Quadrature sub-harmonic frequency down-converter

• US 7,483,687 B2
• Filed: 05/11/2006
• Issued: 01/27/2009
• Est. Priority Date: 05/11/2006
• Status: Expired due to Fees

• Current Assignee: Cobham Defense Electronic Systems Corporation (Cobham PLC)
• Original Assignee: Cobham Defense Electronic Systems Corporation (Cobham PLC)
• Inventors: Carrez, Frederic
• Primary Examiner(s): Le; Thanh C
• Application Number:
  US11/431,972
• Publication Number:
  US 20070264959A1
• Time in Patent Office: 992 Days
• Field of Search: None
• US Class Current: 455/318
• CPC Class Codes: H03D 2200/0084 Lowering the supply voltage and saving power
• CPC Class Codes: H03D 7/1433 using bipolar transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1441 using field-effect transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1458 Double balanced arrangements, i.e. where both input signals are differential
• CPC Class Codes: H03D 7/1475 Subharmonic mixer arrangements
• 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: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes

Abstract

A method and apparatus for frequency down-converting a radio frequency (RF) signal to baseband in two steps using the two quadrature components of a single local oscillator. In the first stage, the RF signal is mixed with both components of the local oscillator signal (LO) in a sub-harmonic mixer to produce an intermediate frequency (IF) output signal having a frequency component at twice the local oscillator frequency minus the RF frequency, i.e., (2×LO)−RF=IF. In the second stage, the IF signal is split into two and supplied to a quadrature mixer that mixes the IF signal with the I component of the same local oscillator signal and separately mixes the IF signal with the Q component of the same local oscillator signal to produce an output signal comprising an I component and a separate Q component at baseband.

Claims

1. A method for frequency down-converting a first data signal centered at a first frequency to a second data signal containing the same data as said first data signal and centered at a second frequency lower than said first frequency, said method comprising the steps of:

(1) receiving said first data signal at said first frequency;

(2) mixing said first data signal with a local oscillator signal having a third frequency about one third of said first frequency in a sub-harmonic mixer to produce a third data signal having a fourth frequency that is a harmonic frequency of said first frequency and said third frequency;

(3) mixing said third data signal with said first component of said quadrature local oscillator signal at said third frequency to produce a first component of said second data signal centered at said second frequency; and

(4) mixing said third data signal with said second component of said quadrature local oscillator signal at said third frequency to produce a second component of said second data signal centered at said second frequency.

2. The method of claim 1 wherein said first data signal comprises a baseband data signal carried on a radio frequency carrier signal.

3. The method of claim 2 wherein said second data signal is centered at 0 Hz.

4. The method of claim 3 wherein said third frequency is ⅓

said first frequency.

5. The method of claim 2 wherein said second data signal is centered at a frequency other than 0 Hz.

6. The method of claim 5 wherein said third frequency is about ⅓

of said first frequency.

7. The method of claim 6 wherein said third frequency is within about 333.3 MHz of ⅓

of said first frequency.

8. The method of claim 1 wherein said third data signal at said fourth frequency comprises a harmonic at about twice said third frequency minus said first frequency.

9. The method of claim 1 further comprising the step of:

(5) amplifying said first data signal prior to step (2).

10. The method of claim 1 further comprising the steps of:

(6) converting said first data signal from the voltage domain to the current domain prior to step (2); and

(7) converting said second data signal from the current domain to the voltage domain after steps (3) and (4).

11. The method of claim 1 wherein step (2) comprises mixing said first data signal with first and second quadrature components of said local oscillator signal.

12. The method of claim 1 wherein step (2) comprises mixing said first data signal with a local oscillator signal having substantially higher amplitude that said first data signal.

13. A frequency down-converter for converting a first data signal centered at a first frequency to a second data signal containing the same data as said first data signal and centered at a second frequency lower than said first frequency comprising:

a local oscillator generating a quadrature signal at a third frequency that is about ⅓

of said first frequency, said quadrature signal having a first component having a first phase and a second component having a second phase 90°

out of phase with said first component;

a sub-harmonic mixer coupled to receive said first data signal at a first input terminal thereof and coupled to receive at least one of said first and second components of said local oscillator signal at second and third input terminals thereof, said sub-harmonic mixer generating a third data signal having a fourth frequency that is a harmonic frequency of said first frequency and said third frequency;

a quadrature mixer comprising first and second mixer components, said first mixer component coupled to mix said third data signal with said first component of said quadrature local oscillator signal to produce a first component of said second data signal centered at said second frequency and said second mixer component coupled to mix said third data signal with said second component of said quadrature local oscillator signal to produce a second component of said second data signal centered at said second frequency.

14. The apparatus of claim 13 wherein said first data signal comprises a baseband data signal carried on a radio frequency carrier signal.

15. The apparatus of claim 14 wherein said second data signal is centered at 0 Hz.

16. The apparatus of claim 15 wherein said third frequency is ⅓

said first frequency.

17. The apparatus of claim 14 wherein said second data signal is centered at a frequency other than 0 Hz.

18. The apparatus of claim 17 wherein said third frequency is about ⅓

said first frequency.

19. The apparatus of claim 18 wherein said third frequency is within about 333.3 MHz of ⅓

said first frequency.

20. The apparatus of claim 13 wherein said third data signal at said fourth frequency comprises a harmonic at about twice said third frequency minus said first frequency.

21. The apparatus of claim 13 further comprising:

an amplifier coupled between said first data signal and said first input terminal of said sub-harmonic mixer.

22. The apparatus of claim 13 further comprising:

(6) a voltage to current converter coupled between said first data signal and said first input terminal of said sub-harmonic mixer; and

(7) a current to voltage converter having an input terminal coupled to said quadrature mixer and an output terminal.