GB2238193A - Band-pass filters controlled in dependence on signal frequency - Google Patents

Band-pass filters controlled in dependence on signal frequency Download PDF

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Publication number
GB2238193A
GB2238193A GB9023156A GB9023156A GB2238193A GB 2238193 A GB2238193 A GB 2238193A GB 9023156 A GB9023156 A GB 9023156A GB 9023156 A GB9023156 A GB 9023156A GB 2238193 A GB2238193 A GB 2238193A
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United Kingdom
Prior art keywords
transmitting
frequency
band
receiving
variable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9023156A
Other versions
GB2238193B (en
GB9023156D0 (en
Inventor
Masao Uno
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Murata Manufacturing Co Ltd
Original Assignee
Murata Manufacturing Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Murata Manufacturing Co Ltd filed Critical Murata Manufacturing Co Ltd
Publication of GB9023156D0 publication Critical patent/GB9023156D0/en
Publication of GB2238193A publication Critical patent/GB2238193A/en
Application granted granted Critical
Publication of GB2238193B publication Critical patent/GB2238193B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J3/00—Continuous tuning
    • H03J3/02—Details
    • H03J3/06—Arrangements for obtaining constant bandwidth or gain throughout tuning range or ranges
    • H03J3/08—Arrangements for obtaining constant bandwidth or gain throughout tuning range or ranges by varying a second parameter simultaneously with the tuning, e.g. coupling bandpass filter
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/09—Filters comprising mutual inductance
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/17—Structural details of sub-circuits of frequency selective networks
    • H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
    • H03H7/1775—Parallel LC in shunt or branch path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/403—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
    • H04B1/405—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency with multiple discrete channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/72—Mobile telephones; Cordless telephones, i.e. devices for establishing wireless links to base stations without route selection
    • H04M1/725—Cordless telephones
    • H04M1/72502—Cordless telephones with one base station connected to a single line

Abstract

A transmitting/receiving circuit for a mobile radio communication system includes an antenna 2, for transmitting and receiving a radio wave, to which first and second variable band-pass filters 30, 32 are connected. First filter 30 is used for an input stage of a receiving circuit and second filter 32 is used for an output stage of a transmitting circuit. The receiving and transmitting circuits are provided with PLL synthesizers 8 and 14 respectively. Each filter includes variable capacitance diodes. The variable capacitance diodes of the first filter are controlled by a control voltage from the PLL synthesizer 8 and the variable capacitance diodes of the second filter are controlled by a control voltage from the PLL synthesizer 14. in a second embodiment only one synthesizer is used. <IMAGE>

