MICRF219_11 datasheet(12/23 Pages) MICREL

12 / 23 page

Micrel

MICRF219

June 2011

M9999-060811

(408) 944-0800

Application Information

Figure 4. Q

Antenna and RF Port Connections

Figure 4 shows the schematic of the Q

configured for 433.29 MHz operation. Figu

R219BPF

ation Exam

, 433.92MHz

R219B

through Figure 23 are PCB pictures. The QR21

int for the prototyping of

nna. The

nal to be

r verification. To use an antenna

such a

and solder the

whip

the PCB instead. A wire

with 167mm (6.-inch) can be used as a

tion if low cost antenna is needed.

Front-End Band Pass Filter

Components L1 and C8 form the band-pass filter at

front of the receiver. Its purpose is to attenuate

undesired outside band noise that degrades the

receiver performance. It is calculated by the parallel

resonance equation:

f = 1/(2×PI×(SQRT L1×C8))

Table 2 shows the component values for most often

L1 (nH)

Applic

ple

used frequencies.

9BPF

most

tenna

Freq (MHz)

C8 (pF)

is a good starting po

applications. Current design offers two

options: A wire antenna or 50

Ω SMA ante

SMA connection also allows an RF sig

injected for test o

s a 50

whip, remove the SMA

antenna in the hole on

of 22AWG

substitu

315.0

6.8

390.0

6.8

418.0

6.0

433.92

5.6

Table 2. Front Band-Pass Filter values for Various

Frequencies

This band-pass filter can be removed if the outside

band noise does not cause a problem. The MICRF219

has built-in image reject mixers which improve the

selectivity significantly and reject outside band noise.

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