Method of and apparatus for performing antenna cosite analysis

• US 5,875,391 A
• Filed: 07/25/1996
• Issued: 02/23/1999
• Est. Priority Date: 07/25/1996
• Status: Expired due to Term

• Current Assignee: ATC IP LLC (American Tower Corporation)
• Original Assignee: UNIsite, Inc. (American Tower Corporation)
• Inventors: Higgins, James, Mawrey, Robert S., Riley, Terence Michael
• Primary Examiner(s): Le, Thanh Cong
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US08/686,967
• Time in Patent Office: 943 Days
• Field of Search: 455/16, 455/63, 455/67.3, 455/561, 455/562, 455/501, 455/206, 455/295, 455/296, 455/306, 455/307, 455/62, 343/835, 343/853, 343/700 R, 343/702, 370/278, 375/254, 375/284, 375/285
• US Class Current: 455/295
• CPC Class Codes: H04B 17/15 Performance testing
• CPC Class Codes: H04B 17/20 of receivers

Abstract

An antenna cosite analysis system with: interactive displays for i) designing an antenna tower for placement of one or more antennas on the tower, ii) designing wireless communication circuits, and iii) relating the antennas on the tower to the wireless communication circuits; and an RF analysis system for analyzing interference between the wireless communication circuits. A process for determining intermodulation interference between transmitters and one or more receivers includes the steps of: determining a minimum susceptibility of the receivers; determining a highest order intermodulation product generated as a result of interference between the victim transmitter and each other transmitter with a power level sufficient to exceed the minimum susceptibility of the one or more receivers at the victim transmitter; and determining the intermodulation products generated as a result of interference between the victim transmitter and the other transmitters, the intermodulation products being determined up to the highest order intermodulation product of a minimum leakage transmitter-victim transmitter pair. Also disclosed is a process for determining intermodulation interference in a receiver, an apparatus for determining intermodulation interference in transmitter, and an apparatus for determining intermodulation interference in a receiver.

Claims

1. In a process for determining intermodulation interference between two or more transmitters and one or more receivers, the steps of:

a) at each transmitter, determining a minimum susceptibility to interference of the one or more receivers;

b) separately considering each transmitter as a victim transmitter paired with each other transmitter, and for each such other transmitter-victim transmitter pair, determining a highest order intermodulation product generated as a result of interference between the victim transmitter and the other transmitter with a power level sufficient to exceed the minimum susceptibility of the one or more receivers at the victim transmitter, and storing the highest order intermodulation product for each other transmitter-victim transmitter pair; and

c) separately considering each transmitter as a victim transmitter, and for each victim transmitter determining the intermodulation products generated as a result of interference between the victim transmitter and all of the at least one other transmitters, each other transmitter having a leakage power to the victim transmitter, the one of the at least one other transmitters having the lowest leakage power to the victim transmitter being the minimum leakage transmitter for that victim transmitter, the minimum leakage transmitter and the victim transmitter together constituting a minimum leakage transmitter-victim transmitter pair, the intermodulation products for each victim transmitter being determined in this step up to the highest order intermodulation product determined in step (b) for the other transmitter-victim transmitter pair that is the same as the minimum leakage transmitter-victim transmitter pair.

2. The process according to claim 1 wherein the step of determining the minimum susceptibility of the one or more receivers at each transmitter comprises the steps of:

separately considering each transmitter as victim transmitter, and determining the susceptibility of each receiver at the victim transmitter; and

determining the minimum of the susceptibilities of the one or more receivers at the victim transmitter.

3. The process according to claim 2 wherein the step of determining the susceptibility of each receiver at the victim transmitter comprises determining the coupling loss between such receiver and the victim transmitter, determining the susceptibility to interference of such receiver at the receiver, and subtracting the coupling loss between such receiver and the victim transmitter from the susceptibility to interference of such receiver at the receiver.

4. The process according to claim 3 wherein the coupling loss between each receiver and the victim transmitter is determined by summing the coupling losses, at the frequency of the receiver, between the receiver and an antenna of the receiver, between the antenna of the receiver and an antenna of the victim transmitter, and between the antenna of the victim transmitter and the victim transmitter.

