Method for generating a radio signal, and corresponding computer program products and devices
Patent Information
- Application Number
- EP2024716393
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-04-03
- Filing Date
- 2024-04-03
- Publication Date
- 2026-02-11
AI Technical Summary
Existing radio frequency transmitter architectures face limitations in generating wideband signals and are resource-intensive in terms of computing power, particularly when implementing Hilbert filtering in the digital domain for image rejection.
The method involves performing Hilbert filtering in the Walsh domain, using Walsh transformations and inverse Walsh transformations to generate phase-shifted channel signals, which reduces computing power requirements and enables wideband operation while maintaining image rejection capabilities.
This approach allows for efficient generation of radio frequency signals with wideband capabilities while minimizing computing power consumption, effectively addressing the limitations of existing architectures.
Smart Images
Figure EP2024059063_10102024_PF_FP_ABST
Abstract
Description
Description Title of the invention: Method for generating a radiofrequency signal, computer program products and corresponding devices. Field of invention
[0001] The field of the invention is that of data transmission via the use of a radio frequency signal.
[0002] The invention relates more particularly to a method of generating a radiofrequency signal intended to be transmitted on one (or two) transmission channels.
[0003] The invention thus has applications, in particular, but not exclusively, in the field of mobile telephony (e.g. 4G or 5G networks as defined by the 3GPP (for "3rd Generation Partnership Project" in English)), WLAN (for "Wireless Local Area Network" in English, e.g. using WiFi), digital broadcasting systems (DVB-T (for "Digital Video Broadcasting - Terrestrial" in English), ISDB-T (for "Integrated Services Digital Broadcasting-Terrestrial" in English), DAB (for "Digital Audio Broadcasting" in English)), high-speed wireless internet access (WiMAX), asymmetric digital links (xDSL), point-to-point links, etc. Prior art and its drawbacks
[0004] A radiofrequency (RF) transmitter architecture includes several key elements for transmitting information. For example, the modulating signal representing the information to be transmitted is traditionally generated digitally, in baseband or directly in intermediate frequency (IF), using a microprocessor and converted into an analog signal using digital-to-analog converters (DACs). A mixer is used to transpose this signal in frequencies, from the baseband or from the intermediate frequency, to an RF frequency. A power amplifier increases the signal power and the antenna radiates an electromagnetic field that is the image of the signal generated by the transmitter in question.
[0005] Among the known transmitter architectures, the image rejection architecture makes it possible to eliminate the image channel generated during the frequency transposition from an intermediate frequency to the RF frequency as detailed for example in the work of B. Razavi, “Rf Microelectronics”, Prentice Hall, 1998.
[0006] [Fig. 1] shows such an architecture. More particularly, the transmitter 100 uses the concept of IQ (in-phase / quadrature) signals to eliminate the image channel when transposing frequencies from an intermediate frequency to a channel RF frequency transmission. In this case, the transmitter 100 comprises:
[0007] - a digital 110 quadrature mixer delivering an intermediate frequency channel signal from digital baseband modulating signals, for the I and Q channels respectively. The intermediate frequency channel signal is centered on the intermediate frequency f 1F ;
[0008] - a DAC 140 delivering the channel signal in analog intermediate frequency from the digital signal X / F [w] ;
[0009] - an analog Hilbert 130 filter, with impulse response g(0, delivering a phase-shifted channel signal x IF jJ^t) as a function of the analog intermediate frequency channel signal Xi^t); and
[0010] - an analog 120 quadrature mixer delivering the radio frequency signal X RF (t) intended to be transmitted on the transmission channel from a first intermediate frequency signal x 1F ^t} and a second intermediate frequency signal Pl us particularly, the first signal in intermediate frequency x IFj(f) is in this case equal to the analog intermediate frequency channel signal X . The second signal in intermediate frequency is in this case equal to the phase-shifted channel signal x IF jJ^.
[0011] The 120 analog quadrature mixer is fed by two quadrature local oscillator signals. Both local oscillator signals have a component at a radio frequency f RF - Thus, as illustrated in [Fig.l], the transmission channel is here centered on a frequency equal to the radio frequency f RF the higher the intermediate frequency f IF . As discussed further below in relation to [Fig.lb], it is also possible to transpose the signal to be transmitted on the channel centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f IFby playing on the sign of the signals in intermediate frequencies to be transposed in frequency.
[0012] Returning to [Fig.l], depending on the implementations considered, the analog Hilbert filter 130 is realized e.g. using an RC-CR network or a polyphase filter. However, the desired phase shift is only obtained over a narrow frequency band. It is therefore impossible to use this architecture for wideband signals. Similarly, such an architecture is difficult to reconfigure so as to be able to generate signals on distant carriers in the frequency domain. To overcome this problem, Hilbert filtering can be implemented in the digital domain as illustrated in [Fig. la].
[0013] Furthermore, in a manner known per se, by playing on the sign of the first signal at intermediate frequency x IF j(f) or the second intermediate frequency signal ü it is possible to choose to transpose the signal to be transmitted on the channel centered on a frequency equal to the radio frequency f RF the higher the intermediate frequency f 1F or on the channel centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f [p . [Fig.lb] illustrates this effect in the case where the impulse response, - g[n], of the Hilbert filter 130 is the opposite of that of the Hilbert filter 130 of [Fig. la]. The other elements of [Fig.lb] being configured in an identical manner to those of [Fig. la], we observe that:
[0014] - the radiofrequency signal X RR (t) generated by the transmitter 100 of [Fig. 1a] is located in the transmission channel centered on the frequency equal to the radio frequency f RF the higher the intermediate frequency f Ip ;
[0015] - the radiofrequency signal X RF(t) generated by the transmitter 100 of [Fig.lb] is located in the image transmission channel centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f lp .
[0016] Such an effect (The. transposition of the radiofrequency signal X RR (t) in the transmission channel or in the image transmission channel) is also obtained regardless of the intermediate frequency signal (x IF or x IF J / p on which the minus sign is applied, and regardless of where in the data path the minus sign in question is applied.
[0017] However, even though the implementation of Hilbert filtering in the digital domain allows us to overcome the bandwidth limitation problems described above in relation to [Fig.l], such digital filtering requires significant resources in terms of computing power.
[0018] There is thus a need for a technique for generating a radio-frequency signal based on an image rejection architecture presenting a wide bandwidth as well as a limited cost with regard to computing power. Statement of the invention
[0019] In one embodiment of the invention, a method is proposed for generating a radio frequency signal intended to be transmitted on a first transmission channel. According to such a method, a transmitter performs: a frequency transposition by implementing a quadrature mixer delivering the radio frequency signal from a first intermediate frequency signal and a second intermediate frequency signal.
[0020] The transmitter performs, for the first transmission channel:
[0021] - a frequency transposition of first baseband signals delivering a first intermediate frequency channel signal; and
[0022] - a generation of a first phase-shifted channel signal as a function of the first signal of intermediate frequency channel.
[0023] The first intermediate frequency signal is linearly dependent on the first intermediate frequency channel signal. The second intermediate frequency signal is linearly dependent on the first phase-shifted channel signal. Generating the first phase-shifted channel signal includes:
[0024] - a Walsh transformation of the first intermediate frequency channel signal delivering a first transformed channel signal;
[0025] - a Hilbert filtering, transposed into the Walsh domain, of the first transformed channel signal delivering a first filtered transformed channel signal; and
[0026] - an inverse Walsh transform of the first filtered transformed channel signal delivering the first phase-shifted channel signal.
[0027] Thus, the invention proposes a new and inventive solution for generating a radiofrequency signal based on an image rejection architecture. More particularly, the implementation of Hilbert filtering in the Walsh domain makes it possible to reduce the computing power required to implement such a filter. Furthermore, the implementation of this filter in the digital domain makes it possible to obtain a wide operating bandwidth.
[0028] In some embodiments, the quadrature mixer is fed with two quadrature local oscillator signals. Both local oscillator signals have a component at a radio frequency. The first channel is centered at a frequency equal to the radio frequency plus the intermediate frequency or at a frequency equal to the radio frequency minus the intermediate frequency.
[0029] In some embodiments, the radio frequency signal is also intended to be transmitted on a second transmission channel. The transmitter performs, for the second transmission channel:
[0030] - a frequency transposition of second baseband signals delivering a second intermediate frequency channel signal; and
[0031] - generation of a second channel signal out of phase as a function of the second channel signal at intermediate frequency.
[0032] The first intermediate frequency signal is linearly dependent on a sum of the first intermediate frequency channel signal and the second intermediate frequency channel signal. The second intermediate frequency signal is linearly dependent on a difference between the first phase-shifted channel signal and the second phase-shifted channel signal. Generating the second phase-shifted channel signal comprises:
[0033] - a Walsh transformation of the second channel signal into intermediate frequency delivering a second transformed channel signal;
[0034] - a Hilbert filtering, transposed into the Walsh domain, of the second signal of transformed channel delivering a second filtered transformed channel signal; and
[0035] - an inverse Walsh transform of the filtered transformed second channel signal delivering the phase-shifted second channel signal.
[0036] In some embodiments wherein the radio frequency signal is also intended to be transmitted on a second transmission channel. The transmitter performs, for the second transmission channel:
[0037] - a frequency transposition of second baseband signals delivering a second intermediate frequency channel signal; and
[0038] - generation of a second channel signal out of phase as a function of the second channel signal at intermediate frequency.
