Harmonic suppression in dual band mobile phones

• US 6,400,963 B1
• Filed: 05/21/1999
• Issued: 06/04/2002
• Est. Priority Date: 05/22/1998
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Johansson, Paul, Herold, Alexander, Glöckler, Roman
• Primary Examiner(s): MAUNG, NAY AUNG
• Application Number:
  US09/316,134
• Time in Patent Office: 1,110 Days
• Field of Search: 455/78, 455/80, 455/82, 455/83, 455/552, 455/553, 455/562, 333/101, 333/103, 333/104, 333/105
• US Class Current: 455/553.1
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• 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

To effectively suppress harmonics in a dual band mobile phone with a power amplifier (10) outputting transmitting signals for different frequency bands (GSM; PCS, DCS) via a single output as described a power amplifier output circuit in which harmonics are filtered through impedance transformation of a turn-off impedance of a transmitter/receiver change over unit (36, 38). Hereby the desired filtering of harmonics may be achieved without almost no additional expenditure.

Claims

1. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively, and

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band.

2. Power amplifier output circuit according to claim 1, wherein the impedance transformation unit (48) is provided as first (λ

/4+n*λ

/2, n=0, 1, . . . ) line (64) being tuned to the double center frequency (2*f1) of the first frequency band.

3. Power amplifier output circuit according to claim 1, wherein the impedance transformation unit (48) is implemented with discrete circuit components such that at the input thereof the impedance for this double center frequency (2*f1) of the first frequency band is a short circuit.

4. Power amplifier output circuit according to claim 1, wherein the second transmitter/receiver change over unit (36, 38) comprises a third switching unit (38) activated in the transmitting mode and a fourth switching unit activated in the receiving mode.

5. Power amplifier output circuit according to claim 1, wherein there is provided a first impedance matching circuit (14) between the power amplifier (10) and the change over unit (16, 28).

6. Power amplifier output circuit according to claim 1, wherein a second impedance matching circuit (18) is provided between the first switching unit (16) and the first transmitter/receiver change over unit (24, 26).

7. Power amplifier output circuit according to claim 1, wherein a third impedance matching circuit (30) is provided between the second switching unit (28) and the second transmitter/receiver change over unit (36, 38).

8. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band, and

e) the change over unit (16, 28) is provided with a first change over unit (16) connected between the output of the power amplifier (10) and the first transmitter/receiver change over unit (24, 26) and a second change over unit (28) connected between the output of the power amplifier (10) and the second transmitter/receiver change over unit (36, 38).

9. Power amplifier output circuit according to claim 8, wherein the impedance transformation unit (48) is provided as first (λ

/4+n*λ

/2, n=0, 1, . . . ) line (64) being tuned to the double center frequency (2*f1) of the first frequency band.

10. Power amplifier output circuit according to claim 8, wherein the impedance transformation unit (48) is implemented with discrete circuit components such that at the input thereof the impedance for this double center frequency (2*f1) of the first frequency band is a short circuit.

11. Power amplifier output circuit according to claim 8, wherein the second transmitter/receiver change over unit (36, 38) comprises a third switching unit (38) activated in the transmitting mode and a fourth switching unit activated in the receiving mode.

12. Power amplifier output circuit according to claim 8, wherein there is provided a first impedance matching circuit (14) between the power amplifier (10) and the change over unit (16, 28).

13. Power amplifier output circuit according to claim 8, wherein a second impedance matching circuit (18) is provided between the first switching unit (16) and the first transmitter/receiver change over unit (24, 26).

14. Power amplifier output circuit according to claim 8, therein a third impedance matching circuit (30) is provided between the second switching unit (28) and the second transmitter/receiver change over unit (36, 38).

15. Power amplifier output circuit according to claim 11, wherein the first switching unit (16), the second switching unit (28), and/or the third switching unit (36), respectively, are provided as first diode of the PIN type (50), second diode of the PIN type (52), and/or third diode of the PIN type (66), respectively.

16. Power amplifier output circuit according to claim 14, wherein the third switching unit (36) is bridged with a series circuit comprising an inductivity (70) and a capacitor (72).

18. Power amplifier output circuit according to claim 11, wherein the switchable notch filter (74) comprises a capacitor (76) connected to ground via a fourth diode of the PIN type (78).

17. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band,

e) the second transmitter/receiver change over unit (36, 38) comprises a third switching unit (38) activated in the transmitting mode and a fourth switching unit activated in the receiving mode, and

f) there is provided a switchable notch filter (74) between the third switching unit (36) and the antenna (42) of the mobile radio unit.

19. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band, and

e) upstream the antenna (42) of the mobile radio unit there is provided a low pass filter (32) the cutoff frequency of which is determined through a second frequency band.