5. The process according to claim 3 wherein the susceptibility to interference of the receiver is determined by the steps of:

determining a noise level at the receiver by subtracting a carrier-to-noise ratio of the receiver from a usable sensitivity of the receiver; and

determining the susceptibility of the receiver by subtracting 6 dB from the noise level at the receiver.

6. The process according to claim 1 wherein the step of determining a highest order intermodulation product generated as a result of interference between the victim transmitter and each other individual transmitter with a power level sufficient to exceed the minimum susceptibility at the victim transmitter comprises the steps of:

for each individual transmitter at each order, determining the power level P_INTatTX for such transmitter as sum of the power leakage L_T2,T1 between such transmitter and the victim transmitter and the conversion loss for the victim transmitter at such order; and

comparing the power level P_INTatTX to the minimum susceptibility at the victim transmitter.

7. The process according to claim 1 further comprising the step of storing the highest order intermodulation product for each other transmitter-victim transmitter pair in a matrix.

8. The process according to claim 7 further comprising the following step after the step of determining the intermodulation products up to the highest order intermodulation product of the minimum leakage transmitter-victim transmitter pair:

for each such intermodulation product, determining an intermodulation product frequency F_INT and an intermodulation product bandwidth BW_INT as follows;

space="preserve" listing-type="equation">F.sub.INT =±

M.sub.1 ×

F.sub.T1 ±

M.sub.2 ×

F.sub.T2 + . . . ±

M.sub.α

×

F.sub.Tα

space="preserve" listing-type="equation">BW.sub.INT =M.sub.1 ×

BW.sub.T1 +M.sub.2 ×

BW.sub.T2 + . . . +M.sub.α

×

BW.sub.Tα

where M₁,M₂, . . . , M.sub.α

! are positive integers.

9. The process according to claim 8 further comprising the following steps after the step of determining the intermodulation product frequency F_INT and intermodulation product bandwidth BW_INT :

comparing each intermodulation product frequency to the frequency band of each receiver to determine if the frequency band of any intermodulation product falls within the frequency band of any receiver;

identifying interfering intermodulation products, each with an intermodulation product frequency falling within the band of one of the receivers RX.sub.β

at frequency F_Rβ

, each interfering intermodulation product being generated by intermodulation between at least one interfering transmitter and the victim transmitter; and

determining the power of the each interfering intermodulation product at the victim transmitter P_INTatTX as follows;

space="preserve" listing-type="equation">P.sub.INTatTX =L.sub.MIN +ConversionLoss(order)

where L_MIN is the minimum leakage power of the at least one interfering transmitter at the victim transmitter.

10. The process according to claim 9 further comprising the step of, for each interfering intermodulation product, determining the intermodulation product power level P_INTatRX at receiver RX.sub.β

by summing the losses in the coupling C_T1,Rβ

between the victim transmitter and the receiver R_Xβ

;

space="preserve" listing-type="equation">P.sub.INTatRX =P.sub.INTatTX +C.sub.T1,Rβ

.

11. The process according to claim 10 further comprising the step of comparing the intermodulation product power level P_INTatRX at receiver R.sub.β

to the susceptibility of the receiver S_Rβ

to determine if interference is caused at receiver RX.sub.β

.

12. In a process for determining intermodulation interference in a receiver between two or more transmitters and the receiver, the steps of:

a) determining a minimum susceptibility to interference of the receiver;

b) for each transmitter, determining a highest order intermodulation product generated as a result of interference between the transmitter and the receiver with a power level sufficient to exceed the minimum susceptibility of the receiver, and storing the highest order intermodulation product for each transmitter; and

c) separately considering each transmitter as a victim transmitter, and for each victim transmitter determining the intermodulation products generated in the receiver as a result of interference between the victim transmitter and all of the at least one other transmitters, each other transmitter having a leakage power to the victim transmitter, the one of the at least one other transmitters having the lowest leakage power to the receiver being the minimum leakage transmitter, the intermodulation products being determined in this step up to the highest order intermodulation product of the minimum leakage transmitter determined in step (b).

