Bandpass phase tracker with hilbert transformation before analog-to-digital conversion

• US 6,301,312 B1
• Filed: 11/09/1999
• Issued: 10/09/2001
• Est. Priority Date: 07/10/1997
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Limberg, Allen LeRoy
• Primary Examiner(s): Ghebretinsae, Temesghen
• Application Number:
  US09/436,705
• Time in Patent Office: 700 Days
• Field of Search: 375/324, 375/326, 375/321, 375/270, 329/304, 455/324, 348/725, 348/726
• US Class Current: 375/326
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

Abstract

The tuner in a digital TV receiver converts received signal to a penultimate intermediate-frequency signal. Penultimate local oscillations are supplied in a first phasing and in a second phasing in quadrature therewith, for heterodyning with the penultimate IF signal in first and second mixers respectively to generate real and imaginary components of an ultimate intermediate-frequency signal. The first and second mixers are of a switching type, switching in respective response to the penultimate local oscillations as supplied in first and in second phasing. First analog-to-digital conversion circuitry containing a number N of analog-to-digital converters digitizes the real component of the ultimate IF signal on an N-phase basis, N being at least one. Second analog-to-digital conversion circuitry, which contains a number N of analog-to-digital converters, digitizes the imaginary component of the ultimate IF signal on an N-phase basis. A complex digital carrier signal is generated at the frequency of the radio carrier wave as translated to the ultimate IF signal band. Synchrodyning circuitry responds to the complex digital carrier signal supplied as ultimate local oscillations, and to the digital samples of the real and imaginary components of the ultimate IF signal, for recovering in-phase and quadrature-phase components of baseband signal.

Claims

1. In a digital television signal receiver for use within a television system in which a plurality of transmitters each transmit via a respective one of a plurality of channels with different respective frequency allocations, each said transmitter transmitting a respective radio carrier wave with amplitude-modulation that codes in multiple-amplitude-level symbols thereof a respective digital signal descriptive of television information, said multiple-amplitude-level symbols occurring at a symbol rate or baud rate, circuitry comprising:

a tuner for selecting for reception the radio carrier wave in one of said plurality of channels and frequency converting the amplitude-modulated radio carrier wave so selected to a penultimate intermediate-frequency signal in a penultimate intermediate-frequency band;

a source of penultimate local oscillations supplied in a first phasing and in a second phasing in quadrature with said first phasing for heterodyning with said penultimate intermediate-frequency signal, said penultimate local oscillations being of a frequency that will heterodyne with said penultimate intermediate-frequency signal to generate within an ultimate intermediate-frequency band an amplitude-modulated carrier the carrier frequency of which is offset from zero frequency by an offset frequency that is sufficiently large as to prevent folding of the frequency spectrum of said amplitude-modulated carrier within said ultimate intermediate-frequency band at frequency below that corresponding to the Nyquist frequency for said multiple-amplitude-level symbols;

first and second mixers connected to receive said penultimate intermediate-frequency signal for said heterodyning with said penultimate local oscillations, said first mixer heterodyning said penultimate intermediate-frequency signal with said penultimate local oscillations as supplied in said first phasing for supplying a real component of said ultimate intermediate-frequency signal, and said second mixer heterodyning said penultimate intermediate-frequency signal with said penultimate local oscillations as supplied in said second phasing for supplying an imaginary component of said ultimate intermediate-frequency signal;

a first lowpass filter for separating said real component of said ultimate intermediate-frequency signal from its image to generate a first lowpass filter response within said ultimate intermediate-frequency band;

a second lowpass filter for separating said imaginary component of said ultimate intermediate-frequency signal from its image to generate a second lowpass filter response within said ultimate intermediate-frequency band;

a sample clock generator for generating a sample clock signal comprising recurrent pulses, said recurrent pulses being generated at a sample rate higher than said symbol rate by a factor larger than one;

first analog-to-digital conversion circuitry timed by said sample clock generator for digitizing said first lowpass filter response to generate as an output signal thereof digitized samples of said real component of said ultimate intermediate-frequency signal supplied at said sample rate, said first analog-to-digital conversion circuitry containing a number N of analog-to-digital converters for digitizing said first lowpass filter response on an N-phase basis, N being at least one;

second analog-to-digital conversion circuitry timed by said sample clock generator for digitizing said second lowpass filter response to generate as an output signal thereof digitized samples of said imaginary component of said ultimate intermediate-frequency signal supplied at said sample rate, said second analog-to-digital conversion circuitry containing a number N of analog-to-digital converters for digitizing said second lowpass filter response on an N-phase basis;

a source of complex digital signal descriptive of ultimate local oscillations at the carrier frequency of said ultimate intermediate-frequency signal; and

first digital synchrodyning circuitry responsive to the digitized samples of said real and imaginary components of said ultimate intermediate-frequency signal and to said complex digital signal supplied to said first digital synchrodyning circuitry as ultimate local oscillations, for recovering an in-phase baseband signal resulting from demodulation of said amplitude modulation of said radio carrier wave selected by said tuner for reception.

2. The circuitry of claim 1, wherein N is more than one.

3. The circuitry of claim 1, wherein N is more than one, and wherein each said analog-to-digital converter is of successive binary approximation type.

4. The circuitry of claim 1, wherein said first and second mixers are of a switching type.

5. The circuitry of claim 1, wherein the uppermost frequency of said ultimate intermediate-frequency band is at most several megaHertz.

