JP2007166534A - Receiving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving circuit for obtaining stable reception characteristics against environmental change due to the change of use configurations. <P>SOLUTION: A local signal whose frequency is the same as reception frequency is oscillated from a local oscillator 11 of a direct conversion receiver, and the local signal is output through a high frequency switch 13, an impedance equalizer 8, a high frequency switch 4, and a directional coupler 3 to an antenna 1. The reflection quantity of a reflected wave from the antenna 1 is measured by a reflection quantity detector 7, and the impedance of an impedance matching circuit 2 is adjusted to a direction where reflection is reduced based on the measurement result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a receiving circuit employing a direct conversion method.

  A direct conversion receiver is known as a receiver suitable for miniaturization, weight reduction, and cost reduction. In a direct conversion receiver, the high-frequency signal received by the antenna is multiplied by a local oscillation signal (local signal) of the same frequency as the high-frequency signal, and the received high-frequency signal is directly converted to an intermediate frequency without conversion. It converts into a baseband signal (for example, refer patent document 1).

  In general, impedance matching between an antenna and a receiving circuit in a receiver is performed by receiving a radio wave transmitted from a transmitter by an antenna, converting a high-frequency signal into a baseband signal, and demodulating the received signal. The measurement is performed by measuring the intensity, generating an impedance control signal based on the measurement result, and adjusting the variable impedance in the direction in which the received electric field strength increases with the generated control signal (see, for example, Patent Document 2). .

  A circuit for adjusting the transmission impedance between the transmission power amplifier circuit and the antenna is described in, for example, Patent Document 3 or Patent Document 4.

JP 2004-193724 A JP-A-7-111470 Japanese Patent Laid-Open No. 10-341117 JP 2001-16044 A

  By the way, recent portable terminals have a videophone function, a web browsing function, a mail transmission / reception function, etc. in addition to a voice call function. In each use situation, the relative positional relationship between the human body (hand, head, etc.) and the mobile terminal is quite different (for example, the ear is close to the mobile terminal during a call, but the finger of the hand is an operation key when composing an email. Etc.). Therefore, the influence of the human body on the antenna characteristics of the mobile terminal varies depending on the usage status of the mobile terminal.

  Even when the normal telephone function of the portable terminal is used, the impedance of the antenna changes variously. For example, the portable terminal is in a standby state that is an ideal state as an antenna on a charging stand on a desk, and is in a state of touching a human head during a call. In addition, the effects from the human body are too great to be ignored when they are stored in a pocket of clothes when being carried. In this way, the external situation of the antenna element changes, and the impedance of the antenna itself to the receiving circuit varies.

  Due to such impedance variation, mismatch between the antenna and the receiving circuit occurs, and the power received by the antenna cannot be sufficiently transmitted to the receiving circuit side, which causes deterioration of reception sensitivity.

  However, in the technique described in Patent Document 1, for example, the timing for performing the reception impedance matching is fixed (for example, because it is performed only once at the beginning of reception). It is difficult to perform fine-tuned adaptive impedance control that follows changes in antenna impedance from time to time.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a receiving circuit capable of obtaining a stable receiving characteristic with respect to an environmental change due to a change in usage pattern or the like.

  The present invention firstly outputs an antenna unit having an antenna element for receiving a high frequency signal, a high frequency amplifier circuit for amplifying the high frequency signal received by the antenna unit, and a local oscillation signal having the same frequency as the high frequency signal. A local oscillator; a frequency converter that performs frequency conversion on the amplified high-frequency signal using the local oscillation signal; a connection unit that selectively connects the local oscillator and the frequency converter or the antenna unit; A reflection amount detector for measuring a reflection amount generated by reflecting the local oscillation signal output from the local oscillator to the antenna portion through the connection portion and reflected by the antenna portion; and the reflection amount detector An impedance matching control unit that controls impedance matching between the antenna unit and the high-frequency amplifier circuit based on the amount of reflection measured by In which signal circuit is provided.

  With this configuration, the impedance at the reception frequency can be measured at an arbitrary timing by measuring the reflection amount of the reflection generated in the antenna unit using a local oscillation signal having a frequency that matches the reception signal, for example, as in the direct conversion method. It is possible to grasp and respond to fluctuations. Accordingly, since it is possible to cope with a change in impedance caused by an environmental change due to a change in usage pattern or the like, a stable reception characteristic can be obtained.

