RF loopback test apparatus for data radio transceiver

• US 20030068989A1
• Filed: 10/05/2001
• Published: 04/10/2003
• Est. Priority Date: 10/05/2001
• Status: Active Grant

• Current Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Original Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Inventors: Harris, Joseph L., Nelson, David Paul
• Granted Patent: US 6,965,756 B2
• Time in Patent Office: Days
• US Class Current: 455/115.1
• CPC Class Codes: H04B 17/15 Performance testing
• CPC Class Codes: H04B 17/17 Detection of non-compliance or faulty performance, e.g. response deviations H04B17/18 takes precedence
• CPC Class Codes: H04B 17/18 Monitoring during normal operation
• CPC Class Codes: H04B 17/19 Self-testing arrangements
• CPC Class Codes: H04B 17/20 of receivers
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements

Abstract

An RF loopback test circuit is adapted to be coupled to an antenna port of a digital radio, to determine whether the radio is functioning properly. A frequency generator outputs an auxiliary frequency corresponding to the sum or difference between the radio'"'"'s transmit and receive frequencies. The auxiliary frequency is coupled to a Schottky diode mixer, which is also coupled to the input/output port. If the radio'"'"'s transceiver section is operating properly, the sum or difference frequency output of the Schottky diode mixer will be passed by only the diplexer'"'"'s narrowband receive path filter to the radio'"'"'s receiver section. The mixer'"'"'s sum frequency is blocked by the diplexer'"'"'s narrowband filters. Therefore, if the receiver section provides an indication that it is receiving a sufficient signal level from the RF loopback test circuit, it can also be inferred that each of the transmitter and receiver sections is operating properly.

Claims

1. A method of testing the operability of a communication apparatus having a transmitter section that is adapted to output a communication signal at a first frequency for application to a diplexer and transmission to another communication device, and a receiver section that is coupled to said diplexer and is adapted to receive a communication signal from said another communication device at a second frequency, different from said first frequency, said method comprising the steps of:

(a) providing an auxiliary communication device having a frequency generator that is operative to generate an auxiliary frequency signal having a frequency on the order of the sum or difference between said first and second frequencies, and a frequency combiner, coupled to said frequency generator and to an input/output terminal of said auxiliary communication device, and being operative to combine said auxiliary frequency signal with an external signal coupled to said input/output terminal and to produce at said input/output terminal an output frequency corresponding to the sum or difference between said auxiliary frequency and the frequency of said external signal; and

(b) coupling said input/output terminal of said auxiliary communication device to said diplexer, and monitoring said receiver section of said communication apparatus for said second frequency.

2. The method according to claim 1, wherein said frequency combiner includes a Schottky diode mixer and an attenuator network coupled between said frequency generator and said input/output terminal.

3. A test architecture for testing the operability of a transceiver that is adapted to transmit on a first communication frequency and to receive on a second communication frequency, and being coupled to a diplexer having an interface port that is adapted to interface wireless communication energy with a telecommunication channel, a first transceiver-coupling port adapted to be coupled with a transmission channel port of said radio transceiver, and a second transceiver port adapted to be coupled with a receive transmission channel port of said radio transceiver, said diplexer further including a transmission filter which is operative to pass signals having said first communication frequency and being coupled between said interface port and said first transceiver port, and a receive filter which is operative to pass signals having said communication frequency, and being coupled between said interface port and said second transceiver port, said test architecture comprising:

a frequency generator that is operative to generate an auxiliary frequency signal having a frequency on the order of the sum or difference between said first and second communication frequencies; and

a frequency combiner, coupled to said frequency generator and to an input/output terminal, and being operative to combine said auxiliary frequency signal with an external signal coupled to said input/output terminal and to produce at said input/output terminal an output sum or difference frequency corresponding to the sum or difference between said auxiliary frequency and the frequency of said external signal; and

wherein

said input/output terminal is adapted to be coupled to said interface port of said diplexer, so that the output of said receiver section may be monitor for the presence of said second communication frequency.

4. The test architecture according to claim 3, wherein said frequency combiner includes a Schottky diode mixer and an attenuator network coupled between said frequency generator and said input/output terminal.

5. An RF loopback test circuit comprising:

an input/output port that is adapted to be coupled to a transmit-receive communication port of a diplexer of a wireless communication device;

a frequency generator that is operative to output an auxiliary frequency corresponding to the difference or sum between transmit and receive frequencies of said wireless communication device;

a mixer coupled to said input/output port and to said frequency generator, and being operative, in response to receiving said transmit frequency, to produce said receive frequency as an RF loopback output at said input/output port, so that, for proper operation of said wireless communication device, said receive frequency produced at said input/output port will be passed by a narrowband receive path filter of said diplexer and coupled thereby to a receiver section of said wireless communication device.

6. The RF loopback test circuit according to claim 5, wherein said mixer comprises a Schottky diode mixer and an attenuator network coupled between said frequency generator and said input/output terminal.