III. Gm-C Filtering - Epublications - Université de Limoges

V.3 State-of-the-Art
V.3.a 4-path Filtering State-of-the-Art
References [V.3 and V.5] report measurement results of very high RF performances
using the structure in Figure 185, with NF below 5dB with IIP3 higher than 14dBm, for a Q
factor between 3 and 29. However, due to aliasing, maximum rejection is limited to 15dB.
The results in this paper are summarized in Table 31. It is worth highlighting that an external
balun is used for the single to differential conversion. In this table, the maximum rejection is
defined by the difference between the gain at fclk and the gain between two folding
frequencies.
Table 31. Sum-up of 4-path filter performances
- 167 -
[V.5] Units
f0 Tuning Range 100 – 1000 MHz
Q-factor 3 to 29 (BW=35MHz) -
Filter Gain at f0 -2 dB
Maximum rejection 15 dB
NF 3 to 5 dB
In-band IIP3 14 to 21 dBm
P1dB 2 dBm
Consumption 2 to 16 mW
Active area 0.07 mm 2
Technology 65nm CMOS -
V.3.b An Innovative Fully-integrated Architecture
As explained in these papers, “most integrated receivers nowadays are zero or low-IF
(Figure 192.a), and benefit from a simple structure and a high level of integration as image
rejection is not a major concern, and channel selection is performed by low-frequency lowpass
filters”. However, these filters consist of RC networks which do not scale with the
technology. Besides “constraints such as 1/f noise or second order non-linearity demand large
device sizes for the IF blocks, exacerbating the scalability issue” [V.7]. A superheterodyne
architecture does not experience these issues since it uses IF but it requires external filters for
image rejection and channel selection, as illustrated in Figure 192.b.
To circumvent the scalability issue of zero or low-IF architectures and to achieve the
same level of integration, references [V.6] and [V.7] propose an architecture with a high IF
(110MHz), similar to a superheterodyne receiver, where image and blockers are progressively
filtered throughout the receiver chain by means of frequency-translated filters derived from
the original N-path filtering concept. This may be observed in Figure 192.c.