  A second aspect of the present invention is the receiving circuit according to the first aspect, wherein the impedance matching control unit includes a matching circuit provided between the antenna unit and the high-frequency amplifier circuit, and the reflection amount detection. And a first control circuit for controlling the matching circuit based on the amount of reflection measured by the instrument.

  With this configuration, for example, by adjusting the matching circuit stepwise or continuously so as to reduce the amount of reflection, the impedance matching between the antenna unit and the high-frequency amplifier circuit can be optimally maintained.

  Third, the receiving circuit according to the first or second aspect, wherein the antenna unit includes a plurality of antenna elements, and the impedance matching control unit includes the plurality of antenna elements. An antenna element selector that selects at least one and connects to the high-frequency amplifier circuit; and a second control circuit that controls the antenna element selector based on the reflection amount measured by the reflection amount detector. .

  With this configuration, by selecting an antenna element based on the amount of reflection, it is possible to optimally maintain impedance matching between the antenna unit and the high-frequency amplifier circuit.

  Fourthly, the present invention provides the receiving circuit according to the third aspect, wherein the second control circuit controls the antenna element selector, and the reflection measured for each of the plurality of antenna elements. Select the antenna element with the least amount.

  With this configuration, since the antenna element with the least amount of reflection is selected from each antenna element, the impedance matching between the antenna unit and the high-frequency amplifier circuit can be easily kept optimal.

  Fifth, the present invention provides the reception circuit according to any one of the first to fourth aspects, wherein the connection unit selectively connects the local oscillator and the frequency converter or the antenna unit. A first switch that selectively connects the antenna unit, the high-frequency amplifier circuit or the first switch, and the antenna unit and the second switch. And a directional coupler that outputs a signal from the second switch toward the antenna unit and outputs a signal from the antenna to the reflection amount detector.

  With this configuration, it is possible to send a local oscillation signal output to the antenna unit and a reflected wave from the antenna unit toward the reflection amount detector using a switch and a directional coupler.

  6thly, it is a receiver circuit of the said 5th, Comprising: The said connection part further has an impedance equalizer inserted between the said 1st switch and the said 2nd switch.

  With this configuration, it is possible to make adjustments such as making the impedance of the path through which the signal from the local oscillator is input viewed from the antenna unit equal to the impedance of the path through which the reception signal including the high-frequency amplifier circuit is output. .

  Seventhly, the present invention provides the receiving circuit according to any one of the first to fourth aspects, wherein the connection unit selectively connects the local oscillator and the frequency converter or the antenna unit. A first switch that outputs a signal from the antenna unit to the high-frequency amplifier circuit, and outputs a signal from the first switch to the antenna unit, the high-frequency amplifier circuit, and the frequency converter Or a second switch for selectively connecting the reflection amount detector.

  With this configuration, when detecting the reflection amount, the reflected wave from the antenna unit amplified by the high-frequency amplifier circuit can be used, so that the detection efficiency of the reflection amount can be improved.

  Eighthly, the present invention provides the reception circuit according to any one of the first to seventh aspects, wherein the impedance matching control unit is a time slot period excluding a reception time slot and a transmission time slot in a time division multiplexing system. The impedance matching between the antenna unit and the high-frequency amplifier circuit is controlled.

  With this configuration, in a receiving circuit that performs time division multiplexing communication, impedance matching control is performed outside the period during which the own device communicates. Therefore, control for impedance matching can be performed even during communication. Therefore, it is possible to follow fluctuations in impedance matching between the antenna and the receiving circuit.

  The ninth aspect of the present invention is the receiving circuit according to any one of the first to eighth aspects, wherein the antenna unit has a telescopic antenna element and is measured by the reflection amount detector. And a notification section for notifying the fact that the expansion / contraction amount of the telescopic antenna element is inappropriate based on the reflected amount.

  With this configuration, when a telescopic antenna element such as a whip antenna is used, the fact is notified to the user when the position of the antenna is not appropriate. It is possible to prevent a decrease in reception sensitivity caused by the above.

  Tenthly, the present invention provides a communication apparatus including the receiving circuit according to any one of the first to ninth aspects.

  ADVANTAGE OF THE INVENTION According to this invention, the receiving circuit which can acquire the stable receiving characteristic with respect to the environmental change by the change of a usage pattern, etc. can be provided.

(First embodiment)
FIG. 1 is a circuit diagram showing a main configuration of an example of a receiving circuit according to the first embodiment of the present invention. In the first embodiment, a direct conversion receiver is shown as an example of a receiving circuit.

