Circuit and method for converting a radio frequency signal into a baseband signal

• US 5,321,852 A
• Filed: 09/24/1991
• Issued: 06/14/1994
• Est. Priority Date: 10/23/1990
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Seong, Chang-yeol
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): PHAM, CHI H
• Application Number:
  US07/764,834
• Time in Patent Office: 994 Days
• Field of Search: 455/180.1, 455/180.2, 455/180.3, 455/187.1, 455/188.1, 455/188.2, 455/189.1, 455/190.1, 455/191.1, 455/196.1, 455/197.1, 455/198.1 , 455/200.1, 455/208, 455/232.1, 455/242.1, 455/242.2, 455/243.1, 455/245.1, 455/260, 455/265, 455/318, 455/324, 453/182.1, 453/182.2, 453/192.1, 453/192.2, 453/313, 453/316
• US Class Current: 455/182.1
• CPC Class Codes: H03D 3/242 combined with means for controlling the frequency of a further oscillator, e.g. for negative frequency feedback or AFC
• CPC Class Codes: H03G 3/3068 Circuits generating control signals for both R.F. and I.F. stages
• CPC Class Codes: H03J 3/08 by varying a second parameter simultaneously with the tuning, e.g. coupling bandpass filter
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A device for converting a radio frequency signal directly to a baseband signal includes: a receiving section having a tuner for providing a tuned radio frequency signal and a phase-locked loop for providing a phase-locked signal in response to the tuned radio frequency signal; a frequency oscillating section having a voltage controlled oscillator for providing a specific frequency signal, with a same phase and frequency as the tuned radio frequency signal, in response to the phase-locked signal and a control voltage, and a phase comparator providing the control voltage by comparing the phase of the tuned radio frequency signal and the phase of the specific frequency signal; a baseband section for producing the baseband signal by mixing the tuned radio frequency signal and the specific frequency signal; and a gain control section generating a gain control signal fed back to the baseband section and a delayed gain control signal fed back to the receiving section.

Claims

1. A circuit for converting a radio frequency signal into a baseband signal, said circuit comprising:

receiving means for providing a tuned frequency signal by tuning the radio frequency signal in dependence upon a first phase-locked signal, a second phase-locked signal and a delayed gain control signal, said receiving means comprising a tuning portion and a phase-locked loop providing the first phase-locked signal, the second phase-locked signal and a third phase-locked signal in response to the tuned frequency signal; and

output means comprising;

a baseband signal portion generating the baseband signal by mixing the tuned frequency signal and a specific frequency signal comprising a same frequency and phase as said tuned frequency signal;

a gain control portion converting said baseband signal into the delayed gain control signal;

and a frequency oscillating portion comprising a voltage controlled oscillator and a phase comparator, said voltage controlled oscillator generating said specific frequency signal in response to the third phase-locked signal and a control voltage, said phase comparator providing the control voltage by comparing the phase of the tuned frequency signal and the phase of the specific frequency signal.

2. The circuit of claim 1, wherein said tuning portion comprises:

an input tuner providing an input tuner signal in response to both the radio frequency signal and the first phase-locked signal;

an amplifier providing an amplified signal by amplifying the input tuner signal in accordance with the delayed gain control signal; and

an interstage tuner providing the tuned frequency signal in response to said amplified signal and said second phase-locked signal.

3. The circuit of claim 1, wherein said gain control portion comprises:

an automatic gain control circuit and a delay circuit, said automatic gain control circuit providing the gain control signal to said baseband signal portion in response to said baseband signal and said delay circuit providing the delayed gain control signal to the receiving means in response to the gain control signal.

4. The circuit of claim 1, wherein said baseband signal portion comprises:

a mixer providing a mixed signal by mixing the tuned radio frequency signal and the specific frequency signal;

a low-pass filter providing a filtered signal by filtering the mixed signal; and

an amplifier providing the baseband signal by amplifying the filtered signal in dependence upon the gain control signal.

5. The circuit of claim 1, wherein said phase comparator further comprises:

means providing a phase compared-signal by comparing the phase of the tuned frequency signal with the phase of the specific frequency signal;

a low-pass filter providing a filtered signal by filtering the phase-compared signal; and

an amplifier providing the control voltage by amplifying the filtered signal.

