Multi-mode communication device for generating constant envelope modulated signals using a quadrature modulator
View Patent ↗A quadrature modulated transceiver ( 102 ) is used to generate a constant envelope angle modulated signal for communications. To produce the required feedback when operating in the constant envelope mode, an orthogonal frequency division multiplexed receiver ( 136 ) is used.
1. A multi-mode communication device, comprising:
a multi-mode transceiver including a quadrature modulator, the multi-mode transceiver capable of transmitting both amplitude modulated signals and constant envelope angle modulated signals alternatively;
a Cartesian feed back path selectably coupled between transmitter output and a back end module of the of the multi-mode transmitter for providing quadrature feedback when the multi-mode transmitter is transmitting the amplitude modulated signals; and
a wireless local area network (WLAN) transceiver for accessing a wireless local area network, and selectably coupled between the transmitter output and the back end module of the of the multi-mode transmitter for providing quadrature feedback when the multi-mode transmitter is transmitting the constant envelope angle modulated signals.
2. A multi-mode communication device as defined in claim 1 , further comprising a frequency converter selectably coupled between the transmitter output of the multi-mode transmitter and the WLAN transceiver, and wherein the WLAN transceiver operates at a prescribed frequency band, the frequency converter shifts a frequency of a sampled signal sampled from the transmitter output of the multi-mode transmitter to a frequency within the prescribed frequency band.
3. A multi-mode communication device as defined in claim 1 , wherein the WLAN transceiver is programmable to be bandwidth limited.
4. A multi-mode communication device as defined in claim 3 , wherein the multi-mode transceiver comprises:
an IQ signal source which generates an I baseband signal and a Q baseband signal from a circular IQ constellation;
a summing junction which sums the I baseband signal with an I error signal to produce a corrected I signal, and which sums the Q baseband signal with an Q error signal to produce a corrected Q signal;
an IQ modulator which modulates a carrier wave with the corrected I and Q signals to produce a constant envelope IQ modulated carrier;
an amplifier which amplifies the constant envelope IQ modulated carrier to produce an output signal; and
a directional coupler which samples the output signal to produce a sampled signal,
wherein the WLAN transceiver is an orthogonal frequency division multiplexed (OFDM) transceiver module selectively coupled to the directional coupler to receive the sampled signal and produce the I error and Q error signals.
5. A multi-mode communication device as defined in claim 4 , wherein the IQ signal source generates the I and Q baseband signals by applying a digitized voice signal to the circular IQ constellation.
6. A multi-mode communication device as defined in claim 4 , wherein the OFDM transceiver module produces an intermediate frequency (IF) signal from the sampled signal and performs frequency demodulation of the IF signal.
7. A multi-mode communication device as defined in claim 2 , wherein the frequency converter is a harmonic generator for generating a harmonic of the sampled signal, and wherein the harmonic of the sampled signal is within the prescribed frequency band.