  Here, it is assumed that the direct conversion receiver of FIG. 1 is mounted on a multiband portable communication terminal that conforms to the PDC method or the GSM method and supports the TDMA communication method. In FIG. 1, a transmission circuit is omitted.

  As shown in FIG. 1, the direct conversion receiver of this embodiment includes an antenna circuit 1 having an antenna element that receives a high-frequency signal, and an impedance between the antenna circuit 1 and the high-frequency amplifier 5 (as viewed from the antenna circuit 1). Impedance matching circuit 2 for adjusting reception impedance), directional coupler 3, high-frequency switch 4 for selecting either the reception path or the local signal injection path, and a high-frequency amplifier circuit (hereinafter referred to as a high-frequency amplifier). ) 5, a control circuit 6 that dynamically adjusts the impedance of the impedance matching circuit 2, and a reflection amount detector that measures the reflection amount of the reflected wave from the antenna circuit 1 that is output from the terminal P <b> 3 of the directional coupler 3. 7, impedance equalizer 8, mixers 9 a and 9 b, 90 ° phase shifter 10, 2 of the local signal A local oscillator 11 that generates a frequency, a frequency divider 12 that divides a frequency twice that of a local signal by 2, a high-frequency switch 13 that switches a supply destination of a local signal obtained via the frequency divider 12, and a low-pass filter 14a, 14b. As described above, the frequency of the local signal is generated by the local oscillator 11 and the frequency divider 12. In actual design, the output of the local oscillator 11 is not used as it is as the frequency of the local signal, but it is oscillated 2 to 4 times the reception frequency in consideration of wraparound, C / N reservation, etc. It is often divided immediately before. This configuration is also adopted in the present embodiment.

  In the present embodiment, the control circuit 6 and the impedance matching circuit 2 that operate as an example of the first control circuit operate as an example of an impedance matching control unit. The mixers 9a and 9b and the 90 ° phase shifter 10 operate as an example of a frequency conversion unit. The high frequency switch 13 operates as an example of the first switch. The high frequency switch 4 operates as an example of a second switch.

  Here, if the frequency of a high-frequency signal (RF signal) received by the antenna circuit 1 is Fr, and the frequency of the local signal output from the local oscillator 11 is f, then f = 2Fr. At the time of reception, the mixer 9a, 9b multiplies (mixes) the received high-frequency signal with a local signal having the same frequency, thereby directly converting the high-frequency signal into a baseband signal.

  In the circuit of FIG. 1, a path for injecting a local signal toward the antenna circuit 1 (local signal injection path) can be appropriately formed, and reflection of a reflected wave from the antenna circuit 1 is possible. The reflection amount detector 7 detects the reflection amount such as the coefficient, the reflected power coefficient, and the VSWR, and the control circuit 6 estimates the impedance matching state between the antenna circuit 1 and the high-frequency amplifier 5 from the detection result, and the antenna circuit The impedance of the impedance matching circuit 2 is adjusted in a direction to reduce reflection from 1.

  The local signal injection path is a high-frequency switch that selectively connects the divider 12, the local oscillator 11, and the 90 ° shifter 10 or the impedance equalizer 8 on the antenna circuit 1 side to switch the supply destination of the local signal. 13, the impedance equalizer 8, the directional coupler 3 on the antenna circuit 1 side, the high-frequency switch 4 that selectively switches between the high-frequency amplifier circuit or the high-frequency switch 13, the directional coupler 3, and the matching circuit 2 It is comprised. When injecting a local signal toward the antenna circuit 1, the high frequency switch 14 is switched to the terminal S3 side, and the high frequency switch 4 is switched to the terminal S2 side.

  The impedance matching circuit 2 includes a variable capacitance and an inductance realized by a variable capacitance diode or the like, and can change the reception impedance continuously or stepwise by changing the capacitance value.

  The control circuit 6 has, for example, a table in which the amount of reflection from the antenna circuit 1 is associated with the reception impedance. Based on this table, the impedance matching circuit 2 is arranged in a direction to reduce the amount of reflection. Adjust continuously or in steps.

  The impedance equalizer 8 is inserted for the purpose of making the impedance viewed from the antenna circuit 1 equal to the impedance of the normal reception path when the local signal injection path is formed. That is, the input impedance of the impedance equalizer 8 (impedance seen from the antenna circuit 1) is set to be the same as the input impedance of the high-frequency amplifier 5.

