III. Gm-C Filtering - Epublications - Université de Limoges
III. Gm-C Filtering - Epublications - Université de Limoges
III. Gm-C Filtering - Epublications - Université de Limoges
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
II.3 Towards a Fair Figure-of-Merit<br />
II.3.a Required Parameters to Handle a Fair Comparison<br />
To be able to compare the performances of the various structures of RF filters (passive<br />
LC, Gyrator-C, <strong>Gm</strong>-C, n-path filters or else) that may be found in the literature, a common<br />
reference figure is nee<strong>de</strong>d. This figure, called figure-of-merit (FOM), should take into account<br />
all parameters related to the specifications discussed in introduction, which are:<br />
- RF dynamic range: linearity and noise;<br />
- Frequency tuning range;<br />
- Selectivity: quality factor, harmonics and adjacent channels rejections;<br />
- Maximum working frequency.<br />
Some other aspects might as well be taken into account, such as the process<br />
variations, the gain at the central frequency or even the area occupied by the circuit.<br />
II.3.b Study of the Figures-of-Merit Found in the Literature<br />
Let’s have a look at some FOMs found in the literature. In [II.5], K. Kwon et al, a<br />
FOM for linear and low-noise low-pass filters is presented. Their FOM is the following:<br />
OIP3.<br />
f max . TR.<br />
N<br />
FOM = (II.29)<br />
( F −1)<br />
Pdc<br />
where F is the noise factor, Pdc/N is the power consumption per pole and TR is the frequency<br />
tuning range.<br />
The quality factor of the filter, for a band-pass, is an important parameter to consi<strong>de</strong>r<br />
and is not taken into account in this FOM. Although too high power consumption would be an<br />
issue, it is not a primary specification since TV is not a portable application. Input parameters<br />
would also be preferred because of their in<strong>de</strong>pen<strong>de</strong>nce of the filter gain.<br />
Another FOM is introduced in [II.6]. After having <strong>de</strong>scribed a passive band-pass filter,<br />
F. Dülger et al. have introduced the following figure-of-merit, which is taken in dB:<br />
N.<br />
SFDR.<br />
f 0.<br />
Q<br />
FOM dB = (II.30)<br />
Pdc<br />
where Pdc/N is still the power consumption by pole, SFDR is the Spurious Free Dynamic<br />
Range.<br />
However, this FOM does not take into account the frequency tunability. There is<br />
reference neither to linearity nor to noise in this figure, which makes this FOM not suitable<br />
for the previously <strong>de</strong>scribed purposes.<br />
- 56 -