Patent ID: 8099064

Claim:
A mobile wireless communications device, comprising: a housing; an antenna supported by the housing; a circuit board carried by the housing and having radio frequency (RF) circuitry operative with the antenna for receiving and transmitting RF signals through the antenna, including a transmission line and power amplifier for amplifying RF signals to be transmitted over the transmission line to the antenna; an antenna switch carried by the circuit board and connected to said antenna and RF circuitry for switching between receiving and transmitting RF signals through the antenna; and an RF metal shield surrounding said power amplifier and antenna switch for isolating said power amplifier and antenna switch from said antenna and RF circuitry, and further comprising a low pass filter within the transmission line and having an input connected to said power amplifier and an output connected to said antenna switch, said low pass filter comprising an RLC filter having a resistor, inductor and capacitor, wherein at a fundamental frequency, the impedance of the capacitor is higher than a predetermined resistance and the impedance of the inductor is lower than a predetermined resistance, and at higher harmonic frequencies, the impedance of the capacitor is reduced and configured to reduce any RF coupling of Voltage Standing Waves of upper harmonic frequencies from the power amplifier into the antenna switch between the input and output of the low pass filter through the RF shield while maintaining transmission of signals through the transmission line at a desired fundamental frequency.