A detailed block diagram is shown in Figure 1.

The input section has:

• RF digital signal generator;
• bandpass filter;
• isolator;
• directional coupler; and
• RF power sensor.

The output section has:

• RF load attenuator;
• directional coupler;
• RF power sensor;
• spectrum analyzer; and
• vector signal analyzer.

It is important that the dual-channel RF power meter and sensors be zeroed and calibrated and set to the correct operating frequency before any measurements take place.

Then, a bench calibration is performed, to determine the input and output insertion losses, entered as offsets into the power meter. Hence, channel 1 (assigned to the input) measures exactly the input RF power and channel 2 (assigned to the output) measures the output power. The gain of the device in dB is determined immediately by taking the difference of these readings in dBm.

The Vramp control signal is generated by the arbitrary function generator. In order to maintain a bounded spectrum during RF power increase or decrease, a gradual change is required on Vramp. This is usually implemented with a ¼ period sin²(x) or sin³(x) function applied to the rising edge. In similar fashion a ¼ period cos²(x) or cos³(x) is applied to the falling edge. In general, the cubic function will provide a gentler rise and fall than the square function, however, the latter has a faster time response.

A proper ramping profile can be generated by considering the following:

• The maximum amplitude (typically 2 V to 2.5 V).

• The pulse duration is 577 µs for one active slot (i.e., slot 0) and 12.5% duty cycle.

• The repetition rate is 4615 µs or approximately 217 Hz.

• The rise and fall times of the pulse are such, that they conform with Annex B in^[2].

• In general, more than one ramping profile is required to satisfy^[2] over RF power output, battery voltage and temperature.

As a starting point, rise and fall times of the ramp can be approximated to those in annex B^[2], that is approximately 14 µs to 16 µs and same time frame rate of 4615 µs.

To communicate with the ArbFuncGen a GPIB/IEEE 488.2 controller card (available, for example, from National Instruments or equivalent) and GPIB control software (such as NI 488.2) installed in the PC is needed. Then install the waveform creation software (such as Tektronix AXW-100 for model AFG-310 function generator or an Agilent 34811A for model HP 33120A function generator). Interconnecting GPIB cables are required between the computer and function generator.

In developing the Vramp profiles, it is useful to have an oscilloscope connected to the output of the arbitrary function generator. Final verification can be made in the RF output power with a spectrum analyzer in the zero-span (time domain) mode.

A typical display of the frequency spectrum as obtained by the spectrum analyzer with a GSM/EDGE personality is shown in Figure 2 (GMSK at 824 MHz) and Figure 3 (EDGE at 1910 MHz).

Required test equipment includes:

• RF digital signal generator GMSK and EDGE modulation capable in the bands of interest;

• spectrum analyzer with GSM personality;

• vector signal analyzer with GSM personality;

• printer for the above units, if required;

• RF power meter, dual channel with sensors calibrated to the band of interest;

• arbitrary function generator, for Vramp generation;

• oscilloscope, four channels with 10x voltage probes and 1x current probes;

• directional couplers, 10 dB coupling (input) and 20 dB coupling (output);

• bandpass filter and isolator for the bands of interest;

• load attenuator 20 dB, 5 W;

• dc power supplies, regulated 0 to 5 V_dc, 2 A output (two);

• DVM for accurate voltage measurements (two); and interconnecting RF and dc cables.

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