MC13158 データシートの表示（PDF） - Motorola => Freescale

部品番号

コンポーネント説明

メーカー

MC13158

WIDEBAND FM IF SUBSYSTEM FOR DECT AND DIGITAL APPLICATIONS

Motorola => Freescale 

MC13158

Input Matching/Components

It is desirable to use a SAW filter before the mixer to

provide additional selectivity and adjacent channel rejection.

In a wideband system the primary sensitivity of the receiver

backend may be achieved before the last mixer. Bandpass

filtering in the limiting IF is costly and difficult to achieve for

bandwidths greater than 280 kHz.

The SAW filter should be selected to easily interface with

the mixer differential input impedance of approximately

2.0 kΩ in parallel with 1.0 pF. The PC board is dedicated to

the Siemens SAW filter (part number Y6970M); the part is

designed for DECT at 112 MHz 1st IF frequency. It is

designed for a load impedance of 2.0 kΩ in parallel with

2.0 pF; thus, no or little input matching is required between

the SAW filter and the mixer.

The Siemens SAW filter has an insertion loss of typically

10 dB and a 3.0 dB bandwidth of 1.0 MHz. The relatively high

insertion loss significantly contributes to the system noise

and a filter having lower insertion loss would be desirable. In

existing low loss SAW filters, the required load impedance is

50 Ω; thus, interface matching between the filter and the

mixer will be required. Figure 15 is a table of the

single–ended mixer input impedance. A careful noise

analysis is necessary to determine the secondary

contribution to system noise.

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ(M11223456505050000Hf000000000ÁÁÁÁÁÁÁÁÁÁÁÁÁz) ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ942111R(764Ω138773s139000000)ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁF–––––––––(iÁÁÁ11XÁÁÁÁÁÁÁÁÁÁ1344322Ωg194s530275u)000000000rÁÁÁÁÁÁÁÁÁÁÁÁÁe 15ÁÁÁÁÁÁÁÁÁÁÁÁÁ.(MSÁÁÁÁÁÁÁÁÁÁÁÁÁiinxgelerÁÁÁÁÁÁÁÁÁÁÁÁÁ–InenpdÁÁÁÁÁÁÁÁÁÁÁÁÁue1td88766533(R0I)Ω66798870mÁÁÁÁÁÁÁÁÁÁÁÁÁ6p50000000)0peÁÁÁÁÁÁÁÁÁÁÁÁÁdanÁÁÁÁÁÁÁÁÁÁÁÁÁceÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ–––––––––2(X11954332Ω873p681302ÁÁÁÁÁÁÁÁÁÁÁÁÁ2)006000000 ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ1(11111112Cp.........8Fp168988905ÁÁÁ)ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

System Noise Considerations

Note: the proceeding terms are defined as linear

The system block diagram in Figure 16 shows the

relationships and are related to the log form for gain and

cascaded noise stages contributing to the system noise; it

noise figure by the following:

represents the application circuit in Figure 12 and a low noise

preamp using a MRF941 transistor (see Figure 17). The

+ ń F log–1[(NF in dB) 10] and similarly

preamp is designed for a conjugately matched input and

+ ń G log–1[(Gain in dB) 10]

output at 2.0 Vdc VCE and 3.0 mAdc Ic. S–parameters at

2.0 V, 3.0 mA and 100 MHz are:

The noise figure and gain measured in dB are shown in the

S11 = 0.86, –20

system block diagram. The mixer noise figure is typically

S21 = 9.0, 164

14 dB and the SAW filter adds typically 10 dB insertion loss.

S12 = 0.02, 79

Addition of a low noise preamp having a 18 dB gain and

S22 = 0.96, –12

2.7 dB noise figure not only improves the system noise figure

The bias network sets VCE at 2.0 V and Ic at 3.0 mA for

VCC = 3.0 to 3.5 Vdc. The preamp operates with 18 dB gain

and 2.7 dB noise figure.

In the cascaded noise analysis the system noise equation

is:

+ ) ń ) ń Fsystem F1 [(F2–1) G1] [(F3–1)] [(G1)(G2)]

but it increases the reverse isolation from the local oscillator

to the antenna input at the receiver. Calculating in terms of

gain and noise factor yields the following:

+ + F1 1.86; G1 63.1

+ + F2 10; G2 0.1

+ F3 25.12

where:

F1 = the Noise Factor of the Preamp

Thus, substituting in the equation for system noise factor:

+ + Fsystem 5.82; NFsystem 7.7 dB

G1 = the Gain of the Preamp

F2 = the Noise factor of the SAW Filter

G2 = the Gain of the SAW Filter

F3 = the Noise factor of the Mixer

MOTOROLA ANALOG IC DEVICE DATA

15

Share Link: