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SuperRegenerative Receiver
Ultra lowpower RF Transceiver for high input power & lowdata rate applications
Thanks to this material to Felix Fernandez ECEN 665 TAMU AMSC
Overview
Invented by Armstrong in 1922 and widely used in vacuum tube circuits until the 1950's It was replaced by the superheterodyne receiver due to its poor selectivity and sensitivity Pros:
Small number of components allow for high integration Low power High energy efficiency
Cons
poor sensitivity poor selectivity low datarate limited demodulation capability
Superregenerative Receiver Block Diagram
Superregenrative Oscillator LNA Selective Network 0
Demodulator Envelope Detector LPF
Ka(t)
Quench Oscillator QU
Superregenerative Receiver Block Diagram & Basic Model
d 2V dV V + = A cos(t ) C 2 +G dt dt L
G = 2C 1 G 2 2 d =  = 0  LC 2C
2
V=
A0 (  + jd )t A0 (   jd )t A sin (0t )  + e e G 2 j d G 2 j d G
Gt
A0 2C A e sin (d t ) + sin (0t ) = Gd G
WWII German Air Interception
(first generation SRR, circa 1940)
Operation Fundamentals
140 Bode D iagram From Input P : oint To: O utput P oint 120 100 80
Magnitude (dB)
60
Ga(t) = 0 [Ga(t) is a negative conductance]
40
20
0
20
40 4 10
10 Frequency (rad/sec)
5
10
6
8
x 10
4
P oleZero M ap
6
stable operation
2 Imaginary Axis
0
2
4
G(t ) =
i(t) v(t)
6
Ga(t) >> G0
8 8000
6000
4000
2000 R Axis eal
close to unstable (high Q)
4
0
2000
unstable operation
4000
Ga(t) = G0
Operation Modes
Linear: The self sustained oscillations are quenched before they reach their maximum amplitude. The height of the SRO output has a linear relationship with the RF input power. Logarithmic: The self sustained oscillations are allowed to reach their maximum amplitude. The area enclosed by the envelope of the SRO output has a logarithmic relationship with the RF input power
vsro(t)
Quenching Mode
External Quenching:
The oscillations of the SRO are quenched by an external oscillator that controls the negative admittance at a fixed frequency
Self Quenching
The oscillation of the SRO are controlled by a feedback network which quenches the oscillation after they have reached a certain threshold
Low RF Input
High RF Input
Low RF Input
High RF Input
`0'
`1'
`0'
`1'
Building Blocks Operation
LNA
Feeds the RF input to the SRO Provides antenna matching Isolates SRO oscillations from the antenna Generate the oscillations needed for the superregenerative operation Quench the SRO oscillations according to the quenching mode Detect the SRO oscillation envelope and digitize the signal Provide tuning ability to the selective network (original tuning scheme was manual tuning)
SRO
Quench Oscillator Demodulator Tuning (PLL)
Super Regenerative System Design Equations
i(t) G0 Ga(t) L C

O
2Q (t )
t
e
(t)
AVG
ta tb t
Super regenerative gain
Ks = e
0 (t )dt
tb
0
1
i(t)
s(t)
p(t)
Output pulse shape
p(t ) = e s(t ) = e
0 (t )dt
t
tb t
ta
tb
t
0 (t )dt
Sensitivity function
0
F {i (t ) s (t )}
Frequency response is given by the Fourier transform of the RF envelope and the sensitivity function.
Selective Network Design Equations
2 00 s G (s ) = K 0 2 2 s + 2 00 s + 0
H (s ) = G (s ) 1 + G (s )K a
2 00 s H (s ) = K 0 2 * 2 s + 2 00 (1 ± K 0 K a )s + 0
K0: Ka(t): 0: AVG:
±: depends on the quench control signal
maximum amplification variable gain controlled by quench signal quiescent damping factor damping factor average value
(t ) = 0 (1 K 0 K a (t ))
K = K a (t ) t =ta
* a
Q(t ) =
1 2 (t )
Quench signal frequency limitations
Avoid resonance from previous cycles (a.k.a. hangover) The hangover coefficient is the relationship between the amplitudes of the first cycle and the second (unwanted) one.
h=e
 2 AVG
0 QU
Examples
Setup
FRF= 10kHz FINT=10.5kHz FQUENCH=100Hz Q=5 LPF: 3RD order Butterworth with f3dB 800Hz Several quench signals
System was simulated using MatLab's Simulink.
Sine Quench
Sawtooth Quench
Different Damping Functions (t)
Frequency Response for Different Damping Functions 5 0 5 10 15 20 25 30 35 40 45 50 0.05 SAWTOOTH SINE SAWTOOTH 2
mSAW > mSAW2
As the transition slope is reduced the SRR shows an narrower frequency response or an increase selectivity SRR selectivity is controlled mainly by the slope at the transition point Better selectivity implies better performance under the presence of interferers
Normalized Magnitude
0.04
0.03
0.02
0.01 0 0.01 Nomralizad Frequency
0.02
0.03
0.04
0.05
Which is the optimal (better selectivity) damping function for a give application?
