Gain Measurements

1st Attempt

Procedure

The signal generator is connected to the input of the electronics box and the output is connected to the HP spectrum analyser. The output of the signal generator is varied between -85 and -3dBm at 6.426GHz and the amplitude of the resulting peak at 26MHz on the spectrum analyser is recorded. The output power is plotted against the input power and the final result is obtained by extrapolating the line to 0dBm. Measurements made near compression or the noise background are rejected if their chi-squared is greater than nine. The result is then recalculated and the selection repeated. The rejected measurements are shown in red.

It was discovered the day after that the signal generator output was offset below the displayed value. This was measured to be 18.3+/-0.4dB (YoungIm).

Results

Bpm	Gain/dB	Error/dB
QM14FFx	24.6	0.3
QM14FFy	27.2	0.3
QM12FFx	26.5	0.4
QM12FFy	28.1	0.3
QM11FFx	27.8	0.3
QM11FFy	26.6	0.3
QF9BFFx	27.2	0.3
QF9BFFy	26.0	0.3
QD8FFx	26.9	0.3
QD8FFy	26.8	0.3
QF7FFx	26.2	0.3
QF7FFy	25.9	0.3
SF5FFx	25.5	0.3
SF5FFy	27.7	0.3

2nd Attempt

Procedure

This time, the signal generator is a Hittite HMC-T2000. It's output range at 6.426GHz is -15dBm to +10dBm. To extend it's range, four attenuators are added and removed in turn between measurements. The output was measured using a spectrum analyser. The loss in the output cable was later measured using a power meter. The effect of the attenuators seemed to vary which caused the gradient of the fitted line to deviate from 1. Therefore, the data are split according to the number of attenuators and analysed separately. The average results is used for the gain.

Results

Bpm	Gain/dB	Error/dB
QM14FFx	22.1	1.4
QM14FFy	28.0	1.3
QM12FFx	24.6	1.1
QM12FFy	27.0	1.1
QM11FFx	31.8	1.1
QM11FFy	30.7	1.2

3rd Attempt

Procedure

This is similar to the second attempt except a variable attenuator with a range of 0-70dB is used in place of two of the fixed attenuators. The output power is varied by changing the attenuation and again, the output is measured with a spectrum analyser and the output cable loss, with a power meter. The analysis procedure is the same as in the first attempt.

Results

Bpm	Gain/dB	Error/dB
QM14FFx	24.4	0.2
QM14FFy	21.6	0.3
QM12FFx	24.0	0.2
QM12FFy	22.9	0.2
QM11FFx	25.6	0.2
QM11FFy	26.0	0.4

S-Band

This time, the input RF is set to 2.890GHz and again, a variable attenuator is used.

Results

Bpm	Gain/dB	Error/dB
SF1FFx	9.2	0.2
SF1FFy	2.8	0.3
SD0FFx	9.4	0.2
SD0FFy	9.8	0.2