Transmission spectra
View Patent ↗Transmitter devices and transmission methods transmit a modulated GMSK- or EDGE-signal in a transmission system, wherein normally the pulse shaping follows the given rules of standards for these mobile radio systems. The amount of TX spectra in the adjacent TX channels is predetermined by these rules. A second filtering step is suggested to be introduced for attenuating predetermined unwanted spectra in the adjacent transmit channels. A second goal of this suggestion is to reduce spectra at adjacent TX channels also at cases of nonlinearity at the TX Power Amplifier of the RF transmitter. Nothing must be changed in standards of mobile communication systems, for example GSM.
1. A transmitter device for transmitting a radio signal via a transmission channel of a radio system, said device comprising:
a first spectral filter configured to improve said radio system with respect to undesirable transmission power density occurring in a neighboring transmission channel, wherein:
said first spectral filter is configured to low-pass filter said radio signal; and
said first spectral filter includes a finite impulse response filter having a predetermined sampling time which is smaller than a step period of primary transmission symbols and having a number of filter coefficients comprising data for a discrete convolution in the time domain, the filter coefficients including odd-numbered filter coefficients set to a first value and even-numbered filter coefficients set to a second value opposite to the first value.
2. A transmitter device according to claim 1 , wherein said radio system is an Enhanced Data rates for GSM Evolution (EDGE) system.
3. A transmitter device according to claim 1 , further comprising a suboptimal final transmission stage.
4. A transmitter device according to claim 3 , wherein said device comprises pre-compensation means for only partially compensating non-linear effects of said final transmission stage.
5. A transmitter device according to claim 4 , further comprising circuit elements for transmission via another radio system and arranged for low-pass filtering Cartesian components of a modulation pointer of a radio signal of said other radio system to improve a transmission spectrum of a final transmission stage even if said final transmission stage deletes all amplitude modulations.
6. A transmitter device according to claim 5 , wherein said other radio system is a Gaussian Minimum Shift Keying (GMSK) system.
7. A transmitter device according to claim 1 , wherein said spectral filter is configured to use said discrete convolution for pulse shaping and replace provision of a fundamental pulse.
8. A transmitter device according to claim 1 , wherein said first spectral filter is arranged in an in-phase path, the transmitter device further comprising a second spectral filter arranged in a quadrature-phase path and having filter parameters and a predetermined sampling time which is smaller than the step period of the primary transmission symbols.
9. A transmitter device according to claim 1 , wherein the first value is “1” and the second value is “4”, wherein said sampling time is set to one twelfth of said step period, and wherein said step period is set to 48/(13 MHz).
10. A transmitter device according to claim 1 , further comprising:
a digital-to-analog converter coupled to an output of the first spectral filter; and
an analog filter coupled to an output of the digital-to-analog converter, wherein said first spectral filter is configured to pre-compensate the analog filter by inverse convolution.
11. A transmitter device according to claim 1 , wherein said filter coefficients of said first spectral filter are variable to enable adjustment of a notch frequency of said first spectral filter.
12. A mobile terminal comprising a transmitter device according to claim 1 .
13. A method for use with a transmission channel of a radio system, said method comprising;
pulse shape filtering a radio signal, the pulse shape filtering including generating unwanted signal portions;
suppressing the unwanted signal portion by low-pass filtering said radio signal using a spectral filter configured to improve said radio system with respect to undesirable transmission power density occurring in a neighboring transmission channel, the low-pass filtering having a predetermined sampling time which is smaller than a step period of primary transmission symbols and having a number of filter coefficients comprising data for a discrete convolution in the time domain, the filter coefficients including odd-numbered filter coefficients set to a first value and even-numbered filter coefficients set to a second value opposite to the first value; and
transmitting the radio signal on the transmission channel of the radio system.
14. A method according to claim 13 , further comprising:
digital-to-analog converting the radio signal after low-pass filtering the radio signal; and
analog filtering the radio signal prior to transmitting the radio signal, wherein said low-pass filtering includes pre-compensating the analog filtering by inverse convolution.
15. A transmitter device for transmitting a radio signal via a transmission channel of a radio system, said device comprising:
a first spectral filter configured to improve said radio system with respect to undesirable transmission power density occurring in a neighboring transmission channel, wherein said first spectral filter is configured to low-pass filter said radio signal and said first spectral filter is a finite impulse response filter having a predetermined sampling time which is smaller than a step period of primary transmission symbols and having a number of filter coefficients comprising data for a discrete convolution in the time domain, the filter coefficients including odd-numbered filter coefficients set to a first value and even-numbered filter coefficients set to a second value opposite to the first value;
a digital-to-analog converter coupled to an output of the first spectral filter; and
an analog filter coupled to an output of the digital-to-analog converter, wherein said first spectral filter is configured to pre-compensate the analog filter by inverse convolution.
16. A transmitter device according to claim 15 , further comprising:
a suboptimal final transmission stage; and
pre-compensation means for only partially compensating non-linear effects of said final transmission stage.
17. A transmitter device according to claim 15 , further comprising circuit elements for transmission via another radio system and arranged for low-pass filtering Cartesian components of a modulation pointer of a radio signal of said other radio system to improve a transmission spectrum of a final transmission stage even if said final transmission stage deletes all amplitude modulations.
18. A transmitter device according to claim 17 , wherein said first spectral filter is arranged in an in-phase path, the transmitter device further comprising a second spectral filter arranged in a quadrature-phase path and having filter parameters and a predetermined sampling time which is smaller than the step period of the primary transmission symbols.