Harmonic rejection mixer and phase adjustment method thereof

• US 8,478,215 B2
• Filed: 07/15/2011
• Issued: 07/02/2013
• Est. Priority Date: 09/14/2010
• Status: Expired due to Fees

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: Matsui, Naohiro
• Primary Examiner(s): Vuong, Quochien B
• Application Number:
  US13/137,036
• Publication Number:
  US 20120064850A1
• Time in Patent Office: 718 Days
• Field of Search: 455/63.1, 455/67.13, 455/131, 455/296, 455/302, 455/303, 455/304, 455/313, 455/323, 455/334, 327/113, 327/355, 331/10, 331/11, 331/12
• US Class Current: 455/131
• 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: H03D 7/18 Modifications of frequency-changers for eliminating image frequencies H03D7/16 takes precedence

Abstract

A harmonic rejection mixer converts a frequency of a radio frequency signal by using a first to a third local signals (LOs) whose phases are different from each other, and the harmonic rejection mixer includes a phase difference detection circuit for detecting a phase difference between the first LO and the second LO, a phase difference detection circuit for detecting a phase difference between the first LO and the third LO, a phase adjustment circuit for adjusting the phase of the second LO so that the phase difference detected by the phase difference detection circuit becomes a first phase difference, and a phase adjustment circuit for adjusting the phase of the third LO so that the phase difference detected by the phase difference detection circuit becomes a second phase difference. It is thereby possible to achieve high precision harmonic rejection characteristics.

Claims

1. A harmonic rejection mixer configured to convert a frequency of a radio frequency signal based on a first, a second, and a third local signals, the harmonic rejection mixer comprising:

a first mixer configured to output a first voltage indicating a phase difference between the first local signal and the second local signal;

a second mixer configured to output a second voltage indicating a phase difference between the first local signal and the third local signal;

a first adjustment circuit configured to adjust a phase of the second local signal based on the first voltage so that the phase difference between the first and the second local signals is a first predetermined phase difference; and

a second adjustment circuit configured to adjust a phase of the third local signal based on the second voltage so that the phase difference between the first and the third local signals is a second predetermined phase difference.

2. The harmonic rejection mixer according to claim 1,

wherein the harmonic rejection mixer adjusts the phase of the second local signal so that the first voltage is a first predetermined voltage, and

wherein the harmonic rejection mixer adjusts the phase of the third local signal so that the second voltage is a second predetermined voltage.

3. The harmonic rejection mixer according to claim 2,

wherein the first adjustment circuit includes a first variable-capacitance diode configured to adjust a capacitance thereof based on the first voltage, and

wherein the second adjustment circuit includes a second variable-capacitance diode configured to adjust a capacitance thereof based on the second voltage.

4. The harmonic rejection mixer according to claim 1, further comprising:

a third mixer configured to mix the radio frequency signal and the first local signal;

a fourth mixer configured to mix the radio frequency signal and the second local signal; and

a fifth mixer configured to mix the radio frequency signal and the third local signal.

5. The harmonic rejection mixer according to claim 4, wherein the first mixer has approximately the same characteristic as the third mixer.

6. The harmonic rejection mixer according to claim 1, further comprising:

a switch coupled to the first and the second mixers to output the radio frequency signal to the first and the second mixers within a normal time period and to output a correction signal based on the first local signal to the first and the second mixers within a correction time period.

7. The harmonic rejection mixer according to claim 6, further comprising a third mixer configured to mix the radio frequency signal and the first local signal within the normal time period.

8. A phase adjustment method of a first, a second, and a third local signals whose phases are different from each other in a harmonic rejection mixer for converting a frequency of a radio frequency signal by using the first, the second, and the third local signals, the phase adjustment method comprising the steps of:

calculating a first output voltage determined by a phase difference between the first local signal and a first reference signal having substantially the same phase as that of the first local signal;

calculating a second output voltage determined by a phase difference between the first local signal and a second reference signal having a phase reverse to that of the first local signal;

calculating a third and a fourth output voltages determined by a predetermined phase difference by using the first and the second output voltages;

adjusting the phase of the first local signal according to the first output voltage; and

adjusting the phases of the second and the third local signals according to the third and the fourth output voltages.