Introduction to
RFIC receiver architecture
Special Topics in Computers and Circuits
30(Wed), March, 2011
2007144078 Min, Kyungsik
Context
• Terminology
– Local Oscillator (LO)
– Low Noise Amplifier (LNA)
– Intermediate Frequency (IF)
• Receiver Architecture
–
–
–
–
–
Heterodyne
SuperHeterodyne
Direct-Conversion (Zero-IF)
Low-IF
Quasi-IF
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Terminology
Receiver Architecture
Local Oscillator(LO)
•
converting a signal of interest to a different frequency using a mixer
(by wikipedia)
•
•
Heterodyning : process of conversion
produces the sum and difference frequencies of the frequency of the local
oscillator and frequency of the input signal of interest.
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LNA
•
first amplifier in the receiver,
right after the antenna and the
duplex filter
•
To boost the received signal out from
the noise and reduce the
noise interference
•
The gain of the LNA helps to suppress
the noise of the subsequent blocks
in the receiver.

Frii’s Equation
𝐹𝑅𝐸𝐶𝐸𝐼𝑉𝐸𝑅 = 𝐹𝐿𝑁𝐴 +
𝐹𝑀𝐼𝑋𝐸𝑅 −1
𝐺𝐿𝑁𝐴
+
𝐹3 −1
𝐹4 −1
+
+…
𝐺𝐿𝑁𝐴 𝐺𝑀𝐼𝑋𝐸𝑅 𝐺𝐿𝑁𝐴 𝐺𝑀𝐼𝑋𝐸𝑅 𝐺3
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Intermediate Frequency(IF)
Definition
•
a frequency to which a carrier frequency is shifted as an intermediate step in
transmission or reception
Created by mixing the carrier signal with a local oscillator signal
•
Used in superheterodying radio receivers
•
Merits
•
can be used in many devices
•
To convert the various different frequencies of the stations
•
Improve frequency selectivity
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Intermediate Frequency(IF)
•
Television receivers: 30 MHz to 900 MHz
•
Analogue television receivers using system M: 41.25 MHz (audio) and 45.75 MHz
(video). Note, the channel is flipped over in the conversion process in an intercarrier
system, so the audio IF frequency is lower than the video IF frequency.
•
Analogue television receivers using system B and similar systems: 33.4 MHz. for aural
and 38.9 MHz. for visual signal.
•
FM radio receivers: 262 kHz, 455 kHz, 1.6 MHz, 5.5 MHz, 10.7 MHz, 10.8 MHz,
11.2 MHz, 11.7 MHz, 11.8 MHz, 21.4 MHz, 75 MHz and 98 MHz.
•
AM radio receivers: 450 kHz, 455 kHz, 460 kHz, 465 kHz, 470 kHz, 475 kHz, 480 kHz
•
Satellite uplink-downlink equipment: 70 MHz, 950-1450 Downlink first IF
•
Terrestrial microwave equipment: 250 MHz, 70 MHz or 75 MHz
•
Radar: 30 MHz
•
RF Test Equipment: 310.7 MHz, 160 MHz, 21.4 MHz
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Terminology
Receiver Architecture
Heterodyne receiver
• Traditional heterodyne receiver architecture based on the parallel data
detector concept
• the original radio receiver design
• introduced in 1901 by Reginald Fessenden (Canadian inventor-engineer)
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Heterodyne receiver
•
exploits high quality filters to provide desired performance
1st filter
: duplex filter
Introduction to RFIC receiver architecture
2nd filter
: image rejection filter
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Heterodyne receiver
Problem #1 : It is very difficult to tune an amplifier and/or filter!
•
We can change the frequency response of an amplifier/filter by changing the
values of the reactive components(i.e., inductors and capacitors).
•
But the center frequency and bandwidth of an amplifier/filter are related to the
inductor and capacitor values in very indirect and complex ways.
•
Additionally, a filter of high selectivity(i.e., “fast roll-off”) will be a filter of high
order -> high order means many inductors and capacitors!
Result : Tuning a good heterodyne receiver can be very difficult, requiring a precise
adjustment of many control knobs!
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Heterodyne receiver
Problem #2 : The signal reaching the detector can be any one of many
frequencies(e.g., w1, w2, w3, w4) distributed across a very wide bandwidth.
As a result, the detector must be wideband!
Unfortunately, a good wideband detector/ demodulator is difficult to build. Generally
speaking, a detector/demodulator will work well at some frequencies, but less well at
others.
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Superheterodyne receiver
•
superheterodyne : creating a beat frequency that is lower than the original signal
•
to purposely mix in another frequency in the receiver, so as to reduce the signal
frequency prior to processing
Incoming signal, centered at
the carrier frequency
Introduction to RFIC receiver architecture
Intermediate frequency signal,
at constant frequency, IF
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Superheterodyne receiver
• Advantages of using Superheterodying (receiver)
– Reduces the signal from very high frequency sources where ordinary
components wouldn’t work(like in a radar receiver)
– Devices can be optimized or made more inexpensively
– Can be used to improve signal isolation by arithmetic selectivity
• Difficulty
– Hard to treat high quality of digital signal
– Duplication of original signal and image signal
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Direct-conversion
Direct-conversion receiver architecture
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Direct conversion
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Direct conversion
•
Amplification and filtering : performed at baseband
– Low current drain in amplifiers and active filters
– No task of image-rejection
•
Wide tuning and high selectivity
•
•
•
Two high frequency conversion stages in parallel
LO frequency deviation
Spurious LO leakage
•
DC offset connected to direct-conversion
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Low-IF
Low-IF receiver architecture
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Low-IF
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Low-IF
•
Analog implementation : hard to provided superior performance and a degree of
flexibility
→ downconversion of information signal to a low-IF frequency
•
no duplication of desired signal with image frequency
•
power consumption
•
Use of I/Q-demodulation
•
I/Q demodulation providing for 20-40 dB’s of image rejection
→ a less selective filter
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Quasi-IF
Quasi-IF receiver architecture
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Quasi-IF
•
Combining a non-tunable I/Q down-conversion mixer and a tunable image
rejection mixer for down-conversion to baseband and channel selection
Advantages
• first LO : optimized with respect to phase noise as no switching requirements are
now present
•
Tunable second LO : operates at low frequencies whereby phase noise and
undesired non-linearities may be minimized
•
absence of IF filter
Disadvantages
• DC offset
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Comparison
Heterodyne
Directconversion
Low-IF
Selectivity
Low
High
High
Analog
Requirements
High
Moderate
Low
Flexibility
Low
Low
High
CMOS
Compatibility
Low
Moderate
High
Noise
Low
Moderate
Low
Dynamic Range
High
High
High
Comparison of various receiver architecture key parameters
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Comparison
Advantages
Difficulties
Directconversion
•
•
•
•
No IF filters(2 LPFs)
No image
Low power consumption
Easy integration
• LO leakage
• DC offset due to device
mismatch
• 1/f noise
• High linearity mixer
Low-IF
•
•
•
•
Low freq. low Q BPF
No LO leakage
No DC offset
Easy integration
• Image rejection
• Path matching
• Increased hardware than
direct-conv.
Quasi-IF
•
•
•
•
No IF filters(2 LPFs)
No LO leak
Low phase noise
Easy integration
• Image rejection
• Path matching
• Increased hardware than
direct-conv.
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Thank you.