  FIG. 2 is a diagram for explaining the function of the directional coupler. As shown in FIG. 2, the directional coupler 2 has four terminals P1 to P4. Here, the terminal P4 is terminated. The terminals P1 and P2 are coupled in both directions, and the terminals P2 and P4 are coupled, but the terminals P2 and P3 are not coupled. That is, when the high-frequency signal Q1 is input from the terminal P2, this Q1 is output to the terminal P1 as it is, and the output P2 demultiplexed from Q1 is obtained at the terminal P4, but the terminal P3 has No output can be obtained.

  Similarly, the terminal P1 and the terminal P3 are coupled, but the terminal P1 and the terminal P4 are not coupled. That is, when the high frequency signal R1 is input from the terminal P1, this R1 is output as it is to the terminal P2, and an output R2 demultiplexed from R1 is obtained at the terminal P3. No output can be obtained.

  Therefore, when adjusting the reception impedance, the local signal injected into the terminal P2 of the directional coupler via the terminal S2 of the high frequency switch 4 is output as it is from the terminal P1, and is then transmitted through the impedance matching circuit 2 to the antenna circuit 1. To reach. The reflected wave generated in the antenna circuit 1 is input to the terminal P1 of the directional coupler 3 via the impedance matching circuit 2, and the demultiplexed component is output from the terminal P3. Guided to vessel 7. In this way, the reflection amount of the antenna circuit 1 can be measured by the reflection amount detector 7.

  Next, returning to FIG. 1, a procedure for optimizing the impedance between the antenna circuit 1 and the high-frequency amplifier 5 (corresponding to the entrance of the receiving circuit) will be specifically described.

  First, a local signal (frequency Fr signal) output from the local oscillator 11 is sent to the antenna circuit 1 via the high frequency switch 13, the impedance equalizer 8, the high frequency switch 4, the directional coupler 3, and the impedance matching circuit 2. inject.

  Next, the reflected wave from the antenna circuit 1 is guided to the reflection amount detector (DET) 7 via the directional coupler 3, and the reflection amount detector 7 reflects the reflection amount (reflection coefficient, reflection power coefficient, VSWR). Etc.).

  For example, the control circuit 6 adjusts the impedance matching circuit 2 so that the actually measured reflection amount is equal to or less than a preset reference value or is minimized.

  The procedure for adjusting the reception impedance is summarized as shown in FIG. FIG. 8 is a flowchart showing a reception impedance adjustment procedure in the reception circuit according to the first embodiment of the present invention.

  First, a local channel (that is, a local oscillation frequency) is designated by a frequency selection signal (step S100), the high frequency switch 13 is switched to the terminal S3 side, and the high frequency switch 4 is switched to the terminal S2 side (step S101). .

  Then, the local oscillator (local synthesizer) 11 starts oscillating (step S102). As a result, the local signal is injected into the antenna circuit 1 via the local signal injection path, and a reflected wave is generated in the antenna circuit 1.

  The reflected wave is output from the terminal P3 of the directional coupler 3, and is measured by the reflection amount detector (DET) 7 (step S103). Then, the control circuit 6 compares the measured reflection amount with a predetermined reference value (step 103), and performs the comparison operation so that the measured reflection amount becomes smaller than the reference value (or the reflection amount). The impedance matching circuit 2 is adjusted so that the amount becomes the minimum value (step S105).

  Then, the control circuit 6 stores the control parameters of the impedance matching circuit 2 in a built-in memory (not shown) (step S106).

  Next, timing for adjusting the impedance of the impedance matching circuit 2 will be described.

  FIG. 3 is a timing chart showing timing for performing impedance adjustment in the receiving circuit according to the first embodiment of the present invention. FIG. 3A shows the impedance adjustment timing in the idle mode (intermittent reception mode), and FIG. 3B shows the impedance adjustment timing in communication (dedicated mode).

  The direct conversion receiver of this embodiment is mounted on a TDMA (Time Division Multiple Access) type mobile communication terminal. A TDMA transmission / reception frame is composed of a plurality of time slots, one of which is assigned as a transmission period or a reception period, and transmission / reception is performed in a time division manner.

  Transmission / reception is switched by an operation mode control signal. The transmitting antenna and the receiving antenna are different, and the antenna to be used is switched according to the operation mode. The antenna is switched by the antenna switching control signal.

