Motorola Corporation

Sek Loon Chan

Chacko Prakash

Pek B Teo

Wan F Tay

Gee S Kok

Sin Hooi Cheah

Hock S Lim

A coupling circuit (,) for a radiofrequency (RF) receiver (,) has an attenuator (,) and a resonator (,). Three resistors (,) of attenuator (,) provide a lossy resistive isolation between a first mixer (,) and a crystal filter (,) of (RF) receiver (,) for undesired signals such as noise and harmonics. Thus, signal reflections between first mixer (,) and crystal filter (,) are absorbed for these undesired signals. However, for desired signals at an intermediate frequency (IF), resonator (,) has an inductor (,) and a capacitor (,) to resonate with such desired signals at the IF. As a result of resonance, resistors (,) are isolated to alleviate attenuation of the desired signals.

Coupling circuit to reduce intermodulation distortion in radiofrequency receivers

A four port antenna switch (300) for switching a receive port (320) and a transmit port (310) between a remote antenna port (330) and a standard antenna port (340) is provided. The switching actions of the receive port (320) between the remote antenna port (330) and the standard antenna port (340) is provided by a relay (350) under the control of a relay controller (352, 354, 400). The switching of the transmit port (310) between the standard antenna port (340) and the remote antenna port (330) is provided by diode switches (360, 370) under the control of diode switch controllers (332, 324, 312, 314, 400). The switching actions of the relay (350) and the diode switches (370, and 360) is complementary to each other, wherein sufficient isolation between the receive port and the transmit port is provided. In this arrangement, a low power relay may be used because the relay only switches low level received signals, and the high power transmit signals are switched by the pins.

Antenna switch for transmit-receive operation using relays and diodes

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Penang, Malaysia

Sek Loon Chan