WIRELESS SYSTEM HAVING HIGH SPECTRAL PURITY
A wireless system having high spectral purity output signals. The wireless system has a transmitter circuit for transmitting an output signal and a power amplifier for amplifying the output signal for wireless transmission via an antenna. Positioned in-line with the output signal between the transmitter circuit and the power amplifier is a harmonic trap configured for inhibiting harmonics within a predetermined frequency range generated by the power amplifier from leaking into the transmitter circuit. The harmonic trap can be implemented as a discrete device, or integrated within the transmitter circuit or integrated within the power amplifier. By inhibiting the harmonics from leaking into the transmitter circuit, degraded performance of the transmitter circuit is prevented.
1 . A wireless device comprising:
a transmit circuit for providing an output signal at a transmit frequency;
a power amplifier for receiving the output signal and providing an amplified output signal, the power amplifier generating harmonics at a specific frequency; and,
a harmonic trap for passing the output signal having the transmit frequency and for inhibiting the harmonics from passing into the transmit circuit.
2 . The wireless device of claim 1 , wherein the specific frequency is an integer multiple of the transmit frequency.
3 . The wireless device of claim 1 , wherein the harmonic trap is a discrete device positioned in a path of the output signal between the transmit circuit and the power amplifier.
4 . The wireless device of claim 1 , wherein the harmonic trap is integrated with the transmit circuit.
5 . The wireless device of claim 1 , wherein the harmonic trap is integrated with the power amplifier.
6 . The wireless device of claim 1 , wherein the harmonic trap is a passive circuit.
7 . The wireless device of claim 6 , wherein the passive circuit includes a capacitor configured to have a frequency response effective for attenuating the harmonics at the specific frequency.
8 . The wireless device of claim 6 , wherein the passive circuit includes a set of capacitors selectively enabled in parallel with each other to have a frequency response effective for attenuating the harmonics at the specific frequency.
9 . The wireless device of claim 1 , wherein the harmonic trap is an active circuit.
10 . The wireless device of claim 1 , wherein the transmit circuit and the power amplifier are soldered to a printed circuit board, and the harmonic trap is integrated in the printed circuit board as distributed transmission lines.
11 . A radio frequency transceiver for providing an output signal to a power amplifier, comprising:
a transmitter core for generating the output signal at a transmit frequency; and,
a harmonic trap for passing the output signal having the transmit frequency, and for inhibiting harmonics at a specific frequency from entering the transmitter core, the harmonics being generated by the power amplifier.
12 . The radio frequency transceiver of claim 11 , wherein the specific frequency is an integer multiple of the transmit frequency.
13 . The radio frequency transceiver of claim 11 , wherein the harmonic trap is a passive circuit.
14 . The radio frequency transceiver of claim 11 , wherein the harmonic trap is an active circuit.
15 . A power amplifier for providing an amplified signal corresponding to an output signal received from a transmitter circuit, comprising:
amplification circuitry receiving the output signal for generating the amplified signal, the amplification circuitry generating harmonics at a specific frequency; and,
a harmonic trap for passing the output signal having a transmit frequency, and for inhibiting the harmonics from passing to the transmitter circuit.
16 . The power amplifier of claim 15 , wherein the specific frequency is an integer multiple of the transmit frequency.