Abstract:
In a transceiver switchover arrangement for alternating connection of a first and a second receiver apparatus, and a first and a second transmitter apparatus, with a single antenna, the first receiver apparatus and the first transmitter apparatus are designed for a first frequency band f1, and the second receiver apparatus and the second transmitter apparatus are designed for a second frequency band f2. By means of on-off switches, in connection with two line sections, of which each represents a quarter-wave line for f2, and which serially represent a quarter-wave line for f1, one of the apparatuses is coupled to the antenna according to the mode of operation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a transceiver switchover arrangement, in particular to a two-band transceiver switchover arrangement for the alternating connection of at least one first receiver apparatus and one second receiver apparatus and at least one first transmitter apparatus and one second transmitter apparatus with a single signal coupling/decoupling means, in particular an antenna. The first receiver apparatus and the first transmitter apparatus are designed for a first frequency band f1, and the second receiver apparatus and the second transmitter apparatus are designed for a second frequency band f2, with f2≈2*f1. 
     2. Description of the Prior Art 
     Circuit arrangements of this sort are required, for example, in many telecommunication systems in order to connect a receiving apparatus with the antenna--or with another signal coupling/decoupling means--in the reception mode, and to connect a transmitter apparatus with the antenna--or with another signal coupling/decoupling means--in the transmitting mode. In particular, this type of circuit arrangement is employed with mobile transceiver apparatuses, which must satisfy two different systems, e.g. GSM and PCN. 
     From U.S. Pat. No. 5,193,218, a transceiver apparatus is known that employs a switch that connects both the transmitter and the receiver to a common antenna via quarter-wave lines. In addition, from U.S. Pat. No. 5,513,382 such a circuit is known for a radiotelephone that connects, in alternating fashion, a transmitter circuit or a receiver circuit with a common antenna by means of two diodes and a quarter-wave line. 
     The transceiver switchover arrangements must fulfill the following requirements: 
     low insertion loss in the switched-on state 
     high insulation in the switched-off state 
     high signal-harmonics ratio 
     high intermodulation resistance 
     low current consumption; no current consumption, as far as possible, in the reception mode. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a transceiver switchover arrangement of the type described above that in particular has a high intermodulation resistance. In addition, it should exhibit a low current consumption in the reception mode. 
     These objects are according to the invention in a transceiver switchover arrangement of the type initially described wherein a first on-off switching apparatus is arranged between a terminal for the first transmission apparatus and a terminal for the signal coupling/decoupling means, and wherein a second on-off switching apparatus is arranged between a terminal for the second transmitter apparatus and the terminal for the signal coupling/decoupling means. A first line section and a second line section connected serially therewith are provided between the terminal for the signal coupling/decoupling means and the terminal for the first receiver apparatus, these line sections being constructed so that each of these line sections for the second frequency band f2 respectively substantially represents a quarter-wave line, and so that the first line section, connected in series with the second line section for the first frequency band f1, substantially represents a quarter-wave line. A third on-off switching apparatus is connected between the first and the second line sections, and also is connected to a fixed potential. A fourth on-off switching apparatus is connected between the first and the second line sections, and also is connected with a terminal for the second receiver apparatus. A fifth on-off switching apparatus is connected to the terminal for the first receiver apparatus and also is connected to a fixed potential. 
     This transceiver switchover arrangement is operable in the following four operating modes: 
     a) In the operating mode &#34;Transmission in the first frequency band f1,&#34; the first and the fifth on-off switching apparatus are in the on state and the remaining on-off switching apparatuses are in the off state. The series circuit of the two line sections is thus applied to the fixed potential, preferably to ground, via the fifth on-off switching means. Since the series circuit of the two line sections represents a quarter-wave line for the first frequency band f1, the short-circuit to the fixed potential is transformed into a no-load at the terminal for the signal on-off means. Accordingly, in this operating mode, only the first transmitting direction is effectively connected with the signal coupling/decoupling means. 
     b) In the operating mode &#34;Transmission in the second frequency band f2,&#34; the second and the third on-off switching apparatuses are in the on state, and the remaining on-off switching apparatuses are in the off state. The first line section is applied to the fixed potential, preferably to ground, via the third on-off switching apparatus. Since the first line section represents a quarter-wave line for the second frequency band f2, the short circuit to the fixed potential is transformed into a no-load at the terminal for the signal coupling/decoupling means. Accordingly, in this operating mode only the second transmitting apparatus is effectively connected with the signal coupling/decoupling means. 
