Basic RF Technic and Manual

Dr. Haim Matzner&Shimshon Levy

April 2002 2 CONTENTS

I Experiment-4 Power Meter and Power Measurement 5

1Introduction 7 1.1 Prelab Exercise ...... 7 1.2BackgroundTheory...... 7 1.3dBanddBmTerminology...... 7 1.4FundamentalsofRFPowerMeasurement...... 8 1.5MicrowavePowerMeter-HP-E4418...... 9 1.5.1 TheoryofOperation...... 9 1.6TypesofPowerMeasurements...... 10 1.7AverageandInstantenousPower...... 10 1.8PowerofModulatedSinusoidalSignal...... 11 1.9PulsePower...... 12 1.10PowerSensingMethod...... 13 1.10.1 as a of Power meter...... 13 1.10.2DiodeasaSensorofPowerMeter...... 14 1.10.3DirectionalPowerSensor...... 16

2 Experiment Procedure 17 2.1RequiredEquipment...... 17 2.2TurningOnthePowerMeter...... 17 2.3 Front Panel Tour ...... 17 2.4PowerMeterOperation...... 19 2.4.1 ZeroingthePowerMeter...... 19 2.4.2 CalibratingthePowerMeter...... 19 2.5 Average Power ...... 20 2.6 PowerofaModulatedSinusoidalSignal...... 21 2.7PulsePower...... 21 2.8 Detector ...... 22 2.9FinalReport...... 23 2.10Appendix-1...... 23 2.10.1Tophaselocktwofunctiongenerator...... 23 2.10.2Settingazerophasereferenceattheendofthecable...... 24 4 CONTENTS Part I Experiment-4 Power Meter and Power Measurement

5

Chapter 1 INTRODUCTION

1.1 Prelab Exercise 1. Define average power, Instantaneous power, PEP, thermocouple principle, square law region of diode. 2. Describe how you intend to measure incident and reflected power using directional coupler.

1.2 Background Theory At low , the strength of the signal is calculated by measuring the or current. Voltage and current are related by ’s law (current= voltage impedance), and power defined as the product of voltage and current. At microwave÷ frequencies theequivalentstovoltageiselectricfield, and magnetic field to current. It is not an easy task to measure accurately magnetic and electric fields. Power is the quantity that is measured and the magnetic and electric fields are derived from the measured power. Power is the of the electromagnetic wave, and is measured in units of watts, which related to mechanics units as watt (W)=1joule/sec. At microwave frequencies, the reference level of power is not 1 W,but1mW . The reason is that a milliwatts of power is enough to operate microwave devices and components, and even wireless products. Techniques for power measurements depend on . Below 100kHz, voltage and current are practically measured. At frequencies of tens hundreds of MHz, power measurement is more accurate then the power calculated by measuring voltage and current. Above 1GHz, power measurement is dominant and current and voltage measurements are not practical.

1.3 dB and dBm Terminology If we look at table one, we see that all the zeroes, before the decimal point for high powers ( more than 1watt), and the zeroes for low powers make the calculation cumbersome. For convenience and the cases we perform relative power measurement, for example, to compare the output power coming out of amplifier, relative to that going into it. the dB system of units is used and expressed as : 8 Introduction

P P [dB]=10log10( ) (1.1) Pref The dB number system can also be used to express absolute value of microwave power as dBm and defined as: P P [dBm] =10log ( ) (1.2) 10 1mW Watts dBm designation 1,000,000 90 1megawatt 1,000 50 1kilowatt 1 30 1watt 0.001 0 1 milliwatt 0.000,001 -30 1microwatt 0.000,000,001 -60 1nanowatt 0.000,000,000,001 -90 1picowatt 0.000,000,000,000,001 -120 1 femtowatt Table-1 Prefix used to specify microwave power

