Direct modulation transmitter utilizing signals squaring
View Patent ↗A apparatus to provide a direct modulation transmitter having high dynamic range and low distortion using signal processing at a first frequency level for a signal to be transmitted and increasing frequency to transmission frequency in a manner to avoid distortion and utilizing a squaring function in up-converting basic processing signal.
1. A direct conversion transmitter comprising:
signal means providing an input signal at a baseband frequency;
a square root circuit receiving the input signal and providing a modulation input signal for a modulator at a square root of the input signal at the baseband frequency;
the modulator modulating the output of the square root circuit, the modulator operating on a modulation frequency of one half RF, where RF is a transmission frequency of the direct conversion transmitter, to convert the input signal to one half RF;
a variable gain amplifier coupled to the output of the modulator,
a squaring circuit coupled to an output of the variable gain amplifier and squaring the modulated signal to convert the output of the variable gain amplifier to the transmission frequency; and
gain control means for providing dynamic range in the transmission frequency, the gain control means providing an output for coupling to a transmission antenna.
2. The transmitter according to claim 1 wherein the signal means provides an in-phase signal and quadrature signal for modulation and wherein the modulator comprises a Gilbert cell modulator.
3. The transmitter of claim 2 wherein the circuit is comprised in a digital signal processor receiving the input signals.
4. The transmitter of claim 2 wherein the square root circuit comprises an analog circuit.
5. The transmitter of claim 3 wherein the squaring circuit comprises a Gilbert multiplier.
6. A direct conversion transmitter comprising:
signal means providing an input signal at a baseband frequency;
a square root circuit receiving the input signal and providing a modulation input signal for a modulator at a square root of the input signal at the baseband frequency;
the modulator modulating the output of the square root circuit, the modulator operating on a modulation frequency of one half RF, where RF is a transmission frequency of the direct conversion transmitter, to convert the input signal to one half RF;
a squaring circuit coupled to an output of the modulator and squaring the modulated signal to convert the output of the modulator to the transmit frequency; and
gain control means for providing dynamic range in the transmission frequency, the gain control means providing an output for coupling to a transmission antenna.
7. The transmitter according to claim 6 wherein the signal means provides an in-phase signal and quadrature signal for modulation and wherein the modulator comprises a Gilbert cell modulator.
8. The transmitter of claim 7 wherein the square root circuit is comprised in a digital signal processor receiving the input signals.
9. The transmitter of claim 8 wherein the squaring circuit comprises a Gilbert multiplier.
10. The transmitter of claim 7 wherein the square root circuit comprises an analog circuit.