MGCT03

5

Spurious Outputs

LO Leakage

-18

dBc

Note 2, Pout = =8dBm

LO Leakage

-14

dBm

Image Rejection

-18

dBc

Note 2, Pout = +8dBm

Other Spurii

-20

dBm

Note 3

Characteristics

Value

Units

Conditions

Min.

Typ.

Max.

Table 3 - AC Characteristics (continued)

Notes:

1. V (I/Q) = 1.4V differential, VHF LO = 22mV rms, UHF LO = -15dBm, VGA = 2.6volts

2. V (I/Q) = 1.4 V dc differential, VHF LO = 22mV rms, UHF LO = -15dBm

3. Frequency range 10MHz to 10*ftx except Rx and Tx bands

Circuit Description

General

The MGCT03 circuit is designed to provide the

transmit function in dual band dual mode IS136/

AMPS mobile phones. The circuit contains the

following blocks:

1. Quadrature modulator

2. Active IF low pass filter

3. IF variable gain amplifier

4. Single sideband mixer with external UHF

oscillator inputs

5. RF variable gain amplifier

6. 900MHz and 1900MHz high power output driver

stages

7. Power and mode control logic

Quadrature Modulator

I and Q data from a baseband circuit such as the

Zarlink Semiconductor MGCM01 or MGCM02 circuit

is applied to the I and Q inputs of the quadrature

modulator to produce the intermediate frequency by

mixing with the local oscillator frequency from the

VHF VCO. The control inputs can select either a

divide by two or divide by four function between the

VHF VCO and the quadrature modulator giving a

choice of possible intermediate frequencies.

VHF Oscillator Input Oscillator Bias and

Divider

An external VHF oscillator circuit is AC coupled to

the VHF oscillator input to drive the quadrature

modulator. An oscillator bias circuit is included on

the chip so that the external VHF oscillator transistor

can be switched off using the control inputs. The bias

voltage is switched off in either of the sieep

conditions shown in Tables 4 and 5.

Active Low Pass Filter

The output from the quadrature modulator is passed

to the active low pass filter which attenuates wide

band noise and spurious outputs.