13. The process according to claim 12 wherein the susceptibility to interference of the receiver is determined by the steps of:

determining a noise level at the receiver by subtracting a carrier-to-noise ratio of the receiver from a usable sensitivity of the receiver; and

determining the susceptibility at the receiver by subtracting 6 dB from the noise level at the receiver.

14. The process according to claim 12 wherein the step of determining a highest order intermodulation product generated as a result of interference between the victim transmitter and each other individual transmitter with a power level sufficient to exceed the minimum susceptibility at the receiver comprises the steps of:

for each transmitter, calculating the leakage power from the transmitter to the receiver as

space="preserve" listing-type="equation">L.sub.T1,R1 =P.sub.T1 -C.sub.T1,R1

where P_T1 is the leakage power of the transmitter and C_T1,R1 is the coupling loss between the transmitter and the receiver; and

for each transmitter at each order, determining the power level P_INTatRX for such transmitter

space="preserve" listing-type="equation">P.sub.INTatRX =L.sub.T2,R1 -(Order-1)*(InterceptPoint(order)-L.sub.T2,R1)

and comparing the power level P_INTatRx to the minimum susceptibility at the receiver.

15. The process according to claim 12 further comprising the step of storing the highest order intermodulation product for each transmitter in a matrix.

16. The process according to claim 12 further comprising the following step after the step of determining the intermodulation products generated in the receiver up to the highest order intermodulation product of the minimum leakage transmitter:

for each such intermodulation product, determining an intermodulation product frequency F_INT and an intermodulation product bandwidth BW_INT as follows;

space="preserve" listing-type="equation">F.sub.INT =±

M.sub.1 ×

F.sub.T1 ±

M.sub.2 ×

F.sub.T2 + . . . ±

M.sub.α

×

F.sub.Tα

space="preserve" listing-type="equation">BW.sub.INT =M.sub.1 ×

BW.sub.T1 +M.sub.2 ×

BW.sub.T2 + . . . +M.sub.α

×

BW.sub.Tα

where M₁,M₂, . . . , M.sub.α

! are positive integers.

17. The process according to claim 16 further comprising the following steps after the step of determining the intermodulation product frequency F_INT and intermodulation product bandwidth BW_INT :

comparing each intermodulation product frequency to the frequency band of the receiver to determine if the frequency band of any intermodulation product falls within the frequency band of the receiver, the intermodulation products with frequencies falling within the frequency band of the receiver being interfering intermodulation products; and

determining the power of each interfering intermodulation product at the victim receiver P_INTatRX as follows;

space="preserve" listing-type="equation">P.sub.INTatRX =L.sub.MIN -(Order-1)*(InterceptPoint(order)-L.sub.MIN)

where L_MIN is the minimum leakage power of the interfering transmitters at the receiver.

18. The process according to claim 17 further comprising the step of comparing the intermodulation product power level P_INTatRX at the receiver to the susceptibility of the receiver to determine if interference is caused at the receiver.

19. An apparatus for determining intermodulation interference between two or more transmitters and one or more receivers, the apparatus comprising:

means for determining a minimum susceptibility to interference of the one or more receivers at each transmitter;

means for separately considering each transmitter as a victim transmitter and for determining and storing a highest order intermodulation product generated as a result of interference between the victim transmitter and each other transmitter individually with a power level sufficient to exceed the minimum susceptibility at the victim transmitter; and

means for separately considering each transmitter as a victim transmitter and for determining the intermodulation products generated as a result of interference between the victim transmitter and all of the at least one other transmitters, each other transmitter having a leakage power to the victim transmitter, the one of the at least one other transmitters with the lowest leakage power to the victim transmitter being the minimum leakage transmitter, the intermodulation products being determined up to the highest order intermodulation product stored for the minimum leakage transmitter and victim transmitter.

20. The apparatus according to claim 19 wherein the means for determining the minimum susceptibility of the one or more receivers at each transmitter comprises:

means for separately considering each transmitter as victim transmitter and for determining the susceptibility of each receiver at the victim transmitter; and

means for determining the minimum of the susceptibilities of the one or more receivers at the victim transmitter.

21. The apparatus according to claim 20 wherein the means for determining the susceptibility of each receiver at the victim transmitter subtracts the coupling loss between such receiver and the victim transmitter from the susceptibility to interference of such receiver at the receiver to determine the susceptibility of such receiver at the victim transmitter.

22. The apparatus according to claim 21 wherein the means for determining the susceptibility of each receiver at the victim transmitter determines the coupling loss between each receiver and the victim transmitter by summing the coupling losses, at the frequency of the receiver, between the receiver and an antenna of the receiver, between the antenna of the receiver and an antenna of the victim transmitter, and between the antenna of the victim transmitter and the victim transmitter.

23. The apparatus according to claim 21 wherein the means for determining the susceptibility of each receiver at the victim transmitter determines the susceptibility to interference of the receiver by:

determining a noise level at the receiver by subtracting a carrier-to-noise ratio of the receiver from a usable sensitivity of the receiver; and

determining the susceptibility of the receiver by subtracting 6 dB from the noise level at the receiver.

24. The apparatus according to claim 19 wherein the means for determining a highest order intermodulation product generated as a result of interference between the victim transmitter and each other individual transmitter with a power level sufficient to exceed the minimum susceptibility at the victim transmitter comprises:

means determining the power level P_INTatTX for each individual transmitter at each order as the sum of the power leakage L_T2,T1 between such transmitter and the victim transmitter and the conversion loss for the victim transmitter at such order; and

means for comparing the power level P_INTatTX to the minimum susceptibility at the victim transmitter.

25. The apparatus according to claim 19 wherein the means for storing the highest order intermodulation product stores the highest order intermodulation product for each transmitter-victim transmitter pair in a matrix.

26. The apparatus according to claim 19 further comprising means for determining, after determining the intermodulation products up to the highest order intermodulation product of the minimum leakage transmitter-victim transmitter pair, for each such intermodulation product, an intermodulation product frequency F_INT and an intermodulation product bandwidth BW_INT as follows:

space="preserve" listing-type="equation">F.sub.INT =±

M.sub.1 ×

F.sub.T1 ±

M.sub.2 ×

F.sub.T2 + . . . +M.sub.α

×

F.sub.Tα

space="preserve" listing-type="equation">BW.sub.INT =M.sub.1 ×

BW.sub.T1 +M.sub.2 ×

BW.sub.T2 + . . . +M.sub.α

×

BW.sub.Tα

where M₁,M₂, . . . , M.sub.α

! are positive integers.

27. The apparatus according to claim 26 further comprising means for comparing, after determining the intermodulation product frequencies F_INT and intermodulation product bandwidths BW_INT, each intermodulation product frequency to the frequency band of each receiver to determine if the frequency band of any intermodulation product falls within the frequency band of any receiver;

means for identifying interfering intermodulation products, each with an intermodulation product frequency falling within the band of one of the one or more receivers RX.sub.β

at frequency F_Rβ

, each interfering intermodulation product being generated by intermodulation between at least one interfering transmitter and the victim transmitter; and

means for determining the power of each interfering intermodulation product at the victim transmitter P_INTatTX as follows;

space="preserve" listing-type="equation">P.sub.INTatTX =L.sub.Min +ConversionLoss(order)

where L_Min is the minimum leakage power of the interfering transmitters at the victim transmitter.

28. The apparatus according to claim 27 further comprising means for, for each interfering intermodulation product, determining the intermodulation product power level P_INTatRX at receiver RX.sub.β

by summing the losses in the coupling C_T1,Rβ

between the victim transmitter and the receiver RX.sub.β

as follows;

space="preserve" listing-type="equation">P.sub.INTatRX =P.sub.INTatTX +C.sub.T1,Rβ

.

29.

