JP2004364055A - Frequency synthesizer and radio communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small sized frequency synthesizer corresponding to respective reception signals when different CN ratios are requested at each reception signal, and also to provide radio communication equipment. <P>SOLUTION: Respective noise peak frequencies ωn are set to correspond to the CN ratios to be requested in a plurality of radio communication systems respectively, concerning loop filters 108-1 to 108-N. A control part 102 performs changeover into the loop filter corresponding to the radio communication system under current communication which is analyzed by a mode analyzing part 101. Through the use of the loop filter, filtering is performed in a control voltage corresponding to a phase difference between a reference signal to be outputted from a reference signal generator 103 and a signal to be outputted from a voltage control oscillator 109. Then the oscillation condition of the voltage control oscillator 109 is controlled by the control voltage after filtering. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a frequency synthesizer, and is suitably applied to, for example, a wireless communication device supporting a plurality of wireless communication systems.
[0002]
[Prior art]
FIG. 5 is a block diagram showing a configuration of a conventional frequency synthesizer (see Patent Document 1). In this figure, an oscillation output _fr is output from a voltage controlled oscillation circuit 11, a phase comparison with a reference signal f _ref is performed by a PLL (Phase Locked Loop) 12, and a voltage proportional to the phase difference is given to a loop filter 13. Can be
[0003]
The loop filter 13 includes a cascade-connected lag-lead filter 13A and a low-pass filter 13B. The loop filter 13 supplies the control voltage S1 passed only through the lag lead filter 13A to the input terminal P1 of the analog switch SW1. The control voltage S2 that has passed through both the lag-lead filter 13A and the low-pass filter 13B is supplied to the input terminal P2 of the analog switch SW1 and the differential absolute value circuit 14.
[0004]
When the control voltage S2 supplied from the loop filter 13 changes, the differential absolute value circuit 14 controls switching of the analog switch SW1 using the switching signal S3.
[0005]
The analog switch SW1 switches the switch according to a switching signal S3 output from the differential absolute value circuit 14. Specifically, when the switching signal S3 indicates that high-speed lock-up is prioritized, the control voltage S1, that is, when the input terminal P1 is selected, and when the switching signal S3 indicates that high CN ratio is prioritized. Selects the control voltage S2, that is, the input terminal P2.
[0006]
The control voltage selected by the analog switch SW1 is supplied to the voltage controlled oscillation circuit 11 via a voltage follower 15 for preventing the influence of a load change from affecting the voltage controlled oscillation circuit 11.
[0007]
Thus, the conventional frequency synthesizer is to readiness to the phase difference between the oscillation output f _r and the reference signal f _ref of the voltage controlled oscillation circuit, and controls the oscillation conditions of the voltage controlled oscillation circuit, high-speed lock-up and high CN The ratio is compatible.
[0008]
By the way, in recent years, a plurality of radio communication systems, such as the GSM (Global System for Mobile Communications) system, the PDC (Personal Digital Cellular) system, and the CDMA (Code Division Multiple Access) system, have been developed. It is also conceivable to apply a synthesizer.
[0009]
[Patent Document 1]
JP-A-7-170181 (FIG. 1)
[0010]
[Problems to be solved by the invention]
However, in the above-described conventional frequency synthesizer, when applied to a communication device corresponding to a plurality of wireless communication systems, E _b / N ₀ (the ratio of bit energy to noise) required in each wireless communication system is different. Since the required CN ratio (Carrier to Noise Ratio) differs depending on the communication method because the transmission bandwidth (transmission amount) differs depending on the communication method, a frequency synthesizer corresponding to each communication method must be provided. This leads to an increase in the device scale.
[0011]
In addition, among a plurality of wireless communication systems, it is conceivable to provide a frequency synthesizer adapted to a communication system that requires the highest CN ratio. However, it is difficult to realize such a frequency synthesizer. This also increases the circuit scale.
[0012]
Here, a frequency synthesizer corresponding to a plurality of wireless communication systems has been described as an example in which different CN ratios are required, but the above-described problem may be considered when a different CN ratio is required for each received signal.
[0013]
If the frequency synthesizer forms a signal that does not satisfy the required CN ratio, the receiving sensitivity characteristic deteriorates, so that outgoing / incoming calls cannot be made in a weak electric field area, or the communication quality deteriorates.
