Receiving apparatus with a single set of channels for processing plural sets of in-phase and quadrature phase signals

The present invention relates to a receiving apparatus of a communication system, which comprises a receiving module, a selection unit, and a processing module. The receiving module receives an input signal and produces a first signal and a second signal. The phases of the first and the second signals are different. The selection unit receives the first and the second signals, and switches for outputting the first or the second signal. The processing module receives and processes the first and the second signals, and produces an output signal. Thereby, the present invention uses the selection unit for processing two phase signals via a set of channels. Thereby, circuit area and power consumption can be reduced, and hence achieving the purpose of saving cost.

FIELD OF THE INVENTION

The present invention relates generally to a receiving apparatus, and particularly to a receiving apparatus of a communication system.

BACKGROUND OF THE INVENTION

In the radio-frequency (RF) transmission architectures of modern wireless communication systems, there are two mainstreams of receiver architectures that are highly integrated as well as providing multiple modes. One is the low intermediate frequency (IF) receiver; the other is the direct conversion, or zero IF, receiver. These two types of receivers own complementary pros and cons, and are extensively valued and applied in the industry. The former receiver can avoid problems of DC shifts and low-frequency noises. However, it suffers from interferences by image signals. On the contrary, the latter receiver has little interferences by image signals. Nevertheless, it has the problems of DC shifts and low-frequency noises.

At present, low- and intermediate-frequency architectures are widely applied to transmitting and receiving sides of wireless communication. Thereby, the problems of image interference and circuit areas in low- and intermediate-frequency receiver architectures have become a major issue in the industry as well as in the academia. The most popular method is, in a low- and intermediate-frequency or an ultra-low- and intermediate-frequency receiver architecture, to use a mixing circuit to down-convert the wireless RF signal received by an antenna and output a pair of orthogonal signals. A complex filter architecture is then used for processing the pair of signals. Starting from the output of a low noise amplifier (LNA) in a general image rejection receiver architecture, passing mixers, filters, amplifiers, analog-to-digital converters, and till the output of a baseband processing circuit, signals are divided into two phases, namely, 0-degree (in-phase, I) and 90-degree (quadrature, Q) signals. Consequently, two sets of mixers, filters, amplifiers, and analog-to-digital converters are required, hence consuming more circuit area and power consumption as well as widening asymmetry between I and Q signals.

Accordingly, the present invention provides a novel receiving apparatus of a communication system, which can avoid using two sets of amplifiers and analog-to-digital converters. Thereby, circuit area and power consumption can be reduced, and the problems described above can be solved.

SUMMARY

An objective of the present invention is to provide a receiving apparatus of a communication system, which uses only a set of channels for processing in-phase and the quadrature signals. Thereby, circuit area and power consumption can be reduced, and hence achieving the purpose of saving cost.

Another objective of the present invention is to provide a receiving apparatus of a communication system, which uses an image rejection filter for eliminating image interferences between the two signals with different phases.

Still another objective of the present invention is to provide a receiving apparatus of a communication system, which adjusts the ratio of the down-converted frequency of a mixer to a switching frequency for reducing power consumption of the receiving apparatus, and hence achieving the purpose of saving power.

The receiving apparatus of a communication system according to the present invention comprises a receiving module, a selection unit, and a processing module. The receiving module receives an input signal and produces a first signal and a second signal. The phases of the first and the second signals are different. The selection unit receives the first and the second signals, and switches for outputting the first or the second signal. The processing module receives and processes the first and the second signals, and produces an output signal. Thereby, the present invention uses the selection unit for switching outputting the first or the second signal to the processing module via a set of channels. Thereby, circuit area and power consumption can be reduced, and hence achieving the purpose of saving cost.

In addition, the processing module produces a selection signal and transmits the selection signal to the selection unit for controlling the selection unit to switch outputting the first or the second signal.

DETAILED DESCRIPTION

FIG. 1shows a block diagram according to a preferred embodiment of the present invention. As shown in the figure, the receiving apparatus1of a communication system according to the present invention comprises a receiving module10, a selection unit20, and a processing module30. The receiving module10receives an input signal and produces a first signal and a second signal. In other words, the receiving module10receives a wireless RF signal as the input signal and produces the first and the second signals. The first signal comprises a first in-phase signal IPand a second in-phase signal IN, where the first in-phase signal IPdiffers second in-phase signal INby 180 degrees and forming a set of difference signals. The second signal comprises a first quadrature-phase signal Qpand a second quadrature-phase signal QN, where the first quadrature-phase signal Qpdiffers second quadrature-phase signal QNby 180 degrees and forming a set of difference signals. Besides, the phases of the first and the second signals are different. According to the present embodiment, the phase difference between the first and the second signals is 90 degrees; the phase difference between the first in-phase signal IPand the first quadrature-phase signal QPis 90 degrees; and the phase difference between the second in-phase signal INand the second quadrature-phase signal QNis 90 degrees.

