GB1579075A - Electronic hf switch - Google Patents

Description

(54) AN ELECTRONIC HF SWITCH (71) We. LICENTIA PATENT VER WALTUNGS G.mb.H., of 1 Theodor Stern-Kai, 6 Frankfurt/Main 70. Federal Republic of Germany, a German body corporate, do hereby declare the invention for which we pray that a patent may be granted to us. and the method by which it is to be performed. to be particularly described in and by the following statement: The invention relates to an electronic HF switch. more particularly an antenna switch.

having PIN diodes as switching elements.

This type of switch is necessary, for example. in transmitting, receiving devices for selectively connecting up the transmitting or receiving part to the antenna.

From application literature for PIN diodes. the antennae switches shown in Figs.

1 and 2 are already known - and these will be discussed in greater detail later. However these antenna switches exhibit a series of disadvantages. in particular they only permit connection of one receiver so that. in radiotelephony devices. a band interchange is not possible for the types of operation: simplex voice communication and conditional full-duplex voice communication. A further disadvantage is that here the transmitter and the receiver may be connected up simultaneously to the antenna and. at least in high transmission power. this may lead to destruction of the receiver input stage.

Moreover. with these antenna switches optimum insertion losses in the shorted state or optimum insertion losses in the nonshorted state cannot be achieved and finallv these known antenna switches have too narrow a bandwidth. i.e. because of the X/4- transformation in the arrangement according to Fig. 1 or because of the ripple in the transmission band region in the arrangement according to Fig. 2.

The invention seeks to create a switch of the type stated at the outset which facilitates selective through connection of one or more HF energy sources or one or more HF energy drains to a common switching point. whereby anv sort of time overlap of through connection of a HF energy source and a HF energy drain is avoided.

According to the invention. there is provided an electronic HF switch for connecting one or more HF energy sources or one or more HF energy drains to a common switching point comprising a controlled PIN diode switch element for each source and drain for switching through its respective source or drain. first delay means for delaying switching through of a source. a blocking circuit for blocking the drain switch elements during through connection of a source and for releasing the switch elements of the drain during blocking of all source elements. and second dealy means for delaying release of the drain switch elements.

In order to increase the blocking capacity of the switching elements of the HF energy drains with respect to high HF powers. a preferred embodiment may be obtained by shifting a resistor in the control circuit of each HF energy source from the anode side of the switching element into a circuit connection common to the circuits of all HF energy sources and drains on the cathode side of all switching elements.

A further refinement which is advantageous with high transmission powers lies in the fact that a high value resistance may be connected in parallel with each switching element in terms of direct current in order to reduce the rectified current's of blocked switching elements.

The solution in accordance with the invention has the following advantages: 1) The ability of two receiver input stages to be connected for the upper or lower band corresponding to the requirements of the types of operation: simplex voice com munication or conditional full duplex voice communication.

2) Separate connecting up of the control currents in the transmitting and in the receiving paths to the antenna while reducing the forward damping in the path between the transmitter and the antenna by dispensing with incomplete transfor mation of the non-ideal shortcircuit at the receiver input into idling at the antennae connection point by means of A/4 trans formation or by means of the transform ing low-pass filter in the arrangements according to Fig. 1 or Fig. 2.

3) The switching currents are connected by means of switching transistors. Thus the possibility opens up of tuning the time switching sequence, between the trans mitting and receiving path, with respect to each other by incorporating separate timing elements (for example RC ele ments) such that the sensitive input stages of the receivers are not damaged or des troyed.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: Figures 1 and 2 show known arrangements; Figure 3 shows a circuit arrangement generally in accordance with the invention, but without the blocking circuit required; Figure 4 shows the complete circuit in accordance with the invertion circuit, and Figure 5 shows a circuit complementary to the circuit of Figure 4 with npn instead of pnp transistors.

Figure 1 shows a known electronic antennae switch having a A/4 line. If the transmitter is through connected to an antennae connection A (or an antenna) by means of a PIN diode Grl acting as a HF switching element, then a control direct current must flow from a voltage source +U0 via PIN diode Girl, a A/4 line and a further PIN diode Gr2 so that the PIN diodes then constitute low value resistors (1f1). The X/4 line transforms the low value resistance of the diode Gr2 into a high value equivalent resistance for the transmitting branch, which is effective at the point A. In the case of reception - there is no control direct current flowing - the blocking layer capacitances of the PIN diodes are effective and the received energy may flow into the receiver almost without loss. The capacitances shown serve for direct current coupling, and the chokes serve for decoupling of the HF current. The disadvantages of this type of antennae switch have been mentioned already. When using it in the 4 m-band, for example, the length of the A/4 line becomes disadvantageous.

Another known antenna switch having a connection for a transmitter S and a receiver E is shown in Fig. 2, in which a T-arrangement built up out of discrete elements is used as a transformation element instead of a A/4 line.