1.4 Fundamentals of RF Power Measurement The measurement of power in RF and microwave applications has the same signif- icance as voltage measurements in . Power meters are used for a wide variety of measurement tasks. In comparison with spectrum or network analyzers, they are relatively cheap and unsophisticated instruments. The development of carrier-based at the beginning of this century derived a parallel development in the field of power measurements. The ma- jority of methods were based on converting electrical energy into heat(Thermistor and thermocouple devices). For a long time, this was the only way of making ac- curate measurements at practically any frequency. In the meantime, direct voltage and current measurements can be made up into the GHz range assuming matched system without having to convert electrical energy into heat. Nevertheless, the in- tensity of RF and microwave signals is still given in terms of power. Apart from the high accuracy of thermal power meters, there are other important reasons for using power. Any signal transmission by waves, for example sound propagation, involves thetransferofenergy.Onlytherateofenergyflow, power, is an absolute measure of waveintensity.IntheRFandmicrowaveranges,thewavepropertiesoftheelectro- magnetic field play an important role because the dimensions of the lines used are of the same order of magnitude as the wavelength used. This fact has to be taken into account when the quantity to be measured . Voltage and current are less appropri- ate because they depend on the physical characteristics of the transmission medium (dimensions, dielectric constant, permeability) and field strength. Consider, for ex- ample, two matched coaxial cables with characteristic impedance of 50Ω and 75Ω. -HP-E4418 9

Diode Sensor Power Meter

RF Input Matching Signal BPF cocditioni ADC Network ng EE PROM Chopper DSP Sensor driver

Micro Calibrator Display Bus Processor

Figure 1 Block diagram of Power Meter with Diode Sensor

For the same transmitted power, the voltage and current for the two impedance differ by a factor of 1.22. here are further reasons for selecting power as the quantity to be measured. There is no direct way of measuring voltage and current in waveguides, and when standing waves occur, there are large measurement errors.

1.5 Microwave Power Meter -HP-E4418 1.5.1 Theory of Operation Digital signal processing and microwave semiconductor have now advanced to the point where dramatically-improved performance and capabilities are available for diode power sensing and metering power are now capable of measuring overawidedynamic-70to+20dBm,rangeof90dB.Thispermitsthenewsensors to be used for CW applications which previously required two sensors. The new HP ECP-E18A power sensor features a frequency range 10 MHz to 18 GHz. A simplified block-diagram of the sensor is shown in Figure-1 . The front end construction is combines the matching input pad ( low value Attenuator), , FET choppers, integrated RF filter , a driving pre-amplifier. All of those components operate at such low levels that it was necessary to integrate them into a single thermal space on a surface-mount-technology PC board. To achieve the expanded dynamic range of 90-dB, the sensor/meter architecture depends on a data compensation algorithm, which is calibrated and stored in an individual EEPROM in each sensor. The data algorithm stores information of three parameters, input power level versus frequency versus temperature for the range 10 MHz to 18 and - 70 to +20 dBm and 0 to 55 ◦C. At the time of sensor power-up, the power meter interrogates the attached sensor, using an industry-standard serial bus format, and in turn, receives the upload of sensor calibration data. An internal temperature sensor supplies the diode’s temperature data for the temperature-compensation algorithm in the power meter. The new sensor store cal-factor tables for two different input power levels to 10 Introduction

Average Power θ Amplitude

t Voltage Power Current

Amplitude of sinusoidal power (solid line), voltage (dashed line), current (dash- dotted line), and average power (dotted line) as function of time. θ is the phase difference between current and voltage.

Figure 2 Average and Instantenous power improve accuracy of the correction routines. Figure -1 shows a simplified schematic of the HP EPM-4418A meter. The pre-amplified sensor output signal receives some early amplification, followed by some signal conditioning and filtering. The signal is then applied to a dual ADC. A serial output from the ADC takes the sampled signals to the digital signal processor, which is controlled by the main microprocessor. A differential drive signal, synchronized to the ADC sampling clock, is output to the sensor for its chopping function.The ADC provides a 20-bit data stream to the digital signal processor, which is under control of the main microprocessor. Even the syn- chronous detection is performed by the ADC and DSP rather than use of a traditional synchronous detector. Experiment-3 Power Meter and Power Measurement

1.6 Types of Power Measurements The main types of power measurements are: average power, pulse power and peak envelope power. The first is suitable for energy transfer considerations, the second type deals with square shape power pulses as function of time, and the last with a more complicated shapes of power as function of time. The pulse power measurement gives us also peak power values, which is an important information in many cases. In order to have a peak envelope power measurement, a relatively great number of single power measurements is performed, such that the needed details of the power as function of time are seen.