The selection unit20is coupled to the receiving module10and receives the first and the second signals. The selection unit20switches outputting the first or the second signal. That is to say, the selection unit20firstly outputs the first signal, and then outputs the second signal the next time for subsequent processes by the processing module30. The processing module30is coupled to the selection unit20and receives the first and the second signals sequentially. In addition, the processing module30processes the first and the second signals and produces an output signal. The processing module produces a selection signal and transmits the selection signal to the selection unit20for controlling the selection unit20to switch outputting the first or the second signal. Namely, the processing module30produces the selection signal according to a switching frequency, and transmits the selection signal to the selection unit20for controlling the selection unit20to output the frequencies of the first and the second signals. Thereby, the processing module30can correctly receive the first and the second signals according to the switching frequency for further processes. According to the present invention, the selection unit20is used for switching outputting the first or the second signal. The selection unit20outputs a set of in-phase signals (IP, IN) or quadrature-phase signals (QP, QN) at a time, and thus achieving using only one set of channels for transmitting and processing two sets of in-phase and quadrature-phase signals. Accordingly, circuit area and power consumption can be reduced, and hence achieving the purpose of saving cost.

The receiving module10according to the present invention comprises an antenna12and a mixing circuit14. The antenna12receives the wireless RF signal as the input signal. The mixing circuit14is coupled to the antenna12and receives the input signal received by the antenna12. Besides, the mixing circuit14mixes the input signal with at least a mixing signal and produces the first in-phase signal IP, the first quadrature-phase signal Qp, the second in-phase signal IN, and the second quadrature-phase signal QN. The mixing circuit14comprises a first mixer140and a second mixer142. The first mixer140mixes the input signal with a first mixing signal according to a down-converted frequency and produces the first signal; the second mixer142mixes the input signal with a second mixing signal according to the down-converted frequency and produces the second signal. The phases of the first and the second mixing signals are different. According to the present embodiment, the phase difference therebetween is 90 degrees. Thereby, the phases of the first and the second signals differ by 90 degrees.

In addition, the mixing circuit14according to the present invention further comprises a signal-generating unit144and a phase shifter146. The signal-generating unit144is used for producing the first mixing signal. The phase shifter146is coupled to the signal-generating unit144for receiving and shifting the phase of the first mixing signal. Then, the phase shifter146transmits the second mixing signal to the second mixer142to make the phases of the first and the second mixing signals different. The signal-generating unit144transmits the first mixing signal to the first mixer140. The phase shifter146transmits the second mixing signal to the second mixer142. According to the present embodiment, the phase shifter146is coupled between the signal-generating unit144and the second mixer142for shifting the phase of the first mixing signal and thus making the phases of the first the second mixing signals differ by 90 degrees. Likewise, the phase shifter146can also be coupled between the signal-generating unit144and the first mixer140(not shown in the figure). The signal-generating unit144is a voltage-controlled oscillator (VCO). Because the mixing circuit14described above is well known to a person having ordinary skill in the art, its details will not be described further.

Moreover, the receiving module10according to the present invention further comprises an amplifier16, a first filter18, and a second filter19. The amplifier16is used for amplifying the input signal and transmitting the amplified input signal to the mixing circuit14. The amplifier16is a low noise amplifier (LNA). The first filter18and the second filter19are coupled to the mixing circuit14for filtering the first and the second signals, respectively, and transmitting the filtered first and second signals to the processing module30. The first and the second filters18,19are general filters. Because the filters described above are well known to a person having ordinary skill in the art, their details will not be described further.

The processing module30according to the present invention comprises an analog-to-digital conversion unit300and a baseband processing circuit302. The analog-to-digital conversion unit300is coupled to the selection unit20and converts the first or the second signal to a digital signal. The baseband processing circuit302is coupled to the analog-to-digital conversion unit300and process the digital signal produced by the analog-to-digital conversion unit300and thus producing the output signal. Meanwhile, the baseband processing circuit302produces the selection signal according to the switching frequency and transmits the selection signal to the selection unit20for controlling the switching frequency of the selection unit20.

