How to improve I/Q mismatch ?

In RF design, commonly phase shifting network contribute primarily to I/Q mismatch, using octet phase generation would help in compensenting it.

Rgds

hi hrkhari, can you talk more about octet phase generation or provide reference?
Also I know you can also perform digital pre-distortion, is there any other method other than digital?

Thanks

1/4 λ microtrip line can produce 90-degree phase shift

have you ever try polyphase filter?

y can use the digital technology to overcome the analoge IQ mismatch,

but if y tell me the concrete condition ,i can recommend some device with good IQ match

Hi there
There are 2 types of mismatch:
-amplitude
-phase

If you maintained nice electrical length between I and Q inputs then the main thing to do is adjust amplitude of one channel in respect to the other.
If you need more compensation, the phase needs to be adjusted. In a measuring setup it is easy.... just fool around with some different lenghts of coax in one channel. In a real application this is not possible.
A sort of calibration routine might help to adjust amplitude & phase. This calls for software.

rgds

Mike

The requirement for I/Q mismatch depends on the modulation. The BPSK/QPSK could tolerate more phase/amplitude mismatch than 8 PSK or 16 QAM. Based on your system, I/Q mismatch may be compensated at the baseband using DSP.

Hello,

There is this doc at Tropian on the error sources in an IQ modulator:
http://www.tropian.com/tech/tech_docs/wse00.pdf

It can indicate which are the most important error terms that need to be corrected.

Hi,

Improving I/Q balance- Some issues to consider:
- Good quadrature phase balance (polyphase filter, divide-by-2 or 4)
- Good amplitude balance (limiting in some cases)
- Symmetry in layout critical (use dummies if necessary)
- Calibration if very high performance required by your system

All the best