29. The apparatus according to claim 28 further comprising means for comparing the intermodulation product power level P_INTatRX at receiver R.sub.β

to the susceptibility of the receiver S_Rβ

to determine if interference is caused at receiver RX.sub.β

.

30. An apparatus for determining intermodulation interference in a receiver between two or more transmitters and the receiver, the apparatus comprising:

means for determining a minimum susceptibility to interference of the receiver;

means for determining and storing, for each transmitter, a highest order intermodulation product generated as a result of interference between the transmitter and the receiver with a power level sufficient to exceed the minimum susceptibility of the receiver; and

means for separately considering each transmitter as a victim transmitter and for determining the intermodulation products generated in the receiver as a result of interference between the victim transmitter and all of the at least one other transmitters, each other transmitter having a leakage power to the victim transmitter, the one of the at least one other transmitters having the lowest leakage power to the receiver being the minimum leakage transmitter, the intermodulation products being determined up to the highest order intermodulation product of the minimum leakage transmitter.

31. The apparatus according to claim 30 wherein the means for determining and storing the highest order intermodulation product comprises:

means for determining a noise level at the receiver by subtracting a carrier-to-noise ratio of the receiver from a usable sensitivity of the receiver; and

means for determining the susceptibility at the receiver by subtracting 6 dB from the noise level at the receiver.

32. The apparatus according to claim 30 wherein the means for determining and storing the highest order intermodulation product generated as a result of interference between the victim transmitter and each other individual transmitter with a power level sufficient to exceed the minimum susceptibility at the receiver comprises:

means for determining, for each transmitter, the leakage power from the transmitter to the receiver as

space="preserve" listing-type="equation">L.sub.T1,R1 =P.sub.T1 -C.sub.T1,R1

where P_T1 is the leakage power of the transmitter and C_T1,R1 is the coupling loss between the transmitter and the receiver; and

means for determining, for each transmitter at each order, the power level P_INTatRX for such transmitter

space="preserve" listing-type="equation">P.sub.INTatRX =L.sub.T2,R1 -(Order-1)*(InterceptPoint(order)-L.sub.T2,R1)

and for comparing the power level P_INTatRx to the minimum susceptibility at the receiver.

33. The apparatus according to claim 30 wherein the means for storing the highest order intermodulation product stores the highest order intermodulation product for each transmitter in a matrix.

34. The apparatus according to claim 30 further comprising means for determining, after determining the intermodulation products generated in the receiver up to the highest order intermodulation product of the minimum leakage transmitter, an intermodulation product frequency F_INT and an intermodulation product bandwidth BW_INT for each such intermodulation product as follows:

space="preserve" listing-type="equation">F.sub.INT =±

M.sub.1 ×

F.sub.T1 ±

M.sub.2 ×

F.sub.T2 + . . . ±

M.sub.α

×

F.sub.Tα

space="preserve" listing-type="equation">BW.sub.INT =M.sub.1 ×

BW.sub.T1 +M.sub.2 ×

BW.sub.T2 + . . . +M.sub.α

×

BW.sub.Tα

where M₁,M₂, . . . , M.sub.α

! are positive integers.

35. The apparatus according to claim 34 further comprising:

means for comparing, after determining the intermodulation product frequency F_INT and intermodulation product bandwidth BW_INT, each intermodulation product frequency to the frequency band of the receiver to determine if the frequency band of any intermodulation product falls within the frequency band of the receiver, the intermodulation products with frequencies falling within the frequency band of the receiver being interfering intermodulation products; and

means for determining the power of the each interfering intermodulation product at the victim receiver P_INTatRX as follows;

space="preserve" listing-type="equation">P.sub.INTatRX =L.sub.MIN -(Order-1)*(InterceptPoint(order)-L.sub.MIN)

where L_MIN is the minimum leakage power of the interfering transmitters at the receiver.

36. The apparatus according to claim 35 further comprising means for comparing the intermodulation product power level P_INTatRX at the receiver to the susceptibility of the receiver to determine if interference is caused at the receiver.