FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See section 10, rule 13) "CODING APPARATUS AND DECODING APPARATUS" PANASONIC CORPORATION, of 1006, Oaza Kadoma, Kadoma-shi, Osaka, 5718501 The following specification particularly describes the invention and the manner in which it is to be performed. 2F04019-PCT DESCRIPTION CODING APPARATUS AND DECODING APPARATUS Technical Field [0001] The present invention relates to a coding apparatus mounted on a radio communication apparatus or the like for coding a voice signal, audio signal or the like and a decoding apparatus for decoding this coded signal. Background Art [0 002] A coding technology for compressing a voice signal, audio signal or the like to a low bit rate signal is particularly important from the standpoint of effectively using a transmission path capacity (channel capacity) of radio waves or the like and a recording medium in a mobile communication system. [0003] Examples of a voice coding scheme for coding a voice signal include schemes like G726, G729 standardized by the ITU-T (International Telecommunication Union Telecommunication Standardization Sector). These schemes use narrow band signals (300 Hz to 3.4 kHz) as coding targets and can perform high quality coding at bit rates of 8 kbits/s to 32 kbits/s. However, since such a narrow band signal is so narrow that its frequency band is a maximum of 3.4 kHz, the quality thereof is such that it gives the user an impression that a sound is muffled, 2F04019-PCT which results in a problem that it lacks a sense of realism. [0004] Furthermore, there is also a voice coding scheme that uses wideband signals (50 Hz to 7 kHz) as coding targets. Typical examples of this are G722, G722.1 of ITU-T and AMR-WB of 3GPP (The 3rd Generation Partnership Project) . These schemes can perform coding of wideband voice signals at a bit rate of 6.6 kbits/s to 64 kbits/s. However, when the signal to be coded is voice, although a wideband signal has relatively high quality, it is not sufficient when an audio signal is the target or a voice signal of higher quality with a sense of realism is required. [0005] On the other hand, when a maximum frequency of a signal is generally on the order of 10 to 15 kHz, it is possible to obtain a sense of realism equivalent to FM radio, and when the maximum frequency is on the order ofupto20kHz, itispossibleto obtain qual ity comparable to that of CD (compact disk) . For such a signal, audio coding represented by the layer III scheme or AAC scheme standardized by MPEG (Moving Picture Expert Group) is appropriate. However, these audio coding schemes have a wide frequency band of a signal tobe coded, which results in a problem that the bit rate of a coded signal increases . [0006] Examples of conventional coding technologies include a technology of coding a signal with a wide frequency band at a low bit rate (e.g., see Patent Document 1) . According to this, an input signal is divided into 2F04019-PCT a signal of a low-frequency domain and a signal of a high-frequency domain, the spectrum of the signal of the high-frequency domain is replaced by the spectrum of the signal of the low-frequency domain and coded, and the overall bit rate is thereby reduced. [0007] FIG.1A to FIG. ID show an overview of the above described processing of replacing the spectrum of high-frequency domain by the spectrum of the low-frequency domain. This processing is originally intended to be performed in combination with coding processing, but for simplicity of explanation, a case where the above described processing is performed on an original signal will be explained as an example. [0008] FIG.1A shows a spectrum of an original signal whose frequency band is restricted to 0^k