20. Power amplifier output circuit for a dual band mobile radio unit;

comprising;

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band, and

e) there is provided a first impedance matching circuit (14) between the power amplifier (10) and the change over unit (16, 28), and further

f) a second impedance matching circuit (18) between the first switching unit (16) and the first transmitter/receiver change over unit (24, 26), and a third impedance matching circuit (30) is provided between the second switching unit (28) and the second transmitter/receiver change over unit (36, 38), such that

g) each of the first impedance matching circuit (14), the second impedance matching circuit (18) and/or the third impedance matching circuit (30) is provided as line/coil in series configuration and capacitor (54, 60, 62) branching off to ground.

21. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmitter/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band,

e) the second transmitter/receiver change over unit (36, 38) comprises a third switching unit (38) activated in the transmitting mode and a fourth switching unit activated in the receiving mode, and

f) as fourth switching unit (38) there is provided a second (λ

/4+n*λ

/2, n=0, 1, . . . ) line (80) lying in the line to carry the second receiving signal such that at the end leading away from the antenna a fifth diode of the PIN type (82) branches off to ground.

22. Power amplifier output circuit according to claim 21, wherein the second (λ

/4+n*λ

/2, n=0, 1, . . . ) line (80) is realized with at least one microstrip section and/or at least one strip line section in at least one circuit substrate layer.

23. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tuned to harmonics of the center frequency (f1) of the first frequency band,

e) the impedance transformation unit (48) is provided as first (λ

/4+n*λ

/2, n=0, 1, . . . ) line (64) being tuned to the double center frequency (2*f1) of the first frequency band, such that the first (λ

/4+n*λ

/2, n=0, 1, . . . ) line (64) is realized with at least one microstrip section and/or at least one strip section in at least one circuit substrate layer.

24. Power amplifier output circuit for a dual band mobile radio unit, comprising:

a) a first transmitter/receiver change over unit (24, 26) to transmit/receive a first transmitting/receiving signal in a first frequency band via an antenna (42) of the mobile radio unit,

b) a second transmitter/receiver change over unit (36, 38) to transmit/receive a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna (42) of the mobile radio unit, wherein

c) a change over unit (16, 28) having a first switching unit (16) and a second switching unit (28) and selectively connecting a power amplifier (10) to amplify the transmitting signals with the first and second transmitter/receiver change over unit, respectively,

d) an impedance transformation unit (48) is provided to transform a turn off impedance of the second transmitter/receiver change over unit (36, 38) during the transmission of the first transmitting signal to a band stop characteristic tune to harmonics of the center frequency (f1) of the first frequency band, and

e) the first transmitter/receiver change over unit (22) is provided with a fifth switching unit (26) activated in the receiving mode.

25. Power amplifier output circuit according to claim 24, wherein there is provided a diplexer (40) to couple the antenna to the power amplifier output circuit such that its input terminals are connected to a first center tap between the third switching unit (36) and the fourth switching unit (38) and a second center tap between the fifth switching unit (24) and the sixth switching unit (26).

26. Method to operate a power amplifier output circuit for a dual band mobile radio unit, comprising the steps:

a) transmitting/receiving a first transmitting/receiving signal in a first frequency band via an antenna of the mobile radio unit and a first transmitter/receiver change over unit (24, 26),

b) transmitting/receiving a second transmitting/receiving signal in a second frequency band above the first frequency band via the antenna of the mobile radio unit and a second transmitter/receiver change over unit (24, 26;

36, 38), respectively, and

c) selectively connecting an output of a power amplifier (10) for amplifying the transmitting signals with the first and second transmitter/receiver change over unit (24, 26;

36, 38), respectively, and

d) filtering the first harmonic of the first transmitting signal in the transmission branch for the second transmitting/receiving signal with a band stop when transmitting the first transmitting signal.

27. Method to operate a power amplifier output circuit according to claim 26, wherein harmonics of the first transmitting signals above the center frequency (f2) of the second frequency band are filtered in the transmission branch of the second transmission/receiving signal with a low pass filter (32) when sending the first transmitting signal.

28. Method to operate a power amplifier output circuit according to claim 26, wherein a band stop is realized in the second transmission branch through transforming the turn-off impedance of the second transmitter/receiver change over unit (36, 38) into an open circuit impedance for the first harmonic of the center frequency f1 of the first frequency band.

29. Method to operate a power amplifier output circuit according to claim 27, wherein a band stop is realized in the second transmission branch through transforming the turn-off impedance of the second transmitter/receiver change over unit (36, 38) into an open circuit impedance for the first harmonic of the center frequency f1 of the first frequency band.

30. Method to operate a power amplifier circuit according to claim 26, wherein the first harmonic of the first transmitting signal is additionally filtered in the transmission branch (42) transmitting/receiving signal with a switchable notch filter (74) when sending the first transmitting signal.

31. Method to operate a power amplifier circuit according to claim 27, wherein the first harmonic of the first transmitting signal is additionally filtered in the transmission branch (42) transmitting/receiving signal with a switchable notch filter (74) when sending the first transmitting signal.

32. Method to operate a power amplifier circuit according to claim 28, wherein the first harmonic of the first transmitting signal is additionally filtered in the transmission branch (42) transmitting/receiving signal with a switchable notch filter (74) when sending the first transmitting signal.