Quadrature sub-harmonic frequency up-converter

• US 20070264945A1
• Filed: 05/11/2006
• Published: 11/15/2007
• Est. Priority Date: 05/11/2006
• Status: Active Grant

• Current Assignee: Cobham Defense Electronic Systems Corporation (Cobham PLC)
• Original Assignee: M/A Com
• Inventors: Carrez, Frederic
• Granted Patent: US 7,558,538 B2
• Time in Patent Office: Days
• US Class Current: 455/118
• 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

Abstract

A method and apparatus for frequency up-converting a baseband signal to radio frequency (RF) in two steps using the two quadrature components of a single local oscillator signal. In a first stage, the baseband signal is split into two parts in quadrature with each other and supplied to a quadrature mixer that mixes the one component of the baseband signal with the I component of a local oscillator signal at frequency F_LO and separately mixes the other baseband component with the Q component of the same local oscillator to produce an intermediate frequency signal centered at the local oscillator frequency and comprising two components, namely, an I component and a Q component. In the second stage, the intermediate frequency signal is mixed with both components of the same local oscillator signal in a sub-harmonic mixer-to produce a radio frequency output signal having a frequency component at three times the local oscillator frequency minus the baseband frequency.

Claims

1. A method for frequency up-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 higher than said first frequency, said method comprising the steps of:

(1) generating first and second oscillator signals having a third frequency that is about ⅓

of said second frequency, said first oscillator signal being 90°

out of phase with said second oscillator signal;

(2) receiving said first data signal;

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

(4) mixing said first data signal with said second oscillator signal to produce a second component of said third data signal centered at said fourth frequency and 90°

out of phase with said first component of said third data signal;

(5) combining said first and second components of said third data signal to produce a combined third data signal; and

(6) mixing said combined third data signal with at least one of said first and second oscillator signals in a sub-harmonic mixer to produce said second data signal having said second frequency, said second frequency being a harmonic frequency of said third and fourth frequencies.

2. The method of claim 1 wherein said first data signal comprises a baseband data signal.

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

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

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

said second frequency.

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

said second frequency.

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

said second frequency.

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

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

(7) amplifying said second data signal.

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

(8) converting said first data signal from the voltage domain to the current domain prior to step (3); and

(9) converting said second data signal from the current domain to the voltage domain after step (6).

11. The method of claim 1 wherein step (6) comprises mixing said combined third data signal with both of said first and second oscillator signals.

12. The method of claim 1 wherein step (6) comprises mixing said combined third data signal with one of said local oscillator signals, wherein said one of said local oscillator signals has a substantially higher amplitude that said combined third data signal.

13. A frequency up-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 higher than said first frequency comprising:

an oscillator generating a quadrature signal at a third frequency that about ⅓

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

a combining circuit coupled to combine said first and second components of said third data signal to produce a combined third data signal;

a sub-harmonic mixer coupled to receive said combined third data signal at a first input terminal thereof and coupled to receive at least one of said first and second components of said oscillator signal at at least a second input terminal thereof, said sub-harmonic mixer generating said second data signal having said second frequency being a harmonic frequency of said third and fourth frequencies.

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 first data signal is centered at 0 Hz.

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

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

said second frequency.

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

said second frequency.

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

said second frequency.

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

21. The apparatus of claim 13 further comprising:

an amplifier coupled to amplify said second data signal.

22. The apparatus of claim 13 further comprising:

(6) a voltage to current converter coupled between said first data signal and said quadrature mixer; and

(7) a current to voltage converter having an input terminal coupled to receive said second data signal and an output terminal.