A Design Method for MIMO Radar Frequency Hopping Codes

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							A Design Method for MIMO Radar
Frequency Hopping Codes
6


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2


0
1
                           1
    0.5
                  0.5
          0   0
                        Chun-Yang Chen and P. P. Vaidyanathan
                                   California Institute of Technology
                                    Electrical Engineering/DSP Lab
                                        Asilomar Conference 2007
Outline

 Review of the background
     – Ambiguity function
     – Ambiguity function in MIMO radar


 The proposed waveform design method
     –   Ambiguity function for MIMO pulse radar
     –   Frequency hopping signals
     –   Optimization of the frequency hopping codes
     –   Examples


 Conclusion and future work

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   2
Review: Ambiguity function in MIMO radar




                                           3
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   4
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
   target  (t,n)




u(t)
 TX

    t:delay
    n:Doppler

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   5
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
   target  (t,n)




u(t)      y(t,n) (t)
 TX         RX

    t:delay
    n:Doppler

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   6
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
                         Matched filter output
           (t,n)
                               y
   target                (t ,n )       (t ',n ') 
                                        (t )  y      (t ) dt



u(t)      y(t,n) (t)
 TX         RX

    t:delay
    n:Doppler

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007      7
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
                         Matched filter output
           (t,n)
                               y
   target                (t ,n )       (t ',n ') 
                                          (t )  y        (t ) dt
                              u (t  t )e j 2n t  u (t  t ' ) e  j 2n 't dt

                              u (t )u (t  (t  t ' )) e j 2 (n n ')t dt
u(t)      y(t,n) (t)
 TX         RX

    t:delay
    n:Doppler

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                            8
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
                         Matched filter output
           (t,n)
                               y
   target                (t ,n )       (t ',n ') 
                                          (t )  y        (t ) dt
                              u (t  t )e j 2n t  u (t  t ' ) e  j 2n 't dt

                              u (t )u (t  (t  t ' )) e j 2 (n n ')t dt
u(t)      y(t,n) (t)
                                (t ,n )   u(t )u(t  t ) e
 TX         RX                                                              j 2n t
                                                                                       dt
    t:delay
    n:Doppler                           Ambiguity function

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                  9
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
 n
                     target 1 (t1,n1)
                        target 2 (t2,n2)

                                            t


Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   10
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
 n         (t  t 1 ,n n 1 )

                      target 1 (t1,n1)
                         target 2 (t2,n2)

                                            t


Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   11
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
 n         (t  t 1 ,n n 1 )
                                                  1

                                                 0.8

                                                 0.6


                      target 1 (t1,n1)           0.4




                         target 2 (t2,n2)
                                                 0.2

                                                  0
                                                  1




                                            t
                                                       0.5                                          1
                                                             0                                0.5
                                                                                         0
                                                                 -0.5             -0.5
                                                                        -1   -1




                                  (t ,n )   u(t )u(t  t ) e                  j 2n t
                                                                                             dt
                                      Ambiguity function

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                          12
Ambiguity Function in SIMO Radar
 Ambiguity function characterizes the Doppler and range
  resolution.
 n         (t  t 1 ,n n 1 )
                                                  1

                                                 0.8

                                                 0.6


                      target 1 (t1,n1)           0.4




                         target 2 (t2,n2)
                                                 0.2

                                                  0
                                                  1




                                            t
                                                       0.5                                          1
                                                             0                                0.5
                                                                                         0
                                                                 -0.5             -0.5
                                                                        -1   -1




                                  (t ,n )   u(t )u(t  t ) e                  j 2n t
                                                                                             dt
                                      Ambiguity function

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                          13
MIMO Radar
Transmitter: M antenna elements



       xT0    xT1         xT,M-1
                      …

        u0(t) u1(t)        uM-1(t)




         Transmitter emits
      incoherent waveforms.


Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   14
MIMO Radar
Transmitter: M antenna elements             Receiver: N antenna elements



       xT0    xT1         xT,M-1               xR0    xR1        xR,M-1
                      …                                      …


        u0(t) u1(t)        uM-1(t)               MF     MF         MF
                                                  …      …          …



                                               Matched filters extract
         Transmitter emits
                                            the M orthogonal waveforms.
      incoherent waveforms.                  Overall number of signals:
                                                        NM

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                 15
Ambiguity Function in MIMO Radar
                           (t,nf) t:delay
                                        n:Doppler
      xT0    xT1         xT,M-1         f: Spatial freq.
 TX                  …

       u0(t) u1(t)        uM-1(t)




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   16
Ambiguity Function in MIMO Radar
                                      t:delay
                           (t,nf)    n:Doppler                     (t,nf)
                                      f: Spatial freq.

      xT0    xT1         xT,M-1                   xR0    xR1       xR,M-1
 TX                  …                     RX                  …

       u0(t) u1(t)        uM-1(t)                  MF     MF         MF
                                                    …      …          …




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                    17
Ambiguity Function in MIMO Radar
                                      t:delay
                           (t,nf)    n:Doppler                              (t,nf)
                                      f: Spatial freq.

      xT0    xT1         xT,M-1                   xR0    xR1                xR,M-1
 TX                  …                     RX                        …

       u0(t) u1(t)        uM-1(t)                  MF     MF                  MF
                                                    …      …                   …

                                                             (t ,n , f )
                                                         y                 (t )



Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                             18
Ambiguity Function in MIMO Radar
                                                      t:delay
                                          (t,nf)     n:Doppler                              (t,nf)
                                                      f: Spatial freq.

      xT0         xT1                  xT,M-1                     xR0    xR1                xR,M-1
 TX                                …                        RX                       …

       u0(t) u1(t)                      uM-1(t)                    MF     MF                  MF
                                                                    …      …                   …

                                                                             (t ,n , f )
                                                                         y                 (t )
 Matched filter output

     y                           
           (t ',n ', f ')
                                        y (t ,n , f ) (t )dt
                                   H
                            (t )

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                             19
Ambiguity Function in MIMO Radar
                                                                        t:delay
 Matched filter output                                                  n:Doppler
                                                                        f: Spatial freq.

      y                           
            (t ',n ', f ')          H        (t ,n , f )
                                        y
                                                                        um(t): m-th waveform
                             (t )                          (t )dt       xm: m-th antenna location
                                                                        n: receiving antenna index


                                       u (t t )u (t t ' )e                                      
     N 1                           M 1 M 1
     e j 2 ( f  f ') n 
     n 0                           m 0 m '0
                                                     m
                                                                    *
                                                                    m
                                                                                j 2 (n v ') t
                                                                                                  dt e j 2 ( fxm  f ' xm ' )
  Receiver beamforming




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                                                 20
Ambiguity Function in MIMO Radar
                                                                        t:delay
 Matched filter output                                                  n:Doppler
                                                                        f: Spatial freq.

      y                           
            (t ',n ', f ')          H        (t ,n , f )
                                        y
                                                                        um(t): m-th waveform
                             (t )                          (t )dt       xm: m-th antenna location
                                                                        n: receiving antenna index


                                       u (t t )u (t t ' )e                                      
     N 1                           M 1 M 1
     e j 2 ( f  f ') n 
     n 0                           m 0 m '0
                                                     m
                                                                    *
                                                                    m
                                                                                j 2 (n v ') t
                                                                                                  dt e j 2 ( fxm  f ' xm ' )
  Receiver beamforming


                      m,m ' (t ,n )   um (t )um ' (t  t )e j 2n t dt
                                                 *


                                Cross ambiguity function




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                                                  21
Ambiguity Function in MIMO Radar
                                                                         t:delay
 Matched filter output                                                   n:Doppler
                                                                         f: Spatial freq.

      y                           
            (t ',n ', f ')          H        (t ,n , f )
                                        y
                                                                         um(t): m-th waveform
                             (t )                          (t )dt        xm: m-th antenna location
                                                                         n: receiving antenna index


                                       u (t t )u (t t ' )e                                         
     N 1                           M 1 M 1
     e j 2 ( f  f ') n 
     n 0                           m 0 m '0
                                                     m
                                                                     *
                                                                     m
                                                                                 j 2 (n v ') t
                                                                                                   dt e j 2 ( fxm  f ' xm ' )
  Receiver beamforming


                      m,m ' (t ,n )   um (t )um ' (t  t )e j 2n t dt
                                                 *
                                                                                         [San Antonio et al. 07]
                                                      M 1 M 1
                       (t ,n , f , f ' )     m ,m ' (t ,n )e j 2 ( fx                m      f ' xm ' )

