TRC105 Просмотр технического описания (PDF) - RF Monolithics, Inc

Номер в каталоге

Компоненты Описание

производитель

TRC105

300-510 MHz RF Transceiver

RF Monolithics, Inc 

OOK modulation is performed by switching on and off the power amplifier and its regulator. The rise and fall times

of the OOK signal can be configured in register MCFG05_PA_Ramp[7..6], which controls the charge and dis-

charge time of the regulator. Figure 4 shows the time constants set by MCFG05_PA_Ramp[7..6]. Table 2 gives

typical values of the rise and fall times as defined in Figure 4 when the capacitance connected to the output of the

regulator is 0.047 µF.

O O K M o d u la tio n W a v e fo r m s

D A TA

P ow er A m p

R e g u la to r

95%

R is e /F a ll

T im e s

2.3 Receiver

R F E n v e lo p e

60 dB

R is e /F a ll

T im e s

Figure 4

The TRC105 is set to receive mode when MCFG00_Chip_Mode[7..5] is set to 011. The receiver is based on a

double-conversion architecture. The front-end is composed of an LNA and a mixer whose gains are constant. The

mixer down-converts the RF signal to an intermediate frequency which is equal to 1/8 of the LO frequency, which

in turn is equal to 8/9 of the RF frequency. Behind this first mixer there is a variable gain IF amplifier that can be

programmed from maximum gain to 13.5 dB less in 4.5 dB steps with the MCFG01_IF_Gain[1..0] register.

After the variable gain IF amplifier, the signal is down-converted into two I and Q base-band signals by two quad-

rature mixers which are fed by reference signals at 1/8 the LO frequency. These I and Q signals are then filtered

and amplified before demodulation. The first filter is a second-order passive R-C filter whose bandwidth can be

programmed to 16 values with the register RXCFG10_LP_filt[7..4]. The second filter can be configured as either

a third-order Butterworth active filter which acts as a low-pass filter for the zero-IF FSK configuration, or as a pol-

yphase band-pass filter for the low-IF OOK configuration. To select Butterworth low-pass filter operation, bit

RXCFG12_PolyFilt_En[7] is set to 0. The bandwidth of the Butterworth filter can be programmed to 16 values

with the register RXCFG10_BW_Filt[3..0]. The low-IF configuration must be used for OOK modulation. This con-

figuration is enabled when the bit RXCFG12_PolyFilt_En[7] is set to 1. The center frequency of the polyphase

filter can be programmed to 16 values with the register RXCFG11_PolyFilt[7..4]. The bandwidth of the filter can

be programmed with the register RXCFG10_BW_Filt[3..0]. In OOK mode, the value of the low-IF is equal to the

deviation frequency defined in register MCFG02_Freq_dev. In addition to channel filtering, the function of the

polyphase filter is to reject the image. Figure 5 below shows the two configurations of the second IF filter. In the

Butterworth configuration, FCBW is the 3 dB cutoff frequency. In the polyphase band-pass configuration FOPP is the

center frequency given by RXCFG11_PolyFilt[7..4], and FCPP is the upper 3 dB bandwidth of the filter whose off-

set, referenced to FOPP, is given by RXCFG10_BW_Filt[3..0].

www.RFM.com E-mail: info@rfm.com

© 2009-2012 by RF Monolithics, Inc.

Technical support +1.800.704.6079

Page 8 of 67

TRC105 - 10/16/12

Share Link: