QwikRadio

tm

5

October 1999

MICRF003

MICRF003

Micrel

Note 1:

Sensitivity is defined as the average signal level measured at the input necessary to achieve 10e-2 Bit Error Rate (BER). The input

signal is defined as a return-to-zero (RZ) waveform with 50% average duty cycle (e.g., Manchester Encoded Data) at a data rate of

600bps. The RF input is assumed to be matched into 50

Ω.

Note 2:

Spurious reverse isolation represents the spurious components which appear on the RF input (ANT) pin measured into 50

Ω with an

input RF matching network.

Note 3:

Sensitivity, a commonly specified Receiver parameter, provides an indication of the Receiver’s input referred noise, generally input

thermal noise. However, it is possible for a more sensitive receiver to exhibit range performance no better than that of a less

sensitive receiver, if the “ether” noise is appreciably higher than the thermal noise. “Ether” noise refers to other interfering “noise”

sources, such as FM radio stations, pagers, etc.

A better indicator of achievable receiver range performance is usually given by its Selectivity, often stated as Intermediate Frequency

(IF) or Radio Frequency (RF) bandwidth, depending on receiver topology. Selectivity is a measure of the rejection by the receiver of

“ether” noise. More selective receivers will almost invariably provide better range. Only when the receiver selectivity is so high that

most of the noise on the receiver input is actually thermal will the receiver demonstrate sensitivity-limited performance.

Note 4:

Parameter scales linearly with REFOSC frequency Ft. For any REFOSC frequency other than 6.75MHz, compute new parameter

value as the ratio [(REFOSC FREQ (in MHz)) / 6.75] * [Parameter Value @ 6.75MHz]. Example: For REFOSC Freq. Ft =

7.12MHz, [Parameter Value @ 7.12MHz] = (7.12 / 6.75) * [Parameter Value @ 6.75MHz].

Note 5:

Parameter scales inversely with REFOSC frequency Ft. For any REFOSC frequency other than 6.75MHz, compute new parameter

value as the ratio [6.75 / (REFOSC FREQ (in MHz))] * [Parameter Value @ 6.75MHz]. Example: For REFOSC Freq. Ft =

7.12MHz, [Parameter Value @ 7.12MHz] = (6.75 / 7.12) * [Parameter Value @ 6.75MHz].

Note 6:

Demod filter bandwidths are related in a binary manner, so any of the other (lower) nominal filter values may be derived simply by

dividing this parameter value by 2, 4, or 8 as desired.