Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P1/00—Auxiliary devices
  • H01P1/20—Frequency-selective devices, e.g. filters
  • H01P1/201—Filters for transverse electromagnetic waves
  • H01P1/203—Strip line filters
  • H01P1/2039—Galvanic coupling between Input/Output
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
  • H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced lines or devices with unbalanced lines or devices
  • H01P5/1007—Microstrip transitions to Slotline or finline
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P1/00—Auxiliary devices
  • H01P1/24—Terminating devices
  • H01P1/26—Dissipative terminations
  • H01P1/268—Strip line terminations

Definitions

• Multistandard multi-mode user terminals integrate multiple radiocommunication or wireless communication systems and experience strong interference due, on the one hand, to the proximity of the frequency bands allocated to the different systems and, on the other hand, to the proximity antenna physics, the size of the terminals being more and more reduced. This results in harmful parasitic interactions between the different systems.
• a first known solution is to introduce, within the terminal, a frequency-selective filter in the transmission-reception chain of each of the systems, this filter being intended to reject unwanted frequencies for the system considered. , such as parasitic lines from other systems, and / or parasites from the transmission / reception chain in question and / or harmonics.
• these filters being very severe (very low insertion losses, high selectivity and very narrow bandwidth), they can not currently be made in a low-cost technology, for example with printed circuits. based on FR4 type substrate.
• An object of the invention is to provide a microstrip line / slot line transition circuit capable of filtering unwanted frequencies without degrading the performance of the transition circuit in its useful band.
• Another object of the invention is to provide such a transition circuit that is feasible in a low cost technology.
• the subject of the invention is a transition circuit from a microstrip line to a slot line comprising a substrate provided with a ground plane, a microstrip line formed on said substrate at a predetermined distance from the ground plane, and extending from a first input / output port, and a slot made in the ground plane forming a slot line extending substantially perpendicular to said microstrip line to a second input / output port and crossing said microstrip line in a so-called coupling zone of the transition circuit, said line microstrip having a first microstrip line portion for transmitting a signal between the first input / output port and the coupling area, and a second microstrip line portion, said slot line having a first slit line portion for transmitting said signal between the coupling area and the second input / output port, and a second slot line portion.
• the slot line comprises a first filter circuit connected to the coupling zone via said second slot line portion, said first filter circuit and said second slot line portion being adapted to return to the slot line, to the level of the coupling zone, an impedance substantially equal to the impedance of an open circuit for at least one desired frequency of the signal and an impedance substantially equal to the impedance of a short circuit for at least one undesired frequency of the signal .
• a filter circuit connected to the second slot line portion is used to reflect, by reflection, optimal electromagnetic coupling conditions on the slot line at the coupling area of the transition circuit for the desired frequency and quasi-zero electromagnetic coupling conditions for the unwanted frequency.
• a filtering circuit is also connected to the second slot line portion to reflect, by reflection, optimal electromagnetic coupling conditions on the microstrip line at the coupling area of the transition circuit for the desired frequency and quasi-zero electromagnetic coupling conditions for the unwanted frequency.
• the microstrip line then comprises a second filter circuit connected to the zone of coupling via said second microstrip line portion, said second filter circuit and said second microstrip line portion adapted to return to the microstrip line, at the coupling area, an impedance substantially equal to the impedance of a short circuit for said at least one desired frequency and an impedance substantially equal to the open circuit impedance for said at least one undesired frequency.
• the first and second filter circuits are notch filters rejecting said at least one desired frequency and passing said at least one undesirable frequency.
• the first and second filtering circuits are bandpass filters passing said at least one unwanted frequency and rejecting said at least one desired frequency.
• the transition circuit is made in a low-cost technology, for example by producing the circuit on a FR4-type substrate.
