Apparatus and method of differential IQ frequency up-conversion

• US 20070230611A1
• Filed: 02/22/2006
• Published: 10/04/2007
• Est. Priority Date: 04/16/1999
• Status: Active Grant

• Current Assignee: ParkerVision, Inc.
• Original Assignee: ParkerVision, Inc.
• Inventors: Cook, Robert, Sorrells, David, Bultman, Michael, Moses, Charley, Rawlins, Michael, Looke, Richard, Rawlins, Gregory
• Granted Patent: US 7,693,230 B2
• Time in Patent Office: Days
• 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:

an in-phase channel including,

a first pair of impedances that receive a first differential signal; and

a first switch coupled across corresponding outputs of said first pair of impedances, said first switch controlled by a first control signal having a plurality of pulses;

a quadrature channel including,

a second pair of impedances that receive a second differential signal; and

a second switch coupled across corresponding outputs of said second pair of impedances, said second switch controlled by a second control signal having a plurality of pulses;

wherein said outputs of said first pair of impedances are wire-ored with said outputs of said second pair of impedances, resulting in an IQ output;

wherein said second control signal is phase-shifted by 270 degrees with respect to said first control signal.

2. The apparatus of claim 1, wherein said first switch shorts together said outputs of said first pair of impedances according to said pulses of said first control signal, and said second switch shorts together said outputs of said second pair of impedances according to said pulses of said second control signal.

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

4. The apparatus of claim 3, said first FET device having a gate controlled by said first control signal, and said second FET device having a gate controlled by said second control signal.

5. The apparatus of claim 1, wherein said IQ output includes a plurality of harmonic images, each harmonic image having the necessary amplitude, frequency, and phase information to reconstruct the first and second differential signal.

6. The apparatus of claim 5, wherein a sampling period T_S of said first and second control signals determines a harmonic frequency spacing between said plurality of harmonics of said IQ output signal.

7. The apparatus of claim 5, wherein a pulsewidth T_A of said first and second control signals determines a relative energy content that is up-converted into said harmonics of said IQ output.

8. The apparatus of claim 5, wherein a pulse width T_A of said first and second control signals is determined to be ½

sine wave wavelength (or ½

λ

) of a desired harmonic of said plurality of harmonics.

9. The apparatus of claim 5, wherein said wire-or is a direct differential connection between outputs of said first pair of impedances and said second pair of impedances.

10. The apparatus of claim 1, wherein said first and second pair of impedances include respective first and second pairs of storage elements.

11. The apparatus of claim 10, wherein said storage elements include at least one inductor.

12. The apparatus of claim 10, wherein said storage elements include at least one capacitor.

13. An apparatus for up-converting an in-phase (I) baseband signal and a quadrature (Q) baseband signal, comprising:

an in-phase channel configured to up-convert the I baseband signal using a first control signal, to generate an up-converted I signal;

a quadrature channel configured to up-convert the Q baseband signal using a second control signal, to generate an up-converted Q signal;

a wire-or connection between an output of said in-phase channel and an output of said quadrature channel, so as to combine said up-converted I signal and said up-converted Q signal.

14. The apparatus of claim 13, wherein said second control signal is phase-shifted by 270 degrees relative to said first control signal.

15. The apparatus of claim 13, wherein said in-phase channel includes a first FET device that samples said in-phase baseband signal according to said first control signal, and said quadrature channel includes a second FET device that samples said quadrature baseband signal according to said second control signal.

16. The apparatus of claim 13, wherein said wire-or connection is a direct connection between said output of said in-phase channel and said output of quadrature channel.

17. The apparatus of claim 13, wherein said outputs of said in-phase channel and said quadrature channel are differential, so that said wire-or is a differential direct connection between corresponding outputs of said in-phase channel output and said quadrature channel output.

18. The apparatus of claim 13, wherein said wire-or connection provides an IQ output signal having a plurality of harmonic images that each contain the necessary amplitude, frequency, and phase information to reconstruct the I baseband signal and the Q baseband signal.

19. The apparatus of claim 18, wherein a sampling period T_S of said first and second control signals determines a frequency spacing between said plurality of harmonics of said IQ output signal.

20. The apparatus of claim 18, wherein a pulsewidth T_A of said first and second control signals is adjusted to improve energy transfer to a desired harmonic of said plurality of harmonics.

21. A method of up-converting a first differential baseband signal and a second differential baseband signal, comprising:

receiving a first differential baseband signal and a second differential baseband signal;

generating a first control signal and a second control signal having a common frequency, wherein said second control signal is phase-shifted relative to said first control signal;

shorting together differential components of said first differential baseband signal according the first control signal resulting in a first up-converted signal, and shorting together differential components of said second differential baseband signal according to said second control signal resulting in a second up-converted signal; and

combining said first up-converted signal with said second up-converted signal using a wire-or connection.

22. The method of claim 21, wherein said step of combining includes the step of directing combining said first up-converted signal and said second up-converted signal.

23. The method of claim 21, wherein said second control signal is phase-shifted by 270 degrees relative to said first control signal.

24. The method of claim 21, wherein said wire-or connection is a direct connection of said first up-converted signal and said second up-converted signal, without the use of a summer or a combiner.

25. A method of up-converting a first baseband signal and a second baseband signal, comprising:

receiving a first baseband signal and a second baseband signal;

generating a first control signal and a second control signal having a common frequency, wherein said second control signal is phase-shifted relative to said first control signal;

sampling said first differential baseband signal according said first control signal resulting in a first up-converted signal, and sampling said second baseband signal according to said second control signal resulting in a second up-converted signal; and

combining said first up-converted signal with said second up-converted signal using a wire-or connection.

26. The method of claim 25, wherein said step of sampling includes the step of shunting said first baseband signal to ground based on said first control signal, and said step of shunting said second baseband signal includes the step of shunting said second control signal to ground based on said second control signal.

27. The method of claim 25, wherein said step of combining includes directly combining said first up-converted signal and said second up-converted signal without the use of a summer or a combiner.