Karthik Chellappa of Tessolve Semiconductor Private Limited presented a method for optimizing testing of dual receiver transceivers. The document discusses challenges in testing two independent receive paths and outlines a technique using high side and low side local oscillator injection to test both channels simultaneously. Setting the local oscillator frequencies equidistant from the radio frequency and at high and low sides allows testing the receive chains in parallel, reducing overall test time by 57% compared to testing each channel independently.

1. Teradyne Users Group Conference | April 28 – 30, 2014 | Anaheim, California
TEST OPTIMIZATION FOR DUAL RX
TRANSCEIVER
Karthik Chellappa
Tessolve Semiconductor Private Limited
Bangalore, Karnataka, India
karthik.chellappa@tessolve.com

2. Dual RX Analog Signal Path
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

3. Challenge on Testing Dual RX Transceiver
 The device contains two independent RX channels and the following tests shall be carried out on
both RX paths in production.
 RX Isolation test will measure the interaction between the two paths.
 Testing the entire RX chain for the overall channel efficiency will be time consuming if they are
tested independently for each RX sub blocks at the
 Mixer
 VGA
 Filter
 ADC Output for different IF/Band Width settings
 Typically the LO is set at RF – IF (Low side Injection) while testing single RX channels as the
Image frequency will be suppressed through the Band pass filter inside the device.
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

4. Introduction to Super Heterodyne
 The multiplication of the carrier with a local oscillator is called low-side injection when
fLO<fC .
 It is called as high side injection when fLO>fC..
 A low pass filter can be selected that will block the sum frequency.
This combination of multiplier and low pass filter is called a down converter. The output
frequency fIF = |fC-fLO | is called the intermediate frequency (IF).
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

5. Three important Frequencies in Heterodyne RX
RF Radio Frequency: The center frequency the signal is broadcast on.
IF Intermediate Frequency: Fixed/Selective frequency set inside the RX. The RF signal is down
converted to this frequency.
LO Local Oscillator: Tunable frequency inside the RX used to translate the RF signal to the IF
frequency
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

6. Frequency Translation through Super Heterodyne Principle
 The super heterodyne receiver works by making use of the frequency translation properties of the
Fourier Transform
 FLO = FRF +/- FIF
 High side Injection: FLO = FRF +FIF
 Low Side Injection: FLO = FRF- FIF
 Careful positioning of the LOs at the high side and low side injection will help to test both the RX
channels efficiently and thereby saving test time and cost.
How to position the LO in High and Low Side Injection for the Dual
RX transceiver to achieve this?
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

7. Positioning the LOs
Example
Let the reference clock the LO is 19.2MHz
RF Frequency is 1618.25MHz
IF Frequency is 600 KHz
Configuration of the PLL for the LMN values and the floating point in such a way that the RF or center
frequency is equidistant to both the LO frequencies
LO1 is set with the following
LO1 will be RF-IF = 1617.65MHz
LMN = 84
Fractional word = 4237994 (2^24 x 0.25260416)
LO2 is set with the following
LO2 will be RF+IF = 1618.85MHz
LMN = 84
Fractional word = 5286570 (2^24 x 0.31510416)
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

8. Positioning the LOs – cont.
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

9. Test results
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10. Test results - cont.
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California

11. Conclusion
 The overall test time by testing both the RX channels is found to be 21.6 sec and after making the
necessary changes in the PLL settings, the overall test time to test both the RX channels in
parallel is 12.04 sec.
 The Overall test time reduction is 57.142% and the results are repeatable and correlate against
Bench and also to the test done independently for RX1 and RX2.
Teradyne Users Group Conference | April 28 – 30 | Anaheim, California