Wide band zero if quadrature demodulator using a intermediate frequency and a single local oscillator

• US 5,761,615 A
• Filed: 05/31/1995
• Issued: 06/02/1998
• Est. Priority Date: 05/31/1995
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Jaffee, James I.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): TO, DORIS HA
• Application Number:
  US08/456,985
• Time in Patent Office: 1,098 Days
• Field of Search: 455/314, 455/313, 455/323, 455/326, 455/334, 455/337, 455/338, 455/76, 455/183.1, 455/86, 455/303, 455/304, 455/305, 455/296, 455/324, 455/216, 455/207, 329/308, 329/306, 329/316, 375/329, 375/331, 375/332, 375/376, 375/327
• US Class Current: 455/314
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A low power zero-IF selective call receiver has a local oscillator (106) that generates an injection signal for a first mixer (104) and a pair of quadrature phase related injection signals (122, 124) for a pair of second mixers (112, 114). The first mixer converts the received carrier signal (102) to an intermediate signal (108). A digital phase shifter/divider (116) coupled to the local oscillator (106) generates the pair of quadrature phase related injection signals (122, 124) at the frequency of the intermediate signal (108) which also equals the frequency of the local oscillator (106) divided by an integer greater then 1. The pair of second mixers (112, 114) coupled to the digital phase shifter/divider (116) converts the in and quadrature phase components (122, 124) of the intermediate signal (108) to respective in and quadrature phase baseband signals (126, 128).

Claims

1. A low power zero-IF selective call receiver, comprising:

a local oscillator that generates an injection signal at a first frequency (f_LO);

a first mixer coupled to the local oscillator for converting a received carrier signal of a second frequency (f_C) to an intermediate signal of a third frequency (f_IF) in response to the injection signal at the first frequency (f_LO), where the third frequency (f_IF) associated with the intermediate signal is one of a sum or a difference of the first (f_LO) and second (f_C) frequencies;

a digital phase shifter/divider coupled to the local oscillator and to the first mixer, the digital phase shifter/divider generating a pair of quadrature phase related injection signals at the third frequency (f_IF) which is the first frequency (f_LO) divided by an integer greater than 1;

a pair of second mixers coupled to the digital phase shifter/divider and the first mixer, the pair of second mixers converting an in phase component of the intermediate signal to an in phase baseband signal and a quadrature component of the intermediate signal to a quadrature baseband signal in response to an in phase and quadrature component of the pair of quadrature phase related injection signals, respectively.

2. The low power zero-IF selective call receiver according to claim 1 wherein the local oscillator comprises a discrete crystal controlled single frequency oscillator.

3. The low power zero-IF selective call receiver according to claim 1 wherein the local oscillator comprises a frequency synthesized crystal controlled oscillator.

4. The low power zero-IF selective call receiver according to claim 1 wherein the local oscillator comprises a frequency synthesized resonator controlled oscillator.

5. The low power zero-IF selective call receiver according to claim 1 wherein the first mixer comprises a non-linear semiconductor mixer.

6. The low power zero-IF selective call receiver according to claim 1 wherein the first mixer comprises a switching mixer.

7. The low power zero-IF selective call receiver according to claim 1 wherein the digital phase shifter/divider comprises a Johnson counter.

8. The low power zero-IF selective call receiver according to claim 1 wherein the second mixers comprise non-linear semiconductor mixers.

9. The low power zero-IF selective call receiver according to claim 1 wherein the second mixers comprise switching mixers.

10. The low power zero-IF selective call receiver according to claim 1 wherein the local oscillator, first mixer, digital phase shifter/divider, and pair of second mixers are fabricated as a single integrated circuit.

11. The low power zero-IF selective call receiver according to claim 1 wherein the third frequency (f_IF) is the first frequency (f_LO) divided by 4.