Quench gain or oscillation's death rate Sampling (frequency selectivity) SR gain or oscillation's growth rate
Find the Optimum for a Given Application !
Optimal damping for this case
Modern Applications
SRR today:
Ultra low power communication require minimum energy consumption during the RF communication
Application fields:
shortdistance dataexchange wireless link with medium datarate, such as sensor network, home automation, robotics, computer peripherals, or biomedicine.
Case Studies [6]
A lowpower 1GHz superregenerative transceiver with timeshared PLL control · The SRR behaves like a PLL for a short amount of time to: · Tune the frequency · Find the optimal transition point
Case Studies [6]
Operating Voltage: Current of RX mode: Sensitivity: Selectivity (5dB attenuation): DataRate: Frequency Range: 2.4v 1.5mA 105dBm 150kHz 150kbits/s 3001500MHz
Case Studies [5]
A 400uWRX, 1.6mWTX SuperRegenerative Transceiver for Wireless Sensor Networks The SRO is based on a extremely highQ BAW resonator thus reducing the required resolution on the Q controlling scheme.
Case Studies [5]
Operating Voltage: Current of RX mode: Sensitivity: Bandwidth: DataRate: Frequency: 1v 400uA 100.5dBm 500kHz 5kbits/s 1.7GHz
Case Studies [4]
A 3.6mW 2.4GHz MultiChannel SuperRegenerative 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
Case Studies [4]
Operating Voltage: Current of RX mode: Sensitivity: Selectivity (channel space): DataRate: Frequency Range: 1.2v 3mA 80dBm 10MHz 500kbits/s 2.4GHz ISM
Challenges:
Selectivity:
Maximize control of quench shape and frequency
Sensitivity:
520dB lower than heterodyne ones
LC tank tuning:
Lowpower tuning
Data rate:
How to decrease the quench to modulation frequency ratio
Integration level:
Onchip LC tank with enhanced Q (SAW, BAW)
Spread spectrum:
PN synchronization and frequency dehopping
References:
[1] E. H. Armstrong, " Some recent developments of regenerative circuits," Proc. IRE, vol. 10, pp. 244260, Aug. 1922 [2] J. R. Whitehead, SuperRegenerative Receivers. Cambridge Univ. Press, 1950. [3] F.X. MoncunillGeniz, P. PalaSchonwalder, O. MasCasals, "A generic approach to the theory of superregenerative reception," IEEE Transactions on Circuits and SystemsI, vol. 52, No.1, pp:54 70, Jan. 2005. [4] J.Y. Chen, M. P. Flynn, and J. P. Hayes, "A 3.6mW 2.4GHz multichannel superregenerative receiver in 130nm CMOS," In Proc. IEEE Custom Integrated Circ. Conference, pp. 361364, Sep. 2005. [5] B. Otis, Y. H. Chee, and Y. Rabaey, "A 400uWRX, 1.6mWTX superregenerative transceiver for wireless sensor networks," Digest of Technical Papers of the IEEE Int. SolidState Circ. Conference, vol. 1, pp. 396397 and p. 606, San Francisco, Feb. 2005. [6] N. Joehl, C. Dehollain, P. Favre, P. Deval, M. Declerq, "A lowpower 1GHz superregenerative transceiver with timeshared PLL control," IEEE J. of SolidState Circuits, vol. 36, pp:1025 1031, Jul. 2001. [7] P. Favre, N. Joehl, A. Vouilloz, P. Deval, C. Dehollain, M.J. Declercq, "A 2V 600A 1GHz BiCMOS superregenerative receiver for ISM applications," IEEE J. of SolidState Circuits, vol. 33, pp:2186 2196, Dec. 1998. [8] F.X. MoncunillGeniz, P. PalaSchonwalder, C. Dehollain, N. Joehl, M. Declercq, "A 2.4GHz DSSS superregenerative receiver with a simple delaylocked loop," IEEE Microwave and Wireless Components Letters, vol 15, pp:499 501, Aug. 2005. [9] A. Vouilloz, M. Declercq, C. Dehollain, "A lowpower CMOS superregenerative receiver at 1 GHz," IEEE J.Solidstate circuits, vol. 36, pp:440 451, Mar. 2001. [10] A. Vouilloz, M. Declercq, C. Dehollain, "Selectivity and sensitivity performances of superregenerative receivers," Proc. ISCAS'98, vol.4, pp:325328, Jun. 1998. [11] F.X. MoncunillGeniz, C. Dehollain, N. Joehl, M. Declercq, P. PalaSchonwalder, "A 2.4GHz LowPower Superregenerative RF FrontEnd for High Data Rate Applications," Microwave Conference, 2006. 36th European, pp:1537 1540, Sept. 2006
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