• the invention also relates to a multistandard terminal comprising at least one transition circuit as described above.
• FIG. 1 a schematic view of a conventional microstrip line / slot line transition circuit, of the Knorr type
• FIG. 2 a graph illustrating the simulated transmission response S (2.1) of the circuit of FIG. 1;
• FIG. 4 is a schematic view of the microstrip line / slot line transition circuit according to the invention and using notch filters;
• FIG. 5 graphs illustrating the simulated responses in transmission and reflection of a band-cut Chebyshev filter employed in the circuit of FIG. 4;
• FIG. 6 an abacus illustrating the reflection response at the input of the Chebyshev filter
• Figures 1 to 3 show a microstrip line transition line / classical Knorr type slot line.
• the transition circuit is made on a substrate S provided with a ground plane. It comprises a microstrip line 1 and a slot line 2 etched in the ground plane, the microstrip line being disposed at a predetermined distance from the ground plane.
• the microstrip line 1 terminates at a first end 1a through an input port P1 and at a second end 1b through an open circuit CO.
• the slot line 2 terminates, at a first end 2a, by a short circuit CC and, at a second end 2b, by an output port P2.
• the port PI is connected to a transmission chain and the port P2 is connected to a slot antenna.
• the microstrip line 1 comprises a portion 11 of microstrip line connected to the port PI extending through a portion 12 of microstrip line, said coupling portion, disposed above the slot line 2, said coupling portion 12 extending there even by a portion 13 terminating in an open circuit.
• the slot line 2 comprises a portion 21 of slot line connected to the port P2 extending through a slot line portion 22, said coupling portion, disposed below the microstrip line 1, said coupling portion 22 is extending itself by a portion 23 ending in a short circuit CC.
• Portions 12 and 22 define the Z coupling zone mentioned above. The transfer of energy from the port PI to the port P2 is by electromagnetic coupling of the portions 12 and 22.
• the portions 13 and 23 In order to obtain optimum electromagnetic coupling conditions between the microstrip line 1 and the slot line 2, the portions 13 and 23 must respectively bring back a short circuit and an open circuit at the level of the transition zone Z.
• the length of the portion 13 must be substantially equal to ⁇ / 4 where ⁇ is the wavelength guided in the microstrip line associated with a desired frequency f (working frequency of the transition circuit).
• the length of the portion 23 should be substantially equal to Xf1 / 4 where Xfl is the guided wavelength in the slot line associated with the desired frequency f1.
• the portions 11 and 21 have the function of reducing, respectively to the ports PI and P2, an impedance close to that present at the ports PI and P2, generally 50 ohms for PI and of the order of 80-100 ohms for the port P2.
• this transition circuit from a microstrip line to a slot line is applicable to operation in the 5GHz WiFi band. It was made on a multilayer substrate based on FR4 material at very low cost.
• the transition circuit of FIG. 1 has the following characteristics: very wide bandwidth, of the order of
• a microstrip line / frequency selective slit line transition is proposed, capable of passing desired frequencies contained in a useful band and of rejecting frequencies outside this useful band.
• FIG. 4 A schematic diagram of the transition circuit according to the invention is shown in FIG. 4. With respect to the diagram of FIG. 1, the transition circuit comprises the following modifications:
• microstrip line 13 is connected at its end 1a to a notch filter SBFm grounded through a load resistor Rm, said filter being designed to reject the frequencies of the useful band;
• the slit line portion 13 is connected at its end 2a to a SBFs filter grounded through a load resistor Rs, this filter is also designed to reject the frequencies of the useful band.
• the role of filters is to provide the desired selectivity by level of the coupling zone Z the optimum coupling conditions, ie a short-circuit (respectively an open circuit) for the microstrip line (respectively slot line) in the useful band of the transition.
• a short-circuit ie an open circuit
• the microstrip line ie slot line
• the purpose of the line portions 13 and 23 is to reduce the impedances of the inputs C and D of the filters to the impedances required at the coupling zone to favor the maximum power transfer in the useful band from the PI Port to the P2 Port and according to the KNORR principle, namely a zero impedance (short circuit) in B and an infinite impedance (open circuit) in A.
• the impedance levels sought at the coupling zone outside and in the useful band of the transition namely: the characteristic impedances and the lengths of the portions of the line 13 and 23, the load resistances Rm and Rs, the impedances of the intrinsic elements to each of the SBFm and SBFs filters.
