User Manual

PBL UHF 1 & 2 Air Interface
Maintenance Handbook
H/book Number:-60-055900HBKM
Issue No:-1
Date:-13/02/2003
Page:-25 of 25
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 50? 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
FILTER 1 483.2-483.6 MHz Passband
FILTER 2 486.2-486.6 MHz
FILTER 1 2.7 dB typical Insertion Loss
FILTER 2 2.7 dB typical
FILTER 1 483.2-483.6 MHz > 80 dB Rejection
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