                                                      m  0 m ' 0
                                          MIMO ambiguity function

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                                                   22
Ambiguity Function in MIMO Radar
 Ambiguity function characterizes the Doppler, range, and
  angular resolution.
            n
                               target 1 (t1,n1,f1)
                                  target 2 (t2,n2,f 2)

                                                      t
        f

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   23
Ambiguity Function in MIMO Radar
 Ambiguity function characterizes the Doppler, range, and
  angular resolution.
            n     (t  t 1 ,n n 1 , f1 , f )

                                  target 1 (t1,n1,f1)
                                     target 2 (t2,n2,f 2)

                                                            t
        f     Ambiguity
                                  m,m' (t ,n )   um (t )um (t  t )e j 2n t dt
                                              M 1 M 1
                                                            *


              function   (t ,n , f , f ' )     m ,m ' (t ,n )e j 2 ( fxm  f ' xm ' )
                                                       m  0 m ' 0

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                             24
Proposed Waveform Design Method




                                  25
MIMO Radar Waveform Design Problem
 Choose a set of waveforms {um(t)} so that the ambiguity
  function tnf,f’ can be sharp around {(0,0,f,f)}.
            n     (t  t 1 ,n n 1 , f1 , f )

                                  target 1 (t1,n1,f1)


                                                      t
        f

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   26
MIMO Radar Waveform Design Problem
 Choose a set of waveforms {um(t)} so that the ambiguity
  function tnf,f’ can be sharp around {(0,0,f,f)}.
            n     (t  t 1 ,n n 1 , f1 , f )

                                  target 1 (t1,n1,f1)


                                                            t
        f     Ambiguity
                                  m,m' (t ,n )   um (t )um (t  t )e j 2n t dt
                                              M 1 M 1
                                                            *


              function   (t ,n , f , f ' )     m ,m ' (t ,n )e j 2 ( fxm  f ' xm ' )
                                                       m  0 m ' 0

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                             27
Imposing Waveform Structures
                                               L 1
 Pulse radar                         u m (t )   m (t  Tl ) m-th waveform
    – MTI (Moving Target Indicator)            l 0

    – Doppler pulse radar




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                      28
Imposing Waveform Structures
                                                L 1
 Pulse radar                         u m (t )   m (t  Tl ) m-th waveform
    – MTI (Moving Target Indicator)             l 0

    – Doppler pulse radar


 Frequency hopping
  signals
    – Constant modulus
                                               Q 1
    – Can be viewed as
      generalized LFM (Linear
                                      m (t )   exp( j 2fcmqt ) 1[0,t ) (t  qt )
                                               q 0
       Frequency Modulation)




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                           29
Imposing Waveform Structures
                                                L 1
 Pulse radar                         u m (t )   m (t  Tl ) m-th waveform
    – MTI (Moving Target Indicator)             l 0

    – Doppler pulse radar


 Frequency hopping
  signals
    – Constant modulus
                                               Q 1
    – Can be viewed as
      generalized LFM (Linear
                                      m (t )   exp( j 2fcmqt ) 1[0,t ) (t  qt )
                                               q 0
       Frequency Modulation)


 Orthogonal waveforms                  cmq  cm'q     q, m  m'
                                        
    – Virtual array                      ft  1
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                           30
Ambiguity Function of Pulse MIMO Radar
            L 1
  u m (t )   m (t  Tl )
            l 0                  T
                              T  Tl 1  Tl   nT  0




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   31
Ambiguity Function of Pulse MIMO Radar
            L 1
  u m (t )   m (t  Tl )
            l 0                    T
                              T  Tl 1  Tl          nT  0

      ( ) m,m' (t ,n )   m (t )m (t  t )e j 2n t dt
                                     *



       m (t )m (t  t ) 1dt
                 *
                                     rmm' (t )
                                       ( )
                                        ,




