12

µPC2533

2.2

MIX1 Block

Fig. 2-2 MIX1 Block

Note Output impedance and input impedance of Buff1 are 330

Ω and 15 kΩ, respectively.

MIX1 (Q101 to Q108) is a DBM (double balanced mixer).

MIX1 output is supplied to 10.7 MHz ceramic filter via Buff1 (output impedance: 330

Ω) for impedance matching.

The local oscillation signal is applied to the bases of Q101 to Q104, and the RF signal to the base of Q105. MIX1

(Q101 to 108) multiplies the local oscillation signal by RF signal, and converts to the resonance frequency of IFT T1

for output.

The local oscillation signal is output from pin 1 via Q109 (OSC Buff). It has an amplitude of 110 dB

µV and can

be directly input to CMOS LSI for use by the PLL synthesizer.

The RF signal applied to the base of Q105 is also input to the detector of the RF AGC circuit.

1

28

33

30

23

32

17

29

27

R11

Q109

Q105

VT

T1

VCC

R107

Q106

Q107

Q108

R108

R109

R110

R111

R112

Buff1

Q104

Q103

Q102

Q101

To RF AGC circuit (Fig. 2-4)

To 10.7 MHz

BPF

From

LPF

Note

+

31

OSC1