[0039] The first intermediate frequency signal is linearly dependent on a difference between the first intermediate frequency channel signal and the second intermediate frequency channel signal. The second intermediate frequency signal is linearly dependent on a sum of the first phase-shifted channel signal and the second phase-shifted channel signal. Generating the second phase-shifted channel signal comprises:
[0040] - a Walsh transformation of the second channel signal into intermediate frequency delivering a second transformed channel signal;
[0041] - a Hilbert filtering, transposed into the Walsh domain, of the second transformed channel signal delivering a second filtered transformed channel signal; and
[0042] - an inverse Walsh transform of the filtered transformed second channel signal delivering the phase-shifted second channel signal.
[0043] Thus, two channels capable of carrying different data are generated in a single step of frequency transposition to radio frequencies.
[0044] In some embodiments, the quadrature mixer is fed with two quadrature local oscillator signals, both local oscillator signals having a component at a radio frequency. The first channel is centered at a frequency equal to the radio frequency plus the intermediate frequency. The second channel is centered at a frequency equal to the radio frequency minus the intermediate frequency.
[0045] In some embodiments, the Hilbert filtering comprises block digital filtering.
[0046] In some embodiments, the Walsh transform and the inverse Walsh transform are discrete Walsh transforms. The Walsh sequences implemented in said transforms are ordered according to a Hadamard order.
[0047] Thus, the computing power required to implement Walsh transforms and / or Hilbert filtering is further reduced.
[0048] The invention also relates to a computer program comprising program code instructions for implementing a generation method as described above, according to any one of its different embodiments, when executed on a computer.
[0049] In one embodiment of the invention, a transmitter is provided for generating a radiofrequency signal intended to be transmitted on a first transmission channel. Such a transmitter comprises means configured to implement the steps of the generation method according to the invention (according to any one of the different embodiments mentioned above). Thus, the characteristics and advantages of this transmitter are the same as those of the corresponding steps of the generation method described previously. Consequently, they are not detailed further. List of figures
[0050] Other aims, characteristics and advantages of the invention will appear more clearly on reading the following description, given as a simple illustrative, and non-limiting, example, in relation to the figures, among which:
[0051] [Fig.1], discussed above in the section “Prior art and its disadvantages”, represents a radiofrequency transmitter with image rejection according to a known technique;
[0052] [Fig. 1a], discussed above in the section "Prior art and its disadvantages", represents a radiofrequency transmitter with image rejection according to another known technique;
[0053] [Fig.lb], discussed above in the section "Prior Art and its Disadvantages", represents the effect of a sign change in the impulse response of the Hilbert filter implemented in the radio frequency transmitter of [Fig. la];
[0054] [Fig.2] illustrates a radiofrequency transmitter with image rejection according to an embodiment of the invention;
[0055] [Fig.3] illustrates an image rejection radiofrequency transmitter according to another embodiment of the invention;
[0056] [Fig.4] represents the steps of a method for generating a radiofrequency signal according to an embodiment of the invention;
[0057] [Fig.5] represents an example of a device structure allowing the implementation of certain steps of the method for generating a radiofrequency signal of [Fig.4] according to an embodiment of the invention.
[0058] Detailed description of embodiments of the invention
[0059] We now present, in relation to [Fig.2], a 200 radiofrequency transmitter with image rejection according to an embodiment of the invention.
[0060] Compared to the known architecture presented above in relation to [Fig.lb], the transmitter 200 comprises a digital block 210 comprising:
[0061] - a block 220 for Walsh transformation of the channel signal into intermediate frequency X ZF [n| delivering a transformed channel signal X ZF ; And
[0062] - a block 230 of Hilbert filtering, transposed into the Walsh domain, of the transformed channel signal X ZF delivering a filtered transformed channel signal X / FjD .
[0063] Hilbert filtering is implemented here in the form of block-based digital filtering, i.e. taking a sample block as input and delivering a sample block as output. More specifically, the output sample block is put into a vector form X ZF ^> is a function of a matrix product between a filter matrix G w and the input sample block put into vector form, X ZF . The filter matrix G w is a function of the impulse response, of the Hilbert filter implemented in block 230 as detailed e.g. in the article by C. Zarowski and M. Yunik, “Spectral filtering using the fast Walsh transform,” IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 33, no. 5, pp. 1246-1252, 1985. In some implementations, the Walsh transform implements Walsh sequences ordered according to a Hadamard order as detailed e.g. in the article by J. Johnson and M. Puschel, 2000 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings (Cat. No.00CH37100), vol. 6, 2000, pp. 3347-3350 vol.6. Thus, the filter matrix G w is block diagonal and antisymmetric, thereby reducing the computing power required for Hilbert filtering.