Description

TITLE OF THE INVENTION Transmitting/Receiving Circuit for Mobile Radio Communication System BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a transmitting/receiving circuit for a mobile radio communication system. More specifically, the present invention relates to a transmitting/receiving circuit which is incorporated in a mobile radio communication apparatus such as a land mobile radio telephone, cordless telephone or the like and used for transmitting and receiving a radio wave through an antenna.
Description of the Prior Art As one example of a mobile radio communication apparatus of a multi-channel access system, US cellular, that is, a land mobile radio telephone which adopts a receiving frequency band of 869-894 MHz and a transmitting frequency band of 824-849 MHz is known.
Examples of conventional transmitting/receiving circuits which can be incorporated in such a land mobile radio telephone are shown in Figs. 4 and 5, respectively.
In a conventional transmitting/receiving circuit shown in Fig. 4, a received signal within the receiving frequency band, which is received by a transmitting/receiving antenna 2, is filtered by a dielectric band-pass filter 4 to be given to a mixer 6.
In the mixer 6, the received signal is mixed with an output of a VCO (voltage-Controlled Oscillator) 10 a frequency of which is controlled by a PLL (Phase-Locked Loop) synthesizer 8 which functions as areceiving frequency controlling means to be converted into an intermediate frequency signal of 45 MHz. The intermediate frequency signal is filtered by an intermediate frequency filter 12 and then detected by a sound detection circuit (not shown).
On the other hand, a sound signal from a sound circuit (not shown) is inputted to a VCO 16 a frequency of which is controlled by a PLL synthesizer 14 which functions as a transmitting frequency controlling means.
Therefore, the output of the VCO 16 becomes a frequencymodulated signal which is modulated by the sound signal.
The frequency-modulated signal is amplified by an amplifier 18 and then transmitted from the transmitting/receiving antenna 2 through a dielectric band-pass filter 20.
A conventional transmitting/receiving circuit shown in Fig. 5 is different from Fig. 4 circuit in that the transmitting/receiving circuit is provided with a single PLL synthesizer 22, a single VCO 24 and an oscillator 25 and that a mixer 26 is added to a circuit for transmitting. In addition, the oscillator 25 may be a fixed frequency oscillator such as a crystal oscillator, and the frequency thereof is set as twice the intermediate frequency, 90 MHz, for example. More specifically, frequency selection data for setting a receiving frequency, for example, 881.5 MHz is applied to the PLL synthesizer 22 which controls the VCO 24 so that an output frequency of the VCO 24 becomes 926.5 MHz, for example. The output of the VCO 24 is inputted to the mixer 26 as well as the mixer 6.On the other hand, the oscillator 25 outputs a frequency-modulated signal which is modulated by the sound signal. Therefore, in the mixer 26, the outputs of the VCO 24 and the oscillator 25 are mixed with each other, and therefore, a frequencymodulated signal a center frequency of which is 836.5 MHz, for example, is outputted from the mixer 26. In the mixer 6, the output of the VCO 24 is mixed with the received signal 881.5 MHz, for example, and therefore, the output of the mixer 6 becomes the intermediate frequency signal of 45 MHz.
In addition, a transmitting/receiving operation of Fig. 5 circuit is similar to that of Fig. 4 circuit.
In the above described conventional transmitting/receiving circuits, as the band-pass filters 4 and 20, dielectric filters having high Q and fixed frequency pass bands are used because the band-pass filters 4 and 20 have to satisfy various requirements as follows: Filter characteristics of the band-pass filters 4 and 20 must have sufficient attenuation characteristics in order to prevent a cross-talk at the outside of the transmitting/receiving frequency bands, levels of the transmitting/receiving signals can not be attenuated largely in order to make clear transmission/reception within the respective frequency bands, and attenuation curves of the respective filters should be sharp at both the inside and outside of the respective frequency bands since pass bands of the respective filters are fixed at 25 MHz and a frequency difference between the transmitting and receiving frequencies is, for example, 45 MHz and thus the frequency distance between adjacent side ends of the respective band-pass filters is very narrow, for example, 20 MHz.
However, a cost of the dielectric filter is very high, and therefore, a cost of the conventional circuit becomes also high since the circuit needs to be provided with at least two dielectric filters for the transmitting circuit and the receiving circuit. In addition, the higher Q, the larger a size of the dielectric filter, and therefore, due to such points, it was impeded a land mobile radio telephone from being cheapened and miniaturized.
SUMMARY OF THE INVENTION Therefore, a principal object of the present invention is to provide a novel transmitting/receiving circuit for a mobile radio communication system.
Another object of the present invention is to provide a transmitting/receiving circuit for a mobile radio communication system capable of being inexpensive and miniaturized.
The other object of the present invention is to provide a transmitting/receiving circuit for a mobile radio communication system, in which variable band-pass filters are used for a transmitting circuit and a receiving circuit, respectively.
A transmitting/receiving circuit in accordance with the present invention comprises: an antenna; transmitting frequency control means for controlling a transmitting frequency; receiving frequency controlling means for controlling a receiving frequency; a first variable bandpass filter for filtering a received signal through the antenna, said first variable band-pass filter having a band varying portion which receives a control signal from the receiving frequency controlling means; and a second variable band-pass filter for filtering a transmitting signal and applying the same to the antenna, said second variable band-pass filter having a band varying portion which receives a control signal from the transmitting frequency controlling means.
A receiving frequency is controlled by the receiving frequency controlling means to be become a vacant frequency within the receiving frequency band and a transmitting frequency is controlled by the transmitting frequency controlling means to be become a vacant frequency within the transmitting frequency band.
At the same time, the control signals are applied to the first and second variable band-pass filters from the receiving frequency controlling means and the transmitting frequency controlling means. Therefore, pass bands of the first and second variable band-pass filters are respectively varied by the band varying portions thereof so that the transmitting signal and the received signal can be respectively transmitted and received at the respective vacant frequencies.
