Specifications

5.8. IMPROVEMENTS AND FURTHER WORK

The reader should be well shielded and the area of operation should

not contain switching devices in these frequency bands.

• Transponder and antenna relative orientations are critical. All transponders

should be installed in a uniform direction. When installing the readers,

it is important to consider the chosen transponder orientation and

mount the antenna accordingly. Further details can be found in Sections

5.4.4 and 5.6.2.

• Maximum read range is approximately 30cm in the presence of no

noise, with the receiver’s antenna and transponder in ideal orientations.

Deviations from this conﬁguration often result in unpredictable performance.

• The antenna can be wound to almost any size which suits the application

without signiﬁcantly aﬀecting performance, provided that the inductance

is kept constant, the receiver’s gain adjusted according to the total

number of coils and the transponder re-oriented to suit new antenna

conﬁguration.

• Low temperature co-eﬃcient capacitors should be used for tuning of

the antennae to limit the eﬀect of temperature drift on the resonant

circuit’s centre frequency.

• Reader performance can be improved by replacing the LF353 op-amps

with NE5532 low noise op-amps.

• Power consumption ultimately depends on the frequency of read requests.

5.8 Improvements and Further Work

It was not possible to implement a dual channel receiver on a single PIC

18F4620 when capturing 16 bit timer values. This microprocessor has the

ability to use independent timers for the two CCP modules. This will enable

eight bit capturing. Initial calculations indicate that the microprocessor

should be capable of capturing both channels when operating the CCP

modules in polled mode. This would enable an additional receive antenna