6. A circuit for converting a received radio frequency signal into a baseband signal, said circuit comprising:

means for providing a tuned radio frequency signal by tuning the received radio frequency signal in response to a gain control signal being delayed and fed back from said baseband signal, said means for providing comprising phase-locked loop means for producing a first phase-locked signal in response to the tuned radio frequency signal; and

means for generating the baseband signal by mixing the tuned radio frequency signal with a specific frequency signal comprising a same frequency and phase as the tuned radio frequency signal, said means for generating comprising a voltage controlled oscillator and a phase comparator, said voltage controlled oscillator providing the specific frequency signal in response to a control voltage and the first phase-locked signal, said phase comparator producing the control voltage by comparing the phase of the specific frequency signal and the phase of the tuned radio frequency signal.

7. The circuit for converting the radio frequency signal as claimed in claim 6, wherein said means for providing said tuned radio frequency signal further comprises:

input tuning means for providing an input tuner signal by tuning the radio frequency signal in response to a second phase-locked signal from the phase-locked loop means, amplifying means for providing an amplified signal by amplifying said input tuner signal, and interstage tuning means for providing said tuned radio frequency signal by tuning said amplified signal in response to a third phase-locked signal from the phase-locked loop means.

8. The circuit for converting the radio frequency signal as claimed in claim 6, wherein the means for generating the baseband signal further comprises:

baseband producing means for converting the tuned radio frequency signal into a baseband signal, said baseband producing means comprising;

mixing means for providing a mixed signal by mixing the specific frequency signal with the tuned radio frequency signal;

first filtering means for providing a first filtered signal by filtering the mixed signal; and

first amplifying means for producing the baseband signal by amplifying the first filtered signal in response to the gain control signal;

gain control means for providing the gain control signal in response to the baseband signal, said gain control means comprising;

automatic gain control means for providing the gain control signal in response to the baseband signal; and

delay means for providing the delayed gain control signal in response to the gain control signal;

frequency oscillating means for providing the specific frequency signal in response to the control voltage and the first phase-locked signal, said frequency oscillating means comprising;

said voltage controlled oscillator;

said phase comparator;

second filtering means for providing a second filtered signal by filtering the phase-compared signal; and

second amplifying means for providing the control voltage by amplifying the second filtered signal.

9. A circuit for producing a baseband signal from a tuned radio frequency signal, said circuit comprising:

means for providing a specific frequency signal, comprising an identical frequency and an identical phase of the tuned radio frequency signal, in response to a phase-locked signal and a control voltage, said means for providing comprising;

voltage controlled oscillating means for producing the specific frequency signal in response to the control voltage and the phase-locked signal; and

phase comparing means for providing the control voltage by comparing the phase of the tuned radio frequency signal with the phase of the specific frequency signal; and

means for producing the baseband signal by mixing the specific frequency signal and the tuned radio frequency signal.

10. A broadcast signal receiving apparatus producing a baseband signal having a same phase and frequency as a radio frequency signal, said apparatus comprising:

receiving means for providing a tuned radio frequency signal by tuning the radio frequency signal, said receiving means comprising;

a tuner comprising a first input terminal for receiving the radio frequency signal, and an output terminal providing the tuned radio frequency signal; and

a phase-locked loop comprising an input terminal for receiving the tuned radio frequency signal, a first output terminal for providing a first phase-locked signal to the tuner, a second output terminal for providing a second phase-locked signal to the tuner and a third output terminal for providing a third phase-locked signal; and

output means for producing the baseband signal, said output means comprising;

a baseband circuit converting the tuned radio frequency signal into a baseband signal;

a gain control circuit comprising an input terminal for receiving the baseband signal, a first output terminal for providing a gain control signal to a second input terminal of the baseband circuit, and a second output terminal for providing said gain control signal being delayed to a second input terminal of the tuner; and

a frequency oscillating circuit comprising a first input terminal for receiving the tuned radio frequency signal, a second input terminal for receiving the third phase-locked signal, and an output terminal for providing the specific frequency signal to a third input terminal of the baseband circuit.

11. A broadcast signal direct-receiving circuit comprising:

receiving means for providing a tuned radio frequency signal by tuning a radio frequency signal, said receiving means comprising;

tuning means for producing said tuned radio frequency signal, said tuning means frequency signal, said receiving means comprising;

tuning means for producing said tuned radio frequency signal, said tuning means comprising an input tuner with a first input terminal for receiving the radio frequency signal and an output terminal for providing an input tuner signal, a first amplifier with a first input terminal for receiving the input tuner signal and an output terminal for providing a first amplified signal, and an interstage tuner with a first input terminal for receiving the first amplified signal and an output terminal for providing the tuned radio frequency signal; and

