JP3753050B2 - Communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication device configured to operate a plurality of communication systems based on an oscillation signal output from an oscillation circuit.
[0002]
[Prior art]
In a communication device, for example, a carrier wave signal is required to transmit a signal, and a signal having the same frequency as that of the carrier wave signal is used to demodulate a received signal, but in order to supply such a frequency signal, Some use a PLL oscillation circuit. When an oscillation signal output from the PLL oscillation circuit is used, the oscillation signal is generally configured to pass through a buffer circuit in order to absorb and stabilize the fluctuation of the output level. Such a buffer circuit operates a transistor in a non-linear region (saturation region), thereby performing a buffer operation (buffering) in which the output level becomes substantially constant even when the amplitude of the input signal slightly varies. ing.
[0003]
However, when the transistor of the buffer circuit is operated in a non-linear region, the output signal waveform of the PLL oscillation circuit is distorted, and therefore harmonic components having the fundamental frequency of the signal are generated at the same time. Since harmonic components are not necessary for the operation of the communication device, a low-pass filter is disposed on the output side of the buffer circuit to filter the harmonic components and finally use only the fundamental component. ing.
[0004]
[Problems to be solved by the invention]
By the way, in recent years, since communication devices have been remarkably miniaturized and multi-functionalized, there are some devices in which a plurality of different communication systems are mounted in one device. In such a communication device, the frequency of a necessary signal may be different for each system. In such a case, if an oscillation circuit is configured for each frequency or a separate multiplier is arranged, the cost is correspondingly increased. Will rise. Conversely, it is conceivable to divide the frequency by setting the oscillation frequency of the oscillation circuit to the highest frequency required by the system, but in that case, an increase in power consumption, measures against unnecessary radiation, and the like become problems.
[0005]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a communication device that can share one oscillation circuit with a simple configuration when a plurality of communication systems are mounted. is there.
[0006]
[Means for Solving the Problems]
According to the communication device of claim 1, when the buffer circuit buffers the oscillation signal output from the oscillation circuit, the buffer circuit also generates and outputs a harmonic component having the fundamental frequency of the oscillation signal. To do. Each of the plurality of filter circuits has a frequency characteristic set so as to selectively output any one of the plurality of frequency signals output from the buffer circuit, and the frequency signal output through each of the filter circuits. Are used by being supplied to each communication system.
[0007]
That is, the harmonic components generated as a by-product by the combination of the oscillation circuit and the buffer circuit are appropriately discriminated by a plurality of filter circuits, so that a complicated circuit is not required. And Different Even when a plurality of communication systems are installed, it is possible to share a single oscillation circuit with a simple configuration and supply a necessary frequency signal to each, so that the apparatus can be configured at low cost.
[0008]
According to the communication device of the second aspect, the buffer circuit outputs the output levels of the plurality of frequency signals used in the plurality of communication systems relatively higher than the output levels of the other frequency signals. Configured. With this configuration, the buffer circuit outputs the frequency signal that is actually used by the communication system so that the level of the frequency signal is increased in advance, so that the frequency discrimination in the filter circuit disposed in the subsequent stage can be further improved. It can be done easily.
[0009]
According to the communication device of the third aspect, one of the plurality of communication systems is a radiotelephone system, and the other is a GPS signal receiving system. That is, in recent years, a mobile phone configured to be able to use a position specifying system realized on the IS (Interim Standard) 801 standard has been put into practical use. In the position specifying system, a mobile phone is transmitted from a GPS satellite. A system for receiving signals is installed. In this type of mobile phone, the local oscillation frequency used in the radio telephone system is in the 700 MHz band, and the local oscillation frequency used in the GPS signal receiving system is in the 1.4 GHz band. That is, since the frequency ratio of the signals used in both is approximately double, the present invention can be effectively applied to such a communication apparatus.
[0010]
According to the communication device of the fourth aspect, the low-pass filter type matching circuit in the buffer circuit is configured to include the capacitor connected between the collector resistance and the common connection point of the coil and the ground, and 3 of the fundamental wave f1. The harmonic component more than twice is cut off and impedance matching is performed with respect to the second harmonic f2. The high-pass filter type matching circuit is connected to the subsequent stage of the low-pass filter type matching circuit and is configured to perform impedance matching with respect to the fundamental wave f1.