  Here, since the time slot period that is not used for transmission or reception is an empty period (that is, a period that is not used for transmission / reception), in this embodiment, the reception impedance is adjusted (that is, this period is used) , Injection of a local signal into the antenna circuit 1, measurement of the amount of reflection from the antenna circuit 1, and adjustment of the impedance matching circuit 2). As a result, the reception impedance can be controlled in real time during idle mode or during a call, and real-time adaptive control is performed following the impedance of the antenna that changes momentarily according to the approaching state of the human body. It becomes possible. Therefore, it is possible to always keep the reception impedance in an optimum state.

  The idle mode in the TDMA communication system is a mode for allowing the mobile communication terminal to intermittently receive control signals from the base station and grasping in which base station area the mobile station is located.

  In the idle mode, a vacant reception slot period for each frame is set as a reception impedance adjustment period. That is, in FIG. 3A, time slot Ts1 (time t2 to t3) is a period for receiving a control signal from the base station. The time slot Ts6 (time t7 to t8) is a period for adjusting the reception impedance.

  Further, when a call is in progress, as shown on the lower side of FIG. 3, there is an empty period other than the reception period (time slot Ts1: time t2 to t3) and the transmission period (time slot Ts4: time t5 to t6). A time slot period (here, a period of time slot Ts6 (time t7 to t8)) is set as a reception impedance adjustment period.

  According to the first embodiment of the present invention, the local oscillator 11 (and the frequency divider 12) in the direct conversion system is used as a signal generation source having the same frequency as the reception frequency. 11 is injected toward the antenna circuit 1 and the amount of reflection from the antenna circuit 1 is measured, whereby the impedance matching state between the antenna circuit 1 and the high-frequency amplifier 5 in the reception frequency band is determined. To check. Therefore, the impedance between the antenna circuit 1 and the high-frequency amplifier 5 can be set more freely without performing processing such as actually receiving a signal, demodulating the received signal, and detecting electric field strength, SNR, and the like. It becomes possible to adjust.

  Therefore, the reception impedance can be adjusted even during the idle period (standby period). In addition, by adjusting the reception impedance during the empty time slot period in the TDMA frame, real-time adaptive control can be performed following the impedance of the antenna that changes momentarily according to the approaching state of the human body. It becomes. Therefore, the reception impedance can always be kept in an optimum state.

(Second Embodiment)
FIG. 4 is a circuit diagram showing a main configuration of an example of a receiving circuit according to the second embodiment of the present invention. 4, parts that are the same as those in FIG. 1 are given the same reference numerals.

  As shown in FIG. 4, the direct conversion receiver of this embodiment is provided with a plurality of receiving antennas A1 to An as antenna units, and the connection (terminal) of the high-frequency switch 15 that operates as an example of an antenna element selection unit. W1 to Wn) are dynamically switched by an antenna selection signal (CS) from the control circuit 6 that operates as an example of the second control circuit, thereby selecting an antenna having a minimum reception impedance. Other configurations are the same as those of the direct conversion receiver of FIG. The antenna element selector may be configured to select at least one of the receiving antennas A1 to An.

  The plurality of antennas A1 to An are optimized in characteristics such as antenna positions so as to be adapted to each usage situation in consideration of the influence of the human body for each usage situation of the mobile terminal. An antenna having the smallest reflection amount is selected from these antennas. The antenna selected in this way, that is, an antenna suitable for the usage status of the mobile terminal at that time.

  The procedure for antenna selection will be described with reference to FIG. FIG. 9 is a flowchart showing the procedure for adjusting the reception impedance in the reception circuit according to the second embodiment of the present invention.

  First, a local channel (that is, a local oscillation frequency) is designated (step S200). Next, the high frequency switch 13 is switched to the terminal S3 side, and the high frequency switch 4 is switched to the terminal S2 side (step 201). Thereby, a path for local signal injection is formed.

  Then, the local oscillator (local synthesizer) 11 starts oscillating (step S202). Further, the high frequency switch 15 as the antenna selector is switched (step S203). Then, the local signal is injected into the antenna 1 via the local signal injection path. Thereby, a reflected wave is generated in the antenna 1.

  The reflected wave is output from the terminal P3 of the directional coupler 3, and is measured by the reflection amount detector (DET) 7 (step S204). Then, the reflection amount for the currently selected antenna is stored in a memory (not shown). And the said operation | movement is implemented about all the antennas (step S206, S207, S204, S205).

