This document discusses using filter banks with phase locked loops for high data rate satellite links. It introduces digital modulation schemes and describes quadrature mirror filter banks and discrete cosine transform filter banks. It then shows how these filter banks can be implemented in a digital PLL design to improve synchronization and signal recovery for satellite communications. The filter banks allow the PLL to adapt to different modulation schemes and channel conditions.

1. Phase Locked Loop with Filter Banks for
High Data Rate Satellite Link
Chirag Warty Richard Wai Yu
RF and Wireless Engineer System Engineer
IEEE Associate Member NAVSEA – Port Hueneme

2. INDEX
• Introduction
• Conventional PLL Design
• Digital Modulation schemes
• Amplitude Shift Keying (ASK)
• Frequency Shift Keying (FSK)
• Phase Shift Keying (PSK)
• Quadrature Mirror Filter Banks
• Two Channel Model
• Multiple Channel Filter Bank
• Discrete Cosine Transform Filter Banks
• Practical model with delays
• Digital PLL Design Implementation
• Conclusion

3. Introduction
• Satellite Communication System • M-channel uniform filter banks to
– LEO (Low Earth Orbit) minimize error by optimizing the
– MEO (Medium Earth Orbit) performance in decomposition and
– GEO (Geosynchronous orbit) reconstruction of signals
• Atmospheric effects and ambient noise • Two basic designs
effect the link – Quadrature Mirror Filter banks (QMF)
– Discrete Cosine Transform Filter banks
• Global Connectivity (DCT)
• Immediate signal lock – Key to minimal • Effects of variable architecture of filter
data loss banks on probability of recovering the
original signal
Noise Channel
Transmitter PLL Receiver

4. Conventional PLL Design
• PLL compares phase of the incoming signal with the output of the voltage
controlled oscillator (VCO) and adjusts the frequency of its oscillator to keep the
system in phase with the received signal
• Loop filter – Band pass operation
• To extract the original signal from the incoming signal the receiver has to be
synchronized with the received carrier
• When in sync the transmitter and the receiver would have the same bit sequence
going through zero simultaneously
Phase Fout
Loop Filter VCO
Detector
Fin
Fout/N Feedback
Counter

5. Phase Lock Loop
• Phase Detector • Loop Filter
• Carrier waveform : • Core Decision Making Block
• Output of the phase detector • Two response models :
– Transient response
– Steady state response
• Applying Fourier Transform to input signal
• Phase error
– Posetive :
– Negative:
Noise Error Signal e(t)
Phase
F out
+ Detector Loop Filter VCO
F in
Fout/N Feedback
Counter

6. Phase Lock Loop
• Voltage Controlled Oscillator (VCO)
• Rate of change in the output frequency due to an incremental change in the input signal
• Loop transfer function
Noise Error Signal e(t)
Phase
F out
+ Detector Loop Filter VCO
F in
Fout/N Feedback
Counter

7. EXOSPHERE
Channel Conditions
The communication link for a terrestrial ground station and
the airborne platform has conventionally been in C-band
(4GHz – 8GHz) to Ku – Band (12GHz – 18GHz)
300 miles
IONOSPHERE
GEO platforms docked in the Exospheric layer of the Earth’s
atmosphere and are in a state of constant motion,
travelling at almost 10 miles/sec
Atmospheric effects
frequency selective fading 50 miles
Doppler shift STRATOSPHERE
Ozone layer
The noise is induced in the form of additive white Gaussian
noise (AWGN) at the loop filter.
10 miles
TROPOSPHERE
The filter plays a decisive role in recovering the original
signal from the noisy version of the received signal
UV/Visible Light
Ground noise

8. M–ary Amplitude Shift Keying (MASK)
0
SNR vs. P(BER) for M-ary Amplitude Shift Keying
10
BASK
4-ASK
8-ASK
16-ASK
-2
10
Probability of Bit Error Rate
-4
10
-6
10
0 5 10 15 20 25
• Earliest Forms of Radio Telegraphy
• Simple implementation but susceptible to
noise and distortion
Eb/No [dB]

9. M–ary Frequency Shift Keying (MFSK)
SNR Vs. P(BER) for M-ary Frequency Shift Keying
0
BFSK
10 4-FSK
8-FSK
Probability of Bit Error Rate
16-FSK
-2
10
-4
10
-6
10
0 5 10 15
Eb/No [dB]
• Performance decreases as SNR increases
• Immune to amplitude changes but susceptible
to ambient frequencies

10. M–ary Phase Shift Keying (MPSK)
SNR vs. P(BER) for M-ary Phase Shift Keying
BPSK
0
10 QPSK
8-PSK
16-PSK
Probability of Bit Error Rate
-2
10
-4
10
-6
10
0 5 10 15 20
Eb/No [dB]
• Receiver and Transmitter need to be
synchronized
• Better performances than MASK and MFSK Phase component of the signal varies in time
• BPSK and QPSK show similar performance

11. Quadrature Mirror Filter Banks
…. …. …
• Basic Building Block – Two Channel model Two
Channel
QMF Bank
• Analysis Section - Two decimator blocks …. …. ….
• Synthesis Section – Two Interpolator Block
• Where is the frequency response of
the LPF and is a mirror image HPF
frequency response
• To achieve perfect reconstruction the
output of the QMF bank should be
identical to the input

12. Multiple QM Filter Banks
Even Set of band Pass Filters
Consist of Analysis Section and Synthesis
Section
PLL Tracking response in Time Domain
0.2
Input
PLL Tracking
0.15
0.1
Magnitude (Volts) 0.05
The analysis filter bank consist of N filters
with where L = 0, 1, 2 …….. N-1, as a 0
system function, which can be obtained by -0.05
uniformly shifting the frequency response of
a low pass filter (LPF) by multiples of -0.1
-0.15
-0.2
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Time (microseconds)

13. Discrete Cosine Transform Filter Banks
n(s)
+ Phase Detector
R(s) + + E(s)
VCO
Y(s)
-
Noisy signal
Loop Filter
H(s)
Fout/N
Feedback
Counter
• Real valued transform that map integer valued signals to floating point coefficients
• Where x(n) is real and even, by using symmetry property of DFT reduces to

14. Digital PLL Design Simulation
Frequency Response of the Filter Banks
50
Magnitude (dB)
0
-50
-100
-150
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Frequency - Normalized (radians/sample)
Phase Response of the Filter Bank
0
Phase (degrees)
-500
-1000
-1500
-2000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Frequency - Normalized (radians/sample)
• Implementing a Low Pass Filter at PLL with stop band at -50 dB
• Fast response compared to traditional PLL loop filter
• Phase response : Similar to FIR filter response
• With satellite bands advancing in to Ka and Ku bands the filter banks need to employ fast
algorithms that can analyze traffic nearly instantaneously

15. Conclusion
• The loop filter in the PLL is the key element to lock on to the phase of the
received signal to synchronize the receiver with the transmitting entity.
• Filter banks provide pseudo adaptive characteristics to PLL, to suite the desired
modulation scheme and the varying order of M
• PLL can operate and adapt to several different environments, atmospheric
conditions and available bandwidth.
• DCT filter banks are acutely sensitive to image processing, thus giving the PLL
circuit an edge on satellite transmissions that include video streaming
• Possibility to introduce other types of filter banks, which reduce clutter.