[0011]
That is, since the radio telephone system and the GPS signal receiving system use the signals of the two frequencies f1 and f2 output from the buffer circuit, ideally, the output levels of these two signals are increased, and the other three times It is preferable to lower the output level of the above harmonic components. Therefore, with such a configuration, in the configuration of the third aspect, it becomes possible to more easily discriminate the frequency in the filter circuit disposed in the subsequent stage of the buffer circuit.
[0012]
In the buffer circuit in the conventional circuit, a matching circuit that extracts the signal output from the collector of the transistor and matches the fundamental wave f1 to the line impedance (for example, 50Ω), and a low-pass filter for filtering higher harmonic components above f2 are provided. It was provided. Assuming that this configuration is applied as it is to the communication device of claim 3 where up to the second harmonic f2 is required, the low-pass filter is set so as to filter higher harmonic components having a frequency f3 or higher. A matching circuit for matching the harmonic wave f2 is further required. In such a circuit configuration, the number of necessary elements increases, and the matching conditions of the two matching circuits cause interference with each other, and the matching between the two is not necessarily optimal.
[0013]
On the other hand, according to the configuration of claim 4, a low-pass filter type matching circuit that cuts off a harmonic component more than three times the fundamental wave f1 is connected between the collector resistance and the common connection point of the coil and the ground. Configured with a capacitor. That is, the coil becomes a component of a low-pass filter together with the capacitor, and the matching circuit also has a function as a filter circuit, so that necessary elements can be reduced.
[0014]
Further, since the subsequent high-pass filter type matching circuit is a high-pass filter configured to match the fundamental wave f1, it hardly affects the second harmonic f2. Therefore, the required two frequency signals f1 and f2 can be satisfactorily matched without interfering with each other.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a mobile phone configured to be able to use a position specifying system realized on the IS801 standard will be described with reference to the drawings. In a system implemented on the IS801 standard, when a mobile phone receives a base station identification number (Base-ID) representing the base station from several base stations, the mobile phone receives a number of the received base station identification numbers. The base station represented by one of the base station identification numbers is determined as a communication base station that communicates with itself, and the base station identification number representing the base station determined as the communication base station is the location information. Send to server.
[0016]
When the location information server receives the base station identification number from the cellular phone, the location server identifies the approximate location of the cellular phone based on the received base station identification number, and the cellular phone captures a GPS (Grobal Positioning System) satellite. Assist information useful for this is transmitted to the mobile phone. Then, when the mobile phone receives the assist information from the position information server, the mobile phone captures the GPS satellite based on the received assist information. According to this, the mobile phone can reduce the load by the amount of GPS satellites that can be captured based on the assist information received from the location information server, and the time until the positioning is started. There is an advantage that it can be shortened.
[0017]
FIG. 5 schematically shows a functional block and a peripheral configuration of the mobile phone. The mobile phone (communication device) 1 includes a control unit 2, GPS (G l obal Positioning System) GPS receiving unit (GPS signal receiving system) 4 for capturing satellite 3, CDMA transmitting / receiving unit (wireless telephone system) 5, microphone 6 and voice processing unit 8 for processing transmission / reception voice input / output to / from speaker 7 , An operation unit 9, a display unit 10, a storage unit 11 composed of a RAM and a ROM, a timing unit 12 having a timing function, and the like.
[0018]
The control unit 2 is constituted by a microcomputer. The GPS receiving unit 4 wirelessly processes the received GPS signal, and includes CDMA. Sending and receiving The communication unit 5 performs telephone processing according to a CDMA (Code Division Multiple Access) system. The operation unit 9 includes a keypad on which a number of keys such as a “call start” key, a “call end” key, and “number” keys “0” to “9” are arranged. The display unit 10 includes a liquid crystal display that displays date / time, telephone number, and the like.
