MGCT02 데이터 시트보기 (PDF) - Zarlink Semiconductor Inc

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MGCT02

Transmit Circuit for TDMA/AMPS

Zarlink Semiconductor Inc 

MGCT02

Characteristics

Value

Min. Typ. Max.

Units

Conditions

Spurious Outputs

LO Leakage

LO Leakage

Image Rejection

Other Spurii

-18

dBc Note 2, Pout = =8dBm

-14

dBm VCC = 3V, T = 25˙C Pout = +8dBm

-18

dBc Note 2, Pout = +8dBm

-20

dBm Note 3

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 MGCT02 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. VHF voltage controlled oscillator buffer and

divide by 4 prescaler

3. Active IF low pass filter

4. IF variable gain amplifier

5. Single sideband mixer with external UHF

oscillator inputs

6. RF variable gain amplifier

7. 900MHz and 1900MHz high power output driver

stages

8. 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. The oscillator drives the

quadrature modulator and an internal divide by four

circuit to reduce the frequency of the output signal to

be sent off chip to the frequency synthesiser. This

reduces the power required in the output buffer

circuit and also allows a low frequency low power

CMOS synthesiser to be used. 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.

5

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