Radiofrequency transmitter with a high degree of integration and possibly with self-calibrating image deletion
View Patent ↗A radio frequency transmitter, of the type supplied with two signals in baseband and in quadrature, I(nT) and q(nT), which are images from two binary streams representing information to be transmitted, 1) provides a first transposition into the digital domain, at an intermediate frequency ω 0 , for the baseband signals and generates, by combination, two signals of intermediate frequency in quadrature, 2) provides a second transposition into the analog domain, after multiplication by a frequency ω 1 , followed by a summation of the two signals at intermediate frequency and in quadrature, in such a way that a resultant signal is generated which is found finally around a frequency ω 2 , where ω 2 =ω 0 +ω 1 . In an advantageous variant, the radio frequency transmitter additionally digitally compensates gain and phase imperfections of the direct conversion.
1. Radiofrequency transmitter, of the type supplied with two signals in base band and in quadrature, i(nT) and q(nT), which are images from two binary streams representing information to be transmitted, the radiofrequency transmitter:
means ( 1 ) of transposition into an intermediate frequency and of digital processing, that provide a first transposition into the digital domain, at an intermediate frequency ω 0 , for said base band signals, and generating, by combination, two signals at the intermediate frequency and in quadrature;
means ( 2 ) of direct conversion, providing a second transposition into the analog domain, after multiplication by a frequency ω 1 , followed by a summation, of said two signals at the intermediate frequency and in quadrature, in a way that generates a resultant signal which is finally modulated around a frequency ω 2 , where ω 2 = ω 0 +ω 1
wherein said two signals at the intermediate frequency and in quadrature are of the form:
m 1 (t)=i(t)·cos(ω 0 t)−q(t)·cos(ω 0 t)
m 2 (t)=−i(t)·sin(ω 0 t)−q(t)·cos(ω 0 t) and in that said resultant signal is of the form
m(t)=g 1 ·m 1 (t)·cos(ω 1 t+θ 1 )+g 2 ·m 2 (t)·sin(ω 1 t+θ 2 )
where
g 1 and g 2 are the respective gains for the two channels in quadrature of said means of direct conversion
θ 1 and θ 2 are the respective phase shifts for the two channels in quadrature of said means of direct conversion.
2. Radiofrequency transmitter according to claim 1 characterized in that it is produced in the form of an integrated circuit.
3. Radiofrequency transmitter according to claim 1 it additionally comprising filtering means ( 17 ) that receive and filter said resultant signal, in a way that suppresses, at least in part, a parasitic component of said resultant signal, at the image frequency ω −2 .
4. Radiofrequency transmitter according to claim 2 , at least a part of said filtering means ( 17 ) is included in said integrated circuit.
5. Radiofrequency transmitter of the type supplied with two signals in base band and in quadrature, i(nT) and q(nT), which are images from two binary streams representing information to be transmitted, the radiofrequency transmitter:
means ( 1 ) of transposition into an intermediate frequency and of digital processing, that provide a first transposition into the digital domain, at an intermediate frequency ω 0 , for said base band signals, and generating, by combination, two signals at the intermediate frequency and in quadrature;
means ( 2 ) of direct conversion, providing a second transposition into the analog domain, after multiplication by a frequency ω 1 , followed by a summation, of said two signals at the intermediate frequency and in quadrature, in a way that generates a resultant signal which is finally modulated around a frequency ω 2 , where ω 2 = ω 0 +ω 1
means ( 10 , and 11 ) of digitally compensating for imperfections in gain and in phase of said means of direct conversion
means ( 10 of estimating the imperfections in gain Δg and in phase Δθ of said means of direct conversion with,
Δg=g 2 −g 1
Δθ=θ 2 −θ 1
means ( 11 ) of applying a correction to said tow two signals at the intermediate frequency and in quadrature, in a way that generates two corrected signals, m 1c (t) and m 2c (t) at the intermediate frequency and in quadrature, the corresponding resultant corrected signal being written:
m c (t)=g 1 ·m 1c (t)·cos(ω 1 t+θ 1 )+g 2 ·m 2c (t)·sin(ω 1 t+θ 2 ).
6. Radiofrequency transmitter according to claim 5 , wherein said means ( 10 ) of estimating imperfections comprise:
transportation means ( 12 ), that provide a third transposition in the analog domain, by multiplication of the resultant signal by said transmission frequency ω 1 in a way that generates the following intermediate signal:
m′ 3 (t)=g 3 ·m(t)·cos(ω 1 t+θ 1 ),
where g 3 is the gain introduced by said transposition means ( 12 ), said filtering means ( 13 ) and said analog/digital A/N conversion means ( 14 );
high stop filtering means ( 13 ), providing filtration of the intermediate signal and generating an intermediate filtered signal m′(t);
analog/digital conversion means ( 14 ), enabling one to convert the intermediate filtered signal m′(t) into digital;
means ( 15 ) of calculating imperfections in gain Δg and in phase Δθ from the digital filtered intermediate signal by said means of analog/digital conversion.
7. Radiofrequency transmitter according to claim 6 , wherein said means ( 15 ) of calculating imperfections in gain Δg and in phase Δθ comprise:
means of transforming said digital filtered intermediate signal in the for:
m′(t)=i′(t)·cos(ω 0 t)−q′(t)·sin(ω 0 t)
and in that the imperfections in gain Δg and in phase Δθ are estimated in accordance with the following formulae;
Δg=2g−(4/g 3 )·[i′(t)+q′(t)]·[i(t)−q(t)]
Δθ=(1/g·g 3 )·[i(t)·q′(t)−q(t)i′(t)].
8. Radiofrequency transmitter according to claim 6 , wherein said gains g and g 3 have values of power 2.
9. Radio frequency transmitter according to claim 5 , wherein said two corrected signals, at the intermediate frequency and in quadrature, are written in the following simplified form:
m 1c (t)=(1+(Δg/2g))·[i(t)·cos(ω 0 t−(Δθ/2))−q(t)·sin(ω 0 t−(Δθ/2))]
m 2c (t)=−(1−(Δg/2g))·[i(t)·sin(ω 0 t−(Δθ/2))−q(t)·cos(ω 0 t+(Δθ/2))].
10. Radiofrequncy Radiofrequency transmitter according to claim 6 , wherein said means ( 14 ) of analog/digital conversion have a working frequency substantially identical to the working frequency of means ( 5 1 , 5 2 ) of digital/analog conversion included in said means ( 2 ) of direct conversion.
11. Radiofrequency transmitter according to claim 2 , additionally comprising means ( 10 , and 11 ) of digitally compensating for imperfections in gain and in phase of said means of direct conversion, said means ( 10 , 11 ) of digital compensation being included in said integrated circuit.
12. A radiofrequency transmitter configured to receive signals in baseband and in quadrature, wherein the signals comprise images from two binary streams representing information to be transmitted, the radiofrequency transmitter comprising:
means for transpositioning the signals into an intermediate frequency, wherein the transpositioning means is configured to provide the signals both at the intermediate frequency and in quadrature;
means for converting the signals as the intermediate frequency and in quadrature into the analog domain, wherein the converting means is configured to multiply the signals by a frequency ω 1 , sum the signals at the intermediate frequency and in quadrature, and generate a resultant signal modulated around a frequency ω 2 , where ω 2 =ω 0 +ω 1 ;
wherein the signals at the intermediate frequency and in quadrature comprise the form:
m 1 ( t ) =i ( t ) ·cos (ω 0 t ) −q ( t ) ·sin (ω 0 t )
m 2 ( t ) =−i ( t ) ·sin (ω 0 t ) −q ( t ) ·cos (ω 0 t ) ; and
wherein the resultant signal comprises the form:
m ( t ) =g 1 ·m 1 ( t ) ·cos (ω 1 t+θ 1 ) +g 2 ·m 2 ( t ) ·sin (ω 1 t+θ 2 ),
where:
g 1 and g 2 comprise gains for channels in quadrature of the converting means; and
θ 1 and θ 2 are the respective phase shifts for the channels in quadrature of the converting means.