In accordance with the present invention, since the pass bands of the first and second variable band-pass filters can be varied automatically in response to change of the transmitting/receiving frequencies, each of the variable band-pass filters may be a filter having a narrow pass band and a broad attenuation curve.
Therefore, it is not necessary to use a filter having high Q such as a dielectric filter. Therefore, it is possible to make a mobile radio communication apparatus such as a land mobile radio telephone inexpensive and compact.
The objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the embodiments of the present invention when taken in conjunction with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing one embodiment in accordance with the present invention.
Fig. 2 is a circuit diagram showing one example of a variable band-pass filter which can be used in Fig. 1 embodiment.
Fig. 3 is a block diagram showing another embodiment in accordance with the present invention.
Figs. 4 and 5 are block diagrams respectively showing different examples of conventional transmitting/receiving circuits.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a block diagram showing one embodiment in accordance with the present invention, wherein the same reference numerals are used for denoting the same or similar portions as that of Fig. 4 prior art, and therefore, a duplicate description will be omitted here.
In Fig. 4 prior art, as the band-pass filters 4 and 20, dielectric filters are used. In contrast, in Fig. 1 embodiment, a variable band-pass filter 30 is inserted between the antenna 2 and the mixer 6 and a variable band-pass filter 32 is inserted between the antenna and the amplifier 18.
Selection data for setting receiving frequency at a vacant frequency within the receiving frequency band is given to the PLL synthesizer 8 from a frequency selection means (not shown). Therefore, the PLL synthesizer 8 outputs a frequency control signal (voltage) for controlling a frequency of the VCO 10 and a control signal (voltage) for varying a frequency band of the variable band-pass filter 30. Selection data for setting a transmitting frequency at a vacant frequency within the transmitting frequency band is given to the PLL synthesizer 14 from a frequency selection means such as a keyboard (not shown). Therefore, a frequency control signal (voltage) is outputted from the PLL synthesizer 14 and applied to the VCO 16.At the same time, a control signal (voltage) for varying a frequency band of the variable band-pass filter 32 is outputted from the PLL synthesizer 14 and applied to the variable band-pass filter 32.
If the vacant frequency within the receiving frequency band is 890 MHz or 870 MHz as shown by a solid line or a dotted line in Fig. 1, the PLL synthesizer 8 controls the variable band-pass filter 30 so that a received signal of 890 MHz or 870 MHz which is received by the antenna 2 can be filtered by the variable bandpass filter 30 and, the VCO 10 so that an output of the mixer 6 becomes an intermediate frequency signal of 45 MHz. Therefore, the intermediate frequency signal is inputted to the sound detection circuit (not shown).
If the vacant frequency within the transmitting frequency band is 845 MHz or 825 MHz, the PLL synthesizer 14 controls the VCO 16 so that the center frequency of the frequency-modulated signal from the VCO 16 becomes 845 MHz or 825 MHz and, the variable band-pass filter 32 so that the transmitting signal from the amplifier 18 can be filtered by the variable band-pass filter 32.
Therefore, as shown by a solid line or a dotted line in Fig. 1, the transmitting signal of 845 MHz or 825 MHz is transmitted through the antenna 2.
Fig. 2 is a circuit diagram showing one example of variable band-pass filters which can be utilized in Fig.
1 embodiment. In Fig. 2, a terminal 34 is connected to the antenna 2 and a terminal 36 is connected to the mixer 6 when the filter is used as the variable band-pass filter 30 or to the amplifier 18 when the filter is used as the variable band-pass filter 32. In addition, a terminal 42 is supplied with a control signal (voltage) from the PLL synthesizer 8, and therefore, variable capacitance diodes 38 and 40 can be controlled by the PLL synthesizer 8 when the filter is used as the variable band-pass filter 30 so that a pass band of the filter is varied.On the other hand, when the filter is used as the variable band-pass filter 32, the terminal 42 is supplied with a control signal from the PLL synthesizer 14, and therefore, the variable capacitance diodes 38 and 40 are controlled by the control signal (voltage) from the PLL synthesizer 14 so that a pass band of the filter can be varied.
In the above described embodiment, since the pass bands of the variable band-pass filters 30 and 32 are respectively varied in response to the selection or setting of the receiving frequency and the transmitting frequency automatically, each of the pass bands may be narrow, for example, 2-3 MHz. Therefore, the receiving frequency and the transmitting frequency can be filtered by the variable band-pass filters 30 and 32 at the frequency distance of approximately 40 MHz, and thus, attenuation curves of the variable band-pass filters 30 and 32 may be not so sharp. Accordingly, as the variable band-pass filters 30 and 32, a filter which has low Q and is cheap and can be miniaturized can be utilized.
Fig. 3 is a block diagram showing another embodiment in accordance with the present invention, in which the present invention is applied to Fig. 5 prior art, and therefore, by using the same reference numerals for denoting the same or similar portions as that of Fig.
5, a duplication description will be omitted here.
In Fig. 3 embodiment, the variable band-pass filters 30 and 32 are controlled by an output of the PLL synthesizer 22 which is used for transmitting and receiving circuits. In addition, the variable band-pass filter shown in Fig. 2 may be used as the variable bandpass filters 30 and 32 of Fig. 3 circuit, respectively.
In Fig. 3 embodiment, the variable band-pass filters 30 and 32 are controlled by a control signal (voltage) outputted from the PLL synthesizer 22 which functions as not only a transmitting frequency controlling means but also a receiving frequency controlling means.
In addition, the present invention is applicable to arbitrary mobile radio communication apparatuses such as a land mobile radio telephone other than the US cellular, cordless telephone and etc.
Furthermore, a type or circuit configuration of a variable band-pass filter is not limited to that of the above described embodiment, and therefore, an arbitrary band-pass filter which includes a variable reactance element reactance of which can be controlled by a control signal such as a voltage, current and so on.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