1.7 Average and Instantenous Power Power is usually defined as the rate of transfer or absorption of energy per unit time. The power transmitted across a system is the product of the instantaneous values of current and voltage at that system(see Fig-2). Power of Modulated Sinusoidal Signal 11

Let the Voltage be

v(t)=Vm cos(wt + θv) and the current i(t)=Im cos(wt + θi) Then the power will be

p(t)=v(t)i(t)=Vm cos(wt + θv)Im cos(wt + θi) 1 by using the trigonometric identity cos θ1 cos θ2 = 2 [cos(θ1 θ2)+cos(θ1 + θ2)] we get − VmIm VmIm p(t)= cos(θv θi)+ cos(2wt + θv + θi) 2 − 2 by using the trigonometric identity cos(θ1 + θ2)=cosθ1 cos θ2 sin θ1 sin θ2 we get −

VmIm p(t)= cos(θv θi)+ (1.3) 2 − VmIm VmIm + cos(θv + θi)cos2wt sin(θv + θi)sin2wt 2 − 2 the following points can be made concerning equation-6.3 and Fig.-2 VmIm 1.Theaveragevalueofthepower(ortheDCcomponent)isgivenby cos(θv 2 − θi) and has maximum when the phase difference between current and voltage equal zero. 2. The frequency of the instantenous power is twice the frequency of voltage or current. 3. If the phase difference between voltage and current is +π/2,thecircuit is purely inductive and the average power will be zero ,power will oscillate between source and inductor. 4. If the phase difference between voltage and current is -π/2, the circuit is purely cacitive and the average power will be zero ,power will oscillate between source and .

1.8 Power of Modulated Sinusoidal Signal When modulated sinusoidal signals are applied, other definitions of power are more appropriate to the system (Fig-3). The average of P over the period is called the average power Pavg. This is what a thermal power meter would indicate. The power averaged over one period of a carrier is referred to as the envelope power Pe(t). It varies in time with the modulation frequency. The maximum envelope power is referred to as the peak envelope power or PEP. PEP is an important parameter for specifying transmitters. PEP and the envelope power can only be measured with peak or envelope power meters, which use fast diode sensors. 12 Introduction

V

0 t

AM voltage signal p PEP

Instantaneous Power Envelope Power Average Power 0 t

Figure 3 PEP and instantaneous power of Am Signal

1.9 Pulse Power power of the pulse is averaged over the pulse width τ, Pulse width τ is considered to be the time between the 50 percent rise-time and fall time amplitude points ( see Fig-4). Pulse power is defined by

τ 1 P = v(t)i(t)dt τ Z0 By definition, pulse power is averages out any aberrations in the pulse envelope such as overshoot or undershoot ringing. The definition of pulse power has been extended since the early days of mi- crowave to be: P P = avg p Duty Cycle where duty cycle is the pulse width times the repetition frequency. This extended definition, allows calculation of pulse power from an average power measurement and the duty cycle. For microwave systems which are designed for a fixed duty cycle, peak power is often calculated by use of the duty cycle calculation along with an average power sensor. One reason is that the instrumentation is less expensive, and in a technical sense, the averaging technique integrates all the pulse imperfections into the average. For microwave systems which are designed for a fixed duty cycle, peak power is often calculated by use of the duty cycle calculation along with an average power sensor. Power Sensing Method 13

PRI=1/PRF pulse width τ

Duty cycle=PRF. τ Pulse top

Power amplitude Average Power PRI

Time

Figure 4 Common Pulse Parameters

* Thermocouple * Diode power * Directional- Substituted DC Meter Coupler or AC Signal RF Sensing elements input