[0064] However, in other embodiments, Hilbert filtering, transposed into the Walsh domain, is implemented in other forms, e.g. in the form of an FIR (for “Finite Impulse Response”) or IIR (for “Infinite Impulse Response”) filter.
[0065] Returning to [Fig.2], the transmitter 200 further comprises a block 240 for inverse Walsh transformation of the filtered transformed channel signal X ZF ^> delivering the phase-shifted channel signal in the analog domain. More specifically, the phase-shifted channel signal is here equal to the second intermediate frequency signal x IF ^t).
[0066] Furthermore, according to the present embodiment, the first intermediate frequency signal x IF j(f) is in this case equal to the analog intermediate frequency channel signal X IF (ff
[0067] However, depending on the hardware implementation considered (eg due to the presence of amplifiers on the data path), we generally have the first signal at intermediate frequency x IF x (f) proportional to the first channel signal at intermediate frequency X ZF (f)- Similarly, generally the second signal in intermediate frequency x IF Jf) is proportional to the first phase-shifted channel signal Xipjfy- Preferably, the proportionality coefficient is substantially the same for the generation of the first signal at intermediate frequency x IF x (f) and for the generation of the second signal at intermediate frequency x IF Jj), the first channel signal in intermediate frequency X z / ^ï) and the first phase-shifted channel signal XiFj^t) being conventionally generated with the same power (or the same energy) and time-synchronous. Thus, the first signal at intermediate frequency xIF 1(0 et I e second intermediate frequency signal substantially equal power (or energy). This allows for optimal image rejection. However, depending on the hardware implementations considered, the existence of mismatches between the proportionality coefficients can lead to imperfect rejection of the image channel during signal recombination.
[0068] Returning to [Fig.2], implementing Hilbert filtering in the Walsh domain allows reducing the computing power required to implement such a filter. Furthermore, implementing this filter in the digital domain allows for a wide operating bandwidth.
[0069] Furthermore, as described above in relation to the prior art, depending on the sign of the impulse response, $n], and therefore of the filtering matrix G wof the Hilbert filter implemented in block 230, the radiofrequency signal X RF (t) generated by the transmitter 200 is located in the transmission channel centered on the frequency equal to the radio frequency f RF the higher the intermediate frequency f IF or in the transmission channel centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f IF (here it is considered by default the case where the radio frequency f RF is greater than the intermediate frequency f IF ). Such an effect (i.e. transposition of the radiofrequency signal X RR (t) in the transmission channel considered or in the transmission channel centered on the image frequency) is also obtained whatever the signal in intermediate frequency (x IF j(f) or x IF2,(t)) on which the minus sign is applied, and regardless of where in the corresponding data path the minus sign in question is applied.
[0070] We now present, in relation to [Fig. 3], a 200 radiofrequency transmitter with image rejection according to another embodiment of the invention.
[0071] Compared to the embodiment presented above in relation to [Fig.2], the transmitter 200 according to the present embodiment comprises two digital blocks 210 as described above. More particularly:
[0072] - a first digital block 210 delivers, for a first transmission channel, a first transformed channel signal X / F and a first filtered transformed channel signal XJF j); and
[0073] - a second digital block 210 delivers, for a second transmission channel (i.e. the transmission channel centered on the image frequency of the frequency on which the first transmission channel is centered), a second transformed channel signal ^IJF and a second filtered transformed channel signal ^IJFJJ.
[0074] Furthermore, a first adder 250 followed by an inverse Walsh transformation block 240 delivers a first signal at intermediate frequency x IF i(t) linearly dependent on a sum of the first channel signal in intermediate frequency X of the second channel signal in intermediate frequency Xjjp(t)-
[0075] Similarly, a second adder 250 followed by an inverse Walsh transform block 240 delivers a second intermediate frequency signal x^^t) linearly dependent on a difference between the first phase-shifted channel signal XiFf^t) and the second phase-shifted channel signal
[0076] For example, depending on the hardware implementation considered (eg due to the presence of amplifiers on the data path), we generally have the first signal at intermediate frequency x IF ](f) proportional to the sum of the first channel signal at intermediate frequency X of the second channel signal in intermediate frequency Xjjpit). Similarly, we generally have the second signal in intermediate frequency x IF ^t) proportional to a difference between the first phase-shifted channel signal x IF jJj) and the second phase-shifted channel signal As discussed above in relation to [Fig.2], preferably the coefficient of proportionality is substantially the same for the generation of the first signal at intermediate frequency x IF j(?) and for the generation of the second signal at intermediate frequency x IF^t). The first intermediate frequency channel signal Xfp(t), the first phase-shifted channel signal Xi F j£t), the second channel signal in intermediate frequency Xjjj^t), as well as the second phase-shifted channel signal x tjFF ^t) are in fact classically generated with the same power (or the same energy) and temporally synchronous. Thus, the first signal in intermediate frequency x IF x (f) and the second signal at intermediate frequency x IFz(t) have substantially equal power (or energy). Thus, optimal image rejection, and therefore decorrelation between the signals present in the first and second transmission channels, is obtained. However, depending on the hardware implementations considered, mismatches between the proportionality coefficients can lead to non-perfect rejection of the image channel during signal recombination and therefore to "cross-talk" between the signals present in the first transmission channel and the second transmission channel.
[0077] Returning to [Fig.3], the impulse response, <g[n], et donc la matrice de filtrage G vv of the Hilbert filter implemented in block 230 of the first digital block 210, as well than the impulse response, $n], and therefore the filter matrix G wof the Hilbert filter implemented in block 230 of the second digital block 210, have the same sign. Thus, the radiofrequency signal X RR (t) generated by transmitter 200 a:
[0078] - a first frequency component corresponding to the first transmission channel centered on the frequency equal to the radio frequency f RF the higher the intermediate frequency f IF ; And
[0079] - a second frequency component corresponding to the second transmission channel centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f Ip .
[0080] In other words, the radio frequency signal X RF (t) generated by the transmitter 200 is intended to be transmitted on a first transmission channel centered on the frequency equal to the radio frequency f RF the higher the intermediate frequency f IFand on a second transmission channel centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f 1F .
[0081] However, generally speaking and as described above in relation to [Fig.2], the first transmission channel is centered on the frequency equal to the radio frequency - frequencies the higher the intermediate frequency f IF or centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f lF depending on whether or not the minus sign is applied to the data path delivering the first channel signal at intermediate frequency X IF (t) (respectively the first phase-shifted channel signal x {F j / t)) ultimately composing the first signal in intermediate frequency x IF i(?) (respectively the second signal in intermediate frequency P arelsewhere, un te the effect est also obtained regardless of where in the given path the minus sign in question is applied.
[0082] Similarly, the second transmission channel is centered on the frequency equal to the radio frequency f RF the higher the intermediate frequency f IF or centered on the image frequency equal to the radio frequency f RF minus the intermediate frequency f IF depending on whether or not the minus sign is applied to the data path delivering the second channel signal at intermediate frequency (respectively on the data path delivering the second phase-shifted channel signal Xij FF ltJ) ultimately composing the first intermediate frequency signal (respectively the second signal in intermediate frequency x IFJ / ))- Moreover, such an effect is equally well obtained regardless of where on the given path the minus sign in question is applied.
[0083] So, in order to transmit the radio frequency signal X RR (t) on the two centered channels on the frequency equal to the radio frequency f RF the higher the intermediate frequency f [F and on the image frequency equal to the radio frequency f RF minus the intermediate frequency f JF , in an alternative way to the case illustrated in [Fig.3] we can have:
[0084] - the first adder 250 followed by the inverse Walsh transformation block 240 delivering a first signal at intermediate frequency x / F x (f) linearly dependent on a difference of the first channel signal in intermediate frequency X IF (t) and the second intermediate frequency channel signal Xjjpii); and
[0085] - the second adder 250 followed by the inverse Walsh transform block 240 delivering a second intermediate frequency signal Xj^ït) linearly dependent on a sum between the first phase-shifted channel signal x IF j / t) and the second phase-shifted channel signal
[0086] Again, the minus sign on the data path delivering the second phase-shifted channel signal can be applied to the filter matrix G as well w (or the impulse response of the Hilbert filter implemented in block 230 or at another location in the data path corresponding to the signal filtered by the Hilbert filter in question.
[0087] For example, the first signal at intermediate frequency x IF x (f) is proportional to the difference between the first channel signal in intermediate frequency second channel signal in intermediate frequency Xjjp(t). Similarly, the second signal in intermediate frequency Xjp^t) est proportional to the sum of the first phase-shifted channel signal XjpjJfy and the second phase-shifted channel signal XjjpJ^t). As discussed above, preferably the coefficient of proportionality is substantially the same for the generation of the first signal at intermediate frequency 1(f) and for the generation of the second signal at intermediate frequency x IF ^(t). The first channel signal in intermediate frequency X IF (t), the first phase-shifted channel signal x IF j^t), the second intermediate frequency channel signal Xjjp(i), as well as the second phase-shifted channel signal are in fact classically generated with the same power (or the same energy) and temporally synchronous! Thus, the first signal in intermediate frequency x IF x(f) and the second signal at intermediate frequency x IF Jj) have substantially equal power (or energy).
[0088] We now present, in relation to [Fig.4], the steps of a method for generating a radiofrequency signal X RR (t) according to an embodiment of the invention.
[0089] More specifically, the radiofrequency signal X RF (t) is intended to be transmitted on a first transmission channel.
[0090] Thus, during a step E400, a transmitter 200 (eg the transmitter 200 of [Fig.2] or the transmitter 200 of [Fig.3]) performs, for the first transmission channel, a transposition into frequencies of first baseband signals, Jtggyjn] and for channels I and Q respectively, delivering a first channel signal in intermediate frequency
[0091] During a step E410, the transmitter 200 performs, for the first transmission channel, a generation of a first phase-shifted channel signal as a function of the first intermediate frequency channel signal
[0092] More particularly, step E410 comprises:
[0093] - a step E410a of Walsh transformation of the first channel signal into intermediate frequency delivering a first transformed channel signal X / F ;
[0094] - a step E410b of Hilbert filtering, transposed into the Walsh domain, of the first transformed channel signal X / F delivering a first filtered transformed channel signal X 7FO ;
[0095] - a step E410c of inverse Walsh transformation of the first filtered transformed channel signal ^-IFX» delivering the first phase-shifted channel signal.
[0096] During a step E420, transmitter 200 performs, for the first transmission channel, a frequency transposition by implementing a quadrature mixer 120 delivering the radiofrequency signal X RF (t) from a first intermediate frequency signal x IF i(t) and a second intermediate frequency signal xlF2.(t)-
[0097] More specifically, the first intermediate frequency signal x fF i(t) is linearly dependent on the first channel signal at intermediate frequency X / jfra]- The second signal at intermediate frequency x IF ^(t) is linearly dependent on the first phase-shifted channel signal.
[0098] For example, as discussed above in connection with [Fig.2], the first intermediate frequency signal x JF i(f) is proportional to the first channel signal at intermediate frequency X t the second signal in intermediate frequency x1F z(t) is proportional to the first phase-shifted channel signal Xi F j£t\ Preferably, the proportionality coefficient is substantially the same for the generation of the first signal at intermediate frequency x IF i(t) and for the generation of the second signal at intermediate frequency
[0099] Depending on the implementation, the quadrature mixer 120 is fed by two quadrature local oscillator signals. Both local oscillator signals have a component at the radio frequency f RF - The first channel is centered on a frequency equal to:
[0100] - the radio frequency f RF the higher the intermediate frequency f IF ; Or
[0101] - the radio frequency f RF minus the intermediate frequency f lp .
[0102] As described above eg in relation to [Fig.2] or [Fig.3], the transposition of the radiofrequency signal X RF (t) in a transmission channel or in the image transmission channel is obtained by applying a minus sign to the intermediate frequency signal This is achieved regardless of where in the given path the minus sign in question is applied.
[0103] In some embodiments, the radio frequency signal X RF (t) is also intended to be transmitted on a second transmission channel. Thus, during step E400, the transmitter 200 (eg the transmitter 200 of [Fig.3]) further performs for the second transmission channel a transposition into frequencies of second baseband signals, x^ B j[n] and X / ^ B for channels I and Q respectively, delivering a second channel signal at intermediate frequency
[0104] During step E410, the transmitter 200 performs, for the second transmission channel, a generation of a second phase-shifted channel signal as a function of the second intermediate frequency channel signal X / ^-fn].
[0105] More specifically, during step E410:
[0106] - step E410a of Walsh transformation of the second channel signal into intermediate frequency X / jpJn] delivers a second transformed channel signal ^IJF;
[0107] - step E410b of Hilbert filtering, transposed into the Walsh domain, of the second transformed channel signal ^IJF delivers a second filtered transformed channel signal ^IJFJJ
[0108] - step E410c of inverse Walsh transformation of the second filtered transformed channel signal ^IJFX> delivers the second phase-shifted channel signal.
[0109] The first signal in intermediate frequency x IFi(f) is linearly dependent on a sum of the first intermediate frequency channel signal X / jft] and the second intermediate frequency channel signal X / ^pt]- The second intermediate frequency signal x IF ^(t) is linearly dependent on a difference between the first phase-shifted channel signal and the second phase-shifted channel signal. These are the operations corresponding to the case illustrated in [Fig.3]. However, as discussed above in connection with [Fig.3], the same effect is obtained when alternatively, the first intermediate frequency signal X / F i(f) is linearly dependent on a difference between the first channel signal in intermediate frequency and the second channel signal in intermediate frequency X / ^fn]- The second signal in intermediate frequency x IF z(t) is linearly dependent on a sum of the first phase-shifted channel signal and the second phase-shifted channel signal.
