EP0996997A1 - Dispositif de separation des signaux hf - Google Patents

Dispositif de separation des signaux hf

Info

Publication number
EP0996997A1
EP0996997A1 EP98965681A EP98965681A EP0996997A1 EP 0996997 A1 EP0996997 A1 EP 0996997A1 EP 98965681 A EP98965681 A EP 98965681A EP 98965681 A EP98965681 A EP 98965681A EP 0996997 A1 EP0996997 A1 EP 0996997A1
Authority
EP
European Patent Office
Prior art keywords
signals
frequency range
electrode
impedance
impedance element
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.)
Withdrawn
Application number
EP98965681A
Other languages
German (de)
English (en)
Inventor
Franciscus Josephus Alfonsus Maria Sessink
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.)
Siemens AG
Original Assignee
Mannesmann VDO AG
Siemens AG
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 Mannesmann VDO AG, Siemens AG filed Critical Mannesmann VDO AG
Priority to EP98965681A priority Critical patent/EP0996997A1/fr
Publication of EP0996997A1 publication Critical patent/EP0996997A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • H03H7/1758—Series LC in shunt or branch path
    • 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
    • H03H7/0115—Frequency selective two-port networks comprising only inductors and capacitors
    • 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
    • H03H7/1766—Parallel LC in series path
    • 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
    • H03H7/46—Networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source