Figure 5 Four type of power sensing methods

1.10 Power Sensing Method Most of power sensors convert high frequency power to a DC or low frequency signal that the power meter can then measure and relate to a certain RF power level. The Four main types of sensors are thermistors, , diode detectors, and directional coupler (see Fig-5). Each power sensor has it’s benefits and limitations. We will briefly go into the theory of each type. 1.10.1 Thermocouple as a sensor of Power meter. Thermocouple sensors are based on the fact that a different metals generates a - age due to temperature differences between a hot and a cold junction. If the two metals are put together in a closed circuit, current will flow due to the difference in the . If the loop remains closed, current will flow as long as the two junc- tions remain at different . In a thermocouple, the loop is broken and a sensitive DC is inserted to measure the net thermoelectric voltage (see Fig-6). The measuring voltage can be related to a temperature change due to RF power incident upon the thermocouple element. 14 Introduction

metal-1

Hot-junction Vdc Cold junction

metal-2

Figure 6 Thermocouple principle

Since the voltage produced in a thermocouple is very low, it is possible to connect several junction in series in order to yield larger thermoelectric voltage. The two main reasons for wide using thermocouple technology are: Thermocouple ex- hibit wider dynamic range than thermistor technology, and they feature an inherent square-law detection characteristic proportional to DC . Since thermocouples, like thermistors with a self-balancing bridge, always respond to the true power of a sig- nal, they are ideal for all types of signal formats from CW to complex . Thermocouple make usable power measurements down to -30 dBm, and have lower measurement uncertainty due to a lower SWR. 1.10.2 Diode as a Sensor of Power Meter Rectifying diodes have long been used as detectors and for relative power measure- ments at microwave frequencies. Diodes convert high frequency energy to DC by using rectification properties, inherent to their non-linear current-voltage (i-v) char- acteristics. The advantage of the diode is that they can be used for measurement of extremely low powers. Refer to Fig-8 and Fig.-9 You can see that their square-law region begin from -70 to -30 dBm. Mathematically, a detection diode obeys the diode detection

qv αv I = Is(e kt 1) = Is(e 1) (1.4) q − − α = kt

where Is is the saturation current (about 10 µA), q is the electron charge , T is the absolute temperature, k is Boltzman constant. I is the diode current, v is the voltage across the diode. Equation–- may be rewrite as a series using Taylor expansion, in order to analyze the rectifing process. (αv)2 (αv)3 (αv)n I = I (αv + + + .... s 2! 3! n! for small signal operation (αv < 1) only the the first two term are significant, so the diode is said to be operating in the square law region. Mathematically it can be Power Sensing Method 15

80µΑ

60µΑ

40µΑ Current 20µΑ

Voltage(v) -0.06 -0.04 -0.02 0 0.02 0.04 0.06 Power(dBm) -21 -15 -11.5

Figure 7 Small signal I-V characteristic of diode detector

0.2

0.15

0.1

0.05 Current(A) 0 70µ v Voltage(v) 0.05 0.1 0.15 0.2 0.25 0.3

Power(dBm) -70 -13 34.867 8

Figure 8 Largel signal I-V characteristic of diode detector prooved that the approximation of square law region is valid between the noise level to about 20mv (-20dbm). In that region the output I (and output v on ), is proportional to RF input voltage squared. When αv ∼ 1, (or between -20 dBm to 0 dBm ) the other term of equation-6.4 become significant, the diode response no longer in law region, but according to quasi law region. above that range (0 to 20 dBm ) the diode moves into linear region, inthat region the output voltage is proportional to input voltage. For a typical diode, the square law region , exist from the noise level about 0.1nw (-70dBm) to 10µw (-20 dBm). the quasi square law region ranges from 10 µw to 1 mw, and linear region extend from 1 mw to 100 mw. Diodetechnologyprovidessome8000times(40dB.)more-efficient RF-to- DC conversion compared to the thermocouple previously discussed. Diode sensor technology excels in sensitivity, although thermocouple sensors maintain their one 16 Introduction

Pinc Pref

Load

Figure 9 Measuring power using directional coupler primary advantage as pure square-law detectors for the range -30 to +20 dBm. At the detecting level of 0.1 nw (-70dBm) the diode detector output is about 50 nv,such a very low signal requires special care to prevent mixing signal with noise. Today broadband detectors span frequencies from 100 kHz to 50 GHz. 1.10.3 Directional Power Sensor Directional sensors are connected between source and load, to measure the incident and reflected power. They are constructed with a dual directional coupler, with capability to separate between forward and reflected wave. The coupled signal are measured by separate RF to DC converters (Schottky diode) for the incident and for the reflected power. Fig.-12 shows a typical block diagram of directional power sensors. Some sensors can measure the peak power, the output signal of the sensors being boosted and applied to a peak hold circuit before it is transferred to the power meter. The directional coupler determines the main features of a directional power sensor, such as measurement accuracy, matching, frequency and power range. Due to rather small dimensions, line couplers with short secondary line directional couplers with lumped components or similar designs are suitable for use with directional power meters. For the frequency range up to 100 MHz, the lumped coupler mostly used. Due to the directional coupler, directional power sensors are always somewhat more narrowband than the terminating power sensors, covering a bandwidth between one octave and little more than two decades. The rated power ranges from a few W to some kW. It can relatively easily be influenced by the coupling ratio, with hardly any change to the power absorbed by the directional sensor. Reflection coefficient and insertion loss of the directional coupler are usually negligible. This holds true at least for the lower band limit, where there is only a loose coupling between main line and secondary line. Chapter 2 EXPERIMENT PROCEDURE

2.1 Required Equipment 1. HP 54603B. 2. − (SG)HP 8647A. 3. Two Arbitrary Generators− (AWG)HP 33120A. 4. Power Meter HP-E4418B. − 5. Power Sensor- HP-E4412A. 6. Double Balanced Mixer Mini-Circuit ZAD 6. 6. Diode Detector Herotek DZM124NB.. − 7. Directional Coupler Waveline 9008-20. 8. Termination-50Ω .

2.2 Turning On the Power Meter The following steps show you how to turn on the power meter and verify that it is operating correctly. 1. Connect the power cord and turn on the power meter. The front panel display and the green power LED light up when the power meter is switched on. The power meter performs it’s power on self test. 2. Set the display contrast if required. The display contrast is adjusted by pressing and . If these softkeys ↑ ª ↓ ª are not displayed press Prev repeatedly until they appear. 3. Connect a power sensor. Connect one end of the sensor cable to the power meter’s channel input and the other end to the power sensor.

2.3 Front Panel Tour Refer to Fig.-1 1. Preset -This hardkey allows you to preset the power meter if you are cur- rently working in local mode (that is, front panel operation). 2. N -This hardkey allows you to select the upper or lower measurement win- H dow on the power meter’s display. The window which is selected is highlighted by a 18 Experiment Procedure

12 11 10 9

POWER REF 1 -10 dBm 2

3

4 5 6 7 8

Figure 1 Front panel of power meter shadowed box. ¤ ¤ -This hardkey allows you to choose either a one or a two window ↔ ¤ display. 3. ∅ -This hardkey switches the power meter between on and standby. | When the power meter is switched to standby (that is, when this hardkey has not been selected but the line power is connected to the instrument) the red LED is lit. When the power meter is switched on the green LED is lit. System 4. The Input hardkey allows access to softkey menus which affect the general power meter system setup, (for example the HP-IB address) and also to softkey menus which effect the setup of the channel inputs. Save 5. Re call -This hardkey is the only one that is completely dedicated to the control of the power meter as a system. Measure Re f 6. Setup Offset dBm/w - These hardkeys allow access to same menus which affect the setup of the measurement windows. Frequency Zero 7. Cal Fac , Cal - These hardkeys allow access to softkey menus which affect the measurement channel. 8. Channel Input- The HP E4418B has one sensor input. 9. POWER REF Output- The power reference output is a 50Ω type N con- nector. The output signal sinewave of 1 mW at 50 MHz is used for calibrating the sensor and meter combination. 10. = = -Arrow hardkeys allow you to move the position of the cursor, use select⇑ ⇓ fi⇐elds for⇒ editing, and edit alphanumeric characters. 11. More -Menu related hardkeys this hardkey allows you to move through all pages of a menu. The bottom right of the power meter display indicates the number of pages in the menu. For example, if ”1 of 2” is displayed, pressing More moves you to ”2 of 2”. Pressing More again moves you back to ”1 of 2”. Prev This hardkey allows you to move back one level in the softkey menu. Power Meter Operation 19

-10 dBm POWER REF

Figure 2 Zeroing and Calibrating Power Meter

Repeatedly pressing Prev accesses a menu which allows you to increase and decrease the display contrast. 12. Softkeys- These four keys are used to make a selection from the menus.