  Then, the smallest one of the repeated reflection amounts is selected, and the high frequency switch 15 is switched (step S208).

  According to the second embodiment of the present invention, since the reception impedance is switched stepwise by switching the antenna, the impedance adjustment over a wide range can be performed quickly.

(Third embodiment)
FIG. 5 is a circuit diagram showing a main configuration of an example of a receiving circuit according to the third embodiment of the present invention. In FIG. 5, the same reference numerals are given to portions overlapping those in FIGS. 1 and 4.

  As shown in FIG. 5, the control circuit 6 selects the antenna by switching the high frequency switch 15 based on the actual measurement result of the reflection amount, and then adjusts the impedance of the impedance matching circuit 2. . At this time, the control circuit 6 operates as an example of the first control circuit and the second control circuit.

  In the direct conversion receiver of FIG. 5, as in the second embodiment, the k-th antenna is selected by the high frequency switch 15 to inject a local signal, and the reflected wave is transmitted to the directional coupler 3 and the reflection amount detector ( DET) Pick up at 7. Then, the amount of reflection is stored, and then the antenna element is set to k + 1, k + 2,..., And the same operation is repeated. At this time, the impedance of the impedance matching unit 2 is fixed to a predetermined reference state.

  Then, the smallest one is selected from the repeated reflection amounts, and the high frequency switch 15 is switched. After that, a local signal is injected again into the selected antenna, and the impedance of the impedance matching circuit 2 is adjusted by the control circuit 6 so that the reflection amount is equal to or less than a preset value or is minimized. To do.

  According to the third embodiment of the present invention, the impedance is quickly adjusted over a wide range by switching the antenna (rough adjustment of the impedance), and then the impedance matching unit 2 performs fine adjustment of the impedance. Make adjustments. Therefore, the reception impedance can be adjusted with higher accuracy.

(Fourth embodiment)
FIG. 6 is a circuit diagram showing a main configuration of an example of a receiving circuit according to the fourth embodiment of the present invention. In FIG. 6, the same reference numerals are assigned to portions overlapping those in FIG. 1.

  The main operation of the direct conversion receiver of FIG. 6 is the same as that of the receiver of FIG. However, in the case of FIG. 6, a circulator 30 is used instead of the directional coupler (reference numeral 3 in FIG. 1). Further, the high frequency switch 4 is provided in the subsequent stage of the high frequency amplifier 5.

  In the direct conversion receiver of FIG. 6, the high-frequency amplifier 5 is always visible when viewed from the antenna 1 even when the amount of reflection is measured. Therefore, in FIG. Reference numeral 8) of 1 is not necessary.

  In the direct conversion receiver of FIG. 6, the reflected wave from the antenna is input to the high frequency amplifier 5 via the circulator 30 and amplified, and the amplified reflected wave is detected by the reflection amount via the high frequency switch 4. Since the light is guided to the detector (DET) 7, the pickup efficiency (ie, S / N) in the reflection amount detector 7 is improved.

  FIG. 7 is a diagram for explaining the function of the circulator. As shown in FIG. 7, the circulator 30 has three terminals P5, P6, and P7, and can transmit signals between adjacent terminals. That is, it is possible to transmit the signal Q6 (signal from the terminal P5 to the terminal P6), the signal Q7 (signal from the terminal P6 to the terminal P7), and the signal Q8 (signal from the terminal P7 to the terminal P5).

  According to the fifth embodiment of the present invention, when detecting the amount of reflection, the reflected wave from the antenna unit amplified by the high-frequency amplifier circuit can be used, so that the detection efficiency of the amount of reflection is improved. Can be achieved.

  The configuration of this embodiment is a configuration using the antenna elements A1 to An and the high-frequency switch 15, which is the configuration shown in the second embodiment (FIG. 4) or the third embodiment (FIG. 5). You may apply.

(Fifth embodiment)
In the fifth embodiment of the present invention, it is detected from the measured value of the amount of reflection from the antenna that the retractable whip antenna is in an inappropriate position, and a notification is made to prompt the user to correct the position of the whip antenna. A portable terminal to be described will be described. As a result, the reception process can always be performed in a state where the whip antenna is in the correct position. As a result, it is possible to prevent a decrease in reception sensitivity caused by an inappropriate antenna expansion / contraction position and storage position, and the convenience of the receiver is improved.

