      SUBROUTINE PASSB2(IDO,L1,CC,CH,WA1)
      DOUBLE PRECISION CC
      DOUBLE PRECISION CH
      DOUBLE PRECISION WA1
      DOUBLE PRECISION TR2
      DOUBLE PRECISION TI2
      DIMENSION CC(IDO,2,L1),CH(IDO,L1,2),WA1(1)

      IF (IDO.GT.2) GO TO 102
      DO 101 K = 1,L1
          CH(1,K,1) = CC(1,1,K) + CC(1,2,K)
          CH(1,K,2) = CC(1,1,K) - CC(1,2,K)
          CH(2,K,1) = CC(2,1,K) + CC(2,2,K)
          CH(2,K,2) = CC(2,1,K) - CC(2,2,K)
  101 CONTINUE
      RETURN
  102 DO 104 K = 1,L1
          DO 103 I = 2,IDO,2
              CH(I-1,K,1) = CC(I-1,1,K) + CC(I-1,2,K)
              TR2 = CC(I-1,1,K) - CC(I-1,2,K)
              CH(I,K,1) = CC(I,1,K) + CC(I,2,K)
              TI2 = CC(I,1,K) - CC(I,2,K)
              CH(I,K,2) = WA1(I-1)*TI2 + WA1(I)*TR2
              CH(I-1,K,2) = WA1(I-1)*TR2 - WA1(I)*TI2
  103     CONTINUE
  104 CONTINUE
      RETURN
      END