The processing module30further comprises an amplifier304, which is coupled between the selection unit20and the analog-to-digital conversion unit300for amplifying and transmitting the first and the second signals to the baseband processing circuit302.

In addition, the processing module30further comprises a filter306, which is disposed in the baseband processing circuit302for filtering the image interference in the digital signal output by the analog-to-digital conversion unit300. The filter306receives the first in-phase signal Ip, the first quadrature-phase signal QP, the second in-phase signal IN, and the second quadrature-phase signal QNand filters the image interference therein. Namely, the image interference in the first and the second signals is filtered by the filter306, which is an image rejection filter.

FIG. 2shows a circuit diagram of a selection unit according to a preferred embodiment of the present invention. As shown in the figure, because the first signal comprises the first in-phase signal IPand the second in-phase signal IN, and the second signal comprises the first quadrature-phase signal QPand the second quadrature-phase signal QN, the selection unit20according to the present invention comprises a first switch200, a second switch202, a third switch204, and a fourth switch206. The first switch200receives the first in-phase signal IP; the second switch202receives the first quadrature-phase signal QP; the third switch204receives the second in-phase signal IN; and the fourth switch206receives the second quadrature-phase signal QN. The selection unit20can switch outputting the first in-phase signal IPand the second in-phase signal IN, or the first quadrature-phase signal QPand the second quadrature-phase signal QNsequentially according to the selection signal. According to the present embodiment, the output of the second switch202is coupled to the output of the first switch200for forming a first switching module; the output of the fourth switch206is coupled to the output of the third switch204for forming a second switching module. The first, the second, the third, and the fourth switches200,202,204,206are controlled by the selection signal, so that the selection unit20can switch outputting a set of in-phase signals or a set of quadrature-phase signals sequentially according to the selection signal. In other words, the selection unit20outputs the first and the second signals sequentially via the first and the second switching modules. The selection signal comprises a first clock signal SEL and a second clock signalSEL, which are the inverses of the other. The first switch200and the second switch202are controlled by the first clock signal SEL and the second click signalSEL, respectively; the third switch204and the fourth switch206are controlled by the first clock signal SEL and the second click signalSEL, respectively. Thereby, the selection unit20outputs a set of in-phase signals or a set of quadrature-phase signals according to the first clock signal SEL and the second click signalSELof the selection signal. Consequently, when the first clock signal SEL closes the first and the third switches200,204and the second clock signalSELopens the second and the fourth switches202,206, the selection unit20output the first in-phase signal Ipand the second in-phase signal IN. On the contrary, when the first clock signal SEL opens the first and the third switches200,204and the second clock signalSELcloses the second and the fourth switches202,206, the selection unit20output the first quadrature-phase signal QPand the second quadrature-phase signal QN. Thereby, by using the selection unit20, circuit area and power consumption can be reduced, and thus the purpose of saving cost can be achieved.

FIGS. 3A to 3Dshow waveforms of the down-converted frequency, switching frequency, and sampling frequency according to preferred embodiments of the present invention. As shown in the figures, the analog-to-digital conversion unit300samples the first or the second signal output by the selection unit20according to a sampling frequency and converts it to a digital signal. According to the sampling theorem of analog-to-digital conversion, at least two samples are required in a period of a signal. Namely, the sampling frequency of the analog-to-digital conversion unit300depends on the frequency of the first or the second signal output by the selection unit20. When the down-converted frequency of the mixers140,142maintains a ratio to the switching frequency of the selection unit20and the switching frequency is greater than the down-converted frequency, the sampling frequency of the analog-to-digital conversion unit300can be reduced, which, in turn, reduces the power consumption of the receiving apparatus1and hence achieving the purpose of saving power.