13. The radiofrequency transmitter of claim 12 , wherein one or more of the transpositioning means or the converting means, or combinations thereof, are disposed in an integrated circuit.
14. The radiofrequency transmitter of claim 12 , further comprising means for filtering the signals, wherein a parasitic component signal is at least partially suppressed at an image frequency.
15. A radiofrequency transmitter of claim 14 , wherein the filtering means is at least partially disposed in an integrated circuit.
16. A radiofrequency transmitter configured to receive signals in baseband and in quadrature, wherein the signals comprise images from two binary streams representing information to be transmitted, the radiofrequency transmitter comprising:
means for transpositioning the signals into an intermediate frequency, wherein the transpositioning means is configured to provide the signals both at the intermediate frequency and in quadrature;
means for converting the signals as the intermediate frequency and in quadrature into the analog domain, wherein the converting means is configured to multiply the signals by a frequency ω 1 , sum the signals at the intermediate frequency and in quadrature, and generate a resultant signal modulated around a frequency ω 2 , where ω 2 =ω 0 +ω 1 ;
means for compensating for imperfections in gain or in phase, or combinations thereof, of the converting means;
means for estimating the imperfections in gain Δg or in phase Δθ, or combinations thereof, of the converting means where:
Δg=g 2 −g 1 ; and
Δθ=θ 2 −θ 1 ; and
means for correcting the signals at the intermediate frequency and in quadrature, wherein the correcting means is configured to generate corrected signals, m 1c ( t ) and m 2c ( t ) , at the intermediate frequency and in quadrature, and wherein the corrected signals have the form:
m c ( t ) =g 1 ·m 1c ( t ) ·cos (ω 1 t+θ 1 ) +g 2 ·m 2c ( t ) ·sin (ω 1 t+θ 2 ).
17. The radiofrequency transmitter of claim 16 , wherein the estimating means comprises:
means for multiplying an output of the transpositioning means by a transmission frequency ω 1 to provide an intermediate signal;
means for filtering the intermediate signal to generate an intermediate filtered signal m′ ( t );
means for converting an analog signal into a digital signal, wherein the analog - to - digital converting means is configured to convert the intermediate filtered signal m′ ( t ) into a digital filtered intermediate signal; and
means for calculating imperfections in gain or in phase, or combinations thereof, from the digital filtered intermediate signal by the analog - to - digital converting means;
wherein:
m′ 3 ( t ) =g 3 ·m ( t ) ·cos (ω 1 t+θ 1 ),
where g 3 is a gain introduced by one of the multiplying means, the filtering means, or the analog - to - digital converting means, or combinations thereof.
18. The radiofrequency transmitter of claim 17 , wherein the means for calculating imperfections in gain or in phase, or combinations thereof, comprises:
means for transforming the digital filtered intermediate signal as:
m′ ( t ) =i′ ( t ) ·cos (ω 0 t ) −q′ ( t ) ·sin (ω 0 t );
wherein the means for calculating imperfections in gain or in phase, or combinations thereof, is configured to estimate imperfections in gain Δg or in phase Δθ, or combinations thereof, as:
Δg= 2 g− ( 4 /g 3 ) ·[i′ ( t ) +q′ ( t ) ]·[i ( t ) −q ( t )]
Δθ=( 1 /g·g 3 ) ·[i ( t ) ·q′ ( t ) −q ( t ) i′ ( t )].
