Low loss high frequency transmitting/receiving switching module

• US 5,778,306 A
• Filed: 11/08/1996
• Issued: 07/07/1998
• Est. Priority Date: 11/08/1996
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kommrusch, Richard S.
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/745,345
• Time in Patent Office: 606 Days
• Field of Search: 333/109, 333/101, 455/73, 455/78, 455/80, 455/82, 455/83, 455/84, 455/550, 455/575, 455/129, 370/277, 370/278, 370/282
• US Class Current: 455/78
• CPC Class Codes: H04B 1/48 in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter H04B1/46 takes precedence

Abstract

A low loss high frequency transmitting/receiving switching module (100) having an input and output port (106,110), that individually may be connected to an antenna or external port (108,112) by applying an appropriate bias potential to a switching circuit (140). The switching circuit (140) is designed to operate with only a single diode (130). This is accomplished by using two, four-port 3 db directional couplers (102,104) connected with two coupling lines (114,118). The switching diode (130) is used to add or delete a transmission line (142) in one of the coupling lines (118) to proved a signal phase shift. The switching circuit (140) switches in or out a 180 degree phase shift to change the phase relationship between signals in the two sets of coupling lines (114,116,118,120) to determine which ports (106,108,110,112) of the directional couplers (102,104) are interconnected.

Claims

1. A transmitting/receiving switching module, comprising:

a first and second directional coupler, the first directional coupler having an input and output port, the second directional coupler having an antenna and external port;

a delay circuit having an electrical length of about one-half wavelength;

a first coupling line electrically connecting the couplers, a second coupling line electrically connecting the couplers, the delay circuit being switchably coupled in series with the second coupling line; and

a switching circuit including a diode, a first, second and third DC blocking capacitor, a biasing element and a RF choke, the diode is connected in a series combination with the second DC blocking capacitor, the series combination is further connected in series with the second coupling line via the first and third DC blocking capacitors, the delay circuit is connected in parallel across the series combination, the RF choke is connected at a junction of the second blocking capacitor and the diode, the biasing element is coupled to the delay circuit;

the delay circuit, when switched into a series connection with the second coupling line by the switching circuit, adding substantially one-half electrical wavelength to the second coupling line, the delay circuit, when switched out of the series connection with the second coupling line by the switching circuit, subtracting substantially one-half electrical wavelength from the second coupling line.

2. The switching module of claim 1, wherein the first coupling line has an integral number of substantially one-half wavelengths of electrical length different from an electrical length of the second coupling line.

3. The switching module of claim 1, wherein the first and second coupling lines have a substantially equal electrical length.

4. The switching module of claim 1, wherein the delay circuit is selected from the group consisting of two substantially one-quarter wavelength transmission lines and a lumped circuit having an total electrical length of about one-half wavelength.

5. The switching module of claim 1, wherein at least one of the couplers, delay circuit, switching circuit and coupling lines are disposed upon at least one ceramic substrate.

6. The switching module of claim 1, wherein at least one of the couplers, delay circuit, switching circuit and coupling lines are substantially buried within at least one ceramic substrate.

7. The switching module of claim 1, wherein the delay circuit comprises two substantially one-quarter wavelength transmission lines having a characteristic impedance of about 25 to 75 ohms.

8. The switching module of claim 1, wherein the RF choke is selecting from the group consisting of a substantially one-quarter wavelength transmission line, a substantially one-quarter wavelength transmission line coupled with a shunt capacitor, an inductor, and an inductor coupled with a shunt capacitor.

9. The switching module of claim 1, wherein the biasing element is selected from the group consisting of a transmission line, a transmission line connected coupled with a shunt capacitor, a biasing diode being connected to be forward biased when the diode is forward biased, and a biasing diode connected coupled with a shunt capacitor and being connected to be forward biased when the diode is forward biased.

10. The switching module of claim 1, wherein a cathode of the diode is connected to the RF choke, and wherein when a positive bias potential is applied to the biasing element relative to the RF choke a DC bias current flows through the biasing element, the transmission line connected to the diode, the diode, and the RF choke, the DC bias current switching the diode into a conducting state thereby switching-out the delay circuit, the first and third blocking capacitors preventing the DC bias current from leaking from the delay circuit, the second blocking capacitor preventing a secondary DC path, the DC blocking capacitors and the conducting diode providing AC coupling to the second coupling line, effectively bypassing the first and second transmission lines.