Claims (5)

WHAT IS CLAIMED IS
1. A transmitting/receiving circuit for a mobile radio communication system, comprises: an antenna; transmitting frequency control means for controlling a transmitting frequency; receiving frequency controlling means for controlling a receiving frequency; a first variable band-pass filter for filtering a received signal through said antenna, said first variable band-pass filter having a first band varying portion which receives a first control signal from the receiving frequency controlling means; and a second variable band-pass filter for filtering a transmitting signal and applying the same to said antenna, said second variable band-pass filter having a second band varying portion which receives a second control signal from the transmitting frequency controlling means
2.A transmitting/receiving circuit for a mobile radio communication system in accordance with claim 1, wherein each of said first and second band varying portions includes at least one of variable reactance element reactance of which can be varied by said first and second control signals.
3. A transmitting/receiving circuit for a mobile radio communication system in accordance with claim 2, wherein said variable reactance element includes a variable capacitance diode.
4. A transmitting/receiving circuit for a mobile radio communication system in accordance with claim 1, wherein each of said transmitting frequency controlling means and said receiving frequency controlling means includes a PLL synthesizer.
5. A transmitting/receiving circuit for a mobile radio communication system in accordance with claim 1, wherein said transmitting frequency controlling means and said receiving frequency controlling means include a common PLL synthesizer.
GB9023156A 1989-10-24 1990-10-24 Transmitting/receiving circuit for mobile radio communication system Expired - Lifetime GB2238193B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1278077A JPH03139022A (en) 1989-10-24 1989-10-24 Transmission and reception circuit for mobile radio equipment

