Group Project in CMOS Bluetooth Transceiver Design
What Actually Happened This Year
In this year, the project was a low IF blue tooth transceiver
in 0.35 micron CMOS. Background research came first in which
the students learned about the CMOS process, principles of low-IF
down conversion, RF and analog design procedures and techniques. Then
students designed their individual blocks, first reviewing what
others (previous students at Carleton and designers elsewhere)
then one or several designs were chosen and detailed design was
done on their individual blocks. As well, attention was paid
to how the blocks would connect to the neighboring blocks.
Students involved and the blocks they worked on are as follows:
Peter Popplewell, power amplifier (PA)
Dalia Sherif: low-noise amplifier (lna)
Nosa Ogbebor: phase detector and charge pump of frequency synthesizer
Kathryn Mills: IF filter stage using transconductance amplifiers
Chris Taylor: synthesizer overview, phase noise analysis
and reduction; divider design
Victor Karam: mixers
Michel Sabourin: voltage-controlled oscillators, poly phase filter
Presentations Done
Part of this group presented their design at Conexant in Ottawa,
and also at the MR&DCan Workshop (Microelectronics Research and
Development in Canada). This presentation is posted next to the
elevator on the fifth floor Mackenzie Building.
Circuit Fabrication
Part of the group had their design fabricated after the term
was over with components coming back in the end of the summer.
Components which were fabricated were the LNA, mixer, oscillator
and power amplifier. The decision to fabricate or not was based
on a number of factors: available fabrication space, the likelihood
of success, the novelty of the design, willingness and availability
to do more work (e.g., completion of layout and testing) after
the term was over.
Information From Before the Term, actually from previous
years
Students will design a radio transceiver in 0.35 micron CMOS.
This will involve a significant amount of time to become familiar
with RF circuits, the CMOS process and the simulation and layout
tools. Students will work as a group, but will also be responsible
for individual parts which make up the transceiver. Parts could
include the low-noise amplifier, image-reject filter, mixer,
oscillator, synthesizer, and power amplifier. If good progress
is made on the radio, or if individual parts look very promising
then actual fabrication through the Canadian Microelectronics
Corporation will be considered towards the end of the school year.
This project assumes a good understanding of background theory
as provided by the third year courses, Electronics II (97.359)
and Communications (94.351). Further theory will be provided by
some of the fourth-year courses.
More Details on Some of the Parts, more to be added later.
1. Radio Frequency Mixer Design
In a radio-frequency front end, the incoming signal at the radio
frequency (RF) is converted to the intermdediate frequency (IF)
by mixing with a local oscillator (LO) signal. Thus the mixer
inputs are the RF and LO signals and the output is the IF signal.
Typically, many RF signals may exist, but only one is desired.
This means that one of the main concerns in a mixer is linearity
of the RF input to prevent intermodulations between various input
signals. Other issues of importance are frequency response, power
dissipation and noise.
This project will begin with a study of different types of mixers.
The study will involve simulation with a combination of HPEESOF
and SPICE to evaluate the linearity, and other specifications
of the different structures. Then a particular design will be
chosen for detailed analysis and design, followed by implementation
and test.
2. Radio Frequency Oscillator Design
Oscillators are used in several ways in Radio Frequency circuits,
for example as an input to a mixer which converts from the radio
frequency to the intermediate frequency. Usually, the oscillator
frequency is adjustable (Voltage-Controlled Oscillator or VCO) and
used inside of a frequency synthesizer. One of the biggest concerns
in oscillators is noise components which can cause the wrong
frequencies to be mixed down to the intermediate stage.
This project will begin with a study of the background material
and of possible oscillator topologies. This will be followed
by simulation, probably with HPEESOF, to determine which type
of oscillator results in the lowest noise. Then, a particular
topology would be chosen for more detailed study of the design
tradeoffs, followed by implementation and test.
3. Radio Frequency Power Amplifier Design
Power amplifiers are used to drive the antenna on the transmit
side. Difficulties in design are achieving high enough power
while using a battery as a power supply. High efficiency is important
in order to maximize life of the battery. Different classes of
amplifiers (from class A through class F) can be chosen with
different tradeoffs between efficiency, linearity and simplicity
of design.
This project will begin with a study of the different classes
and types of power amplifiers. This will be followed by simulation,
probably with HPEESOF, to determine which type of amplfier results
in the highest efficiency and what the tradeoffs are. Then, a
particular design, or combination of designs will be chosen
for detailed analyis and design, followed by implementation and
test.
4. Radio Frequency LNA Design
The LNA provides amplification close to the input without adding
too much noise. This means that noise added by later stages is
of less importance. Thus the main issue is noise. Other things
are also ofconcern. For example, the input impedance must be
matched to the antenna. Linearity must be sufficiently high to
avoid overloading in the presence of high amplitude blocking
signals, while still receiving potentially low amplitude wanted
signals. Other important design considerations are power dissipation,
layout area etc.
This project will begin with a study of different types of LNAs.
The study will involve simulation with a combination of HPEESOF
and SPICE to evaluate the noise, linearity, and other specifications
of the different structures. Then a particular design will be
chosen for detailed analysis and design, followed by implementation
and test.
4. Synthesizer Design
In a radio communication system, one can typically communicate
on one of many channels. In a radio front end, the synthesizer
is sets the local oscillator frequency to tune in the desired
channel. Thus the synthesizer contains a voltage-controlled oscillator
(which is a project of its own) but also adds the control circuitry
to set the frequency and to allow selection of frequency. Synthesizers
can be based on phase-locked loops, of which there are several
variants, or can be direct digital (where the equivalent of sine
waves are stored in memory and read out at an appropriate rate
to produce the desired signal). Issues in synthesizers are switching
speed, resolution, tuning range, etc.
This project will begin with a study of different types of LNAs.
The study will involve simulation with a combination of HPEESOF
and SPICE to evaluate the noise, linearity, and other specifications
of the different structures. Then a particular design will be
chosen for detailed analysis and design, followed by implementation
and test.
Courses most strongly related to the project
97.359 For transistor level circuit Design, while 97.359 deals
more with bipolar transistors, the project will emphasize
MOS transistors, specifically CMOS. However, the ideas
and techniques are very similar. As well, 97.359 includes
discussions about amplifiers, stability, oscillators,
and filters, all of which will be part of the project.
94.351, Communications theory - The project is about building
a radio for a communications system. This course tends
to be block level, while the project will get into actual
circuit details.
97.469 Integrated circuit layout is covered and will be used
for the project.
97.455 Telecommunications circuits which covers many of the blocks
used, e.g., low noise amplifiers, mixers, oscillators,
synthesizers, and detectors.
97.477 Analog integrated circuits using CMOS are related to the
design in the project.