[0019]
In such a configuration, when the operation unit 9 performs an operation for instructing the start of positioning by the user, for example, the mobile phone 1 has a base station identification number representing the base station 13 from several base stations 13. (Base-ID) is received, and the base station 13 represented by any one of the received base station identification numbers is identified based on, for example, the received electric field strength of the received radio wave. The base station identification number representing the base station 13 determined as the communication base station is determined through the base station 13, the base station controller 14 and the CDMA telephone network 15. Send to server 16.
[0020]
When receiving the base station identification number from the mobile phone 1, the location information server 16 specifies the approximate location of the mobile phone 1 based on the received base station identification number, and the mobile phone 1 captures the GPS satellite 3. Assist information useful for the transmission is transmitted to the mobile phone 1 through the CDMA telephone network 15, the base station controller 14 and the base station 13. When the mobile phone 1 receives the assist information from the position information server 16, the mobile phone 1 captures the GPS satellite 3 based on the received assist information. When the GPS signal transmitted from the captured GPS satellite 3 is received by the GPS receiver 4, the positioning is performed based on the received GPS signal.
[0021]
FIG. 1 is a functional block diagram showing a configuration of the mobile phone 1 mainly including a GPS receiving unit 4 and a CDMA transmitting / receiving unit 5. The received signal processing unit 17 is arranged inside the control unit 2 and performs demodulation processing (orthogonal demodulation) of the received signal.
[0022]
The GPS receiver 4 includes a band pass filter (BPF) 18, a reception amplifier (low noise amplifier) 19, a BPF 20, a mixer 21, a BPF 22, and the like. The GPS signal is received by the antenna 23, given to the BPF 18 through the diplexer 24, and only the signal in the 1575.42 MHz band is output to the reception amplifier 19. The signal amplified by the reception amplifier 19 is supplied to the mixer 21 via the BPF 20, and the reception signal and the local frequency signal of 1.4652 GHz are mixed. The output signal of the mixer 21 becomes an intermediate frequency signal of 110.22 MHz, and is output to the reception signal processing unit 17 via the BPF 22.
[0023]
On the other hand, the CDMA transceiver unit 5 includes a CDMA receiver 25 and a CDMA transmitter 26. The CDMA receiver 25 includes a reception amplifier 27, a BPF 28, a mixer 29, a BPF 30, and the like. A signal received by the antenna 23 is given to the reception amplifier 27 via the diplexer 24 and the duplexer 31. The signal amplified by the reception amplifier 27 is supplied to the mixer 29 via the BPF 28, and the reception signal and the local frequency signal in the 700 MHz band are mixed. Then, the output signal of the mixer 29 becomes an intermediate frequency signal of 110 MHz, and is output to the reception signal processing unit 17 via the BPF 30.
[0024]
Although the intermediate frequency is 110.22 MHz on the GPS side and 110 MHz on the CDMA side, the difference between these intermediate frequencies can be achieved by switching the oscillation frequency of the second oscillator (not shown) in the reception signal processing unit 17. To absorb. However, the frequency of the PLL oscillation circuit 37 may be matched so that the GPS side and the CDMA side have the same intermediate frequency.
[0025]
The CDMA transmission unit 26 includes a transmission signal processing unit 32, a BPF 33, transmission amplifiers (power amplifiers) 34A and 34B, a coupler 35, a detector 36, and the like. The transmission signal processing unit 32 performs modulation processing (orthogonal modulation) of the transmission signal, and the output signal is given to the transmission amplifiers 34A and 34B via the BPF 33. The transmission signal processing unit 32 is provided with a local frequency signal in the 700 MHz band in order to perform modulation processing.
[0026]
The transmission amplifiers 34A and 34 amplify and output the transmission signal, and the output signal is transmitted to the outside from the antenna 23 via the coupler 35, the duplexer 31, and the diplexer 24. The coupler 35 is provided to give a part of the transmission signal to the detector 36. The detector 36 detects the transmission power level and outputs it to a control unit (not shown).
[0027]
Here, the local frequency signals supplied to the GPS receiver 4, the CDMA receiver 25, and the CDMA transmitter 26 are supplied through the following paths. That is, the PLL oscillation circuit 37 is configured to transmit and output a frequency signal in the 700 MHz band, and the output signal is distributed to two systems of the GPS side and the CDMA side via the buffer circuit 38 and the distributor 39. .