Definitions

  • the invention relates to a device for separating RF signals in at least a first and a second frequency range, which device comprises a first electrode for supplying the RF signals and also a second electrode for supplying the RF signals in the first frequency range.
  • the invention also relates to an assembly of an antenna and such a device.
  • a device as described in the opening paragraph is currently often used in motorcars which are equipped with an antenna suitable for receiving both radio and telephony signals and is also suitable for transmitting telephony signals.
  • radio signals are AM and FM signals.
  • GSM signals are examples of telephony signals.
  • the radio signals received by such an antenna can be processed and reproduced by a radio receiver.
  • it is necessary that the telephony signals in a device as described in the opening paragraph are separated from the radio signals.
  • the use of the known devices leads to a considerable decrease of the sensitivity of the radio reception because the radio signals are also attenuated by these devices. This is a great problem, notably for the reception of AM signals.
  • the device according to the invention is characterized in that the first electrode is coupled to the second electrode via a first impedance element, the second electrode is coupled to a reference point via a second impedance element, and the first impedance element has a first impedance value which is comparatively high for the RF signals in the second frequency range and comparatively low for the RF signals in the first frequency range, the second impedance element having a second impedance value which is substantially equal to zero for the RF signals in the second frequency range and unequal to zero for the RF signals in the first frequency range.
  • the invention is based on the recognition that, in the known devices, the attenuation of the RF signals in the first frequency range is caused by the fact that the known devices are provided with one or more capacitors coupled between the signal path and ground.
  • the use of such capacitors follows from the application of one of the conventional methods of designing filters.
  • the use of said capacitor is not necessary.
  • the impedance of the first impedance element is high and the impedance of the second impedance element is substantially equal to zero.
  • the first impedance element ensures a considerable attenuation of the RF signals in the second frequency range
  • the second impedance element constitutes a short circuit to the reference point for these RF signals, which reference point may be, for example ground. Both effects jointly ensure a substantial suppression of the RF signals in the second frequency range.
  • the impedance of the first impedance element is comparatively low and the impedance of the second impedance element is unequal to zero.
  • the RF signals in the first frequency range are hardly attenuated by the first impedance element, while the RF signals are not short-circuited to the reference point by the second impedance element. Both effects jointly ensure a substantially unchanged transfer of the RF signals in the first frequency range to the second electrode.
  • the second impedance element comprises a series arrangement of a coil and a capacitor.
  • a series-resonant circuit is obtained having an impedance which is substantially equal to zero at a first resonance frequency f res ,.
  • L is the inductance of the coil
  • Cj is the capacitance of the capacitor, f res
  • the impedance of the series arrangement is unequal to zero.
  • a further embodiment of the device according to the invention is characterized in that the first impedance element comprises a parallel arrangement of a second coil and a second capacitor.
  • the first impedance element comprises a parallel arrangement of a second coil and a second capacitor.
  • Another embodiment of the device according to the invention is characterized in that the second resonance frequency ranges between a fundamental frequency of the RF signals in the second frequency range and a harmonic of said fundamental frequency. It is thereby achieved that both the fundamental frequency and its harmonic are substantially attenuated by the parallel arrangement.
  • Fig. 1 shows an embodiment of a device according to the invention.
  • Fig. 2 is an electric circuit diagram of an antenna circuit incorporating a device according to the invention.
  • Fig. 1 shows an embodiment of a device according to the invention.
  • This device may be used for separating RF signals in different frequency ranges such as, for example radio signals (AM, FM) and telephony signals (GSM).
  • AM, FM radio signals
  • GSM telephony signals
  • these RF signals must be applied to a first electrode 10 of the device.
  • This first electrode 10 is coupled to a second electrode 16 via a first impedance element 12.
  • This second electrode 16 is coupled to a reference point 18 via a second impedance element 14, which reference point 18 is grounded.
  • the RF signals applied to the first electrode 10 and located in a first and a second frequency range, respectively, are separated from each other in such a way that substantially only the RF signals in the first frequency range are obtainable from the second electrode 16.
  • the first impedance element 12 may be constituted by a parallel arrangement of a coil 20 and a capacitor 22. It is known that the impedance of such a parallel arrangement is frequency-dependent, with this impedance showing a peak at a first resonance frequency which is equal to l/27rVL,C 1 .
  • Lj represents the inductance of the coil 20
  • C ⁇ represents the capacitance of the capacitor 22.
  • the parallel arrangement has a comparatively low impedance for frequencies which are unequal to the first resonance frequency. It is to be noted that, in many cases, the parasitic capacitance of the coil 20 cannot be left outside consideration when computing the first resonance frequency. As the case may be, this parasitic capacitance alone may already be large enough to reach the desired first resonance frequency.
  • the capacitor 22 can then of course be dispensed with.
  • the second impedance element 14 may be constituted by a series arrangement of a coil 24 and a capacitor 26.
  • Such a series arrangement is also known to have an impedance which is frequency-dependent and is substantially equal to zero at a second resonance frequency which is equal to l/2 ⁇ L 2 C 2 .
  • L 2 represents the inductance of the coil 24 and C 2 represents the capacitance of the capacitor 26.
  • the impedance of the series arrangement is unequal to zero for frequencies which are unequal to the second resonance frequency.
  • the RF signals in the first frequency range for example AM signals between 150 kHz and 30 MHz, are hardly attenuated by the low impedance of the parallel arrangement, while these RF signals are not short-circuited to ground 18 by the series arrangement. Both effects jointly ensure a substantially unchanged transfer of the RF signals in the first frequency range to the second electrode 16.
  • the device according to the invention is preferably used in combination with an antenna which is suitable for receiving radio and telephony signals and is also suitable for transmitting telephony signals.
  • antennas are currently often used in motorcars.
  • the telephony signals can be prevented from having a disturbing influence on the radio reception.
  • Such an antenna can be coupled to the device according to the invention via the first electrode 10.
  • Fig. 2 is an electric circuit diagram of an antenna circuit incorporating a device according to the invention.
  • This antenna circuit may be coupled to an antenna as described above via a first electrode 10.
  • a telephone may be connected to an electrode 32.
  • telephony signals received by the antenna can be passed on to the telephone via a capacitor 30.
  • the telephony signals generated by the telephone can be applied for transmission to the antenna via the capacitor 30.
  • the device according to the invention is arranged between the first electrode 10 and the second electrode 16.
  • the first impedance element 12 is constituted by the coil 20 which, together with its own parasitic capacitance, constitutes a parallel-resonant circuit.
  • the second impedance element 14 is constituted by the series arrangement of the coil 24 and the capacitor 26.
  • the telephony signals are suppressed to a considerable extent by the device according to the invention as described hereinbefore, so that substantially only the radio signals (AM and FM signals) received via the antenna are present at the second electrode 16. These AM and FM signals are subsequently separated by the antenna circuit whereafter they are amplified.
  • the AM signals are suppressed to a considerable extent by the series arrangement of the capacitor 40 and the coil 42 which, together with the antenna, has a resonance frequency of approximately 100 MHz. Consequently, substantially only the FM signals are present at the base of the transistor 46. Together with the resistors 44 and 50 and the coil 48, this transistor 46 constitutes a negative feedback amplifier which amplifies the FM signals.
  • This FM amplifier has a high input impedance so that the very frequency-dependent source resistance constituted by the capacitor 40 and the coil 42 does not substantially influence the transmission of the FM signals.
  • the emitter of the transistor 46 is connected to ground via the coil 48. This provides a negative feedback for the FM signals.
  • a resistor instead of the coil 48 is often used for this purpose.
  • the use of the coil 48 has the advantage that it does not introduce noise and that no losses occur.
  • the coil 34 constitutes a parallel-resonant circuit. Since this resonant circuit resonates at approximately 100 MHz, substantially only the AM signals are passed on to the capacitor 52. Unwanted low-frequency components are filtered from these AM signals by this capacitor 52.
  • the AM signals filtered in this way are subsequently amplified in an amplifier comprising two MOS transistors 60 and 62 and the resistors 54, 56, 58 and 64. This amplifier is linear through a comparatively large range because the MOS transistors 60 and 62 are arranged in parallel. Due to this measure, a noise adaptation to the capacitive source is also obtained.
  • the resistors 54 and 56 ensure a further suppression of the telephony signals.
  • the combination of the coil 34 and the input capacitances of the MOS transistors constitutes a resonant circuit.
  • the unwanted frequency dependence of this resonant circuit is limited by the attenuation resistor 36.
  • the coil 76 ensures that FM signals which are applied to the electrode 84 via the coil 82 and the capacitor 80 cannot reach the AM-specific part.
  • the series arrangement of the coil 82 and the capacitor 80 ensures that AM signals cannot reach the FM-specific part.
  • the amplified AM and FM signals are joined again for their supply to a radio receiver.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)