[0014]
The present invention has been made in view of the above, and an object of the present invention is to provide a small-sized frequency synthesizer and a wireless communication device corresponding to each received signal when a different CN ratio is required for each received signal.
[0015]
[Means for Solving the Problems]
In order to solve such a problem, a frequency synthesizer according to the present invention includes: a first frequency divider for dividing a reference frequency at a desired frequency division ratio; an oscillator for oscillating a frequency according to a control voltage; A second frequency divider for dividing the oscillated frequency by a desired frequency division ratio; and a control voltage corresponding to a phase difference between the frequencies divided by the first frequency divider and the second frequency divider. Phase comparing means, a plurality of loop filters each having a different noise peak frequency for determining a frequency at which a noise peak appears when filtering the control voltage generated by the phase comparing means, and the loop filter. And a control unit that monitors a signal transmitted from a communication partner and controls the switching unit based on a monitoring result.
[0016]
According to this configuration, since the noise peak frequency is an element that affects the CN ratio of the signal oscillated by the oscillating means, the oscillating means can respond to the signal transmitted from the communication partner by setting the noise peak frequency. While oscillating a signal having a desired frequency, the signal can have a desired CN ratio. Thereby, even when a different CN ratio is required for each signal transmitted from the communication partner, a single frequency synthesizer corresponding to each signal can be realized, and the degradation of speech quality can be avoided, and The scale can be reduced.
[0017]
In the frequency synthesizer of the present invention, in the above-described configuration, the plurality of loop filters are set to noise peak frequencies according to different wireless communication systems, and the control unit determines which wireless communication system among the plurality of wireless communication systems. It is configured to detect whether the switching unit is used and to control the switching unit based on the detection result.
[0018]
According to this configuration, the frequency synthesizer corresponding to the plurality of wireless communication systems is switched by switching the plurality of loop filters for realizing the CN ratio required by the plurality of wireless communication systems according to the communication system during communication. Can be realized by one, and the scale of the apparatus can be reduced.
[0019]
In the frequency synthesizer of the present invention, in the above configuration, the plurality of loop filters are set with noise peak frequencies corresponding to different transmission rates, and the control unit detects a transmission rate of a signal transmitted from a communication partner, A configuration for controlling the switching means based on a detection result is employed.
[0020]
According to this configuration, by switching a plurality of loop filters for realizing a CN ratio corresponding to the transmission rate of the signal according to a transmission rate during communication, a frequency synthesizer corresponding to a plurality of transmission rates can be realized. And the size of the apparatus can be reduced.
[0021]
In the frequency synthesizer of the present invention, in the above configuration, the plurality of loop filters are set with a noise peak frequency corresponding to a different modulation scheme, and the control unit detects a modulation scheme of a signal transmitted from a communication partner, A configuration for controlling the switching means based on a detection result is employed.
[0022]
According to this configuration, by switching a plurality of loop filters for realizing a CN ratio corresponding to the modulation scheme of the signal according to the modulation scheme during communication, one frequency synthesizer corresponding to the plurality of modulation schemes can be realized. And the size of the apparatus can be reduced.
[0023]
A wireless communication apparatus according to the present invention includes a first frequency divider for dividing a reference frequency at a desired frequency division ratio, an oscillator for oscillating a frequency according to a control voltage, and a frequency oscillated by the oscillator. A second frequency dividing means for dividing the frequency by a frequency dividing ratio of; a phase comparing means for generating a control voltage corresponding to a phase difference of the frequency divided by the first frequency dividing means and the second frequency dividing means; A plurality of loop filters each having a different noise peak frequency for determining a frequency at which a noise peak appears when filtering the control voltage generated by the phase comparing means; and a switching means for switching the loop filters. And a control unit that monitors a signal transmitted from a communication partner and controls the switching unit based on the monitoring result.
[0024]
According to this configuration, since the noise peak frequency is an element that affects the CN ratio of the signal oscillated by the oscillating means, the oscillating means can respond to the signal transmitted from the communication partner by setting the noise peak frequency. While oscillating a signal having a desired frequency, the signal can have a desired CN ratio. Thereby, even when a different CN ratio is required for each signal transmitted from the communication partner, a single frequency synthesizer corresponding to each signal can be realized, and the degradation of speech quality can be avoided, and The scale can be reduced.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
The gist of the present invention is to prepare a plurality of loop filters for realizing each CN ratio corresponding to a signal transmitted from a communication partner, and to switch the loop filter according to the transmitted signal.
