Apparatus and method of differential IQ frequency up-conversion

• US 8,036,304 B2
• Filed: 04/05/2010
• Issued: 10/11/2011
• Est. Priority Date: 04/16/1999
• Status: Expired due to Fees

• Current Assignee: ParkerVision, Inc.
• Original Assignee: ParkerVision, Inc.
• Inventors: Cook, Robert W., Rawlins, Gregory S., Bultman, Michael J., Sorrells, David F., Moses, Charley D. Jr., Looke, Richard C., Rawlins, Michael W.
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US12/662,190
• Publication Number:
  US 20100195757A1
• Time in Patent Office: 554 Days
• Field of Search: 375/295, 375/298, 375/259, 375/256, 375/296, 375/268, 455/118, 455/323, 455/313, 455/76, 455/91
• 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 1/04 Circuits
• CPC Class Codes: H04B 1/408 the transmitter oscillator frequency being identical to the receiver local oscillator frequency
• CPC Class Codes: H04B 2001/0491 with frequency synthesizers, frequency converters or modulators
• CPC Class Codes: H04L 25/03 Shaping networks in transmitter or receiver, e.g. adaptive shaping networks

Abstract

A balanced transmitter up-converts I and Q baseband signals 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 I and Q baseband signals 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 I and Q baseband signals. 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.

Claims

1. An apparatus, comprising:

a first channel, the first channel comprising;

a first pair of impedances configured to receive a first differential signal, and

a first switch configured to sample the first differential signal by shorting together corresponding outputs of the first pair of impedances in response to a first control signal.

2. The apparatus of claim 1, wherein the first switch is a first FET device having respective source and drain coupled across the outputs of the first pair of impedances.

3. The apparatus of claim 2, wherein the first FET device includes a gate controlled by the first control signal.

4. The apparatus of claim 1, further comprising:

a second channel, the second channel comprising;

a second pair of impedances configured to receive a second differential signal, and

a second switch configured to sample the second differential signal by shorting together corresponding outputs of the second pair of impedances in response to a second control signal.

5. The apparatus of claim 4, wherein the first control signal includes a first plurality of pulses and the second control signal includes a second plurality of pulses, the first and the second plurality of pulses being characterized as being out of phase with respect to each other.

6. The apparatus of claim 5, wherein a pulse width of each of the first and the second plurality of pulses is a half sine wavelength of a desired output frequency.

7. The apparatus of claim 4, further comprising:

a wire-or connection configured to combine the outputs of the first pair of impedances with the outputs of the second pair of impedances to provide a combined output signal.

8. The apparatus of claim 7, wherein the combined output signal comprises:

a plurality of harmonic images, each image including baseband information from the first differential signal and the second differential signal.

9. The apparatus of claim 1, wherein the first pair of impedances is characterized as being a low impedance at DC and a high impedance at a frequency of interest.

10. The apparatus of claim 1, wherein the first switch is further configured to sub-sample the first differential signal at a sub-harmonic of the first differential signal.

11. A method, comprising:

(a) receiving, by a first pair of impedances, a first differential signal, and

(b) sampling, by a first switch, the first differential signal by shorting together its differential components in response to a first control signal to provide a first sampled signal.

12. The method of claim 11, wherein the first switch is a first FET device having respective source and drain coupled across outputs of the first pair of impedances.

13. The method of claim 12, wherein the first FET device includes a gate controlled by the first control signal.

14. The method of claim 11, further comprising:

(c) receiving, by a second pair of impedances, a second differential signal, and

(d) sampling, by a second switch, the second differential signal by shorting together its differential components in response to a second control signal to provide a second sampled signal.

15. The method of claim 14, wherein the first control signal includes a first plurality of pulses and the second control signal includes a second plurality of pulses, the first and the second plurality of pulses being characterized as being out of phase with respect to each other.

16. The method of claim 15, wherein a pulse width of each of the first and the second plurality of pulses is a half sine wavelength of a desired output frequency.

17. The method of claim 14, further comprising:

(e) combining the first sampled signal and the second sampled signal to provide a combined output signal.

18. The method of claim 17, wherein the combined output signal comprises:

a plurality of harmonic images, each image including baseband information from the first differential signal and the second differential signal.

19. The method of claim 11, wherein the first pair of impedances is characterized as being a low impedance at DC and a high impedance at a frequency of interest.

20. The method of claim 11, wherein step (b) comprises:

(b)(i) sub-sampling the first differential signal at a sub-harmonic of the first differential signal.