Handbook

PBL UHF1/1A 1 & 2 Air Interface
Maintenance Handbook
H/book Number:-60-055900HBKM
Issue No:-2
Date:-20/10/2003
Page:-
30 of 85
5. SUB-UNIT MODULES
5.1 UHF 1 Air Interface (60-055901)
5.1.1 Bandpass Duplexers (02-013401)
5.1.1.1 Description
The bandpass filters are multi-section designs with a bandwidth dependent upon the
passband frequencies, (both tuned to customer requirements). The response shape is
basically Chebyshev with a passband design ripple of 0.1dB. The filters are of combline
design, and are carefully aligned during manufacture in order to optimise the insertion loss,
VSWR and intermodulation characteristics of the unit. The tuned elements are silver-plated
to reduce surface ohmic losses and maintain a good VSWR figure and 50Ω load at the input
and output ports. Note that the same filter is used for both UHF 1 & 2, but tuned differently
depending on the required frequencies and bandwidth for each air interface.
Being passive devices, the bandpass filters should have an extremely long operational life
and require no maintenance. Should a filter be suspect, it is usually most time efficient to
replace the module rather than attempt repair or re-tuning.
No adjustments should be attempted without full network sweep analysis facilities to
monitor both insertion loss and VSWR simultaneously.
5.1.1.2 Technical Specification
PARAMETER SPECIFICATION
FILTER 1 483.2-483.6 MHzPassband:
FILTER 2 486.2-486.6 MHz
FILTER 1 2.7 dB typicalInsertion Loss:
FILTER 2 2.7 dB typical
FILTER 1 483.2-483.6 MHz > 80 dBRejection:
FILTER 2 486.2-486.6 MHz > 80 dB
Power Rating: 250 Watt
Impedance: 50 ohm
VSWR: Better than 1.2:1
Connectors: SMA female