Abstract
The modulation noise and the special case, dc erased noise in magnetic recording are discussed theoretically, taking account of two main causes at the same stage, i.e. the magnetic properties such as the inhomogeneous distribution of the particles on the tape, and the mechanical properties such as the head-to-tape space variations arising from the tape surface roughness. We derive the signal as well as the noise power spectrum of the induced voltage at the read head. This is done by generalizing the theory of the signal behaviour. The theoretical result turned out to agree quite well with the experimental one. The modulation noise power spectrum can be interpreted to consist of two parts, i.e. the steep peak due to the mechanical causes near the recorded signal wavenumber and the broad peak due to magnetic causes.
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Abbreviations
- A(k) :
-
variable defined byν(Kmav L g L d)2
- d :
-
head-to-tape spacing [m]
- d av :
-
average value ofd [m]
- Δd :
-
variance ofd [m]
- ΔD :
-
variable defined by (8)
- e(t) :
-
induced voltage at the read head [V]
- g :
-
gap length [m]
- H :
-
the Karlqvist head field excited by a current uniti [A/m]
- i :
-
a curren unit [A]
- j:
-
√−1
- k=¦k¦:
-
wavenumber [m−1]
- k c :
-
wavenumber of recorded signal [m−1]
- K :
-
constant which includes the number of turn of head, the read head efficiency and the permeabilityμ 0[Vs/Am]
- l d :
-
correlation length of the variationΔd [m]
- l m :
-
correlation length of the variationΔm [m]
- L d (k) :
-
spacing loss defined by exp(−kdav)
- L g (k) :
-
gap loss defined by sin(gk/2)/(gk/2)
- M :
-
magnetization of the tape [A/m]
- ΔM :
-
variable defined by (8)
- m :
-
amplitude of the magnetization of the signal pattern [A/m]
- m av :
-
average value ofm [A/m]
- Δm :
-
variance ofd [A/m]
- P(k) :
-
power spectrum [V2/Hz]
- P dc(k):
-
noise power spectrum [V2/Hz]
- S :
-
signal pattern of the tape
- v :
-
relative velocity between the head and the tape [m/s]
- x t =(x t ,yt):
-
coordinate on the tape
- (x 0,y0):
-
coordinate fixed on the read head
- (x 1,y1):
-
coordinate defined by (10)
- δ :
-
tape thickness [m]
- θ d :
-
random phase variable defined by (8)
- θ m :
-
random phase variable defined by (8)
- μ O :
-
permeability [Vs/Am]
- Φ :
-
read-head detected flux [Wb]
References
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