[0026]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0027]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of the frequency synthesizer according to Embodiment 1 of the present invention. In this figure, a mode analysis unit 101 analyzes which communication method among a plurality of wireless communication methods is used, based on a signal transmitted from a communication partner. As an analysis method, it is conceivable to multiply a received signal by a predetermined spreading code and demodulate the signal to specify that it is a CDMA method or another method. The analysis result, that is, information indicating the communication system used for communication is notified to the control unit 102.
[0028]
The control unit 102 controls the first frequency divider 104, the second frequency divider 105, and the switching unit 107 according to the communication scheme during communication notified from the mode analysis unit 101. Note that the mode analysis unit 101 and the control unit 102 function as control means.
[0029]
The reference signal generator 103 generates a signal serving as a reference of a frequency at which the frequency synthesizer can oscillate, and outputs the generated reference signal to the first frequency divider 104.
[0030]
The first frequency divider 104 changes the frequency division ratio based on the control of the control unit 102, and divides the frequency of the reference signal output from the reference signal generator 103 by the changed frequency division ratio. The frequency-divided signal is output to the phase comparator 106.
[0031]
The second frequency divider 105 changes the frequency division ratio based on the control of the control unit 102, and divides the frequency of the reference signal output from the voltage controlled oscillator 109 at the changed frequency division ratio. The frequency-divided signal is output to the phase comparator 106.
[0032]
The phase comparator 106 compares the phase of the signal output from the first frequency divider 104 with the signal output from the second frequency divider 105, and switches a voltage (control voltage) proportional to the phase difference to the switching unit 107. Give to.
[0033]
The switching unit 107 supplies the voltage provided from the phase comparator 106 to one of the loop filters 108-1 to 108-N based on the control of the control unit 102.
[0034]
In the loop filters 108-1 to 108-N, the noise peak frequencies ωn are set so as to correspond to the CN ratios required in a plurality of wireless communication systems, respectively, and the loop filters 108-1 to 108-N smooth (average) the voltage given from the switching unit 107. The DC voltage obtained by smoothing is applied to the voltage controlled oscillator 109. The noise peak frequency ωn is an element that affects the CN ratio because it determines the frequency at which a noise peak appears when averaging the voltage, and is determined by the capacitance of a capacitor that forms a loop filter. That is, by setting the noise peak frequency ωn, the CN ratio of the averaged signal can be set to the CN ratio corresponding to the signal transmitted from the communication partner.
[0035]
The voltage controlled oscillator 109 oscillates a signal of a frequency corresponding to the DC voltage given from any of the loop filters 108-1 to 108-N, and outputs a signal of a CN ratio corresponding to a wireless communication system during communication. .
[0036]
FIG. 2 is a diagram illustrating a CN ratio versus frequency characteristic in an output signal of the frequency synthesizer. In this figure, the horizontal axis represents frequency, and the vertical axis represents CN ratio. Further, it is assumed that a solid line indicates the wireless communication system A, a dotted line indicates the wireless communication system B, and a dashed line indicates the wireless communication system C. Here, for example, in the wireless communication system A, the frequency _{f A} is used, CN ratio and CN _A is required. Similarly, in the wireless communication system B, the frequency _{f B} is used, CN ratio is required CN _B, the radio communication method C, the frequency _{f C} is used, CN ratio and CN _C is required. The graph shows the CN ratio versus frequency characteristic of the loop filter corresponding to the CN ratio and frequency required in each wireless communication system, as shown in the figure. The noise peak frequency ωn of the loop filter is adjusted so that the desired CN ratio is obtained. Is set. As shown in FIG. 2, it can be seen that each loop filter needs to be switched in order to satisfy all the frequencies and CN ratios required in each communication scheme.
[0037]
Next, the operation of the frequency synthesizer having the above configuration will be described. The mode analysis unit 101 analyzes which wireless communication system is performing communication based on a signal transmitted from a communication partner, and notifies the control unit 102 of the analysis result. The control unit 102 controls the first frequency divider 104, the second frequency divider 105, and the switching unit 107 in accordance with the wireless communication scheme currently being communicated. More specifically, the control unit 102 stores the communicable communication system, the division ratio, and the switching information of the loop filter in association with each other, and stores the division ratio and the switching information corresponding to the communication system in communication. Is output as control information.
