Telecommunications – Receiver or analog modulated signal frequency converter – Noise or interference elimination
Reexamination Certificate
1999-02-09
2001-04-17
Maung, Nay (Department: 2681)
Telecommunications
Receiver or analog modulated signal frequency converter
Noise or interference elimination
C455S063300, C375S349000
Reexamination Certificate
active
06219534
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio communication apparatus used for a radio receiver such as a cellular phone. Especially, the present invention relates to a circuit system which suppresses an interference wave automatically and is able to transfer data at high speed.
2. Related Background Art
The cellular phone has prevailed rapidly. There are an analog system and a digital system for the cellular phone. The digital system can use frequency band more efficiently than the analog system, and the digital system surpasses the analog system in capability for security. Because of this, it is predicted that the digital system becomes predominant in future.
The digital system converts a voice signal into code information and transfers the information by radio frequency. Because of this, the digital system has a feature in that it hardly suffers the influence of noise. On the other hand, in order to increase the number of channels available for the cellular phone, frequency band per a channel has to be narrowed. However, when the frequency band per a channel is narrowed, each channel easily suffers the influence of the noise. Because of this, a conventional circuit which suppresses an image interference wave by using a quadrature mixer and a ±45° phase shifter has been known.
In order to suppress the image interference wave, it is necessary to control a gain difference and a phase difference between an I signal as an in-phase component and a Q signal as a quadrature component. However, the conventional circuit has initially set the gain difference and the phase difference only by hand. The reason is because differential signals of the gain difference and the phase difference is very little, for example, less than 1 dB or 2°, and because a technique which detects such a micro signal with high precision and controls the gain difference and the phase difference has not been established. Because of this, the gain difference and the phase difference had to be controlled by hand. Accordingly, it has taken a long time to control the gain difference and the phase difference, and the conventional circuit could not suppress the image interference wave at will.
On the other hand,
FIG. 17
is a diagram which explains TDMA (time-division multiple access) in a mobile communication system called a GSM system which is prevailing in Europe. As shown in
FIG. 17
, the GSM system transfers data at each time-slot. A sending timing fRX of a mobile station (MS) which communicates with a base station and a receiving timing fTX is being shown in FIG.
17
.
The mobile station receives the data at a time R
1
and sends data at a time T
1
. The mobile station receives the next data at a time R
2
after 8 time-slot of the time R
1
. Between times R
6
and R
7
, a period which monitors another channel is provided.
The mobile station has to perform both of a voice communication and a data transfer within one time-slot. Because of this, the capability of transferring data is inevitably limited by a time length per one time-slot.
Accordingly, in order to transfer a large amount of data at high speed, a bit rate in a time-slot has to be raised, or data transfer has to be performed by using a plurality of slots. It is difficult to realize the former because of restriction of the conventional system. In the case of the latter, because an interval between the sending period and the receiving period becomes narrow inevitably, a frequency synthesizer used in the radio communication apparatus has to be changed quickly. That is, it is necessary to use an expensive frequency synthesizer.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a radio communication apparatus which is able to suppress a interference wave by an automatic control.
Furthermore, an another object of the present invention is to provide a radio communication apparatus which is able to transfer data at high speed without using a frequency synthesizer capable of changing the frequency quickly.
In order to achieve the foregoing object, a radio communication apparatus, comprising:
a first in-phase/quadrature component separating circuit for separating a selecting frequency component included in a signal received by an antenna into an in-phase component signal and a quadrature component signal;
a first A/D converter for outputting a digital signal obtained through an A/D converter of the in-phase component signal separated by said first in-phase/quadrature component separating circuit;
a second A/D converter for outputting a digital signal obtained through an A/D conversion of the quadrature component signal separated by said first in-phase/quadrature component separating circuit;
a detecting circuit for performing a detecting process based on the digital signals outputted from said first and second A/D converters;
a second in-phase/quadrature component separating circuit for separating the digital signal outputted from said first A/D converter into the in-phase component signal and the quadrature component signal;
a third in-phase/quadrature component separating circuit for separating the digital signal outputted from said second A/D converter into the in-phase component signal and the quadrature component signal; and
an interference wave suppression control circuit for controlling at least one of reference voltages of said first and second A/D converters based on each signal separated by said second and third in-phase/quadrature component separating circuits, so that the gain difference of each digital signal outputted from said first and second A/D converters is equal to or less than a prescribed value.
Furthermore, a radio communication apparatus, comprising:
a first in-phase/quadrature component separating circuit for separating a selecting frequency component included in a signal received by an antenna into an in-phase component signal and a quadrature component signal;
a signal selecting circuit for selecting either the in-phase component signal or the quadrature component signal separated by said first in-phase/quadrature component separating circuit;
an A/D converter for outputting a digital signal obtained through an A/D conversion of the signal selected by said signal selecting circuit;
a delay circuit for delaying the digital signal outputted from said A/D converter;
a second in-phase/quadrature component separating circuit for separating the output of said delay circuit into an in-phase component signal and the quadrature component signal;
a third in-phase/quadrature component separating circuit for separating the digital signal outputted from said A/D converter into an in-phase component signal and a quadrature component signal; and
an interference wave suppression control circuit for controlling the reference voltage of said A/D converter based on each signal separated by said second and third in-phase/quadrature component separating circuits, so that a gain difference of each digital signal outputted from said A/D converter or said delay circuit is equal to or less than a prescribed value.
Furthermore, a radio communication apparatus for transmitting signals with two different frequency bands, comprising:
a first local oscillator for outputting a first local oscillating signal;
a frequency divider for dividing a frequency of said first local oscillating signal;
a first frequency converter for converting a signal with a first frequency band received by an antenna into an intermediate frequency signal with a prescribed frequency, based on the signal with the frequency divided by said frequency divider; and
a second frequency converter for converting a signal with a second frequency band received by the antenna into the intermediate frequency signal with the prescribed frequency, based on the signal with the frequency divided by said frequency divider, wherein
said first local oscillator outputs said first local oscillating signal with an equal frequency, even if performing transmission and reception.
According to the present invention, in a radio communic
Kabushiki Kaisha Toshiba
Maung Nay
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vuong Quochien B.
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