Radio communication apparatus having an automatic frequency control circuit for controlling a transmission frequency on the basis of a reception frequency

• US 5,444,736 A
• Filed: 07/21/1992
• Issued: 08/22/1995
• Est. Priority Date: 07/22/1991
• Status: Expired due to Term

• Current Assignee: Fujitsu Toshiba Mobile Communications Limited (Fujitsu Limited)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kawashima, Kazuhiro, Serizawa, Mutsumu
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): VO, DON NGUYEN
• Application Number:
  US07/915,674
• Time in Patent Office: 1,127 Days
• Field of Search: 375/22, 375/81, 375/97, 375/7, 375/96, 455/182.1, 455/182.2, 455/192.1, 455/192.2, 455/255, 455/256, 455/257, 455/258, 455/259, 455/264, 455/265
• US Class Current: 375/219
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H03J 7/065 the counter or frequency divider being used in a phase locked loop
• CPC Class Codes: H04B 1/403 using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency

Abstract

A radio communication apparatus comprises a detecting circuit for detecting a change of a received frequency of a radio communication channel during a communication and outputting a digital detection signal, a pulse width modulating circuit, and a smoothing circuit. The pulse width modulating circuit pulse-width modulates a pulse signal having a predetermined frequency in accordance with the digital detection signal output from the detecting circuit. The smoothing circuit smoothes the pulse-width modulated circuit output from the pulse width modulating circuit and generates an analog control signal. A transmission local oscillating frequency is controlled in accordance with the analog control signal.

Claims

1. A radio communication apparatus used in a cellular radio system in which a communication signal is transmitted through a radio communication channel established between a base station and the radio communication apparatus, comprising:

detecting means for detecting a change of a received frequency of the communication signal transmitted through the radio communication channel during a communication to produce a digital detection signal;

pulse width modulating means for pulse width modulating a pulse signal having a predetermined frequency to vary linearly with the digital detection signal to produce a linear pulse-width modulated signal;

smoothing means for smoothing the linear pulse-width modulated signal thereby generating an analog control signal;

local oscillating means for generating a local oscillating signal whose frequency changes in accordance with the analog control signal; and

mixing means for mixing the local oscillator signal with a transmission signal to produce a radio transmission signal.

2. A radio communication apparatus according to claim 1, wherein said detecting means and said pulse width modulating means are integrated together with a digital demodulating circuit for digital-demodulating a digital reception signal and outputting a digital reception baseband signal.

3. A radio communication apparatus according to claim 1, wherein said detecting means comprises storing means for storing a plurality of preset change detection patterns in accordance with the amounts of change of the received channel frequency, means for obtaining a correlation between an input digital reception signal and the change detection patterns stored in said storing means, and means for detecting an amount of frequency change of the received channel frequency on the basis of the obtained correlation.

4. A radio communication apparatus used in a cellular radio system in which a communication signal is transmitted through a radio communication channel established between a base station and the radio communication apparatus, comprising:

detecting means for detecting a change of a received frequency of the communication signal transmitted through the radio communication channel during a communication to produce a digital detection signal;

pulse width modulating means for pulse width modulating a pulse signal having a predetermined frequency to vary logarithmically with the digital detection signal to produce a log pulse-width modulated signal;

smoothing means for smoothing the log pulse-width modulated signal thereby generating an analog control signal;

local oscillating means for generating a local oscillating signal whose frequency changes in accordance with the analog control signal; and

mixing means for mixing the local oscillator signal with a transmission signal to produce a radio transmission signal.

5. A radio communication apparatus according to claim 4, wherein said detecting means and said pulse width modulating means are integrated together with a digital demodulating circuit for digital-demodulating a digital reception signal and outputting a digital reception baseband signal.

6. A radio communication apparatus according to claim 4, wherein said detecting means comprises storing means for storing a plurality of preset change detection patterns in accordance with the amounts of change of the received channel frequency, means for obtaining a correlation between an input digital reception signal and the change detection patterns stored in said storing means, and means for detecting an amount of frequency change of the received channel frequency on the basis of the obtained correlation.