Fig. 3 shows an antennae switch generally in accordance with the invention for a transmitter S and two receivers E and E', but without the circuit part for preventing simultaneous connecting up of the transmitter and one of the receivers to the antenna connection point A. In the shown position of a first switch S1 the control direct current flows through a control circuit for the switching element - a PIN diode Grl - for through connecting the transmitter S comprising a resistor R1, a first choke Drl, the PIN diode Grl and a second choke Dr3 so that in this case the transmitter S is through connected to the antennae connection A. In the other position of the first switch S1 and in the shown position of the second switch S2, one receiver E' would be connected to the antennae connection A via a Pin diode Gr2' controlled by a corresponding control circuit - comprising resistor R2', choke Dr2', Pin diode Gr2' and choke Dr3. The same is true for a further receiver E having its switching element Gr2 and a related control circuit in the position of the second switch S2 which is not shown. The three control circuits for the transmitter S and the two receivers E and E' are identically constructed in which the second choke Dr3 is a common component of all three circuits. The arrangement according to Fig. 3 facilitates operation of a transmitter/receiving device both in the manner of simplex voice communication as well as conditional full duplex voice communication.

When using this in transmitting/receiving devices, the arrangement must of course be complemented - as already mentioned - for the protection of input stages of the receivers E and E' against damage or destruction by a circuit which prevents simultaneous connection of the transmitter S and one or two receivers E and E' to the antenna connection A.

Fig. 4 shows the complete circuit arrangement in accordance with the invention. The switches S1 and S2 of the arrangement according to Fig. 3 are replaced here by three transistor switches Tl, T2 and T2'. The transmitter S is through connected to the antennae connection A by earth potential being applied to a first connection ST, whereby the control direct current is supplied by the battery + U0 via the then through connected transistor switch T1 to the control circuit of the Pin diode Grl for through connection of the transmitter. The same is true for the receivers E or E' if earth potential is applied to a further connection ET or ET' in which the control direct current from the battery + U0 flows to the control circuit of the Pin diode Gr2 or Gr2' for through connecting this receiver via the transistor switches T2 or T2'. In order to prevent the high transmission power of, for example, 10 watts from being supplied to one of the receivers E or E', a blocking circuit is provided, which comprises substantially a further transistor switch T3, a diode Gr4 or Gr4' and a further diode Gr3 or Gr3' (the diodes Gr3 and Gr3' in practice are each constituted by two diode elements connected in series and housed in a common casing), and which functions in the following manner.

When keying the transmitter, i.e. when applying the earth potential to the connection ST, the switching transistor T3 immediately becomes conductive and discharges the capacitance C9 within 1 CLsec. Thus the potential at the cathodes of the diodes Gr4 and Gr4' increases (to U0 - UF with UF forward voltage of a diode or of a conductive base-emitter diode of a transistor), whereby the two switching transistors T2 and T2' are immediately blocked since they are conductive because of the "double" diodes Gr3 or Gr3' only when the cathode potentials are low (sU0 - 3UF). Furthermore the switching transistor T1 determining through connection of the transmission branch is through connected itself after a delay in accordance with a first timing element R5 and C8 (the capacitance C8 must be charged up first of all by the resistor R5). Moreover, a second timing element R4 and C8 as well as a third timing element R7 or R7' and C9 are dimensioned so that, owing to the required high drop in pofential (from U0 - UF to UO - 3UF), it is ensured that, at the connections of the diodes Gr3 and Gr4 or Gr3' and Gr4', the transmission branch is first blocked at the end of keying of the transmitter i.e. when the connection ST is separated from each potential and only thereafter is one of the receiver branches through connected (if the related connection ET or ET' is connected at this time to earth potential).

It has proved advantageous if the resistor R1 is arranged in the control circuit for the PIN diode Grl for through connection of the transmitter instead of on the anode side of the PIN diode Grl (as shown in Fig. 3) on the cathode side in the circuit part common to the circuits of the transmitter and the two receivers as shown in Fig. 4. With the resistor R1 so positioned an uncoupling capacitance Cli is required for uncoupling the antennae connection A in terms of direct current. Of the three PIN diodes Girl, Gr2 and Gr2' only one is conductive at any one time (together with its associated transistor T1, T2 or T2') and the other two of the diodes are automatically acted upon by a negative blocking voltage by means of the voltage drop which is produced at the resistor R1 with the aid of the additional earth-connected high value resistors R8, R8' and R8" (high resistance in order to keep possible rectified currents very small).

As a result of these measures, the interchannel modulation at the antennae switch is reduced on the one hand and on the other hand the blocking capacity of the PIN diodes is improved and this facilitates use of higher transmission power.

Fig. 5 shows an antenna switch which is complementary to the arrangement according to Fig. 4 in which, instead of pnp transistors, npn transistors are used (at the same time with reversed orientation of the PIN diodes). This type of arrangement is required if through switching of the transmitter S or a receiver E or E' is not to be undertaken by applying the earth potential but with the aid of a positive potential at the related connection ST, ET or ET'.

