Transmission signal processing apparatus

• US 5,583,887 A
• Filed: 03/15/1993
• Issued: 12/10/1996
• Est. Priority Date: 03/13/1992
• Status: Expired due to Term

• Current Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Original Assignee: Fujitsu Limited
• Inventors: Murata, Hiroyasu, Kaku, Takashi
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US08/031,621
• Time in Patent Office: 1,366 Days
• Field of Search: 375/12, 375/122, 375/229, 375/230, 375/295, 375/296, 375/285, 375/377, 364/724.1, 364/577, 364/572, 348/720, 348/538, 370/69.1
• US Class Current: 375/229
• CPC Class Codes: H03H 17/0657 where the output-delivery frequency is higher than the input sampling frequency, i.e. interpolation
• CPC Class Codes: H04J 1/05 using digital techniques
• CPC Class Codes: H04L 25/05 Electric or magnetic storage of signals before transmitting or retransmitting for changing the transmission rate

Abstract

A roll off filter portion for an input transmission point signal executes a roll-off filtering process and an interpolation process with a multiple of two at the same time. The roll-off filtering process is adapted to form a frequency spectrum characteristic in a cosine roll-off shape for the input signal. An interpolator portion, connected to the roll-off filter portion, executes an interpolation process with a multiple of two. This process is a filtering process for forming a frequency spectrum characteristic in a cosine roll-off shape for an input signal. Depending on what multiple of the original sampling frequency a transmission point signal is interpolated, a corresponding number of the interpolator portions are connected in a cascade shape. when a plurality of channels of transmission point signals are modulated and multiplexed according to an FDM system, a corresponding number of signal processing systems are disposed according to the plurality of transmission point signals with different modulation rates.

Claims

1. A transmission signal processing apparatus comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a transmission point signal to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolation means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, the interpolation process being executed at least one time to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated.

2. A transmission signal processing apparatus comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a transmission point signal to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, the interpolation process being executed at least one time to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

wherein the number of execution times of said interpolation process of said interpolator means is given by the following formula;

space="preserve" listing-type="equation">n=log2(f1/f2)-1

where f1 is a frequency at which said transmission point signal can be modulated;

f2 is a sampling frequency of said transmission point signal which is inputted to said roll-off filter means; and

n is the number of execution times of said interpolation process.

3. A transmission signal processing apparatus comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a transmission point signal to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, the interpolation process being executed at least one time to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

wherein said interpolation process of said interpolator means has the same frequency spectrum characteristic when said interpolation process is executed twice or more.

4. A transmission signal processing apparatus which has a plurality of channels for receiving a plurality of transmission point signals, comprising:

roll-off filer means for executing a roll-off filtering process and an interpolation process with a multiple of two for a corresponding transmission point signal of said plurality of transmission point signals to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, said interpolation process being executed at least one time to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated.

5. A transmission signal processing apparatus which has a plurality of channels for receiving a plurality of transmission point signals, comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a corresponding transmission point signal of said plurality of transmission point signals to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, said interpolation process being executed at least one time to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

wherein the number of execution times of said interpolation process of said interpolator means for said transmission point signal is given by the following formula;

space="preserve" listing-type="equation">n=log2(f1/f2)-1

where f1 is a frequency at which said transmission point signal can be modulated;

f2 is a sampling frequency of said transmission point signal which is inputted to said roll-off filter means; and

n is the number of execution times of said interpolation process.

6. A transmission signal processing apparatus which has a plurality of channels for receiving a plurality of transmission point signals, comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a corresponding transmission point signal of said plurality of transmission point signals to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, said interpolation process being executed at least one time to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated.

wherein said interpolation process of said interpolator means for said transmission point signal has the same frequency spectrum characteristic when said interpolation process is executed twice or more.

7. A transmission signal processing apparatus comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a transmission point signal to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic or said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, at least one interpolator means being arranged in a cascade to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated.

8. A transmission signal processing apparatus comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a transmission point signal to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received form said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, at least one interpolator means being arranged in a cascade to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

wherein the number of said interpolator means is given by the following formula;

space="preserve" listing-type="equation">n=log2(f1/f2)-1

where f1 is a frequency at which said transmission point signal can be modulated;

f2 is a sampling frequency of said transmission point signal which is inputted to said roll-off filter means; and

n is the number of said interpolator means.

9. A transmission signal processing apparatus comprising;

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a transmission point signal to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, at least one interpolator means being arranged in a cascade to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

herein said interpolator means has the same frequency spectrum characteristic when the number of said interpolation means is two or more.

10. A transmission signal processing apparatus which has a plurality of channels for receiving a plurality of transmission point signals, comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a corresponding transmission point signal of said plurality of transmission point signals to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filter process for forming a frequency spectrum characteristic of said received point signal in a cosine roll-off shape, at least one said interpolator means being arranged in a cascade to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated.

11. A transmission signal processing apparatus which has a plurality of channels for receiving a plurality of transmission point signals, comprising:

roll-off filer means for executing a roll-off filtering process and an interpolation process with a multiple of two for a corresponding transmission point signal of said plurality of transmission point signals to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said received signal in a cosine roll-off shape, at least one said interpolator means being arranged in a cascade to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

wherein the number of said interpolator means for said transmission point signal is given by the following formula;

space="preserve" listing-type="equation">n-log2(f1/f2)-1

where f1 is a frequency at which said transmission point signal can be moduatled;

f2 is a sampling frequency of said transmission point signal which is inputted to said roll-off filter means; and

n is the number of said interpolator means.

12. A transmission signal processing apparatus which has a plurality of channels for receiving a plurality of transmission point signals, comprising:

roll-off filter means for executing a roll-off filtering process and an interpolation process with a multiple of two for a corresponding transmission point signal of said plurality of transmission point signals to limit a frequency band of said transmission point signal, said roll-off filtering process being adapted to form a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape; and

interpolator means for executing an interpolation process with a multiple of two for a signal received from said roll-off filter means, the interpolation process being a filtering process for forming a frequency spectrum characteristic of said transmission point signal in a cosine roll-off shape, at least one said interpolator means being arranged in a cascade to raise a sampling frequency of said received signal to a frequency at which said transmission point signal can be modulated,

wherein said interpolator means has the same frequency spectrum characteristic when the number of said interpolator means is two or more.