Self calibration apparatus and methods

1. A method of calibrating an instrument, the method comprising:

for an instrument having N ports, where N>=2,

characterizing cables having a first type including,

connecting a first cable between two of the N ports,

performing an “unknown-thru” full two-port calibration between the two ports,

obtaining a S-parameter of the first cable,

saving the S-parameter of the first cable in an internal dedicated user memory, and

repeating connecting, performing, obtaining and saving for additional cables having the first type;

disconnecting the cables having the first type from one of the two ports and transferring a measurement plane from the connected end of the cable to the disconnected end of the cable; and

characterizing cables having a second type including,

connecting a second cable between the second of the two ports and the disconnected end of the first cable,

measuring a S-parameter of the second cable, and

saving the S-parameter of the second cable in the internal dedicated user memory.

2. A method as defined in claim 1 , wherein the characterized cables are used to calibrate the remaining N-2 ports having a matable connector to the first or second cable, using the Short-Open-Load-Thru (SOLT) method.

3. A method as defined in claim 1 , the instrument including:

a signal source;

a switch, connecting to the signal source and operable to connect to each of the N ports;

each of the N ports connecting to a block that includes,

a dual reflectometer having an input sensing arm connected to a reference receiver and an output sensing arm connected to a test receiver,

a three terminal switch, having a first terminal connected to a reflectometer, a second terminal connected to a multi-state impedance module, and a third terminal connected to a test port connector.

4. A method as defined in claim 1 , comprising correcting mismatch power measurements using power calibrated receivers and characterized cables and adapters.

5. A method of calibrating comprising:

for an instrument having N ports, where N>=2 and the instrument includes,

a signal source; and

a source switch connecting to the signal source and operable to connect to each of the N ports;

each of the N ports connecting to a block that includes,

a power splitter, connected to the signal source, having a first splitter output connected to a reference channel receiver; and

a second splitter output of the power splitter connected to the common pole of a single pole, N throw switch, each throw connected to a block including,

a single reflectometer having input port connected to the source switch and an output arm connected to a test receiver,

a three position switch, connected to the output port of the single reflectometer, connected to the test port connector,

a multi state impedance module connected to the three position switch;

connecting a cable of a characterized type between a first port and a second port with the signal source connected to the first port and the multi-state impedance module connected to the second port;

performing a 1-port calibration at an end of the cable using the multi-state impedance connected to the second port;

switching the second port to connection with the reflectometer instead of the multi-state impedance module; and

measuring a thru connection to complete a 2-port calibration.

6. A method as in claim 5 , when the multi-state impedance module is electrically connected to the test port connector, it is used for calibrating another port.

7. A method as in claim 5 , when the multi-state impedance module is electrically connected to the test port connector, it is used as variable impedance termination for a device under test.

8. A method as defined in claim 5 , comprising correcting mismatch power measurements using power calibrated receivers and characterized cables and adapters.

9. An instrument having N ports, where N>=2, comprising:

a signal source; and

a single pole, double throw switch, having a common pole connected to a second splitter output, each throw connected to a block including,

a three terminal switch, having a first terminal connected to a reflectometer, a second terminal connected to a multi-state impedance module, and a third terminal connected to a test port connector,

wherein the reflectometer is selected from a group including single and dual reflectometers.

10. An instrument as defined in claim 9 , wherein the reflectometer is a single reflectometer, further including a power splitter, connected to the signal source, having a first splitter output connected to a reference channel receiver.

11. An instrument as in claim 9 , when the multi-state impedance module is electrically connected to the test port connector, it is used for calibrating another port.

12. An instrument as in claim 9 , when the multi-state impedance module is electrically connected to the test port connector, it is used as variable impedance termination for a device under test.