[0110] For example, as discussed above in connection with [Fig.3], the first intermediate frequency signal x IF j(f) is proportional to the sum of the first channel signal at intermediate frequency X JF (t) and the second channel signal in intermediate frequency The second signal in intermediate frequency x IF 2(t) is proportional to a difference between the first phase-shifted channel signal the second phase-shifted channel signal Xjjppfy- Preferably, the coefficient of proportionality is substantially the same for the generation of the first signal at intermediate frequency x IF i(f) and for the generation of the second signal at intermediate frequency x IF ;£t).
[0111] Thus, two channels capable of carrying different data are generated in a single step of frequency transposition to radio frequencies.
[0112] More particularly, the quadrature mixer 120 is fed by two quadrature local oscillator signals. Both local oscillator signals have a component at the radio frequency f RF . So :
[0113] - the first channel is centered on a frequency equal to the radio frequency f RF the higher the intermediate frequency f lF ; And
[0114] - the second channel is centered on a frequency equal to the radio frequency f RF minus the intermediate frequency f IF .
[0115] In some embodiments, Hilbert filtering is implemented as block digital filtering as described above in connection with [Fig. 2]. In some implementations, the Walsh transform implements Walsh sequences ordered according to a Hadamard order. Thus, the filter matrix is block diagonal and antisymmetric, thereby reducing the computational power required for Hilbert filtering.
[0116] We now present, in relation to [Fig. 5], an example of the structure of the transmitter 200 comprising means making it possible to implement all or part of the steps of the generation method of [Fig. 4] according to an embodiment of the invention.
[0117] More particularly, the transmitter 200 comprises an electronic device 500 comprising various means such as a random access memory 503 (for example a RAM memory), a processing unit 502 equipped for example with a processor, and controlled by a computer program stored in a read-only memory 501 (for example a ROM memory or a hard disk). Upon initialization, the code instructions of the computer program are for example loaded into the random access memory 503 before being executed by the processor of the processing unit 502.
[0118] The electronic device 500 is more particularly configured to carry out the steps of the generation method of [Fig.4] (according to any one of the embodiments and / or variants described above in relation to [Fig.4]) implemented by the digital blocks 210 described above in relation to [Fig.2] and [Fig.3], i.e. steps E400, E410a and E410b.
[0119] This [Fig. 5] illustrates only one particular way, among several possible ones, of producing the electronic device 500 so that it performs all or part of the aforementioned steps of the generation method of [Fig. 4] (according to any one of the embodiments and / or variants described above in relation to [Fig. 4]). Indeed, these steps can be performed indifferently on a reprogrammable computing machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module).
[0120] In the case where the electronic device 500 is produced with a reprogrammable computing machine, the corresponding program (i.e. the sequence of instructions) may be stored in a removable storage medium (such as for example a CD-ROM, a DVD-ROM, a USB key) or not, this storage medium being partially or totally readable by a computer or a processor.
[0121] According to some implementations, the electronic device 500 also implements the inverse Walsh transformation step E410c. However, according to the embodiment of [Fig. 5], the binary nature of the Walsh sequences (i.e. the fact that the sequences in question have two binary values) is taken advantage of to implement such an inverse Walsh transformation in a semi-analog manner. More particularly, the blocks 240 comprise inverse Walsh transformation means comprising for example:
[0122] - a plurality of 1-bit DACs (e.g. buffer type), each DAC being amplitude controlled by the inverse Walsh sequence corresponding to the sequential component considered for the inverse transformation; and
[0123] - an analog adder to sum the outputs of the different 1-bit DACs together and thus generate an analog quantity (voltage or current) representative of the inverse Walsh transform of the input signal so as to generate the output signal.
[0124] Furthermore, the transmitter 200 comprises analog / RF frequency transposition means, i.e. the quadrature mixer 120, configured to implement step E420. Such a quadrature mixer 120 is e.g. implemented via transistors configured to chop, at the rate of the local oscillator signal, the signal to be transposed into frequencies.
[0125] Thus, in all embodiments, the transmitter 200 comprises means configured to execute all or part of the steps of the generation method of [Fig.4] (according to any one of the embodiments and / or variants described above in relation to [Fig.4]).
Claims
Claims
1. A method of generating a radio frequency signal intended to be transmitted on a first transmission channel, in which a transmitter (200) performs: - a frequency transposition (E420) by implementing a quadrature mixer (120) delivering said radiofrequency signal from a first intermediate frequency signal and a second intermediate frequency signal, and in which the transmitter performs, for said first transmission channel: - a frequency transposition (E400) of first baseband signals delivering a first intermediate frequency channel signal; and - a generation (E410) of a first phase-shifted channel signal as a function of the first intermediate frequency channel signal, the first intermediate frequency signal being linearly dependent on the first intermediate frequency channel signal, the second intermediate frequency signal being linearly dependent on the first phase-shifted channel signal, characterized in that the generation of the first phase-shifted channel signal comprises: - a Walsh transformation (E410a) of the first intermediate frequency channel signal delivering a first transformed channel signal; - a Hilbert filtering (E410b), transposed into the Walsh domain, of the first transformed channel signal delivering a first filtered transformed channel signal; and - an inverse Walsh transform (E410c) of the first filtered transformed channel signal delivering the first phase-shifted channel signal.