  10A and 10B are diagrams for explaining a whip antenna used for a mobile terminal. FIG. 10A is a cross-sectional view showing a main part of the whip antenna, and FIG. It is sectional drawing which shows the state correctly accommodated in the housing | casing, FIG.10 (c) is sectional drawing which shows the state (correct expansion | extension state) where the whip antenna was extended from the housing | casing of the portable terminal.

  As shown in FIG. 10A, the whip antenna (AN) includes an element for storage (helical antenna part) 17 and an element for extension (bar-shaped antenna part) 18. At the time of storage, an upper storage antenna (helical antenna unit) 17 is used. At the time of extension, the lower bar antenna portion 18 is used.

  The antenna for storage (helical antenna part) 17 and the element for extension / contraction (bar-shaped antenna part) 18 are insulated, and each antenna part has an independent feeding part. If the power feeding portion of each antenna element (17, 18) is stored or extended and fixed by the user in contact with the stopper 20 (case side connection portion), the antenna 1 and the high frequency amplifier 5 (receiving circuit) The connection of is a normal connection state.

  In FIG. 10B, the whip antenna (AN) is correctly stored in the casing 19 of the mobile terminal. The whip antenna (AN) is locked by a stopper 20. In this state, the storage element 17 serves as a feeding unit for the whip antenna (AN).

  FIG. 10C shows a state where the whip antenna (AN) is correctly extended from the casing 19 of the mobile terminal. The whip antenna (AN) is locked by a stopper 20. In this state, the extension element 18 serves as a feeding unit for the whip antenna (AN).

  FIG. 11 is a diagram for explaining the operation of the receiving circuit according to the fifth embodiment of the present invention.

  In the case of FIG. 11A, the whip antenna is in the middle between the extended state and the retracted state, and therefore the high-frequency amplifier (receiving circuit) 5 is not connected to the antenna (AN) at all and functions as an antenna. It is a state that does not.

  In the direct conversion receiver having the configuration of FIG. 4, when a local signal is injected in the state of FIG. 11A, the amount of reflection from the antennas (A1 to An) becomes maximum, and the detection of the reflection amount detector (DET) 7 occurs. The quantity indicates the maximum value (abnormal value). Therefore, it can be detected that the antenna is in an inappropriate position.

  In this case, the control circuit 6 displays a message prompting the user to correctly store or extend the antenna element on the display unit 21 of the portable terminal. Thereby, it is possible to always perform the reception process in a state where the antenna is in the correct position. In addition, as a means to alert | report to a user, you may alert | report by audio | voice output etc. other than the display part 21. FIG.

  FIG. 12 is a circuit diagram showing a main configuration of an example of a receiving circuit according to the fifth embodiment of the present invention. In FIG. 12, parts that are the same as those in the previous drawings are given the same reference numerals.

  The basic configuration of the direct conversion receiver of FIG. 12 is the same as that of the receiver of FIGS. However, in the case of FIG. 12, a telescopic whip antenna (AN) is used, and the control circuit 6 performs impedance adjustment of the impedance matching circuit 2 or, instead of the impedance adjustment, The display of the display unit 21 is also controlled. In FIG. 12, reference numeral 22 is a low-pass filter for transmission signals, reference numeral 23 is a transmission amplifier, and reference numeral 40 is a duplexer.

  According to the fifth embodiment of the present invention, it is possible to notify the user in advance that the position of the whip antenna is inappropriate and correct the whip antenna to an appropriate position. Therefore, reception can always be started under an antenna state suitable for reception.

  As described above, according to the embodiment of the present invention, in the receiving circuit adopting the direct conversion method, the reception frequency is equal to the local frequency, and the local oscillation output is injected into the antenna circuit. The amount of reflection from the circuit side is measured, and impedance matching between the antenna and the high-frequency amplifier circuit (receiver circuit) is optimized according to the frequency to be received, thereby improving the reception characteristics.

  The receiving circuit of the present invention has an effect capable of obtaining a stable receiving characteristic with respect to an environmental change due to a change in usage pattern, etc., and is useful for a receiving circuit of a cellular phone device.

