SINGLE DIODE MIXER WITH RF TO IF PORT ISOLATION
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-12
Field testing of cellular phone base stations can require the use of a loopback circuit. This circuit couples a known transmitter output signal into a mixer that mixes the transmitter signal down to the receive band. This mixed down or looped back sig- nal is attenuated and injected into the receiver front end. There it is received, demodulated and com- pared with the known transmitted signal to deter- mine transceiver functionality. This can include received signal strength, and bit error rate measure- ments. All this can be done without interrupting ser- vice while the transceiver is still in the field. The RF (Radio Frequency) mixer required for a loop- back circuit has unique design requirements. This led to the development of a low cost single diode mixer that requires low LO (Local Oscillator) drive, and offers good RF to IF (Intermediate Frequency) isolation.