Publications (3)

Publication Number Publication Date
GB9023156D0 GB9023156D0 (en) 1990-12-05
GB2238193A true GB2238193A (en) 1991-05-22
GB2238193B GB2238193B (en) 1993-12-15

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Application Number Title Priority Date Filing Date
GB9023156A Expired - Lifetime GB2238193B (en) 1989-10-24 1990-10-24 Transmitting/receiving circuit for mobile radio communication system

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JP (1) JPH03139022A (en)
GB (1) GB2238193B (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0633674A2 (en) * 1993-07-06 1995-01-11 Mitsubishi Denki Kabushiki Kaisha Radio-transceiver with means for reducing interference
WO1995015621A1 (en) * 1993-11-22 1995-06-08 Philips Electronics N.V. A telecommunication system, and a first station, a second station, and a transceiver for use in such a system
EP0929146A1 (en) * 1998-01-12 1999-07-14 Alps Electric Co., Ltd. Tuner for satellite broadcasting receiver
EP1052772A1 (en) * 1999-05-10 2000-11-15 Alcatel Circuit and method for producing a filtered signal
EP1675270A2 (en) * 2004-12-21 2006-06-28 Samsung Electronics Co., Ltd. Noise removing apparatus for wireless transceiver

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6144260A (en) * 1995-06-09 2000-11-07 Matsushita Electric Industrial Co., Ltd. Amplifier
JP2016046548A (en) * 2014-08-19 2016-04-04 シャープ株式会社 Communication device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4399561A (en) * 1980-12-29 1983-08-16 Motorola, Inc. Variable capacitance circuit

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0633674A2 (en) * 1993-07-06 1995-01-11 Mitsubishi Denki Kabushiki Kaisha Radio-transceiver with means for reducing interference
EP0633674A3 (en) * 1993-07-06 1995-08-16 Mitsubishi Electric Corp Radio-transceiver with means for reducing interference.
US5548825A (en) * 1993-07-06 1996-08-20 Mitsubishi Denki Kabushiki Kaisha Radio transmitter with active band-pass filtering
WO1995015621A1 (en) * 1993-11-22 1995-06-08 Philips Electronics N.V. A telecommunication system, and a first station, a second station, and a transceiver for use in such a system
EP0929146A1 (en) * 1998-01-12 1999-07-14 Alps Electric Co., Ltd. Tuner for satellite broadcasting receiver
US6272312B1 (en) 1998-01-12 2001-08-07 Alps Electric Co., Ltd. Satellite broadcasting receiving tuner which inhibits interference caused by satellite broadcast signals having one octave higher frequency band
EP1052772A1 (en) * 1999-05-10 2000-11-15 Alcatel Circuit and method for producing a filtered signal
FR2793619A1 (en) * 1999-05-10 2000-11-17 Cit Alcatel DEVICE AND METHOD FOR PRODUCING A FILTER SIGNAL HAVING A GIVEN FREQUENCY AND A HERTZIAN TRANSMITTER TRANSMITTING AT A FREQUENCY ESTABLISHED BY A FREQUENCY ADJUSTABLE OSCILLATOR
EP1675270A2 (en) * 2004-12-21 2006-06-28 Samsung Electronics Co., Ltd. Noise removing apparatus for wireless transceiver
EP1675270A3 (en) * 2004-12-21 2008-01-23 Samsung Electronics Co., Ltd. Noise removing apparatus for wireless transceiver

Also Published As

Publication number Publication date
GB2238193B (en) 1993-12-15
JPH03139022A (en) 1991-06-13
GB9023156D0 (en) 1990-12-05

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PE20 Patent expired after termination of 20 years

Expiry date: 20101023