WHAT WE CLAIM IS: 1. An electronic HF switch for connecting one or more HP energy sources or one or more HF energy drains to a common switching point comprising a controlled PIN diode switch element for each source and drain for switching through its respective source or drain, first delay means for delaying switching through of a source, a blocking circuit for blocking the drain switch elements during through connection of a source and for releasing the switch elements of the drain during blocking of all source switch elements, and a second delay means for delaying release of the drain switch elements.

2. An electrode HF switch according to claim 1, wherein, in order to increase the blocking capacity of the switching elements of the HF energy drains in respect of high HF power, and in order to reduce interchannel modulation, a resistance is inserted into a common wiring line on the cathode side of all of the switching elements, and an earthconnected high value resistor is provided on the anode side of all of the switching elements.

3. An electronic HF switch substantially as described herein with reference to Figures 4 and 5 of the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. the control circuit of the Pin diode Grl for through connection of the transmitter. The same is true for the receivers E or E' if earth potential is applied to a further connection ET or ET' in which the control direct current from the battery + U0 flows to the control circuit of the Pin diode Gr2 or Gr2' for through connecting this receiver via the transistor switches T2 or T2'. In order to prevent the high transmission power of, for example, 10 watts from being supplied to one of the receivers E or E', a blocking circuit is provided, which comprises substantially a further transistor switch T3, a diode Gr4 or Gr4' and a further diode Gr3 or Gr3' (the diodes Gr3 and Gr3' in practice are each constituted by two diode elements connected in series and housed in a common casing), and which functions in the following manner. When keying the transmitter, i.e. when applying the earth potential to the connection ST, the switching transistor T3 immediately becomes conductive and discharges the capacitance C9 within 1 CLsec. Thus the potential at the cathodes of the diodes Gr4 and Gr4' increases (to U0 - UF with UF forward voltage of a diode or of a conductive base-emitter diode of a transistor), whereby the two switching transistors T2 and T2' are immediately blocked since they are conductive because of the "double" diodes Gr3 or Gr3' only when the cathode potentials are low (sU0 - 3UF). Furthermore the switching transistor T1 determining through connection of the transmission branch is through connected itself after a delay in accordance with a first timing element R5 and C8 (the capacitance C8 must be charged up first of all by the resistor R5). Moreover, a second timing element R4 and C8 as well as a third timing element R7 or R7' and C9 are dimensioned so that, owing to the required high drop in pofential (from U0 - UF to UO - 3UF), it is ensured that, at the connections of the diodes Gr3 and Gr4 or Gr3' and Gr4', the transmission branch is first blocked at the end of keying of the transmitter i.e. when the connection ST is separated from each potential and only thereafter is one of the receiver branches through connected (if the related connection ET or ET' is connected at this time to earth potential). It has proved advantageous if the resistor R1 is arranged in the control circuit for the PIN diode Grl for through connection of the transmitter instead of on the anode side of the PIN diode Grl (as shown in Fig. 3) on the cathode side in the circuit part common to the circuits of the transmitter and the two receivers as shown in Fig. 4. With the resistor R1 so positioned an uncoupling capacitance Cli is required for uncoupling the antennae connection A in terms of direct current. Of the three PIN diodes Girl, Gr2 and Gr2' only one is conductive at any one time (together with its associated transistor T1, T2 or T2') and the other two of the diodes are automatically acted upon by a negative blocking voltage by means of the voltage drop which is produced at the resistor R1 with the aid of the additional earth-connected high value resistors R8, R8' and R8" (high resistance in order to keep possible rectified currents very small). As a result of these measures, the interchannel modulation at the antennae switch is reduced on the one hand and on the other hand the blocking capacity of the PIN diodes is improved and this facilitates use of higher transmission power. Fig. 5 shows an antenna switch which is complementary to the arrangement according to Fig. 4 in which, instead of pnp transistors, npn transistors are used (at the same time with reversed orientation of the PIN diodes). This type of arrangement is required if through switching of the transmitter S or a receiver E or E' is not to be undertaken by applying the earth potential but with the aid of a positive potential at the related connection ST, ET or ET'. WHAT WE CLAIM IS:

1. An electronic HF switch for connecting one or more HP energy sources or one or more HF energy drains to a common switching point comprising a controlled PIN diode switch element for each source and drain for switching through its respective source or drain, first delay means for delaying switching through of a source, a blocking circuit for blocking the drain switch elements during through connection of a source and for releasing the switch elements of the drain during blocking of all source switch elements, and a second delay means for delaying release of the drain switch elements.

2. An electrode HF switch according to claim 1, wherein, in order to increase the blocking capacity of the switching elements of the HF energy drains in respect of high HF power, and in order to reduce interchannel modulation, a resistance is inserted into a common wiring line on the cathode side of all of the switching elements, and an earthconnected high value resistor is provided on the anode side of all of the switching elements.

3. An electronic HF switch substantially as described herein with reference to Figures 4 and 5 of the drawings.