[0028]
The mixer 21 of the GPS receiver 4 is supplied with a frequency signal from a distributor 39 via a high pass filter (HPF, filter circuit) 40. The mixer 29 of the CDMA receiving unit 25 and the transmission signal processing unit 32 of the CDMA transmitting unit 26 pass through a low-pass filter (LPF, filter circuit) 41 from the distributor 39 and are further connected to the receiving side by the distributor 42. The frequency signal is assigned to the transmitting side.
[0029]
Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 2 is a functional block diagram centering on the frequency 4 signal supply system described above, and explains the operation of this embodiment. The PLL oscillation circuit 37 has a well-known configuration and forms a loop by connecting a phase comparison unit 37a, an LPF 37b, and a VCO (Voltage Controlled Oscillator) 37c. A signal output from the PLL oscillation circuit 37 is a sine wave, and includes only a single frequency f1 (= 700 MHz band) as a frequency component.
[0030]
Although the buffer circuit 38 will be described in detail later, the basic operation is the same as in the prior art, and the output level of the VCO 37c can be controlled by operating the internal transistor in the nonlinear region with the signal output from the PLL oscillation circuit 37. Even when it fluctuates, buffering is performed so that the output level of the frequency signal is constant. As a result, the output signal waveform of the buffer circuit 38 is distorted, and the frequency components include the second harmonic f2, the third harmonic f3,... Having the frequency f1 as a fundamental wave. .
[0031]
When the output signal of the buffer circuit 38 is distributed to two systems via the distributor 39, one is outputted to the GPS side via the HPF 40, and the other is outputted to the CDMA side via the LPF 41. That is, the local frequency used in the GPS receiving unit 4 is a 1.4 GHz band and corresponds to the frequency f2. Therefore, the fundamental wave f1 is filtered through the HPF 40, and the frequency f2 is supplied to the GPS receiver 4.
[0032]
As for the frequency f3, since the original generation level in the buffer circuit 38 is lower than the signal component of the frequency f2, it may be left as long as it does not cause spurious interference. If the influence cannot be ignored, the HPF 40 may be replaced with the BPF, and both signal components of the frequencies f1 and f3 may be filtered.
[0033]
The local frequency used on the CDMA side is the 700 MHz band and corresponds to the frequency f1. Therefore, the harmonics f2, f3,... More than twice are filtered through the LPF 41, so that only the frequency f1 is supplied to the CDMA receiver 25 and transmitter 26.
[0034]
FIG. 3 shows a detailed configuration of the buffer circuit 38. The buffer circuit 38 of the present embodiment is configured to perform a circuit operation that is more suitable for the operation described in FIG. The buffer circuit 38 is configured around an NPN transistor 42, an LPF type matching circuit 43, and an HPF type matching circuit 44.
[0035]
A coupling capacitor 45 is connected to the base of the transistor 42. A series circuit of a resistor (collector resistor) 46 and a coil 47 is connected between the power supply VCC and the collector, and a resistor 48 is connected between the common connection point and the base. A capacitor 49 is connected between the common connection point and the ground. The emitter of the transistor 42 is connected to the ground.
[0036]
Further, a series circuit of a coil 50 and capacitors 51 and 52 is connected between the common connection point and the output terminal of the buffer circuit 38, and the common connection point between the capacitor 51 and the capacitor 52 and the ground. A coil 53 is connected between them.
[0037]
In the above description, the coil 47, the capacitor 49, and the coil 50 constitute an LPF type matching circuit 43, and the capacitors 51, 52 and the coil 53 constitute an HPF type matching circuit 44. The signal output level of the VCO 37c constituting the PLL oscillation circuit 37 is set so that the transistor 42 operates in a non-linear region.
[0038]
The T-type matching circuit 43 is adjusted so as to match the frequency f2, and the cutoff frequency is adjusted so that it also acts as an LPF that filters higher harmonics of the frequency f3 or higher. Yes. The T-type matching circuit 44 is adjusted so as to match the frequency f1, and the HPF is adjusted so that the cutoff frequency is lower than f2.
[0039]
The coil 50 in the matching circuit 43 and the capacitor 52 in the matching circuit 44 are designed to match impedances, and the cutoff frequencies of the LPF and HPF do not match the above-mentioned predetermined setting conditions. What is necessary is just to connect when necessary for performing, and it is not necessarily a required element.
[0040]
For comparison, FIG. 4 shows a buffer circuit configured for the purpose of using a single frequency signal (f1) output from a PLL oscillation circuit as in the prior art, as in the present embodiment. A configuration example is shown in the case where it is assumed that the two systems use different frequency signals (f1, f2) as they are.
[0041]
In the buffer circuit 100 in FIG. 4, the transistor 42, the capacitor 45, the resistor 46, and the coil 47 a are connected similarly to the buffer circuit 38. Further, between the collector of the transistor 42 and the output terminal of the buffer circuit 100, matching circuits 101 and 102 each composed of three π-type elements and an LPF 103 are connected. Matching circuits 101 and 102 are circuits for impedance matching for signals of frequencies f1 and f2, respectively, and LPF 103 has a filter characteristic set so as to filter higher harmonic components of frequency f3 or higher.
[0042]
In the buffer circuit 100 configured in this way, the number of elements increases, and the matching conditions of the matching circuits 101 and 102 interfere with each other, and the matching between the two cannot always be achieved optimally.
[0043]
On the other hand, in the buffer circuit 38 of the present embodiment, the harmonic component having the frequency f3 or higher is filtered in the matching circuit 43 in the preceding stage, and matching is performed for the higher frequency f2, and the HPF in the matching circuit 44 in the subsequent stage. Matching is made for the lower frequency f1 by a circuit of the type. Accordingly, the matching circuit 44 at the subsequent stage hardly affects the signal component of the frequency f2, and can optimally match the frequency f1 and f2.
[0044]
The coil 47a is a choke coil (having sufficiently high impedance with respect to the frequencies f1 and f2) necessary for basic buffering operation. In the buffer circuit 38 of this embodiment, the coil 47 is an LPF type. This is a component of the matching circuit 43. In this respect, the required number of elements is reduced as compared with the buffer circuit 100. In addition, the buffer circuit 38 employs a configuration in which the functions of the filter circuit and the matching circuit are shared as described above. As a result, in the buffer circuit 100, the number of elements after the transistor 42 is 10 elements including the coil 47, whereas the buffer circuit 38 is composed of 6 elements, and the total of 4 elements is reduced.
[0045]
As described above, according to the present embodiment, in the mobile phone 1, when the buffer circuit 38 buffers the oscillation signal output from the PLL oscillation circuit 37, the harmonic having the fundamental frequency of the oscillation signal frequency f1. The components f2, f3,... Are also generated and output simultaneously, and the output signals are filtered by the HPF 40 and the LPF 41, respectively, so that the necessary frequency signals are supplied to the GPS receiver 4 and the CDMA transceiver 5 Configured.
[0046]
Therefore, the harmonic components generated as a by-product by the combination of the PLL oscillation circuit 37 and the buffer circuit 38 are appropriately discriminated by the HPF 40 and the LPF 41, so that a complicated circuit is not required. Even when different communication systems such as the GPS receiving unit 4 and the CDMA transmitting / receiving unit 5 are mounted on the mobile phone 1, a single PLL oscillation circuit 37 is shared and a necessary frequency signal is supplied to each of them with a simple configuration. Therefore, the apparatus can be configured at a low cost.
[0047]
Further, according to the present embodiment, the buffer circuit 38 uses the matching circuit 43 as an LPF type to block harmonic components more than three times the fundamental wave f1 and to perform impedance matching with the second harmonic f2. The matching circuit 44 is of the HPF type, and impedance matching is performed with respect to the fundamental wave f1.
[0048]
That is, the buffer circuit 38 sets the output level of the signals of the two frequencies f1 and f2 used by the GPS receiver 4 and the CDMA transceiver 5 to three or more harmonic components (f3, f4, f5,...). Therefore, the frequency discrimination in the HPF 40 and the LPF 41 arranged in the subsequent stage can be performed more easily. That is, the cutoff characteristics of these filter circuits can be set with a margin.
