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Super-Regenerative Receiver

Ultra low-power RF Transceiver forhigh input power & low-data rateapplications

ECEN 665 TAMU AMSC

Thanks to this material to Felix Fernandez

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Overview

{ Invented by Armstrong in 1922 and widely used in

vacuum tube circuits until the 1950s{ It was replaced by the super-heterodyne receiver due

to its poor selectivity and sensitivity

{ Pros:z Small number of components allow for high integration

z Low power

z High energy efficiency

{ Consz poor sensitivity

z poor selectivity

z low data-rate

z limited demodulation capability

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Super-regenerative Receiver

Block Diagram

Selective

Network

Ka(t)

Quench

Oscillator

LNAEnvelope

DetectorLPF

Demodulator

Super-regenrativeOscillator

0

QU

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Super-regenerative Receiver

Block Diagram & Basic Model

( )tALV

dtdVG

dtVdC cos2

2

=++ ( ) ( ) ( )

( ) ( )tG

Ate

G

A

GtAe

GjAe

GjAV

dC

Gt

d

tj

d

tj

d

dd

020

000

sinsin

sin22

+=

+=

+

220

2

21

2

=

=

=

CG

LC

C

G

d

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WWII German Air Interception(first generation SRR, circa 1940)

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Operation Fundamentals

Ga(t) = G0

Ga(t) = 0 [Ga(t) is a negative conductance]

Ga(t) >> G0

Pole-Zero Map

Real Axis

ImaginaryAxis

-8000 -6000 -4000 -2000 0 2000 4000-8

-6

-4

-2

0

2

4

6

8x 10

4

Bode Diagram

Frequency (rad/sec)10

410

510

6-40

-20

0

20

40

60

80

100

120

140From: Input Point To: Output Point

Magnitude(dB)

stable

operation

close

to

unstab

le

(high

Q)

unstable

operat

ion

( )v(t)i(t)tG =

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Operation Modes

z Linear: The self

sustained oscillationsare quenched beforethey reach theirmaximum amplitude.The height of the SRO

output has a linearrelationship with the RFinput power.

z Logarithmic: The self

sustained oscillationsare allowed to reachtheir maximumamplitude. The areaenclosed by the

envelope of the SROoutput has a logarithmicrelationship with the RFinput power

vsro

(t)

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Quenching Mode

{ External Quenching:

z The oscillations of theSRO are quenched byan external oscillatorthat controls the

negative admittanceat a fixed frequency

{ Self Quenching

z The oscillation of theSRO are controlled bya feedback networkwhich quenches the

oscillation after theyhave reached acertain threshold

Low RF Input High RF Input Low RF Input High RF Input

0 1 0 1

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Building Blocks Operation

{ LNA

z Feeds the RF input to the SROz Provides antenna matchingz Isolates SRO oscillations from the antenna

{ SROz Generate the oscillations needed for the super-

regenerative operation{ Quench Oscillator

z Quench the SRO oscillations according to thequenching mode

{ Demodulatorz Detect the SRO oscillation envelope and digitize the

signal

{ Tuning (PLL)z Provide tuning ability to the selective network

(original tuning scheme was manual tuning)

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Super Regenerative System

Design Equations

( )

( )

( )

( )( )

=

=

=

t

t

bt

bt

dtt

dtt

dtt

s

ets

etp

eK

0

0

0

0

0

Super regenerative gain

Output pulse shape

Sensitivity function

Frequency response is given by the Fourier transform of theRF envelope and the sensitivity function.

ttQ

O

e)(2

(t)

AVG

ta tbt

ta tbt

s(t)1

p(t)

i(t)

G0 -Ga(t) L Ci(t)

{ })()( tstiF

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Selective Network Design Equations

( )2

000

2

000

2

2

++=

ss

sKsG

( ) ( )( ) aKsGsGsH

+= 1

: depends on the

quench control signal

( ) ( )( )tKKt a00 1=

( ) )(21

ttQ =

K0: maximum amplificationKa(t): variable gain controlled by quench signal

0: quiescent damping factorAVG: damping factor average value ( ) attaa tKK ==

*

( ) ( ) 20*

000

2

000

12

2

++= sKKs

s

KsHa

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Quench signal frequency limitations

{ Avoid resonance fromprevious cycles(a.k.a. hangover)

{ The hangovercoefficient is therelationship betweenthe amplitudes of the

first cycle and thesecond (unwanted)one.

QUAVGeh

02

=

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Examples

{ Setup

z FRF= 10kHz

z FINT=10.5kHz

z FQUENCH=100Hzz Q = 5

z LPF: 3RD order Butterworth with f3dB 800Hz

z Several quench signals

{ System was simulated using MatLabsSimulink.

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Sine Quench

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Sawtooth Quench

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-0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5Frequency Response for Different Damping Functions

Nomralizad Frequency

NormalizedMagnitude

SAWTOOTHSINE

SAWTOOTH 2

Different Damping Functions (t)

As the transition slopeis reduced the SRRshows an narrowerfrequency response oran increase selectivity

SRR selectivity iscontrolled mainly bythe slope at thetransition point

Better selectivityimplies betterperformance under thepresence of interferers

mSAW > mSAW2

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Which is the optimal (better selectivity)damping function for a give application?

