Data signal system
View Patent ↗A demodulation system for Radio Data System (RDS) signals in a receiver includes a quadrature mixer ( 303 ) configured to convert a RDS signal at an input frequency directly to a base band RDS signal, a single filter ( 305 ) configured to filter the base band RDS signal to provide a RDS signal, and a signal level detector ( 311 ) configured to provide an indication of a level of the RDS signal ( 313 ), a demodulator ( 315 ) configured to demodulate the RDS signal and provide RDS data, the RDS data corresponding to information for user consumption, where the indication is used for selectively interrupting the user consumption when the level of the RDS signal is unsatisfactory. Other aspects of the RDS and corresponding methods include interference mitigation and include a blanker ( 323 ) configured to remove impulse noise from a RDS signal to provide the RDS signal without impulse noise and a demodulator ( 315 ) coupled to the blanker and configured to demodulate the RDS signal to provide data corresponding to information for user consumption.
1. A demodulation system in a receiver comprising:
a quadrature mixer configured to convert a multiplexed signal that includes a radio data system (RDS) signal at an input frequency directly to a base band RDS signal;
a single filter configured to filter the base band RDS signal to provide a RDS signal;
a signal level detector configured to provide an indication based on a level of the RDS signal;
a demodulator configured to demodulate the RDS signal and provide RDS data, the RDS data corresponding to information for user consumption,
wherein the indication is suitable for selectively interrupting the user consumption of the information provided by the RDS data when the level of the RDS signal is unsatisfactory.
2. The demodulation system of claim 1 wherein the quadrature mixer is further configured to convert a digital multiplexed signal at an input sample rate to a digital base band RDS signal and the single filter is further coupled to a first down sampler to provide the RDS signal at a first sample rate, the RDS signal at the first sample rate coupled to the signal level detector.
3. The demodulation system of claim 2 further comprising a second filter coupled to the RDS signal at the first sample rate and series coupled to a second down sampler to provide the RDS signal at a second sample rate, the demodulator further configured to demodulate the RDS signal at the second sample rate.
4. The demodulation system of claim 1 further comprising a blanker coupled to the RDS signal and arranged to remove impulse noise from the RDS signal prior to the demodulator demodulating the RDS signal.
5. The demodulation system of claim 4 wherein the RDS signal is a digital signal and the blanker operates to set a predetermined number of bits in each sample of the digital signal to a predetermined value, to remove impulse noise from the RDS signal.
6. The demodulation system of claim 5 wherein the blanker performs a plurality of shift operations on the samples corresponding to the RDS signal, thereby setting the predetermined number of bits to the predetermined value.
7. The demodulation system of claim 4 further comprising a subcarrier detector and a switch, the subcarrier detector coupled to the RDS signal and configured to control the switch to alternatively couple the RDS signal and the RDS signal with the impulse noise removed to the demodulator.
8. The demodulation system of claim 7 , wherein, when the subcarrier detector detects an unsuppressed subcarrier, the switch is controlled to couple the RDS signal to the demodulator and otherwise to couple the RDS signal with the impulse noise removed to the demodulator.
9. The demodulation system of claim 1 further comprising a decoder configured to decode the RDS signal data to provide decoded signals corresponding to the information for user consumption, wherein the indication is used to interrupt a flow of the information to the user when the level of the RDS signal is unsatisfactory.
10. The demodulation system of claim 1 wherein the quadrature mixer is electrically connected to an FM (frequency modulated) demodulator that provides the multiplexed signal that includes the RDS signal at an input frequency of 57 KHz, the quadrature mixer coupled to and driven by a 57 KHz local oscillator.
11. A Radio Data System (RDS) for a Multiplexed signal receiver, the RDS including interference mitigation and comprising:
a blanker coupled to and configured to remove impulse noise from a RDS signal as received to provide the RDS signal without impulse noise; and
a demodulator coupled to the blanker and configured to demodulate the RDS signal to provide data corresponding to information for user consumption,
wherein the RDS signal is a digital signal and the blanker is further configured to set a predetermined number of bits in each sample of the digital signal to a predetermined value and thereby mitigate interference due to the impulse noise in the RDS signal.
12. The Radio Data System of claim 11 wherein the blanker is configured to perform a plurality of shift operations on each sample, to set the predetermined number of bits to the predetermined value.
13. The Radio Data System of claim 11 further comprising a subcarrier detector coupled to the RDS signal and a switch coupled to the RDS signal and the RDS signal without impulse noise, the subcarrier detector configured to control the switch to alternatively couple the RDS signal and the RDS signal without impulse noise to the demodulator.
14. The Radio Data System of claim 13 wherein the subcarrier detector further comprises a low pass filter coupled to a comparator, wherein when an output of the low pass filter satisfies a threshold, the comparator provides a control signal suitable for controlling the switch so that the RDS signal rather than the RDS signal without impulse noise is coupled to the demodulator.
15. The Radio Data System of claim 11 further comprising a decoder to decode the data to provide RDS data and a display driver coupled to the RDS data, the display driver configured to present the information for user consumption on a display.
16. The Radio Data System of claim 11 further comprising an input portion for receiving a digital multiplex signal at an input sample rate that includes the RDS signal at an input frequency, the input portion comprising:
a complex mixer configured to convert the digital multiplex signal that includes the RDS signal directly to a base band RDS signal;
a first alter and first down sampler configured to filter the base band RDS signal to provide the RDS signal at a first sample rate;
a second filter and second down sampler configured to filter the RDS signal at the first sample rate and provide the RDS signal at a second sample rate.
17. A method of mitigating interference in a Radio Data System (RDS), the method comprising:
removing impulse noise from samples of a RDS signal;
demodulating and decoding the RDS signal with the impulse noise removed; and
providing data corresponding to the RDS signal in a form suitable for user consumption,
wherein the removing impulse noise further comprises setting a predetermined number of bits of each of the samples to a predetermined value to thereby mitigate the interference in the RDS signal.
18. The method of claim 17 wherein the setting a predetermined number of bits of each of the samples to a predetermined value further comprises performing a plurality of shifts operations on each sample.
19. The method of claim 17 further comprising detecting an unsuppressed subcarrier and when an unsuppressed subcarrier is detected, demodulating and decoding the RDS signal rather than the RDS signal with the impulse noise removed.