MGCT02
Value
Characteristics
Min.
Spurious Outputs
LO Leakage
LO Leakage
Image Rejection
Other Spurii
-18
-14
-18
-20
dBc
dBm
dBc
dBm
Note 2, Pout = =8dBm
V
CC
= 3V, T = 25˙C Pout = +8dBm
Note 2, Pout = +8dBm
Note 3
Typ.
Max.
Units
Conditions
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
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.
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
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
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