phase-locked loop means comprising an input terminal for receiving the tuned radio frequency signal, a first output terminal for providing a first phase-locked signal to a second input terminal of the input tuner, a second output terminal for providing a second phase-locked signal to a second input terminal of the interstage tuner, and a third output terminal for providing a third phase-locked signal; and

output means for producing a baseband signal in response to the tuned radio frequency signal and the third phase-locked signal, said output means comprising;

a baseband circuit comprising a mixer with a first input terminal for receiving the tuned radio frequency signal and an output terminal for providing a mixed signal, a first filter with an input terminal for receiving the mixed signal and an output terminal for providing a first filtered signal, and a second amplifier having a first input terminal for receiving the first filtered signal and an output terminal for providing the baseband signal;

a gain control circuit comprising an automatic gain control section and a delay section, said automatic gain control section having an input terminal for receiving the baseband signal and an output terminal for providing an automatic gain control signal to a second input terminal of the second amplifier, said delay section having an input terminal for receiving the automatic gain control signal and an output terminal for providing said automatic gain control signal being delayed to a second input terminal of the first amplifier; and

a frequency oscillating circuit comprising;

a voltage controlled oscillator having a first input terminal for receiving the third phase-locked signal, a second input terminal for receiving a control voltage and an output terminal for providing a specific frequency signal to a second input terminal of the mixer;

a phase comparator having a first input terminal for receiving the specific frequency signal, a second input terminal for receiving the tuned radio frequency signal and an output terminal for providing a phase-compared signal;

a second filter having an input terminal for receiving the phase-compared signal and an output terminal for providing a second filtered signal; and

a third amplifier having an input terminal receiving the second filtered signal and an output terminal for providing the control voltage to a second input terminal of the voltage controlled oscillator.

12. A broadcast signal receiving apparatus for producing a baseband signal having a same phase and frequency as a tuned radio frequency signal, said apparatus comprising:

a phase-locked loop providing a phase-locked signal in dependence upon the tuned radio frequency signal;

means for producing a specific frequency signal, comprising a same frequency and phase of the tuned radio frequency, in response to the tuned radio frequency signal and said phase-locked signal, said means for producing comprising;

voltage controlled oscillating means for providing the specific frequency signal in response to the phase-locked signal and a control voltage; and

phase comparing means for providing the control voltage by comparing the phase of the tuned radio frequency signal and the phase of the specific frequency signal; and

means for producing the baseband signal by mixing the specific frequency signal with the tuned radio frequency signal.

13. A circuit for producing a baseband signal from a tuned radio frequency signal, said circuit comprising:

a phase-locked loop providing a phase-locked signal in dependence upon the tuned radio frequency signal;

means for producing a specific frequency signal in response to said phase-locked loop signal and in response to a phase comparison of the tuned radio frequency signal and the specific frequency signal; and

means for producing the baseband signal by mixing the specific frequency signal with the tuned radio frequency signal.

14. A method of converting a radio frequency signal into a baseband signal, said method comprising the steps of:

providing a tuned radio frequency signal by tuning the radio frequency signal in accordance with a phase-locked signal of a phase-locked loop;

generating a specific frequency signal corresponding in phase and frequency to the tuned radio frequency signal, in response to the phase-locked signal and a control voltage, and providing said control voltage by comparing the phase of the tuned radio frequency signal with the phase of the phase-locked signal; and

producing the baseband signal by mixing the specific frequency signal and the tuned radio frequency signal.

15. The method of claim 14, wherein the tuning step comprises the step of:

tuning one of a VHF component and an UHF component of the radio frequency signal.

16. A method of producing a baseband signal from a tuned radio frequency signal, said method comprising the steps of:

generating a phase-locked signal of the tuned radio frequency signal;

providing a control voltage corresponding to a comparison of a phase of the tuned radio frequency signal and a phase of a specific frequency signal;

producing the specific frequency signal comprising a same phase and frequency as the tuned radio frequency signal in response to the phase-locked signal and the control voltage; and

producing the baseband signal by mixing the specific frequency signal with the tuned radio frequency signal.

17. A method of converting a radio frequency signal to a baseband signal, said method comprising the steps of:

tuning said radio frequency signal in response to a gain control signal being delayed;

producing a phase-locked signal in response to the tuned radio frequency signal;

producing a control signal by comparing a phase of a specific frequency signal with a phase of the tuned radio frequency signal;

producing the specific frequency signal in a voltage controlled oscillator in response to the phase-locked signal and the control signal; and

producing the baseband signal by mixing the specific frequency signal with the tuned radio frequency signal and controlling a gain of the baseband signal according to the gain control signal.