Pulse or digital communications – Multilevel
Reexamination Certificate
1997-09-16
2001-04-03
Pham, Chi (Department: 2631)
Pulse or digital communications
Multilevel
C375S377000
Reexamination Certificate
active
06212241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio receiver and, more specifically, to a radio receiver which receives a digital-modulated signal to produce received data through an analog-to-digital converter.
2. Description of the Related Art
In general, a radio receiver such as a pager employs an intermittent receiving scheme so as to save the battery power. Further, there has been proposed a system which can stop supplying main clock pulses to a CPU during each receiving period to stabilize the radio receiving characteristics. In Japanese Patent Unexamined Publication No. 7-99680, for example, a portable data processing apparatus is provided with an I/O slot into which a radio pager can be detachably connected. When the radio pager is receiving a radio signal, the radio pager outputs a control signal to the data processing apparatus, and thereby the main clock signal supplied to the CPU of the data processing apparatus is stopped or switched to a sub clock signal of a lower frequency during the receiving period so as to avoid causing the harmonics of the main clock to influence the radio receiving characteristics. After the receiving operation is completed, the main clock signal is supplied to the CPU and thereby the CPU starts performing data processing of the received data.
SUMMARY OF THE INVENTION
In recent years, as one measure to accommodate the increasing transmission rate, a multi-level digital modulation technique such as M-ary FSK (frequency shift keying) has been employed. Especially, the 4-ary FSK modulation format is used in many wireless applications. Since the multi-level digital modulation allows a larger amount of data to be transmitted, a message of increased length of can be transmitted at a time to a radio selective call receiver such as a pager.
In the case of the radio selective call receiver, however, the received data is temporarily stored onto a memory and, after the receiving operation is completed, the received data stored in the memory is read and processed by a CPU supplied with the main clock. Therefore, when receiving a large amount of data which exceeds the capacity of the memory, the CPU has to process the received data according to the main clock during the receiving operation. This may raise the possibility that the harmonics of the main clock pulses adversely influence the radio sensitivity characteristics of the radio system.
An object of the present invention is to provide a receiver and a timing control method which can receive a digital-modulated signal with reliability and stability while processing received digital data.
Another object of the present invention is to provide a radio selective call receiver which can receive a large amount of data without effect on the receiving characteristics.
According to the invention, in a receiver having an AD converter through which a multi-level detected signal is converted into digital form, the data processing of the digital signal is performed when the AD converter does not perform AD conversion of the multi-level detected signal. Since the multi-level detected signal is input through the AD converter when the data processing is not performed, the data can be received without effect on the receiving characteristics.
According to an aspect of the present invention, a receiver includes a detector for detecting a multi-level detected signal from the digital-modulated signal and an AD converter for converting the multi-level detected signal to a digital signal at intervals determined based on the multi-level detected signal. The receiver further includes a first controller which controls a plurality of operations of the radio receiver, the operations including data processing of the digital signal, and a second controller which controls the operation timing of the first controller such that the first controller performs the data processing within a time period during which the AD converter does not perform AD conversion of the multi-level detected signal.
According to another aspect of the present invention, a radio selective call receiver further includes a decoder for decoding the digital signal to produce received data and a memory for storing the received data. A timing controller controls AD conversion timing of the AD converter such that the AD conversion is performed at intervals determined based on the multi-level detected signal. A data processor processes data to perform a plurality of operations of the radio selective call receiver, the operations including data storing and data processing of the received data, wherein the data processing of the received data is performed within a time period during which the AD conversion is not performed.
REFERENCES:
patent: 4510569 (1985-04-01), Takoa et al.
patent: 5081454 (1992-01-01), Campbell, Jr. et al.
patent: 5422807 (1995-06-01), Mitra et al.
patent: 5533062 (1996-07-01), Liberti, Jr. et al.
patent: 5790607 (1998-08-01), Burke et al.
patent: 5901149 (1999-05-01), Itakura et al.
patent: 7-99680 (1995-04-01), None
Burd Kevin M
NEC Corporation
Pham Chi
Young & Thompson
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