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007        32
Ambiguity Function of Pulse MIMO Radar
            L 1
  u m (t )   m (t  Tl )
            l 0                      T
                                T  Tl 1  Tl           nT  0

      ( ) m,m' (t ,n )   m (t )m (t  t )e j 2n t dt
                                     *



       m (t )m (t  t ) 1dt
                 *
                                        rmm' (t )
                                          ( )
                                           ,

                          M 1 M 1 ( )    j 2 ( fxm  f ' xm ' )  
                                                                         L 1
                                                                              j 2n Tl 
    (t ,n , f , f ' )     rm ,m ' (t )e                          e            
                          m 0 m '0                                  l 0          
                                                                           Doppler processing
                                                                           is separable

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                  33
Ambiguity Function of Pulse MIMO Radar
            L 1
  u m (t )   m (t  Tl )
            l 0                      T
                                T  Tl 1  Tl             nT  0

      ( ) m,m' (t ,n )   m (t )m (t  t )e j 2n t dt
                                     *



       m (t )m (t  t ) 1dt
                 *
                                        rmm' (t )
                                          ( )
                                           ,

                          M 1 M 1 ( )    j 2 ( fxm  f ' xm ' )  
                                                                         L 1
                                                                              j 2n Tl 
    (t ,n , f , f ' )     rm ,m ' (t )e                          e            
                          m 0 m '0                                  l 0          
                                                                           Doppler processing
                            Define as      (t , f , f ' )                 is separable

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                  34
Waveform Design Problem in Pulse
MIMO Radar
                      M 1 M 1
  (t , f , f ' )    rm(m)' (t )e j 2 ( fxm  f ' xm ' )
                           ,
                      m  0 m ' 0



   rmm' (t )   m (t )m (t  t )dt
    ( )
     ,
                          *




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007      35
Waveform Design Problem in Pulse
MIMO Radar
                      M 1 M 1
  (t , f , f ' )    rm(m)' (t )e j 2 ( fxm  f ' xm ' )
                           ,
                      m  0 m ' 0



   rmm' (t )   m (t )m (t  t )dt
    ( )
     ,
                          *


 Choose a set of pulses {m(t)} such that (t,f,f’) can be
  sharp around {(0,f,f)}.




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007      36
Waveform Design Problem in Pulse
MIMO Radar
                       M 1 M 1
   (t , f , f ' )    rm(m)' (t )e j 2 ( fxm  f ' xm ' )
                            ,
                       m  0 m ' 0



    rmm' (t )   m (t )m (t  t )dt
     ( )
      ,
                           *


 Choose a set of pulses {m(t)} such that (t,f,f’) can be
  sharp around {(0,f,f)}.

 Ex: SIMO case: M=1
      (t , f , f ' )  r0(, ) (t )
                            0




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007       37
Waveform Design Problem in Pulse
MIMO Radar
                       M 1 M 1
   (t , f , f ' )    rm(m)' (t )e j 2 ( fxm  f ' xm ' )
                            ,
                       m  0 m ' 0



    rmm' (t )   m (t )m (t  t )dt
     ( )
      ,
                           *


 Choose a set of pulses {m(t)} such that (t,f,f’) can be
  sharp around {(0,f,f)}.

 Ex: SIMO case: M=1
      (t , f , f ' )  r0(, ) (t )
                            0

                  Choose a pulse with a sharp correlation function (e.g. LFM)

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                      38
Orthogonality of the Frequency Hopping
Signals
         Q 1
m (t )   exp( j 2fcmqt ) 1[0,t ) (t  qt )   m
         q 0

     cmq  cm'q   q, m  m'                       m'
     
      ft  1

                                         Frequency


                                              f

                                                             t
                                                                  Time




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007               39
Orthogonality of the Frequency Hopping
Signals
         Q 1
m (t )   exp( j 2fcmqt ) 1[0,t ) (t  qt )   m
         q 0

     cmq  cm'q   q, m  m'                       m'
     
      ft  1

         m (t )m (t )dt   m,m'
                  *




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   40
Orthogonality of the Frequency Hopping
Signals
         Q 1
m (t )   exp( j 2fcmqt ) 1[0,t ) (t  qt )   m
         q 0

     cmq  cm'q   q, m  m'                       m'
     
      ft  1

         m (t )m (t )dt   m,m'
                  *

                         M 1 M 1
        (0, f , f )    rm(m)' (0)e j 2f ( xm  xm ' )  M
                              ,
                         m  0 m ' 0