19. The radiofrequency transmitter of claim 17 , wherein the gains g and g 3 have values of exponents of the power 2 .
20. The radiofrequency transmitter of claim 16 , wherein the corrected signals, at the intermediate frequency and in quadrature, are configured to be represented as:
m 1c ( t )=( 1 + ( Δg/ 2 g )) ·[i ( t ) ·cos (ω 0 t− ( Δθ/ 2 )) −q ( t ) ·sin (ω 0 t− ( Δθ/ 2 ))]
m 2c ( t )=−( 1 − ( Δg/ 2 g )) ·[i ( t ) ·sin (ω 0 t− ( Δθ/ 2 )) −q ( t ) ·cos (ω 0 t+ ( Δθ/ 2 ))].
21. The radiofrequency transmitter of claim 17 , wherein the analog- to - digital converting means comprises a working frequency substantially identical to the working frequency of the transpositioning means or the converting means, or combinations thereof.
22. The radiofrequency transmitter of claim 13 , further comprising means for compensating for imperfections in gain or in phase, or combinations thereof, of an output from the converting means.
23. A method, comprising:
receiving signals in baseband and in quadrature, wherein the signals comprise images from two binary streams representing information to be transmitted;
transpositioning the signals into an intermediate frequency to provide the signals at both the intermediate frequency and in quadrature; and
converting the signals at the intermediate frequency and in quadrature into the analog domain, wherein said converting comprises multiplying the signals by a frequency ω 1 , summing the signals at the intermediate frequency and in quadrature, and generating a resultant signal modulated around a frequency ω 2 , where ω 2 =ω 0 +ω 1 ;
wherein the signals at the intermediate frequency and in quadrature comprise the form:
m 1 ( t ) =i ( t ) ·cos (ω 0 t ) −q ( t ) ·sin (ω 0 t )
m 2 ( t ) =−i ( t ) ·sin (ω 0 t ) −q ( t ) ·cos (ω 0 t ) ; and
wherein the resultant signal comprises the form:
m ( t ) =g 1 ·m 1 ( t ) ·cos (ω 1 t+θ 1 ) +g 2 ·m 2 ( t ) ·sin (ω 1 t+θ 2 )
where:
g 1 and g 2 comprise gains for channels in quadrature of said converting; and
θ 1 and θ 2 are the respective phase shifts for the channels in quadrature of said converting.
24. The method of claim 12 , further comprising filtering the signals, wherein a parasitic component signal is at least partially suppressed at an image frequency.
25. A radiofrequency transmitter, comprising:
a first circuit configured to generate an intermediate frequency signal from signals in baseband and in quadrature, wherein the intermediate frequency signal is a digital signal; and
a second circuit configured to convert the intermediate frequency signal from a digital signal into a resultant analog signal to be transmitted;
wherein the first circuit is configured to generate the intermediate frequency signal in a form so that, if converted by the second circuit, an image signal at an output of the second circuit is sufficiently attenuated without requiring filtering of the image signal;
wherein the intermediate frequency signal and the in quadrature signal comprise the form:
m 1 ( t ) =i ( t ) ·cos (ω 0 t ) −q ( t ) ·sin (ω 0 t )
m 2 ( t ) =−i ( t ) ·sin (ω 0 t ) −q ( t ) ·cos (ω 0 t ) ; and
wherein the resultant signal is of the form:
m ( t ) =g 1 ·m 1 ( t ) ·cos (ω 1 t+θ 1 ) +g 2 ·m 2 ( t ) ·sin (ω 1 t+θ 2 )
where:
g 1 and g 2 comprise gains for channels in quadrature of the second circuit; and
θ 1 and θ 2 are the respective phase shifts for the channels in quadrature of the second circuit.
26. The radiofrequency transmitter of claim 25 , wherein one or more of the first circuit or second circuits, or combinations thereof, are disposed in an integrated circuit.
27. The radiofrequency transmitter of claim 25 , further comprising a filter configured to at least partially suppress parasitic component signals at an image frequency.
28. The radiofrequency transmitter of claim 27 , wherein the filter is at least partially disposed in an integrated circuit.