11. The switching module of claim 10, wherein the second blocking capacitor is shorted and a fourth capacitor is connected in series with the transmission line that is not connected to the diode, the fourth capacitor preventing a secondary DC path when the delay circuit is biased.

12. The switching module of claim 10, wherein:

when the diode is connected to the third blocking capacitor the first blocking capacitor is shorted and a fourth capacitor is connected in series with the transmission line that is not connected to the diode, the fourth capacitor preventing a secondary DC path when the delay circuit is biased, and

when the diode is connected to the first blocking capacitor the third blocking capacitor is shorted and a fourth capacitor is connected in series with the transmission line that is not connected to the diode, the fourth capacitor preventing a secondary DC path when the delay circuit is biased.

13. The switching module of claim 1, wherein when no bias potential is applied to the biasing element substantially minimal DC bias current flows such that the diode is in a substantially nonconducting state thereby switching-in the delay circuit, the first and third DC blocking capacitors AC coupling the first and second transmission lines in series with the second coupling line, thereby adding about a one-half electrical wavelength to the second coupling line.

14. The switching module of claim 1, wherein an anode of the diode is connected to the RF choke, and wherein when a negative bias potential is applied to the biasing element relative to the RF choke a DC bias current flows through the RF choke, the diode, the transmission line connected to the diode, and the biasing element, the DC bias current switching the diode into a conducting state thereby switching-out the delay circuit, the first and third DC blocking capacitors preventing the DC bias current from leaking from the switching circuit, the second blocking capacitor preventing a secondary DC path, the DC blocking capacitors and the conducting diode providing AC coupling to the second coupling line, effectively bypassing the first and second transmission lines.

15. The switching module of claim 1, further comprising four operating modes:

a first operating mode, wherein a signal from the input port is coupled to the antenna port, the first operating mode including the delay circuit being switched-out bypassing the delay circuit, a signal subsequently entering from the input port to the first coupler being divided by the first coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the output port, the signals being substantially equal in magnitude and about 90°

out of phase with the signal in the first coupling line leading the signal in the second coupling line by about 90°

of phase, the signals in the first and second coupling lines traveling a substantially equal electrical length to the second coupler, the signal entering the second coupler from the first coupling line leading the signal entering the second coupler from the second coupling line by about 90°

of phase such that the signals combine into a single signal coupled at the antenna port with substantially no signal present at the external port;

a second operating mode, wherein a signal from the input port is connected to the external port, the second operating mode including the delay circuit being switched-in to connect the delay circuit in a series connection with the second coupling line, a signal subsequently entering from the input port to first coupler being divided by the first coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the output port, the signals leaving the first coupler being substantially equal in magnitude and about 90°

out of phase with the signal in the first coupling line leading the signal in the second coupling line by about 90°

of phase, the signal in the second coupling line traveling about an extra one-half wavelength through the at least one transmission line than the signal in the first coupling line, the signals entering the second coupler, being effectively reversed in phase with the signal in the second coupling line leading the signal in the first coupling line by about 90°

of phase such that the signals combine into a single signal coupled at the external port with substantially no signal coming out of the antenna port;

a third operating mode, wherein a signal from the antenna port is connected to the output port, the third operating mode including the delay circuit being switched-in to connect the delay circuit in a series connection with the second coupling line, a signal subsequently entering from the antenna port to the second coupler being divided by the second coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the external port, the signals leaving the second coupler being substantially equal in magnitude and about 90°

out of phase with the signal in the second coupling line leading the signal in the first coupling line by about 90°

of phase, the signal in the second coupling line traveling about an extra one-half wavelength through the at least one transmission line than the signal in the first coupling line, the signals entering the first coupler, being substantially reversed in phase with the signal in the first coupling line now leading the signal in the second coupling line by 90°

, combine into a single signal coupled at the output port with substantially no signal coming out of the input port; and

a fourth operating mode, wherein a signal from the external port is coupled to the output port, the fourth operating mode including the delay circuit being switched-out and bypassing the delay circuit, a signal subsequently entering from the external port to the second coupler being divided by the second coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the antenna port, the signals being substantially equal in magnitude and about 90°

out of phase with the signal in the first coupling line leading the signal in the second coupling line by about 90°

of phase, the signals in the first and second coupling lines traveling a substantially equal electrical length to the first coupler, the signal entering the first coupler from the first coupling line leading the signal entering the first coupler from the second coupling line by about 90°

of phase such that the signals combine into a single signal coupled at the output port with substantially no signal present at the input port.

