On-channel transceiver architecture in a dual band mobile phone

A radio transmitting and receiving apparatus for generating a signal for transmission on a transmit frequency and for receiving a signal on a receive frequency, comprising:

• a first downconvertor for mixing said received signal with a first local oscillator frequency signal and converting it to a first intermediate frequency signal;
• a second downconvertor for mixing said first intermediate frequency signal with a second local oscillator frequency signal and converting it to a second intermediate frequency;
• reference means for providing a reference frequency signal;
• first local oscillator frequency synthesizer means having a first input for said first local oscillator frequency signal and a second input for said reference frequency signal and in dependence thereon producing a control signal to control said first local oscillator to produce the desired first local oscillator frequency signal;
• second local oscillator frequency synthesizer means having a first input for said second local oscillator frequency signal and a second input for said reference frequency signal and producing in dependence thereon a control signal to control said second local oscillator to produce the desired second local oscillator frequency signal;
• transmit oscillator means for generating a transmit frequency signal;
• transmit downconvertor means for mixing the transmit frequency signal with the first local oscillator signal to produce a lock frequency signal;
• transmit synthesizer means having a first input for the lock frequency signal and a second input for the reference frequency signal and in dependence thereon producing a control signal for the transmit oscillator means to control the transmit frequency signal.