This application claims the benefit of U.S. provisional application No. 61/680,095, filed on Aug. 6, 2012 and incorporated herein by reference.
1. Technical Field
The invention relates generally to telecommunications, and more particularly, to analysis of multiple carriers used in telecommunications.
2. Related art
A first telecommunications device may be served by one of several second telecommunications devices near the first telecommunications device. For example, the first telecommunications device may be a mobile station (MS) or user equipment (UE); each of the second telecommunications devices may be a telecommunications base station (BS) or Node B. Each of the second telecommunications devices may use a specific carrier. A carrier may also be called a carrier signal or a carrier wave; it may have a specific frequency.
From the first telecommunications device's perspective, the second telecommunications device that's currently serving the first telecommunications device may be regarded a serving telecommunications device. Although the first telecommunications device may not be communicating with the other nearby second telecommunications devices, the first telecommunications device may need to monitor carriers used by these nearby second telecommunications devices. For example, this may help the first telecommunications device to determine whether to select another nearby second telecommunications device as its serving telecommunications device, and which one of the nearby second telecommunications devices should be selected.
Because there may be several carriers to be monitored, e.g. as many as 32 carriers, receiving these carriers one after another may take up a lot of time and waste a lot of power. The excessive power consumption may reduce the standby time of the first telecommunications device, forcing its user to charge it more frequently. In addition, the long delay may make it inconvenient to use the first telecommunications device.
An embodiment of the invention provides a method of processing a radio frequency (RF) signal. According to the embodiment, the RF signal is first synthesized with a synthesis signal to generate a synthesized signal. Then, the synthesized signal is filtered with a filtering bandwidth to generate a filtered signal. Next, the filtered signal is converted into digital data. Then, the digital data is processed to analyze a plurality of carriers within the filtering bandwidth as presented in the RF signal.
Another embodiment of the invention provides a telecommunications device. The telecommunications device includes a synthesizer, a RF front end (RF FE), a filter, an analog-to-digital convertor (ADC), and a digital circuit. The synthesizer is configured to provide a synthesis signal. The RF FE is coupled to the synthesizer, and is configured to synthesize an RF signal received from an antenna with the synthesis signal to generate a synthesized signal. The filter is coupled to the RF FE and is configured to filter the synthesized signal to generate a filtered signal. The filter has a filtering bandwidth. The ADC is coupled to the filter and is configured to convert the filtered signal into digital data. The digital circuit is coupled to the ADC and is configured to process the digital data to analyze a plurality of carriers within the filtering bandwidth as presented in the RF signal.
Other features of the invention will be apparent from the accompanying drawings and from the detailed description which follows.
The invention is fully illustrated by the subsequent detailed description and the accompanying drawings.
The antenna 110 is configured to receive an RF signal and pass the RF signal to the RF FE 130. The RF signal may contain information conveyed at several different frequencies. Some of these frequencies may be carriers used by some second telecommunications devices near the first telecommunications device 100. For example, these carriers may be broadcast control channel (BCCH) carriers, and the first telecommunications device 100 may need to monitor these carriers from time to time. The SX 120 is configured to generate a synthesis signal for the purpose of frequency down conversion. To accomplish this, the SX 120 may need to include a local oscillator (LO).
After looking into several major telecommunications systems around the world, it has been found that many carriers to be monitored are likely close to each other in the frequency domain. As a result, the first telecommunications device 100 may take advantage of this characteristic to monitor these carriers together at once. For example, the first telecommunications device 100 may use the method of
Please refer to both
Then, at step 240, the filter 140 filters the synthesized signal to generate a filtered signal. In order to retain the information at frequencies near the synthesis frequency f_sx, the filter 140 may be a wideband filter (such as a low-pass filter or a band-pass filter) with a relatively larger filtering bandwidth. For example, an upper cut-off frequency f_co of the filter 140 may be at least 500 kHz. As another example, the upper cut-off frequency f co of the filter 140 may be at least 1 MHz. The filter 140 may help retain those carriers within the filtering bandwidth and exclude other frequency components outside the filtering bandwidth.
Generally speaking, a filter may have a resistor-capacitor (RC) circuit, and its upper cut-off frequency is inversely proportional to the product of the RC circuit's resistance and capacitance. As a result, the greater the upper cut-off frequency, the smaller the filter will be on an integrated circuit (IC). Because the filter 140 of this embodiment has a relatively larger upper cut-off frequency f_co, it may occupy a smaller area on an IC.
At step 250, the ADC 150 converts the filtered signal into digital data. To retain information contained within a relatively wider frequency range, i.e. within the filtering bandwidth of the filter 140, the ADC 150 may need to be a wideband high-speed ADC. For example, its sampling frequency f_sp may be at least 50 MHz. As another example, the sampling frequency f_sp of the ADC 150 may be at least 100 MHz. To reach such a high sampling frequency, the ADC 150 may include a sigma-delta ADC and one or several decimation filters.
At step 260, the digital circuit 160 processes the digital data to analyze the carriers in the RF signal. Specifically, for each of the carriers within the filtering bandwidth to be analyzed, the digital circuit 160 first performs digital frequency down conversion on the digital data to generate frequency down-converted data. Then, the digital circuit 160 processes the frequency down-converted data to analyze the given carrier. Through this step, the digital circuit 160 may determine whether this carrier is included within the filtering bandwidth, determine a power level of this carrier, or search a nearby second telecommunications device, or retrieve information conveyed through this carrier as presented in the RF signal.
At step 430, the buffered digital data is read from the memory 162. Then, at step 440, the digital circuit 160 analyzes a next carrier. Specifically, the frequency down convertor 164 performs digital frequency down conversion on the digital data to generate frequency down-converted data. This time the frequency shift may be equal to or close to the difference between f_sx and the frequency of the given carrier. The single carrier processing unit 166 then processes the frequency down-converted data to analyze the given carrier as presented in the RF signal. Please note that different carriers may correspond to different frequency down-converted data, respectively.
At step 450, the digital circuit 160 determines whether all the carriers have been analyzed. If the answer if no, it goes back to step 430; if the answer is yes, it moves to the end of the flowchart.
While the digital circuit 160 is performing steps 430, 440, and 450, the other components depicted in
Conventionally, a first telecommunications device may have to use its SX to generate a plurality of carriers successively, and to use its RF FE to synthesize an RF signal with the carriers successively. In other words, the first telecommunications device may have to have several successive RF receiving windows, each for one of the carriers. Each of the RF receiving windows would consume some power and take some time.
In contrast, the first telecommunications device 100 needs only one RF receiving window to generate the digital data that retains information of multiple (e.g. more than five) carriers. Once the digital circuit 160 receives the digital data, the other components depicted in
The embodiments also make it faster and more energy-economic for the first telecommunications device 100 to perform cell search when it needs to know which one of several nearby second telecommunications devices should be selected as its serving telecommunications device.
In addition to enabling analysis of several carriers, the single RF receiving window may even be used to receive signal from a second telecommunications device currently serving the first telecommunications device 100. This may reduce the power consumption of the first telecommunications device 100 even more.
The aforementioned embodiments may also be used to search for amplitude modulated (AM) or frequency modulated (FM) radio stations because each AM/FM radio station may use a specific carrier.
In the foregoing detailed description, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the following claims. The detailed description and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
Number | Date | Country | |
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61680095 | Aug 2012 | US |