Method, system, and apparatus for balanced frequency up-conversion of a baseband signal

• US 8,077,797 B2
• Filed: 06/24/2010
• Issued: 12/13/2011
• Est. Priority Date: 04/16/1999
• Status: Expired due to Fees

• Current Assignee: ParkerVision, Inc.
• Original Assignee: ParkerVision, Inc.
• Inventors: Sorrells, David F., Bultman, Michael J., Cook, Robert W., Looke, Richard C., Moses, Charley D. Jr., Rawlins, Gregory S., Rawlins, Michael W.
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US12/823,055
• Publication Number:
  US 20100260289A1
• Time in Patent Office: 537 Days
• Field of Search: 375/295, 375/298, 375/259, 375/256, 375/296, 375309-312, 375/268, 455/76, 455/91, 455/118, 455/323, 455/313
• US Class Current: 375/295
• CPC Class Codes: H03C 3/40 using two signal paths the outputs of which have a predetermined phase difference and at least one output being amplitude-modulated
• CPC Class Codes: H03D 3/006 by sampling the oscillations and further processing the samples, e.g. by computing techniques H03D3/007 takes precedence
• CPC Class Codes: H03D 7/00 Transference of modulation from one carrier to another, e.g. frequency-changing H03D9/00, H03D11/00 take precedence; dielectric amplifiers, magnetic amplifiers, parametric amplifiers used as a frequency-changers H03F
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04L 25/03 Shaping networks in transmitter or receiver, e.g. adaptive shaping networks

Abstract

A balanced transmitter up-converts a baseband signal directly from baseband-to-RF. The up-conversion process is sufficiently linear that no IF processing is required, even in communications applications that have stringent requirements on spectral growth. In operation, the balanced modulator sub-harmonically samples the baseband signal in a balanced and differential manner, resulting in harmonically rich signal. The harmonically rich signal contains multiple harmonic images that repeat at multiples of the sampling frequency, where each harmonic contains the necessary information to reconstruct the baseband signal. The differential sampling is performed according to a first and second control signals that are phase shifted with respect to each other. In embodiments of the invention, the control signals have pulse widths (or apertures) that operate to improve energy transfer to a desired harmonic in the harmonically rich signal. A bandpass filter can then be utilized to select the desired harmonic of interest from the harmonically rich signal. The sampling modules that perform the sampling can be configured in either a series or a shunt configuration. In embodiments of the invention, DC offset voltages are minimized between the sampling modules to minimize or prevent carrier insertion into the harmonic images.

Claims

1. A method for up-converting a baseband signal, comprising the steps of:

(1) receiving the baseband signal;

(2) differentially sampling the baseband signal according to a first control signal and a second control signal resulting in a plurality of harmonic images that are each representative of the baseband signal, wherein said first and second control signals have pulse widths that improve energy transfer to a desired harmonic image of said plurality of harmonics; and

(3) minimizing DC offset voltages between sampling modules during step (2), and thereby minimizing carrier insertion in said harmonic images.

3. The method of claim 1, wherein step (2) comprises the steps of:

(a) converting said baseband signal into a differential baseband signal having a first differential baseband component and a second differential baseband component;

(b) sampling said first differential component according to said first control signal to generate a first harmonically rich signal, and sampling said second differential component according to said second control signal to generate a second harmonically rich signal, wherein said second control signal is phase shifted relative to said first control signal as measured by a master clock signal; and

(c) combining said first harmonically rich signal and said second harmonically rich signal to generate said harmonic images.

4. The method of claim 3, further comprising the step of:

(d) adding a reference voltage to said first differential component and said second differential component prior to step (b), and thereby minimizing any DC offset voltages during sampling of said first differential baseband component and said second differential baseband component.

5. The method of claim 3, wherein said step (b) of sampling comprises the steps of:

(i) generating said first control signal comprising a first plurality of pulses and said second control signal comprising a second plurality of pulses; and

(ii) operating a first switch according to said first control signal to periodically sample said first differential baseband component, and operating a second switch according to said second control signal to periodically sample said second differential baseband signal.

6. The method of claim 5, wherein said step (i) comprises the step of widening pulse widths of said first control signal and said second control signal by a non-negligible amount that tends away from zero time duration to extend the time that said first switch and said second switch is closed in step (ii), and thereby improving energy transfer to said desired harmonic image.

7. The method of claim 6, wherein said step of widening pulse widths comprises the step of widening pulse widths for said first and second control signals to a non-zero fraction of a period of the desired harmonic of interest.

8. The method of claim 6, wherein said step of widening pulse widths comprises the step of widening pulse widths for said first and second control signals to approximately one-half of a period of said desired harmonic of interest.

9. The method of claim 1, wherein said first control signal and said second control signal have a period of T_S so that said harmonics images repeat at 1/T_S in frequency, and wherein said second control signal is phase-shifted relative to said first control signal by approximately 180 degrees.

10. The method of claim 1, wherein said pulse widths of said first control signal and said second control signal are a non-zero fraction of a period of said desired harmonic of interest.

11. The method of claim 1, wherein said pulse widths of said first control signal and said second control signal are approximately one-half of a period of said desired harmonic of interest, and thereby improve energy transfer to said desired harmonic of interest.

13. The method of claim 1, wherein said harmonic images have an amplitude that is proportional to the following equation:

14. The method of claim 1, wherein said harmonic images have an amplitude that is based on n*(T_A/T_S), where T_S is a period of said first and second control signals, T_A is a pulse width of pulses in said first and second control signals, and n is a harmonic number of said harmonic image.

2. A method for up-converting a baseband signal, comprising the steps of:

(1) receiving the baseband signal;

(2) differentially sampling the baseband signal according to a first control signal and a second control signal resulting in a plurality of harmonic images that are each representative of the baseband signal, wherein said first and second control signals have pulse widths that improve energy transfer to a desired harmonic image of said plurality of harmonics; and

(3) minimizing DC offset voltages between sampling modules during step (2) by maintaining a reference voltage between said sampling modules during said differential sampling, thereby minimizing carrier insertion in said harmonic images.

12. The method of claim 2, wherein said pulse widths of said first control signal and said second control signal are approximately one-half of a period of said desired harmonic of interest, and thereby improve energy transfer to said desired harmonic of interest.