2.4 Power Meter Operation 2.4.1 Zeroing the Power Meter Zeroing adjusts the power meter for a zero power reading with no power applied to the power sensor. During zeroing, which takes approximately 10 seconds, the wait symbol is displayed. To zero the power meter: Zeroing of the power meter is recommended: *whena5◦C change in temperature occurs since the last calibration. * when you change the power sensor. * every 24 hours. * prior to measuring low level signals. For example, 10 dB above the lowest specified power for your power 1. Connect the power sensor to the POWER REF output as indicated in Fig-2. Zero 1. Press cal , Zero . During zeroing the wait symbol is displayed. 2.4.2 Calibrating the Power Meter Calibration sets the of the power meter using a 50 MHz 1 mW calibrator as a traceable power reference. The power meter’s POWER REF output is used as the signal source for calibration. An essential part of calibrating is setting the correct reference calibration factor for the power sensor you are using. The HP E-4412A power sensors set the reference calibration factor automatically. During calibration the wait symbol is displayed. The power meter identify that an HP E-series power sensor is connected and will not allow you to select certain softkeys. The text on these softkeys appears grayed out. Note During calibration the power meter automatically switches the power reference calibrator on (if it is not already on), then after calibration it switches it to the state it was in prior to the calibration. 1. Verify that the system is connected as indicated In Fig.-2 20 Experiment Procedure

15.000,000 MHz R I Oscilloscope 54600A

HP-33120A L 15.000,000 MHz

Figure 3 Average power of sinusoidal signa

Zero 2. Press Cal 3. Press: cal to calibrate the power meter. During calibration the wait symbol is displayed. (The power meter automatically turns on the POWER REF output.)

2.5 Average Power In this part of the experiment, we use two sinusoidal to represent the voltage and the current respectively. The Double Balanced Mixer used as a multiplier with losses, which multiply the voltage and the current respectively. The oscilloscope used as the display of the power meter. 1. Refer to appendix-1, connect the system according to appendix, and set the phase between the two generators to zero degree. 2. Connect the System according to Fig.- 3. 3. Adjust the T&M equipment as follows: LO AW G- Frequency 1 kHz amplitude 100 mv. − RF AW G- Frequency 1 kHz amplitude 100 mv. − 4. Measure the two signals according to table-1, and save the data on magnetic media. Frequency Vp p Vave power − . Voltage Table-1 Why is Vave of the voltage signal significantly smaller than the Vave of the power signal? 5. Set the phase between the two generators to +90◦,describe what happens to the power signal, and what is the meaning of these changes? 6.Setthephasebetweenthetwogeneratorsto-90◦ describe what happens to the power signal generators to -90◦ what is the difference +90◦ and -90◦?Setthe phase between the two generators to +90◦,-90◦,andsavethe data on magnetic media Power of a Modulated Sinusoidal Signal 21

15.000,000 MHz R I Oscilloscope 54600A

HP-33120A L 15.000,000 MHz

Figure 4 Power of AM modulated signal for each phase difference.

2.6 Power of a Modulated Sinusoidal Signal In this part of the experiment, we multiply two identical AM signal sources, in order to simulate three types of power (average power, peak power, peak envelope peak) used in measuring modulated sinusoidal signals . 1. Connect the System according to Fig. -4. 2. Set the frequency of the two AWG’s to 20 kHz,and set the phase to 0◦ between them. 3. Adjust the T&M equipment as follow: LO AW G- Frequency 20 kHz amplitude 400 mv , AM modulation, modulated frequency 1− kHz, AM depth 70%. RF AW G- Frequency 20 kHz amplitude 100 mv , AM modulation, modu- lated frequency− 1 kHz, AM depth 70%. 4. Adjust the oscilloscope in order to get a stable signal like Fig-3 (theory chapter), and save the data on magnetic media.

