Duplexer with improved transmission/receiving band separation

description

Duplexer with improved transmission / reception band separation

radio systems in wireless communication systems, especially in motor, which do not allow TDD (Time Domain Duplexmg), typically two, different frequency bands are provided, which seen from the viewpoint of the Kommumkationsteilnehmers serve as transmitting and receiving band. In Kommumkation- sendgerat, particularly in Mobilfunkgerat (mobile phone) is to

Sending and receiving signals using the same antenna. For the separation of transmitted and received signals, therefore, a duplexer is generally necessary, which is connected between the antenna and transmit and receive paths. Such consists essentially of two interconnected filters together, namely an RX filter between the antenna and the Rx path (LNA = Low Noise Amplifier) ​​for received signals and a Tx filter between Tx path (PA = Power Amplifier) ​​and antenna for signals to be transmitted.

Since the Kommunikatlonsendgerat transmit and receive simultaneously may need, each of the two filters must be able to suppress a located in the other frequency band signal good Typical values ​​that m such drantlosen communication systems, for example for the suppression of the Tx-band through the

Rx filters are required, are in the range of 50 dB and more Simultaneously, the respective signals must when passing through the filter in each frequency band with minimal losses experienced A typical value for a maximum tolerated figurable attenuation of the Tx band in the Tx filter 2 dB or better.

Known duplexer that this Noher on f or the band separation (Sperrbereichsuncerdruckung) and meet the Emfuge- evaporation are constructed as of microwave ceramic filters. With sufficient bandgap of TX and Rx band also Oberflachenwellenfllter (SAW filter) may be used will. However, if TX and Rx bands very close together, all requirements can simultaneously alone very difficult or impossible to comply with SAW filters. An example of such a system is the American CDMA / TDMA-1900 (in accordance with IS-95 or IS-136), in which transmission and reception bands each 60 MHz wide, and wherein a duplex distance (= constant-distance between the transmitter - and receiving signals) provided by 80 MHz. In said bandwidth while remaining between the two bands, only a separation of 20 MHz, which corresponds to approximately 10,000 ppm of the said frequency band. Within only 20 MHz has to 2 dB attenuation m pass the restricted area, where for example, the aforementioned 50 dB attenuation are required the respective filter from the passband with eg. This requires a ύbertragungsverhalten having steep flanks in the passband. In addition, since even a temperature dependent frequency drift of the filter as well as manufacturing tolerances are taken into account, it has heretofore been impossible to build such a duplexer only on the base of SAW filter technology. For ren SAW filters weighing necessary, having a passband with extremely steep sides.

Object of the present invention is therefore to provide a duplexer for such communication systems, which allows the use of SAW filter technology, thus allowing further miniaturization of duplexers.

This object is achieved with a duplexer Claim 1. Advantageous embodiments of the invention are found in the dependent spruchen.

The invention is based on the idea, at least one of the filter between the antenna and RX path (Empfangsfllter) and between antenna and TX path (transmission filter) from assembling at least two partial filters whose pass bands are m mutually adjacent frequency sub-ranges of the required transmission or reception band and thereby the entire Tape covering. These trained as part Oberflächenwellenfllter filters can then be correspondingly narrower bandwidth than the filter used to date. Each of the two as part of filter will only ken abzudek- half the bandwidth of the corresponding transmission or reception band. From the addition of the two frequency sub-ranges results in the required overall width of the corresponding transmission or reception band.

For a narrow band SAW filter a better optimization is possible, in particular, allows the formation of steeper flanks in the pass band. Even with only one m the slope verbeserten flank, provided that the adjacent reception relationship as transmission band defines the corresponding transmit or receive band, a better separation of the bands is possible. Thus, the split filter can be formed as SAW filters, which because of not steep enough adjustable flanks and low bandgap was not possible hitherto. With the steeper flanks of the partial filter, the invention also allows for better suppression of the other band (transmission or reception band) of 50 dB and more. Moreover, does not apply to the use of SAW filters of xern conventional duplexers of microwave ceramic (MWK) quenzlage for adjusting the frequency required balance.

Preferably, both input and Ausgangsfllter are formed as split surface chenwellenfllter. Thus, the duplexer according to the invention consists entirely of SAW filters, so that the advantages of SAW filters over conventional MWK filters or duplexers can be fully utilized. In particular, with a composed only of SAW filters duplexer further miniaturization possible, which also further miniaturization of the corresponding terminals, m which the duplexer according to the invention

is to be used, allows. Since provided in the transmission and the reception band filter part for frequency sub-ranges are, which are narrower than the entire band, a suppression of the other bands or frequency portion is easily possible. Have been used for example for the American CDMA-1900 system input and output filters with a bandwidth of 60 MHz, so remained in a duplex spacing of 80 MHz between the two bands (frequency ranges) a maximum distance of 20 MHz. According to the invention having split into at least two sub-filters input and output filters now a spacing of 50 MHz is possible. For better suppression of the other band can even reach under non-optimal edges of the corresponding passbands. By building exclusively of SAW filters and a single-chip solution for all filters of the duplexer is possible.

When duplexer according to the invention also may be to switch between the sub-filters and thus provided for switching between the frequency sub-ranges switch. By the provision of a switch only one of the filter element of the split SAW filter to the antenna, the sub-filter is respectively always connected, so that the one or other of the filter does not interfere with the properties of the "active" part of the filter. Thus, it is also possible to independently to optimize to a suitable frequency position and an appropriate flank slope towards. Are input and output filters designed as split SAW filters, then each filter element of the input filter is associated with a filter element of the output filter, which together form a partial filter pair. with the help of a common switch or two individual switches can then sync. to switch from an active further to a previously passive partial filter pair. the partial filter pairs are the frequency sub-ranges assigned so that the Duplexerabstand is respected. Übli^¬ cherweise thereby the frequency locations of the sub-filter are shifted by the same amount in input and output filter to each. This shift takes place in pairs. In a further advantageous embodiment of the duplexer for transmitting and receiving within at least two different communication systems adapted to use the different frequency bands. This is achieved m simply by the number of inputs and Ausgangsfllter and the associated switch is multiplied accordingly. For each communication system for which the duplexer according to the invention is designed, therefore, a separate set of input and output filters and associated switches is provided. So far known are, for example Endgerate, which are intended for use m two different communication systems (dual-band mobile phone) and use a separate duplexer for each of these systems. Erfmdungsgemaß it is also possible to provide a duplexer for more than two Kommunikationssy- interpreted systems.

In a further embodiment of the invention can switch a switch between both sub-filter pairs within a communication system as well as between part-filter pairs which are two different communication system belongs.

Here also the duplex spacing may alter and thus terpaare the distance between the frequency of partial Bereicher Teilfil-. If the two Kommunikationssysteπe be parallel to each other and have different degrees of coverage up, better network coverage is possible for the erfindungsgemaßer duplexer-use Kommunikatlonsendgerat. If different communication systems used m different countries, so can a participating Kommumkationsendgerat cross-border m both systems are used. Common advantage ISC always that only a duplexer for the different communication systems is required this can m two communication systems splits the input and / or output filter m to make two or more sub-filters. However, it is also possible that a communication system has a sufficiently high duplex spacing, with the aid of a respective SAW filter for input and Ausgangsfllter can be realized. In combination with a communication system which split the input and / or output filter which gives s ch as a duplexer according to the invention, a changeover possibility between at least three pairs of filters, of which at least two Teilfliterpaare on OFW are based.

Preferably, all inputs and Ausgangsfllter of You- are plexer and optionally moreover arranged the switch m a common housing or at least on a common engine module. Such is easier to handle by the device manufacturers and can be m optimize the properties easier.

Preferably, an inventive duplexer exclusively is lent from the surface acoustic wave filters for the receive and the transmit band constructed, all of which are integrated on a common piezoelectric substrate or disposed on two substrates. Due to the high integration density this potential can be with the former version of the highest Mmiaturisierungsgrad for the duplexer reach. On a common substrate and the common use of other switching and network components for the different filters is possible, which results in a further increase in the integration density. On the common substrate also has a simplified adjustment of the filters to each other and to a network is possible.