Quench gain or oscillations death rate

Sampling (frequency selectivity)

SR gain or oscillations growth rate

Find the Optimum for a Given Application !

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Optimal damping for this case

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Modern Applications

{ SRR today:

z Ultra low power communication require minimumenergy consumption during the RF communication

{ Application fields:

z

short-distance data-exchange wireless link withmedium data-rate, such as sensor network, homeautomation, robotics, computer peripherals, orbiomedicine.

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Case Studies [6]

A low-power 1-GHz super-regenerative transceiver with time-shared PLL control

The SRR behaves like a PLL for a short amount of time to:

Tune the frequency

Find the optimal transition point

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Case Studies [6]

Operating Voltage: 2.4v

Current of RX mode: 1.5mA

Sensitivity: -105dBm

Selectivity (-5dB attenuation): 150kHz

Data-Rate: 150kbits/s

Frequency Range: 300-1500MHz

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Case Studies [5]

A 400uW-RX, 1.6mW-TX Super-Regenerative Transceiver for Wireless Sensor

Networks

The SRO is based on a extremely high-Q BAW resonator thus reducing the requiredresolution on the Q controlling scheme.

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Case Studies [5]

Operating Voltage: 1v

Current of RX mode: 400uA

Sensitivity: -100.5dBm

Bandwidth: 500kHz

Data-Rate: 5kbits/s

Frequency: 1.7GHz

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Case Studies [4]

A 3.6mW 2.4-GHz Multi-Channel Super-Regenerative Receiver in 130nm CMOS

Similar to case study [1] but the quench/damp signal generated is shaped by the digital

controller to improved the selectivity.critical point

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Case Studies [4]

Operating Voltage: 1.2v

Current of RX mode: 3mA

Sensitivity: -80dBm

Selectivity (channel space): 10MHz

Data-Rate: 500kbits/s

Frequency Range: 2.4GHz ISM

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Challenges:

{ Selectivity:z Maximize control of quench shape and frequency

{ Sensitivity:z 5-20dB lower than heterodyne ones

{ LC tank tuning:z Low-power tuning

{ Data rate:z How to decrease the quench to modulation frequency

ratio

{ Integration level:z On-chip LC tank with enhanced Q (SAW, BAW)

{ Spread spectrum:z PN synchronization and frequency de-hopping

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References:

[1] E. H. Armstrong, Some recent developments of regenerative circuits, Proc. IRE, vol. 10, pp. 244-260, Aug.

1922

[2] J. R. Whitehead, Super-Regenerative Receivers. Cambridge Univ. Press, 1950.

[3] F.X. Moncunill-Geniz, P. Pala-Schonwalder, O. Mas-Casals, A generic approach to the theory of

superregenerative reception,IEEE Transactions on Circuits and Systems-I, vol. 52, No.1, pp:54 70, Jan.

2005.

[4] J.Y. Chen, M. P. Flynn, and J. P. Hayes, A 3.6mW 2.4-GHz multi-channel super-regenerative receiver in 130nm

CMOS,In Proc. IEEE Custom Integrated Circ. Conference, pp. 361-364, Sep. 2005.

[5] B. Otis, Y. H. Chee, and Y. Rabaey, A 400uW-RX, 1.6mW-TX super-regenerative transceiver for wireless

sensor networks,Digest of Technical Papers of the IEEE Int. Solid-State Circ. Conference, vol. 1, pp. 396-397and p. 606, San Francisco, Feb. 2005.

[6] N. Joehl, C. Dehollain, P. Favre, P. Deval, M. Declerq, A low-power 1-GHz super-regenerative transceiver with

time-shared PLL control,IEEE J. of Solid-State Circuits, vol. 36, pp:1025 1031, Jul. 2001.

[7] P. Favre, N. Joehl, A. Vouilloz, P. Deval, C. Dehollain, M.J. Declercq, A 2-V 600-A 1-GHz BiCMOS super-

regenerative receiver for ISM applications,IEEE J. of Solid-State Circuits, vol. 33, pp:2186 2196, Dec. 1998.

[8] F.X. Moncunill-Geniz, P. Pala-Schonwalder, C. Dehollain, N. Joehl, M. Declercq, A 2.4-GHz DSSS

superregenerative receiver with a simple delay-locked loop,IEEE Microwave and Wireless ComponentsLetters, vol 15, pp:499 501, Aug. 2005.

[9] A. Vouilloz, M. Declercq, C. Dehollain, A low-power CMOS super-regenerative receiver at 1 GHz,IEEE

J.Solid-state circuits, vol. 36, pp:440 451, Mar. 2001.

[10] A. Vouilloz, M. Declercq, C. Dehollain, Selectivity and sensitivity performances of superregenerative

receivers, Proc. ISCAS98, vol.4, pp:325-328, Jun. 1998.

[11] F.X. Moncunill-Geniz, C. Dehollain, N. Joehl, M. Declercq, P. Pala-Schonwalder, A 2.4-GHz Low-Power

Superregenerative RF Front-End for High Data Rate Applications,Microwave Conference, 2006. 36thEuropean, pp:1537 1540, Sept. 2006