MC13156FB View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC13156FB

Wideband FM IF System

Motorola => Freescale 

MC13156

A series LC network to ground (which is VCC) is comprised

of the inductance of the base lead of the on–chip transistor

and PC board traces and tap capacitors. Parasitic

oscillations often occur in the 200 to 800 MHz range. A small

resistor is placed in series with the base (Pin 24) to cancel the

negative resistance associated with this undesired mode of

oscillation. Since the base input impedance is so large a

small resistor in the range of 27 to 68 Ω has very little effect

on the desired Butler mode of oscillation.

The crystal parallel capacitance, Co, provides a feedback

path that is low enough in reactance at frequencies of 5th

overtone or higher to cause trouble. Co has little effect near

resonance because of the low impedance of the crystal

motional arm (Rm–Lm–Cm). As the tunable inductor which

forms the resonant tank with the tap capacitors is tuned off

the crystal resonant frequency, it may be difficult to tell if the

oscillation is under crystal control. Frequency jumps may

occur as the inductor is tuned. In order to eliminate this

behavior an inductor (Lo) is placed in parallel with the crystal.

Lo is chosen to resonant with the crystal parallel capacitance

(Co) at the desired operation frequency. The inductor

provides a feedback path at frequencies well below

resonance; however, the parallel tank network of the tap

capacitors and tunable inductor prevent oscillation at these

frequencies.

UHF Application

Figure 22 shows a 318.5 to 320 MHz receiver which drives

the mixer with an external varactor controlled (307.8 to

309.3 MHz) LC oscillator using an MPS901 (RF low power

transistor in a TO–92 plastic package; also MMBR901 is

available in a SOT–23 surface mount package). With the

50 kΩ 10 turn potentiometer this oscillator is tunable over a

range of approximately 1.5 MHz. The MMBV909L is a low

voltage varactor suitable for UHF applications; it is a dual

back–to–back varactor in a SOT–23 package. The input

matching network uses a 1:4 impedance matching

transformer (Recommended sources are Mini–Circuits and

Coilcraft).

Using the same IF ceramic filters and quadrature detector

circuit as specified in the applications circuit in Figure 17, the

12 dB SINAD performance is –95 dBm for a fmod = 1.0 kHz

sinusoidal waveform and fdev ±40 kHz.

This circuit is breadboarded using the evaluation PC board

shown in Figures 32 and 33. The RF ground is VCC and path

lengths are minimized. High quality surface mount

components were used except where specified. The

absolute values of the components used will vary with layout

placement and component parasitics.

RSSI Response

Figure 26 shows the full RSSI response in the application

circuit. The 10.7 MHz, 110 kHz wide bandpass ceramic filters

(recommended sources are TOKO part # SK107M5–AO–10X

or Murata Erie SFE10.7MHY–A) provide the correct

bandpass insertion loss to linearize the curve between the

limiter and IF portions of RSSI. Figure 25 shows that limiting

occurs at an input of –100 dBm. As shown in Figure 26, the

RSSI output linear from –100 dBm to –30 dBm.

The RSSI rise and fall times for various RF input signal

levels and R20 values are measured at Pin 20 without 10 nF

filter capacitor. A 10 kHz square wave pulses the RF input

signal on and off. Figure 27 shows that the rise and fall times

are short enough to recover greater than 10 kHz ASK data;

with a wider IF bandpass filters data rates up to 50 kHz may

be achieved. The circuit used is the application circuit in

Figure 17 with no RSSI output filter capacitor.

104 MHz

(2)

10 p

RF Input

SMA 3.0 p

Figure 20. MC13156DW Application Circuit

fRF = 104 MHz; fLO = 93.30 MHz

5th Overtone Crystal Oscillator

33

(4)

0.135 µH

+1.0 µ

120 p

1

(1)

0.1 µ

2

10 n

3

To Filter

Mixer

27 p

24

1.0 µH

(3)

30 p

23

4.7 k 5th OT

XTAL

VEE 22

10 n

VCC

NOTES: 1. 0.1 µH Variable Shielded Inductor: Coilcraft part # M1283–A or equivalent.

2. Capacitors are Silver Mica.

3. 5th Overtone, Series Resonant, 25 PPM Crystal at 93.300 MHz.

4. 0.135 µH Variable Shielded Inductor: Coilcraft part # 146–05J08S or equivalent.

MOTOROLA WIRELESS SEMICONDUCTOR

13

SOLUTIONS – RF AND IF DEVICE DATA

Share Link: