Backmi DA579H Users Manual
2.4GHz DSS DIGITAL CORDLESS HEADSET
MODEL : DA579 USA VERSION
Circuit Explanation
BACKMI Corporation
2.4GHz DSS DIGITAL CORDLESS HEADSET
MODEL : DA579 USA VERSION
Base Circuit Description
The signal which inputted in TEL-LINE(J701) is coupled at RL700 and RL701, this signal is passed
through Configuration switch, SW303, T300 and transformed Analog into Digital at U1.
Data which is transformed into Digital signal is mixed with PN code at U1 (by spread spectrum)
and transmitted to RF part.
Spreading signal which inputted to RF part is mixed with Carrier supplied to VCO (U903) and create
TX frequency of using channel and then is transmitted to ANTENNA through U801 by TX control of
U802.
The signal received to antenna is transmitted to U901 by RX/TX control time.
The signal inputted at U901 is mixed Carrier of VCO(U903) and got to direct conversion and create
Base band signal. And then, create I and Q signal by demodulation (QPSK : Quadrature Phase Shift
Keying method is phase- shifted by 90
I and Q signal (Two signal phase is 90
Digital signal.
Digital signal is transformed into Analog at U1.
This audio signal is passed through U42, T302, Configuration switch, RL700, RL701 and transmitted
to TEL-LINE(J701).
Hand Circuit Description
The signal which is inputted to MIC is transformed Analog into Digital at U701.
DATA which is transformed into Digital signal is mixed with PN code at U701 (by spread spectrum)
and transmitted to RF part.
Spreading signal which inputted to RF part is mixed with Carrier supplied to VCO(U903)and create
TX frequency of using channel and then is transmitted to ANTENNA through Q900, Q901
The signal received to antenna is transmitted to U901 by RX/TX control time.
The signal inputted at U901 is mixed Carrier of VCO(U903) and got to direct conversion and create
base band signal.
And then, create I and Q signal by demodulation (QPSK : Quadrature Phase Shift Keying method is
phase- shifted by 90
I and Q signal (Two signal phase is 90
generated Digital signal.
Digital signal is transformed into Analog at U701.
This audio signal is passed through receiver and transmitted.
°
)
°
).
°
) is transmitted to U1 and remixed with PN code and enerated
°
) is transmitted to U701 and remixed with PN code and
BACKMI Corporation
2.4GHz DSS DIGITAL CORDLESS HEADSET
MODEL : DA579 USA VERSION
RF Circuit Description
LO Generation : The LO signal is generated by a programmable PLL frequency synthesizer in the
U901(RF109) and the an external 2.4GHz VCO(U903). The RF109 synthesizer requires differential
input signals from the external VCO to generate the LO Frequency.
Therefore a BALUN(U905) transformer is used to generate differential signals from single-ended VCO
output.
Receive Path : The signal is received at the antenna and pass the T/R switch(U802) and an RF
bandpass filter. The output of the bandpass filter is ac-coupled to the Low Noise Amplifier (LNA) of
the U901.
The U901 downconverts the RF signal into In-phase( I) and Quadrature signal(Q) baseband signals.
The differential I and Q baseband signals are dc-coupled to the ASIC(U1 or U303) RXIP, RXIN, RXQP
and RXQN inputs.
Transmit Path
Base unit : The baseband digital data input signal is shaped by external filter (R919,C925, L901,
C924, R918) and inputted to the TXD1 Port of the U901 (RF109).
The inputted baseband digital data is mixed with Carrier supplied to VCO (U903) and transmitted to
the U801 (RF110) with a phase difference of 180 degreed between the two branch.
The inputted a differential signals to the U801 (RF110) are amplified by the U801 (RF110) And the
differential output signals of the U801 (RF110) output port are converted to a single- Ended signal at
the RF matching network.
Handset : The baseband digital data input signal is shaped by external filter (R919,C925, L901,
C924, R918) and inputted to the TXD1 Port of the U901 (RF109).
The inputted baseband digital data is mixed with Carrier supplied to VCO (U903) and transmitted to
the Q901. The inputted a single-Ended signals is amplified by the Q900, Q901
BACKMI Corporation
2.4GHz DSS DIGITAL CORDLESS HEADSET
MODEL : DA579 USA VERSION
User’s Manual
BACKMI Corporation
T
T
T
o
o
o
t
t
t
a
a
a
l
l
y
y
y
W
W
W
l
l
l
l
i
r
e
l
e
s
i
r
e
l
e
l
e
e
i
r
s
s
s
s
s
!
!
!
!
!
!
D
D
D
A
A
A
5
5
5
7
7
7
9
9
9
/////////////////////////////////////////////////////////////////////////////////////////////////////////////DA579 USER GUIDE
IMPORTANT SAFETY INSTRUCTIONS
When using your Headset equipment, basic safety precautions should always be followed to reduce the risk of fire, electric shock, and
injury to persons, including the following:
1. Read and understand all instructions.
2. Unplug this product from the wall outlet before cleaning. Do not use liquid cleaners or aerosol cleaners. Use a damp cloth for cleaning.
3. Do not use this product near water, for example, near a bathtub, washbowl, kitchen sink, or laundry tub, in a wet basement or near a
swimming pool.
4. Do not place this product on an unstable cart, stand, or table. The product may fall, causing serious damage to the product.
5. This product should be operated only from the type of power source indicated on the marking label. If you are not sure of the type of
power supply to your home, consult your dealer or local power company.
6. To reduce the risk of electric shock, do not disassemble this product, but take it to a qualified service contractor when some service or
repair work is required. Opening or removing covers may expose you to dangerous voltages or other risks. Incorrect reassembly can
cause electric shock when the appliance is subsequently used.
7. Unplug this product from the wall outlet and refer servicing to qualified service personnel under the following conditions:
A. When the power supply cord or plug is damaged or frayed.
B. If liquid has been spilled into the product.
C. If the product has been exposed to rain or water.
If the product does not operate normally by following the operating instructions, Adjust only those controls that are covered by the
operating instructions. Improper
D. Adjustments of other controls may result in damage and will often require extensive work by a qualified technician to restore the
product to normal operation.
E. If the product has been dropped or the cabinet has been damaged.
F. If the product exhibits a distinctive change in performance.
/////////////////////////////////////////////////////////////////////////////////////////////////////////////DA579 USER GUIDE
Loading...