2. The method of claim 1, wherein said quadrature mixer is fed with two quadrature local oscillator signals, both local oscillator signals having a component at a radio frequency, wherein said first channel is centered at a frequency equal to the radio frequency plus the intermediate frequency or at a frequency equal to the radio frequency minus the intermediate frequency.
3. Method according to claim 1 or 2, in which the radio frequency signal is also intended to be transmitted on a second transmission channel, in which the transmitter carries out, for said second transmission channel: - a frequency transposition (E400) of second baseband signals delivering a second channel signal in intermediate frequency; and - a generation (E410) of a second phase-shifted channel signal as a function of the second intermediate frequency channel signal, the first intermediate frequency signal being linearly dependent on a sum of the first intermediate frequency channel signal and the second intermediate frequency channel signal, the second intermediate frequency signal being linearly dependent on a difference between the first phase-shifted channel signal and the second phase-shifted channel signal, and wherein the generation of the second phase-shifted channel signal comprises: - a Walsh transformation (E410a) of the second channel signal into intermediate frequency delivering a second transformed channel signal; - a Hilbert filtering (E410b), transposed into the Walsh domain, of the second transformed channel signal delivering a second filtered transformed channel signal; and - an inverse Walsh transform (E410c) of the second filtered transformed channel signal delivering the second phase-shifted channel signal.
4. Method according to claim 1 or 2, in which the radio frequency signal is also intended to be transmitted on a second transmission channel, in which the transmitter carries out, for said second transmission channel: - a frequency transposition (E400) of second baseband signals delivering a second channel signal in intermediate frequency; and - a generation (E410) of a second channel signal phase-shifted as a function of the second channel signal in intermediate frequency, the first signal in intermediate frequency being linearly dependent on a difference between the first channel signal in frequency intermediate and the second intermediate frequency channel signal, the second intermediate frequency signal being linearly dependent on a sum of the first phase-shifted channel signal and the second phase-shifted channel signal, and wherein generating the second phase-shifted channel signal comprises: - a Walsh transformation (E410a) of the second channel signal into intermediate frequency delivering a second transformed channel signal; - a Hilbert filtering (E410b), transposed into the Walsh domain, of the second transformed channel signal delivering a second filtered transformed channel signal; and - an inverse Walsh transform (E410c) of the second filtered transformed channel signal delivering the second phase-shifted channel signal.
5. The method of claim 3 or 4, wherein said quadrature mixer is fed with two quadrature local oscillator signals, both local oscillator signals having a component at a radio frequency, wherein said first channel is centered at a frequency equal to the radio frequency plus the intermediate frequency, and wherein said second channel is centered at a frequency equal to the radio frequency minus the intermediate frequency.
6. A method according to any one of claims 1 to 5, wherein the Hilbert filtering comprises block digital filtering.
7. A method according to any one of claims 1 to 6, wherein said Walsh transform and said inverse Walsh transform are discrete Walsh transforms, the Walsh sequences implemented in said transforms being ordered according to a Hadamard order.
8. A computer program product comprising program code instructions for implementing the method according to any one of claims 1 to 7, when said program is executed on a computer.
9. Transmitter (200) for generating a radio frequency signal intended to be transmitted on a first transmission channel, the transmitter comprising: - means of transposition into frequencies by implementing a quadrature mixer (120) delivering said radiofrequency signal to from a first intermediate frequency signal and a second intermediate frequency signal, and, for said first transmission channel: - means for transposing into frequencies (500) first baseband signals delivering a first channel signal in intermediate frequency; and - means for generating (500, 240) a first phase-shifted channel signal as a function of the first intermediate frequency channel signal, the first intermediate frequency signal being linearly dependent on the first intermediate frequency channel signal, the second intermediate frequency signal being linearly dependent on the first phase-shifted channel signal, characterized in that the means for generating the first phase-shifted channel signal comprise: - Walsh transformation means (500) of the first channel signal into intermediate frequency delivering a first transformed channel signal; - Hilbert filtering means (500), transposed into the Walsh domain, of the first transformed channel signal delivering a first filtered transformed channel signal; and - inverse Walsh transform means (500, 240) of the first filtered transformed channel signal delivering the first phase-shifted channel signal.