[0038]
In the first frequency divider 104, the reference signal output from the reference signal generator 103 is frequency-divided by the control information output from the control unit 102, that is, the frequency division ratio corresponding to the communication system in communication. Similarly, in the second frequency divider 105, the signal output from the voltage controlled oscillator 109 is frequency-divided at a frequency division ratio according to control information of the control unit 102. The divided signals are output to the phase comparator 106.
[0039]
In the phase comparator 106, the phase difference between the signals output from the first frequency divider 104 and the second frequency divider 105 is obtained, and a voltage (control voltage) corresponding to the phase difference is output. The voltage corresponding to the phase difference is provided to the voltage controlled oscillator 109 via any one of the switching unit 107 and the loop filters 108-1 to 108-N, and controls the voltage controlled oscillator 109 so that the phase difference is eliminated.
[0040]
In switching section 107, based on the switching information notified from control section 102 (here, the switching information indicates loop filter 108-1), the voltage supplied from phase comparator 106 is applied to loop filter 108-1. Given to.
[0041]
The loop filter 108-1 is set with a noise peak frequency ωn corresponding to the communication system currently in communication, filters (smooths) the voltage supplied from the switching unit 107, and converts the filtered DC voltage into a voltage-controlled oscillator. Give to 109.
[0042]
The voltage controlled oscillator 109 oscillates a frequency corresponding to the voltage supplied from the loop filter 108-1, and forms a signal having a CN ratio and a frequency required in a communication system during communication. As a result, good communication quality can be ensured in each communication method.
[0043]
As described above, according to the present embodiment, a loop filter for realizing a CN ratio required in a plurality of wireless communication systems is prepared, and by switching to a loop filter corresponding to a communication system in communication, a plurality of loop filters are provided. A single frequency synthesizer corresponding to the communication system can be realized, the size of the device can be reduced, and the deterioration of the communication quality in each communication system can be avoided.
[0044]
(Embodiment 2)
FIG. 3 is a block diagram showing a configuration of the frequency synthesizer according to Embodiment 2 of the present invention. However, parts in FIG. 3 common to FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed description thereof will be omitted. FIG. 3 differs from FIG. 1 in that mode analysis section 101 is changed to transmission rate analysis section 301 and loop filters 108-1 to 108-N are changed to loop filters 302-1 to 302-N. is there.
[0045]
The transmission rate analysis unit 301 analyzes at what transmission rate a signal transmitted from a communication partner was transmitted based on information included in the signal. The transmission rate changes, for example, according to the bandwidth of the signal, and the CN ratio also changes according to the bandwidth. Specifically, when the transmission rate is high, the bandwidth is wide, and the CN ratio tends to decrease. Conversely, when the transmission rate is low, the bandwidth is narrow, and the CN ratio tends to improve. The specified communication method is notified to the control unit 102. Note that the transmission rate analysis unit 301 and the control unit 102 function as control means.
[0046]
Further, the loop filters 302-1 to 302-N each have a noise peak frequency ωn set so as to realize a CN ratio corresponding to a predetermined transmission rate, and smooth the voltage supplied from the switching unit 107 (average). The DC voltage obtained by smoothing is applied to the voltage controlled oscillator 109.
[0047]
As described above, according to the present embodiment, a plurality of loop filters for realizing a CN ratio corresponding to the transmission rate of a signal transmitted from a communication partner are prepared, and the loop filter is switched to a loop filter corresponding to the transmission rate during communication. This makes it possible to realize a single frequency synthesizer corresponding to a plurality of transmission rates, to reduce the size of the device, and to avoid deterioration in speech quality in each communication method.
[0048]
(Embodiment 3)
FIG. 4 is a block diagram showing a configuration of the frequency synthesizer according to Embodiment 3 of the present invention. However, parts in FIG. 4 common to FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed description thereof will be omitted. 4 differs from FIG. 1 in that mode analysis section 101 is changed to adaptive modulation analysis section 401 and loop filters 108-1 to 108-N are changed to loop filters 402-1 to 402-N. is there.