In addition, it is possible to filter all the and sub-filter together with an adjustment may be necessary network of passive components and the switches to be integrated on a common module. This also simplifies the handling and simplifies the application, since the terminal manufacturers must process only one module.

For the surface acoustic wave filters and SAW Teilfllter as

Substrate material lithium red y preferably with an average angle of 35 ° to 46 ° (LT35-46). This material a particularly good temperature coefficient, with which transmission behavior an excess can be adjusted with narrow bandwidths and steep flanks.

Since lead less steep edges to the desired decoupling between transmit and receive bands with the inventive duplexer due to the higher distance between the frequency sub-ranges, the use of lithium is in principle red y with a cutting angle 60-70 ° (LN60-70) and in particular near 64 ° (LT64) possible. This can be compared with lithium even lower insertion losses reach. This may be particularly when using lithium for the Ausgangsfllter advantageous, since in particular in the communication terminal a high transmission power is desired for the turn, a low insertion loss is required. At a constant transmission power, a lower insertion loss has a lower power requirements result.

It is also possible to provide for input and Ausgangsfllter SAW filters, which are based on different Substratmateπalien. Preferred is the combination of lithium and lithium for the Ausgangsfllter for the input filter.

To achieve the good filter natural saddle th preferably Elektrodenmateπal is correspondingly power resistant. Well suited are therefore electrodes, the following material layers or a sandwich structure with the following Mateπalschicht- kombmationen comprise: aluminum and copper layers, aluminum and magnesium layers or aluminum / copper and copper or magnesium films.

An improved Leistungsvertraglichkeit is also achieved when a comprehensive titanium layer, especially a titanium layer is provided between Elektrodenmateπal and substrate. Preferably the Oberflächenwellenfllter of erfm- dungsgemaßen duplexers are designed as Reaktanzfllter with which to achieve the required high Einfugedampfung especially when Ausgangsfllter well is

In the following, the invention is based on Ausfuhrungsbei- and the associated seven figures explained in more detail

Figure 1 shows the position and arrangement of transmit and receive bands.

Figure 2 shows a real filter curve

Figure 3 shows arrangement and location of Frequenzteilbe- rich according to the invention

4 to 6 intrinsically different levels of integration of a

Duplexer including peripherals.

Figure 7 shows an exemplary interconnection of

Port resonators to Reaktanzfllter

Figure 1 shows a schematic representation m Anorαnung and location of transmission band TX and RX receiving tape of the American CDMA 1900 system, the transmission band TX ranges from 1850 to 1910 MHz and is thus 60 MHz wide. The reception band RX ranges 1930-1990 MHz and thus also has a width of 60 MHz. A communication link uses seen from the communication terminal device from 10ns- for example, a transmission frequency fxT, which lies in the transmission band TX and simultaneously to a reception frequency in the reception band RX fxR. The distance between fxT and fxR is called the duplex spacing DA and amounts for said CDMA system 80 MHz for a communication connection within the system all pairs of frequencies with the duplex spacing 80 MHz are suitable for the distance BA between the transmission band TX and reception band RX amounts 20MHz Figure 2 shows a schematic representation of a possible m transmission curve of a filter with including drawn in the required bandwidth, here the transmission band TX. Decisive for the filter quality is in particular the Emfugedampfung ED. This is within the corresponding band of the greatest distance from the dashed Nulllmie for zero damping the transmission curve. Usually, the passband is wider than the required frequency range of the respective belt as the edges of a filter in the passband

(Passband) can not be adjusted vertically. When m the figure transmission curve shown for a transmission filter the right flank F_re crucial that borders the passband hm to the adjacent frequency range of the reception band RX off. This edge must be steep enough, the order here

Input filter in the area of ​​the reception band RX has a sufficiently low sensitivity or a sufficiently high stopband rejection SU. For a corresponding input filter the left flank would be F₁ passband crucial that separates the reception band RX hm for transmission band TX.

