This show talks about noise in RF circuits.

1. RF MicroelectronicsLECTURE -2 : NOISE
BY: AHMED SAKR.
AHMEDSAKR01@GMAIL.COM
SUPERVISED BY:
PROF. HESHAM HAMED
DR. MAHMOUD A. ABDELGHANY.

2. Introduction
Performance limitations
The two main performance
limitations in RF design are noise and
nonlinearity.
Noise is RANDOM, which means that
the instantaneous value of noise can
not be predicted.
Noise is expressed in term of its
average power Pn.

3. Device Noise
Thermal noise of resistors
Resistors noise is modeled by an ideal resistance
in series with voltage source with Vn
2 or in parallel with
a current source of In
2.
model should be chosen to simplify calculations.
The polarity of the sources is unimportant but should
be same throughout the entire calculations.

4. Device Noise
Noise of MOSFETs
Thermal, flicker.
γ is the Excess noise coefficient. 2/3 for
long channel MOS, >= 2 for short channel
MOSs.
Thermal noise may be modeled by series
voltage source with the gate or parallel
current source between the drain and source.
flicker noise 1/f.

5. Device Noise
Noise of MOSFETs
Thermal, flicker.
Flicker noise 1/f. modeled by a
voltage source in series with the gate.
The choice of the lower frequency
of the system should be larger than the
Corner frequency fc.
flicker noise+ nonlinearity+ (time-
variance) = translation of flicker noise
into the band of interest [Mixers, OSC]
(*)K is a process-
dependent constant

6. Representation of noise in circuits.
Input-referred noise
Noise is modeled by series voltage source & parallel current source.
To calculate Vn
2 we short the input port and measure output noise,
To calculate In
2 we do the same with input port opened.

7. Representation of noise in circuits.
Noise figure
SNR (signal-to-noise ratio) =
𝑃 𝑠𝑖𝑔𝑛𝑎𝑙
𝑃 𝑛𝑜𝑖𝑠𝑒
NF describes the added noise from the
circuit into the signal.

8. Sensitivity & dynamic range
Sensitivity is the minimum signal level that a
receiver can detect with acceptable quality.
Noise floor
The total integrated noise of the system
Dynamic range :
𝑡ℎ𝑒 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑖𝑛𝑝𝑢𝑡 𝑙𝑒𝑣𝑒𝑙 𝑎 𝑟𝑒𝑐𝑒𝑖𝑣𝑒𝑟 𝑐𝑎𝑛 𝑡𝑜𝑙𝑜𝑟𝑎𝑡𝑒
𝑡ℎ𝑒 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑖𝑛𝑝𝑢𝑡 𝑙𝑒𝑣𝑒𝑙 𝑖𝑡 𝑐𝑎𝑛 𝑑𝑒𝑡𝑒𝑐𝑡 (𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦)

9. Sensitivity & dynamic range
Dynamic range:
𝑡ℎ𝑒 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑖𝑛𝑝𝑢𝑡 𝑙𝑒𝑣𝑒𝑙 𝑎 𝑟𝑒𝑐𝑒𝑖𝑣𝑒𝑟 𝑐𝑎𝑛 𝑡𝑜𝑙𝑜𝑟𝑎𝑡𝑒
𝑡ℎ𝑒 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑖𝑛𝑝𝑢𝑡 𝑙𝑒𝑣𝑒𝑙 𝑖𝑡 𝑐𝑎𝑛 𝑑𝑒𝑡𝑒𝑐𝑡 (𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦)
SFDR (spurious-free dynamic range):
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑖𝑛𝑝𝑢𝑡 𝑙𝑒𝑣𝑒𝑙 𝑖𝑛 𝑡𝑤𝑜−𝑡𝑜𝑛𝑒 𝑡𝑒𝑠𝑡 𝑤𝑖𝑡ℎ 𝐈𝐌 𝐥𝐞𝐯𝐞𝐥≤𝐧𝐨𝐢𝐬𝐞 𝐟𝐥𝐨𝐨𝐫
(𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦)

10. Impedance transformation
Quality Factor
Quality factor Q indicates how close to ideal an energy-storing
device (Inductor, Capacitor) is.

11. Impedance transformation
Parallel to series conversion
Quality factor Q indicates how close to ideal an energy-storing
device (Inductor, Capacitor) is.
For Q2>>1 (true for a finite frequency range)

12. Impedance transformation
L sections used for matching
Sometimes the load resistance is needed to become larger or
smaller, that can be achieved by matching networks as following

13. Scattering parameters.

14. Scattering parameters.
Input matching
Reverse gain
Output matching
Gain

15. Any Questions?