16. A transmitting/receiving switching module, comprising:

a first and second hybrid junction, the first hybrid junction having an input and output port, the second hybrid junction having an antenna and external port;

a delay circuit having an electrical length of about one-half wavelength;

a first coupling line electrically connecting the junctions, a second coupling line electrically connecting the junctions, the delay circuit being switchably coupled in series with the second coupling line; and

a switching circuit including a diode, a first, second and third DC blocking capacitor, a biasing element and a RF choke, the diode is connected in a series combination with the second DC blocking capacitor, the series combination is further connected in series with the second coupling line via the first and third DC blocking capacitors, the delay circuit is connected in parallel across the series combination, the RF choke is connected at a junction of the second blocking capacitor and the diode, the biasing element is coupled to the delay circuit;

the delay circuit, when switched into a series connection with the second coupling line by the switching circuit, adding substantially one-half electrical wavelength to the second coupling line, the delay circuit, when switched out of the series connection with the second coupling line by the switching circuit, subtracting substantially one-half electrical wavelength from the second coupling line.

17. A transmitting/receiving switching module, comprising:

a first and second directional coupler, the first directional coupler having an input and output port, the second directional coupler having an antenna and external port;

a first and second transmission line being connected in series, the first and second transmission lines having a total electrical length of about one-half wavelength; and

a first coupling line electrically connecting the couplers, a second coupling line electrically connecting the couplers, the first and second transmission lines being switchably coupled in series with the second coupling line;

the first and second transmission lines, when switched into a series connection with the second coupling line, adding substantially one-half electrical wavelength to the second coupling line, the first and second transmission lines, when switched out of the series connection with the second coupling line, subtracting substantially one-half electrical wavelength from the second coupling line; and

a diode, a first, second and third DC blocking capacitor, a biasing element and a RF choke, the diode being connected in a series combination with the second DC blocking capacitor, the series combination is further connected in series with the second coupling line via the first and third DC blocking capacitors, the first and second transmission lines being connected in parallel across the series combination, the RF choke being connected at a junction of the second blocking capacitor and the diode, the biasing element being connected at a junction of the first and second transmission lines.

18. The switching module of claim 17, wherein the RF choke is selecting from the group consisting of a substantially one-quarter wavelength transmission line, a substantially one-quarter wavelength transmission line with a shunt capacitor, an inductor, and an inductor with a shunt capacitor, and wherein the biasing element is selected from the group consisting of a transmission line, a transmission line connected with a shunt capacitor, a biasing diode being connected to be forward biased when the diode is forward biased, and a biasing diode connected with a shunt capacitor and being connected to be forward biased when the diode is forward biased.

19. The switching module of claim 17, further comprising a switched-out mode of the transmission lines including one of:

a cathode of the diode being connected to the RF choke and a positive bias potential being applied to the biasing element relative to the RF choke such that a DC bias current flows through the biasing element, the transmission line connected to the diode, the diode, and the RF choke, the DC bias current switching the diode into a conducting state switching-out the transmission lines from a series connection with the second coupling line, and,

an anode of the diode being connected to the RF choke and a negative bias potential being applied to the biasing element relative to the RF choke such that a DC bias current flows through the RF choke, the diode, the transmission line connected to the diode, and biasing element, the DC bias current switching the diode into a conducting state switching-out the transmission lines from a series connection with the second coupling line; and

wherein the first and third blocking capacitors prevent the DC bias current from leaking to the directional couplers, the second blocking capacitor prevent a secondary DC path, and the DC blocking capacitors and the conducting diode providing AC coupling to the second coupling line, effectively bypassing the first and second transmission lines.

20. The switching module of claim 19, wherein the second blocking capacitor is shorted and a fourth capacitor is connected in series with the transmission line that is not connected to the diode, the fourth capacitor preventing a secondary DC path when the diode is biased to conduct.

21. The switching module of claim 19, wherein:

when the diode is connected to the third blocking capacitor the first blocking capacitor is shorted and a fourth capacitor is connected in series with the transmission line that is not connected to the diode, the fourth capacitor preventing a secondary DC path when the diode is biased to conduct, and

when the diode is connected to the first blocking capacitor the third blocking capacitor is shorted and a fourth capacitor is connected in series with the transmission line that is not connected to the diode, the fourth capacitor preventing a secondary DC path when the diode is biased to conduct.

22. The switching module of claim 19, wherein at least one of the respective first and third blocking capacitors are shorted, DC signal blocking being provided outside of the switching module in at least one of the corresponding antenna and receiver.

