Radio tele-communication device having function of variably controlling received signal level

• US 5,408,698 A
• Filed: 03/25/1992
• Issued: 04/18/1995
• Est. Priority Date: 03/26/1991
• 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): Urban, Edward F.
• Application Number:
  US07/856,249
• Time in Patent Office: 1,119 Days
• Field of Search: 455/234.1, 455/234.2, 455/240.1, 455/249.1, 455/245.1, 455/246.1, 375/80, 375/94, 375/95, 375/98, 375/22
• US Class Current: 455/245.1
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence

Abstract

A level changing circuit is provided in a reception signal path for a radio signal and a level detection circuit and a pulse width modulation circuit are provided in a gain control circuit. A level corresponding to the amplitude level of a signal processed by a digital demodulation circuit is detected by the level detection circuit and a pulse signal whose pulse width is modulated according to the detected signal level is generated from the pulse width modulation circuit. Then, a gain control signal having a D.C. level corresponding to the pulse signal is generated and the gain of the level changing circuit is controlled according to the gain control signal, thereby making it possible to control the level of the received signal.

Claims

1. A radio-telecommunication device

frequency-converting means for receiving a radio signal transmitted via a radio channel and for frequency-converting the received radio signal into a signal having a frequency lower than the received radio signal;

variable gain-type level changing means, responsive to a gain control signal, for permitting the amplitude of the signal derived from said frequency converting means to be changed;

demodulating means for demodulating the signal output from said level changing means to produce a digital base band signal as a first output signal, said demodulating means comprising converting means for converting the signal output from said level changing means into a digital signal, means for performing a digital demodulation of the digital signal to produce a demodulated signal, and outputting means for outputting a second output signal obtained from the demodulated signal;

level detecting means for detecting amplitude information corresponding to the amplitude level of the signal output from said level changing means based on the second output signal from said outputting means;

pulse width modulation means for generating a pulse signal whose pulse width is modulated according to the detected amplitude information; and

gain control signal generating means for generating a gain control signal having a D.C. level corresponding to the pulse width of the pulse signal and for supplying the gain control signal to said level changing means to control the gain thereof.

2. A radio tele-communication device according to claim 1, wherein said frequency converting means includes a plurality of series-connected frequency converting circuits and said level changing means is coupled to a last-stage frequency converting circuit among said plurality of frequency converting circuits.

3. A radio tele-communication device according to claim 1, wherein said outputting means includes synchronizing signal detecting means for detecting preset synchronizing signals periodically set in said radio signal and outputting the detected signals, and said level detecting means detects the peak value of the detected signals output from said synchronizing signal detecting means and outputting the detected peak value as said amplitude information.

4. A radio tele-communication device according to claim 1, wherein said demodulation means includes synchronizing signal detecting means for detecting preset synchronizing signals periodically set in said radio signal and outputting the detected signals, and said level detecting means includes peak value detecting means for detecting the peak values of detected signals output from said synchronizing signal detecting means and means for deriving an average value of a plurality of peak values detected by said peak value detecting means and outputting the average value as said amplitude information.

5. A variable gain control circuit provided in a device having a digital processing circuit for converting an input signal into a digital signal and then demodulating the digital signal, comprising:

level changing means preceding said digital processing circuit, for changing the amplitude level of a signal supplied thereto to produce an output signal having a changed amplitude level and supplying the output signal to said digital processing circuit as an input signal;

level detecting means for detecting amplitude information corresponding to the amplitude level of the output signal of said level changing means based on the digital signal;

pulse width modulation means for outputting a pulse signal whose pulse width is modulated according to the amplitude information detected by said level detecting means; and

gain control means for generating a gain control signal having a D.C. level corresponding to the pulse width of the pulse signal output from said pulse width modulation means and for controlling the gain of said level changing means according to the gain control signal.

6. A variable gain controlling method applied to a device having a digital processing circuit for converting an input signal into a digital signal and then subjecting the same to a predetermined processing, comprising the steps of:

changing the amplitude level of a signal by use of a level changing means to produce an output signal having a changed amplitude level and supplying the output signal to said digital processing circuit as an input signal;

detecting amplitude information corresponding to the amplitude level of the output signal from said level changing means based on the digital signal;

outputting a pulse signal whose pulse width is modulated according to the detected amplitude information;

generating a gain control signal having a D.C. level corresponding to the pulse width of the pulse signal; and

controlling the gain level of said level changing means according to the D.C. level of the gain control circuit.

7. A radio-telecommunication device comprising:

a frequency converter for frequency-converting a received radio signal having a first carrier frequency into a frequency-converted radio signal having a second carrier frequency lower than the first carrier frequency;

a variable gain amplifier, responsive to a gain control signal, for amplifying the frequency-converted radio signal;

an analog-to-digital converter for converting the amplified frequency-converted radio signal to a digital signal;

a demodulator for demodulating the digital signal to produce a demodulated digital signal;

a level detector for detecting amplitude information corresponding to the amplitude level of the amplified frequency-converted radio signal based on the demodulated digital signal;

a pulse width modulator for generating a pulse signal whose pulse width is modulated according to the detected amplitude information; and

gain control signal generation means for generating a gain control signal having a level corresponding to the pulse width of the pulse signal, wherein the gain control signal is supplied to said variable gain amplifier to control the gain thereof.

8. The radio-telecommunication device according to claim 7, wherein said demodulator comprises a quadrature demodulator.

9. The radio-telecommunication device according to claim 8, further comprising a delay detector for generating base band data from the demodulated digital signal and for outputting the base band data to an error correction demodulating circuit.

10. The radio-telecommunication device according to claim 9, further comprising a synchronizing circuit for detecting a slot synchronization signal from the demodulated digital signal.

11. A radio-telecommunication device comprising:

a frequency converter for frequency-converting a received radio signal having a first carrier frequency into a frequency-converted radio signal having a second carrier frequency lower than the first carrier frequency;

a variable gain amplifier, responsive to a gain control signal, for amplifying the frequency-converted radio signal;

an analog-to-digital converter for converting the amplified frequency-converted radio signal to a digital signal;

a demodulator for demodulating the digital signal to produce a demodulated digital signal;

a correlation circuit for generating a correlation signal from the demodulated digital signal;

a peak detector for detecting peak values of said correlation signal;

an averaging circuit for generating an average peak value from the peak values detected by said peak detector;

a pulse width modulator for generating a pulse signal whose pulse width is modulated according to the average peak value; and

gain control signal generation means for generating a gain control signal having a level corresponding to the pulse width of the pulse signal, wherein the gain control signal is supplied to said variable gain amplifier to control the gain thereof.

12. The radio-telecommunication device according to claim 11, wherein said demodulator comprises a quadrature demodulator.

13. The radio-telecommunication device according to claim 12, further comprising a delay detector for generating base band data from the demodulated digital signal and for outputting the base band data to an error correction demodulating circuit.

14. The radio-telecommunication device according to claim 13, wherein said correlation circuit detects a slot synchronizing signal in the demodulated digital signal.

15. The radio-telecommunication device according to claim 14, wherein said correlation circuit comprises a finite impulse response filter.

16. The radio-telecommunication device according to claim 15, further comprising a control circuit for outputting timing control signals, and wherein said peak detector detects the peak value of the correlation signal in synchronism with the timing control signals.

17. The radio-telecommunication device according to claim 11, wherein said correlation circuit detects a slot synchronizing signal in the demodulated digital signal.

18. The radio-telecommunication device according to claim 13, wherein said correlation circuit comprises a finite impulse response filter.

19. The radio-telecommunication device according to claim 11, further comprising a control circuit for outputting timing control signals, and wherein said peak detector detects the peak value of the correlation signal in synchronism with the timing control signals.