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007        41
Orthogonality of the Frequency Hopping
Signals
         Q 1
m (t )   exp( j 2fcmqt ) 1[0,t ) (t  qt )   m
         q 0

     cmq  cm'q   q, m  m'                       m'
     
      ft  1

         m (t )m (t )dt   m,m'
                  *

                         M 1 M 1
        (0, f , f )    rm(m)' (0)e j 2f ( xm  xm ' )  M
                              ,
                         m  0 m ' 0

      is a constant along {(0,f,f)}, no matter what codes
      are chosen.

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007        42
Optimization of the Codes
                                     
 Define a vector ωC  vec C (nt , n f , n f ' )            


  ω C  w ω C'                               Code C is better than
                                             code C’.




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007           43
Optimization of the Codes
                                     
 Define a vector ωC  vec C (nt , n f , n f ' )            
    ω C  w ω C'          Code C is better than code C’.


 Def: a code C is efficient if there exists no other code C’
  such that



                ω C'  w ω C
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007       44
Optimization of the Codes
                                     
 Define a vector ωC  vec C (nt , n f , n f ' )            
    ω C  w ω C'          Code C is better than code C’.


 Def: a code C is efficient if there exists no other code C’
  such that    ω C'  w ω C

 For any f  i gi where gi are increasing convex
  functions
      ωC'  w ωC  f (ωC' )  f (ωC )

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007       45
Optimization of the Codes
                                     
 Define a vector ωC  vec C (nt , n f , n f ' )            
    ω C  w ω C'          Code C is better than code C’.


 Def: a code C is efficient if there exists no other code C’
  such that    ω C'  w ω C

 For any f  i gi where gi are increasing convex
  functions    ωC'  w ωC  f (ωC' )  f (ωC )

 So a code C is efficient if              f (ωC )  f (ωC' )
                                                                 for all C’.
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                     46
Optimization of the Codes
                                     
 Define a vector ωC  vec C (nt , n f , n f ' )            
    ω C  w ω C'          Code C is better than code C’.


 Def: a code C is efficient if there exists no other code C’
  such that    ω C'  w ω C

 For any f  i gi where gi are increasing convex
  functions    ωC'  w ωC  f (ωC' )  f (ωC )

 So a code C is efficient if f (ωC )  f (ωC' ) for all C’.
 Example: f (ωc )  ωc p
                         p



Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007       47
Optimization of the Codes
                  1 1
        min    (t , f , f ' ) dt df df '
                                                        p

           C
                  0 0
               C {0,1, K  1}MQ
               
               
               
                   cmq  cm 'q                    q, m  m'

      M:# of waveforms
                                            Q 1
      Q: # of freq. hops
      K: # of freq.                m (t )   exp( j 2cmqt ) 1[0,t ) (t  qt )
                                            q 0
      Time-bandwidth product:
      KfQt

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                           48
Simulated Annealing Algorithm
      min f p (C)
        C
                       subject to    C 

 Simulated annealing [S. Kirkpatrick et al. 85]
    – Create a Markov chain on the set A

                                                                 C’
                                                      C

                                                                 …




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   …        49
Simulated Annealing Algorithm
      min f p (C)
        C
                        subject to   C 

 Simulated annealing [S. Kirkpatrick et al. 85]
    – Create a Markov chain on the set A with the equilibrium distribution

                      1      f p (C)                           C’
             T (C)     exp 
                                     
                                  T 
                                                      C
                      ZT             
                          f p (C)                              …
            ZT   exp          
                  C        T   




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   …          50
Simulated Annealing Algorithm
      min f p (C)
        C
                        subject to   C 

 Simulated annealing [S. Kirkpatrick et al. 85]
    – Create a Markov chain on the set A with the equilibrium distribution

                      1      f p (C)                           C’
             T (C)     exp 
                                     
                                  T 
                                                      C
                      ZT             
                          f p (C)                              …
            ZT   exp          
                  C        T   