23. The switching module of claim 17, further comprising a switched-in mode of the transmission lines wherein no bias potential is applied to the biasing element such that substantially minimal DC bias current flows such that the diode is in a substantially nonconducting state such that the first and third DC blocking capacitors AC electrically couple the first and second transmission lines in series with the second coupling line, thereby adding about a one-half electrical wavelength to the second coupling line.

24. The switching module of claim 17, further comprising four operating modes:

a first operating mode, wherein a signal from the input port is coupled to the antenna port, the first operating mode including the at least one transmission line being switched-out bypassing the at least one transmission line, a signal subsequently entering from the input port to the first coupler being divided by the first coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the output port, the signals being substantially equal in magnitude and about 90°

out of phase with the signal in the first coupling line leading the signal in the second coupling line by about 90°

of phase, the signals in the first and second coupling lines traveling a substantially equal electrical length to the second coupler, the signal entering the second coupler from the first coupling line leading the signal entering the second coupler from the second coupling line by about 90°

of phase such that the signals combine into a single signal coupled at the antenna port with substantially no signal present at the external port;

a second operating mode, wherein a signal from the input port is connected to the external port, the second operating mode including the at least one transmission line being switched-in to connect the at least one transmission line in a series connection with the second coupling line, a signal subsequently entering from the input port to first coupler being divided by the first coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the output port, the signals leaving the first coupler being substantially equal in magnitude and about 90°

out of phase with the signal in the first coupling line leading the signal in the second coupling line by about 90°

of phase, the signal in the second coupling line traveling about an extra one-half wavelength through the at least one transmission line than the signal in the first coupling line, the signals entering the second coupler, being effectively reversed in phase with the signal in the second coupling line leading the signal in the first coupling line by about 90°

of phase such that the signals combine into a single signal coupled at the external port with substantially no signal coming out of the antenna port;

a third operating mode, wherein a signal from the antenna port is connected to the output port, the third operating mode including the at least one transmission line being switched-in to connect the at least one transmission line in a series connection with the second coupling line, a signal subsequently entering from the antenna port to the second coupler being divided by the second coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the external port, the signals leaving the second coupler being substantially equal in magnitude and about 90°

out of phase with the signal in the second coupling line leading the signal in the first coupling line by about 90°

of phase, the signal in the second coupling line traveling about an extra one-half wavelength through the at least one transmission line than the signal in the first coupling line, the signals entering the first coupler, being substantially reversed in phase with the signal in the first coupling line now leading the signal in the second coupling line by 90°

, combine into a single signal coupled at the output port with substantially no signal coming out of the input port; and

a fourth operating mode, wherein a signal from the external port is coupled to the output port, the fourth operating mode including the at least one transmission line being switched-out and bypassing the at least one transmission line, a signal subsequently entering from the external port to the second coupler being divided by the second coupler to provide two signals to the first and second coupling lines with substantially no signal transmitted to the antenna port, the signals being substantially equal in magnitude and about 90°

out of phase with the signal in the first coupling line leading the signal in the second coupling line by about 90°

of phase, the signals in the first and second coupling lines traveling a substantially equal electrical length to the first coupler, the signal entering the first coupler from the first coupling line leading the signal entering the first coupler from the second coupling line by about 90°

of phase such that the signals combine into a single signal coupled at the output port with substantially no signal present at the input port.

25. A radio communication device having a switching module, the switching module comprising:

a first and second directional coupler, the first directional coupler having an input and output port, the second directional coupler having an antenna and external port;

a delay circuit having an electrical length of about one-half wavelength;

a first coupling line electrically connecting the couplers, a second coupling line electrically connecting the couplers, the delay circuit being switchably coupled in series with the second coupling line; and

a switching circuit including a diode, a first, second and third DC blocking capacitor, a biasing element and a RF choke, the diode is connected in a series combination with the second DC blocking capacitor, the series combination is further connected in series with the second coupling line via the first and third DC blocking capacitors, the delay circuit is connected in parallel across the series combination, the RF choke is connected at a junction of the second blocking capacitor and the diode, the biasing element is coupled to the delay circuit;

the delay circuit, when switched into a series connection with the second coupling line by the switching circuit, adding substantially one-half electrical wavelength to the second coupling line, the delay circuit, when switched out of the series connection with the second coupling line by the switching circuit, subtracting substantially one-half electrical wavelength from the second coupling line.