[0049]
In the matching circuits 43 and 44, the matching conditions hardly interfere with each other, and the matching can be optimally performed for both the frequencies f1 and f2. In addition to providing the matching circuits 43 and 44 with a function as a filter circuit, the coil 47 necessary for the buffering operation is shared as a component of the matching circuit 43, so that the buffer circuit 38 is replaced with the buffer circuit 100. The number of elements can be reduced as compared with the above.
[0050]
The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following modifications or expansions are possible.
Instead of the distributor 39, a switch for selectively distributing the output signal of the buffer circuit 38 to either the GPS side or the CDMA side may be arranged.
In the case where the signal of the frequency f2 does not have a great influence on the CDMA transmission unit 26 side, the LPF 41 may be arranged on the CDMA reception unit 25 side after the distributor 42.
If there is no problem in communication characteristics or a problem that the circuit scale becomes large, the buffer circuit 100 may be used instead of the buffer circuit 38.
The oscillation circuit is not limited to the PLL oscillation circuit 37, and an oscillation circuit having another configuration may be used.
The present invention is not limited to the mobile phone 1 in which the GPS receiver 4 and the CDMA transceiver 5 are mounted, but can be applied to a communication device in which a plurality of communication systems (or three or more) that require different frequency signals are mounted. it can.
[Brief description of the drawings]
FIG. 1 shows an embodiment in which the present invention is applied to a mobile phone configured to be able to use a position identification system, and the mobile phone mainly has a GPS receiver and a CDMA transmitter / receiver. Functional block diagram showing
FIG. 2 is a functional block diagram for explaining the operation of the present invention and mainly showing a frequency signal supply system;
FIG. 3 is a diagram showing a detailed configuration of a buffer circuit;
FIG. 4 is a diagram showing a configuration example when it is assumed that a buffer circuit having a conventional configuration is directly applied to the configuration of the present embodiment for comparison.
FIG. 5 is a diagram schematically showing a functional block and a peripheral configuration of a mobile phone
[Explanation of symbols]
1 is a mobile phone (communication device), 4 is a GPS receiver (GPS signal receiving system), 5 is a CDMA transceiver unit (wireless telephone system), 37 is a PLL oscillation circuit, 38 is a buffer circuit, 40 is a high-pass filter (filter) Circuit), 41 is a low-pass filter (filter circuit), 42 is a transistor, 43 is a low-pass filter matching circuit, 44 is a high-pass filter matching circuit, 45 is a coupling capacitor, 46 is a resistor (collector resistance), 47 is a coil, Reference numeral 49 denotes a capacitor.

Claims (4)

An oscillation circuit;
A buffer configured to simultaneously generate and output a signal that becomes a harmonic component when the oscillation signal output from the oscillation circuit is buffered and output when the frequency of the oscillation signal is a fundamental wave. Circuit,
A plurality of filter circuits for selectively outputting any of a plurality of frequency signals output from the buffer circuit;
A communication apparatus comprising: a plurality of different communication systems that operate simultaneously based on a plurality of frequency signals output from the plurality of filter circuits. The buffer circuit is configured to output an output level of a plurality of frequency signals used in the plurality of communication systems relatively higher than output levels of other frequency signals. The communication device according to claim 1. The communication apparatus according to claim 1, wherein one of the plurality of communication systems is a radiotelephone system, and the other is a GPS signal receiving system. If the frequency of the signal used for the radio telephone system is the fundamental wave f1, and the frequency of the signal used for the GPS signal reception system is the second harmonic f2 of the fundamental wave f1,
The buffer circuit is
A transistor whose oscillation signal is input to the base;
A collector resistor and a coil connected in series between a power source and the collector of the transistor;
The collector resistor and a capacitor connected between the common connection point of the coil and the ground are configured to block a harmonic component more than three times the fundamental wave f1 and to the second harmonic f2. A low-pass filter type matching circuit configured to perform impedance matching,
4. A high-pass filter type matching circuit, which is connected to a subsequent stage of the low-pass filter type matching circuit and is configured to perform impedance matching with respect to the fundamental wave f1. Communication device.

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