5探测器电路

In this example, a Schottky detector diode is used to measure the RF signal being received at the antenna of the radio. The diode used in this design is a Skyworks SMS3923-079LF. The circuit design is quite basic and could likely be improved upon. RF is rectified across the junction of the diode. Any remaining RF on the anode side of the diode is shunted to ground by the 120 pF capacitor. Any DC appearing on the cathode side of the diode will be shorted to ground by the 560 nH inductor. Resistor R3 in the schematic was not used in this example. The circuit as designed outputs about 110 mV DC with approximately 0 dB input. A picture of a crude implementation is shown in Figure 2.

Figure 2: Crude Implementation

The output from this circuit is fed into the RSSI input pin on the GreenPAK IC. When the voltage in the RSSI pin drops sufficiently (50 mV in this example), the GreenPAK will adjust the bias point of the amplifier and increase the power supplied to the amplifier to improve performance. When the received signal is sufficiently strong, the bias point will be reduced thereby saving power.

Improvements made to this circuit could include using forward bias across the diode to improve voltage output. A better and cleaner layout would also result in improved performance. Additionally, an amplifier could be used to increase the level of voltage output.