Circuit and method for testing RF device and RF device with built-in testing circuit

An RF device, comprising:

• an RF circuit for transmitting or receiving an RF signal;
• a testing circuit performing a testing operation to detect an RF circuit characteristic of the RF device, comprising:
• a first filter unit having a first external terminal electrically coupled to a testing signal and a second external terminal electrically coupled to the RF circuit, wherein the first filter unit is configured to allow the testing signal to enter the RF circuit while blocking an RF signal transmitted in the RF circuit from entering the testing circuit the first filter unit is configured to allow bidirectional transmitting of the testing signal, and a frequency of the testing signal is different from a frequency of the RF signal;
• and
• a testing-result informing unit having an external input electrically coupled to the first external terminal, and generating an informing signal, which indicates the RF circuit characteristic according to an electric level at the external input.

A testing method for determining an RF circuit characteristic of an RF device, executed by a testing circuit built in the RF device and electrically coupled to an RF circuit of the RF device, the testing method comprising:

• electrically coupling a testing circuit to the RF circuit in the RF device;
• receiving a testing signal;
• transmitting the testing signal through both the testing circuit and the RF circuit while blocking an RF signal transmitted in the RF circuit from entering the testing circuit, wherein the testing signal is allowed to be transmitted from the testing circuit to the RF circuit and from the RF circuit to the testing circuit, and a frequency of the testing signal is different from a frequency of the RF signal;
• generating an informing signal in response to the testing signal transmitted through the testing circuit and the RF circuit;
• comparing the informing signal with a default signal to obtain a comparison result;
• and
• determining the RF circuit characteristic according to the comparison result.