12. A low power zero-IF selective call receiver, comprising:

a local oscillator that generates an injection signal at a first frequency for converting a received carrier signal at a second frequency to an intermediate signal at a third frequency;

a digital phase shifter/divider coupled to the local oscillator, the digital phase shifter/divider generating at the third frequency, an in phase injection signal and a quadrature phase injection signal;

a first mixer coupled to the local oscillator and the digital phase shifter/divider, the first mixer converting the received carrier signal to an intermediate signal at the third frequency in response to the injection signal at the first frequency, the third frequency being one of a sum or a difference of the first and second frequencies and further being equal to the first frequency divided by an integer greater than 1;

a second mixer coupled to the first mixer and the digital phase shifter/divider, the second mixer converting an in phase component of the intermediate signal to an in phase baseband signal in response to the in phase injection signal; and

a third mixer coupled to the first mixer and the digital phase shifter/divider, the third mixer converting a quadrature component of the intermediate signal to a quadrature baseband signal in response to the quadrature phase injection signal.

13. The low power zero-IF selective call receiver according to claim 12 wherein the local oscillator comprises a discrete crystal controlled single frequency oscillator.

14. The low power zero-IF selective call receiver according to claim 12 wherein the local oscillator comprises a frequency synthesized crystal controlled oscillator.

15. The low power zero-IF selective call receiver according to claim 12 wherein the local oscillator comprises a frequency synthesized resonator controlled oscillator.

16. The low power zero-IF selective call receiver according to claim 12 wherein the first mixer comprises a non-linear semiconductor mixer.

17. The low power zero-IF selective call receiver according to claim 12 wherein the first mixer comprises a switching mixer.

18. The low power zero-IF selective call receiver according to claim 12 wherein the digital phase shifter/divider comprises a Johnson counter.

19. The low power zero-IF selective call receiver according to claim 12 wherein the second mixer comprises a non-linear semiconductor mixer.

20. The low power zero-IF selective call receiver according to claim 12 wherein the second mixer comprises a switching mixer.

21. The low power zero-IF selective call receiver according to claim 12 wherein the third mixer comprises a non-linear semiconductor mixer.

22. The low power zero-IF selective call receiver according to claim 12 wherein the third mixer comprises a switching mixer.

23. The low power zero-IF selective call receiver according to claim 12 wherein the in phase injection signal and the quadrature injection signal are each a pair signals of opposite phase and electrically balanced with respect to ground for the purpose of reducing electromagnetic interference due to unwanted radiation and coupling of said signals.

24. The low power zero-IF selective call receiver according to claim 12 wherein the local oscillator, first mixer, digital phase shifter/divider, second mixer, and third mixer are fabricated as a single integrated circuit.

25. The low power zero-IF selective call receiver according to claim 12 wherein the third frequency is the first frequency divided by 4 and further being equal to one of a sum or a difference of the first and second frequencies.

26. A low power zero-IF selective call receiver, comprising:

a first mixer receiving a carrier signal at a second frequency, and in response to a local oscillator injection signal at a first frequency, producing a walking intermediate frequency signal at a third frequency;

a direct conversion quadrature demodulator receiving the walking intermediate frequency signal from the first mixer and producing at least two output signals representing the real and imaginary components of modulated information contained in the carrier signal;

a local oscillator operating to provide the first local oscillator injection signal to the first mixer at the first frequency, and a second local oscillator injection signal to the direct conversion quadrature demodulator at the third frequency which is equal to the first frequency divided by an integer N greater than 1 and further equal to one of a sum or a difference of the first and second frequencies.

27. The low power zero-IF selective call receiver according to claim 26, wherein the direct conversion quadrature demodulator comprises:

a second mixer coupled to the first mixer and a digital phase shifter/divider, the second mixer converting an in phase component of the walking intermediate frequency signal to an in phase baseband signal in response to an in phase injection component of the second oscillator signal; and

a third mixer coupled to the first mixer and the digital phase shifter/divider, the third mixer converting a quadrature component of the walking intermediate frequency signal to a quadrature baseband signal in response to a quadrature injection component of the second oscillator signal.

28. The low power zero-IF selective call receiver according to claim 26, wherein the direct conversion quadrature demodulator comprises:

a pair of second mixers coupled to a digital phase shifter/divider and the first mixer, the pair of second mixers converting an in phase component of the walking intermediate frequency signal to an in phase baseband signal and a quadrature component of the walking intermediate frequency signal to a quadrature baseband signal in response to an in phase and a quadrature component of the second oscillator signal, respectively.

29. The low power zero-IF selective call receiver according to claim 26 wherein the integer N is equal to 4.