from the GSM network.