Integrated micro-sampling wireless receiver
View Patent ↗Disclosed are methods and systems for filtering an intermediate frequency (IF) band when digitizing a radio frequency (RF) signal using a higher Nyquist zone several times above the sampling rate. Undersampling may be employed along with an undersampled Nyquist filtering technique to implement an integrated receiver for base station applications such as wireless base station beacon monitoring. Such a receiver may be integrated into a smaller package and consume less power at a reduced cost. In one embodiment, the receiver may operate at a high RF sampled frequency that is microsampled in the 10 th Nyquist zone at less than 20% undersampling. In another embodiment, the receiver may operate in the 5 th Nyquist zone at ½ the sampling rate with 40% undersampling. In various embodiments, sampling and processing functions may be implemented using software on a computer or other embedded computing device.
1. A method for use in a software defined radio (SDR) system including an analog to digital convertor (ADC) operating at a sampling rate, Fs, to sample and digitize an intermediate frequency (IF) signal derived from a received radio frequency (RF) signal, comprising:
selecting a Nyquist zone at least five times above said sampling rate;
selecting an IF sampling band for the selected Nyquist zone that substantially matches a low loss filter for providing a desired dynamic range;
down-converting the RF signal to said IF sampling band, thereby providing the IF signal within the selected Nyquist zone;
filtering said IF signal using said low loss filter; and
sampling the IF signal within the selected Nyquist zone at said sampling rate, wherein said sampling comprises undersampling at less than 20% of said IF sampling band.
2. The method of claim 1 , wherein said low loss filter is a surface acoustic wave (SAW) filter.
3. The method of claim 1 , wherein the selected Nyquist zone is in a tenth Nyquist zone above said sampling rate.
4. The method of claim 2 , wherein the low loss filter is characterized by a shape of 55:5.
5. A software defined radio (SDR) system comprising:
at least one radio frequency (RF) receiver;
at least one analog to digital converter (ADC) communicatively coupled to said RF receiver;
at least one processor communicatively coupled to said ADC; and
at least one memory communicatively coupled to said at least one processor, the at least one memory storing therein computer readable instructions capable of configuring said SDR system to perform the following method:
selecting a Nyquist zone at least five times above a sampling rate;
selecting an intermediate frequency (IF) sampling band for the selected Nyquist zone that substantially matches a low loss filter for providing a desired dynamic range;
down-converting the RF signal to said IF sampling band, thereby providing an IF signal within the selected Nyquist zone;
filtering said IF signal using said low loss filter; and
sampling the IF signal within the selected Nyquist zone at said sampling rate, wherein said sampling comprises undersampling at less than 20% of said IF sampling band.
6. The SDR system of claim 5 , wherein said low loss filter is a surface acoustic wave (SAW) filter.
7. The SDR system of claim 5 , wherein said Nyquist zone is in a tenth Nyquist zone above said sampling rate.
8. The SDR system of claim 5 , wherein said Nyquist zone is in a fifth Nyquist zone above said sampling rate.
9. The SDR system of claim 5 , wherein the low loss filter is characterized by a shape of 55:5.
10. A system for filtering and digitizing an intermediate frequency (IF) or a radio frequency (RF) signal, the system comprising:
means for receiving RF signals;
means for digitizing said RF signals or an IF signal derived from said RF signal;
means for receiving a sampling rate and a desired dynamic range;
means for selecting a Nyquist zone at least five times above said sampling rate;
means for selecting a sampling band for the selected Nyquist zone for providing the desired dynamic range;
low loss filtering means for filtering said signal; and
means for sampling and digitizing the signal within the selected Nyquist zone at said sampling rate, wherein said means for sampling comprises means for undersampling at less than 20% of said IF sampling band.
11. The system of claim 10 , wherein said low loss filtering means comprises a surface acoustic wave (SAW) filter.
12. The system of claim 10 , wherein the selected Nyquist zone is in a tenth Nyquist zone above said sampling rate.
13. The system of claim 10 , wherein the selected Nyquist zone is in a fifth Nyquist zone above said sampling rate.
14. The system of claim 11 , wherein the low loss filtering means provides a filter shape of 55:5.