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 Introduction to RFIC receiver architecture 2 / 25

Terminology Receiver Architecture

Local Oscillator(LO)

•

converting a signal

(by wikipedia) of interest

to a different frequency

using a mixer • •

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.

Introduction to RFIC receiver architecture 4 / 25

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

𝐹 𝑅𝐸𝐶𝐸𝐼𝑉𝐸𝑅 = 𝐹 𝐿𝑁𝐴 + 𝐹 𝑀𝐼𝑋𝐸𝑅 −1 𝐺 𝐿𝑁𝐴 + 𝐹 3 −1 𝐺 𝐿𝑁𝐴 𝐺 𝑀𝐼𝑋𝐸𝑅 + 𝐹 4 −1 𝐺 𝐿𝑁𝐴 𝐺 𝑀𝐼𝑋𝐸𝑅 𝐺 3 +… Introduction to RFIC receiver architecture 5 / 25

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

Introduction to RFIC receiver architecture 6 / 25

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

and 38.9 MHz. for visual signal. using system B and similar systems: 33.4 MHz. for aural

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 Introduction to RFIC receiver architecture 7 / 25

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) Introduction to RFIC receiver architecture 9 / 25

Heterodyne receiver

• exploits high quality filters to provide desired performance 1 st filter : duplex filter 2 nd filter : image rejection filter Introduction to RFIC receiver architecture 10 / 25

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!

Introduction to RFIC receiver architecture 11 / 25

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.

Introduction to RFIC receiver architecture 12 / 25

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 13 / 25

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 Introduction to RFIC receiver architecture 14 / 25

Direct-conversion

Direct-conversion receiver architecture Introduction to RFIC receiver architecture 15 / 25

Direct conversion

Introduction to RFIC receiver architecture 16 / 25

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 Introduction to RFIC receiver architecture 17 / 25

Low-IF

Low-IF receiver architecture Introduction to RFIC receiver architecture 18 / 25

Low-IF

Introduction to RFIC receiver architecture 19 / 25

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 Introduction to RFIC receiver architecture 20 / 25

Quasi-IF

Quasi-IF receiver architecture Introduction to RFIC receiver architecture 21 / 25

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

Introduction to RFIC receiver architecture 22 / 25

Comparison

Selectivity Analog Requirements Flexibility CMOS Compatibility Noise Dynamic Range

Heterodyne

Low High Low Low Low High

Direct conversion

High Moderate Low Moderate Moderate High Comparison of various receiver architecture key parameters

Low-IF

High Low High High Low High Introduction to RFIC receiver architecture 23 / 25

Comparison

Direct conversion • • • •

Advantages

No IF filters(2 LPFs) No image Low power consumption Easy integration Low-IF Quasi-IF • • • • • • • • Low freq. low Q BPF No LO leakage No DC offset Easy integration No IF filters(2 LPFs) No LO leak Low phase noise Easy integration • • • • • • • • • •

Difficulties

LO leakage DC offset due to device mismatch 1/f noise High linearity mixer Image rejection Path matching Increased hardware than direct-conv.

Image rejection Path matching Increased hardware than direct-conv.

Introduction to RFIC receiver architecture 24 / 25

Thank you.