     c) In the operating mode &#34;Reception in the first frequency band f1,&#34; all the on-off switching apparatuses are in the off state. The terminal for the signal coupling/decoupling means is connected, in accordance with the characteristic impedance, with the first transmitting apparatus for the first frequency band f1, via the first and second line section, which are connected in series. The rest of the circuit arrangement is disconnected. 
     d) In the last of the four possible operating modes, &#34;Reception in the second frequency band f2,&#34; the fourth and the fifth on-off switching apparatus are in the on state, and the remaining on-off switching apparatuses are in the off state. The second receiver apparatus is thus connected, in accordance with the characteristic impedance, with the terminal for the signal coupling/decoupling means, via the first line section. The second line section is in turn applied to the fixed potential, preferably to ground, via the fifth on-off switching apparatus. Since the second line section for the second frequency band f2 represents a quarter-wave line, the short-circuit to the fixed potential is transformed into a no-load at the terminal for the second receive apparatus. Accordingly, in this operating mode only the second receiver apparatus is effectively connected to the signal coupling/decoupling means. 
     In a preferred embodiment, the first and the second line section are fashioned as striplines on a circuit board (PCB, multilayer board, etc.). In this way, the inventive circuit arrangement can advantageously be realized in particularly simple fashion. 
     The on-off switching apparatus are preferably switching diodes and associated current supply networks. In the on state of each on-off switching apparatus, the respectively associated switching diode is switched conductive, and is polarized (biased) in the blocking fashion in the off state. The energy consumption of the circuit arrangement is extremely low. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of a circuit diagram of the inventive transceiver switchover arrangement. 
     FIG. 2 shows circuit details of the exemplary embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, the inventive transceiver switchover arrangement has a first on-off switching apparatus SE1 connected between a terminal S1 for a first transmitting apparatus that transmits in a first frequency band f1 and a terminal A for an antenna (signal coupling/decoupling means). A second on-off switching apparatus SE2 is connected between a terminal S2, for a second transmitting apparatus transmitting in a second frequency band f2, and the terminal A for the antenna. 
     In addition, the antenna terminal A is connected with a first receiver apparatus E1 for the first frequency band f1, via a first line section SL1 and via a line section SL2, which is connected downstream from this first line section SL1, as seen from the antenna terminal A. The first and the second line sections SL1 and SL2 are fashioned so that each of these line sections SL1 and SL2 for the second frequency band f2 substantially represents a quarter-wave line, and the first line section SL1, connected in series with the second line section SL2 for the first frequency band f1, substantially represents a quarter-wave line. Ideally, the second frequency band f2 substantially represents the doubled frequency of the first frequency band f1. 
     Third and fourth on-off switching apparatuses SE3 and SE4 are connected between the first and the second line sections SL1 and SL2, and with a fixed potential P, preferably ground, or with a terminal E2 for a second receive apparatus. A fifth on-off switching apparatus SE5 is connected between the terminal E1 for the first receiver apparatus and the fixed potential P. In the table 1 below, the operating states of this transceiver switchover arrangement are summarized. 
     The concrete exemplary embodiment according to FIG. 2, according to its operating state, conforms for example to the GSM (Global System for Mobile Communications) system or to the PCN (Personal Communication Networks) system (the frequency band f2 of the PCN system has substantially double the frequency of the frequency band f1 of the GSM system). The on-off switching apparatuses SE1 to SE5 are realized by diodes D1 to D5, in particular PIN diodes, and associated power supply networks SN1 to SN5. The power supply networks SN1 to SN5, each of which has a control terminal 1 to 5 for the application of a control signal, serve to switch the diodes D1 to D5 into the &#34;conductive&#34; or &#34;blocking&#34; state. 
     In the table 2 below, the operating states of the transceiver switchover arrangement according to the exemplary embodiment are summarized. In the off state of the on-off switching apparatuses SE1 to SE5, consisting respectively of a diode D1 to D5 and a current supply network SN1 to SN5, a voltage of -15V to ground is for example applied to the control terminal 1 to 5 allocated to the respective diode D1 to D5. In the on state, a current of, for example, 10 mA (transmitting modes) or 2 mA (receiver mode in the frequency band f2) flows via the respective diodes D1 to D5. This takes place by means of the application of a voltage to the corresponding control terminals 1 to 5. 
     The current supply networks SN1 to SN5 are for example conventional current supply networks used in mobile radiotelephone technology for switching diodes, consisting of capacitors C3 to C12 and inductances L2 to L6, and thus need not be further described herein. The capacitors C1 and C2 serve for the disconnection, in terms of direct current, of the on-off switching apparatus SE3, consisting of the current supply network SN3 and the diode D3, from the line sections SL1 and SL2. The inductance L1 serves for the disconnection, in terms of radio frequency, of the ground P from the antenna terminal A and from the transmission apparatus terminals S1 and S2. 
     In place of the diodes D1 to D5 with current supply networks SN1 to SN5, transistor arrangements, for example, or other circuit arrangements can be used as on-off circuit apparatuses SE1 to SE5. Accordingly, the inventive transceiver switchover arrangement is of course not limited to the above-described exemplary embodiment. 
     The functional characteristics of the above-described two-band transceiver switchover arrangement can be further improved by means of conventional matching elements, e.g. in stripline technology or discrete LC circuits, etc., at the terminals S1, S2, E1, E2 and A. If the transceiver apparatuses are connected with the transceiver switchover arrangement via suitable filters (e.g., SAW filters, stripline filters, LC filters, etc.), the insulating and intermodulation characteristics thereof can be further improved. 
     In the inventive transceiver switchover arrangement the intermodulation is very low in the transmitting mode, since not all of the blocking switching diodes D2 to D4 or D1, D4 and D5, lie immediately in parallel with the RF power. Moreover, in the receive mode the transceiver switchover arrangement uses extremely little electrical energy, so that the power supply batteries are conserved, in particular in mobile telephones. 
     
                                           TABLE 1__________________________________________________________________________Operating State of the on-off circuit apparatus                  Explanation of manner ofmode  SE1    SE2 SE3           SE4 SE5                  functioning__________________________________________________________________________Transmission On Off Off           Off On Transmission mode for the lower-in the first           frequency first frequency band f1.frequency              The two quarter-wave lines SL1,band f1                SL2 for f2 form a quarter-wave                  line for f1 with one another (since                  f2≈2*f1). The short-circuit to                  ground P through SE5 is thereby                  transformed into a no-load at the                  antenna terminal A.Transmission off    on  on off off                  Transmission mode for thein the second          higher-frequency frequency band f2.frequency              The quarter-wave line SL1 forband f2                f2 between SE3 and the antenna                  terminal A transforms the short-                  circuit via S3 to ground P into a                  no-load at antenna terminal A.Reception in Off    Off Off           Off Off                  The receiver E1 for the firstthe first              frequency band f1 is connectedfrequency              with the antenna terminal A viaband f1                the two quarter-wave lines SL1,                  SL2, in accordance with the                  characteristic impedance.Reception in Off    Off Off           On  On The receiver E2 for the secondthe second             frequency band f2 is connectedfrequency              with the antenna terminal A viaband f2                the quarter-wave line SL1, in                  accordance with the                  characteristic impedance. The                  short circuit through S5 to ground                  P is transformed by the quarter-                  wave line for f2 into a no-load at                  the terminal E2 for the second                  receiver.__________________________________________________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________                       Remarks/measurementOperating Switching state at the control terminal:                       results (measured with anmode  1   2   3   4     5   RF power of 28 dBm)__________________________________________________________________________Transmission  10 mA     -15 V         -15 V             -15 V  10 mA                       0.5 dB insertion lossin the first                harmonic with 71 dB ratiofrequency                   IP3 at the output: 50 dBmband f1Transmission -15 V      10 mA          10 mA             -15 V -15 V                       0.5 insertion loss harmonic,in the second               with 71 dB ratiofrequencyband F2Reception in -15 V     -15 V         -15 V             -15 V -15 V                       0.5 dB insertion loss.the first                   Essentially no currentfrequency                   consumption. Only blockingband f1                     current of the diodes(GSM)                       D1 . . . D5.Reception in -15 V     -15 V         -15 V              2 mA open                       0.67 dB insertion loss. Lowthe second        (D4, D5   current consumption.frequency         conductive)band f2(PCN)__________________________________________________________________________ 
    
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.