Figure 3 shows how the present invention, the transmitting and reception areas TX, RX e two frequency sub-ranges of Lden here Roommate bandwidth are split. In each case a frequency portion TX1, TX2 of the transmission band is a frequency quenzteilbereich RX1, RX2 of the receive bands allocated so that the duplex spacing DA can be adhered to. For example, a transmission frequency fXT the required duplex spacing DA is assigned a receiving frequency fxR of for example 80 MHz. While the distance BA between transmit and receive bands with known duplexers the distance FLR - f3T equivalent, it is in accordance with the invention split transmission or reception bands, respectively associated filter FLR - F2T = F2R - f3T = 50 MHz (for said CDMA system). Belonging to the respective frequency sub-ranges filters have a m entsprecnenden the frequency sub-ranges Passband on. Due to the higher bandgap BA filter with less steep edges are possible to select, however, still reach the required Sperrbereichsunterdruckung SU of typically 50 dB.

In addition to the sharing of transmit and receive bands m shown here two frequency sub-ranges Txl, Tx2; Rx, Rx2, it is also possible, m three or more frequency sub-ranges divide the respective bands, being provided for eden frequency portion a private part filter

Figure 4 shows a schematic representation m a four-part filters FR1, FR2, FT1, FT2 duplexer including its interconnection with an antenna A and the associated sensor depfad-PA and the reception deposit-LNA. Both the input filter and the Ausgangsfllter are designed as split Oberfla- chenwellenfllter with e two sub-filters. The Emgangsfllter includes the partial filter FR1 and FR2, while comprising Ausgangsf lter the partial filter FT1 and FT2. see intermediate antenna A and consisting of the four sub-filters duplexer is arranged a switch S, which can switch between two part filter pairs FT1 / FR1 and FT2 / FR2. A Teilfliterpaar each case includes a filter input and output filters, for example, the pair FRI / FTL or FR2 / FT2 More Switches S^λ S^{, v}- For example, connect the components of the receive path LNA with the input filter, the switch S switches between the sub-filters of the input filter. According switches the switch S between the various output filters FT1 and FT2, which are selectively connected to the components of the transmission path PA. The broken line a module Ml is shown, are integrated on the de four part filter. The matching network, consisting for example of passive components such as resistors, capacitors and inductors or strip lines (m the figure not shown), such as the switch S is also realized outside the module Figure 5 shows a corresponding arrangement in which, however, on an enlarged module M2 adjacent to the sub-filters in addition the matching network is still integrated.

E even higher integrated module M3 is shown m FIG. 6 This module M3 comprises the sub-filters additionally the matching network and the switch S.

Figure 7 shows a schematic representation m a circuit arrangement for a built-up of surface wave-port resonators Reaktanzfllter. Em SAW Emtorresonator is constructed on a piezoelectric substrate 1, and includes a provided with two terminals Interd gitalwandler IDT which is disposed between two reflectors Ref. For a simple Reaktanzfllter two such Emden are now at least torresonatoren connected such that at least one of the resonators is disposed in series between input and output ES AS and at least one of the resonators m is connected to a parallel branch to the ground. Em serial resonator, such as RIS, together with an adjacent parallel resonator R1P em phalanx of Reaktanzfllters. Preferably em Reaktanzfllter, however as shown m the figure of several series-connected basic elements, for example, of three basic elements. In exports approximately for forming the resonators R2S and R1P and R2S and R2P two other basic elements. Within a basic element, the resonant frequencies of parallel and serial resonator are shifted from each other that the Antiresonanzfre- lies exactly on the resonant frequency of the parallel resonator frequency of serial resonator. Here, the

Filter em passage behavior with a pass band which has a particularly low Emfugedampfung of for example 2 dB and less.

The exemplary embodiments are only examples of possible embodiments of the invention. However, the invention is not to the embodiments limited and may comprise other variations, not shown.