• the line portion 11 serves, if necessary, to reduce the impedance at the port PI to the usual value of 50 ohms.
• the transition circuit of FIG. 4 was simulated using the Agilent / ADS software for a filter transition allowing the band 5 to 6 GHz to pass.
• the coupling of the portion 12 of the microstrip line with the portion 22 of the slot line was modeled with the Agilent / Momentum electromagnetic simulator to extract the parameters S.
• a simulation of the circuit was performed by taking for the other components of the circuit, namely the other portions of the line and the charged filters, their electrical equivalent model, thus disregarding their technique and production technology.
• Line portions are defined by their electrical length at a given frequency and their characteristic impedance.
• a filter having a Chebyshev-type response has been selected with the following characteristics:
• the impedance returned to the filter inputs in the rejection band is an open circuit for the SBFm filter and a short circuit for the SBFs filter;
• FIGS. 5 and 6 show the responses of a SBFm filter thus defined.
• FIG. 5 shows the insertion losses, the bandwidth and the rejection level
• FIG. 6 shows that this filter SBFm does indeed have a circuit open at its inputs at the center frequency of 5.5 GHz.
• the 2 filters of the circuit are of order 2 and have theoretical insertion losses of 2dB.
• the parameters of the integrated components of the circuit of FIG. 4 are given in the table below. They have been optimized to meet the requirements to achieve the desired performance.
• the PI excitation port is also well adapted (dB (Sll)). This shows that the signal is not reflected and is transmitted to a load, in this case the load Rm of the notch filter SBFm. This is only possible because, outside of the transition bandwidth, the slit-band notch filter SBFs does bring a very low impedance back to the coupling area at point A. This is shown in Figure 9. In this figure, it can be seen that the notch filter reduces to point A a low impedance close to a short circuit at 3GHz and at 8 GHz (outside the bandwidth) and an open circuit at 5.5 GHz (in bandwidth) .
• the transmission response of the transition circuit described above is of the bandpass type, the interfering frequencies to be suppressed being present outside the bandwidth of the circuit.
• the notch filters can be replaced by bandpass filters so as to obtain a response of the notch transition circuit.
• a response of the notch transition circuit makes it possible, for example, to reject an interfering signal in a well-identified frequency band.
• This embodiment has been simulated.
• the two bandpass filters used for this simulation are of order 2, centered around 4.2GHz and have a very narrow bandwidth equal to 100MHz.
• the simulated responses of the transition are shown in Figures 10 and 11. In the transmission response, we find here the bandpass response of a classical transition. But it will be noted especially that the band is cut around 4.2GHz because of the presence of the two bandpass filters of the transition circuit.
• the transition can be ultra-selective in frequency and the insertion losses do not depend on those of the filters introduced into the circuit, but essentially those of the coupling zone; this means that the filters can be made using very low cost technologies, and the quality factors of the resonant elements of the filters can be low;
• the transition does not require that the inserted filters be of high order to obtain a very selective frequency response, resulting in a gain in size.
• the SBFm filter mounted on the microstrip line can be eliminated to the detriment of the frequency discrimination performance of the transition circuit
• the circuit can also be used as a conventional filtering circuit inserted in a transmission / reception chain, in which case it will be sufficient to connect to the port P2 a transition circuit.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Control Of Motors That Do Not Use Commutators (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=47291012

Family Applications (1)

Country Status (7)

Family Cites Families (5)

• 2011
  • 2011-12-12 FR FR1161437A patent/FR2984018A1/fr not_active Withdrawn
• 2012
  • 2012-12-06 CN CN201280061425.2A patent/CN103988363B/zh not_active Expired - Fee Related
  • 2012-12-06 US US14/362,516 patent/US20150022280A1/en not_active Abandoned
  • 2012-12-06 WO PCT/EP2012/074659 patent/WO2013087509A1/fr active Application Filing
  • 2012-12-06 KR KR1020147019412A patent/KR20140100577A/ko not_active Application Discontinuation
  • 2012-12-06 EP EP12795473.3A patent/EP2792016B1/de not_active Not-in-force
  • 2012-12-06 JP JP2014546427A patent/JP2015505198A/ja not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events