2.7 Pulse Power In this part of the experiment, we measure the major parameter of a pulse, generated byasquarewavesignalwithoffset and duty cycle. 1. Connect the System according to Fig.-5 . 2.AdjusttheAWGto:Squarewave,Frequency1MHz,amplitude100mv ,offset 50 mv,duty cycle 20%. 3. Using the oscilloscope feature measure a. Zero to peak power, (without the over and under shoot of the pulse), b. Pulse width, c. Pulse Repetition Interval (PRI). d. Average power. 22 Experiment Procedure

Oscilloscope 54600A 15.000,000 MHz

HP-33120A

Figure 5 Power of pulse signal

Digital 515.000,00 MHz 10.000,00 V DC

Diode HP-34401A Detector Signal generator HP-8647A

Figure 6 Measuring power using diode detector

e. Pulse Repetition Frequency (PRF).

f. Duty cycle of the pulse

save the Pulse on magnetic media.

2.8 Diode Detector

In the first part of the experiment you will sketch the characteristic curve voltage as a function of input power. In the second part you will measure the power of an ’unknown’ source .

1. Connect the diode detector to the signal generator as indicated in Fig.-6.

2. Set the signal generator to 500 MHz, amplitude according to table-2, mea- sure the output voltage and fill in the table. Final Report 23

P(dBm) Diode Voltage P(dBm) Diode Voltage -50 -15 -45 -10 -40 -7 -35 -5 -30 0 -25 3 -20 5 -17 10 Table-2

2.9 Final Report

1. Using the data of average and instantaneous power , draw three graphs of average power for 0◦,90◦,-90◦, ( answer the relevant questions in this pharagraph). 2. Using the data of Power of a Modulated Sinusoidal Signal draw a graph like figure-3(theory part), but based on measured data. a. Using Matlab or other software, draw a graph of 20 kHz AM- signal, modulated by 1 kHz, AM depth of 70%. (See instantaneous power Fig.-3 theory part). b. A graph of calculated average power (Pave). c. A graph of calculated envelope power Pe(t) (based on average of every cycle of instantaneous power). d. Find the PEP from the above calculation. 3. Referring to your data of pulse measurement , draw a graph of a. Pulse power b. Average power of the pulse(calculated). From the data find peak power, PRF, duty cycle of the pulse. 4. Use the data of table-2, draw a graph of the diode (Vin (calculated) as a function of output voltage). Using regression function (with statistical software or worksheet ) find the best equation of the curve. According to the graphs find the range where the output voltage of the diode is approximately proportional to the input power, and the range that the output voltage is proportional to input voltage.

2.10 Appendix-1 2.10.1 To phase lock two . 1. Connect rear- panel Ref Out 10MHz output terminal of the master Arbitrary Waveform Generator HP-33120A to Ref in on the rear panel of the slave HP-33120A as indicated in Fig-9. 2. Connect the two AWG’s to the oscilloscope as shown in figure-9 3. Set the oscilloscope to XY function, in order to measure phase difference. 24 Experiment Procedure

Ref Out Ext Ref in Ref Out Ext Ref in

Rear panel connection.

15.000,000 MHz Oscilloscope Oscilloscope 54600A display

HP-33120A

15.000,000 MHz

Figure 7 Setting zero phase using Lissajous method

4. Turn on the menu of the AWG by pressing shift Menu On/Off the display then looks like A: MOD MENU . 5. Move across to G: PHASE MENU by pressing the < button. 6. Move down one level to the ADJUST command, by pressing , the display looks like 1: ADJUST ∨ 5. Press one level and set the phase offset, Change the phase continuously ∨ between the two AWG’s until you get straight line, incline at 45◦ to the X axis (zero phase). you see then a display like 120.000DEG . 6. Turn off the menu by pressing∧ ENTER .You have then exited the menu. 2.10.2 Setting a zero phase reference at the end of the cable. 1. Turn on the menu by pressing shift Menu On/Off the display looks like A: MOD MENU . 2. Move across to the PHASE MENU choice on this level, by pressing <,the display looks like G: PHASE MENU 3. Move down one level and then across to the SET ZERO by pressing and > bottoms, the display show the message 2: SET ZERO . ∨ 4. Move down a level to set the zero phase reference, by pressing the displayed message indicates PHASE = 0 . ∨ 5. Press Enter , save the phase reference and turn off the menu. Important Appendix-1 25

1. At this point, the function generator HP-33120A is phase locked to another HP-33120A or external clock signal with the specified phase relationship. The two signals remain locked unless you change the output frequency.