1 is a circuit diagram showing a main configuration of an example of a receiving circuit according to a first embodiment of the present invention; Diagram for explaining the function of a directional coupler FIG. 3 is a timing chart showing timing for impedance adjustment in the receiving circuit according to the first embodiment of the present invention; The circuit diagram which shows the main structures of an example of the receiving circuit which concerns on the 2nd Embodiment of this invention The circuit diagram which shows the main structures of an example of the receiving circuit which concerns on the 3rd Embodiment of this invention The circuit diagram which shows the main structures of an example of the receiving circuit which concerns on the 4th Embodiment of this invention Diagram for explaining the function of the circulator The flowchart which shows the adjustment procedure of the reception impedance in the receiver circuit which concerns on the 1st Embodiment of this invention The flowchart which shows the adjustment procedure of the reception impedance in the receiver circuit which concerns on the 2nd Embodiment of this invention The figure for demonstrating the whip antenna used for a portable terminal The figure for demonstrating operation | movement of the receiver circuit in the 5th Embodiment of this invention. The circuit diagram which shows the main structures of an example of the receiving circuit which concerns on the 5th Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Impedance matching circuit 3 Directional coupler 4 High frequency switch 5 High frequency amplifier 6 Control circuit 7 Reflection amount detector 8 Impedance equalizer 9a, 9b Mixer 10 90 degree phase shifter 11 Local oscillator 12 Frequency divider 13 High frequency switch 14 Low pass Filter 15 High-frequency switch 17 Storage element 18 Extension element 19 Housing 20 Stopper 21 Display unit 22 Low-pass filter for transmission signal 23 Power amplifier

Claims (10)

An antenna unit having an antenna element for receiving a high-frequency signal;
A high frequency amplifier circuit for amplifying a high frequency signal received by the antenna unit;
A local oscillator that outputs a local oscillation signal having the same frequency as the high-frequency signal;
A frequency converter that performs frequency conversion on the amplified high-frequency signal using the local oscillation signal;
A connection section for selectively connecting the local oscillator and the frequency conversion section or the antenna section;
A reflection amount detector that measures the amount of reflection of the local oscillation signal output from the local oscillator to the antenna unit via the connection unit and generated by the antenna unit;
A receiving circuit comprising: an impedance matching control unit that controls impedance matching between the antenna unit and the high-frequency amplifier circuit based on a reflection amount measured by the reflection amount detector. The receiving circuit according to claim 1,
The impedance matching control unit is a first control for controlling the matching circuit based on a matching circuit provided between the antenna unit and the high-frequency amplifier circuit and a reflection amount measured by the reflection amount detector. A receiver circuit. The receiving circuit according to claim 1 or 2,
The antenna unit has a plurality of antenna elements,
The impedance matching control unit is configured to select at least one of the plurality of antenna elements and connect to the high-frequency amplifier circuit, and based on the reflection amount measured by the reflection amount detector. And a second control circuit for controlling the antenna element selector. The receiving circuit according to claim 3,
The second control circuit is a receiving circuit that controls the antenna element selection unit to select an antenna element having the least amount of reflection measured for each of the plurality of antenna elements. A receiving circuit according to any one of claims 1 to 4,
The connecting portion is
A first switch for selectively connecting the local oscillator and the frequency converter or the antenna unit;
A second switch for selectively connecting the antenna unit and the high-frequency amplifier circuit or the first switch;
A direction that is provided between the antenna unit and the second switch, outputs a signal from the second switch toward the antenna unit, and outputs a signal from the antenna to the reflection amount detector. A receiving circuit having a sex coupler. The receiving circuit according to claim 5, wherein
The connection unit further includes an impedance equalizer inserted between the first switch and the second switch. A receiving circuit according to any one of claims 1 to 4,
The connecting portion is
A first switch for selectively connecting the local oscillator and the frequency converter or the antenna unit;
A circulator that outputs a signal from the antenna unit to the high-frequency amplifier circuit and outputs a signal from the first switch to the antenna unit;
A receiving circuit comprising: the high-frequency amplifier circuit; and a second switch that selectively connects the frequency converter or the reflection amount detector. A receiving circuit according to any one of claims 1 to 7,
The impedance matching control unit is a receiving circuit that controls impedance matching between the antenna unit and the high-frequency amplifier circuit in a time slot period excluding a reception time slot and a transmission time slot in a time division multiplexing system. A receiving circuit according to any one of claims 1 to 8,
The antenna unit has a telescopic antenna element,
A receiving circuit further comprising an informing unit for informing, when the amount of expansion / contraction of the telescopic antenna element is inappropriate, based on the amount of reflection measured by the reflection amount detector.   A communication apparatus comprising the receiving circuit according to claim 1.

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