6. The circuitry of claim 1, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.

7. The circuitry of claim 1, wherein said source of complex digital signal descriptive of ultimate local oscillations at the carrier frequency of said ultimate intermediate-frequency signal comprises:

an address counter for counting said recurrent pulses to generate an address count; and

read-only memory addressed at least in part by said address count for generating said complex digital signal descriptive of ultimate local oscillations at the carrier frequency of said ultimate intermediate-frequency signal.

8. The circuitry of claim 1, wherein said circuitry further comprises:

second digital synchrodyning circuitry responsive to the digitized samples of said real and imaginary components of said ultimate intermediate-frequency signal, and to said complex digital signal descriptive of ultimate local oscillations at the carrier frequency of said ultimate intermediate-frequency signal, for generating a quadrature-phase baseband signal.

9. The circuitry of claim 8, wherein said circuitry further comprises:

a local oscillator included within said tuner for supplying oscillations used in frequency conversion of the amplitude-modulated radio carrier wave selected for reception to generate said penultimate intermediate-frequency signal, said local oscillator being of a type in which the frequency and phase of said oscillations are controlled in response to an automatic-frequency-and-phase-control signal; and

circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal.

10. The circuitry of claim 9, wherein said circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal comprises:

an analog lowpass filter connected for applying its response to said local oscillator as said automatic-frequency-and-phase-control signal; and

digital-to-analog circuitry for converting said quadrature-phase baseband signal to an analog input signal for said analog lowpass filter.

11. The circuitry of claim 10, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.

12. The circuitry of claim 9, wherein said circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal comprises:

a multiplier for multiplying said quadrature-phase baseband signal by said in-phase baseband signal to generate a product signal;

an analog lowpass filter connected for applying its response to said local oscillator as said automatic-frequency-and-phase-control signal; and

digital-to-analog circuitry for converting said product signal to an analog input signal for said analog lowpass filter.

13. The circuitry of claim 12, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.

14. The circuitry of claim 8, wherein said source of penultimate local oscillations is of a type in which the frequency and phases of said penultimate local oscillations are controlled in response to an automatic-frequency-and-phase-control signal, and wherein said automatic-frequency-and-phase-control signal is developed from said quadrature-phase baseband signal.

15. The circuitry of claim 14, further comprising circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal, wherein said circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal comprises:

an analog lowpass filter connected for applying its response, as said automatic-frequency-and-phase-control signal, to said source of penultimate local oscillations; and

digital-to-analog circuitry for converting said quadrature-phase baseband signal to an analog input signal for said analog lowpass filter.

16. The circuitry of claim 15, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.

17. The circuitry of claim 14, further comprising circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal, wherein said circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal comprises:

a multiplier for multiplying said quadrature-phase baseband signal by said in-phase baseband signal to generate a product signal;

an analog lowpass filter connected for applying its response, as said automatic-frequency-and-phase-control signal, to said source of penultimate local oscillations; and

digital-to-analog circuitry for converting said product signal to an analog input signal for said analog lowpass filter.

18. The circuitry of claim 17, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.

19. The circuitry of claim 1, wherein said circuitry further comprises:

a first digital bandpass filter of linear-phase finite-impulse-response type receiving as its input signal said digitized samples of said real component of said ultimate intermediate-frequency signal and supplying as its output signal digitized samples of a real component of an uinmodulated pilot carrier wave as translated in frequency to said ultimate intermediate-frequency band and separated from other portions of said real component of said ultimate intermediate-frequency signal;

a second digital bandpass filter of linear-phase finite-impulse-response type receiving as its input signal said digitized samples of said imaginary component of said ultimate intermediate-frequency signal and supplying as its output signal digitized samples of an imaginary component of said unmodulated pilot carrier wave as translated in frequency to said ultimate intermediate-frequency band and separated from other portions of said imaginary component of said ultimate intermediate-frequency signal;

second digital synchrodyning circuitry, responsive to said complex digital carrier signal supplied thereto as ultimate local oscillations and to said output signals of said first and second digital bandpass filters, for generating a quadrature-phase baseband signal.

20. The circuitry of claim 19, wherein said circuitry further comprises:

a local oscillator included within said tuner for supplying oscillations used in frequency conversion of the amplitude-modulated radio carrier wave selected for reception to generate said penultimate intermediate-frequency signal, said local oscillator being of a type in which the frequency and phase of said oscillations are controlled in response to an automatic-frequency-and-phase-control signal; and

circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal.

21. The circuitry of claim 20, wherein said circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal comprises:

an analog lowpass filter connected for applying its response to said local oscillator as said automatic-frequency-and-phase-control signal; and

digital-to-analog circuitry for converting said quadrature-phase baseband signal to an analog input signal for said analog lowpass filter.

22. The circuitry of claim 21, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.

23. The circuitry of claim 19, wherein said source of penultimate local oscillations is of a type in which the frequency and phases of said penultimate local oscillations are controlled in response to an automatic-frequency-and-phase-control signal, and wherein said automatic-frequency-and-phase-control signal is developed from said quadrature-phase baseband signal.

24. The circuitry of claim 23, further comprising circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal, wherein said circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase baseband signal comprises:

an analog lowpass filter connected for applying its response to said local oscillator as said automatic-frequency-and-phase-control signal; and

digital-to-analog circuitry for converting said quadrature-phase baseband signal to an analog input signal for said analog lowpass filter.

25. The circuitry of claim 24, further comprising:

a spectrum filter supplying a response to said in-phase baseband signal; and

a symbol decoder responsive to the response of said spectrum filter for decoding said multiple-amplitude-level symbols of said vestigial-sideband amplitude modulation of the radio carrier wave selected by said tuner for reception.