# DspLog some good articles about analog, comm, and DSP

Make it to the Right and Larger Audience

 Authors Krishna SanKar Date 2013 Affiliation dsplog.com About Technical Blogs
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### DspLog some good articles about analog, comm, and DSP

dsplog.com has good short analysis articles (blogs) in wireless communication domain. The following are some examples:

First is named “Image Rejection Ration (IMRR) with transmit IQ gain/phase imbalance”. IQ modulator has gain of α and β on each arm an phase imbalance of Φ.

IMRR is defined as desired signal power over image signal power. For example, if desired signal is $e^{j\omega t}$, then image signal is $e^{-j\omega t}$, which is used in article. After some derivation, IMRR is shown as:

$IMRR = \frac{\gamma^2 +1 -2\gamma\cos{\phi}}{\gamma^2 +1 -2\gamma\cos{\phi}}$

I made a spreadsheet based on this formula and you can easily calculate IMRR with it.

The second is about error vector magnitude (EVM) dut o phase noise and thermal noise.  After some derivation, it shows EVM is

$EVM = \sqrt{\frac{N_0}{E_s} + 2-2e^{-\frac{\phi^2_{rms}}{2}}}$

where $\phi^2_{rms}$ is phase noise variance.  Again, this formula is captured in the xls.

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