[0049]
Adaptive modulation analysis section 401 analyzes which modulation scheme the signal transmitted from the communication partner has been transmitted based on information included in the signal. There is also a correspondence between the modulation scheme and the CN ratio. When the modulation multi-level number is high (for example, 16QAM), the CN ratio tends to decrease, and when the modulation multi-level number is low (for example, QPSK), the CN ratio is low. Tends to improve. The specified communication method is notified to the control unit 102. The adaptive modulation analysis unit 401 and the control unit 102 function as control means.
[0050]
The noise peak frequency ωn is set in each of the loop filters 402-1 to 402-N so as to realize a CN ratio corresponding to a predetermined modulation scheme (modulation multi-level number). The obtained voltage is smoothed (averaged), and the smoothed DC voltage is supplied to the voltage controlled oscillator 109.
[0051]
As described above, according to the present embodiment, a plurality of loop filters for realizing the CN ratio corresponding to the modulation scheme of the signal transmitted from the communication partner are prepared, and the loop filter is switched to the loop filter according to the modulation scheme during communication. This makes it possible to implement a single frequency synthesizer that supports a plurality of modulation schemes, reduce the size of the device, and avoid deterioration in speech quality in each communication scheme.
[0052]
【The invention's effect】
As described above, according to the present invention, a loop filter for realizing each CN ratio corresponding to a signal transmitted from a communication partner is prepared, and the loop filter is switched according to the transmitted signal. In addition, a single frequency synthesizer corresponding to each of the CN ratios required by a plurality of wireless communication systems can be realized, thereby reducing the size of the device and avoiding deterioration of the communication quality in each communication system. can do.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a frequency synthesizer according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a CN ratio versus frequency characteristic of an output signal of the frequency synthesizer. FIG. FIG. 4 is a block diagram showing a configuration of a frequency synthesizer according to a third embodiment of the present invention. FIG. 5 is a block diagram showing a configuration of a conventional frequency synthesizer.
101 Mode analysis unit 102 Control unit 103 Reference signal generator 104 First frequency divider 105 Second frequency divider 106 Phase comparator 107 Switching units 108-1 to 108-N, 302-1 to 302-N, 402-1 ~ 402-N
Loop filter 109 Voltage controlled oscillator 301 Transmission rate analyzer 401 Adaptive modulation analyzer

Claims (5)

First frequency dividing means for dividing the reference frequency by a desired frequency dividing ratio;
Oscillating means for oscillating a frequency according to the control voltage;
Second frequency dividing means for dividing the frequency oscillated by the oscillating means at a desired frequency dividing ratio;
Phase comparing means for generating a control voltage corresponding to a phase difference between the frequencies divided by the first frequency dividing means and the second frequency dividing means;
When filtering the control voltage generated by the phase comparison means, a plurality of loop filters that are set so that noise peak frequencies that determine the frequency at which a noise peak appears differ from each other,
Switching means for switching the loop filter,
A control unit that monitors a signal transmitted from a communication partner and controls the switching unit based on a monitoring result,
A frequency synthesizer comprising: The plurality of loop filters are set noise peak frequencies according to different wireless communication systems,
2. The frequency synthesizer according to claim 1, wherein the control unit detects which one of a plurality of wireless communication systems is used, and controls the switching unit based on a detection result. 3. . The plurality of loop filters are set noise peak frequencies according to different transmission rates,
The frequency synthesizer according to claim 1, wherein the control unit detects a transmission rate of a signal transmitted from a communication partner, and controls the switching unit based on a detection result. The plurality of loop filters are set noise peak frequencies according to different modulation schemes,
2. The frequency synthesizer according to claim 1, wherein the control unit detects a modulation scheme of a signal transmitted from a communication partner, and controls the switching unit based on a detection result. First frequency dividing means for dividing the reference frequency by a desired frequency dividing ratio;
Oscillating means for oscillating a frequency according to the control voltage;
Second frequency dividing means for dividing the frequency oscillated by the oscillating means at a desired frequency dividing ratio;
Phase comparing means for generating a control voltage corresponding to a phase difference between the frequencies divided by the first frequency dividing means and the second frequency dividing means;
When filtering the control voltage generated by the phase comparison means, a plurality of loop filters that are set so that noise peak frequencies that determine the frequency at which a noise peak appears differ from each other,
Switching means for switching the loop filter,
A control unit that monitors a signal transmitted from a communication partner and controls the switching unit based on a monitoring result,
A wireless communication device comprising:

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