7. A radio communication apparatus used in a cellular radio system in which a communication signal is transmitted through a radio communication channel established between a base station and the radio communication apparatus, comprising:

detecting means for detecting a change of a received frequency of the communication signal transmitted through the radio communication channel during a communication to produce a digital detection signal;

pulse width modulating means for pulse width modulating a pulse signal having a predetermined frequency in accordance with the digital detection signal to produce a pulse-width modulated signal;

smoothing means for smoothing the log pulse-width modulated signal thereby generating an analog control signal;

local oscillating means for generating a local oscillating signal whose frequency changes in accordance with the analog control signal; and

mixing means for mixing the local oscillator signal with a transmission signal to produce a radio transmission signal, wherein said pulse width modulating means comprises;

first pulse width modulating means for modulating the pulse signal to vary linearly with the digital detection signal to produce a linear pulse-width modulated signal;

second pulse width modulating means for modulating the pulse signal to vary logarithmically with the digital detection signal to produce a log pulse-width modulated signal;

comparing means for comparing the digital detection signal with a predetermined threshold value; and

selecting means, responsive to said comparing means, for selecting the log pulse-width modulated signal from said second pulse width modulating means when the value represented by the digital detection signal is the same as or greater than the predetermined threshold value, for selecting the linear pulse-width modulated signal from said first pulse width modulating means when the value represented by the digital detection signal is less than the predetermined threshold value, and for outputting the selected signal to said smoothing means.

8. A radio communication apparatus according to claim 7, wherein said detecting means and said pulse width modulating means are integrated together with a digital demodulating circuit for digital-demodulating a digital reception signal and outputting a digital reception baseband signal.

9. A radio communication apparatus according to claim 7, wherein said detecting means comprises storing means for storing a plurality of preset change detection patterns in accordance with the amounts of change of the received channel frequency, means for obtaining a correlation between an input digital reception signal and the change detection patterns stored in said storing means, and means for detecting an amount of frequency change of the received channel frequency on the basis of the obtained correlation.

10. A radio communication apparatus, comprising:

detecting means for detecting a change of frequency of a received radio frequency signal and outputting a digital detection signal representing the amount of the change;

pulse width modulating means for pulse width modulating a pulse signal having a predetermined frequency to vary linearly with the digital detection signal to produce a linear pulse-width modulated signal;

control signal generating means for generating an analog control signal to control a transmission frequency in accordance with the linear pulse-width modulated signal; and

radio transmission frequency generating means for generating a radio transmission frequency whose frequency varies in accordance with the analog control signal.

11. A radio communication apparatus, comprising:

detecting means for detecting a change of frequency of a received radio frequency signal and outputting a digital detection signal representing the amount of the change;

pulse width modulating means for pulse width modulating a pulse signal having a predetermined frequency to vary logarithmically with the digital detection signal to produce a log pulse-width modulated signal;

control signal generating means for generating an analog control signal to control a transmission frequency in accordance with the log pulse-width modulated signal; and

radio transmission frequency generating means for generating a radio transmission frequency whose frequency varies in accordance with the analog control signal.

12. A radio communication apparatus, comprising:

detecting means for detecting a change of frequency of a received radio frequency signal and outputting a digital detection signal representing the amount of the change;

pulse width modulating means for pulse width modulating a pulse signal having a predetermined frequency in accordance with the digital detection signal to produce a pulse-width modulated signal;

control signal generating means for generating an analog control signal to control a transmission frequency in accordance with the pulse-width modulated signal; and

radio transmission frequency generating means for generating a radio transmission frequency whose frequency varies in accordance with the analog control signal, wherein said pulse width modulating means comprises;

first pulse width modulating means for modulating the pulse signal to vary linearly with the digital detection signal to produce a linear pulse-width modulated signal;

second pulse width modulating means for modulating the pulse signal to vary logarithmically with the digital detection signal to produce a log pulse-width modulated signal;

comparing means for comparing the digital detection signal with a predetermined threshold value; and

selecting means, responsive to said comparing means, for selecting the log pulse-width modulated signal from said second pulse width modulating means when the value represented by the digital detection signal is the same as or greater than the predetermined threshold value, for selecting the linear pulse-width modulated signal from said first pulse width modulating means when the value represented by the digital detection signal is less than the predetermined threshold value, and for outputting the selected signal to said smoothing means.