Modulation circuit for a radio device and a method thereof

• US 9,379,798 B2
• Filed: 02/06/2015
• Issued: 06/28/2016
• Est. Priority Date: 02/06/2014
• Status: Active Grant

• Current Assignee: IMEC International
• Original Assignee: IMEC International
• Inventors: Guermandi, Davide, Giannini, Vito, Van Thillo, Wim, Bourdoux, Andr
• Primary Examiner(s): HA, DAC V
• Application Number:
  US14/615,541
• Publication Number:
  US 20150222344A1
• Time in Patent Office: 508 Days
• US Class Current: 1/1
• CPC Class Codes: H03D 2200/0086 Reduction or prevention of harmonic frequencies
• 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 7/165 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: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths
• CPC Class Codes: H04B 7/06 at the transmitting station
• CPC Class Codes: H04L 27/2053 using more than one carrier, e.g. carriers with different phases

Abstract

The present disclosure relates to a modulation circuit and a method for suppressing energy content of spectral side lobes caused by high-frequency content present in a baseband signal, with the energy content of the spectral side lobes being outside an intended operational bandwidth in a modulated radio-frequency signal. An example circuit is configured to: receive a digital baseband signal, feed the digital baseband signal to a first and a second signal path, with the first signal path comprising a first mixer and the second signal path comprising a delay circuit and a second mixer. The first mixer and the second mixer may receive a same local oscillator signal, and may respectively provide a first radio-frequency signal and a second radio-frequency signal that are delayed with respect to each other. The example circuit is further configured to generate an output radio-frequency signal by combining the first and second radio-frequency signals.

Claims

1. A circuit comprising:

a first signal path comprising a first mixer, wherein the first mixer is configured to modulate a baseband signal with a local oscillator signal to provide a first radio-frequency signal, wherein the first mixer is configured to receive (i) the baseband signal at a non-linear input and (ii) the local oscillator signal at a linear input;

a second signal path comprising a delay circuit and a second mixer, wherein the delay circuit is configured to delay the baseband signal by a delay time, and wherein the second mixer is configured to modulate the delayed baseband signal with the local oscillator signal to provide a second radio-frequency signal, wherein the second mixer is further configured to receive (i) the delayed baseband signal at a non-linear input and (ii) the local oscillator signal at a linear input; and

an adder circuit configured to combine the first radio-frequency signal and the second radio-frequency signal to provide an output radio-frequency signal.

2. The circuit of claim 1, wherein the delay time is one-third of a bit period of the baseband signal.

3. The circuit of claim 1, wherein the first signal path comprising a first filter upstream of the first mixer, and wherein the second signal path comprises a second filter between the delay circuit and the second mixer, wherein each of the first filter and the second filter comprises a passive low-pass filter.

4. The circuit of claim 3, wherein the passive low-pass filter has a cut-off frequency of 2 GHz.

5. The circuit of claim 1, wherein each of the first mixer and the second mixer comprises a passive mixer.

6. The circuit of claim 1, wherein the at least one millimeter-wave frequency signal comprises a frequency above 2 GHz.

7. The circuit of claim 1, wherein the circuit is arranged to output a binary phase-shift keying modulated radio-frequency signal.

8. A method comprising:

receiving at a modulation circuit a digital baseband signal;

mixing the digital baseband signal with a local oscillator signal to generate a first radio-frequency signal, wherein mixing the digital baseband signal comprises receiving;

(i) the baseband signal at a non-linear input and (ii) the local oscillator signal at a linear input;

delaying the digital baseband signal to provide a delayed baseband signal;

mixing the delayed baseband signal with the local oscillator signal to generate a second radio-frequency signal, wherein mixing the delayed baseband signal comprises receiving (i) the delayed baseband signal at a non-linear input and (ii) the local oscillator signal at a linear input; and

generating an output radio-frequency signal by combining the first radio-frequency signal and the second radio-frequency signal.

9. The method of claim 8, further comprising filtering the digital baseband signal before mixing the digital baseband signal with the local oscillator signal and filtering the delayed baseband signal before mixing the delayed baseband signal with the local oscillator signal.

10. The method of claim 9, wherein filtering the delayed baseband signal comprises filtering the delayed baseband signal with a passive low pass filter having a cut-off frequency of 2 GHz.

11. The method of claim 8, wherein the delay time is one-third of a bit period of the digital baseband signal.

12. The method of claim 8, wherein mixing the digital baseband signal with the local oscillator signal and mixing the delayed baseband signal with the local oscillator signal are performed with respective passive mixers.

13. The method of claim 8, wherein at least one millimeter-wave frequency signal comprises a frequency above 2 GHz.

14. The method of claim 8, wherein the output radio-frequency signal comprises a binary phase-shift keying modulated radio-frequency signal.

15. A radio device comprising a modulation circuit, the modulation circuit comprising:

a first signal path comprising a first mixer, wherein the first mixer is configured to modulate a baseband signal with a local oscillator signal to provide a first radio-frequency signal, wherein the first mixer is configured to receive (i) the baseband signal at a non-linear input and (ii) the local oscillator signal at a linear input;

a second signal path comprising a delay circuit and a second mixer, wherein the delay circuit is configured to delay the baseband signal by a delay time, and wherein the second mixer is configured to modulate the delayed baseband signal with the local oscillator signal to provide a second radio-frequency signal; and

an adder circuit configured to combine the first radio-frequency signal and the second radio-frequency signal to provide an output radio-frequency signal.

16. The radio device of claim 15, wherein the delay time is one-third of a bit period of the baseband signal.

17. The radio device of claim 15, wherein each of the first mixer and the second mixer comprises a passive mixer.

18. The radio device of claim 15, wherein the output radio-frequency signal comprises a frequency above 2 GHz.

19. The radio device of claim 15, wherein the circuit is arranged to output a binary phase-shift keying modulated radio-frequency signal.