                                                             …
    – Run the Markov chain Monte Carlo (MCMC)


Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007              51
Simulated Annealing Algorithm
      min f p (C)
        C
                        subject to   C 

 Simulated annealing [S. Kirkpatrick et al. 85]
    – Create a Markov chain on the set A with the equilibrium distribution

                      1      f p (C)                           C’
             T (C)     exp 
                                     
                                  T 
                                                      C
                      ZT             
                          f p (C)                              …
            ZT   exp          
                  C        T   




                                                             …
    – Run the Markov chain Monte Carlo (MCMC)
    – Decrease the temperature T from time to time
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007              52
Examples
            Proposed Freq. Hopping Signals
                    Parameters:
                    Uniform linear array
                    # of waveforms M =4
                    # of hops       Q=10
                    # of freq.      K=15
                    norm type       p=3
    1

    0

   -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1
    1

    0

   -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1
    1

    0

   -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1
    1

    0

   -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007             53
Examples
            Proposed Freq. Hopping Signals                                             Orthogonal LFM
                    Parameters:                                                  Parameters:
                    Uniform linear array
                                                                                – The same array
                    # of waveforms M =4
                    # of hops       Q=10                                        – The same duration and
                    # of freq.      K=15                                          bandwidth
                    norm type       p=3                                         – Initial frequencies
    1                                                                  1

    0                                                                  0

   -1                                                                  -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1
    1                                                                  1

    0                                                                  0

   -1                                                                  -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1
    1                                                                  1

    0                                                                  0

   -1                                                                  -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1
    1                                                                  1

    0                                                                  0

   -1                                                                  -1
        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1        0    0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                                                                 54
Examples – Ambiguity Function

Proposed Freq. Hopping Signal                      Orthogonal LFM




                              |(t,f,f’)|
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007          55
Examples – Ambiguity Function

Proposed Freq. Hopping Signal                      Orthogonal LFM




                      10log10|(t,f,f’)|
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007          56
Examples – Sorted Samples of Ambiguity
Functions
             10log10(|(t,f,f’)|)
    0
                                                          LFM
                                                          Randomly selected code
   -5
                                                          Proposed method

                                                              10log10(|(t,f,f’)|)
  -10                                                0

                                                    -5

                                                    -10
  -15
     0       2       4        6       8       10
                                                    -15
                 Sorted samples (%)
                                                    -20
                                                          0    20     40    60       80   100
                                                              Sorted samples (%)
Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                  57
     Examples – Correlation Function Matrix

           Proposed Freq. Hopping Signal                                                             Orthogonal LFM
1                  1                  1                   1                  1                  1                  1                  1

0                  0                  0                   0                  0                  0                  0                  0

-1                 -1                 -1                  -1                 -1                 -1                 -1                 -1
     0   0.5   1        0   0.5   1        0    0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5    1
1                  1                  1                   1                  1                  1                  1                  1

0                  0                  0                   0                  0                  0                  0                  0

-1                 -1                 -1                  -1                 -1                 -1                 -1                 -1
     0   0.5   1        0   0.5   1        0    0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5    1
1                  1                  1                   1                  1                  1                  1                  1

0                  0                  0                   0                  0                  0                  0                  0

-1                 -1                 -1                  -1                 -1                 -1                 -1                 -1
     0   0.5   1        0   0.5   1        0    0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5    1
1                  1                  1                   1                  1                  1                  1                  1

0                  0                  0                   0                  0                  0                  0                  0

-1                 -1                 -1                  -1                 -1                 -1                 -1                 -1
     0   0.5   1        0   0.5   1        0    0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5   1        0   0.5    1



                                               rmm' (t )   m (t )m (t  t )dt
                                                ( )
                                                 ,
                                                                      *


     Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007                                                                                      58
Conclusion
 MIMO radar frequency hopping waveform design
  method
     – Sharper ambiguity function (Better resolution)
     – Applicable in the case of
        • pulse radar
        • orthogonal waveforms


 Future work
     – Other optimization tools
     – Phase coded signals

Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007   59
Thank You!

                                Q&A                      Any questions?




Chun-Yang Chen, Caltech DSP Lab | Asilomar Conference 2007          60

						
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