Abstract

L'invention concerne un dispositif permettant de séparer les signaux HF selon au moins une première et une seconde plage de fréquence. Ce dispositif comprend une première électrode (10) servant à produire les signaux HF et une seconde électrode (16) servant à fournir les signaux HF compris dans la première plage de fréquence. La première électrode (10) est couplée à la seconde électrode (16) via un premier élément (12) d'impédance. La seconde électrode (16) est couplée à un point (18) de référence via un second élément (14) d'impédance. La première valeur d'impédance d'un premier élément (12) d'impédance est haute pour les signaux HF situés dans la seconde plage de fréquence, tandis que cette première valeur d'impédance est relativement basse pour les signaux HF se trouvant dans la première plage de fréquence. Une seconde valeur d'impédance du second élément (14) d'impédance est sensiblement égale à zéro pour les signaux HF compris dans la seconde plage de fréquence et cette seconde valeur d'impédance est différente de zéro pour les signaux HF compris dans la première plage de fréquence.
EP98965681A 1997-11-27 1998-11-20 Dispositif de separation des signaux hf Withdrawn EP0996997A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP98965681A EP0996997A1 (fr) 1997-11-27 1998-11-20 Dispositif de separation des signaux hf

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP97203702 1997-11-27
EP97203702 1997-11-27
PCT/EP1998/007451 WO1999029038A1 (fr) 1997-11-27 1998-11-20 Dispositif de separation des signaux hf
EP98965681A EP0996997A1 (fr) 1997-11-27 1998-11-20 Dispositif de separation des signaux hf

Publications (1)

Publication Number Publication Date
EP0996997A1 true EP0996997A1 (fr) 2000-05-03

Family

ID=8228979

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98965681A Withdrawn EP0996997A1 (fr) 1997-11-27 1998-11-20 Dispositif de separation des signaux hf

Country Status (2)

Country Link
EP (1) EP0996997A1 (fr)
WO (1) WO1999029038A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7425880B2 (en) * 2005-01-20 2008-09-16 Tdk Corporation Filters with improved rejection band performance

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5173671A (en) * 1990-12-18 1992-12-22 Raytheon Company Monolithic lumped element networks
US5652599A (en) * 1995-09-11 1997-07-29 Qualcomm Incorporated Dual-band antenna system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9929038A1 *

Also Published As

Publication number Publication date
WO1999029038A1 (fr) 1999-06-10

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