As shown inFIGS. 3A to 3D, the waveform of the first in-phase signal IPis used as an example. However, the present invention is not limited to the waveform of the first in-phase signal IP. The waveform can also be the second in-phase signal IN, the first quadrature-phase signal QP, and the second quadrature-phase signal QN. For simplicity, only the waveform of the first in-phase signal IPis used in the present embodiments. First, as shown inFIG. 3A, when the down-converted frequency of the mixers140,142is 2.5 MHz, the switching frequency of the selection unit20is 2.5 MHz, and the waveform of the first in-phase signal IPoutput by the first mixer140is a sine wave50, the selection unit20produces a switching waveform52according to the first in-phase signal IPoutput by the switching frequency, as shown inFIG. 3A. For complying with the sampling theorem, the sampling frequency of the analog-to-digital conversion unit300at least needs to be 5 MHz. The analog-to-digital conversion unit300produces a sampling waveform54according to the sampling frequency, as shown inFIG. 3A. For simplicity, only the sampling points of corresponding to the first in-phase signal IPare plotted in the sampling waveform. As shown inFIG. 3B, when the switching frequency of the selection unit20is changed to 5 MHz and the selection unit20produces a switching waveform62according to the switching frequency, the sampling frequency of the analog-to-digital conversion unit300at least needs to be 10 MHz, and a sampling waveform64is produced according to the sampling frequency. As shown inFIG. 3C, when the switching frequency of the selection unit20is changed to 10 MHz and the selection unit20produces a switching waveform72according to the switching frequency, the sampling frequency of the analog-to-digital conversion unit300at least needs to be 10 MHz, and a sampling waveform74is produced according to the sampling frequency.

As shown inFIG. 3D, when the switching frequency of the selection unit20is changed to 20 MHz and the selection unit20produces a switching waveform82according to the switching frequency, the sampling frequency of the analog-to-digital conversion unit300can be 20 MHz or 10 MHz, and a sampling waveform84or86is produced according to the sampling frequency. According to the sampling theorem, at least two samples are required in a period of a signal. Thereby, according to the present embodiment, the sampling frequency of the analog-to-digital conversion unit300can be 10 Mhz for complying with the sampling criterion. Accordingly, the power consumption of the receiving apparatus1is reduced, and thus achieving the purpose of saving power. Of course, the sampling frequency of the analog-to-digital conversion unit300can also be 20 MHz for enhancing conversion accuracy of the analog-to-digital conversion unit300.

According to the description above, when the switching frequency is greater than the down-converted frequency and a ratio of down-converted frequency to switching frequency is greater than a first threshold value, to the switching frequency, the sampling frequency is equal to the switching frequency. As shown inFIG. 3C, when the switching frequency (10 MHz) is greater than the down-converted frequency (2.5 MHz) by 4 times, the sampling frequency can be 10 MHz. If the ratio is greater than a second threshold value, the sampling frequency should be smaller than the switching frequency. As shown inFIG. 3D, when the switching frequency (20 MHz) is greater than the down-converted frequency (2.5 MHz) by 8 times, the sampling frequency can be 10 MHz only for complying with the sampling criterion. In other words, if the ratio of the down-converted frequency to the switching frequency is an integer M and the multiples of the ratio is greater than a certain threshold value, the sampling frequency of the analog-to-digital conversion unit300can be reduced, which, in turn, reduces the power consumption of the receiving apparatus1and thus achieving the purpose of saving power. Of course, the requirement of the ratio of the down-converted frequency to the switching frequency being an integer M is only used for description. In practice, the ratio needs not be an integer.

FIG. 4shows a block diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present embodiment and the one inFIG. 1is that a filter40according to the present embodiment is coupled to the output of the selection unit20for filtering the first and second signals output by the selection unit20. Because the filter40is disposed at the output of the selection unit40, the filter40needs to filter only the first signal or the second signal. Thereby, the filter40according to the present embodiment can reduced the circuit area effectively, and hence reducing the overall circuit area.

FIG. 5shows a block diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present embodiment and the previous one is that the receiving apparatus1according to the present embodiment disposes the filter306in the baseband processing circuit302only for filtering the image interference of the digital signal output by the analog-to-digital conversion unit300, namely, filtering the image interference of the first and the second signals. Meanwhile, the noises in the first and the second signals can be filtered as well. Besides, the filter306is an image rejection filter.

To sum up, the receiving module of a communication system according to the present invention uses a selection unit to receive a first signal and a second signal of a switching module, and switches for outputting one of the first and the second signals to a processing module. The processing module receives and processes the first and the second signals, and produces an output signal. The processing module also produces a selection signal according to a switching frequency and transmits the selection signal to the selection unit for controlling the selection unit to switch outputting the first or the second signal. Thereby, the present invention uses the selection unit for processing two phase signals via a set of channels. Thereby, circuit area and power consumption can be reduced, and hence achieving the purpose of saving cost.